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When the next-generation Mars rover, dubbed Curiosity, touches down on martian soil next summer, its cameras will likely capture a scene similar to what the first explorers of the Grand Canyon witnessed: towering layers of rock and sediment rising up from a dusty valley.
On Friday, NASA officials announced that Curiosity will land in a region named Gale Crater, a large depression with a massive, finely stratified mountain at its center. For two years, the rover will explore and sample sediments from the crater's valleys and cliffs, seeking signs of habitability.
Maria Zuber, the Earle A. Griswold Professor of Geophysics and Planetary Science and head of MIT's Department of Earth, Atmospheric and Planetary Sciences, says Gale Crater may reveal clues about Mars' past. She spoke with MIT News about a future in which humans might explore the Red Planet.
Q. What makes Gale Crater an ideal landing site?
A. Gale is a large, ancient crater — about 154 kilometers [96 miles] in diameter — in the equatorial region of Mars that formed somewhere in the range of 3.5 to 3.8 billion years ago. At the center of the crater is a five-kilometer-high [16,400-foot] mountain that contains hundreds of fine layers and grades in composition from the bottom up. Such a sequence of rocks, called a stratigraphic section, is a treasure trove of information for geologists. It preserves a temporal record, in which you're essentially looking back in time as you progress down the column.
Gale's mountain is the remnant of sediments that once filled the crater and were subsequently eroded. At the base of this mountain are clays, which form in water-rich conditions at elevated temperatures possibly associated with impact or hydrothermal conditions. The geologic context of the clay minerals will hopefully allow the origin to be distinguished. Further up the column the mineralogy transitions to reveal sulfate-rich rocks. The crystallization of sulfates also requires a substantial quantity of water, and some sulfates recognized on Mars require acidic conditions to form. This sequence implies a change in the aqueous chemistry of early Mars, conceivably indicating a significant change in environmental conditions.
The Curiosity rover will be able to ascend at least the lower layers of the central mountain, systematically studying the chemistry and geology and providing information that scientists will use to reconstruct just how the environment changed.
Q. What would this area have looked like during an age when there might have been water, and possibly life, on the planet?
A. Gale has had a complex history but it seems certain that water played a role in shaping the crater. There may have been a large amount of water on the floor, and water may have played a role in depositing the sediments that compose the central mountain. Several channels, likely carved by flowing water, cut the mountain, underscoring that water was present in multiple episodes of the crater's history.
Q. One of the goals of the Curiosity mission is to "prepare for human exploration." What does this mean, and how will the rover tackle this objective?
A. This mission will demonstrate the ability to deliver a large and heavy spacecraft to the surface of Mars. That's a step … that needs to be taken if you want to eventually send a human there: When humans go to Mars, the landed mass will be significant. The Curiosity lander is about as heavy as a small car and more than 300 kilograms heavier than the Mars exploration rovers; to deliver such a massive robotic explorer to the surface of Mars is real progress.
The precision landing system to set the rover on the martian surface, called "Sky Crane," is genuinely new, and increases the flexibility in selecting landing sites. When we used to evaluate landing sites on Mars, the engineers would always want to land at low elevation, with a lot of atmosphere above it — for parachuting in — and somewhere flat with no large rocks that would cause the rover to tip over or limit mobility. And the scientists would always want to go to the rocky, hazardous, mountainous places because those are the most interesting geologically. Because this landing system is so robust, Curiosity can land in many places on Mars that would not have been possible in the past. The fact that a site may be rocky, or have a mountain or cliff nearby, need no longer necessarily be a showstopper.
This guided entry and the ability to do precision landing is extremely helpful for future human exploration, because humans will want to land in the best, safest place on Mars. | 0.864376 | 3.952413 |
New research asks a big question: Is there such a thing as a sustainable civilization, perhaps one that lies far beyond our own galaxy? Or are all civilizations doomed to destroy themselves?
“If we’re not the universe’s first civilization, that means there are likely to be rules for how the fate of a young civilization like our own progresses.”
In the face of climate change, deforestation, and biodiversity loss, creating a sustainable version of civilization is one of humanity’s most urgent tasks. But when confronting this immense challenge, we rarely ask what may be the most pressing question of all: How do we know if sustainability is even possible?
Astronomers have inventoried a sizable share of the universe’s stars, galaxies, comets, and black holes. But are planets with sustainable civilizations also something the universe contains? Or does every civilization that may have arisen in the cosmos last only a few centuries before it falls to the climate change it triggers?
Astrophysicist Adam Frank, a professor of physics and astronomy at the University of Rochester, is part of a group of researchers who have taken the first steps to answer these questions. In a new study in the journal Astrobiology, the group addresses these questions from an “astrobiological” perspective.
“Astrobiology is the study of life and its possibilities in a planetary context,” says Frank, who is also author of the new book Light of the Stars: Alien Worlds and the Fate of the Earth (W.W. Norton, 2018), which draws on this study. “That includes ‘exo-civilizations’ or what we usually call aliens.”
Frank and his colleagues point out that discussions about climate change rarely take place in this broader context—one that considers the probability that this is not the first time in cosmic history that a planet and its biosphere have evolved into something like what we’ve created on Earth.
“If we’re not the universe’s first civilization,” Frank says, “that means there are likely to be rules for how the fate of a young civilization like our own progresses.”
As a civilization’s population grows, it uses more and more of its planet’s resources. By consuming the planet’s resources, the civilization changes the planet’s conditions. In short, civilizations and planets don’t evolve separately from one another; they evolve interdependently, and the fate of our own civilization depends on how we use Earth’s resources.
In order to illustrate how civilization-planet systems co-evolve, Frank and his collaborators developed a mathematical model to show ways in which a technologically advanced population and its planet might develop together. By thinking of civilizations and planets—even alien ones—as a whole, researchers can better predict what might be required for the human project of civilization to survive.
“The point is to recognize that driving climate change may be something generic,” Frank says. “The laws of physics demand that any young population, building an energy-intensive civilization like ours, is going to have feedback on its planet. Seeing climate change in this cosmic context may give us better insight into what’s happening to us now and how to deal with it.”
Using their mathematical model, the researchers found four potential scenarios that might occur in a civilization-planet system:
- Die-off: The population and the planet’s state (indicated by something like its average temperature) rise very quickly. Eventually, the population peaks and then declines rapidly as the rising planetary temperature makes conditions harder to survive. A steady population level is achieved, but it’s only a fraction of the peak population. “Imagine if 7 out of 10 people you knew died quickly,” Frank says. “It’s not clear a complex technological civilization could survive that kind of change.”
- Sustainability: The population and the temperature rise but eventually both come to steady values without any catastrophic effects. This scenario occurs in the models when the population recognizes it is having a negative effect on the planet and switches from using high-impact resources, such as oil, to low-impact resources, such as solar energy.
- Collapse without resource change: The population and temperature both rise rapidly until the population reaches a peak and drops precipitously. In these models civilization collapses, though it is not clear if the species itself completely dies outs.
- Collapse with resource change: The population and the temperature rise, but the population recognizes it is causing a problem and switches from high-impact resources to low-impact resources. Things appear to level off for a while, but the response turns out to have come too late, and the population collapses anyway.
“The last scenario is the most frightening,” Frank says. “Even if you did the right thing, if you waited too long, you could still have your population collapse.”
Looking at Easter Island
The researchers created their models based in part on case studies of extinct civilizations, such as the inhabitants of Easter Island. People began colonizing the island between 400 and 700 CE and grew to a peak population of 10,000 sometime between 1200 and 1500 CE. By the 18th century, however, the inhabitants had depleted their resources and the population dropped drastically to about 2,000 people.
The Easter Island population die-off relates to a concept called carrying capacity, or the maximum number of species an environment can support. The Earth’s response to civilization building is what climate change is really all about, Frank says.
“If you go through really strong climate change, then your carrying capacity may drop, because, for example, large-scale agriculture might be strongly disrupted. Imagine if climate change caused rain to stop falling in the Midwest. We wouldn’t be able to grow food, and our population would diminish.”
Right now researchers can’t definitively predict the fate of the Earth. The next steps will be to use more detailed models of the ways planets might behave when a civilization consumes energy of any form to grow. In the meantime, Frank issues a sober warning.
“If you change the Earth’s climate enough, you might not be able to change it back,” he says. “Even if you backed off and started to use solar or other less impactful resources, it could be too late, because the planet has already been changing. These models show we can’t just think about a population evolving on its own. We have to think about our planets and civilizations co-evolving.”
Source: University of Rochester | 0.858216 | 3.195475 |
Future human settlers looking to create a permanent residence on Mars could conceivably use Martian-mixed concrete for construction purposes, researchers at Northwestern University, Illinois say.
With SpaceX successfully landing a rocket stage, and the Curiosity rover frequently delivering tidbits of information concerning the realities of the Red Planet, the notion of life on Mars—as in humans heading there to live—seems more and more tangible. Add in a Golden Globe win by Matt Damon, and heck it seems like we’re practically ready to hang our collective hats over there (as in approximately 235 million miles away).
But the fact is, if we are going to set up shop upon our dusty planetary neighbor, we’ll need to be practical—and there are researchers working on ways to make our stay a possibility—like Northwestern University’s Center for Sustainable Engineering of Geological and Infrastructure Materials (SEGIM), who have devised ways for earthlings on Mars to concoct viable building material.
A group from SEGIM recently published a piece (titled A Novel Material for In Situ Construction on Mars: Experiments and Numerical Simulations) that lays the foundation for possibly establishing foundations on Mars with resources taken from Martian soil. “A significant step in space exploration during the 21st century will be human settlement on Mars,” the write-up opens, “Instead of transporting all the construction materials from Earth to the red planet with incredibly high cost, using Martian soil to construct a site on Mars is a superior choice.”
As it turns out, Mars is just lousy with sulfur. The element has a long history of human use for building purposes, and as the SEGIM team reports, “Both the atmospheric pressure and temperature range on Mars are adequate for hosting sulfur concrete structures.” To those among us not well-versed in the mixing of concrete, it turns out that not every environment in the Solar System would allow for its creation—not even our moon, where “the low temperature (it can dip as low as -243 degrees Fahrenheit)…is too harsh to maintain intact the mechanical properties of sulfur concrete.” On the other hand, the average temp on Mars (-81 degrees Fahrenheit) is apparently quite suitable.
The SEGIM formula for MC (“Martian Concrete”) would roughly be a mix of 50-percent Martian sulfur and 50-percent Martian soil—and the mix also has the added bonus of being recyclable.
“In recent years,” the Northwestern U team reports, “many countries, including the U.S., China, and Russia, announced to launch manned Mars missions in the next decades. Due to the dry environment on Mars, sulfur concrete concept is a superior choice for building a human village on the red planet.”
There is, however, no mention of how to keep future human visitors from carving, “Earth wuz here” in any future freshly-laid Martian sidewalks. | 0.830061 | 3.166194 |
Southern aurora (aurora australis) composited with NASA imagery As we're in the midst of experiencing some particularly stormy solar weather it seems appropriate to make a quick post with some nifty auroral images and time-lapse movies (see below)...
The planet Upsilon Andromedae b in close orbit to its parent star (NASA/JPL-Caltech) Understanding the structure, dynamics, and chemistry of planetary atmospheres is key to exoplanetary science...
Earth-sized planets near and far (NASA/Ames/JPL-Caltech) Planets in habitable zones, planets orbiting twin suns, miniature solar systems, rogue planets, planets, planets, planets.
A black hole lenses the light of the Milky Way in the background (Credit: Ute Kraus amd Axel Mellinger) This weekend Stephen Hawking turns 70, an extraordinary physical accomplishment to add to an extraordinary list of physics accomplishments...
In the northern winter months we are surrounded by the stark beauty of chilled landscapes. From the darkness of the far north, broken perhaps only by starlight and the glow of aurora, to the brisk grey streets of Manhattan and its now skeletal trees with their claw-like limbs and knobbly stubs pressed to the skies, [...]..
The Sun rising above the Arctic plain (H. D. Nygren, NOAA Corps.) As our spinning globe of rock and metal tracks its steady path around the Sun, we find ourselves crossing once again through the winter solstice, the point at which Earth's northern pole is pointed as far from our fierce stellar parent as it can be (this year at a coordinated universal time of 5.30 am on December the 22nd, almost the same as 5.30 am Greenwich Mean Time)...
A strange chemical reaction Imagine, if you will, a planet with atmosphere, oceans, rocks and life. On this planet, most chemical reactions are either slow and geophysical, or quick and biological but very localized...
Warning: Exoplanets may appear less massive than they really are (images used: Eysteinn Guðni Guðnason and NASA/Kepler) Exoplanets can be confusing things.
Comparison of "habitable zone" of Kepler 22 system and our solar system (NASA/Kepler) Today sees the announcement that one of the "candidate" planets listed from NASA's Kepler mission back in February is now confirmed, and it's a key one...
What lies beneath such turbulent skies? (NASA/JPL) Gas giant planets are among the most beautiful and awe-inspiring worlds. In our own solar system we've long gazed at Jupiter's extraordinary swirling atmosphere, where stormy circulations like the Great Red Spot persist for centuries...
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Scientists have produced a new version of what is perhaps NASA's best view of Jupiter's ice-covered moon, Europa. The mosaic of color images was obtained in the late 1990s by NASA's Galileo spacecraft. This is the first time that NASA is publishing a version of the scene produced using modern image processing techniques.
The image is available at:
This view of Europa stands out as the color view that shows the largest portion of the moon's surface at the highest resolution.
An earlier, lower-resolution version of the view, published in 2001, featured colors that had been strongly enhanced. The new image more closely approximates what the human eye would see. Space imaging enthusiasts have produced their own versions of the view using the publicly available data, but NASA has not previously issued its own rendition using near-natural color.
The image features many long, curving and linear fractures in the moon's bright ice shell. Scientists are eager to learn if the reddish-brown fractures, and other markings spattered across the surface, contain clues about the geological history of Europa and the chemistry of the global ocean that is thought to exist beneath the ice.
In addition to the newly processed image, a new video details why this likely ocean world is a high priority for future exploration.
The video is available at:
Hidden beneath Europa's icy surface is perhaps the most promising place in our solar system beyond Earth to look for present-day environments that are suitable for life. The Galileo mission found strong evidence that a subsurface ocean of salty water is in contact with a rocky seafloor. The cycling of material between the ocean and ice shell could potentially provide sources of chemical energy that could sustain simple life forms.
The Galileo mission was managed by NASA's Jet Propulsion Laboratory in Pasadena, California, for the agency's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology, Pasadena.
More information about Europa is available at:
News Media ContactPreston Dyches
Jet Propulsion Laboratory, Pasadena, Calif. | 0.817599 | 3.019679 |
From the hottest deserts to the iciest mountains (like the slopes of Mount Rainier, above), the world is a many-splendored place. But some spots are one-of-a-kind, with sights that can't be seen anywhere else on the planet. Here, we list some of these amazing places. Let's go exploring.
Where the Clouds Roll By
A rare tubular cloud formation occurs with regularity only one place on Earth: Northern Australia’s Gulf of Carpentaria. Here, ultra-long "roll clouds" form regularly in fall months. The phenomenon even has its own, geographically specific name, the Morning Glory cloud. Elsewhere in the world, roll clouds pop up only very occasionally, usually associated with sea winds or sometimes thunderstorm downdrafts. [See more images of curious clouds]
Where the Snow Is Like Knives
These sharp snow formations make the white stuff look uninviting. They’re called penitentes, and although they can form at high altitudes anywhere, there’s no place better to see them than in the Dry Andes of Chile and Argentina, way up past 13,000 feet (about 4,000 meters).
Penitentes, named after pointy hats worn by people doing penance for their sins in Christian traditions, form in very cold, dry air, where the water in snow sublimates, or turns directly into vapor without melting first. Sublimation randomly occurs faster in some areas than in others; once uneven pock-marks form in the snow, they focus the sunlight, causing those areas to sublimate ever faster. Spiky penitentes get left behind, unmelted. The tallest penitentes can reach 12 feet (4 meters) high.
Where the Lakes Explode
To see a lake that can kill you without you even dipping in a toe, visit Africa. In Cameroon and on the border of Rwanda and the Democratic Republic of the Congo are three deadly lakes: Nyos, Monoun and Kivu. All three are crater lakes that sit above volcanic earth. Magma below the surface releases carbon dioxide into the lakes, resulting in a deep, carbon dioxide-rich layer right above the lakebed.
In 1984, Lake Monoun abruptly exploded, releasing waves of water and a cloud of carbon dioxide. Thirty-seven people who lived near the lake asphyxiated in the CO2 cloud, though the cause of their deaths remained a mystery until two years later, when Lake Nyos let out its own burst of carbon dioxide. This time, 1,700 people died when the carbon dioxide, which is heavier than oxygen, displaced the breathable air in their villages.
Venting pipes have been installed in Lake Nyos and Lake Monoun in an attempt to release the carbon dioxide gas slowly and prevent future disasters. Kivu, which has never erupted, is not being vented, although local companies do extract dissolved methane from the lake to use for power generation.
Where Tsunamis Sweep Mountains
In landlocked Bhutan, tsunamis are becoming a danger. Climate change is melting Himalayan glaciers, increasing the risk that glacial melt will break through ice dams and wipe out villages. Scientists call these flash floods, one of which killed dozens in 1994, "glacial-lake-outburst floods," but in layman's terms, they're mountain tsunamis.
Bhutan is working to ease the danger by draining some high glacial lakes and shoring up their natural dams. Glacial lake outbursts can happen anywhere where glaciers are melting, but according to Bhutan's government and the United Nations, 24 of the country's 2,674 glacial lakes are at risk, making Bhutan the epicenter of this phenomenon. [Ice World: Gallery of Awe-Inspiring Glaciers]
Where the Rocks Walk
At Racetrack Playa in Death Valley, it’s not horses or stock cars that make the rounds — it’s rocks. This pancake-flat dry lakebed is marked by tracks of large rocks that seem to have wandered from here to there under their own power.
In fact, the rocks (some of which weigh tens or hundreds of pounds) may require a perfect storm to get moving. According to lunar and planetary sciences researchers at NASA Goddard, wind pushes the rocks around. But for the wind to move huge boulders, there has to be little friction between the rock and the ground. Most likely, ice-encrusted rocks get inundated by meltwater from the hills above the playa, according to NASA researchers. When everything’s nice and slick, a stiff breeze kicks up, and whoosh, the rock is off.
Where Crystals Dwarf Humans
Imagine an underground world where shimmering crystals crisscross caverns like a giant’s Tinkertoys. Mexico's Cave of Crystals, buried below the Chihuahuan desert, is just that. Here, enormous crystals of selenite grow more than 30 feet (10 meters) long.
But this fantasy world is tough to withstand. The cave is nearly 1,000 feet (300 meters) below the surface, and a magma chamber below keeps the caverns heated to about 136 degrees Fahrenheit (58 degrees Celsius), with 99 percent humidity. Explorers must wear protective gear if they hope to survive in this crystal cave for more than a few minutes. [Amazing Caves: Pictures of the Earth's Innards]
Where Lightning Strikes Way More Than Twice
Clear skies rarely prevail at the mouth of the Catatumbo River in Venezuela. Here, it storms on average every other night, as moist, warm winds meet the nearby ridges of the Andes and explode into electrifying tempests. The lightning is so consistent that sailors have been known to navigate by its glow, which even reportedly saved the city of Maracaibo from attack by the English pirate Sir Francis Drake in 1595. According to a 1597 poem, the lightning illuminated Drake’s fleet, alerting the city to the pirate's presence.
Where the Coral Grows Like Mushrooms
The only place to find this strange structure is along the northeastern coast of Brazil, in and around Abrolhos Marine National Park. This is the only spot on Earth to see chapeiroes, isolated coral columns that grow on the seafloor and have a mushroomlike structure. Chapeiroes come in different shapes and sizes, but the giant and mature chapeiroes of the Abrolhos Bank can reach more than 65 feet (20 meters) tall and 165 feet (50 meters) in diameter at their tops. According to Conservation International, an environmental group that works in the region, climate change threatens these unique reefs, so researchers are working to understand how the coral responds to changing conditions.
Where Tectonic Plates Meet
Deep in the ocean, underwater mountains form as tectonic plates spread apart, with the boundary between these spreading plates forming a mid-ocean ridge as molten rock from below rises up to fill in the gap. To see a mid-ocean ridge with your own eyes, though, travel to Iceland, the only place where the mid-Atlantic ridge runs on land. This geologically active spot, also known as the Reykjanes Ridge, marks a rather fuzzy boundary between the North American and Eurasian tectonic plates. Because of unusually active volcanism at the ridge below Iceland, the area is like a blister on the top of this gash, oozing (and sometimes erupting) lava to the surface, which hardens into new crust.
Where the Life Is Very Old
To get a sense of how life on Earth used to be, visit Shark Bay, Australia, one of the very few places on the planet where you can see living stromatolites. These structures are rounded towers of sediment built over thousands of years by cyanobacteria, or blue-green algae. The stromatolites at Shark Bay are a few thousand years old, but they’re nearly identical to the life that thrived on Earth 3.5 billion years ago, when oxygen made up just 1 percent of the atmosphere. Though they’re found in a few extra-salty bodies of water around the world, stromatolites are at their most diverse and most abundant at Shark Bay. | 0.820659 | 3.043511 |
In recent years, the idea of life on other planets has become less far-fetched. NASA announced June 27 that it will send a vehicle to Saturn’s icy moon Titan , a celestial body known to harbor surface lakes of methane and an ice-covered ocean of water, boosting its chance for supporting life.
On Earth, scientists are studying the most extreme environments to learn how life might exist under completely different settings, like on other planets. A University of Washington team has been studying the microbes found in " cryopegs ,” trapped layers of sediment with water so salty that it remains liquid at below-freezing temperatures, which may be similar to environments on Mars or other planetary bodies farther from the sun.
At the recent AbSciCon meeting in Bellevue, Washington, researchers presented DNA sequencing and related results to show that brine samples from an Alaskan cryopeg isolated for tens of thousands of years contain thriving bacterial communities. The lifeforms are similar to those found in floating sea ice and in saltwater that flows from glaciers, but display some unique patterns.
"We study really old seawater trapped inside of permafrost for up to 50,000 years, to see how those bacterial communities have evolved over time,” said lead author Zachary Cooper , a UW doctoral student in oceanography.
Cryopegs were first discovered by geologists in Northern Alaska decades ago. This field site in Utqia’vik, formerly known as Barrow, was excavated in the 1960s by the U.S. Army’s Cold Regions Research and Engineering Laboratory to explore large wedges of freshwater ice that occur in the permafrost there. Subsurface brine was eventually collected from the site in the 2000s.
"The extreme conditions here are not just the below-zero temperatures, but also the very high salt concentrations,” said Jody Deming , a UW professor of oceanography who studies microbial life in the Arctic Ocean. "One hundred and forty parts per thousand - 14% - is a lot of salt. In canned goods that would stop microbes from doing anything. So there can be a preconceived notion that very high salt should not enable active life.”
It’s not fully known how cryopegs form. Scientists believe the layers might be former coastal lagoons stranded during the last ice age, when rain turned to snow and the ocean receded. Moisture evaporated from the abandoned seabed was then covered by permafrost, so the remaining briny water became trapped below a layer of frozen soil.
To access the subsurface liquids, researchers climb about 12 feet down a ladder and then move carefully along a tunnel within the ice. The opening is just a single person wide and is not high enough to stand in, so researchers must crouch and work together to drill during the 4- to 8-hour shifts.
Deming describes it as "exhilarating” because of the possibility for discovery.
Samples collected in the spring of 2017 and 2018, geologically isolated for what researchers believe to be roughly 50,000 years, contain genes from healthy communities of bacteria along with their viruses.
"We’re just discovering that there’s a very robust microbial community, coevolving with viruses, in these ancient buried brines,” Cooper said. "We were quite startled at how dense the bacterial communities are.”
The extreme environments on Earth may be similar to the oceans and ice of other planets, scientist believe.
"The dominant bacterium is Marinobacter,” Deming said. "The name alone tells us that it came from the ocean - even though it has been in the dark, buried in frozen permafrost for a very long time, it originally came from the marine environment.”
Mars harbored an ocean of water in the past, and our solar system contains at least a half-dozen oceans on other planets and icy moons. Titan, the moon of Saturn that NASA will explore, is rich in various forms of ice. Studying life on Earth in frozen settings that may have similarities can prepare explorers for what kind of life to expect, and how to detect it.
Other collaborators at UW are Josephine Rapp , a postdoctoral researcher in Oceanography, Max Showalter, a doctoral student in Oceanography, and Shelly Carpenter , a research scientist in Oceanography. | 0.85414 | 3.783765 |
NASA’s two small MarCO CubeSats will be flying past Mars in 2016 just as NASA’s next Mars lander, InSight, is descending to land on the surface. MarCO, for Mars Cube One, will provide an experimental communications relay to inform Earth quickly about the landing. Credits: NASA/JPL-Caltech
See fly by and cubesat spacecraft graphics and photos below[/caption]
CubeSats are taking the next great leap for science – departing Earth and heading soon for the fourth rock from the Sun.
For the first time, two tiny CubeSat probes will launch into deep space in early 2016 on their first interplanetary expedition – aiming for the Red Planet as part of an experimental technology relay demonstration project aiding NASA’s next Mission to Mars; the InSight lander.
NASA announced the pair of briefcase-sized CubeSats, called Mars Cube One or MarCO, as a late and new addition to the InSight mission, that could substantially enhance communications options on future Mars missions. They were designed and built by NASA’s Jet Propulsion Laboratory (JPL), Pasadena, California.
InSight, which stands for Interior Exploration Using Seismic Investigations, Geodesy and Heat Transport, is a stationary lander. It will join NASA’s surface science exploration fleet currently comprising of the Curiosity and Opportunity missions which by contrast are mobile rovers.
InSight is the first mission to understand the interior structure of the Red Planet. Its purpose is to elucidate the nature of the Martian core, measure heat flow and sense for “Marsquakes.”
Because of their small size – roughly 4 inches (10 centimeters) square) – and simplicity using off-the-shelf components, they are a favored platform for university students and others seeking low cost access to space – such as the Planetary Society’s recently successful Light Sail solar sailing cubesat demonstration launched in May. Six units are combined together to create MarCO.
Over the past few years many hundreds of cubesats have already been deployed in Earth orbit – including many dozens from the International Space Station (ISS) – but these will be the first going far beyond our Home Planet.
Data relayed by MarCO at 8 kbps in real time could reveal InSight’s fate on the Martian surface within minutes to mission controllers back on Earth, rather than waiting for a potentially prolonged period of agonizing nail-biting lasting an hour or more.
The two probes, known as MarCO-A and MarCO-B, will operate during InSight’s highly complex entry, descent and landing (EDL) operations as it descends through the thin Martian atmosphere. Their function is merely to quickly relay landing data. But the cubesats will have no impact on the ultimate success of the mission. They will intentionally sail by but not land on Mars.
“MarCO is an experimental capability that has been added to the InSight mission, but is not needed for mission success,” said Jim Green, director of NASA’s planetary science division at the agency’s headquarters in Washington, in a statement.
The MarCO Cubesats will serve as a test bed for a revolutionary communications mode that seeks to quickly relay data back to Earth about the status of InSight – in real time – as it plummets down to the Red Planet for the “Seven Minutes of Terror” that hopefully climaxes with a soft landing.
The MarCO duo will fly by past Mars at a planned distance and altitude of about 3,500 kilometers as InSight descends towards the surface during EDL operations. They will rapidly retransmit signals coming from the lander in real time, directly back to NASA’s huge Deep Space Network (DSN) receiving dish antennas back on Earth.
For this flight, six cubesats will be joined together to provide the additional capability required for the journey to Mars and to accomplish their communications task.
The six-unit MarCO CubeSat has a stowed size of about 14.4 inches (36.6 centimeters) by 9.5 inches (24.3 centimeters) by 4.6 inches (11.8 centimeters) and weighs 14 kilograms.
The solar powered probes will be outfitted with UHF and X-band communications gear as well as propulsion, guidance and more.
The overall cost to design, build, launch and operate MarCO-A and MarCO-B is approximately $13 million, a NASA spokesperson told Universe Today.
InSight and MarCO are slated to blastoff together on March 4, 2016 atop a United Launch Alliance Atlas V rocket from Vandenberg Air Force Base, California.
After launch, both MarCO CubeSats will separate from the Atlas V booster and travel along their own trajectories to the Red Planet.
“MarCO will fly independently to Mars,” says Green.
They will be navigated independently from InSight. They will all reach Mars at approximately the same time for InSight’s landing slated for Sept. 28, 2016.
MarCO’s two solar panels and two radio antennas will unfurl after being released from the Atlas booster. The high-gain, X-band antenna is a flat panel engineered to direct radio waves the way a parabolic dish antenna does,” according to a NASA description.
The softball-size radio “provides both UHF (receive only) and X-band (receive and transmit) functions capable of immediately relaying information received over UHF.”
During EDL, InSight will transmit landing data via UHF radio to the MarCO cubesats sailing past Mars as well as to NASA’s Mars Reconnaissance Orbiter (MRO) soaring overhead.
MarCO will assist InSight by receiving the lander information transmitted in the UHF radio band and then immediately forward EDL information to Earth using the X-band radio. By contrast, MRO cannot simultaneously receive information over one band while transmitting on another, thus delaying confirmation of a successful landing possibly by an hour or more.
“Ultimately, if the MarCO demonstration mission succeeds, it could allow for a “bring-your-own” communications relay option for use by future Mars missions in the critical few minutes between Martian atmospheric entry and touchdown,” say NASA officials.
It’s also very beneficial and critical to the success of future missions to have a stream of data following the progress of past missions so that lessons can be learned and applied, whatever the outcome.
“By verifying CubeSats are a viable technology for interplanetary missions, and feasible on a short development timeline, this technology demonstration could lead to many other applications to explore and study our solar system,” says NASA.
InSight will smash into the Martian atmosphere at high speeds of approximately 13,000 mph in September 2016 and then decelerate within a few minutes for landing via a heat shield, retro rocket and parachute assisted touchdown on the plains at flat-lying terrain at “Elysium Planitia,” some four degrees north of Mars’ equator, and a bit north of the Curiosity rover.
As I reported in recently here, InSight has now been assembled into its flight configuration and begun a comprehensive series of rigorous environmental stress tests that will pave the path to launch in 2016 on a mission to unlock the riddles of the Martian core.
The countdown clock is ticking relentlessly towards liftoff in less than nine months time in March 2016.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news. | 0.877241 | 3.263651 |
Part one of this series, Flashpoints, looked at all of the ways in which human activity could cause a global catastrophe. This is part two of that series, giving an overview of the numerous cosmic disasters that may threaten life on Earth in the near- to long-term future.
While human-caused catastrophes are entirely within our ability to control and mitigate, cosmic disasters generally are not. While a few of these threats could be reduced by increasing our scientific knowledge of the issues at hand, in many cases, our only hope for long-term survival involves leaving Earth altogether and colonizing other worlds and stars.
Here are all of the ways in which the cosmos might throw us an existential curve ball, ranked in order from highest plausible impact to lowest plausible impact.
1. Eruption of a Supervolcano
The Earth has been volcanically active since its formation more than 4.5 billion years ago. The role volcanic eruptions have played in the history of life on Earth can't be understated, with several of the biggest mass extinctions in Earth's history linked to volcanic activity.
Volcanic eruptions are capable of releasing large amounts of material, including ash and greenhouse gasses, into the atmosphere. In some of the largest known eruptions, this ash has encircled the globe, blocking out sunlight and covering the ground in ash deposits.
When volcanic activity starts blocking out sunlight, photosynthesis becomes compromised, which stunts the growth of plants and plankton alike. When this happens, the entire food chain can be thrown out of wack from the bottom up.
The eruption of Mount Sinabung in Indonesia. Image: Yosh Ginsu
In addition to a compromised food chain, global temperatures can plummet due to the lack of sunlight. This happened most recently in 1816, when a significant eruption in Indonesia caused what became known as the "year without a summer," resulting in crop failures across the Northern hemisphere as a result of low temperatures.
By comparison, the eruption of a supervolcano could cause temperatures to plummet for years on end. Such an event could trigger another ice age, precipitated by a fall in global temperatures and the mass die-off of plants and animals that have adapted to specific environmental niches.
What makes large-scale volcanism particularly risky is that it could completely destroy the agricultural sector we rely on for sustenance, preventing us from producing enough food to feed the nearly 8 billion people on Earth. If sun-deprived conditions caused by atmospheric ash were to continue for several years, this would lead to mass starvation on an unprecedented level.
2. Asteroid Impact
In Plato's Timaeus, the ancient philosopher seems to identify cataclysmic asteroid impacts as a threat to human civilization.
Famously, 65 million years ago, a gigantic asteroid struck Earth and caused the dinosaurs to go extinct. Well, that may not be entirely accurate. Some evidence points to the idea that around the same time this 10-kilometer wide asteroid slammed into what is today the Yucatan Peninsula, mass volcanic eruptions were spewing lava and ash into the atmosphere in today's India. don’t take down the dinosaurs with just one big space rock—you need to set the world on fire at the same time.
That's an example of a convergence of cataclysms. It's thought that the impact event itself may have been so powerful that it actually intensified these volcanic eruptions on the other side of the planet, essentially sealing the fate of the giant lizards and ushering in the age of mammals.
Luckily, over the past few decades, we've gained a considerable amount of knowledge about asteroids and their movements through the solar system. With more advanced asteroid-hunting telescopes being deployed all the time, NASA has been on the forefront of detecting and cataloging near-Earth asteroids for quite some time.
We now know with a large degree of confidence the orbits and trajectories of perhaps 90-95% of all of the near-Earth asteroids larger than one kilometer in size—these are the planet-killing asteroids, large enough that a potential impact would cause destruction across an entire continent. There may be as many as 1,000 of these orbiting in our general vicinity.
From there, things get a bit more bleak. There are an estimated 27,000 near-Earth asteroids larger than 140 meters in size, of which we've only identified approximately one third. Asteroids this large are capable of wiping a small- to mid-sized country off of the map, and it's a little bit disconcerting that the majority of these are yet to be found and cataloged. While such an event would be unlikely to cause the downfall of global civilization, it could certainly cause global instability on a large scale—especially if it impacted a significantly populated area.
And then we have the significant leftovers—an estimated 840,000 near-Earth asteroids measuring between 40 to 140 meters in size, of which we've only identified around 1.5% so far. These objects would be larger than the Chelyabinsk meteor that exploded over Russia in 2013 and injured some 1,500 people, and closer in size to the meteor that caused the infamous Tunguska event in the middle of Siberia back in 1908.
An asteroid over 40 meters in diameter is referred to as a "city-killer," and could conceivably cause significant or even cataclysmic damage to an urban metropolis in the case of a direct hit. The danger here is that city-killers are smaller and more difficult to detect than larger asteroids, so they're much more likely to strike with little or no warning.
A 1.2 kilometer wide impact crater caused by a 50 meter asteroid some 50,000 years ago. This type of impact would completely destroy a city center and most of the surrounding structures. Image: Wikimedia Commons/USGS/D. Roddy
Fortunately, assuming an equal distribution of asteroid impacts across the Earth's surface, it's more likely that such an impact would end up in the middle of the ocean or a large empty expanse of land, like Siberia—so we probably don't need to worry that much. Even so, it could be wise to continue our investment in asteroid detection capabilities.
While we may not know with 100% accuracy when the next deadly asteroid might come our way, we can be 100% confident that one day it will—whether or not we're still around to witness it.
3. A Wandering Rogue Planet
If the prospect of a 10-kilometer wide asteroid slamming into Earth sounds daunting, imagine what a collision with a planet-sized object might do. This has happened before—about 4.5 billion years ago, culminating in the formation of the Earth and our Moon.
But this event occurred between two planetary bodies in unstable orbits within our early solar system, a condition which doesn't exist in today's modern solar system (it's extremely unlikely that Mars, for example, would collide with the Earth at any point in the future). But that doesn't entirely rule out collisions with planetary bodies originating from outside of our solar system.
While all planets must initially form in orbit around a star, they don't necessarily have to remain there. In some cases, planets can be ejected from their originating star system (ie. by being pushed out by the gravitational influence of another large planet or star), becoming doomed to roam interstellar space without being connected to a host star. At this point, they become known as rogue planets.
It's estimated that in our Milky Way Galaxy alone, rogue planets may outnumber the amount of stars in the galaxy. Higher estimates seem to indicate that rogue planets may outnumber stars by several orders of magnitude.
An artist's impression of exoplanets around a distant star. Image: Wikimedia Commons/NASA
A rogue planet entering our solar system from interstellar space could cause significant disruption in the orbits of asteroids, comets, and our neighboring planets. These effects could be particularly worsened depending on the size of the rogue planet that comes to visit—we know from surveys of nearby star systems that exoplanets several times more massive than Jupiter appear to be common.
The instability caused by a close encounter with a wandering rogue planet could send massive comets from the Oort cloud raining down on the inner solar system, or even destabilize the orbits of other planets and cause them to be ejected from our solar system entirely (or send them colliding into another planet).
Since the vast majority of our solar system consists of empty space, it's extremely unlikely that such an object would collide with another planetary body or become trapped in orbit around our sun, but this is another possibility.
Worst of all, since a rogue planet wouldn't be emitting any visible light, detecting these objects in interstellar space would be extremely difficult. We likely wouldn't know that such an object was approaching until it was already knocking at our door.
4. A Close Encounter with a Star
Planetary objects aren’t as big as they get—we might also need to consider the possibility that neighboring stars could get a little too close for comfort.
We know that the Oort cloud may extend as far as several light years beyond our solar system. Any star entering within the Oort cloud could cause an incredible amount of disruption, resulting in a bombardment of icy comets and planetesimals raining down on us from the outer solar system.
Proxima Centauri, our Sun's nearest neighboring star, currently sits at a comfortable 4.2 light years away. At this distance, this relatively small star (being only around 1/8th the mass of our own sun) isn't large enough or close enough to cause any such perturbations of the Oort cloud. But there are plenty of other stars in our galactic neighborhood, and they have a habit of moving around.
At 4.37 light years away, Alpha Centauri is the nearest star system to Earth after our own sun. Image: ESO/DSS 2
It's currently estimated that in about 1.3 million years, Gliese 710, a nearby star with 60% the mass of our Sun, may approach as close as 0.22 light years to Earth. The results of this encounter may be catastrophic for Earth and the inner solar system in general, causing massive comets to be hurtled into the inner solar system at a highly accelerated rate for several million years.
Assuming life on Earth still exists by then, the Sun's close encounter with Gliese 710 would significantly increase the probability and frequency of a significant impact event occurring—perhaps even an impact more devastating than what happened to the dinosaurs.
5. Black Holes in our Midst
Since the concept of black holes entered the scientific canon and the public lexicon several decades ago, humans have been captivated by the concept of a point in space from which nothing—not even light—can escape. In addition to their mystique, black holes may also represent a highly underrated existential threat to life on Earth.
This is for good reason. The mere existence of black holes had remained in the realm of scientific theory up until 2019, when the first-ever direct image of a black hole was captured.
The first-ever image of a black hole was released in 2019 after tremendous effort. The M87 galaxy, with a supermassive black hole at its center, is located 53 million light years from Earth. Image: EHT Collaboration
The recency of this image reveals the problem: because their gravitational fields are so strong that not even light can escape the event horizon, detecting a black hole against the backdrop of empty space is impossible. Because we can't detect them, we can't count them. And because we can't count them, we can never know for certain how many there are, and what the distribution curve is.
Nobody really knows how many black holes might exist in any given galaxy, or what the average size of these black holes might be. It's plausible that black holes ranging in size from a few dozen to a few hundred solar masses may be common, millions of which could be distributed throughout our galaxy without our knowledge. Detecting these objects from afar would be a nearly impossible feat, and it's conceivable that we wouldn't recognize their presence until we begun noticing the telltale signs of gravitational abnormalities in our galactic neighborhood.
The effects of a massive invisible object in our vicinity could be profound. Just as a rogue planet entering our solar system or a nearby star getting a little too close for comfort, a large black hole could push or tug at our solar system and nearby star systems from afar.
The large gravitational disruption that a black hole encounter would entail could send our sun hurtling towards the center of the galaxy, or could increase the probability of an unwanted encounter with a nearby star system.
6. A Nearby Supernova or Gamma Ray Burst
As if black holes and planetary collisions weren't worrying enough, we also need to contend with the fact that, at the end of their life cycle, some of the largest stars tend to explode and spew gamma radiations over long distances of space.
Gamma rays consist of extremely high-energy electromagnetic waves that can be hazardous to biological life. In some cases, gamma ray bursts produced by an exploding hypernova (a stellar explosion that's an order of magnitude more powerful than a supernova) can become narrowly focused into concentrated beams. If any of these gamma-ray beams were to be directed towards Earth, it could destroy the entire Ozone layer and leave our biosphere exposed to high-radiation cosmic rays.
An image of the remnants of Supernova 1987A, some 168,000 light years from Earth. Image: ESO/L. Calçada
The beams from gamma ray-ray bursts can be so powerful that, when pointed in our direction, they've been detected at distances up to 10 billion light years away. At these distances, gamma-rays don't pose any threat to life on Earth. But if such an outburst were to originate from inside our Milky Way Galaxy, especially within a distance of a few thousand light years, that wouldn't be a good day for life on Earth.
Such an event is thought to be fairly uncommon, perhaps occurring every one billion years or so on average because hypernovae are relatively rare. But a hypernova isn't the only type of explosion that can produce high-powered gamma rays: we also have to consider the risk that a passing star could explode as a regular old supernova.
Because supernovae are far more common, these are far more likely to disrupt life on Earth than a distant gamma-ray burst. It's estimated that a sufficiently powerful supernova occurring within 50 light years of Earth may produce enough gamma radiation to destroy all or part of the Ozone layer. And the closer an explosion occurs, or the more x-rays and gamma rays it produces, the more devastating such an encounter could be.
One average, it's estimated that a supernova explosion occurs within 33 light years of Earth every 240 million years or so. Such an event may have been responsible for a mass-extinction event some 450 million years ago, in which up to 85% of marine species went extinct (during the Ordovician-Silurian extinction events).
If such an event were to occur today, there would be little we could do to mitigate the effects of sudden and total Ozone loss.
7. Fluctuations in our Sun's Energy Output
We don’t need to look outside of our solar system for killer stars—just look up in the sky on a sunny day (or don’t, because your retinas might burn out of your skull).
Forget about light-year distances; there's a gigantic nuclear fusion explosion in space going on just 8 light-minutes away from Earth, every second of every day, for the past 4.6 billion years. And most of the time, we aren't even worried.
A closeup of the Sun captured by NASA's Solar Dynamics Observatory. Image: NASA/GSFC/Solar Dynamics Observatory
We know that the Sun is capable of producing solar storms and solar flares. While these aren't typically powerful enough to seriously disrupt life on Earth, there is reason to consider our own Sun as a potential driver of civilization collapse.
Back in 1859, a powerful geomagnetic storm had a direct impact on Earth. This is known as the Carrington Event, and it was powerful enough to bring down telegraph systems at the time. Had this type of event occurred today, it would have caused widespread blackouts and damage to the electrical grid. Since most of our civilization runs on electricity and relies on digital computers, any significant damage to these systems caused by a future solar storm could cause an unprecedented global disruption with cost estimates ranging in the trillions of dollars.
While we could take steps to make sure our electronics and electrical grids are robust enough to survive such an event, the Sun does have another trick up it's sleeve. Over time, the Sun's energy output tends to fluctuate—it can decrease over some ~11 year cycles, and increase over others. While these fluctuations are usually very small, they do have an impact on the Earth's climate: it's thought that the Sun's current cycle of increased energy output may be responsible for anywhere from 7% to upwards of 30% of global warming over the past 30 years (with the rest being attributed to human activity).
It's thought that the Sun's energy fluctuations over time may also be partly responsible for the numerous glacial periods (or ice ages), followed by warmer interglacial periods (the climate of the past 11,700 years) that have occurred in the Northern Hemisphere over the past 2.5 million years. Of course, due to the complexity of these systems and the numerous drivers of warming and cooling periods, scientists can't be completely sure to what extent different inputs (such as solar fluctuations) may account for climate fluctuations.
This puts human civilization in a precarious spot, faced with two extremes: unprecedented global warming, and the prospect of slipping into another ice age. Sometimes it doesn't take a direct impact or a supernova to cause a global catastrophe, but rather the slow progression of complex natural cycles that we don't yet fully understand.
8. The Sun's Red Giant Phase
While fluctuations in solar output play out over the short-term (hundreds or thousands of years), the long-term future of our Sun looks a lot different.
For one, the Sun's luminosity has increased by about 1% every 110 million years. Within a few hundred million years, the increasing energy output of the Sun may have may begin having a more extreme impact on Earth's climate, causing global temperatures to rise and making life on Earth more difficult overall.
This increased luminosity will continue until, in about 5 billion years (when the sun is 67% more luminous than today), all of its hydrogen fuel will be exhausted and it will begin transitioning into its red giant phase. Life on Earth won't last long enough to see this, as increasing solar output and global warming will likely cause all life on Earth to go extinct within 2.8 billion years.
If human civilization is still around a few hundred million years from now, the only option for our long-term survival would be either moving the Earth or moving ourselves to other planets altogether (ie. Mars) as solar output increases. That is, if we haven't packed up and left the solar system entirely by that point.
9. The Heat Death of the Universe
If human civilization does manage to colonize other stars and worlds in the galaxy, then there's a good chance we'll survive well past the Sun's red giant phase. But there are limits. And there's no escaping the slow and eventual death of the universe itself.
The laws of physics tells us that in any system, entropy always increases. In short, by natural processes, thermal energy always progresses towards achieving greater equilibrium and less structure.
For example, take a hot cup of coffee in an enclosed room with a set temperature. Added together, the room and the coffee have a set amount of energy (in the form of temperature), but it's unbalanced. The freshly brewed cup of hot coffee possesses more energy relative to the rest of the room.
Over time, the amount of thermal energy in the coffee will diminish. The excess heat will dissipate into the room, slightly warming it. Eventually, the cup of coffee and the rest of the room will achieve the same temperature and energy level—they will have achieved equilibrium. This is an example of entropy doing its thing.
And this same process is playing out across the entire universe.
Thousands of distant galaxies captued by Hubble, some of which are more than 13 billion light years away. Image: NASA/ESA et al.
Trillions of years from now, all of the stars in the universe will have expended all of the available fuel for nuclear fusion to take place. Star formation will come to an end, the universe will go dark, and the temperature of all of the planets in the universe will gradually approach absolute zero.
Life as we know it relies primarily on solar energy to survive (all of the food you or I eat can only exist thanks to photosynthesis). Some lifeforms can survive on chemical energy produced through geological processes, but even this energy source is short-lived: as planets cool, geologic activity grinds to a halt.
Once all of the stars in the universe have gone dark, there won't be any more energy available for biological processes to continue. Life will cease to exist.
Assuming civilization is able to survive until then, the final heat death of the universe seems like a cruel joke. Even if we do manage to avoid human-induced global catastrophes and navigate through these potential cosmic cataclysms, it won't be enough to continue existing indefinitely. No matter what we do, our fate as living beings is ultimately sealed by the cosmos itself.
Cover image published under CC0 1.0. | 0.926019 | 3.495598 |
Crescent ♌ Leo
Moon phase on 14 September 2020 Monday is Waning Crescent, 26 days old Moon is in Leo.Share this page: twitter facebook linkedin
Previous main lunar phase is the Last Quarter before 4 days on 10 September 2020 at 09:26.
Moon rises after midnight to early morning and sets in the afternoon. It is visible in the early morning low to the east.
Moon is passing about ∠12° of ♌ Leo tropical zodiac sector.
Lunar disc appears visually 0.4% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1901" and ∠1908".
Next Full Moon is the Hunter Moon of October 2020 after 17 days on 1 October 2020 at 21:05.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 26 days old. Earth's natural satellite is moving from the second to the final part of current synodic month. This is lunation 255 of Meeus index or 1208 from Brown series.
Length of current 255 lunation is 29 days, 8 hours and 19 minutes. This is the year's shortest synodic month of 2020. It is 12 minutes shorter than next lunation 256 length.
Length of current synodic month is 4 hours and 26 minutes shorter than the mean length of synodic month, but it is still 1 hour and 44 minutes longer, compared to 21st century shortest.
This lunation true anomaly is ∠322.3°. At the beginning of next synodic month true anomaly will be ∠341.2°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
8 days after point of apogee on 6 September 2020 at 06:31 in ♈ Aries. The lunar orbit is getting closer, while the Moon is moving inward the Earth. It will keep this direction for the next 4 days, until it get to the point of next perigee on 18 September 2020 at 13:44 in ♎ Libra.
Moon is 377 132 km (234 339 mi) away from Earth on this date. Moon moves closer next 4 days until perigee, when Earth-Moon distance will reach 359 081 km (223 123 mi).
3 days after its ascending node on 10 September 2020 at 23:05 in ♊ Gemini, the Moon is following the northern part of its orbit for the next 9 days, until it will cross the ecliptic from North to South in descending node on 23 September 2020 at 12:33 in ♐ Sagittarius.
3 days after beginning of current draconic month in ♊ Gemini, the Moon is moving from the beginning to the first part of it.
2 days after previous North standstill on 12 September 2020 at 05:25 in ♋ Cancer, when Moon has reached northern declination of ∠24.353°. Next 10 days the lunar orbit moves southward to face South declination of ∠-24.458° in the next southern standstill on 24 September 2020 at 19:11 in ♑ Capricorn.
After 2 days on 17 September 2020 at 11:00 in ♍ Virgo, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.151398 |
Phoenix Robotic Arm Camera Sees Possible Ice
A view of the ground underneath NASA's Phoenix Mars Lander adds to evidence that descent thrusters dispersed overlying soil and exposed a harder substrate that may be ice.
The image received Friday night from the spacecraft's Robotic Arm Camera shows patches of smooth and level surfaces beneath the thrusters.
"This suggests we have an ice table under a thin layer of loose soil," said the lead scientist for the Robotic Arm Camera, Horst Uwe Keller of Max Planck Institute for Solar System Research, Katlenburg- Lindau, Germany.
The Robotic Arm Camera on NASA's Phoenix Mars Lander captured this image underneath the lander on the fifth Martian day, or sol, of the mission. Descent thrusters on the bottom of the lander are visible at the top of the image.
This view from the north side of the lander toward the southern leg shows smooth surfaces cleared from overlying soil by the rocket exhaust during landing. One exposed edge of the underlying material was seen in Sol 4 images, but the newer image reveals a greater extent of it. The abundance of excavated smooth and level surfaces adds evidence to a hypothesis that the underlying material is an ice table covered by a thin blanket of soil.
The bright-looking surface material in the center, where the image is partly overexposed may not be inherently brighter than the foreground material in shadow.
"We were expecting to find ice within two to six inches of the surface," said Peter Smith of the University of Arizona, Tucson, principal investigator for Phoenix. "The thrusters have excavated two to six inches and, sure enough, we see something that looks like ice. It's not impossible that it's something else, but our leading interpretation is ice." | 0.817599 | 3.12499 |
Telling Time on Mars
A Mars solar day (typically referred to as a “sol”) has a length of 24 hours, 39 minutes, and 35.244 seconds. This difference in duration in comparison to an Earth day, while slight, nevertheless warrants careful consideration of how best to tell time on Mars. Although humans have yet to set foot on the planet, the question of time bears relevance for even unmanned spacecraft due to the necessity of daylight for solar panels and the sun’s effect on temperature fluctuations in Mars’ thin atmosphere.
Using Earth time to measure events on Mars would have little practical benefit; even if clocks were initially synchronized between the two planets, the 40-minute time differential per day means that Earth time would rapidly diverge to the point where it had no bearing on the local solar time at Mars. Proposed alternatives to Earth time have included adding a 25th partial Earth hour at the end of each sol, an altogether new system based on powers of 10, and stretching terrestrial measurements to preserve the convention of a 24-hour day. The last of these has been the method which Mars missions have employed to date.
This system would preserve the length of terrestrial hours, minutes, and seconds, but add an extra partial hour after midnight, and has made fictional appearances in Kim Stanley Robinson’s Mars trilogy, as well as Philip K. Dick’s Martian Time-Slip.
Despite the practicalities of preserving conventions familiar to Earth residents, the partial hour proposal exhibits several disadvantages. This system could potentially require the addition of a leap second every four days, and calculating elapsed time across the partial hour boundary poses mathematical inconveniences (for example, the elapsed time between 23:30 and 01:00 is not an even hour and a half, but a more cumbersome two hours and 10 minutes). Furthermore, a lack of uniformity between hours complicates the process of celestial navigation (specifically, determining one’s longitude by observing the rise of the Sun, Phobos, or Deimos and comparing local time to the expected time of occurrence at the prime meridian).
The proposal of decimal time seeks to use the settlement of Mars as an opportunity to replace Earth’s somewhat unwieldy base-24 and base-60 time system with a sleeker one utilizing units of 10. Earth seconds could provide the basis for such a system: terrestrial time already uses milliseconds and microseconds, and this convention could be extended to kiloseconds (roughly 15 minutes), megaseconds (about 12 days), and gigaseconds (around 32 years).
This proposal looks forward to a time when civilization spans several celestial bodies, with the argument that this standardized form of time would avoid political or social issues arising from prioritizing the use of a system associated with any one planet. A more Mars-centric approach would involve dividing a sol by powers of 10 to yield centidays (around 15 Earth minutes), millidays (roughly one and a half minutes), and microdays (10 microdays being slightly faster than a second).
Whatever the method, the principal advantage of decimal time lies in its ability to facilitate simple calculations by aligning time measurements with the base-10 system of modern Arabic numerals. Changing from seconds to hours (as one might do when converting meters per second to kilometers per hour) involves a factor of 3600, while similar calculations in decimal time only require more straightforward powers of 10. On the other hand, transitions to such a system have failed to meet widespread popular acceptance in the past, such as the unsuccessful attempts made during the French Revolution. Moreover, Mars geographical coordinates already use the same base-60 degrees, minutes, and seconds as on Earth, and existing equations of celestial navigation rely on correspondence between geographical and chronological systems where, for example, one hour/minute/second of time equals 15 degrees/minutes/seconds of longitude.
The system currently in place for telling time on Mars simply divides the solar day by 24 hours to yield familiar hours, minutes, and seconds, each 1.0275 times longer than their terrestrial equivalents. This method has the practical benefits of remaining similar to Earth time without necessitating the inconveniences of an additional partial hour, facilitating understanding of the planet’s orientation toward the Sun (i.e. 6:00 AM means roughly the same thing on both Earth and Mars), and allowing unaltered terrestrial equations of celestial navigation to apply on Mars.
The 1976 Viking Lander missions originally adopted this system, and it has seen use ever since—members of the Mars Exploration Rover mission even utilized custom-made wristwatches with strategically-placed lead weights to slow the movement of the hands to Mars time. The Goddard Institute for Space Studies’ publicly-available Mars24 Sunclock software, which displays Mars time alongside other information such as lander locations and the relative orbital positions of Earth and Mars, uses stretched time as well.
Despite the acceptance of this method of timekeeping, the potential for confusion between Earth units and Mars units does exist. For this reason, it has been recommended that differing terminology should be employed for the two systems. As highlighted above, the scientific community has already adopted a separate word to distinguish Mars sols from Earth days, but other units of time must currently be preceded by “Earth” or “Mars” to establish clarity.
Prime Meridian and Time Zones
As mentioned above, comparing the occurrence of sunrise and moonrises at local time to their expected occurrences at the prime meridian provides an accurate method to assess longitude. But where does one define the prime meridian on an extraterrestrial planet? On Mars, the definition of longitude 0° was originally set in 1877 based on the region Sinus Meridiani, and later refined to a specific crater named Airy-0. Recent proposals have suggested fixing the prime meridian at 47.95137° east of Viking Lander 1, a more precisely-defined location approximately at the center of Airy-0..
Rather than globally-defined time zones, Mars missions have traditionally used estimates of local solar time at the landing site, as was the case on Earth prior to the adoption of standard time in the 19th century. Even so, creating time zones on Mars as was done on Earth by dividing the planet’s surface into longitudinal sections and offsetting the time from that established at a given point remains a possibility. The Mars24 Sunclock illustrates this with 15° sections offset from the prime meridian at Airy-0, where mean solar time is referred to as “Airy Mean Time” (AMT).
- Allison, M., & Schmunk, R. (2018, December 13). NASA GISS: Mars24 Sunclock — Technical Notes on Mars Solar Time. Retrieved June 28, 2019, from https://www.giss.nasa.gov/tools/mars24/help/notes.html.
- Timekeeping on Mars. (2019). In Wikipedia. Retrieved from https://en.wikipedia.org/w/index.php?title=Timekeeping_on_Mars&oldid=903883982
- Zubrin, R. (2011). The Case for Mars. Simon & Schuster.
- Robinson, K. S. (2003). Red Mars. Random House Publishing Group.
- Dick, P. K. (2012). Martian Time-Slip. Houghton Mifflin Harcourt.
- Mackenzie, B. (1989). Metric Time for Mars. 75, 539. Retrieved from http://ops-alaska.com/time/mckenzie/mckenzie.htm
- Decimal time. (2019). In Wikipedia. Retrieved from https://en.wikipedia.org/w/index.php?title=Decimal_time&oldid=902701795
- Mars Exploration Rover Mission: Spotlight. (2004). Retrieved June 28, 2019, from https://mars.nasa.gov/mer/spotlight/spirit/a3_20040108.html
- NASA GISS: Mars24 Sunclock — Time on Mars. (n.d.). Retrieved June 28, 2019, from https://www.giss.nasa.gov/tools/mars24/
- Kuchynka, P., Folkner, W. M., Konopliv, A. S., Parker, T. J., Park, R. S., Le Maistre, S., & Dehant, V. (2014). New constraints on Mars rotation determined from radiometric tracking of the Opportunity Mars Exploration Rover. Icarus, 229, 340-347.
- International Astronomical Union | IAU. (n.d.). Retrieved June 28, 2019, from https://www.iau.org/news/announcements/detail/ann18010/ | 0.816206 | 3.924647 |
NASA’s Phoenix lander may have already hit pay dirt with its first scoop of Martian soil – it contains white streaks that could be water ice. Meanwhile, mission engineers have fixed an electrical glitch on an important Phoenix instrument, restoring it to health.
“It’s been a thrill for me this first week after landing on the permafrost region in the Northern Arctic on Mars to find out that we’re in a really great place for doing the science we plan to do,” said Peter Smith of the University of Arizona in Tucson, US, Phoenix’s chief scientist, at a press conference on Monday.
The $420-million spacecraft has now gouged out its first scoopful of Martian dirt from an area informally known as the Knave of Hearts, using its 2.3-metre robotic arm.
The brain trust isn’t exactly sure if this stuff is actually ice or salt, since it’s theorized that Mars’ water was a seriously salty brine before it finally dried up completely. But I guess the first chemical analysis will find out, won’t it?
The goal of finding an Earth-like planet around another star has just come closer. Astronomers announced today they have discovered a planet of about three Earth masses orbiting a star smaller than our sun.
The planet has the closest mass to Earth of all the known extrasolar planets, and is the lightest planet ever found orbiting a normal-size star. “Our discovery indicates that even the lowest mass stars can host planets,” David Bennett of the University of Notre Dame, who led an international team of astronomers to the discovery, said on Monday at the American Astronomical Society meeting in St Louis, Missouri, US.
The planet is referred to as MOA-2007-BLG-192L and is around 3000 light years from Earth. Planet formation theory suggests it is likely made mostly of rock and ice.
The planet’s orbit around the host star is of a similar radius to the orbit of Venus, although it is likely to be much colder than Pluto. That is because the host star, thought to be a brown dwarf between 6 and 8 percent of the Sun’s mass, may not be large enough to sustain nuclear reactions in its core.
Believe it or not, astronomers and other planet hunters are getting rather good at finding extrasolar planets. The method used in this case is gravitational microlensing, which uses an object’s gravity that warps the light from another object behind it which magnifies the image of it.
Not my idea, blame Einstein. I just post the stuff. Read the article.
Also, read this post at Paul Gilster’s Centauri Dreams, they explain it better than I can.
And I can’t let this day go by without a little rant against the rampant corporatism that has the nation and the world by our collective throats and our wallets:
On Thursday, new Time Warner Cable Internet subscribers in Beaumont, Texas, will have monthly allowances for the amount of data they upload and download. Those who go over will be charged $1 per gigabyte, a Time Warner Cable executive told the Associated Press.
Just 5 percent of the company’s subscribers take up half of the capacity on local cable lines, Leddy said. Other cable Internet service providers report a similar distribution.
“We think it’s the fairest way to finance the needed investment in the infrastructure,” Leddy said.
Metered usage is common overseas, and other U.S. cable providers are looking at ways to rein in heavy users. Most have download caps, but some keep the caps secret so as not to alarm the majority of users, who come nowhere close to the limits. Time Warner Cable appears to be the first major ISP to charge for going over the limit: Other companies warn, then suspend, those who go over.
Time Warner can bite me. Trouble is, Verizon and all these other criminals do the same, plus report you to the ‘Ministry’ of ‘Homeland’ Security!
So much for the sanctity of the InnerTubes. Big Brother is not only watching, but making us pay in order for them to watch! | 0.841556 | 3.501135 |
A new color map of dwarf planet Ceres, which NASA's Dawn spacecraft has been orbiting since March 2015, reveals the diversity of the surface of this planetary body. Differences in morphology and color across the surface suggest Ceres was once an active body, Dawn researchers said yesterday at the 2015 General Assembly of the European Geosciences Union in Vienna.
"This dwarf planet was not just an inert rock throughout its history. It was active, with processes that resulted in different materials in different regions. We are beginning to capture that diversity in our color images," said Chris Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles.
New color map of dwarf planet Ceres. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.
The Dawn mission made history on March 6 as the first spacecraft to reach a dwarf planet, and the first spacecraft to orbit two extraterrestrial targets. Previously, Dawn studied giant asteroid Vesta from 2011 to 2012, uncovering numerous insights about its geology and history. While Vesta is a dry body, Ceres is believed to be 25 percent water ice by mass. By comparing Vesta and Ceres, scientists hope to gain a better understanding of the formation of the solar system.
Ceres' surface is heavily cratered, as expected, but appears to have fewer large craters than scientists anticipated. It also has a pair of very bright neighboring spots in its northern hemisphere. More detail will emerge after the spacecraft begins its first intensive science phase on April 23, from a distance of 13 500 km (8 400 miles) from the surface, said Martin Hoffmann, investigator on the Dawn framing camera team, based at the Max Planck Institute for Solar System Research, Göttingen, Germany.
The visible and infrared mapping spectrometer (VIR), an imaging spectrometer that examines Ceres in visible and infrared light, has been examining the relative temperatures of features on Ceres' surface. Preliminary examination suggests that different bright regions on Ceres' surface behave differently, said Federico Tosi, investigator from the VIR instrument team at the Institute for Space Astrophysics and Planetology, and the Italian National Institute for Astrophysics, Rome.
Based on observations from NASA's Hubble Space Telescope, planetary scientists have identified 10 bright regions on Ceres' surface. One pair of bright spots, by far the brightest visible marks on Ceres, appears to be located in a region that is similar in temperature to its surroundings. But a different bright feature corresponds to a region that is cooler than the rest of Ceres' surface.
These images, from Dawn's visible and infrared mapping spectrometer (VIR), highlight two regions on Ceres containing bright spots. The top images show a region scientists have labeled "1" and the bottom images show the region labeled "5." Region 5 contains the brightest spots on Ceres. Image credit: NASA/JPL-Caltech/UCLA/ASI/INAF.
The origins of Ceres' bright spots, which have captivated the attention of scientists and the public alike, remain unknown. It appears the brightest pair is located in a crater 92 km (57 miles) wide. As Dawn gets closer to the surface of Ceres, better-resolution images will become available.
"The bright spots continue to fascinate the science team, but we will have to wait until we get closer and are able to resolve them before we can determine their source," Russell said.
Both Vesta and Ceres are located in the main asteroid belt between Mars and Jupiter. The Dawn spacecraft will continue studying Ceres through June 2016.
Featured image: New color map of dwarf planet Ceres. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA. | 0.911586 | 3.907491 |
Historic Close Encounter with Pluto Captured with a Little Help from Friends at Materion
After 9-1/2 years hurtling 3 billion miles through the solar system, NASA's tiny New Horizons spacecraft passed by Pluto July 13th, providing scientists breathlessly waiting back on earth arresting new images of the dwarf planet. High-performance materials from Materion Precision Optics were on board for much more than the ride.
Traveling at more than 31,000 miles per hour, the probe crossed the face of Pluto in just three minutes, yet allowed for our closest look ever (from "only" 7,800 miles away) and marking the last great American flyby of the planets.
NASA's New Horizon mission is to collect data that will shed light on the beginnings of the solar system. The spacecraft -- about the size of a grand piano and swathed in gold-colored foil -- spent almost two-thirds of its time in hibernation designed to keep its systems operational.
Spacecraft Camera Contains Materion Filters
George Allen, Product Design Engineer at Precision Optics, describes Materion's contribution to the spacecraft. "Our customer Ball Aerospace, in cooperation with the Southwest Research Institute (SwRI), built the ‘Ralph' instrument, which is a critical component aboard New Horizons. ‘Ralph' includes the Multispectral Visible Imaging Camera (MVIC), which generates visible and near infrared multi-spectral images and the Linear Etalon Imaging Spectral Array (LEISA), provided by NASA/Goddard, which generates short wave infrared hyperspectral images. Materion was responsible for manufacturing the filters for MVIC as well as a beam splitter used to separate the visible wavelengths used in MVIC from the infrared wavelengths used by LEISA."
Exciting new color images of Pluto and its five moons are being transmitted from New Horizons and reveal the diversity of their surface terrains. The images come courtesy of the ‘Ralph' camera and filters provided by Materion. "One crucial aspect of deep space missions is that all the components, such as the filters we supply, need to reliably function after many years of travel in a stressful space environment. These ‘space qualified' filters are an important part of Materion's durable optics offerings," added Tom Mooney, Product Engineering Manager, Precision Optics.
The New Horizons mission to Pluto is considered a staggering technological achievement and the most exciting space mission in a generation. The geologic and atmospheric data collected is expected to help interpret the formation of the whole planetary system. The ‘Ralph' camera has allowed us to capture high-resolution topographical images of a complex, variegated surface marked by chasms, mounds, craters and fault lines, as well as a strikingly bright heart-shaped region.
NASA's New Horizons spacecraft captured on Pluto for the first time features that may be cliffs, as well as a circular feature that could be an impact crater. Rotating into view is the bright heart-shaped feature. This annotated version includes a diagram indicating the dwarf planet's north pole, equator and central meridian. Image credit: NASA/JHUAPL/SWRI
Artist conception of New Horizons Spacecraft. Image credit: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute. | 0.828032 | 3.276838 |
Astronomers used the European Southern Observatory telescope and spotted a planet-star scheme that resembles the Jupiter-Sun one.
A Brazilian-led team made the discovery in an effort to find other stars like the Sun in order to discover other planetary systems that are similar to our own. The researchers found the twin of Jupiter at the exact distance as our Jupiter orbits from the Sun, orbiting from a star resembling the Sun called HIP 11915.
This discovery has been accredited to HARPS, which is one of the most exact planet hunting instruments in the world, installed on the European Southern Observatory telescope from Chile, in the La Silla Observatory.
The scientists say that even though other people have found planets which are similar to Jupiter and orbiting other stars inside the galaxy, the recently discovered exoplanet is the most similar to the Jupiter and Sun system in both distance and mass from the host star, and in similarity between our Sun and the planet’s host star.
The host of the exoplanet, the Sun twin called HP 11915, is similar in mass to our Sun and is also around the same age. But there are even more similarities, such as its composition which is also similar to our Sun’s. The chemical signature of the Sun could be marked by the existence of planets in the Solar System, which hints at a possibility that there could also be rocky planets around the newly discovered HP 11915.
Jorge Melendez from the Universidade de Sao Paolo in Brazil, co-author of the study and leader of the team of astronomers said that the search for an Earth 2.0 and a complete Solar System 2.0 has been one of the most fascinating projects in astronomy. He added that they are delighted to be part of the research which is only possible because of the observational facilities which are provided by the European Southern Observatory.
Megan Bedell of the University of Chicago and also the lead author of the study said that after 20 years of searching for exoplanets, we are at long last starting to discover gas planets resembling those in our Solar System thanks to instruments such as HARPS. This recent discovery is in every aspect a very thrilling sign that there may be other solar systems out there just waiting to be found.
Some other observations are required in order to confirm the finding but there is no doubt that HIP 11915 is among the most appealing candidates to hold a planetary system that is similar to our own.
Image Source: ngm.nationalgeographic.com | 0.870323 | 3.37447 |
Deimos Dust for Mars Orbit Insertion
A friend proposes a fast transfer to Mars; 10 to 20% more delta V at Earth results in a much faster trip there. However, the arrival velocity would be MUCH higher, and difficult to shed by aerobraking without high lift (and high centripedal gees) to remain within the appropriate density layer of the atmosphere of this small, low gravity planet. The v²/r - g acceleration arriving at Mars would be much higher for Mars than for Apollo.
The difficulty is worse for large heavy spacecraft; there is not enough atmosphere for a low speed parachute landing.
Mars Missions in the Age of Robots
Going to Mars with microbe-infested humans is also a very bad idea, possibly the worst scientific crime of the millenium. If a motivation for a Mars mission is a search for life, it is likely that the only life found will be the microbes shed by humans. A robot probe can be autoclaved; humans cannot. However, humans can go to prepared habitats on Phobos, and control robots from there. Getting to Phobos will be as difficult as landing with aerobraking.
Before humans go to Mars, we must rule out the possibility of ancient life anywhere that human contamination can reach. The Martian atmosphere is thin, but it is windy and connects the whole planet. So, we should explore the most of the surface with robots, ruling out surface fossil life to a very high confidence level in every possible kind of niche. Mars is frozen; it is reasonable to assume that (with proper precautions) material below the surface ice level can be kept absolutely free of contamination. However, the robotic exploration of the planet will require very many robots a very long time.
If we screw this up, we destroy our chances of learning the truth - forever.
Phobos Low Station
But what if there is a cheap way to get robots to Mars, and humans to Phobos, to operate those robots from a close enough distance to simulate "walking on Mars in a space suit" via telepresence, taking advantage of rapid lightspeed communication from Phobos, or Low Mars Orbit, or from a manned station on a tether hanging down from Phobos? The round trip speed of light delay from a station at 1000 km, through a chain of relay satellites, to a surface station on the opposite side of Mars is less than 10 milliseconds. We are laearning to operate robot submersibles in the ocean from much larger distances.
The "gravity" experienced on this hanging station would be "only" 2.2 m/s², only 60% of Mars surface gravity, but that also means the tether can be made without unobtanium. See AcousticClimber for a way to power climbers up and down that tether to the main base on Phobos.
We continuously monitor the distance to the LAGEOS laser geodesy satellites to micrometer precision, through a thick and turbulent atmosphere. These satellites are now the reference standard for all surface measurements on Earth. They are accurate enough to observe the slow drift of the continents via plate tectonics, and calibrate the GPS navigation system. They are inert balls of aluminum and brass covered with retroreflectors. It is conceivable that we could use them to calibrate GPS directly, and achieve nanometer precision with signal averaging.
We do vastly better with LIGO era laser technology, with 1e-22 precision. That has been compared to measuring the distance to Proxima Centauri to an accuracy of the thickness of a human hair. With distributed retroreflectors and an accurate computer simulation of the solar system, we can make hyperprecise calculations of positions and orbits. If we make this a priority, we can compute the position of spacecraft and electromagnetically launched objects to millimeters over gigameter distances. That means we can learn to hit a very small bullseye over solar system distances.
Harenodynamic Braking with "Deimos Dust"
In the early 1980s, Krafft Ehricke wrote about a "slide lander" for braking lunar landers to a stop on the Moon, without using propellant on board the vehicle. The vehicle would skid to a stop on a carefully prepared runway. That was in a low-accuracy era, but the spacecraft would need to be lined up to millimeter precision and milliradian trajectory angles to remain in contact with the runway all the way from orbital velocity to a stop.
An interesting idea, but we can do better. We can use low velocity mortars or short launchloop style accelerators to launch packets of carefully sorted lunar dust into the center of the path of a lander's heat shield, detals here. A vehicle travelling from Earth will arrive at 2520 m/s and require careful aiming; however, a 1500
Escape velocity from Deimos orbit to an interplanetary orbit is 1.35 km/s. Deimos is 1.47e15 kg of rock and sand. can be mechanically converted into arbitrarily small grains of dust, sorted by size electrostatically in high vacuum. | 0.83048 | 3.069046 |
Matching up maps of matter and light from the Dark Energy Survey and Fermi Gamma-ray Space Telescope may help astrophysicists understand what causes a faint cosmic gamma-ray glow.
Astrophysicists have come a step closer to understanding the origin of a faint glow of gamma rays covering the night sky. They found that this light is brighter in regions that contain a lot of matter and dimmer where matter is sparser – a correlation that could help them narrow down the properties of exotic astrophysical objects and invisible dark matter.
The glow, known as unresolved gamma-ray background, stems from sources that are so faint and far away that researchers can’t identify them individually. Yet, the fact that the locations where these gamma rays originate match up with where mass is found in the distant universe could be a key puzzle piece in identifying those sources.
The background is the sum of a lot of things ‘out there’ that produce gamma rays. Having been able to measure for the first time its correlation with gravitational lensing – tiny distortions of images of far galaxies produced by the distribution of matter – helps us disentangle them,” said Simone Ammazzalorso from the University of Turin and the National Institute for Nuclear Physics (INFN) in Italy, who co-led the analysis.
The study used one year of data from the Dark Energy Survey (DES), which takes optical images of the sky, and nine years of data from the Fermi Gamma-ray Space Telescope, which observes cosmic gamma rays while it orbits the Earth.
“What’s really intriguing is that the correlation we measured doesn’t completely match our expectations,” said Panofsky fellow Daniel Gruen from the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University, who led the analysis for the DES collaboration. “This could mean that we either need to adjust our existing models for objects that emit gamma rays, or it could hint at other sources, such as dark matter.”
The study has beenaccepted for publication in Physical Review Letters.
Two sensitive ‘eyes’ on the sky
Gamma radiation, the most energetic form of light, is produced in a wide range of cosmic phenomena – often extremely violent ones, such as exploding stars, dense neutron stars rotating at high speeds and powerful beams of particles shooting out of active galaxies whose central supermassive black holes gobble up matter.
Another potential source is invisible dark matter, which is believed to make up 85 percent of all matter in the universe. It could produce gamma rays when dark matter particles meet and destroy each other in space.
The Large Area Telescope (LAT) on board the Fermi spacecraft is a highly sensitive “eye” for gamma radiation, and its data provide a detailed map of gamma-ray sources in the sky.
But when scientists subtract all the sources they already know, their map is far from empty; it still contains a gamma-ray background whose brightness varies from region to region.
“Unfortunately gamma rays don’t have a label that would tell us where they came from,” Gruen said. “That’s why we need additional information to unravel their origin.”
That’s where DES comes in. With its 570-megapixel Dark Energy Camera, mounted on the Victor M. Blanco 4-meter Telescope at the Cerro Tololo Inter-American Observatory in Chile, it snaps images of hundreds of millions of galaxies. Their exact shapes tell researchers how the gravitational pull of matter bends light in the universe – an effect that shows itself as tiny distortions in galaxy images, known as weak gravitational lensing. Based on these data, the DES researchers create the most detailed maps yet of matter in the cosmos.
In the new study, the scientists superimposed the Fermi and DES maps, which revealed that the two aren’t independent. The unresolved gamma-ray background is more intense in regions with more matter and less intense in regions with less matter.
“The result itself is not surprising. We expect that there are more gamma ray producing processes in regions that contain more matter, and we’ve been predicting this correlation for a while,” said Nicolao Fornengo, one of Ammazzalorso’s supervisors in Turin. “But now we’ve succeeded in actually detecting this correlation for the first time, and we can use it to understand what causes the gamma ray background.”
Potential hint at dark matter
One of the most likely sources for the gamma-ray glow is very distant blazars – active galaxies with supermassive black holes at their centers. As the black holes swallow surrounding matter, they spew high-speed jets of plasma and gamma rays that, if the jets point at us, are detected by the Fermi spacecraft.
Blazars would be the simplest assumption, but the new data suggest that a simple population of blazars might not be enough to explain the observed correlation between gamma rays and mass distribution, the researchers said.
In fact, our models for emissions from blazars can fairly well explain the low-energy part of the correlation, but we see deviations for high-energy gamma rays,” Gruen said. “This can mean several things: It could indicate that we need to improve our models for blazars or that the gamma rays could come from other sources.”
One of these other sources could be dark matter. A leading theory predicts the mysterious stuff is made of weakly interacting massive particles, or WIMPs, which could annihilate each other in a flash of gamma rays when they collide. Gamma rays from certain matter-rich cosmic regions could therefore stem from these particle interactions.
The idea to look for gamma-ray signatures of annihilating WIMPs is not a new one. Over the past years, scientists have searched for them in various locations believed to contain a lot of dark matter, including the center of the Milky Way and the Milky Way’s companion galaxies. However, these searches haven’t produced identifiable dark matter signals yet. The new results could be used for additional searches that test the WIMP hypothesis.
Planning next steps
Although the probability that the measured correlation is just a random effect is only about one in a thousand, the researchers need more data for a conclusive analysis.
“These results, connecting for the first time our maps of gamma rays and matter, are very interesting and have a lot of potential, but at the moment the connection is still relatively weak, and one has to interpret the data carefully,” said KIPAC Director Risa Wechsler, who was not involved in the study.
One of the main limitations of the current analysis is the amount of available lensing data, Gruen said. “With data from 40 million galaxies, DES has already pushed this to a new level, and that’s why we were able to do the analysis in the first place. But we need even better measurements,” he said.
With its next data release, DES will provide lensing data for 100 million galaxies, and the future Legacy Survey of Space and Time (LSST) at the Vera Rubin Observatory will look at billions of galaxies in a much larger region of the sky.
“Our study demonstrates with actual data that we can use the correlation between the distributions of matter and gamma rays to learn more about what causes the gamma-ray background,” Fornengo said. “With more DES data, LSST coming online and other projects like the Euclid space telescope on the horizon, we’ll be able to go much deeper in our understanding of the potential sources.”
Then, the scientists might be able to tell if some of that gamma-ray glow stems from dark matter’s self-destruction.
DES is an international project with over 400 scientists from 25 institutions in 7 countries, who have come together to carry out the survey. Parts of the project were funded by DOE’s Office of Science and the National Science Foundation. NASA’s Fermi Gamma-ray Space Telescope is an international and multi-agency space observatory. The analysis used Fermi-LAT data that were publicly released by the international LAT collaboration.
Reference: “Detection of cross-correlation between gravitational lensing and gamma rays” by S. Ammazzalorso, D. Gruen, M. Regis, S. Camera, S. Ando, N. Fornengo, K. Bechtol, S. L. Bridle, A. Choi, T. F. Eifler, M. Gatti, N. MacCrann, Y. Omori, S. Samuroff, E. Sheldon, M. A. Troxel, J. Zuntz, M. Carrasco Kind, J. Annis, S. Avila, E. Bertin, D. Brooks, D. L. Burke, A. Carnero Rosell, J. Carretero, F. J. Castander, M. Costanzi, L. N. da Costa, J. De Vicente, S. Desai, H. T. Diehl, J. P. Dietrich, P. Doel, S. Everett, B. Flaugher, P. Fosalba, J. Garcia-Bellido, E. Gaztanaga, D. W. Gerdes, T. Giannantonio, D. A. Goldstein, R. A. Gruendl, G. Gutierrez, D. L. Hollowood, K. Honscheid, D. J. James, M. Jarvis, T. Jeltema, S. Kent, N. Kuropatkin, O. Lahav, T. S. Li, M. Lima, M. A. G. Maia, J. L. Marshall, P. Melchior, F. Menanteau, R. Miquel, R. L. C. Ogando, A. Palmese, A. A. Plazas, A. K. Romer, A. Roodman, E. S. Rykoff, C. Sanchez, E. Sanchez, V. Scarpine, S. Serrano, I. Sevilla-Noarbe, M. Smith, M. Soares-Santos, F. Sobreira, E. Suchyta, M. E. C. Swanson, G. Tarle, D. Thomas, V. Vikram, Y. Zhang, 31 July 2019, Cosmology and Nongalactic Astrophysics. | 0.911142 | 4.174438 |
A NASA mission has discovered an important process explaining the fate of energy contained in the turbulent magnetic fields surrounding the Earth.
The phenomenon, discovered by NASA's four-spacecraft Magnetospheric Multiscale (MMS) mission, is small but provides crucial insight into turbulent plasmas.
The Earth's magnetic field protects us from the solar wind, which is a stream of plasma coming from the Sun. Plasmas - streams of charged particles such as protons and electrons - fill much of the visible universe, so studying their properties can tell us a lot about space environments.
Intense periods of solar wind also cause 'magnetic storms' on Earth that disrupt GPS satellites and ground communications, making understanding its dynamics important.
The solar wind plasma becomes very turbulent where it interacts with the edges of the Earth's magnetic field, in the 'magnetosheath'. Turbulent plasmas are not well understood in physics, despite playing a fundamental role in environments, ranging from lab experiments to the Sun.
Now, researchers studying data from NASA's Magnetospheric Multiscale (MMS) mission at the edge of the Earth's magnetic field have discovered the ultimate fate of this turbulent energy and motion. The results of the team, which includes Imperial College London researcher Dr Jonathan Eastwood, are published today in Nature.
The answer revolves around a phenomenon known as magnetic reconnection, where energy from the magnetic field is transferred to the particles, creating hot jets of plasma. This dissipates the energy of the turbulence.
Magnetic reconnection is seen on large scales, and was predicted at smaller scales where it would dissipate energy as heat. However, very small-scale magnetic reconnection has never been observed until now, and several alternative mechanisms were also proposed to be the cause of the dissipation of turbulence.
The team analysed MMS data in the turbulent region and found reconnection occurring on the scale of electrons, the smallest scale observed to date. However, they found a key surprising difference in the process at this small scale compared to larger scales.
At larger scales, magnetic reconnection produces a 'jet' of charged particles called ions. This occurs for example in the Earth's magnetic field on the 'night side' of the Earth, facing away from the Sun, as part of the process that creates the Northern and Southern Lights. However, at the smallest scales, no ions jets have been observed.
Instead, the team determined that reconnection only affected the electrons in the plasma and created electron jets, which are very much faster than ion jets in large-scale reconnection.
Dr Eastwood, from the Department of Physics at Imperial, said: "Turbulence is one of the last great concepts in classical physics that we do not understand well, but we know it's important in space as it redistributes energy. With this observation, we can now make new theories or models that will help us understand observations of other places like the Sun's atmosphere and the magnetic environments of other planets."
The discovery confirms reconnection is happening on these small scales rather than some other process. However, the discovery also opens up many new questions, such as why the ions are not involved and whether this same process occurs in other plasmas. New theories and models now need to be developed to understand magnetic reconnection at these small scales. | 0.810724 | 4.117734 |
The NASA New Horizons probe just set a new interstellar exploration record, taking pictures from further out in space than ever before – it snapped the shots you see above some 6.12 billion kilometres (3.79 billion miles) away from Earth.
That’s about 6 million kilometres (3.7 million miles) further out than the Voyager 1 spacecraft was when it captured the famous Pale Blue Dot image of Earth back in 1990. Since Voyager 1’s cameras were turned off shortly after that shot was taken, the record has stood for the past 27 years.
The new record-breaking photos show two Kuiper Belt objects, 2012 HZ84 and 2012 HE85. As fuzzy as they are, they’re the closest look we’ve ever got at any objects inside this vast icy ring, which circles the Sun about 30 to 55 times further out than Earth.
“New Horizons has long been a mission of firsts – first to explore Pluto, first to explore the Kuiper Belt, fastest spacecraft ever launched,” says New Horizons Principal Investigator Alan Stern, from the Southwest Research Institute in Boulder, Colorado.
“And now, we’ve been able to make images farther from Earth than any spacecraft in history.”
In fact, New Horizons broke the record twice in quick succession, first snapping a shot of a group of distant stars called the Wishing Well, around 1,300 light-years away from our planet. That was followed up with the shots of the Kuiper Belt two hours later.
New Horizons first left Earth in 2006 with the aim of flying by Pluto, which it did in 2015, taking some dramatic photos along the way. Since then it’s been heading into the Kuiper Belt, and will carry out a flyby of Kuiper Belt object (KBO) 2014 MU69 in January 2019.
By that time 2014 MU69 should have a catchier name attached to it – NASA is asking for suggestions.
The probe continues to cover around 1.1 million kilometres or 700,000 miles of deep space every day, and is only the fifth man-made object in history – after Pioneer 10, Pioneer 11, Voyager 2, and Voyager 1 – to be on course to fly beyond the reaches of our Solar System.
As anyone who’s ever tried to keep a camera steady will know, taking pictures at that speed is an impressive feat.
Before we eventually lose touch with New Horizons, it’s hoped that it will tell us plenty more about the Kuiper Belt. The probe is measuring levels of plasma, dust, and gases as it travels, and will eventually take a look at more than 20 other KBOs.
New Horizons is going to get nudged out of hibernation again on the 4th of June. In the meantime, we can marvel at these record-breaking deep space photographs. | 0.814435 | 3.385846 |
Three times before the Cambrian period (545 mya), the entire earth has been buried in several kilometers of snow -- based on evidence including tropical glacial deposits and the cessation of carbonate production (which prefers to form in warmer waters) -- in a phenomenon known as Snowball Earth. But what causes these drastic glaciations to occur?Most theories have focused on internal forcing, but one new theory posits that external forcing -- supernovae and starbursts -- could be the culprit. These nebulae send large amounts of cosmic dusts particles (which reflect sunlight) and cosmic rays (which, depending on type, destroy the ozone or form reflective clouds) into our atmosphere, decreasing solar radiation hitting the ground and resulting in global cooling. Snow has a high albedo, which means it reflects sunlight away very well, so as snow begins to accumulate, a positive feedback cycle begins.
Encounters last 1–10 kyrs
Occur within 10 pc of the solar system approximately once per several hundred myrs
Catastrophic explosion of a heavy star (> 8 solar masses)
- Dark cloud
Encounters last 0.1–10 Myrs
Dense dark cloud of 2000/cc occurs once every billion years
High-density and low-temperature neutral gas; 1% cosmic dust by mass
Last ~100 Myrs
Occur every several ten myrs
Star-formation rate in a galaxy enhanced by interactions with nearby galaxies
At 4.6 billion years old, the earth has survived a few encounters with nebulae, and some of these encounters overlap with Snowball Earth events. Starburst events occurred 2.0-2.4 and 0.6-0.8 bya, which corresponds to Snowball Earths in the early Paleoproterozoic and the late Neoproterozoic. The authors also noticed that several large extinction events also correlated with supernovae and dark clouds; they believe that on top of wiping out tons of species, the nebulae could have sped up evolution by increasing rates of mutation.
Right now, this intriguing "Nebula Winter" theory has temporal correlation and an explanatory mechanism on its side, but more research is needed to confirm its validity. According to the authors, the next step is to look for geochemical evidence of supernovae, such as iridium, in sediments and rocks formed during the Snowball Earths.
Kataoka, R., Ebisuzaki, T., Miyahara, H., Nimura, T., Tomida, T., Sato, T., & Maruyama, S. (2013). The Nebula Winter: The united view of the snowball Earth, mass extinctions, and explosive evolution in the late Neoproterozoic and Cambrian periods. Gondwana Research. Available from: http://www.sciencedirect.com/science/article/pii/S1342937X13001597
Bonus information on Snowball Earths:
- When did they occur? A few times.
- Could a Snowball Earth have fueled photosynthesis by releasing peroxide? Read more here or here. | 0.885439 | 3.858305 |
Have you heard about comet 46P/Wirtanen? It has been zooming through the inner solar system, approaching Earth’s vicinity at a speed of about 6 miles per second (10 km/s). As it’s come nearer, the comet has brightened and should be brightest around December 16, when it passes closest to Earth, within 7.4 million miles (12 million km). Comet Wirtanen is the brightest comet in the night sky now; it’s the brightest comet of 2018. The comet sweeps closest to Earth just a few days after being closest to the sun on December 12. Closest approach to Earth happens on December 16 at 13:05 UTC (8:05 a.m. EST; translate UTC to your time).
Although bright enough, strictly speaking, to be visible to the eye now, this comet is not easily visible to the eye. Astronomers have captured it using telescopes and binoculars (see a collection of photos here). We heard from one experienced observer this weekend who said she glimpsed it – briefly, and through an 8-inch telescope – from the parking lot of a car dealership, in the middle of a city.
Yet comet 46P/Wirtanen is still best seen from a dark location. To get a look at it, use the chart in this post. Or check to see if your local astronomy club is hosting an event for observing comet 46P/Wirtanen. Or visit the Virtual Telescope Project for a free, online viewing of comet Wirtanen on December 17.
Want to try to spot the comet yourself, in a dark sky? Keep reading …
As of early December, observers around the world are reporting that Comet 46P/Wirtanen is, in theory, bright enough to be seen with the eye. The problem is that the dim light reflected from the comet is spread over a large cometary atmosphere, or coma.
So you’ll be looking for a large, diffuse, dim object.
The comet is moving in front of the stars from one night to the next. It appears in front of the same stars as seen from both the Northern Hemisphere and the Southern Hemisphere. But, as always, your orientation to these stars is different from different parts of Earth. Where should you look on any given date? See the charts below.
Or, try setting your specific location to this comet Wirtanen page at In-the-Sky.org.
You can also set your location at this site: TheSkyLive’s comet Wirtanen page.
Here’s another helpful article on how to see the comet, from SkyandTelescope.com.
Estimates of the comet’s brightness have varied, but it should now have a visual magnitude of around 3. If the comet were a point source, like a star, it would be of medium brightness! But its diffuse coma and the nearly full moon on December 16 will make observations challenging. On Sunday night, December 16, the moon is 65 percent illuminated.
If you do glimpse comet 46P/Wirtanen in December, here are a few details that might help you appreciate it.
Consider that the comet’s icy nucleus, or core, is less than a mile (just 1.2 km) wide. Meanwhile, its cometary atmosphere – or coma – is bigger, in an absolute sense, than the planet Jupiter.
When you see 46P/Wirtanen, consider the question of comet tails. Due to the orientation in space of Earth and Wirtanen when the comet is closest, the ion tail will be behind the comet, not visible from Earth’s perspective. So far, we haven’t seen much of a tail at all from this comet, but that could change. It might develop a slight curved tail in the coming days; if so, it’ll likely be easier to see in astrophotography than with the unaided eye.
Finally, if you are glimpsing the comet with optical aid, you might be able to discern this comet’s movement in front of the stars. Careful observations of the comet – in particular with a small telescope – should let you perceive its motion relative to the stars, over about a 30-minute period. The video below, from Tom Wildoner, shows you the comet’s movement.
Whether or not you see comet 46P/Wirtanen, it’ll be fun to contemplate this comet’s 2018 passage near the Earth and sun. According to astronomers at the University of Maryland, this passage of comet Wirtanen near the Earth (near by comet standards, that is) will be the 10th closest approach of a comet in modern times.
At its closest to us, the comet will be about 30 times the moon’s distance (7.1 million miles, or 11.5 million km).
The record for the closest observed comet – for all of recorded history – goes to D/1770 L1 Lexell, which came to less than six times the Earth-moon distance in June 1770.
Or, contrast Wirtanen’s closest appraoch – 30 times the moon’s distance, 7.1 million miles, or 11.5 million km – to another comet that swept relatively near us recently, 21P/Giacobini-Zinner, causing a brief outburst in this year’s Draconid meteor shower. Giacobini-Zinner swept closest to Earth on September 9-10, 2018, at 36 million miles (58 million km). That was the closest Giacobini-Zinner had come in 72 years!
So you see comets are elusive objects. They don’t come very close, usually, in any absolute sense. Still, this 2018 approach is a good one for comet Wirtanen.
And there is more …
Between December 6 and 12, 2018, comet 46P/Wirtanen enters an area of the sky where, as seen from our perspective, there is an orbiting ring of some 450 active geostationary satellites.
This belt of meteorological, television and other communication satellites orbits our planet at about 22,236 miles (35,786 km) above Earth’s equator. Because these satellites orbit our planet at the same speed that Earth rotates, geostationary satellites appear to be motionless, at a fixed position in the sky, thus explaining why the small satellite dishes on the roofs of our houses are pointing at a fixed position.
Because they orbit so high above Earth, these satellites are illuminated by the sun most of the time.
Observers using telescopes with a small motor that tracks astronomical objects in the sky, compensating for the Earth’s rotation, will perceive the slow motion of these satellites passing in front of the comet and stars. The view will be similar to the one seen on this video:
If the object appears to cross the field of view in the telescope fairly fast, you are likely looking at a satellite in low-Earth orbit. But if the satellite is moving slowly and remains visible several seconds through the telescope, you are probably seeing one of many geostationary satellites that will be visible in the path of comet Wirtanen from early to mid-December.
Sometimes, geostationary satellites may be visible in groups of three or more.
Can you confirm you are looking at a geostationary satellite at the eyepiece? Yes. If you are a using a computerized or tracking telescope, center the slow-moving object in the field of view. Then turn off the telescope or tracking function. If it’s a geostationary satellite, it will remain centered and now all the stars will appear to slowly drift as Earth rotates.
Keep in mind that you might have to re-align the telescope to continue observing the comet or other astronomical objects. Have fun!
Bottom line: Comet 46P/Wirtanen is due to pass closest to the sun on December 12, 2018, and closest to Earth just a few days later, on December 16. It’s theoretically visible to the eye now, but is large and diffuse … not easy to see. Charts, tips and other info here.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says. | 0.838488 | 3.389171 |
Our galaxy could have 100 billion brown dwarfs or more, according to work by an international team of astronomers, led by Koraljka Muzic from the University of Lisbon and Aleks Scholz from the University of St Andrews. On Thursday 6 July Scholz will present their survey of dense star clusters, where brown dwarfs are abundant, at the National Astronomy Meeting at the University of Hull.
Brown dwarfs are objects intermediate in mass between stars and planets, with masses too low to sustain stable hydrogen fusion in their core, the hallmark of stars like the Sun. After the initial discovery of brown dwarfs in 1995, scientists quickly realised that they are a natural by-product of processes that primarily lead to the formation of stars and planets.
All of the thousands of brown dwarfs found so far are relatively close to the Sun, the overwhelming majority within 1500 light years, simply because these objects are faint and therefore difficult to observe. Most of those detected are located in nearby star forming regions, which are all fairly small and have a low density of stars.
In 2006 the team began a new search for brown dwarfs, observing five nearby star forming regions. The Substellar Objects in Nearby Young Clusters (SONYC) survey included the star cluster NGC 1333, 1000 light years away in the constellation of Perseus. That object had about half as many brown dwarfs as stars, a higher proportion than seen before.
To establish whether NGC 1333 was unusual, in 2016 the team turned to another more distant star cluster, RCW 38, in the constellation of Vela. This has a high density of more massive stars, and very different conditions to other clusters.
RCW 38 is 5500 light years away, meaning that the brown dwarfs are both faint, and hard to pick out next to the brighter stars. To get a clear image, Scholz, Muzic and their collaborators used the NACO adaptive optics camera on the European Southern Observatory's Very Large Telescope, observing the cluster for a total of 3 hours, and combining this with earlier work.
The researchers found just as many brown dwarfs in RCW 38 - about half as many as there are stars - and realised that the environment where the stars form, whether stars are more or less massive, tightly packed or less crowded, has only a small effect on how brown dwarfs form.
Scholz says: "We've found a lot of brown dwarfs in these clusters. And whatever the cluster type, the brown dwarfs are really common. Brown dwarfs form alongside stars in clusters, so our work suggests there are a huge number of brown dwarfs out there."
From the SONYC survey, Scholz and team leader Koraljka Muzic, estimate that our galaxy, the Milky Way, has a minimum of between 25 and 100 billion brown dwarfs. There are many smaller, fainter brown dwarfs too, so this could be a significant underestimate, and the survey confirms these dim objects are ubiquitous. | 0.836922 | 3.920213 |
Another potentially Earth-like world has been found. Image Credit: NASA
Astronomers have identified a distant exoplanet with a size and orbit comparable to that of the Earth.
The planet, which is situated around 24,000 light years away, appears to have a mass somewhere between that of the Earth and Neptune and orbits its parent star - which is a mere 10% of the mass of the Sun - at a distance somewhere between that of the Earth and Venus.
This makes it a particularly rare find as very few extrasolar planets are such a close match.
The discovery was made using a technique known as gravitational microlensing.
"The combined gravity of the planet and its host star caused the light from a more distant background star to be magnified in a particular way," said study lead author Dr. Herrera Martin.
"We used telescopes distributed around the world to measure the light-bending effect."
"To have an idea of the rarity of the detection, the time it took to observe the magnification due to the host star was approximately five days, while the planet was detected only during a small five-hour distortion."
"After confirming this was indeed caused by another 'body' different from the star, and not an instrumental error, we proceeded to obtain the characteristics of the star-planet system."
Due to the relatively small mass of the parent star, this new 'Super-Earth' has an orbital period of 617 days, however in many other ways it has the potential to be remarkably similar to our own planet.
When NASA's upcoming James Webb Space Telescope finally launches, worlds like this one will no doubt prove a tantalizing target for further observation.
Source: SciTech Daily | Comments (3)
Similar stories based on this topic: | 0.90836 | 3.285514 |
While scientists keep a close watch on the myriad space rocks near Earth, they don’t yet have a solid plan on what to do if one appears headed on a collision course toward our planet.
Two new studies propose potential spacecraft missions that would collide with asteroids in an attempt to deflect them away from our planet. Such missions, some researchers say, may be among our best hopes to ward off asteroids that may pose a threat to Earth.
One concept from researchers in China involves deflecting an asteroid with a spacecraft propelled by solar sails, giant mirrors that fly through space via the force of sunlight reflecting off them. A possible target is the asteroid known as Apophis, named after the Egyptian god of darkness because of fears that it might crash into Earth.
The researchers noted that giving Apophis a tiny shove at a key moment in 2029 would help ensure that it would not approach Earth in 2036, the year that it is forecasted to come near. The scientists calculated that a solar sail could hurl a spacecraft fast enough at Apophis to potentially knock it off course. [Photos: Asteroids in Deep Space]
"The impact velocity can be as high as 100 kilometers per second (223,700 mph), which is much higher than the impact velocity of a regular spacecraft, which is about 30 kilometers per second (67,100 mph)," study lead author Shengping Gong at Tsinghua University in Beijing told SPACE.com.
Europe's asteroid smasher
Another potential plan, a European Space Agency mission called Don Quijote, would also seek to crash a spacecraft into an asteroid in an attempt to deflect it.
The mission would involve two probes. One would smash into its target asteroid at more than 30,000 mph (48,000 kph), while the other would orbit the asteroid six months beforehand to observe its behavior before and after impact.
However, Don Quijote or any other mission aiming to slam into an asteroidsto deflect it would need to analyze such collisions in greater detail than before thought, according to scientists at the Open University in England and their colleagues. [Video: Asteroid Collision Watch]
Instead of measuring only an asteroid's orbit before and after impact, researchers found that its diameter, reflectivity and surface roughness would also have a large effect on how it would react to a collision. As such, these details need to monitored closely as well, significantly altering such missions.
In addition to radio transmitters to help pin down an asteroid's orbit, these spacecraft would need to carry sophisticated imaging arrays, and possibly seismic sensors on the space rock to see if it would break apart upon impact.
"In order for the mission to succeed, you have to characterize the physical properties to distinguish effects from the deflection and effects from other non-gravitational perturbations," study lead author Stephen Wolters, an astronomer now at NASA's Jet Propulsion Laboratory in Pasadena, Calif., told SPACE.com.
Picking an asteroid target
The researchers do note that the asteroids they used in their calculations are not immediate threats.
The asteroid Apophis is expected to fly harmlessly by Earth on April 13, 2036, with only a 1-in-233,000 chance of hitting our planet, while neither of the two asteroids studied for the Don Quijote mission, designated 2002AT4 and 1989ML, is close to crossing Earth's orbit.
Although Apophis was picked for the study only as an example, "the results are universal" and could apply to other asteroids, Gong said.
"The idea for the mission was not to deflect a dangerous asteroid, but to deflect a safe one a little bit," Wolters said of his team's results. "This is practice so that we are prepared when there is a real danger. At the moment you might need a decade or more to prepare a real deflection mission. By having test missions, you cut down on that time, so you are prepared if you find an asteroid with fewer years until impact." | 0.833191 | 3.561218 |
Researchers find evidence for a new fundamental constant of the Sun
New research undertaken at Northumbria University, Newcastle shows that the sun's magnetic waves behave differently than currently believed.
Their findings have been reported in Nature Astronomy.
After examining data gathered over a 10-year period, the team from Northumbria's Department of Mathematics, Physics and Electrical Engineering found that magnetic waves in the sun's corona – its outermost layer of atmosphere – react to sound waves escaping from the inside of the sun.
These magnetic waves, known as Alfvénic waves, play a crucial role in transporting energy around the sun and the solar system. The waves were previously thought to originate at the sun's surface, where boiling hydrogen reaches temperatures of 6,000 degrees and churns the sun's magnetic field.
However, the researchers have found evidence that the magnetic waves also react – or are excited – higher in the atmosphere by sound waves leaking out from the inside of the sun.
The team discovered that the sound waves leave a distinctive marker on the magnetic waves. The presence of this marker means that the sun's entire corona is shaking in a collective manner in response to the sound waves. This is causing it to vibrate over a very clear range of frequencies.
This newly-discovered marker is found throughout the corona and was consistently present over the 10-year time-span examined. This suggests that it is a fundamental constant of the sun – and could potentially be a fundamental constant of other stars.
The findings could therefore have significant implications for our current ideas about how magnetic energy is transferred and used in stellar atmospheres.
Dr. Richard Morton, the lead author of the report and a senior lecturer at Northumbria University, said: "The discovery of such a distinctive marker – potentially a new constant of the sun – is very exciting. We have previously always thought that the magnetic waves were excited by the hydrogen at the surface, but now we have shown that they are excited by these sound waves. This could lead to a new way to examine and classify the behaviour of all stars under this unique signature. Now we know the signature is there, we can go looking for it on other stars.
"The sun's corona is over one hundred times hotter than its surface and energy stemming from the Alfvénic waves is believed to be responsible for heating the corona to a temperature of around one million degrees. The Alfvénic waves are also responsible for heating and accelerating powerful solar wind from the sun which travels through the solar system. These winds travel at speeds of around a million miles per hour. They also affect the atmosphere of stars and planets, impacting on their own magnetic fields, and cause phenomena such as aurora."
Dr. Morton added: "Our evidence shows that the sun's internal acoustic oscillations play a significant role in exciting the magnetic Alfvénic waves. This can give the waves different properties and suggests that they are more susceptible to an instability, which could lead to hotter and faster solar winds."
Dr. Morton and Professor McLaughlin are currently working with NASA to analyse images of the sun which were taken by NASA's High-Resolution Coronal Imager, Hi-C.
Their paper, "A basal contribution from p-modes to the Alfvenic wave flux in the sun's corona" is published in Nature Astronomy. | 0.801634 | 3.855213 |
Among the planets of the Solar System, the gas giant Jupiter is considered to be king in terms of the radius. However, among exoplanets, he was not honored to take a leading position. Then which extrasolar planet is considered the largest?
Let's move a distance of 337 light years from the solar system. We are in the beautiful constellation of the Southern Hemisphere Mucha. This is a small constellation in which 60 visible stars are located. We are interested in a single white and blue star HD 100546.
It is interesting in that it contains a protoplanetary disk, where in 2013 they found an exoplanet HD 100546 b. Before you is the largest exoplanet of the Universe among worlds known to science. It was discovered using the Very Large Telescope (Chile).
Comparative dimensions of exoplanets HD 100546 b. For comparison, the bottom left is Jupiter HD 100546 b belongs to the class of gas supergiants. Jupiter is 20 times more in mass, and 6.9 times larger in radius. And the planet continues to grow in size. The remoteness of the world from the native star is 6 times the distance of the Earth-Sun.
It is surprising that a full-fledged planet is located in a protoplanetary disk and is still surrounded by building material for the formation of future planets. The age of the star HD 100546 reaches only 10 million years. How did the exoplanet manage to form? The answer so far can not be found.
It is also interesting that because of its gigantic size, HD 100546 b approaches the category of brown dwarfs. We are talking about substellar objects, whose mass is 12.57-80.35 times the size of Jupiter. Researchers will continue to study the largest exoplanet, and perhaps one day they will change its status from “planet” to “brown dwarf”. | 0.848215 | 3.157669 |
A star has been discovered orbiting tightly round the massive black hole at the center of our Milky Way galaxy, making its circuit in just eleven and a half years.
The star, known as S0-102, could help astronomers discover whether Albert Einstein was right in his fundamental prediction of how black holes warp space and time.
It’s the second with a short orbit to be found in the region: S0-2 orbits in 16 years. Most have orbits of 60 years or longer.
“I’m extremely pleased to find two stars that orbit our galaxy’s supermassive black hole in much less than a human lifetime,” says Andrea Ghez of UCLA.
“It is the tango of S0-102 and S0-2 that will reveal the true geometry of space and time near a black hole for the first time. This measurement cannot be done with one star alone.”
Einstein’s theory of general relativity predicts that mass not only slows down the flow of time but also stretches or shrinks distances.
“The exciting thing about seeing stars go through their complete orbit is not only that you can prove that a black hole exists but you have the first opportunity to test fundamental physics using the motions of these stars,” says Ghez.
“Showing that it goes around in an ellipse provides the mass of the supermassive black hole, but if we can improve the precision of the measurements, we can see deviations from a perfect ellipse – which is the signature of general relativity.”
As the stars come to their closest approach – which for S0-2 will be in 2018 – their motion will be affected by the curvature of spacetime, and the light traveling from the stars to us will be distorted.
“The fact that we can find stars that are so close to the black hole is phenomenal,” says Ghez.
“Now it’s a whole new ballgame, in terms of the kinds of experiments we can do to understand how black holes grow over time, the role supermassive black holes play in the center of galaxies, and whether Einstein’s theory of general relativity is valid near a black hole, where this theory has never been tested before. It’s exciting to now have a means to open up this window.” | 0.83371 | 3.928786 |
My last post raised the specter of a geomagnetic storm so strong it would black out electric power across continent-scale regions for months or years, triggering an economic and humanitarian disaster.
How likely is that? One relevant source of knowledge is the historical record of geomagnetic disturbances, which is what this post considers. In approaching the geomagnetic storm issue, I had read some alarming statements to the effect that global society is overdue for the geomagnetic "Big One." So I was surprised to find reassurance in the past. In my view, the most worrying extrapolations from the historical record do not properly represent it.
I hasten to emphasize that this historical analysis is only part of the overall geomagnetic storm risk assessment. Many uncertainties should leave us uneasy, from our incomplete understanding of the sun to the historically novel reliance of today's grid operators on satellites that are themselves vulnerable to space weather. And since the scientific record stretches back only 30–150 years (depending on the indicator) and big storms happen about once a decade, the sample is too small to support sure extrapolations of extremes.
Nevertheless the historical record and claims based on it are the focus in this and the next post. I'll examine four (kinds of) extrapolations that have been made from the record: from the last "Big One," the Carrington event of 1859; from the July 2012 coronal mass ejection (CME) that might have caused a storm as large if it had hit Earth; a more complex extrapolation in Kappenman (2010); and the formal statistical extrapolation of Riley (2012). I'll save the last for the next post.
The Carrington event
A series of CMEs starting in late August 1859 caused an extraordinary, global geomagnetic storm. It came to be named for astronomer Richard Carrington, who linked the events on earth to an intense solar flare he had observed on the sun hours before. The Carrington event produced spectacular auroras as far south, in the northern hemisphere, as San Salvador and as far north, in the southern hemisphere, as Santiago. Vivid reports were made from around the world. Here is one from the Washington Territory of the US:
At 8 P.M. Aug. 28, 1859, a diffused light, without definite form, was observed a little east of north, covering about one-fourth of the heavens, which gradually increased to the west, sending across from east to west an arch of a whitish color, the arch itself being much brighter than the circumjacent light…At 9h25m P.M. strongly marked rays became visible, which rising from the horizon converged to a point on the arch a little south of the zenith, and in this position remained visible about one hour. The rays in the northwest were of a pink color, those in the southeast were purple, alternately brightening and fading to a whitish color. At midnight, all disappeared except the arch, and at intervals undulating flashes of light appeared not visible longer than three seconds. Occasionally streamers shot up from the horizon, the lower part disappearing before the upper part had reached the zenith. Sometimes these streamers were broad at the horizon, and came to a point near the zenith, and sometimes the reverse.
The storm hardly harmed human societies: it temporarily disrupted telegraph communications. Yet because of its apparent strength, the Carrington event of 1859 occupies a special place in the minds of those concerned about geomagnetic storms. It is the 1906 San Francisco earthquake, whose repetition is statistically inevitable. And next time global society may be much more vulnerable.
A critical question in assessing that vulnerability is: how much bigger was Carrington than the geomagnetic storms that have hit since the development of modern grids, which civilization has shrugged off? The paucity of high-quality scientific measurements from 1859 impedes comparisons (some magnetometers were operating, but went off scale). But scientists have made the most of the available data. The table below compares the Carrington event to more recent storms on several measures.
|Storm strength indicator||Carrington event, 1859||Modern comparators||Sources|
|Lowest magnetic latitude where aurora visible||23°||29°, Mar. 1989||Cliver and Svalgaard (2004), p. 417; Silverman (2006), p. 141|
|Associated solar flare intensity (soft X-ray emissions)||0.0045 W/m2||0.0035 W/m2, Nov. 2003||Cliver and Dietrich (2013), pp. 2–3|
|Transit time of CME to earth||17.6 h||14.6 h, Aug. 1972; 20.3 h, Oct. 2003||Cliver and Svalgaard (2004), Table III|
|Dst (low-latitude magnetic field depression)||–850 nT||–589 nT, Mar. 1989||Siscoe, Crooker, and Clauer (2006); Kyoto University|
|W/m2 = watts/square meter; h = hours; nT = nanotesla|
Perhaps the most important comparison is in the last row. The storm-time disturbance (Dst) index measures the change in Earth's magnetic field, as measured at four low-latitude observatories; it roughly proxies the overall geomagnetic impact of a storm. The Dst has only been compiled since 1957; scientists estimate that the Carrington event would have registered at roughly –850 nanotesla. As shown in the table, the biggest value on record is –589 nT; it occurred on March 14, 1989, which is when the Québec grid collapsed for some hours and permanently lost two transformers. (Last Tuesday a pretty-big CME drove the Dst to –195, the largest reading in 10 years.) This and the other comparisons in the table suggest that the Carrington storm was, conservatively, no more than twice as strong as modern events.
The July 2012 near-miss
Another important comparator is the major CME of July 23, 2012. That CME missed Earth because it left from what was then the far side of the sun. However, the NASA probe STEREO-A was travelling along earth’s orbit about 4 months ahead of the planet, and lay in the CME’s path, while STEREO-B, trailing four months behind earth, was also positioned to observe. The twin probes produced the best measurements ever of a Carrington-class solar event (Baker et al. 2013). Since the sun rotates about its axis in less than a month, had the CME come a couple of weeks sooner or later, it would have smashed into our planet. Two numbers convey the power of the near-miss CME. First is its transit time to earth orbit: at just under 18 hours, almost exactly the same as in the Carrington event. A slower CME on July 19 appears to have cleared the interplanetary medium of solar plasma, resulting in minimal slowdown of the big CME on July 23. The second number is the strength of the component of the CME’s magnetic field running parallel to earth’s. When a CME hits Earth, it strews the most magnetic chaos if its field parallels Earth’s (meaning that both point south); then it is like slamming together two magnetized toy trains the way they don’t want to go. The southward component of the magnetic field of the great July 2012 CME peaked at 50 nT. Here, however, “south” means perpendicular to Earth’s orbital plane. Since Earth’s spin axis is tilted 23.5° and its magnetic poles deviate from the spin poles by about another 10°, the southerly magnetic force of the near-miss CME, had it hit Earth, could have been more or less than 50 nT, depending on the exact time of day and year. Baker et al. (2013, p. 590) estimate the worst case as 70 nT south, relative to earth’s magnetic orientation.
For comparison, the graph below shows the north-south component of the interplanetary magnetic field near earth since 1963, where north and south are also defined by the orientation of earth’s magnetic poles. Unfortunately, data are missing for the largest storm in the time range, the one of March 1989. The graph does reveal a large northerly spike in 1972, which explains why that year’s great CME caused minimal disruption despite the record speed noted in the table above. Also shown are large southerly magnetic forces in storms of 1982 and 2003, the latter reaching 50 nT.
Given the near-miss CME’s speed, its magnetic field, and its density, how big a storm could it have caused had it hit earth? Baker et al. (2013) estimate that it would have rated between –480 and –1182 on the Dst index, depending on the CME’s magnetic orientation relative to Earth’s at collision. Comparing the high value to the modern record of –589 again points to a benchmark worst-case storm as being twice as strong as anything experienced since the construction of modern grids. In a companion paper, the same team of scientists ran computer simulations to develop a more sophisticated understanding of what would have happened if earth had been in STEREO-A’s place on July 23. Their results do not point clearly to a counterfactual catastrophe. “Had the 23 July CME hit Earth, there is a possibility that it could have produced comparable or slightly larger geomagnetically induced electric fields to those produced by previously observed Earth directed events such as the March 1989 storm or the Halloween 2003 storms.”
Kappenman's factor of 10
In contrast, the prominent analyst John Kappenman has favored a factor of 10 to characterize the likely 100-year storm relative to the strongest recent storms. Recognizing that this contrast with my interpretation of the evidence begs explanation, I investigated the basis for the factor of 10. It appears to arise as the ratio of two numbers. One represents the worst disruption that geomagnetic storms have wrought in the modern age, meaning, again, the Québec blackout in March 1989. As Kappenman points out, just as the Richter scale doesn't tell you everything about the destructive force of an earthquake in any given spot – local geology, distance from the epicenter, and building construction quality matter too – the Dst index doesn't tell you everything about the capacity of a storm to induce electrical surges in any given place. What matters is not the total perturbation in the magnetic field, globally averaged, but the rate of magnetic field change from minute to minute along power lines of concern. By the laws of electromagnetism, a changing magnetic field induces a voltage; and the faster the change, the bigger the voltage. In Québec in 1989, the rate of magnetic field change peaked at 479 nT/min (nanotesla per minute) according to Kappenman.
While I did not find a clear citation of source for this statistic, it looks highly plausible. The graph below, based on my own extracts of magnetic observatory data, shows the maximum horizontal field changes at 58 stations on that day in 1989, based on measurements taken every minute, on the minute. Each 3-letter code represents an observatory; e.g., FRD is Fredericksburg, VA, and BFE is Brorfelde, Denmark.
Ottawa (OTT, in red) recorded a peak change of 556 nT/min, between 9:50 and 9:51pm universal time, which is compatible with Kappenman's 479 for nearby Québec. Brorfelde recorded the highest value, 1994 nT/min.
The other number in Kappenman's factor-of-10 ratio represents the highest estimate we have of any per-minute magnetic field change before World War II, at least at a latitude low enough to concern Europe or North America. It comes from Karlstad, in southern Sweden, during the storm of May 13–15, 1921. The rate of change of the magnetic field was not measured there, but the electric field induced in a telegraph line was reportedly estimated at 20 volts/kilometer (V/km). Calibrating to modern observations, Kappenman calculates, “the 20 V/km observation…suggests the possibility that the disturbance intensity approached a level of 5000 nT/min.” Elsewhere Kappenman suggests 4800 nT/min. And 4800/479 is just about 10. That is, the worst case on record looks to be 10 times as bad as what caused the Québec blackout.
I have two doubts about this ratio. First, the top number appears to have been unintentionally increased by a scholarly game of telephone. As a source for the 20 V/km observation, Kappenman cites – and correctly represents – a 1992 conference paper by Elovaara et al., who write, “The earth surface potentials produced are typically characterized by the value 1 V/km, but in extreme cases much higher values has been recorded like 20 V/km in a wire communication system in Sweden in May 1922 [sic].” No source is given there; but Jarmo Elovaara pointed me to Sanders (1961) as likely. Indeed, there we read, “In May, 1921, during an outstanding magnetic storm, the largest earth-current voltages measured on wirelines in Sweden ranged from 6.3 to 20 v/km.” The cited source for that range is the “Earth Currents” article of the 1943 Encyclopedia Britannica, which states: “In May 1921, during an outstanding magnetic storm, Stenquist calculated from the fusing of some copper wires and the non-fusing of others that the largest earth current voltage in Sweden lay between 6.3 and 20 volts per kilometre.” “Stenquist” is David Stenquist, a Swedish telegraph engineer who in 1925 published Étude des Courants Telluriques (Study of Earth Currents). The pertinent passage thereof comes on page 54:
Nevertheless I tried to calculate the largest value of telluric [earth] currents. Until now, standard opinion was that the largest potential differences in the earth because of telluric currents are two volts per kilometer. During the nights of May 13–14 and 14–15, this value was greatly exceeded. In many cases the currents were so strong in the lines of copper (3 mm [millimeters]), the conduits melted, i.e. the current exceeded 2.5 amps. Because the copper wire just mentioned had a resistance of 2.5 ohms per kilometer, we get a potential difference of 6.3 volts per kilometer. In contrast, the [fusion tubes?] placed on the iron lines (4 mm) did not melt. These iron lines have a resistance of 8 ohms per kilometer. So it is known that 20 volts did not occur. With a large enough security to speak, a difference of 10 volts per kilometer was found.
Stenquist believed the electric force field reached 10 V/km but explicitly rejected 20. Yet through the chain of citations, “20 volts n’ont pas été dé-passés” became “higher values has been recorded like 20 V/km.” Using Kappenman’s rule of thumb, Stenquist’s 10 V/km electrical force field suggests peaks of 2500 rather than 5000 nT/min of magnetic change on that dark and geomagnetically stormy night in Karlstad.
The second concern I have about the estimated ratio of 10 between magnetic fluctuations in the distant and recent past is that it appears to compare apples to oranges—an isolated, global peak value in one storm to a wide-area value in another. As we have already seen, the highest value observed in 1989 was not the 479 Kappenman uses to represent that storm but 1994 nT/min, in Brorfelde. And back in July 13–14, 1982, the Lovo observatory, at the same latitude as Karlstad, experienced 2688 nT/min according to my calculations from the public data. Both instances were isolated: most observatories of comparable latitude reported much lower peaks. It is therefore not clear that the 1921 storm, with its isolated observation of 2500 nT/min, exceeded those of the 1980s at all, let alone by a factor of 10. Maximum magnetic changes and voltages may have been the same.
While there is apparently no evidence that fluctuations as great as 4800 nT/min have happened over large areas, Kappenman's simulated 100-year storm scenario assumes that extremes of this order would occur across the US in a 5-degree band centered on 50° N geomagnetic latitude (an area 350 miles wide north-south, 3,000 long east-west) – 4800 nT/min east of the Mississippi and 2400 nT/min to the west. The associated estimate that a 100-year storm would put 365 high-voltage transformers at risk of permanent damage, out of some 2,146 in service, affect regions home to 130 million people, and reduce economic output by trillions of dollars, entered an oft-cited National Research Council conference report. Yet to me, this seems like a highly unrepresentative extrapolation from history.
I found one other independent review of the Kappenman analysis. It was commissioned in 2011 by the US Department of Homeland Security from JASON, a group of scientists that advises the government on issues at the intersection of science and security. The JASON report concludes: "Because mitigation has not been widely applied to the U.S. electric grid, severe damage is a possibility, but a rigorous risk assessment has not been done. We are not convinced that the worst-case scenario of [Kappenman] is plausible. Nor is the analysis it is based on, using proprietary algorithms, suitable for deciding national policy....[W]e are unlikely to experience geomagnetic storms an order-of-magnitude more intense than those observed to date."
Despite some spectacular reports from 1859 Carrington event and some equally spectacular scenario forecasts, to this point in our inquiry, the historical record appears surprisingly reassuring. There is little suggestion that the Carrington event – or any other in the last two centuries – was more than twice as strong as the biggest storms of recent decades, in 1982, 1989, and 2003. And civilization shrugged those off, with only a few high-voltage transformers taken out of commission. This does not prove geomagnetic storms pose no global catastrophic risk; like the JASON group, I don't feel we can rule that out. But it does lead us to more focussed questions: What are the risks posed by a doubling of storm strength relative to recent experience? Under what assumptions would the effects be extremely disproportionate to the increase in magnetic disruption? What steps could be taken to change that? In fact, I don't feel that I have satisfactory answers to those questions. The area appears under-researched, and that may point to an opportunity for philanthropy. But I get ahead of myself. In the next post, I will make a final approach on the historical record, this one more systematic and statistical. I think it's important but it will not change the conclusion much. | 0.824363 | 3.483336 |
Fr.: raie D
One of the pair of yellow lines in emission spectra of neutral sodium (Na I). D1 has a wavelength of 5895.94 Å and D2 is 5889.97 Å. This sodium doublet is one of the strongest absorption features in the spectra of late-type stars.
Labelled D in a sequence of alphabetical letters first used by Joseph von Fraunhofer to designate spectral features in the solar spectrum, → Fraunhofer line.
Fr.: anneau D
Fr.: paradoxe de d'Alembert
A hydrodynamical paradox arising from the neglect of → viscosity in the → steady flow of a fluid around a submerged solid body. According to this paradox, the submerged body would offer no resistance to the flow of an → inviscid fluid and the pressure on the surface of the body would be symmetrically distributed about the body. This paradox may be traced to the neglect of the viscous forces, which are indirectly responsible for fluid resistance by modifying the velocity field close to a solid body (Meteorology Glossary, American Meteorological Society).
Fr.: principe de d'Alembert
The statement that a moving body can be brought to a → static equilibrium by applying an imaginary inertia force of the same magnitude as that of the accelerating force but in the opposite direction. More specifically, when a body of mass m is moving with a uniform acceleration a under the action of an external force F, we can write: F = m . a, according to Newton's second law. This equation can also be written as: F - ma = 0. Therefore, by applying the force -ma, the body will be considered in equilibrium as the sum of all forces acting on it is zero. Such equilibrium is called → dynamic equilibrium. Owing to this principle, dynamical problems can be treated as if they were statical.
Named after the French mathematician and philosopher Jean le Rond d'Alembert (1717-1783), who introduced the principle in his Traité de dynamique (1743).
Fr.: principe d'Alembert-Lagrange
A second order, → partial differential operator in space-time, defined as: ▫2 = ∂2/∂x2 + ∂2/∂y2 + ∂2/∂z2 - (1/c2)∂2/∂t2, or ▫2 = ∇2 - (1/c2)(∂2/∂t2), where ∇2 is the → Laplacian and c is the → speed of light. This operator is the square of the → four-dimensional operator ▫, which is Lorentz invariant.
D-type ionization front
pišân-e yoneš-e gune-ye D
Fr.: front d'ionisation de type D
An → ionization front of → H II regions whose expansion speed is comparable to the → sound speed in the gas (~ 10 km/sec for hydrogen at 104 K). A D-type ionization front results from → R-type ionization front when its propagation speed decreases as the volume of gas ahead of the ionization front grows. If front velocity is equal to a lower limit (C12 / 2C2, where C1 and C2 are the sound speed ahead and behind the front respectively), the front is called D critical.
Fr.: raie D3
D3, because of confusion with the sodium → D lines. When Joseph N. Lockyer first observed this line in the solar spectrum at the eclipse of 1868, helium was not yet isolated on Earth. Initially, this line was thought to be the third member of the D1 and D2 line family of sodium which lie in the same yellow part of the spectrum; → line.
DA white dwarf
sefid kutule-ye DA
Fr.: naine blanche DA
Fr.: minimum de Dalton
Named after John Dalton (1766-1844), British meteorologist; → minimum.
Of an oscillating system, the progressive decrease with time in the amplitude of the oscillation, due to friction (internal or external) or other resistance.
M.E. damp "black damp, a poison gas occurring in a mine," from Mid.Du. or Mid. Low German; akin to O.H.G. damph "vapor."
Mirâyi, noun from mirâ "getting extinguished, going out, expiring, dying," from mordan, present tense stem mir- "to die," Mid.Pers. murdan "to die," O.Pers. mrt- "to die," amriyta "dies," martiya- "(mortal) man" (Mod.Pers. mard "man"), Av. mərəta- "died," Skt. mar- "to die," mrti- "death;" PIE base *mor-/*mr- "to die." Cognates in other IE languages: Gk. emorten "died," ambrotos "immortal," L. morior "I die," mortuus "dead" (Fr. mourir "to die," mort "dead"), Arm. merani- "to die," O.C.S. mrutvu "dead," O.Ir. marb, Welsh marw "died," O.E. morþ "murder," Lith. mirtis "man."
1) vašt (#); 2) vaštan (#), vaštidan
Fr.: 1) danse; 2) danser
1a) A successive group of rhythmical steps or bodily motions, or both,
usually executed to music.
M.E. da(u)ncen "to dance," from O.Fr. dancier of unknown origin, perhaps related to O.H.G. *dansjan "to lead (someone) to a dance."
Vašt, variant of gašt, gardidan, gel, gelidan "to turn," → revolve, cf. Eastern Gilâni gilâr "dance."
vaštâr, vaštande, vaštgar
Fr.: danseur, danseuse
1) A person who dances.
Vaštâr, from vašt "dnace," + agent noun suffix -âr, as in parastâr, padidâr; vaštande, vaštgar with agent noun suffixes, -ande and -gar, → -or.
1) Liability or exposure to harm or injury; risk; peril.
M.E. daunger, from O.Fr. dangier "power, power to harm, authority, control," alteration of dongier, from V.L. *dominarium "power of a lord," from L. dominus "lord, master," → domain.
Xatar "danger," loan from Ar.
Fr.: astrolabe de Danjon
A modern unportable astrolabe which is used for high precision measuring of stellar and geographical coordinates. The instrument uses the simultaneous observations of two images of the same star, one of the images formed directly by the lower face of a prism and the other by the light rays reflected first from a mercury bath and then by the upper face of the prism. The images coincide when the zenithal distance of the star attains a prefixed value (Gauss method of equal altitudes, → almucantar). Apart from astrometry, the Danjon astrolabe was used for studying the Earth's rotation and is currently used for solar radius measurements.
After André Danjon (1890-1967), French astronomer, who developed the instrument at the Strasbourg Observatory before the Second World War and at the Paris Observatory in 1948. The concept of prism astrolabe was initially invented by the French Auguste Claude (1858-1938) around 1900 and was later modified in collaboration with Ludovic Driencourt (1861-1940); → astrolabe.
Fr.: échelle de Danjon
A scale to evaluate as exactly as possible the darkening degree of a total → lunar eclipse. The five steps of the scale run from 0 (extremely dark, invisible Moon) to 4 (extremely bright, the eclipse having a very weak effect on the Moon's visibility). The darkening at a lunar eclipse is determined to a great extent by the transparency of the terrestrial atmosphere, which is affected by clouds and the dust from the volcanic eruptions (M.S.: SDE).
1) daršidan; 2) darše
Fr.: 1) oser; 2) défi
1) To be courageous enough to try to do something.
M.E. durren, from O.E. durran "be bold enough, have courage" (to do something); cf. O.Norse dearr, O.H.G. giturran, Gothic gadaursan, from PIE root *dhers- "bold" source also of O.Pers. darš-, as below.
Daršidan, from O.Pers. darš- "to dare," Av. darš- (prefixed *upa- in upadarəš- "to dare"); cf. Khotanese darv- "to dare;" Baluci durrit/durr- "to take courage;" Skt. dhars "to venture;" Gk. thrasus "bold;" Goth. ga-daursan "to venture;" E. "to dare;" PIE *dhers- "to attack, venture, dare" (Cheung 2007).
Taking or willing to take risks; audaciousness.
Fr.: sombre, obscur, noir
Having very little or no light.
M.E. derk, O.E. deorc, from P.Gmc. *derkaz.
Târik, Mid.Pers. târig "dark," târ "darkness," Av. taθra- "darkness," taθrya- "dark," cf. Skt. támisrâ- "darkness, dark night," L. tenebrae "darkness," Hittite taš(u)uant- "blind," O.H.G. demar "twilight."
niyâveš bé târiki
Fr.: adaptation à l'obscurité
The automatic adjustment of the iris and retina of the eye to allow maximum vision in the dark, following exposure of the eye to a relatively brighter illumination. | 0.820774 | 3.747289 |
As you’re no doubt aware, the universe is an incredibly complicated entity. This means there’s a lot for you to learn. But don’t fret; we’ve got everything you need to know right here. To help you out, we’ve arranged each of the below sections in no particular order, with headers so you can dip in and out of them quickly depending on what you need to know. Happy revising!
Spherical aberrations, should you want to know, occur due to the curvature of a lens or mirror and it is most pronounced with lenses (or mirrors) of large diameters. The effect can be minimised by making both lens surfaces contribute equally to the ray deviations.
The event horizon
The event horizon is the distance up to which nothing can escape from a black hole. Eerie or what? The phenomenon occurs when the gravitational field around a black hole is so high that nothing — including light — can escape. Unless of course, it is a certain distance away.
The lens equation
When using the lens equation, you should remember that where f is the focal length, u is the object distance and v is the image distance (i.e. distance from the lens). It’s also important to consider what sign each term has. For a divergent lens f is negative, and if the image appears on the same side of the lens as the object, then v is negative (in this case one would obtain a virtual image).
All you need to know about charge couple devices (CCDs)
The quantum efficiency of a typical CCD is ~75 per cent. This quantum efficiency is the ratio of the number of photons incident on the device to the number of photons detected. Photographic film usually has a quantum efficiency of ~5%.
A charge couple device is a microchip that converts a light signal into a digital format. They act as a replacement for photographic film, and are wafer thin chips divided into individual picture elements called pixels. There are a handful of advantages over traditional photographic film; namely, CCDs are more efficient, and they can detect wavelengths beyond those of visible light, etc.
An Airy disc is the name given to the effect of a light passing through a circular aperture, which is analogous to that of it passing through a double slit, in that an interference pattern is produced whereby the diffracted waves (of light) interfere with one another and produce a series of light and dark rings (or fringes for the double slit)
Wien’s Displacement Law
Wien’s Displacement Law demonstrates that the peak wavelength is inversely proportional to the temperature in Kelvin.
The Doppler Effect
The Doppler Effect is the shift in wavelength of light (or sound), due to relative movement of source or observer. In astronomy, if a star and the Earth are moving towards one another, the wavelengths are shortened (moved to the blue end of the spectrum), so they are blue shifted. When they are moving away from one another, the wavelengths are lengthened (towards the red end), so they are red shifted.
Hubble’s law is the name given to the statement in astronomy that galaxies move away from each other, and that the velocity with which they recede is proportional to their distance. To put a long story short, we can thank Hubble’s Law and scientists’ extrapolations for the Big Bang Theory. Go science!
As far as your exams are concerned, you should know that where v is the recession velocity in kilometres per second H is Hubble’s constant, which has a modern value of 73 kilometres per second per megaparsec. Edwin Hubble determined this relationship by plotting the recession velocities of galaxies against their distance. This is a linear relationship, showing that the further away the galaxy, the faster it is moving away. The Hubble constant is the gradient of this relationship. | 0.845892 | 3.692312 |
40,000 years ago a star exploded. This is the result.
This is the supernova remnant Simeis 147, sometimes known as the Spaghetti Nebula. It spans about 3 degrees of sky on the Auriga/Taurus border, a diameter of six full Moons. The bright star Elnath is at the bottom of the frame, which is easily visible to the naked eye.
These star charts, generated using World Wide Telescope, show the location of Simeis 147 in the sky.
Orion is sinking out of sight from the UK at this time of year but Auriga is still visible to the west as it gets dark, just above Venus.
The star chart above was generated using the free software Stellarium.
The bright red filaments of Simeis 147 are largely composed of glowing hydrogen, heated as material expelled by the explosion crashes into its surroundings. Over the next few thousand years it will continue to expand and dim, eventually fading into the background. This inverted monochrome image, taken through a hydrogen-alpha filter, shows the structure of the nebula more clearly.
(No telescope was used to take these images, just a short telephoto lens, in order to fit it all in the field of view. The lens and camera ride on a lightweight motorised star tracker powered by AA batteries. Total exposure time was about 35 minutes for the colour starfield and 50 minutes for the hydrogen-alpha. The hydrogen alpha data was then blended into the red channel of the colour image to produce the final version.)
(Amateurs have taken far better images of Simeis 147 than the one above. This is the best I could find, a spectacular 47 hour telescope mosaic by Franco Sgueglia & Francesco Sferlazza. The blue filaments are composed of glowing ionised oxygen.)
40,000 years ago, when light from the supernova first reached Earth, our ancestors would have certainly noticed. For a few months it would have been the brightest thing in the sky, after the Sun and Moon and perhaps Venus. In the dark skies of the neolithic, darker than all but the most remote locations today, it's sudden appearance would have been dramatic and spectacular. Unfortunately we'll never know what they made of it as writing would not be developed for another 30,000 years.
But we do have accounts of more recent supernova events. Kepler’s Nova of 1604 was clearly visible to the naked eye, and in 1987 a star exploded in the Large Magellanic Cloud, a nearby satellite galaxy of the Milky Way. The Hubble Space Telescope tracked its evolution over several years.
It’s difficult to convey just how violent and extreme an event a supernova is. Perhaps the easiest way is to talk about about Death Stars.
Alderaan appears to be a similar size to the Earth. Certainly it was inhabited by suspiciously human-like inhabitants, who appear to be comfortable in Earth gravity.
To completely destroy a planet it’s necessary to overcome the force of gravity holding it together. Earth’s gravitational binding energy can be calculated, it comes to 2.49 x 1032 Joules in scientific notation, or 249,000,000,000,000,000,000,000,000,000,000 Joules in longhand. That’s a lot of energy, as much as our Sun puts out in a week. (A single Joule is enough energy to lift a tomato a metre.)
The energy output of a typical type II supernova, caused by the collapse of a massive star, is 1.00 x 1046 Joules. The same as 40 trillion Death Stars firing at once. 40 trillion is a big number, if you counted one Death Star a second it would take you over a million years to tally them all. As the man said...
‘Bang’ doesn’t really do it justice. Fortunately there are no supernova candidates close enough to Earth to cause us any harm. But they can reach out and touch our atmosphere from enormous distances, evidence of past supernovae have been found in Antarctic ice cores, in the form of nitrate deposits.
Important safety tips from Lord Vader there. Although to be honest, given his obvious breathing difficulties he’s probably more worried about stormtroopers coughing on him than our well-being. | 0.898791 | 3.894531 |
When Russian astronomers detected the ‘virgin’ Comet ISON in September 2012, the world was hoping for something a little bit special. But no comet is the same and the nature of ‘dirty snowballs’ is rarely predictable.
In a NASA Comet ISON Observing Campaign (CIOC) blog update, astronomer Padma Yanamandra-Fisher (of the Space Science Institute) remarked on the unpredictable nature of ISON, saying: “this comet has decided to march to its own drummer.” In other words, even for a comet, ISON is its own beast, underlining the fact that comets still have many surprises up their icy sleeves.
ANALYSIS: Comet ISON Barely Survives Thanksgiving Solar Roast
So, as ISON made its solar close-pass (an event in its orbit known as ‘perihelion’) on Nov. 28, few would have been able to guess what was going to happen next.
Living up to its celebrity status, ISON put on a dramatic show on Thanksgiving Day, first fading from the view of solar observatories as it seemed to succumb to extreme solar heating. All seemed to be lost when the Solar and Heliospheric Observatory (SoHO) spotted a wisp of what seemed to be ISON’s ‘ashes’ re-emerge from the sun’s lower atmosphere — few would have doubted that ISON was toast; it had disintegrated.
Comet ISON-watchers were crestfallen — was this the end of ISON’s voyage through the inner solar system?
Comet ISON: 5 Things You Should Know
Just as the U.S. gave up hope and went back to the Thanksgiving Day wine, confused messages from astronomers studying data from the armada of solar observatories started to pour out. There was something in the debris stream; a possible chunk of Comet ISON had survived the extreme lower coronal environment a mere million miles from the sun’s “surface” (the photosphere). And it was brightening.
Now, around 24 hours post-perihelion, astronomers are tracking ISON once more as it continues its trek through the inner solar system. It obviously didn’t get away from its solar close encounter unscathed, but there is definitely a significant mass of comet material that made it though the solar roasting.
Comet ISON’s violent solar encounter may have caused a significant shedding of mass from ISON, perhaps exposing more primordial icy material (that formed during the early evolution of our solar system) to the sun’s heating. This is likely causing the brightening, but it seems unlikely that ISON will become the Comet of the Century. But it is without doubt one of the most fascinating objects to visit our solar system for some time and may help to rewrite the our understanding of sungrazing comets.
For more images and updates on Comet ISON go to Breaking The News Today blog. | 0.852358 | 3.790958 |
For the first time, in response to the public’s increased interest in being part of discoveries in astronomy, the International Astronomical Union (IAU) is organizing a worldwide contest to give popular names to selected exoplanets along with their host stars. The proposed names will be submitted by astronomy clubs and non-profit organisations interested in astronomy, and votes will be cast by the public from across the world through the web platform NameExoWorlds. This platform is under development by the IAU in association with Zooniverse. The intention is that millions of people worldwide will be able to take part in the vote. Once the votes are counted, the winning names will be officially sanctioned by the IAU, allowing them to be used freely in parallel with the existing scientific nomenclature, with due credit to the clubs or organizations that proposed them.
People have been naming celestial objects for millennia, long before any scientific system of names ever existed. Even today, almost every civilisation and culture uses common names to describe the stars and planets visible to the naked eye, as well as their apparent distribution on the sky — constellations, asterisms, etc.
When the IAU was created in 1919, professional astronomers delegated the task of giving official scientific names to newly discovered celestial objects to it. In parallel, throughout its history, the IAU has supported the contribution of the general public in naming various Solar System objects, as outlined in previous announcements (ann13009, ann13010, ann13012).
On 14 August 2013, the IAU issued a statement on the Public Naming of Planets and Planetary Satellites, which outlined a first set of rules that allowed the public to become involved in naming exoplanets. Capitalizing on the unique expertise of its members, the IAU through its Public Naming of Planets and Planetary Satellites Working Group has now developed a project in partnership with Zooniverse — home to the internet's largest, most popular and most successful citizen science projects .
The NameExoWorlds contest aims at crowdsourcing the process by which public names will be given to a large sample of well-studied, confirmed exoplanets and their host stars, referred to as ExoWorlds. The NameExoWorlds vote is conceived as a global, cross-cultural, educational, and above all ambitious and challenging contest, both for the IAU–Zooniverse partnership, and for the public. The main steps of the contest are the following :
A list of 305 well-characterized exoplanets, discovered prior to 31 December 2008 , has been selected for naming by the IAU Exoplanets for the Public Working Group and is being published today on the www.NameExoWorlds.org website. These exoplanets belong to 260 exoplanetary systems comprising one to five members, in addition to their host star.
In parallel, an IAU Directory for World Astronomy website is being prepared (directory.iau.org). This site will open in September 2014 and astronomy clubs and non-profit organisations interested in naming these exoplanets will be invited to register. The IAU will have the capability to handle the registration of thousands of such groups.
In October 2014, these clubs or organizations will be asked to vote for the 20–30 exoworlds they wish to name out of the list provided by the IAU. The actual number will depend on how many groups have registered.
From December 2014, these clubs or organizations will be able to send in proposals for the names of members and host stars of these selected ExoWorlds, based on the rules in the IAU Exoplanet Naming Theme, together with a detailed supporting argument for their choice. Each group will be allowed to name only one exoworld. More details on this stage will be given later.
From March 2015, the general public will be able to vote to rank the proposed exoworld names. The IAU and Zooniverse will be ready to handle a million votes or more worldwide.
Starting from July 2015, the IAU, via its Public Naming of Planets and Planetary Satellites Working Group, will oversee the final stages of the contest, and will validate the winning names from the vote.
The results will be announced at a special public ceremony held during the IAU XXIX General Assembly in Honolulu, USA, 3–14 August 2015.
The naming process will take place on www.NameExoWorlds.org website, where we encourage volunteers to translate the content into different languages in order to offer everyone the opportunity to take part in the contest (volunteer translators may email: [email protected]).
The winning names will not replace the scientific designations, which already exist for all exoplanets and their host stars, but they will be sanctioned by the IAU as their adopted names, and be publicized as such, along with due credit to the astronomy clubs or organisations that proposed them. These public names may then be used freely worldwide, along with, or instead of, the original scientific designation. It is expected that the winning names for the 20–30 systems will reflect the diversity of cultures on all continents.
The IAU is excited that the general public will be able to participate in this new and ambitious global challenge. Other contests may be organized after 2015. In the meantime, stay tuned for announcements about the next steps towards the first NameExoWorlds contest.
Zooniverse is a citizen science web portal owned and operated by the Citizen Science Alliance. The organization grew from the original Galaxy Zoo project and now hosts dozens of projects which allow volunteers to participate in scientific research.
Read more about the process in detail on the NameExoWorlds website.
The date refers to the date of submission to a refereed journal. Many exoplanets discovered after this date require confirmation or are incompletely characterized.
The IAU is the international astronomical organisation that brings together almost 11,000 distinguished astronomers from more than 90 countries. Its mission is to promote and safeguard the science of astronomy in all its aspects through international cooperation. The IAU also serves as the internationally recognised authority for assigning designations to celestial bodies and the surface features on them. Founded in 1919, the IAU is the world's largest professional body for astronomers.
IAU General Secretary / Institut d'Astrophysique de Paris
Tel: +33 1 43 25 83 58
Chris J. Lintott
Zooniverse, Citizen Science Alliance, University of Oxford
Oxford, United Kingdom
Cell: +44 7808 167288
Lars Lindberg Christensen
IAU Press Officer
Garching bei München, Germany
Tel: +49 89 320 06 761
Cell: +49 173 38 72 621
International Outreach Coordinator
Office for Astronomy Outreach, NAOJ, Japan | 0.835836 | 3.284388 |
Methane, a substance which goes hand in hand with life on Earth, has also been found on Mars. At a meeting of the American Geophysical Union (AGU) in New Orleans, Louisiana, NASA scientists reported that atmospheric methane on Mars exhibits a surprising variation. Its causes are still unknown.
Many things on Earth, from wetlands to permafrost, and from plants to animals themselves, generate methane. Researchers have been closely monitoring this substance as it is the most potent greenhouse gas in our atmosphere, albeit much more short-lived than CO2, for instance. But researchers were surprised to see any methane at all on frigid, barren Mars. Even more surprising was the large variation of the gas.
“The thing that’s so shocking here is this large variation,” said Chris Webster, who leads the methane-sensing instrument on NASA’s Curiosity rover. “We’re left trying to imagine how we can create this seasonal variation,” says Webster, who is at the Jet Propulsion Laboratory in Pasadena, California.
Scientists analyzed data from the Curiosity Rover. Since it landed on the Red Planet, the rover sampled Martian air 30 times, reporting extremely small background levels of the gas: around 0.4 parts per billion (ppb), compared with Earth’s 1800 ppb. But even small quantities need to come from somewhere. To make things even more mysterious, methane levels have been cycling from 0.3 ppb and 0.7 ppb over just two Martian years.
Some seasonality is, of course, to be expected. However, the mechanisms we’re currently aware of don’t even get close to explaining a variation of this magnitude. It could be that whatever is generating the methane has a temperature variation, which could translate to seasonality, but this is mere speculation at this point.
Diving into the realm of speculation, there’s also another possibility — “one that no one talks about but is in the back of everyone’s mind” — biological activity, says Mike Mumma, a planetary scientist at Goddard Space Flight Center in Greenbelt, Maryland. “You’d expect life to be seasonal.”
Life on Mars
Most of the methane on Earth was generated by microbes. There’s a good chance that the same process is, or was, happening on Mars. If this is the case, we would be dealing with either contemporary or ancient microbes. But ancient microbes wouldn’t really explain the seasonal variation, so going on this train of thought, it would appear more likely that we’re dealing with active microbial life on Mars. Yet this isn’t the only possible explanation.
Methane can also be generated through geological processes which have nothing to do with biology. Methane can be produced through hydrothermal reactions, especially ones involving olivine-rich rocks. It can also appear when carbon-containing meteoroids are bombarded by ultraviolet (UV) light, and dust falls down on the planet. This particular theory could also help explain the large variation.
Basically, the same chemical that produces methane from interplanetary dust at the surface level would be power-charged by UV light at high altitudes. As meteorite or comet dust particles fall down on the planet, they’re vaporized at tens of kilometers high in the air, producing significant quantities of methane. Since Curiosity’s reported variation can be somewhat correlated to meteor showers, Marc Fries, the cosmic dust curator at Johnson Space Center in Houston, Texas, believes this might explain the seasonality. But not everyone is convinced, and Fries himself concedes that meteor showers are highly variable and a causation is difficult to establish.
However, the good news is that Fries will have a chance to test his hypothesis: on 24 January, Mars will have a close encounter with comet C/2007 H2 Skiff — the comet is set to pass at less than a tenth of the Earth-moon distance. Even skeptics agree that this is a good opportunity to test the theory.
To make things even better, the European Space Agency’s ExoMars Trace Gas Orbiter will start observations on Mars, mapping methane distributions across the planet. But if neither of these tests confirms Fries’ theory, it’s back to the drawing board. | 0.853477 | 4.019855 |
The search for life in our universe, anywhere else besides Earth, continues to be a long and drawn-out process. So far, we have no leads; on the other hand, scientists continue their search based on the signatures of exoplanets that look and behave similarly to Earth.
One such potential candidate that was recently discovered was outlined in a new paper published this week in Nature. It’s a terrestrial Earth-like exoplanet dubbed LHS 1140b that resides around 40 light years away from us and is about 1.4 times the size of our planet.
Image Credit: M. Weiss/CfA
Astronomers say it circles the red dwarf star LHS 1140 once every 25 Earth days, exists within the star’s habitable zone and liquid water could potentially exist on its surface. This type of environment is ideal for live to thrive, which in turn has experts excited over the finding.
The star that LHS 1140b orbits is approximately one fifth of the size of our Sun, so the exoplanet is much closer to its host star than Earth is to the Sun. Nevertheless, because the star is producing far less energy, LHS 1140b is bombarded with much less energy than the Earth, which helps make life formation more possible.
The following illustration shows what a trip to LHS 1140 would look like:
It’s worth noting how a recent study suggested that exoplanets orbiting red dwarf stars are unlikely to support life, so there’s certainly a conflict of opinion in the astronomical community over where we’re likely to find life in the first place.
Nevertheless, because being the first to find life anywhere else in the universe besides planet Earth would come with great honors and eons of scientific citation, scientists aren’t leaving any rocks unturned.
While our current operating space observation equipment isn’t quite powerful enough to study life-supporting planets from so far away, the study does cite “telescopes under construction,” which might be able to.
They’re, of course, referring to the James Webb Space Telescope (JWST), which is slated to launch sometime in 2018 to explore the cosmos even further than the Hubble Space Telescope can with its much larger primary mirror and up-to-date sensory equipment.
It should be interesting to see if we can study the LHS 1140 system in more detail and whether or not we can find any traces of the exoplanet supporting life.
Source: New York Times | 0.817501 | 3.60155 |
An X-Ray image of a supernova remnant and its central neutron star
Click on image for full size
ROSAT satellite image courtesy of NASA
Neutron Stars are the end point of a massive star's life. When a really massive star runs out of nuclear fuel in its core the core begins to collapse under gravity. When the core collapses the entire star collapses. The surface of the star falls down until it hits the now incredibly dense core. It then bounces off the core and blows apart in a supernova
. All that remains is the collapsed core, a Neutron Star or sometimes a Black Hole
, if the star was really massive.
A typical neutron star is the size of a small city, only 10 Kilometers in diameter but it may have the mass of as many as three suns. It is quite dense. One spoonful of neutron star material on Earth would weigh as much as all the cars on Earth put together.
Some neutron stars spin very rapidly and have very strong magnetic fields. If the magnetic poles are not lined up with the star's rotation axis then the magnetic field spins around very fast. Charged particles can get caught up in the magnetic fields and
beam away radiation like a lighthouse lamp. This type of neutron star is called a pulsar. Pulsars are detected by their rapidly repeating radio signals beamed at Earth from those charged particles trapped in the magnetic field. When they were first discovered it was thought that they were radio signals from "Little Green Men" from outer space. Weird.
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What’s that dark spot on Jupiter? It’s the shadow of Jupiter‘s most volcanic moon Io. Since Jupiter shines predominantly by reflected sunlight, anything that blocks that light leaves a shadow. If you could somehow be in that shadow, you would see a total eclipse of the Sun by Io. Io‘s shadow is about 3600 kilometers across, roughly the same size as Io itself — and only slightly larger than Earth’s Moon. The featured image was taken last month by NASA’s robotic Juno spacecraft currently orbiting Jupiter. About every two months, Juno swoops close by Jupiter, takes a lot of data and snaps a series of images — some of which are made into a video. Among many other things, Juno has been measuring Jupiter’s gravitational field, finding surprising evidence that Jupiter may be mostly a liquid. Under unexpectedly thick clouds, the Jovian giant may house a massive liquid hydrogen region that extends all the way to the center.
Image & info via APOD: https://apod.nasa.gov/apod/astropix.html | 0.86957 | 3.043273 |
Strangelets in cosmic rays
Recently new data from the Cosmo-LEP project appeared, this time from DELPHI detector. They essentially confirm the findings reported some time ago by ALEPH, namely the appearence of bundles of muons with unexpectedly high multiplicities, which so far cannot be accounted by present day models. We argue, using arguments presented by us some time ago, that this phenomenon could be regarded as one more candidate for the presence in the flux of cosmic rays entering the Earth’s atmosphere from outer space nuggets od Strange Quark Matter (SQM) in form of so called strangelets.
Recently new data from Cosmo-LEP program, this time from DELPHI detector, has been reported . Among other things they have confirmed the findings reported before by ALEPH , namely that one observes bunches of cosmic muons (i.e., produced at the top of the Earth’s atmosphere) of unexpected large multiplicities (up to ). Their origin is so far unexplained and no model used in Monte Carlo (MC) programs simulating cascades of cosmic rays (CR) in the atmosphere is able to account for this phenomenon. In the expectation was made that source of this discrepancy can eventually come directly from the elementary interaction model used in MC. However, in our opinion, which we would like elaborate here in more detail, it could rather come (at least to a large extent) from the projectile initiating the cascade. Namely, as we have already done in many places on other occassions [3, 4], we shall argue that the abovementioned results of both experiments can be regarded as yet another signal of the presence in the flux of CR entering the Earth’s atmosphere of nuggets of Strange Quark Matter (SQM) called strangelets. In this way results of and would just continue a long list of other phenomena explanable in this way like anomalous cosmic ray burst from Cygnus X-3, extraordinary high luminosity gamma-ray bursts from the supernova remnant N49 in the Large Magellanic Cloud or Centauro (to mention only the most interesing and intriguing examples, for more details see [4, 5] and references therein). In we have already provided successful explanation of ALEPH observations by using notion of strangelets and assuming their flux being the same as obtained from analysis of all previous signals of strangelets present in the literature. (Actually, at that time ALEPH results were circulated only as conference papers, however, the final results presented in turned out to be identical to those addressed in ).
It is worth to remind here that CosmoLEP data are very important because: the high multiplicity cosmic muon events (muon bundles) are potentially very important source of information about the composition of primary CR because muons transport in essentially undisturbed way information on the first interaction of the cosmic ray particle with atmosphere; such events have never been studied with such precise detectors as provided by LEP program at CERN, nor have they been studies at such depth as at CERN (ranging between and meters what corresponds to muon momentum cut-off between and GeV).
2 Some Features of Strangelets
For completeness let us remind here the most important for us features of strangelets (see [3, 4] for details). They are hadron-like being a bag of up, down and strange quarks (essentially in equal proportion) becoming absolutely stable at high mass number (more stable than the most tightly bound nucleus as iron). However, they become unstable below some critical mass number, . Despite the fact that their geometrical radii are comparable to those of ordinary nuclei of the corresponding mass number , , they can still propagate very deep into atmosphere. This is because after each collision with the atmosphere nucleus strangelet of mass number becomes just a new
strangelet with mass number approximately equal and this procedure continues unless either strangelet reaches Earth or (most probably) disintegrates at some depth of atmosphere reaching . Actually, in a first approximation (in which ), in the total penetration depth of the order of
where is the usual mean free path of the nucleon in the atmosphere.
There are number of candidates for strangelets known in the literature, the common feature is their small ratio of charge and mass numbers, . The so called Saito events have and and . The most spectacular is Price event with but . On the other hand the Exotic Track event (ET) has been produced after the respective projectile has traversed g/cm of atmoshere. Finally, the so called Centauro events has been produced at depth g/cm and contains probably baryons . In Fig. 1 we show the resulting flux of strangelets obtained by considering the above signals . One can add to them the recently registered with AMS detector event with small ratio and also very small , estimated to be , it could be a metastable strangelet.
This is the picture we shall use to estimate the production of muon bundles produced as result of interaction of strangelets with atmospheric nuclei. We use for this purpose the SHOWERSIM modular software system specifically modified for our present purpose. Monte Carlo program describes the interaction of the primary particles at the top of atmosphere and follows the resulting electromagnetic and hadronic cascades through the atmosphere down to the observation level. Registered are muons with momenta exceeding GeV for ALEPH and GeV for DELPHI. Primaries initiated showers were sampled from the usual power spectrum with the slope index equal to and with energies above TeV.
The integral multiplicity distribution of muons from ALEPH data are compared with our simulations in Fig. 2. For completeness DELPHI data are present also. At first we have used here the so called ”normal” chemical composition of primaries with % of protons, % of helium, % of C-N-O mixture, % of Ne-S mixture and % of Fe. As one can see in Fig. 2 it can describe only the low multiplicity () region of ALEPH data. The small admixture of strangelets with the mass number being just above the estimated critical one estimated in the primary flux of CR (corresponding to relative flux of strangelets ) can, however, fully accomodate ALEPH data. As can be noticed DELPHI data differ rather substantially in shape from ALEPH data. They could be described equally well for but only with -fold smaller flux of strangelets. However, in this case events with small would fall completely outside the fit111In fact nothing better can be done because neither ALEPH or DELPHI can at the moment provide any explanation of this visible discrepancy of their respective results..
One should notice that results of both experiments differ already at small values of muon multiplicity. It looks like DELPHI makes preference for heavy composition of primary CR right from the beginning whereas ALEPH preferes somohow lighter (protonic) composition of CR. In any case, the excess of muons is clearly visible therefore we regard this as a possible additional signal of strangelets222There are still expected data from L3 experiment, however, so far the muonic part is not yet ready ..
To conclude: we propose to regard the Cosmo-LEP data on CR muons obtained so far as an additional possible signal of the possible SQM admixture present in the primary CR flux. We would like to add here that such admixture would also contribute to CR flux at energies greater than GZK cut-off [4, 16] explaining therefore this phenomenon in a quite natural way333If it will be finally confirmed by experiment .. This makes strangelets interesting subject to investigate in the future.
We would like to close with the following remark. With the flux of strangelets as estimated by us and used here (equal to in the enrgy range of tens of GeV) the energetic spectrum of strangelets should fall like , i.e., with spectral index being much smaller than for protons. Actually, this result agrees nicely with -dependence of the spectral index of CR’s obtaine when fitting the world CR data .
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- C.Timmermans (L3+C Coll.), Int. Conf. Cosmic Ray Conf., Salt Lake City (1999), Contributed Papers, Vol. 2 (1999) 9. See also: C.Taylor et al., (CosmoLEP Coll.), CosmoLEP and underground cosmic ray muon experiment in the LEP ring CERN/LEP 99-5 (1999) LEPC/P9 and Cosmic multi-muon events in ALEPH as part of the CosmoLEP project, CosmoLEP Report 1 (1999); cf. also: CERN Courier, Vol. 39-8, October (1999) 29.
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- See talk by P. Le Coultre, these proceedings.
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For the past 10 years, the European Space Agency (ESA)'s Rosetta spacecraft has been chasing a comet known (awkwardly) as 67P/Churyumov–Gerasimenko. And it's all come down to this - the day has finally come for it to send its lander probe, Philae, down to the surface in an attempt to become the first spacecraft to land on a comet.
In August this year, Rosetta finally caught up with and entered the orbit of the 4-km-wide space rock, which is on its way towards the Sun. Since then we've managed to learn a lot about the nature of comets, such as what they smell like (farts and horse pee) and how they respond as they warm up.
Fascinatingly, just yesterday Rosetta discovered that the comet is producing a mysterious, dolphin-like song produced “in the form of oscillations in the magnetic field in the comet’s environment," as ESA's Rosetta blog explains. The frequencies have been increased by a factor of around 10,000 so you can listen to the eerie track below.
But the biggest test comes today, when the ESA attempts to get Philae from the Rosetta craft onto the surface of the comet, a journey that will take around seven hours.
Philae will start its descent from Rosetta at 8pm AEST (9am GMT), and the expected landing time is around 3am AEST (4pm GMT). Because it takes around 30 minutes to up to an hour and a half for Philae to transmit information back to Rosetta, we won't know if the landing has been successful until around 4.30am AEST (5.30pm GMT).
If Philae achieves its goal, it'll stab harpoons into the surface of the comet to hold it into place and use its solar panel to recharge its battery. It'll then start making observations about the comet and beaming them back to Rosetta, until March when the surface will likely become to hot for the lander to survive.
These observations could help us understand how Earth formed in the Solar System, as astrophysicist Stephen Hughes from Queensland University of Technology in Australia explains.
"In some ways, comets are like bricks left on a building site long after the building is completed. We have high hopes the Rosetta mission will allow scientists to 'read' one of these bricks to obtain information about the formation of the Earth," said Hughes in a press release.
In particular, Philae will be analysing the type of water that makes up the comet, and testing whether it's similar to Earth's water. "This may indicate at least some of Earth's water was supplied by comets in the early days of the solar system," said Hughes.
Good luck, little lander, we'll all be watching. But, most importantly, good luck to all the amazing scientists, engineers and support staff who have been involved in the mission so far. Let's hope for more of these photos by the end of the day.
Now here's some creepy comet music to keep you occupied while you're watching the ESA researchers nervously await their fate. | 0.847266 | 3.745796 |
Daisies who pursue the Space Science Explorer badge will observe the sun, moon and sky, while Brownies tackling the Space Science Adventurer badge will delve into the planets, moon phases and constellations. Juniors, aka Space Science Investigators, will explore the celestial motion, the dimensions of constellations, and the size and scale of the solar system.
The US community faces a daunting task. Each generation of facilities is getting more expensive and harder to build. Operational costs are mounting. Meanwhile, the research budgets of the US National Science Foundation (NSF) and NASA have remained more or less flat since the 1990s (see ‘Astronomical costs’). Hard decisions have been made to close old but still-productive telescopes, which has proved insufficient to pay for new ones. And these pressures will only get worse as more big projects come online.
Researchers have detected a rogue planet traveling the void between stars some 20 light years away. Rogue planets or brown dwarfs (which this might be) aren’t exactly rare, cosmologically speaking, but they tend to be very difficult to see. And yet, the way we found this particular planet/brown dwarf suggests we might locate other similar stellar objects through an application of the same technique.
NASA's Parker Solar Probe will be the first spacecraft to "touch" the sun, hurtling through the sizzling solar atmosphere and coming within just 3.8 million miles (6 million kilometers) of the surface. It's designed to take solar punishment like never before, thanks to its revolutionary heat shield that's capable of withstanding 2,500 degrees Fahrenheit (1,370 degrees Celsius).
Astronomers have calculated that Mars will be a mere 35.8 million miles (57.6 million kilometers) next Tuesday, July 31. That’s practically in our backyard by some measures. The following week on Friday, August 11, Mars will be in opposition to the sun. That means the two objects will be on the exact opposite sides of the Earth.
Famed astronomer Galileo Galilei discovered the first four moons of Jupiter way back in the early 1600s. More than 400 years later, astronomers are still finding moons orbiting the solar system’s largest planet.
In the time it takes you to read this sentence, uncountable trillions of neutrinos have passed through your body. These ghostly particles rain down on us from the sun, but also from sources outside our solar system. Just a tiny fraction of neutrinos will run into anything on Earth, but scientists just detected one from outside our galaxy for the first time ever.
The disk of our home galaxy - the Milky Way - is bigger than we previously thought. A new study shows it would take 200,000 years for a spaceship traveling at the speed of light to go across the entire galaxy.
The National Science and Technology Council released a report Wednesday calling for improved asteroid detection, tracking and deflection. NASA is participating, along with federal emergency, military, White House and other officials. For now, scientists know of no asteroids or comets heading our way. But one could sneak up on us, and that's why the government wants a better plan.
The solar system just got a bit stranger. As astronomers continue their ongoing quest to find the elusive Planet Nine, a team found a space rock that lends credence to the idea that a huge super-Earth planet really exists in the outer reaches of our solar system. | 0.852519 | 3.464473 |
On WASP-121B, a hot Jupiter-like exoplanet, it’s hot – hotter than hot. That is the result of an orbit very close to a bright and warm host star. But also, according to a recent study, due to the heavy metals escaping from the upper atmosphere of the planet.
WASP-121B is an exoplanet discovered in 2015, about 850 light-years away from our Solar System, somewhere in the constellation of Stern. It is a hot Jupiter planet known especially for the water that has been detected in its atmosphere. It is also an ideal target for investigations of the future James-Webb space telescope, which will scan the infrared for water and carbon dioxide.
But in the framework of Panchromatic Comparative Exoplanet Treasury (PanCET) – the first large-scale comparative study of distant worlds in the ultraviolet, visible and infrared domains launched on the Hubble Space Telescope – WASP-121a reserved another surprise to astronomers. In search of spectral signatures of magnesium and iron in the light of the stars filtering through the atmosphere of the exoplanet, they made an astonishing observation.
For the first time, a stream of gas of heavy metals was observed escaping from the planet. In principle, hot planets the size of Jupiter remain cool enough inside to condense these heavy elements into clouds. But WASP-121 b orbits so close to its star that the temperature of its upper atmosphere reaches more than 2,500 ° C.
A surprisingly clear phenomenon
So it would essentially be the ultraviolet light (UV) of the sun of this amazing exoplanet, a sun warmer and brighter than ours, which would warm its upper atmosphere to allow heavy metals to escape. “And these metals make the atmosphere more opaque to UV, which further contributes to the warming of the upper atmosphere,” says David Singer, a researcher at Johns Hopkins University in Baltimore, United States.
“We were hoping to have the chance to observe this phenomenon on this planet that we know is extreme. But we were surprised by the clarity of the data and the presence of heavy metals as far away from the planet. WASP-121B is actively stripping its atmosphere,” says Singer. This result brings some additional elements to the understanding of how the planets lose their primordial atmospheres. When they are formed, the planets surround themselves with an atmosphere made essentially of hydrogen and helium, the most abundant elements of the Universe. An atmosphere they tend to lose as they get closer to their star. “In the case of WASP 121b, hydrogen and helium gas escape, dragging with them heavy metals,” concludes David Singer. | 0.851511 | 4.050864 |
A discovery of space dust could change how we understand the Solar System.
Scientists have been sampling dust grains from the Saturn region with the Cassini spacecraft, and they’ve made an incredible discovery: some of them came from outside the Solar System.
After analyzing millions of dust grains, a total of 36 of them appear to have an interstellar origin, according to a NASA statement.
Cassini has been orbiting around Saturn for the last 12 years, taking most of the dust it has been sampling from the moon Enceladus. Scientists first discovered intellar dust back in the 1990s, and had always hoped to detect them near Saturn.
Scientists suspect that these dust grains are from another part of spae because they travel at a much higher rate of speed and in a specific path different from the grains that are normally collected around Saturn.
The dust was typically traveling at around 45,000 miles per hour before getting caught in Saturn’s gravity.
“From that discovery, we always hoped we would be able to detect these interstellar interlopers at Saturn with Cassini. We knew that if we looked in the right direction, we should find them,” said Nicolas Altobelli, Cassini project scientist at ESA (European Space Agency) and lead author of the study, in the statement. “Indeed, on average, we have captured a few of these dust grains per year, travelling at high speed and on a specific path quite different from that of the usual icy grains we collect around Saturn.”
“Cosmic dust is produced when stars die, but with the vast range of types of stars in the universe, we naturally expected to encounter a huge range of dust types over the long period of our study,” added Frank Postberg of the University of Heidelberg, a co-author of the paper and co-investigator of Cassini’s dust analyzer. | 0.867964 | 3.768652 |
On November 18th, 2013, a 670 million dollar spacecraft was launched from Cape Canaveral in Florida. Scientists rejoiced when it reached space successfully, and NASA enthusiasts were engaged for a short time, but as the shuttle disappeared into the void of space towards its destination, it also disappeared from the public eye.
The launch of MAVEN (fig. 1)
But, ten months later, on September 21th 2014, it reached its destination: the orbit of Mars. This spacecraft, roughly the length of a school bus, is called MAVEN, or Mars Atmosphere and Volatile Evolution, with it’s primary task being to discover how and why Mars evolved into the red planet we see today. More specifically, scientists have described the mission as “the first mission devoted to studying the upper Martian atmosphere as a key to understanding the history of Mars’ climate, water and habitability,” (CNN).
An artist’s representation of MAVEN orbiting Mars (fig. 2)
But why research this? Don’t humans already know everything about the planets in our solar system? To answer this question we must first step back and examine our own world, the planet earth. Earth’s atmosphere is composed of five layers, the Troposphere, nitrogen, oxygen and water vapor rich, the Stratosphere, protecting us from the ultra violet rays of the sun, the Mesosphere, the Thermosphere, provider of the northern lights, and lastly, the most outer layer, the Exosphere, which gradually fades into space. Our atmosphere is very complex, as the combination of these layers together is what makes life on our planet possible. Mars has an atmosphere as well, but one much less complicated. It consists of four regions, the lower atmosphere, full of airborne dust, middle atmosphere, where the jet stream flows, and upper atmosphere, also known as thermosphere, the hottest region due to the heat of the sun, and lastly, the Exosphere, which is the same as that of Earths, where Mars’ atmosphere stops and slowly fades into the vacuum of space. The air on Mars consists of 95.3% carbon dioxide and 2.7% nitrogen, with the remaining 2% a combination of other gases. Mars’ atmosphere also is much, much less dense than that of Earth’s. But however thin it is, it exists, as if Mars did not have an atmosphere, pictures from the surface would show a black sky day and night, like the sky observed from Earth’s moon.
As one can discern from this information, Mars’ atmosphere is not suitable for human, plant, or animal life. It contains no oxygen, vital for survival, and has an empty, barren surface, devoid of resources or any sort of vegetation. But what drove Scientists to send MAVEN to the red planet was that they believe Mars was not always this way. They hypothesize that billions of years ago, Mars used to look like earth, that it had running water, and forests. Instead of red, the surface was blue and green. They believe that years and years ago Mars’ atmosphere was much more dense, and could support water in its’ liquid form on the surface. Curiosity, a rover from NASA that is currently roaming the planet, has found frozen materials in rocks, and indications of water beneath the exterior surface, showing this hypothesis to be probably true. But over time this seemingly Earth-like atmosphere and environment was lost, due to dramatic climate change. So what happened? Theories include Mars losing gas to space (an encroaching exosphere) over time, the loss of magnetic field, or the sun slowly stripping the atmosphere away. But there have been no real conclusions, as there has never been enough information or evidence to make them. Until, possibly, now. My personal opinion on what I have discovered about MAVEN, first, is that it is fascinating how we, as humans, are still discovering information about our solar system. To answer my earlier question posed: there is still so much we don’t know. After learning about MAVEN, I am itching to know what NASA discovers, if anything. I am hoping the news stations will soon light up some time over this next year, excitedly announcing that NASA has discovered influential and vitally important information about Mars from the MAVEN mission! But we will just have to wait and see.
What Scientists believe the surface of Mars used to look like (fig. 4)
As MAVEN begin its one year year long research mission, it will sample the gas and ion composition of the upper atmosphere and ionosphere. Scientists know now that Mars’ atmosphere is cold and dry place where liquid water cannot exist in a stable state. They believe they know what it used to be like: teeming with green and blue. But soon they may discover what caused the transformation of this now, red, barren planet, and this could change the way we see our universe forever. The age old question “Will we ever be able to live on Mars?” may soon be one step closer to answered, all because of a change in atmosphere.
“Ask an Astronomer.” Cool Cosmos. Web. 01 Oct. 2014. <http://coolcosmos.ipac.caltech.edu/ask/79-Does-Mars-have-an-atmosphere->.
“Atmosphere of Mars: Planet Mars Atmospheric Pressure, Layers & Sky.” Planet Facts. Web. 01 Oct. 2014. <http://planetfacts.org/the-atmosphere-of-mars/>.
The Comparison of the Atmospheres of Earth and Mars. Digital image. Science Junkie. Oct. 2013. Web. 01 Oct. 2014. <http://science-junkie.tumblr.com/post/50042175706/atomstargazer-a-comparison-of-earths-and-mars#.VC39lC5dUgN>.
Dunbar, Brian. “NASA – NASA Selects ‘MAVEN’ Mission to Study Mars Atmosphere.” NASA. NASA, 15 Sept. 2008. Web. 02 Oct. 2014. <http://www.nasa.gov/mission_pages/mars/news/maven_20080915.html#.VC38MS5dUgN>.
“The MAVEN Mission.” NASA. NASA. Web. 01 Oct. 2014. <http://www.nasa.gov/content/maven-launch/#.VC2IhS5dUgM>.
“MAVEN.” NASA. NASA. Web. 01 Oct. 2014. <http://www.nasa.gov/mission_pages/maven/main/#.VCyNxi5dUgM>.
Presto, Suzanne. “MAVEN Spacecraft Enters Mars Orbit to Explore Its Climate Change.” CNN. Cable News Network, 21 Sept. 2014. Web. 01 Oct. 2014. <http://www.cnn.com/2014/09/21/tech/mars-maven-spacecraft-orbit/index.html?iref=allsearch>. | 0.842435 | 3.764797 |
The distribution of metals in the Galaxy provides important information about galaxy formation and evolution. H II regions are the most luminous objects in the Milky Way at mid-infrared to radio wavelengths and can be seen across the entire Galactic disk. We used the National Radio Astronomy Observatory (NRAO) Green Bank Telescope to measure radio recombination line and continuum emission in 81 Galactic H II regions. We calculated LTE electron temperatures using these data. In thermal equilibrium metal abundances are expected to set the nebular electron temperature with high abundances producing low temperatures. Our H II region distribution covers a large range of Galactocentric radius (5-22 kpc) and samples the Galactic azimuth range 330°-60°. Using our highest quality data (72 objects) we derived an O/H Galactocentric radial gradient of -0.0383 ± 0.0074 dex kpc-1. Combining these data with a similar survey made with the NRAO 140 Foot telescope we get a radial gradient of -0.0446 ± 0.0049 dex kpc-1 for this larger sample of 133 nebulae. The data are well fit by a linear model and no discontinuities are detected. Dividing our sample into three Galactic azimuth regions produced significantly different radial gradients that range from -0.03 to -0.07 dex kpc-1. These inhomogeneities suggest that metals are not well mixed at a given radius. We stress the importance of homogeneous samples to reduce the confusion of comparing data sets with different systematics. Galactic chemical evolution models typically derive chemical evolution along only the radial dimension with time. Future models should consider azimuthal evolution as well. | 0.863429 | 3.596526 |
If force (F), velocity(V) and time (T) are taken as fundamental units, the dimensions of mass are
A projectile is fired from the surface of the earth with a velocity of 5ms–1 and angle θ with the horizontal. Another projectile fired from another planet with a velocity of 3ms–1 at the same angle follows a trajectory which is identical with the trajectory of the projectile fired from the earth. The value of the acceleration due to gravity on the planet is: (given = 9.8 ms–2)
A particle is moving such that its position coordinates (x, y) are (2m, 3m) at time t = 0, (6m,7m) at time t = 2s and (13m, 14m) at time t = 5 s,
Average velocity vector from t = 0 to t = 5 s is :
A system consists of three masses m1, m2 and m3 connected by a string passing over a pulley P. The mass m1 hangs freely and m2 and m3 are on a rough horizontal table (the coefficient of friction = μ). The pulley is frictionless and of negligible mass. The downward acceleration of mass m1 is : (Assume m1 = m2 = m3 = m)
The force 'F' acting on a particle of mass 'm' is indicated by the force-time graph shown below. The change in momentum of the particle over the time interval from zero to 8 s is :
1. 24 Ns
2. 20 Ns
4. 6 Ns
A balloon with mass 'm' is descending down with an acceleration 'a' (where a < g). How much mass should be removed from it so that is starts moving up with an acceleration 'a' ?
A body of mass (4m) is lying in x-y plane at rest. It suddenly explodes into three pieces. Two pieces, each of mass (m) move perpendicular to each other with equal speeds (υ). The total kinetic energy generated due to explosion is :
A solid cylinder of mass 50 kg and radius 0.5 m is free to rotate about horizontal axis. A massless string is wound round the cylinder with one end attached to it and other hanging freely. Tension in the string required to produce an angular acceleration of 2 revolutions s–2
1. 25 N
2. 50 N
3. 78.5 N
4. 157 N
The ratio of the acceleration for a solid sphere (mass 'm' and radius 'R') rolling down an incline of angle 'θ' without slipping and slipping down the incline without rolling is :
A block hole is an object whose gravitational field is so strong that even light cannot escape from it. To what approximate radius would earth (mass = 5.98×1024 kg) have to be compressed to be a black hole ?
Copper of fixed volume 'V' is drawn into wire of length 'λ'. When this wire is subjected to a constant force 'F', the extension produced in the wire is 'Δ. Which of the following graph is a straight line ?
A certain number of spherical drops of a liquid of radius 'r' coalesce to form a single drop of radius 'R' and volume 'V'. If 'T' is the surface tension of the liquid, then:
1. Energy=4VT is released.
2. Energy=3VT is released.
3. Energy=3VT is released.
4. Energy is neither released nor absorbed.
Steam at 1000C is passed into 20g of water at 100C When water acquires a temperature of 800C, the mass of water present will be:
[ Take specific heat of water = 1 cal g–1 0C–1 and latent heat of steam = 540 cal g–1]
1. 24 g
2. 31.5 g
3. 42.5 g
4. 22.5 g
Certain quantity of water cools from 700C to 600C in the first 5 minutes and to 540C in the next 5 minutes. The temperature of the surroundings is;
A mono atomic gas at a pressure P, having a volume V expands isothermally to a volume 2V and then adiabatically to a volume 16V. The final pressure of the gas is : (take γ= 5/3)
1. 64 P
2. 32 P
4. 16 P
A thermodynamics system undergoes cyclic process ABCDA as shown in Fig. The work done by the system in the cycle is:
The mean free path of molecules of a gas (radius 'r') is inversely proportional to:
If n1, n2 and n3 are the fundamental frequencies of three segments into which a string is divided, then the original fundamental frequency n of the string is given by:
The number of possible natural oscillations of air column in a pipe closed at one end of length 85 cm whose frequencies lies below 1250 Hz are: (velocity of sound = 340 ms–1)
A speeding motorcyclist sees traffic jam ahead of him. He slows down to 36km/hour. He finds that traffic has eased and a car moving ahead of him at 18 km/hour is honking at a frequency of 1392 Hz. If the speed of sound is 343 m/s, the frequency of the honk as heard by him will be:
1. 1332 Hz
2. 1372 Hz
3. 1412 Hz
4. 1454 Hz
A conducting sphere of radius R is given a charge Q. The electric potential and the electric field at the centre of the sphere respectively are:
1. Zero and
2. and zero
4. Both are zero.
In a region the potential is represented by V(x, y, z) = 6x – 8xy –8y + 6yz, where V is in volts and x, y, z, are in meters. The electric force experienced by a charge of 2 coulomb situated at point (1, 1,1) is :
2. 30 N
3. 24 N
Two cities are 150 km apart. Electric power is sent from one city to another city through copper wires. The fall of potential per km is 8 volt and the average resistance per km is 0.5 The power loss in the wire is:
1. 19.2 W
2. 19.2 kW
3. 19.2 J
4. 12.2 kW
The resistance in the two arms of the meter bridge are 5 and R, respectively. When the resistance R is shunted with an equal resistance, the new balance point is at 1.6l1. The resistance 'R' is :
A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery, used across the potentiometer wire, has an emf of 2.0 V and a negligible internal resistance. The potentiometer wire itself is 4 m long. When the resistance, R, connected across the given cell, has values of (i) infinity (ii) 9.5, the 'balancing lengths, on the potentiometer wire, are found to be 3m and 2.85 m, respectively.
The value of internal resistance of the cell is (in ohm) :
In an ammeter 0.2% of main current passes through the galvanometer. If resistance of galvanometer is G, the resistance of ammeter will be:
Two identical long conducting wires AOB and COD are placed at the right angle to each other, with one above other such that 'O' is their common point for the two. The wires carry I1 and I2 currents, respectively. Point 'P' is lying at distance 'd' from 'O' along a direction perpendicular to the plane containing the wires. The magnetic field at the point 'P' will be :
A thin semicircular conducting the ring (PQR) of radius 'r' is falling with its plane vertical in a horizontal magnetic field B, as shown in figure. The potential difference developed across the ring when its speed is v is:
2. and P is at the higher potential
3. and R is at the higher potential
4. 2BvR and R is at the higher potential
A transformer has an efficiency of 90% is working on 200 V and 3 kW power supply. If the current in the secondary coil is 6 A the voltage across the secondary coil and the current in the primary coil respectively are:
1. 300 V, 15 A
2. 450 V, 15 A
3. 450 V, 13.5 A
4. 600 V, 15 A
Light with an energy flux of 25 × 104 Wm–2 falls on a perfectly reflecting surface at normal incidence. If the surface area is 15 cm2, the average force exerted on the surface is :
A beam of light of λ = 600 nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between first dark fringes on either side of the central bright fringe is :
1. 1.2 cm
2. 1.2 mm
3. 2.4 cm
4. 2.4 mm
In Young's double-slit experiment, the intensity of light at a point on the screen where the path difference is λ is K, (λ being the wavelength of light used). The intensity at a point where the path difference is λ/4 will be :
It the focal length of the objective lens is increased then magnifying power of :
1. microscope will increase but that of telescope decrease
2. microscope and telescope both will increase
3. microscope and telescope both will decrease
4. microscope will decrease but that of the telescope will increase
The angle of a prism is 'A'. One of its refracting surfaces is silvered. Light rays falling at an angle of incidence 2A on the first surface returns back through the same path after suffering reflection at the silvered surface. The refractive index μ, of the prism, is :
1. 2sin A
3. cos A
4. tan A
When the energy of the incident radiation is increased by 20%, the kinetic energy of the photoelectrons emitted from a metal surface increased from emitted 0.5 eV to 0.8eV. The work function of the metal is :
1. 0.65 eV
2. 1.0 eV
3. 1.3 eV
4. 1.5 eV
If the kinetic energy of the particle is increased to 16 times its previous value, the percentage change in the de-Broglie wavelength of the particle is :
The hydrogen atom in the ground state is excited by monochromatic radiation of λ = 975 Å. The number of spectral lines in the resulting spectrum emitted will be :
The Binding energy per nucleon of and nucleon are 5.60 MeV and 7.06 MeV, respectively. In the nuclear reaction , the value of energy Q released is:
1. 19.6 MeV
2. -2.4 MeV
3. 8.4 MeV
4. 17.3 MeV
A radioisotope 'X' with a half-life 1.4 × 109 years decays to 'Y' which is stable. A sample of the rock from a cave was found to contain 'X' and 'Y' in the ratio 1:7. The age of the rock is :
1. 1.96 x 109 years
2. 3.92 x 109 years
3. 4.20 x 109 years
4. 8.40 x 109 years
X decay to Y (stable)
Ratio of X and y = 1:7
at the start t0 = 0 X = N0 and Y = 0
after time t
X will be N0 – X
Y = X
N0 – X/x = 1/7
X = 7 N0/8
Remaining nuclei = N0 – X = N0 - 7 N0/8
= N0/8 = N0/23
Number of half life passed = 3
t = 3X half life = 3x 1.4 × 109 years = 4.2× 109 years
1. It is V -I characteristic for solar cell where, point A represents open circuit voltage and point B short circuit current.
2. It is for a solar cell and points A and B represent open circuit voltage and current, respectively.
3. It is for a photodiode and points A and B represent open circuit voltage and current respectively.
4. It is for a LED and points A and B represent open circuit voltage and short circuit current, respectively.
The barrier potential of a p-n junction depends on:
(a) type of semiconductor material
(b) amount of doping
Which one of the following is correct?
1. (a) and (b) only
2. (b) only
3. (b) and (c) only
4. (a),(b) and (c)
What is the maximum number of orbitals that can be identified with the following quantum number
n = 3, l = 1, m = 0
Calculate the energy in corresponding to light of wavelength 45 nm : (Planck's constant h = 6.63 × 10–34 Js: speed of light c = 3 × 108 ms–1)
1. 6.67 x 1015
2. 6.67 x 1011
3. 4.42 x 10-15
4. 4.42 x 10-18
Equal masses of H2, O2 and methane have been taken in a container of volume V at temperature 27 ºC in identical conditions. The ratio of the volumes of gases H2:O2 : methane would be -
If a is the length of the side of a cube, the distance between the body centered atom and one corner atom in the cube will be:
Which property of colloids is not dependent on the charge on colloidal particles ?
4. Tyndall effect
Which of the following salts will give highest pH in water ?
Of the following 0.10m aqueous solutions, which one will exhibit the largest freezing point depression ?
When 22.4 litres of H2(g) is mixed with 11.2 litres of Cl2(g), each at STP, the moles of HCl(g) formed is equal to :
1. 1 mol of HCl(g)
2. 2 mol of HCl(g)
3. 0.5 mol of HCl(g)
4. 1.5 mol of HCl(g)
When 0.1 mol is oxidised the quantity of electricity required to completely to is :
1. 96500 C
2. 2 x 96500 C
3. 9650 C
4. 96.50 C
Using the Gibbs change, ΔG º = + 63.3 kJ, for the following reaction, Ag2CO3(g) 2Ag+ (aq) + (aq) the Ksp of Ag2CO3(s) in water at 25 ºC is (R = 8.314 JK–1 mol–1)
The weight of silver (at.wt. = 108) displaced by a quantity of electricity which displaces 5600 mL of O2at STP will be :
1. 5.4 g
2. 10.8 g
3. 54.0 g
4. 108.0 g
Which of the following statements is correct for the spontaneous adsorption of a gas ?
1. S is negative and therefore, H should be highly positive
2. S is negative and therefore, H should be highly negative
3. S is positive and therefore, H should be negative
4. S is positive and therefore, H should also be highly positive
For the reversible reaction :
N2(g) + 3H2(g) 2NH3(g) + heat
The equilibrium shifts in forward direction -
1. by increasing the concentration of
2. by decreasing the pressure
3. by decreasing the concentration of
4. by increasing pressure and decreasing temperature
For the reaction :
X2O4(l) → 2XO2(g)
ΔU = 2.1 kcal, ΔS = 20 cal K–1 at 300 K
The value of ΔG is
1. 2.7 k cal
2. -2.7 k cal
3. 9.3 k cal
4. -9.3 k cal
or a given exothermic reaction, Kp and Kp’ are the equilibrium constants at temperatures T1 and T2respectively. Assuming that heat of reaction is constant in temperatures range between T1 and T2, it is readily observation that:
Which of the following orders of ionic radii is correctly represented?
1.0 g of magnesium is burnt with 0.56 g O2 in a closed vessel. Which reaction is left in excess and how much? (At, wt.Mg = 24; O = 16)
1. Mg, 0.16 g
2. , 0.16 g
3. Mg, 0.44 g
4. , 0.28 g
The pair of compounds that can exist together is:
Be2+ is isoelectronic with which of the following ions?
Which of the following molecules has the maximum dipole moment ?
Which one of the following species has plane triangular shape ?
Acidity of diprotic acids in aqueous solutions increases in the order:
(a) H2O2 + O3 → H2O + 2O2
(b) H2O2 + Ag2O → 2Ag + H2O + O2
Role of hydrogen peroxide in the above reactions is respectively:
1. oxidizing in (a) and reducing in (b)
2. reducing in (a) and oxidizing in (b)
3. reducing in (a) and (b)
4. oxidizing in (a) and (b)
Artificial sweetner which is stable under cold conditions only is:
In acidic medium, H2O2 changes Cr2O7–2 to CrO5 which has two (–O – O–) bonds Oxidation state of Cr in CrO5 is :
The reaction of aqueous KMnO4 with H2O2 in acidic conditions gives:
Among the following complexes the one which shows zero crystal field stabilization energy (CFSE) is
agnetic moment 2.83 BM is given by which of the following ions?
(At.nos.Ti=22, Cr=24, Mn=25, Ni=28)
Which of the following complexes is used to be as an anticancer agent ?
Reason of lanthanoid contraction is:
1. Negligible screening effect of 'f' orbitals
2. Increasing nuclear charge
3. Decreasing nuclear charge
4. Decreasing screening effect
Which of the following will be most stable diazonium salt ?
Which of the following hormones is produced under the condition of stress which stimulates glycogenolysis in the liver of human being ?
Which of the following organic compounds polymerizes to form the polyester Dacron?
1. Propylene and para
2. Benzolic acid and ethanol
3. Terepthalic acid and ethylene glycol
4. Benzoic acid and para
Which one of the following is not a common component of Photochemical Smog?
3. Peroxyacetyl nitrate
In the Kjedahl’s method for estimation of nitrogen present in soil sample, ammonia evolved from 0.75g of sample neutralized 10ml. of 1M H2SO4 The percentage of nitrogen in the soil is:
Which of the following compounds will undergo racemisation when solution of KOH hydrolysis?
(i) (ii) CH3CH2CH2Cl (iii) (iv)
1. (i) and (ii)
2. (ii) and (iv)
3. (iv) only
4. (i) and (iv)
Among the following sets of reaction which one produces anisole?
1. CH3CHO ; RMgX
2. C6H5OH ; NaOH ; CH3l
3. C6H5OH ; neutral FeCl3
4. C6H5 - CH3 ; CH3COCl ; AlCl3
Which of the following will not be soluble in sodium hydrogen carbonate ?
1. 2, 4, 6-trinitrophenol
2. Benzoic acid
4. Benezenesulphonic acid
Identify Z in the sequence of reactions:
Which of the following organic compounds has same hybridization as its combustion product –(CO2) ?
Which one of the following shows isogamy with non-flagellated gametes?
Five kingdom system of classification suggested by R.H. Whittaker is based on:
1. Complexity of body organisation
2. Mode of reproduction
3. Mode of nutrition
4. All of the above
Which one of the following fungi contains hallucinogens?
1. Morchella esculenta
2. Amanita muscaria
3. Neurospora sp.
4. Ustilago sp.
Archaebacteria differ from eubacteria in:
1. Cell membrane stucture
2. Mode of nutrition
3. Cell shape
4. Mode of reproduction
Which one of the following is wrong about Chara?
1. upper oogonium and lower round antheridium
2. Globule and nucule present on the same plant
3. Upper antheridium and lower oogonium
4. Globule is male reproductive structure
Which of the following is responsible for peat formation?
Placenta and pericarp are both edible portions in :
When the margins of sepals or petals overlap one another without any particular direction, the condition is termed as:
You are given a fairly old piece of dicot stem and a dicot root. Which of the following anatomical structures will your use to distinguish between the two?
1. Secondary xylem
2. Secondary phloem
4. Cortical cells
Which one of the following statements is correct?
1. The seed in grasses is not endospermic
2. Mango is a parthenocarpic fruit
3. A proteinaceous aleurone layer is present in maize gain.
4. A sterile pistil is called a staminode.
Tracheids differ from the tracheary elements in :
1. Having casparian strips
2. Being imperforate
3. Lacking nucleus
4. Being lignified
An example of edible underground stem is:
3. Sweet potato
Which structures perform the function of mitochondria in bacteria ?
3. Cell wall
The solid linear cytoskeletal elements having a diameter of 6 nm and made up of a single type of monomer are known as
3. Intermediate filaments
The osmotic expansion of a cell kept in water is chiefly regulated by
During which phase(s) of cell cycle, amount of DNA in a cell remains at 4 C level if the initial amount is denoted as 2C ?
1. G0 and G1
2. G1 and S
3. Only G2
4. G2 and M
Match the following and select the correct answer :
List - I
List – II
(i) Infoldings in mitochondria
(iii) Nucleic acids
(iv) Basal body cilia or flagella
1. A-iv B-ii C-i D-iii
2. A-i B-ii C-iv D-iii
3. A-i B-iii C-ii D-iv
4. A-iv B-iii C-i D-ii
Dr F. Went noted that if coleoptile tips were removed and placed on agar for one hour, the agar would produce a bending when placed on one side of freshly - cut coleoptile stumps. Of what significance is this experiment?
1. It made possible the isolation and exact identification of auxin.
2. It is the basis for quantitative determination of small amounts og growth-promoting substances.
3. It supports the hypothesis that IAA is auxin.
4. It demonstated polar movements of auxins.
Deficiency symptoms of nitrogen and potassium are visible first in :
1. Senescent leaves
2. Young leaves
In which one of the following processes CO2 is not released ?
1. Aerobic respiration in plants
2. Aerobic respiration in animals
3. Alcoholic fermentation
4. Lactate fermentation
Anoxygenic photosynthesis is characteristic of:
A few normal seedling of tomato were kept in a dark room. After few days they were found to have become white- coloured like albions, Which of the following terms will you use to describe them ?
Which one of the following growth regulators is known as stress hormone ?
1. Abscissic acid
4. Indole acetic acid
1. Fertilization of a flower by the pollen from another flower of the same plant
2. Fertilization of a flower by the pollen from another same flower.
3. Fertilization of a flower by the pollen from a flower of another plant in the same population
4. Fertilisation of a flower by the pollen from a flower of another plant belonging to a distant population
Male gametophyte with least number of cells is present in :
An aggregate fruit is one which devloped from
1. Multicarpellary syncarppous gynoecium
2. Multicarpellary apocarpous gynoecium
3. Complete inflorescence
4. Multicarpellary superior ovary
Pollen tablets are available in the market for:
1. In vitro fertilization
2. Breeding programmes
3. Supplementing food
4. Ex situ conservation
Function of filiform apparutus is to :
1. Recognize the suitable pollen at stigma
2. Stimulate division of genrative cell
3. Producer nector
4. Guide the entry of pollen tube
Non- albuminous seed is produced in:
Which of the following shows coiled RNA strand and capsomeres ?
1. Polio virus
2. Tobacco mosaic virus
3. Measles virus
4. Retro virus
Which one of the following is wrongly matched?
1. Transcription- Writing information from DNA to t-RNA
2. Translation- Using information in m-RNA to make protein
3. Repressor protein- Binds to a operator to stop enzyme synthesis
4. Operon- Structural genes, operator and promoter
Transformation was discovered by :
1. Meseson and Stahl
2. Hershey and chase
4. Waston and crick
Fruit colour in squash is an example of :
1. Recessive epistasis
2. Dominant epistasis
3. Complementary genes
4. Inhibitory genes
Viruses have :
1. DNA enclosed in a protein coat
2. Prokaryotic nucleus
3. Single chromosome
4. Both DNA and RNA
The first human hormone produced by recombinant DNA technology is :
An analysis of chromosomal DNA using the Southern hybridization technique does not use:
In vitro clonal propagation in plants in characterized by :
1. PCR and RAPD
2. Northern blotting
3. Electrophoresis and HPLC
An alga which can be employed as food for human beings :
Which vector can clone only a small fragment of DNA?
1. Bacterial artificial chromosome
2. Yeast artificial chromosome
An example of ex situ conservation is :
1. National park
2. Seed bank
3. Wildlife sactuary
4. Sacred grove
A location with luxuriant growth of lichens on the trees indicates that the :
1. Trees are very healthy
2. Trees are heavily infested
3. Location is highly polluted
4. Location is not polluted
Match the following and select the correct option :
List - I
(c) Ecosystem service
(d) Population growth
List – II
(i) Pioneer species
1. A-(i) B-(ii) C-(iii) D-(iv)
2. A-(i) B-(ii) C-(iii) D-(iv)
3. A-(iii) B-(ii) C-(iv) D-(i)
4. A-(ii) B-(i) C-(iv) D-(iii)
A species facing extremely high risk of extinction in the immediate future is called
3. Critically Endangered
The zone of atmosphere in which the ozone layer is present is called
The organization which published the Red List of species is
Select the Taxon mentioned that represents both marine and fresh water species :
Select the Taxon mentioned that represents both marine and fresh water species :
Which one of the following living organisms completely lacks a cell wall?
2. Sea- fan (Gorgonia)
4. Coelenterata algae
Planaria possess high capacity of
3. alternation of generation
A marine cartilaginous fish that can produce electric current is:
Choose the correctly matched pair:
1. Tendon-Specialized connective tissue
2. Adipose tissue-Dense connective tissue
3. Areolar tissue- Loose connective tissue
4. Cartilage- Loose connective tissue
Choose the correctly matched pair
1. Inner lining of salivary ducts- Ciliated epithelium
2. Moist surface of buccal cavity- Glandular epithelium
3. Tubular parts of nephrons- Cuboidal epithelium
4. Inner surface of bronchioles- Squamous epithelium
In 'S' phase of the cell cycle
1. amount of DNA doubles in each cell.
2. amount of DNA remains same in each cell
3. chromosome number is increased
4. amount of DNA is reduced to half in each cell.
The motile bacteria are able to move by
Select the option which is not correct with respect to enzyme action:
1. Substrate binds with enzyme at its active site.
2. Addition of lot of succinate does not reverse the inhibition of succinic dehydrogenase by malonate
3. A non-competitive inhibitor binds the enzyme at a site distinct from that which binds the substrate
4. malonate is a competitive inhibitor of succinic dehydrogenase
Which one of the following is a non-reducing carbohydrate?
4. Ribose 5-phospohate
The enzyme recombinase is required at which stage of meiosis
The initial step in the digestion of milk in infant is carried out by ?
Fructose is absorbed into the blood through mucosa cells of intestine by the process called
1. Active transport
2. Facilitated transport
3. Simple diffusion
4. Co-transport machenism
Approximately seventy percent of carbon-dioxide absorbed by the blood will be transported to the lungs
1. as bicarbonate ions
2. in the form of dissolved gas molecules
3. by binding to R.B.C
4. as carbamino-haemoglobin
Person with blood group AB is considered as universal recipient because he has:
1. both A and B antigens on RBC but no antibodies in the plasma
2. both A and B antibodies in the plasma
3. no antigen on RBC and no antigens in the plasma
4. both A and B antigens in the plasma but no antibodies
How do parasympathetic neural signals affect the working of the heart?
1. reduce both heart rate and cadiac output
2. Heart rate is increased without affecting the cardiac output
3. Both heart rate and cardiac output increased
4. Heart rate decreases but cardiac output increases
Which of the following causes an increase in sodium reabsorption in distal convoluted tubule?
1. Increase in aldosterone levels
2. Increase in antidiuretic hormone levels
3. Decrease in aldosterone levels
4. Decrease in antidiuretic hormone levels
Select the correct matching of the types of the joint with the example in human skeletal system:
Stimulation of a muscle fiber by a motor neuron occurs at:
1. the neuromuscular junction
2. the transverse tubules
3. the myofibril
4. the sacroplasmic reticulum
Injury localized to the hypothalamus would most likely disrupt
1. short-term memory
2. co-ordination during locomotion
3. executive functions, such as decision making
4. regulation of body temperature
Which one of the following statements is not correct?
1. Retinal is the light absorbing portion of visual photo pigments
2. In retina the rods have the photopigments rhodospin while cones have three different photopigments.
3. Retinal is a derivative of Vitamin C
4. Rhodospin is the purplish protein present in rods only.
Identify the hormone with its correct matching of source and function:
1. Oxytocin- posterior pituitary, growth and maintenance of mammary glands.
2. Melatonin- pineal gland, regulates the normal rhythm of sleepwake cycle.
3. Progesterone- corpus-luteum, stimulation of growth and activities of female secondary sex organs.
4. atrial natriuretic factor- ventricular wall increases the blood pressure.
Fight - or - flight reaction cause activation of
1. the parathyroid glands, leading to increased metabolic rate.
2. the kidney, leading to suppression of rennin angiotensin-aldosterone pathway.
3. the adrenal medulla, leading to increased secretion of epinephrine and norepinephrene
4. the pancreas leading to a reduction in the blood sugar levels.
The shared terminal duct of the reproductive and urinary system in the human male is:
3. Vas deferens
4. Vasa efferentia
The main function of mammalian corpus luteum is to produce:
1. estrogen only
3. human chorionic gonadotropin
4. relaxin only
Select the correct option describing gonadotropin activity in a normal pregnant female:
1. High level og FSH and LH stimulates the thickening of endometrium.
2. High level of FSH and LH facilitate implantation of the embryo
3. High level of hCG stimulates the synthesis if estrogen and progesterone
4. High level of hCG stimulates the thickening of endometrium.
Tubectomy is method of sterilization in which
1. small part of fallopian tube is removed or tied up.
2. ovaries are removed surgically
3. small part of vas deferens is removed or tied up
4. uretuis is removed surgically
Which of the following is a hormone releasing intra Uterine Device (IUD) ?
1. Multiload 375
2. LNG - 20
3. Cervical cap
Assisted reproductive technology, IVF involves transfer of
1. Ovum into the fallopian tube.
2. Zygote into the fallopian tube.
3. Zygote into the uterus
4. Embryo with 16 blastomeres into the fallopian tube.
A man whose father was colour blind marries a woman who had a colour blind mother and a normal father. What percentage of male children of this couple will be colour blind?
In a population of 1000 individuals 360 belong to genotype AA, 480 to Aa and the remaining 160 to aa, Based on this data, the frequency of allele A in the population is :
A human female with Turner's syndrome:
1. has 45 chromosomes with XO
2. has one additional chromosome.
3. exhibit male character
4. is able to produce children with normal husband.
Select the correct option:
Commonly used vectors for human genome sequencing are:
2. BAC and YAC
3. Expression Vectors
4. T/A cloning Vectors
Forelimbs of cat, lizard used in walking; forelimbs of whale used in swimming and forelimbs of bats used in flying are an example of :
1. Analogous organs
2. Adaptive radiation
3. Homologous organs
4. Convergent evolution
Which one of the following are analogous structures?
1. Wing of Bat and Wings of Pigeon
2. Gills of Prawn and Lungs of Man
3. Thorns of Bougainvillea and Tendrils of CUcurbita
4. Flippers of Dolphin and Legs of Horse.
Which is the particular type of drug that is obtained from the plants whose one flowering branch is shown below?
4. Pain - Killer
At which stage of HIV infection does one usually show symptoms of AIDS?
1. Within 15 days of sexual contact with an infected person
2. When the infected retro virus enters host cells
3. When HIV damage large number of helper T - Plymphocytes.
4. When the viral DNA is produced by reverse transcriptase.
To obtain virus - free healthy plants from a diseased one by tissue culture technique, which part/parts of the diseased plant will be taken ?
1. Apical meristem only
2. Palisade parenchyma
3. Both apical and axillary meristems
4. Epidermis only
What gases are produced in anaerobic sludge digesters?
1. Methane and CO2
2. Methane, Hydrogen Sulphide and CO2
3. Methane, Hydrogen Sulphide and CO
4. Hydrogen Sulphide and CO2
Just as a person moving from Delhi to Shimla to escape the heat for the duration of hot summer, thousands of migratory birds from Siberia and other extremely cold northern regions move to:
1. Western Ghat
3. Corbett National Park
4. Keolado National Park
Given below is a simplified model of phosphorus cycling in a terrestrial ecosystem with four blanks (A-D). Identify the blanks.
The extent of global diversity of invertebrates is represented in the image below. Choose the correct combination of groups (A-D) respectively?
A scrubber in the exhaust of a chemical industrial plant removes:
1. Gases like sulphue dioxide
2. Particulate matter of the size 5 micrometer or above
3. Gases like ozone and methane
4. Particulate matter of the size 2.5 micrometer or less
If 20 J of energy is trapped at producer level, then how much energy will be available to peacock as food in the following chain?
Plant → mice →snake→ peacock\
1. 0.02 J
2. 0.002 J
3. 0.2 J
4. 0.0002 J | 0.829821 | 3.259649 |
|Diameter||60–160 km (37–99 mi)|
|Age||364 ± 8 Ma|
Late Devonian to Early Carboniferous
Woodleigh is a large meteorite impact crater (astrobleme) in Western Australia, centred on Woodleigh Station east of Shark Bay, Gascoyne region. A team of four scientists at the Geological Survey of Western Australia and the Australian National University, led by Arthur J. Mory, announced the discovery in the 15 April 2000 issue of Earth and Planetary Science Letters.
The crater is not exposed at the surface and therefore its size is uncertain. The original discovery team stated in 2000 that it may be up to 120 km (75 mi) in diameter, but others argue it may be much smaller, with one 2003 study suggesting a diameter closer to 60 km (37 mi). The larger estimate of 120 km, if correct, would make this crater tied for the fourth largest confirmed impact structure in the world, and imply a bolide (asteroid or comet) about 5 to 6 km (3.1 to 3.7 mi) in diameter. A more recent study in 2010 suggests the crater could be between 60 and 160 kilometres (37 and 99 mi) or more, and was produced by a comet or asteroid 6 to 12 kilometres (3.7 to 7.5 mi) wide.
The central uplift, interpreted to be 20 km (12 mi) in diameter, was first intersected by drilling activities in the late 1970s; however its significance as an impact structure was only realised in 1997 during a gravity survey. In 1999, a new core sample was taken. The thin veins of melted glass, breccia, and shocked quartz found would have formed under pressures 100,000 times greater than atmospheric pressure at sea level, or between 10 and 100 times greater than those generated by volcanic or earthquake activity. Only a large impact could have generated such conditions. The reported discovery in 2018 of the extremely rare mineral reidite in a drillcore sample from the central uplift zone, supports the interpretation of the crater as being over 100 km in diameter, and possibly the largest in Australia.
The Woodleigh impact event, originally thought to have occurred between the Late Triassic and Late Permian, is now thought to date from 364 ± 8 million years (Late Devonian). This time corresponds approximately to the Late Devonian extinction. There is evidence for other large impact events at around the same time, such as the East Warburton Basin, so if the extinction is related to impact, perhaps more than one crater was involved.
Of the two dozen or more impact craters known in Australia, the three largest are Woodleigh, Acraman, and Tookoonooka. The Gnargoo structure, which has remarkable similarities to Woodleigh, is a nearby proposed impact crater on the Gascoyne platform.
- Mory AJ, Iasky RP, Glikson AY, Pirajno F (2000). "Woodleigh, Carnarvon Basin, Western Australia: a new 120 km diameter impact structure". Earth and Planetary Science Letters. 117 (1–2): 119–128. Bibcode:2000E&PSL.177..119M. doi:10.1016/S0012-821X(00)00031-5. Abstract
- Reimold WU, Koeberl C, Hough RM, Mcdonald I, Bevan A, Amare K, French BM (2003). "Woodleigh impact structure, Australia: Shock petrography and geochemical studies". Meteoritics & Planetary Science. 38 (7): 1109–1130. Bibcode:2003M&PS...38.1109R. doi:10.1111/j.1945-5100.2003.tb00301.x. Abstract and full PDF
- Mory A, Iasky R (2000). Woodleigh — Australia's largest impact structure?. Fieldnotes, Geological Survey of Western Australia. 16. pp. 1–2. ISBN 978-0-7307-5642-2. PDF Archived 23 August 2006 at the Wayback Machine
- Gareth Barton (27 October 2010). "Giant crater may have been extinction trigger". Cosmos. Archived from the original on 12 October 2016. Retrieved 15 August 2012.
- Discovery of reidite, one of the rarest minerals on Earth, may reveal Australia's biggest crater ABC News, 16 October 2018. Retrieved 17 October 2018.
- "Woodleigh". Earth Impact Database. Planetary and Space Science Centre University of New Brunswick Fredericton. Retrieved 9 October 2017.
- R. Iaskty and A. Glikson (2005). "Gnargoo: a possible 75 km-diameter post-Early Permian – pre-Cretaceous buried impact structure, Carnarvon Basin, Western Australia", Australian Journal of Earth Sciences, Vol 52, 2005 | 0.871054 | 3.623373 |
Quarter* ♉ Taurus
Moon phase on 26 January 2015 Monday is Waxing Crescent, 7 days young Moon is in Aries.Share this page: twitter facebook linkedin
Previous main lunar phase is the New Moon before 5 days on 20 January 2015 at 13:14.
Moon rises in the morning and sets in the evening. It is visible toward the southwest in early evening.
Lunar disc appears visually 0.7% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1936" and ∠1949".
Next Full Moon is the Snow Moon of February 2015 after 8 days on 3 February 2015 at 23:09.
There is medium ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at very acute angle, so their combined tidal force is moderate.
The Moon is 7 days young. Earth's natural satellite is moving from the beginning to the first part of current synodic month. This is lunation 186 of Meeus index or 1139 from Brown series.
Length of current 186 lunation is 29 days, 10 hours and 34 minutes. It is 45 minutes longer than next lunation 187 length.
Length of current synodic month is 2 hours and 10 minutes shorter than the mean length of synodic month, but it is still 3 hours and 59 minutes longer, compared to 21st century shortest.
This lunation true anomaly is ∠338.3°. At the beginning of next synodic month true anomaly will be ∠354.5°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
4 days after point of perigee on 21 January 2015 at 20:06 in ♒ Aquarius. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 10 days, until it get to the point of next apogee on 6 February 2015 at 06:25 in ♍ Virgo.
Moon is 370 230 km (230 050 mi) away from Earth on this date. Moon moves farther next 10 days until apogee, when Earth-Moon distance will reach 406 155 km (252 373 mi).
1 day after its descending node on 25 January 2015 at 10:23 in ♈ Aries, the Moon is following the southern part of its orbit for the next 13 days, until it will cross the ecliptic from South to North in ascending node on 8 February 2015 at 17:10 in ♎ Libra.
13 days after beginning of current draconic month in ♎ Libra, the Moon is moving from the second to the final part of it.
8 days after previous South standstill on 18 January 2015 at 06:17 in ♐ Sagittarius, when Moon has reached southern declination of ∠-18.577°. Next 4 days the lunar orbit moves northward to face North declination of ∠18.513° in the next northern standstill on 31 January 2015 at 00:59 in ♋ Cancer.
After 8 days on 3 February 2015 at 23:09 in ♌ Leo, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.83659 | 3.175238 |
Guest post by Philip Mulholland
The following two figures, showing the principal features of the Earth’s Energy Budget, were published in 1997 by the Oklahoma Climatological Survey (OK-First) and are reproduced here with kind permission.
Both of these diagrams when combined provide detailed energy budget information for the Earth’s climate; however, their parameters are recorded as percentages of solar insolation at the top of the atmosphere (TOA). Neither diagram published by OK-First records the actual values of solar power intensity, nor is it demonstrated how they can be used to estimate the global average temperature for the surface of the Earth.
A number of assumptions must be made in order to understand how the OK-First diagrams can be used to estimate the average global temperature under an expected solar insolation radiant power intensity of *1368 W/m2, and the albedo of 0.30 used in Figure 1. *N.B. The standard NASA Earth irradiance is 1361 W/m2 and the Bond albedo is 0.306 (Williams, 2019). However, in 1997 the solar irradiance used by Kiehl and Trenberth (1997) was 1368 W/m2, and so this value is used here to give the most appropriate match to this historic paper (Fig. 3) (reproduced below with kind permission).
2. Filling in the Gaps.
At first sight it is clear that Figure 1 shows that 30% of the solar insolation is bypassed via albedo loss, and so only 70% of the power intensity is available to heat the planet. If we now apply the standard divide by 4 spherical geometry rule to the expected (but not yet confirmed) solar irradiance of 1368 W/m2, then the TOA power intensity will be reduced to 235 W/m2 post-albedo (as per Kiehl and Trenberth, 1997). However, and confusingly, because the percentages relate to the unfiltered TOA power intensity, it follows that the power intensity values in the OK-First diagrams are percentages of the assumed (but not yet confirmed) pre-albedo value of 342 W/m2, and so this power intensity number must be used. By this means consistency in both percentages and also power intensity values will be maintained throughout the OK-First diagrams, the elements of which are presented below in Table 1.
The next assumption we must make is that the standard partition of energy by the atmosphere is being applied. The standard assumption is that for all energy fluxes intercepted by the atmosphere, half of the flux is directed upwards, and lost to space, and half of all captured flux is returned to the surface as back radiation and recycled. This concept is shown in figure 4 (reproduced here with kind permission).
Fig. 4: Equipartition of energy flux by the Atmospheric layer (Jacob, 1999 Fig.7-12)
Because the intercepted energy flux is being recycled this feed-back loop is an endless sum of halves of halves. It has the mathematical form of a geometric series, and is a sum of the descending fractions in the power sequence 2– n, where minus n is a continuous sequence of natural numbers ranging from zero to infinity.
Equation 1: 1/2 + ¼ + 1/8 + 1/16 + 1/32 + …. + 2-n = 1
Equation 1 describes the cumulative effect of the feed-back loop (after an infinite series of additions), where for each turn of the cycle, half the ascending energy flux is passed out to space and lost, and the other half is returned back to the ground surface and then re-emitted. It is a feature of this form of an infinite series that the sum of the series is not itself an infinite number, but in this case the limit is the finite natural number 1.
As a direct consequence of applying Equation 1 to the OK-First atmospheric model we must double the energy flux within the atmosphere, because the atmosphere retains and stores an energy flux equal to that of the total intercepted flux. When we apply the logic of the 50%:50% atmospheric energy flux partition to the OK-First analysis, then we are able to create the following table of percentage atmospheric energy recycling (Table 2): –
Table 2 demonstrates that the power intensity experienced by the atmosphere is 128% of the incoming solar beam, and in addition the power intensity flux emitted by the surface, and directly attributable to the high frequency solar insolation, adds another 51% to the planetary energy budget. This means that the total power intensity flux that drives the Earth’s climate is 179% of the pre-albedo TOA insolation according to the OK-First diagram.
In order to justify what is clearly a contentious statement I will now apply the identical process of deconstruction to the accepted diagram of Kiehl and Trenberth, with its recorded power intensity values (Fig. 3), and compare this with the atmospheric absorption elements as listed in Figs. 1 & 2 by OK-First.
Table 3 demonstrates that the total power intensity flux absorbed by the atmosphere in the Kiehl and Trenberth diagram is 195 W/m2, and that this power intensity is then doubled to 390 W/m2 by the process of atmospheric recycling, which includes recycling of both the thermals and also evaporation energy fluxes. Using the standard Stefan-Boltzmann equation to convert irradiance power intensity to thermodynamic temperature
Where j* is the black body radiant emittance in Watts per square metre, then the average temperature of the Earth’s atmosphere for a total atmospheric power intensity flux of 390 W/m2 is 288 Kelvin (15o Celsius).
Table 4 below demonstrates that the total energy budget for the Earth is driven by 168 W/m2 of surface intercepted and incoming atmospheric absorbed solar insolation. This flux must be added to the intercepted and recycled atmospheric flux of 390 W/m2 (that contains the direct atmospheric solar interception of 67 W/m2) to give a planetary energy budget of 558 W/m2, which equates to a thermodynamic temperature of 315 Kelvin (42o Celsius). The surface fluxes of 1. Surface Longwave Radiation, 2. Thermals and 3. Evaporation are all losses that create surface cooling and so combine to produce the expected Surface Radiation flux of 390 W/m2, which equates to a thermodynamic temperature of 288 Kelvin (15o Celsius).
If at this point you are beginning to wonder why the much-vaunted back radiation has been adjusted, and why some of the returning radiant flux in the Kiehl and Trenberth diagram can be replaced with recycled energy fluxes from the descending air (returned thermals) then please bear with me.
Let us return to the OK-First diagrams (Figs. 1 & 2) now that the table of flux values has been validated using the Kiehl and Trenberth power intensity metrics and apply the same TOA input flux of 342 W/m2 used in Fig. 3 to the table of percentages created from the OK-First diagrams and displayed in Table 2.
This insolation power intensity flux of 342 W/m2, when combined with the published percentages of OK-First can be used to create a table of power intensity values (Table 6) and associated thermodynamic temperatures (Table 7).
The global average surface temperature of 23oC calculated using the OK-First data is higher than that calculated by Kiehl and Trenberth. This temperature difference arises from a number of possible causes.
1. The OK-First model is using a lower Bond albedo.
2. The solar irradiance used by OK-First for the calculation of percentages is unknown but assumed to be the same number as that used by Kiehl and Trenberth.
3. The balance of energy partition fluxes within the OK-First model is different from the canonical model, and this is the most likely cause of the bias towards the calculated higher global average temperature.
Kiehl and Trenberth and OK-First, use identical concepts in the formation of their global energy budget diagrams, however both originators present their results in ways that do not clearly demonstrate the commonality or the rigor of the concepts used. In particular both sources fail to illustrate the implicit role of atmospheric mass movement in the process of energy recycling that also heats the surface of our planet. In the presence of a gravity field that binds the atmosphere to the surface of a planet, what goes up must come down. The distribution of energy fluxes in Table 3 show that for the total atmospheric energy budget of 558 W/m2 (Table 4), 63.44% (354 W/m2) is transmitted by radiation fluxes and 36.56% (204 W/m2) is carried by mass motion (Table 8).
So clearly mass motion is an important energy carrying process within the Earth’s atmosphere. It is critical to understand at this point that because our energy budget is formulated in terms of power intensity, if the proportion of flux carried by mass motion increases due to an increase in moist convectional overturning, then the proportion of energy transmitted by radiant processes must decrease (and vice versa), a given energy flux cannot do two things at once.
In addition, we find that because the energy budgets of OK-First and also Kiehl and Trenberth are clearly built on the equipartition of energy by the atmosphere (half up and half down), then there are only two ways that the internal energy budget of the Earth’s atmosphere can be increased.
1. The longwave surface to space atmospheric window is closed, which causes more energy to be recycled within the atmosphere.
2. The planetary Bond albedo is decreased which allows more solar energy to enter the climate system.
Issue #1 relates directly to concerns that carbon dioxide emissions increase the opacity of our semi-transparent atmosphere, and will close the atmospheric window (Fig. 5). We can test the effects of closing this window on global average temperature by using Table 3, and diverting the 40 W/m2 direct to space radiant emission into atmospheric capture and heating (Table 9).
The impact of closing the Earth’s long wave emission atmospheric window is to raise the global average temperature from 15oC to 29oC (Table 10). This 14oC increase is the maximum possible temperature increase that the Earth can experience by internal energy recycling for a constant Bond albedo of 0.306.
In order to further raise the Earth’s average global temperature above 29oC to form a Cretaceous hothouse world it is necessary to either increase the atmospheric mass, (thereby raising atmospheric pressure and also the boiling point of water), and/or reduce the planetary brightness by lowering the Earth’s Bond albedo. Assuming total blocking of the atmospheric thermal radiant window and also assuming no increase in atmospheric mass, then it is possible to achieve a Cretaceous global average temperature of 36oC with a planetary Bond albedo of 0.244 (Table 11).
This reduction in planetary brightness can be achieved by having a Cretaceous world with no surface icecaps, and also an increased continental surface inundation associated with a high global sea level to create a putative low albedo hothouse world (Table 12).
Replacing reflective continental solid land surfaces with a liquid surface of shallow solar energy absorbing seas means that the Earth would capture and transmit more solar energy from the tropics to the poles via the oceanographic currents of a flooded world (e.g. the Tethys Ocean). Assuming a Cretaceous meteorological distribution of energy flux, pro-rata to that of the modern world, then the key energy budget metrics for a 36oC world are speculatively recorded in Table 13.
There are some fundamental messages that come from this analysis of these diagrams of the Earth’s energy budget: –
Issue #1. Internal energy recycling limits the maximum possible temperature rise to an increase of plus 14oC, assuming total blocking of the longwave atmospheric window and an unchanged Bond albedo. It is impossible for the Earth to experience a runaway greenhouse effect if the total mass of the atmosphere does not increase.
In order to achieve a putative Cretaceous global average temperature of 36oC, it is necessary to both reduce the Earth’s albedo to 0.244, and also to apply total blocking of surface to space longwave radiation (and/or raise the total mass of the atmosphere).
Total blocking of the atmospheric window by Carbon Dioxide may not be possible. This is an issue that was studied by Ferenc Miskolczi (2010) in his paper “The Stable Stationary Value of the Earth’s Global Average Atmospheric Planck-Weighted Greenhouse-Gas Optical Thickness”.
Miskolczi stated his conclusions as: –
New relationships among the flux components have been found and are used to construct a quasi-all-sky model of the earth’s atmospheric energy transfer process. In the 1948-2008 time period the global average annual mean true greenhouse-gas optical thickness is found to be time-stationary. Simulated radiative no-feedback effects of measured actual CO2 change over the 61 years were calculated and found to be of magnitude easily detectable by the empirical data and analytical methods used.
The data negate increase in CO2 in the atmosphere as a hypothetical cause for the apparently observed global warming. A hypothesis of significant positive feedback by water vapor effect on atmospheric infrared absorption is also negated by the observed measurements. Apparently major revision of the physics underlying the greenhouse effect is needed.
Issue #2. Changes in the value of the Earth’s planetary Bond albedo are a valid mechanism by which global warming can occur. Variations in water distribution in the forms of either reflective ice and/or cloud; or absorbing surface water areal variations by either short term sea-ice distribution or long-term geologic ocean distribution (e.g. The Tethys Ocean) is the primary route to change planetary albedo. This dominance of water either in its reflective role of clouds and ice leading to planetary albedo increase, or in its absorptive form as a transparent surface liquid replacing polar sea ice, means that there is no albedo role for atmospheric carbon dioxide to change global average temperatures. Unlike water, carbon dioxide is not a condensing gas in the Earth’s atmosphere, and so it has no impact on insolation energy capture via changes in reflective planetary brightness.
Issue #3. The standard climate model has the following basic features with specific rules applied.
1. The planetary disc intercept rule. – The average solar irradiance is divided by 4 and spread over the surface of the globe.
2. The albedo bypass rule. – A given percentage of the planetary insolation is bypassed by planetary brightness and not used within the climate system.
3. The remaining solar insolation is absorbed by the planet/atmosphere.
4. The planetary atmosphere is leaky. – Low frequency thermal radiation can pass from the surface directly out to space.
5. The atmosphere is an energy reservoir.
6. Energy recycling by the atmosphere doubles the quantity of energy in this reservoir. – The half in / half out rule of back radiation energy flux partition.
7. Rule six limits the maximum possible gain to times 2. –The infinite recycling geometric series limit.
What this all means is that for a planet with a zero albedo surface (that is with 100% insolation high-energy absorption under a totally clear atmosphere) and a totally opaque atmosphere for exiting surface thermal radiation (that is no surface leaks to space and total 100% atmospheric thermal radiant blocking) then the absolute limit of the internal energy budget is 3 times the Solar Irradiance flux divided by 4.
For planet Earth, with a planetary solar irradiance of 1361.0 W/m2 (Williams, 2019), the maximum possible planetary energy budget for a hypothetical Bond albedo of zero and total atmospheric insolation clarity is 1361*0.75 = 1020.75 W/m2. This flux translates into a maximum possible energy budget thermodynamic temperature of 366.3 Kelvin (93.3oC) (Table 14).
For Venus, with a solar irradiance of 2601.3 W/m2 (Williams, 2018), the maximum possible planetary energy budget for a hypothetical Bond albedo of zero and total atmospheric insolation clarity is 2601.3*0.75 = 1951 W/m2. This flux translates into a maximum possible energy budget thermodynamic temperature of 430.7 Kelvin (157.7oC), but the surface temperature of Venus is 737 Kelvin (464oC) (Williams, 2018).
From this analysis we can deduce that the standard climate model is compromised. The back-radiation concept cannot explain why Venus has a surface temperature of 464oC by atmospheric radiant energy flux recycling. The solar flux captured by the Venusian atmosphere is far too low to produce the observed surface temperature, even if that planet had a Bond albedo of zero and total atmospheric insolation clarity (which it clearly does not have).
Jacob, D.J. 1999. Introduction to Atmospheric Chemistry. Princeton University Press.
Kiehl, J.T and K.E. Trenberth, 1997. Earth’s Annual Global Mean Energy Budget. Bulletin of the American Meteorological Society, Vol. 78 (2), 197-208.
Miskolczi, F.M., 2010. The stable stationary value of the earth’s global average atmospheric Planck-weighted greenhouse-gas optical thickness. Energy & Environment, 21(4), pp.243-262.
Oklahoma Climatological Survey 1997 Earth’s Energy Budget.
Williams, D.R. 2018 Venus Fact Sheet.
Williams, D.R. 2019 Earth Fact Sheet. | 0.834182 | 3.340323 |
- Image 1 of 2
- Image 2 of 2
NASA's Hubble Space Telescope has captured three of Jupiter's moons marching across the huge planet's disc, a stunning sight that happens only once or twice every 10 years.
The rare triple-moon conjunction on Jupiter, which Hubble witnessed on Jan. 24, involved Io, Callisto and Europa — three of the gas giant's four Galilean moons (so named because they were discovered by astronomer Galileo Galilei in the early 17th century).
"The moons in these photos have distinctive colors. The ancient, cratered surface of Callisto is brownish; the smooth icy surface of Europa is yellow-white; and the volcanic, sulfur-dioxide surface of Io is orange," representatives of the Space Telescope Science Institute (STScI) in Baltimore, which operates Hubble, wrote in a statement Feb. 5. [See more photos of Jupiter's rare triple-moon shadow dance]
"The apparent 'fuzziness' of some of the shadows depends on the moons' distances from Jupiter," they added. "The farther away a moon is from the planet, the softer the shadow, because the shadow is more spread out across the disk."
The conjunction lasted about 42 minutes. The fourth Galilean moon, Ganymede, was outside Hubble's field of view during the triple transit, STScI representatives said.
Volcanic Io is the innermost of the Galilean moons, completing one lap around Jupiter every 1.8 days. Europa, Ganymede and Callisto have orbital periods of 3.6, 7.2 and 16.7 days, respectively.
With a diameter of 3,270 miles, Ganymede is the largest natural satellite in the solar system. Indeed, it's bigger than the planet Mercury.
Europa is the smallest Galilean moon, at 1,900 miles wide, but it generates excitement and intrigue disproportionate to its size. The satellite harbors an ocean of liquid water beneath its icy shell, and this ocean is thought to be in contact with Europa's rocky mantle, making possible all kinds of interesting chemical reactions.
Indeed, many scientists regard Europa as the solar system's best bet to host alien life. NASA is mapping out a robotic mission to Europa, which agency officials say should be ready to launch by the mid-2020s. | 0.800837 | 3.317407 |
I am back from the 45th annual Division of Planetary Sciences meeting in Denver, Colorado, where I presented my findings on the study of the triple asteroid system (87) Sylvia through a poster and in a press conference (video here). Located in the asteroid main-belt, we know that (87) Sylvia possesses two moons since our publication in Nature Journal in 2005. Our team has combined observations from professional-class telescopes and from small telescopes used by amateur astronomers to reveal that this 270-km diameter main-belt asteroid has a complex interior, probably linked to the way the multiple system was formed.
Since the discovery of its second moon, we have continued to observe this triple asteroid system by gathering 66 adaptive optics observations collected with various 8-10m class telescopes such as the W.M. Keck Observatory, the Very Large Telescope and the Gemini North telescope.
Because (87) Sylvia is a large, bright (V=10.5) asteroid located in the main belt, it is a great target for the first generation of adaptive optics systems available on these large telescopes. We have combined data from our team with archival data to get a good understanding of the orbits of these moons.
With expert assistance from colleagues at the Institut de Mécanique Céleste et de Calcul des Éphémérides (IMCCE) of the Observatoire de Paris, we developed an accurate dynamical model of the system, allowing us to predict the position of the moons around the asteroid at any time.
The “drop test” of this work was the prediction of the relative positions of the moons during an occultation on Jan. 6, 2013. Observers equipped with small telescopes located on a narrow path across the south of France, Italy and Greece could see the triple system (87) Sylvia occulting a bright 11-mag star.
In collaboration with EURASTER, a group of amateur and professional astronomers, the team successfully motivated ~50 observers to watch the event. Twelve of them detected the occultation by the primary of the system which lasted between 4 and 10 seconds depending on their position on Earth.
Additionally, four observers also detected a two-second eclipse of the star caused by Romulus, the outermost satellite, at a relative position close to our prediction. This result confirmed the accuracy of our model and provided a rare opportunity to directly measure the size and shape of the satellite.
The chords of this occultation revealed that Romulus is a body 24 km in diameter with an extremely elongated shape, possibly made of two lobes joined together. This is not surprising if the satellite formed from the accretion of fragments created by the disruption of a proto-Sylvia by an impact, which occurred several billion years ago.
We derived the shape of the 270-km primary asteroid Sylvia by combining data from the occultation of the asteroid with other sources of information. These included archived recordings of the variation of light caused by the spin of the satellite, and direct imaging by adaptive optics systems. Because the satellites’ orbits do not seem to be affected by the irregular shape of the asteroid, we concluded that the large asteroid is most likely differentiated. The asteroid likely has a spherical core of dense material, surrounded by a fluffy or fractured outer surface layer.
Combined observations from small and large telescopes provide a unique opportunity to understand the nature of this complex and enigmatic triple asteroid system. Thanks to the presence of these moons, we can constrain the density and interior of an asteroid, without the need for a spacecraft’s visit. Knowledge of the internal structure of asteroids is key to understanding how the planets of our solar system formed.
I would like to thank NASA PAST NNX11AD62G for their support and Danielle Futselaar for her fantastic drawing. This work is about to be submitted to Icarus Journal (Berthier et al. 2013). Let me know if you want me to send you the submitted version. | 0.830632 | 3.765221 |
Students, lecturers and researchers are helping scientists install the first major radio telescope in Britain for many decades at STFC’s Chilbolton Observatory in Hampshire this week (June 7-11). The telescope which is part of the European LOFAR project (Low Frequency Array) will ‘listen’ to the Universe at FM frequencies, helping astronomers detect when the first stars in the Universe were formed revealing more about how the Universe evolved.
The participants from a consortium of universities are helping scientists at Chilbolton to install the 96 telescope radio antennae. When completed, LOFAR will consist of over 5000 separate antennae spread in ‘stations’ all over Europe forming the world’s largest and most sensitive radio telescope.
Derek Mckay works for STFC's Rutherford Appleton Laboratory whose staff manage the Chilbolton site, says; “It’s been very satisfying watching the UK progress so quickly working with the students is great. They’re enthusiastic and enjoying the challenge. The work is going very well and the work is very exciting - I mean let’s face it, it’s the largest radio telescope in the world and to lead for the UK’s contribution is a fantastic opportunity”.
“The LOFAR telescope will produce an enormous volume of data which will enable a significant amount of science, from monitoring the sun’s activity or ‘space weather,’ to potentially searching for alien intelligence,” said Professor Bob Nichol of the University of Portsmouth’s Institute of Cosmology and Gravitation, and LOFAR-UK spokesperson. “Maybe we can answer the age-old question ‘Are we alone?’”
The antennae will work at the lowest frequencies accessible from the Earth and will be connected using sophisticated computing and high speed internet. A super computer based in the Netherlands, will use digital electronics to combine the signals from the antennae to make images of the entire radio sky.
“At the Chilbolton site, seven petabytes of raw data will be produced each year, which must be transferred in real time to Holland. That’s like streaming 100 high definition TV channels for every second of every day for the next five years. This exciting facility will also contribute to UK and European preparations for the planned global next generation radio telescope, the Square Kilometre Array (SKA)," said Professor Rob Fender of the University of Southampton, Principal Investigator of the LOFAR-UK project.
LOFAR-UK is funded through a collaboration of UK universities with the SEPnet (link opens in a new window) consortium and the UK Science and Technologies Facilities Council.
For more information please contact: RAL Space Enquiries | 0.806626 | 3.121762 |
Jupiter’s conspicuous opposition in the Balance
Jupiter is at its brightest and best in the constellation of Libra, the Weighing Scales or Balance, this month. Its opposition, when it stands directly opposite the Sun, occurs on the morning of the 9th but it is prominent every night as it transits low across the south from the south-east at nightfall to the south-west before dawn.
Venus, however, outshines it in the western evening sky and both Saturn and the increasingly striking Mars follow Jupiter into the southern morning sky.
The Sun climbs another 7° northwards during May as Edinburgh’s sunrise/sunset times change from 05:29/20:52 BST on the 1st to 04:36/21:45 on the 31st. Because twilight is also lengthening, official darkness in the middle of the night lasts for under one hour by May’s end.
The Moon is at last quarter on the 8th, new on the 15th, at first quarter on the 22nd and full on the 29th.
Venus stands 20° high in the west at sunset, sinking to set in the north-west by 23:40 on the 1st and one hour later by the 31st. Brilliant at magnitude -3.9, it begins the month 6° above-right of Taurus’ brightest star, Aldebaran, and tracks east-north-eastwards between the Bull’s horns to end May in mid-Gemini, below Castor and Pollux.
The young earthlit Moon makes an impressive sight almost 6° below-left of the planet on the evening of the 17th. Three days later, as Venus joins the region of sky covered by our chart, it passes 1.0° (two Moon-diameters) above-right of the star cluster M35 whose brightest stars may be glimpsed through binoculars from their distance of some 2,800 light years. Still on the far side of its orbit, Venus approaches from 217 million to 190 million km this month as its almost-full disk swells to 13 arcseconds in diameter.
After dominating our winter nights, Orion ducks below our western horizon as the evening twilight fades at present. The Plough is overhead and Leo high in the south with its main star Regulus which has a close encounter with the first quarter Moon on the night of 21st/22nd.
By our map times, Leo sis inking in the west and Jupiter is easily the most conspicuous object in the south though it stands barely 18° high for Edinburgh. Moving westwards in Libra, it lies close to the Moon on the 27th. Its motion takes it from 4° east (left) of the well-known double star Zubenelgenubi at present to lie just 1.0° north-east of the star on the 31st.
Jupiter is 658 million km away at opposition, shines at magnitude -2.5 and shows a 45 arcseconds wide disk through a telescope. Its two main darker cloud bands, its northern and southern equatorial belts, straddle a lighter equatorial zone. The famous Great Red Spot is gradually losing its status, however, being less than half as wide as it was a century ago and currently more salmon-pink in hue than red. It sits in a bay at the southern edge of the south equatorial belt and, like the many other Jovian cloud features, is carried smartly across the disk as the planet spins in just under ten hours.
Steadily-held binoculars show the four main moons of Jupiter, Io, Europa, Ganymede and Callisto which change their configuration to the east and west of Jupiter from night to night, sometimes disappearing as they hide behind Jupiter or cross the disk, along with their shadows.
If Jupiter’s low elevation makes telescopic views less than sharp, this is even more the case with Saturn which rises in the south-east at our map times and is 6° lower in the sky than Jupiter as it reaches the meridian just before dawn. Saturn improves from magnitude 0.4 to 0.2 as it creeps westwards above the Teapot asterism in Sagittarius. It lies 1,392 million km away at mid-month when its oblate globe is 18 arcseconds across set within 40 by 17 arcseconds rings that have their north face inclined at 26° to our view. Look for it 4° right of the Moon on the morning of the 5th.
Less than 2° below Saturn is the globular star cluster M22, a ball of thousands of stars that lies about 10,600 light years away and formed some 12 billion years ago. At about magnitude 5.1 and visible as a hazy glow through binoculars, it was the first globular to be discovered and is brighter than M13 in Hercules, the best globular in the northern sky.
Mars lies almost 15° east of Saturn at present and rises at Edinburgh’s south-eastern horizon at 02:46 on the 1st. As it more than doubles in brightness, from magnitude -0.4 to -1.2, it also speeds 12° eastwards from Sagittarius to Capricornus so that by the 31st it rises at 01:31 and its fiery glow is unmistakable above the south-south-eastern horizon before dawn.
Catch Mars below the Moon on the morning of the 6th. Telescopically, its disk swells from 11 to 15 arcseconds as its distance falls from 126 million to 92 million km. Its approach opens the optimum window for sending probes to the planet and NASA’s InSight lander to study “marsquakes” and the Martian interior is due for launch between 5 May and 8 June.
Meteors of the Eta-Aquarids shower, debris from Comet Halley, appear until the 20th as they radiate from a point that lies low in the east for an hour or so before dawn over Scotland. The shower peaks with some moonlight interference on the 6th and brings a fine shower for watchers further south but only a handful of meteors for us.
Diary for 2018 May
Times are BST
3rd 18h Venus 7° N of Aldebaran
4th 21h Moon 1.7° N of Saturn
5th – 6th Peak of Eta Aquarids meteor shower
6th 08h Moon 2.7° N of Mars
8th 03h Last quarter
9th 02h Jupiter at opposition at distance of 658 million km
15th 13h New moon
17th 19h Moon 5° S of Venus
22nd 03h Moon 1.5° N of Regulus
22nd 05h First quarter
27th 19h Moon 4° N of Jupiter
29th 15h Full moon
This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on April 30th 2018, with thanks to the newspaper for permission to republish here.
Impressive conjunction before dawn for Mars and Saturn
The Sun climbs almost 10° northwards during April to bring us longer days and, let us hope, some decent spring-like weather at last. Our nights begin with Venus brilliant in the west and end with three other planets rather low across the south. Only Mercury is missing – after rounding the Sun’s near side on the 1st it remains hidden in Scotland’s morning twilight despite standing further from the Sun in the sky (27°) on the 29th than at any other time this year.
Edinburgh’s sunrise/sunset times change from 06:44/19:51 BST on the 1st to 05:32/20:50 on the 30th. The Moon is at last quarter on the 8th, new on the 16th, first quarter on the 22nd and full on the 30th.
Mars and Saturn rise together in the south-east at about 03:45 BST on the 1st and are closest on the following day, with Mars, just the brighter of the two, only 1.3° south of Saturn. Catch the impressive conjunction less than 10° high in the east-south-east as the morning twilight begins to brighten.
Both planets lie just above the so-called Teapot of Sagittarius but they are at very different distances – Mars at 166 million km on the 1st while Saturn is nine times further away at 1,492 million km.
Brightening slightly from magnitude 0.5 to 0.4 during April, Saturn moves little against the stars and is said to be stationary on the 18th when its motion reverses from easterly to westerly. Almost any telescope shows Saturn’s rings which are tipped at 26° to our view and currently span some 38 arcseconds around its 17 arcseconds disk.
Mars tracks 15° eastwards (to the left) and almost doubles in brightness from magnitude 0.3 to -0.3 as its distance falls to 127 million km. Its reddish disk swells from 8 to 11 arcseconds, large enough for telescopes to show some detail although its low altitude does not help.
Saturn is 4° below-left of Moon and 3° above-right of Mars on the 7th while the last quarter Moon lies 5° to the left of Mars on the next morning.
Orion stands above-right of Sirius in the south-west as darkness falls at present but has all but set in the west by our star map times. Those maps show the Plough directly overhead where it is stretched out of shape by the map projection used. We can extend a curving line along the Plough’s handle to reach the red giant star Arcturus in Bootes and carry it further to the blue giant Spica in Virgo, lower in the south-south-east and to the right of the Moon tomorrow night.
After Sirius, Arcturus is the second brightest star in Scotland’s night sky. Shining at magnitude 0.0 on the astronomers’ brightness scale, though, it is only one ninth as bright as the planet Jupiter, 40° below it in the constellation Libra. In fact, Jupiter improves from magnitude -2.4 to -2.5 this month as its distance falls from 692 million to 660 million km and is hard to miss after it rises in the east-south-east less than one hour before our map times. Look for it below-left of the Moon on the 2nd, right of the Moon on the 3rd, and even closer to the Moon a full lunation later on the 30th.
Jupiter moves 3° westwards to end the month 4° east of the double star Zubenelgenubi (use binoculars). Telescopes show the planet to be about 44 arcseconds wide, but for the sharpest view we should wait until it is highest (17°) in in the south for Edinburgh some four hours after the map times.
Venus’ altitude on the west at sunset improves from 16° to 21° this month as the evening star brightens from magnitude -3.9 to -4.2. Still towards the far side of its orbit, it appears as an almost-full disk, 11 arcseconds wide, with little or no shading across its dazzling cloud-tops. Against the stars, it tracks east-north-eastwards through Aries and into Taurus where it stands 6° below the Pleiades on the 20th and 4° left of the star cluster on the 26th. As it climbs into our evening sky, the earthlit Moon lies 6° below-left of Venus on the 17th and 12° left of the planet on the 18th.
The reason that we have such impressive springtime views of the young Moon is that the Sun’s path against the stars, the ecliptic, is tipped steeply in the west at nightfall as it climbs through Taurus into Gemini. The orbits of the Moon and the planets are only slightly inclined to the ecliptic so that any that happen to be towards this part of the solar system are also well clear of our horizon. Contrast this with our sky just before dawn at present, when the ecliptic lies relatively flat from the east to the south – hence the non-visibility of Mercury and the low altitudes of Mars, Saturn and Jupiter.
The evening tilt of the ecliptic means that, under minimal light pollution and after the Moon is out of the way, it may be possible to see the zodiacal light. This appears as a cone of light that slants up from the horizon through Venus and towards the Pleiades. Caused by sunlight reflecting from tiny particles, probably comet-dust, between the planets, it fades into a very dim zodiacal band that circles the sky. Directly opposite the Sun this intensifies into an oval glow, the gegenschein (German for “counterglow”), which is currently in Virgo and in the south at our map times – we need a really dark sky to see it though.
Diary for 2018 April
Times are BST.
1st 19h Mercury in inferior conjunction on Sun’s near side
2nd 13h Mars 1.3° S of Saturn
3rd 15h Moon 4° N of Jupiter
7th 14h Moon 1.9° N of Saturn
7th 19h Moon 3° N of Mars
8th 08h Last quarter
16th 03h New moon
17th 13h Saturn farthest from Sun (1,505,799,000 km)
17th 20h Moon 5° S of Venus
18th 03h Saturn stationary (motion reverses from E to W)
18th 15h Uranus in conjunction with Sun
22nd 23h First quarter
24th 05h Venus 4° S of Pleiades
24th 21h Moon 1.2° N of Regulus
29th 19h Mercury furthest W of Sun (27°)
30th 02h Full moon
30th 18h Moon 4° N of Jupiter
This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on March 31st 2018, with thanks to the newspaper for permission to republish here.
Elusive Mercury is second evening star alongside Venus
Orion is striding proudly across the meridian as darkness falls, but, even before the twilight dims, we have our best chances this year to spot Mercury low down in the west and close to the more familiar brilliant planet Venus.
Both evening stars lie within the same field-of-view in binoculars for much of March, so the fainter Mercury should be relatively easy to locate using Venus as a guide. Provided, of course, that we have an unobstructed horizon. Mercury never strays far from the Sun’s glare, making it the most elusive of the naked-eye planets – indeed, it is claimed that many astronomers, including Copernicus, never saw it.
Blazing at magnitude -3.9, Venus hovers only 9° above Edinburgh’s western horizon at sunset on the 1st and sets 64 minutes later. Mercury, one tenth as bright at magnitude -1.3, lies 2.0° (four Moon-breadths) below and to its right and may be glimpsed through binoculars as the twilight fades. Mercury stands 1.1° to the right of Venus on the 3rd and soon becomes a naked eye object as both planets stand higher from night to night, becoming visible until later in the darkening sky.
By the 15th, Mercury lies 4° above-right of Venus and at its maximum angle of 18° from the Sun, although it has more than halved in brightness to magnitude 0.2. The slender young Moon sits 5° below-left of Venus on the 18th and 11° above-left of the planetary pairing on the 19th. Earthshine, “the old Moon in the new Moon’s arms”, should be a striking sight over the following few evenings.
On the 22nd, the 30% illuminated Moon creeps through the V-shaped Hyades star cluster and hides (occults) Taurus’ leading star Aldebaran between 23:31 and 00:14 as they sink low into Edinburgh’s west-north-western sky.
Falling back towards the Sun, Mercury fades sharply to magnitude 1.4 by the 22nd when it passes 5° right of Venus and becomes lost from view during the following week. At the month’s end, Venus stands 15° high at sunset and sets two hours later.
The Sun climbs 12° northwards in March to cross the sky’s equator at the vernal equinox at 16:15 on the 20th, which is five days before we set our clocks forward at the start of British Summer Time. Sunrise/sunset times for Edinburgh change from 07:04/17:47 GMT on the 1st to 06:46/19:49 BST (05:46/18:49 GMT) on the 31st. The Moon is full on the 2nd, at last quarter on the 9th, new on the 17th, at first quarter on the 24th and full again on the 31st.
Orion is sinking to our western horizon at our star map times while the Plough, the asterism formed by the brighter stars of Ursa Major, is soaring high in the east towards the zenith. To the south of Ursa Major, and just reaching our meridian, is Leo which is said to represent the Nemean lion strangled by Hercules (aka Heracles) in the first of his twelve labours. Leo appears to be facing west and squatting in a similar pose to that of the lions at the foot of Nelson’s Column in Trafalgar Square.
Leo’s Sickle, the reversed question mark that curls above Leo’s brightest star Regulus, outlines its head and mane and contains the famous double star Algieba whose two component stars, both much larger than our Sun, take more than 500 years to orbit each other and may be seen through a small telescope. Regulus, itself, is occulted as they sink towards Edinburgh’s western horizon at 06:02 on the morning of the 1st.
Jupiter, easily our brightest morning object, rises at Edinburgh’s east-south-eastern horizon at 00:47 GMT on the 1st and at 23:41 BST (22:41 GMT) on the 31st, climbing to pass around 17° high in the south some four hours later. Brightening from magnitude -2.2 to -2.4, it is slow moving in Libra, being stationary on the 9th when its motion reverses from easterly to westerly. Jupiter is obvious below the Moon on the 7th when a telescope shows the Jovian disk to be 40 arcseconds wide.
If we look below and to the left of Jupiter in the south before dawn, the three objects that catch our attention are the red supergiant star Antares in Scorpius and, further from Jupiter, the planets Mars and Saturn.
Mars lies in southern Ophiuchus, between Antares and Saturn, and is heading eastwards into Sagittarius and towards a conjunction with Saturn in early April. The angle between the two planets falls from 17° to only 1.5° this month as Mars brightens from magnitude 0.8 to 0.3 and its distance falls from 210 million to 166 million km. Mars’ disk swells from 6.7 to 8.4 arcseconds, becoming large enough for surface detail to be visible through decent telescopes. Sadly, Mars (like Saturn) is so far south and so low in Scotland’s sky that the “seeing” is unlikely to be crisp and sharp.
Incidentally, on the morning of the 19th Mars passes between two of the southern sky’s showpiece objects, being a Moon’s breadth below the Trifid Nebula and twice this distance above the Lagoon Nebula. Both glowing clouds of hydrogen, dust and young stars appear as hazy patches through binoculars but are stunning in photographs.
Saturn, creeping eastwards just above the Teapot of Sagittarius, improves from magnitude 0.6 to 0.5 and has a 16 arcseconds disk set within its superb rings which span 37 arcseconds at midmonth and have their northern face tipped towards us at 26°. The waning Moon lies above-left of Mars on the 10th and close to Saturn on the 11th.
Diary for 2018 March
Times are GMT until March 25, BST thereafter.
1st 06h Moon occults Regulus (disappears at 06:02 for Edinburgh)
2nd 01h Full moon
4th 14h Neptune in conjunction with Sun
5th 18h Mercury 1.4° N of Venus
7th 07h Moon 4° N of Jupiter
9th 10h Jupiter stationary (motion against stars reverses from E to W)
9th 11h Last quarter
10th 01h Moon 4° N of Mars
11th 02h Moon 2.2° N of Saturn
15th 15h Mercury furthest E of Sun (18°)
17th 13h New moon
18th 01h Mercury 4° N of Venus
18th 18h Moon 8° S of Mercury
18th 19h Moon 4° S of Venus
20th 16:15 Vernal equinox
23rd 00h Moon occults Aldebaran (23:31 to 00:14 for Edinburgh)
24th 16h First quarter
25th 01h Start of British Summer Time
27th 02h Moon 1.8° S of star cluster Praesepe in Cancer
31st 14h Full moon
This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on February 28th 2018, with thanks to the newspaper for permission to republish here.
Saturn at its best as noctilucent clouds gleam
The first day of June marks the start of our meteorological summer, though some would argue that summer begins on 21 June when (at 05:25 BST) the Sun reaches its most northerly point at the summer solstice.
Sunrise/sunset times for Edinburgh vary surprisingly little from 04:35/21:47 BST on the 1st, to 04:26/22:03 at the solstice and 04:31/22:02 on the 30th. The Moon is at first quarter on the 1st, full on the 9th, at last quarter on the 17th and new on the 24th.
The Sun is already so far north that our nights remain bathed in twilight and it will be mid-July before Edinburgh sees its next (officially) dark and moonless sky. This is a pity, for the twilight swamps the fainter stars and, from northern Scotland, only the brightest stars and planets are in view.
If we travel south, though, the nights grow longer and darker, and the spectacular Milky Way star fields in Sagittarius and Scorpius climb higher in the south. From London at the solstice, for example, official darkness, with the Sun more than 12° below the horizon, lasts for three hours, while both Barcelona and Rome rejoice in more than six hours.
It is in this same area of sky, low in the south in the middle of the night, that we find the glorious ringed planet Saturn. This stands just below the full moon on the 9th and is at opposition, directly opposite the Sun, on the 15th when it is 1,353 million km away and shines at magnitude 0.0, comparable with the stars Arcturus in Bootes and Vega in Lyra. The latter shines high in the east-north-east at our map times and, together with Altair in Aquila and Deneb in Cygnus, forms the Summer Triangle which is a familiar feature of our nights until late-autumn.
Viewed telescopically, Saturn’s globe appears 18 arcseconds wide at opposition while its rings have their north face tipped 27° towards us and span 41 arcseconds. Sadly, Saturn’s low altitude, no more than 12° for Edinburgh, means that we miss the sharpest views although it should still be possible to spy the inky arc of the Cassini division which separates the outermost of the obvious rings, the A ring, from its neighbouring and brighter B ring.
Other gaps in the rings may be hard to spot from our latitudes – we can only envy the view for observers in the southern hemisphere who have Saturn near the zenith in the middle of their winter’s night. For us, Saturn is less than a Moon’s breadth further south over our next two summers, while the ring-tilt begins to decrease again.
On the other hand, we can sympathize with those southern observers for most of them never see noctilucent clouds, a phenomenon for which we in Scotland are ideally placed. Formed by ice condensing on dust motes, their intricate cirrus-like patterns float at about 82 km, high enough to shine with an electric-blue or pearly hue as they reflect the sunlight after any run-of-the-mill clouds are in darkness. Because of the geometry involving the Sun’s position below our horizon, they are often best seen low in the north-north-west an hour to two after sunset, shifting towards the north-north-east before dawn – along roughly the path taken by the bright star Capella in Auriga during the night.
Jupiter dims slightly from magnitude -2.2 to -2.0 but (after the Moon) remains the most conspicuous object in the sky for most of the night. Indeed, the Moon lies close to the planet on the 3rd – 4th and again on the 30th. As the sky darkens at present, it stands some 30° high and just to the west of the meridian, though by the month’s end it is only half as high and well over in the SW. Our star maps plot it in the west-south-west as it sinks closer to the western horizon where it sets two hours later.
The giant planet is slow-moving in Virgo, about 11° above-right of the star Spica and 3° below-left of the double star Porrima. As its distance grows from 724 million to 789 million km, its disk shrinks from 41 to 37 arcseconds in diameter but remains a favourite target for observers.
The early science results from NASA’s Juno mission to Jupiter were released on 25 May. They reveal the atmosphere to be even more turbulent than was thought, with the polar regions peppered by 1,000 km-wide cyclones that are apparently jostling together chaotically. This is in stark contrast to the meteorology at lower latitudes, where organized parallel bands of cloud dominate in our telescopic views. In addition, the planet’s magnetic field is stronger and more lumpy than was expected. Juno last skimmed 3,500 km above the Jovian clouds on 19 May and is continuing to make close passes every 53 days.
Both Mars and Mercury are hidden in the Sun’s glare this month, the latter reaching superior conjunction on the Sun’s far side on the 21st.
Venus, brilliant at magnitude -4.3 to -4.1, is low above our eastern horizon before dawn. It stands at its furthest west of the Sun in the sky, 46°, on 3 June but it rises only 78 minutes before the Sun and stands 10° high at sunrise as seen from Edinburgh. By the 30th, it climbs to 16° high at sunrise, having risen more than two hours earlier. Between these days, it shrinks in diameter from 24 to 18 arcseconds and changes in phase from 49% to 62% illuminated. It lies left of the waning crescent Moon on the 20th and above the Moon on the following morning.
This is a slightly-revised version of Alan’s article published in The Scotsman on May 31st 2017, with thanks to the newspaper for permission to republish here.
Jupiter rules our April nights
Venus dominated our evening sky for the first quarter of 2017, but it is now Jupiter’s turn in the spotlight. The conspicuous giant planet lies directly opposite the Sun in the sky on the 7th so that it rises in the east at sunset, reaches its highest point in the south in the middle of the night and sets in the west at sunrise.
Our charts show it in Virgo to the east of south as Taurus and Orion dip beneath the western horizon and the Plough looms overhead, stretched out of its familiar shape by our map projection. Regulus in Leo is in the south-west and almost level with Arcturus in Bootes in the south-east. Vega in Lyra and Deneb in Cygnus are beginning their climb in the north-east.
Sunrise/sunset times for Edinburgh change from 06:43/19:51 BST on the 1st to 05:31/20:50 on the 30th. The Moon is at first quarter on the 3rd, full on the 11th, at last quarter on the 19th and new on the 26th.
Venus rises only a little more than one hour before sunrise and, though brilliant at magnitude -4.2, may be difficult to spot low in the east before dawn. However, the other inner planet, Mercury, remains nicely placed in the evening and stands furthest east of the Sun (19°) on the 1st.
Thirty minutes after Edinburgh’s sunset on that day, Mercury is 12° high in the west and shines at magnitude 0.0. It should be possible to spy it through binoculars and eventually with the unaided eye as the twilight fades and the planet sinks to set another 96 minutes later. By the 8th, though, it is a couple of degrees lower and a quarter as bright at magnitude 1.6 as it is engulfed by the twilight. Inferior conjunction on the Sun’s near side occurs on the 20th.
Mars, magnitude 1.5 to 1.6 and above and to Mercury’s left at present, tracks east-north-eastwards this month to pass 5° below the Pleiades on the 15th and a similar distance left of the star cluster on the 26th. By then it sets late enough to be plotted near our north-western horizon at the star map times.
Its opposition means that Jupiter is at its brightest and closest, shining more brightly than any star at magnitude -2.5 and a distance of 666 million km. It lies 6° north-west (above-right) of Virgo’s leading star Spica as the month begins and tracks 3.7° westwards during April to pass 10 arcminutes or a third of a Moon’s-width south of the fourth magnitude star Theta Virginis on the 5th.
Jupiter lies close to the full Moon on the night of the 10th-11th when the Jovian disk appears 44 arcseconds wide if viewed telescopically, one fortieth as wide as the Moon.
Jupiter’s clouds are arrayed in bands that lie parallel to its equator, the dark ones called belts and the intervening lighter hued ones called zones. There are numerous whirls and spots, the most famous being the Great Red Spot in the southern hemisphere. The planet spins in under ten hours, so a resolute observer might view the entire span of its clouds in a single April night. The four main moons, visible through decent binoculars and easy through a telescope, lie on each side of the disk and change their configuration from night to night.
The beautiful planet Saturn rises in the south-east less than three hours after our map times and is the brightest object (magnitude 0.4 to 0.3) less than 15° above Edinburgh’s southern horizon before dawn. It is a shame that its low altitude means that we miss the sharpest and most impressive views of it rings which span 39 arcseconds in mid-April, and are tilted at 26° around its 17 arcseconds disk. After appearing stationary on the 6th, Saturn begins to creep westwards against the stars of Sagittarius – look for it below and left of the Moon on the 16th and right of the Moon on the 17th.
It is not often that I advertise the annual Lyrids meteor shower. As one of the year’s lesser displays, it yields only some 18 meteors per hour at best, all of them swift and some leaving glowing trains in their wake as they diverge from a radiant point to the right of Vega. The event lasts from the 18th to the 25th and peaks on the 22nd when moonlight should not interfere unduly this year. The Lyrid meteoroids were released by Comet Thatcher, last seen in 1861.
Bright comets have been rare of late, but fainter ones are observed frequently. One such has the jaunty name of comet 41P/Tuttle–Giacobini–Kresák and takes 5.4 years to orbit between the paths of Jupiter and the Earth. It passes within 21 million km of us on the 1st as it nears perihelion, its closest point to the Sun, on the 12th. I glimpsed it through binoculars from a superb dark-sky site at Kielder Forrest, Northumberland, last week when it was a diffuse seventh magnitude smudge close to Merak, the southern star of the Pointers in the Plough.
Although its path is not depicted on our chart, the comet is poised to sweep close to three of the stars identified in Draco, between the Plough and Polaris, the Pole Star. It passes 0.6° north of Thuban on the night of the 2nd-3rd, 1.5° south-west of Eta on the 11th (sadly, in full moonlight) and 0.6° west of Beta on the 18th-19th. During past perihelia, it has been seen to flare by several magnitudes for a few days at a time, so, if we are lucky, it may reach naked-eye visibility. | 0.928711 | 3.477998 |
We all know that space can be a dangerous place. Many safety measures are put in place by space agency scientists so astronaut’s lives are protected and mission success can be assured. Generally, some degree of certainty can be insured in near Earth orbit, protecting astronauts onboard the International Space Station and Shuttle missions, as most activities go on within the Earth’s protective magnetosphere. But in the future, when we establish a colony on the Moon and Mars, how will human life be protected from the ravages of solar radiation? In the case of Mars, this will be of special interest as should something go wrong, colonists will be by themselves…
Solar energy is essential to life on Earth. Without it, we wouldn’t be here. In space, this friendly source of energy suddenly becomes our enemy. Highly energetic particles in the form of ions (i.e. atoms of solar elements stripped of most of their electrons) are generated by the Sun and ejected into space during periods of intense solar activity. These intense periods of solar activity are known as “solar maxima”, occurring approximately every 11 years as a part of the solar cycle. Although we can predict the periods of the solar cycle, we cannot predict when the Sun might launch a devastating solar flare or increase its solar wind output. Astronauts caught in a solar “ion storm” will receive high doses of radiation, putting them at risk of short term radiation poisoning and long term health problems.
Astronauts in Earth orbit are comparatively protected from the worst of the solar radiation as the energetic ions will be deflected by the Earth’s strong magnetic field. But future manned missions to Mars are at an obvious risk as Mars does not have a significant magnetic field and has a very tenuous atmosphere. So what can be done for our future colonists?
Research is afoot to protect long-haul travel through space (i.e. the six month transit between the Earth and Mars), but colonies will need to be warned about the onset of a solar storm should a long-term Mars base be established. Taking the lead from the recent real-time early warning system established with the Solar and Heliospheric Observatory (SOHO), sitting in the Earth-Sun First Lagrangian Point, 1.5 million km away from the Earth in direct line of sight of the Sun, the concept of an early warning system for Mars could be (inexpensively) set up.
Like Earth, Mars has its own Lagrangian points with the Sun. Currently there are no man-made satellites in L1 (Mars) or L2 (Mars) orbit, but it is conceivable that these islands of gravitational stability may be used to greatly benefit future Mars colonies.
The SOHO mission receives the signal that solar ions are approaching Earth an hour before atmospheric impact. This not only provides excellent diagnostic data, but also gives advanced warning to companies and organizations that the Earth is 60 minutes away from experiencing an increase in solar radiation. Emergency procedures can be enacted accordingly, possibly saving delicate satellites and astronauts.
A simple, cost effective probe may be inserted into the Mars-Sun L1 point. This probe needn’t be as sophisticated as SOHO, it just needs to monitor the flux of energetic particles travelling toward Mars. Akin to a “flag” system on a patrolled beach (red for “dangerous”, no swimming. Green for “safe”, water is safe), Mars settlers could have advanced warning of an incoming flood of ions from the Sun. If constantly measured by a particle detector on the probe at the L1 point, various stages of danger levels may be used to indicate to settlers unprotected on the surface of what severity of risk they are in. Surface “walkabouts” may be tightly restricted by such a system.
The Mars L1 time-lag problem
The distance between Earth’s L1 point and the planet is approximately 1.5 million km. This provides information on the solar wind particles approximately 1 hour before they are received on Earth. Mars is a less massive planet than the Earth; therefore, Mars’ L1 point will be closer to the planet than the Earth’s.
Reaching a logical conclusion, assuming solar particles are travelling at the same velocity in near-Mars orbit as with near-Earth orbit, a Mars early warning system of the design outlined above will be less effective than the terrestrial version. So, how much time will the Mars early warning system provide to colonists from detection (at L1) to impact (at Mars’ surface)?
Using the equation from Lagrangian point calculations:
where r is the distance of L1 from Mars, R is the distance between the bodies and MM and MS are the masses of Mars and the Sun respectively.
Using R = 2.28 × 1011 meters, MM = 6.4191×1023 kg and MS = 1.98892×1030 kg, we arrive at a value of 1.08 million km, 72% of the distance of Earth’s 1.5 million km.
Now, keeping the assumption that it will approximately take solar ions 60 minutes to travel 1.5 million km (from Earth’s L1 point to Earth), the time from L1 to Mars’ surface = 60 × 72% = 43.2 minutes.
Although 43 minutes is less than the warning time Earth-based solar wind probes are able to provide, this is not a great reduction in lag time, and would still greatly benefit the humans unprotected from solar radiation on the surface of Mars. | 0.809689 | 3.470012 |
Tides are created by the gravitational attraction of the moon and the sun, with the moon having the much larger effect. The tides can be predicted because of the predictability of the moon's orbit around the earth. The moon takes 24 hours and 50 minutes to orbit the earth, and in this time two high tides and two low tides will rise and fall on the seashore. The time and height of each tide will be repeated in approximately 19 years.
The rise and fall is caused by two waves or bulges on the surface of the sea, one beneath the pull of the moon on one side of the earth, the other away from it on the other side of the earth. This wave, measuring 20,000 kilometers from crest to crest, is the world's longest wave.
Everything on earth, including the atmosphere and the earth's crust is lifted by the tidal forces. Even our own bodies are affected, weighing about 1/6,000,000 less when both sun and moon are overhead.
The tide-wave is fixed in position by the force of the moon's gravity, and the earth rotates beneath it. When the edge of a continent slips beneath the crest of the wave, the sea level along the shore is raised causing a high tide. When the shore then slips beneath the following trough in the wave, the sea level falls, causing low tide. In mid ocean, the height of this wave is relatively low, but when the crest encounters the coastal waters of inlets or bays, its energy is confined by the shallow waters and narrowing channels and as a result the height of the wave increases.
The difference between the high tide level and the following low tide level - the tidal range - can measure anywhere from a few centimetres to several metres. | 0.824791 | 3.165224 |
Where Cosmic Rays Come From
|HESS gamma-ray image of supernova remnant
European astronomers have produced the first image of an object using high energy gamma rays – the most penetrating form of radiation known. The image is of a supernova remnant called RX J1713.7-3946, which exploded 1,000 years ago.
Over time, a ring of material has expanded to twice the diameter of the Moon in the sky. If you had gamma ray eyes, you would be able to see a large ring in the sky every night. This also helps solve a 100 year mystery about the origin of cosmic rays; the remnant seems to be acting as a particle accelerator.
During Earth’s earliest history, its surface also was bombarded by high-energy particles associated with solar activity (from a solar wind that was enhanced during early history and from solar flares) and galactic cosmic rays, and possibly from nearby supernovae and events associated with gamma-ray bursts. This bombardment must have had deleterious effects on life at the Earth’s surface, and may have severely affected the formation and earliest evolution of life.
The latest result, published in the Journal Nature on November 4th, was carried out using the High Energy Stereoscopic System (H.E.S.S.), an array of four telescopes, in Namibia, South-West Africa. Dr Paula Chadwick of the University of Durham said "This picture really is a big step forward for gamma-ray astronomy and the supernova remnant is a fascinating object. If you had gamma-ray eyes and were in the Southern Hemisphere, you could see a large, brightly glowing ring in the sky every night."
|Dr. John Horack, who led the assembly, testing and calibration program for the gamma ray burst experiment on NASA’s Compton Gamma-Ray Observatory
Credit: D. Rezabek
Professor Ian Halliday, CEO of the UK-based Particle Physics and Astronomy Research Council said "These results provide the first unequivocal proof that supernovae are capable of producing large quantities of galactic cosmic rays – something we have long suspected, but never been able to confirm."
To put the finding in perspective, Astrobiology Magazine had the opportunity to talk with John Horack, who led the assembly, testing and calibration program for the gamma ray burst experiment on NASA’s Compton Gamma-Ray Observatory.
Astrobiology Magazine (AM): Have people been proposing a gamma-ray telescope for a long time, or is this possible now with newer technologies?
John Horack (JH): There have been gamma-ray telescopes in the past, for example the COMPTEL experiment aboard NASA’s Compton Gamma-Ray Observatory imaged the cosmos in gamma rays for nearly 10 years from low earth orbit. The breakthrough here, as I understand it, is that we are now making gamma ray images from the ground.
AM: Presumably, seeing in a small wavelength window highlights the higher energy processes in the sky. Does it make sense to look at gamma ray bursts with a gamma ray telescope?
JH: Gamma ray bursts are very different from supernova remnants, of course, but yes, it makes sense to try — and scientists have been trying since their discovery in 1967. The problem with gamma ray bursts is that you do not know where the next one is coming from, and therefore trying to guess by pointing your telescope is kind of a shot in the dark. Early gamma-ray burst experiements used very wide fields fo view, and found the direction to bursts by working out the direction by studying the time difference in detection by widely-separated experiments in space.
Later, experiements like BATSE on the Compton GRO used detectors that could see the entire sky at once, thereby capturing any gamma-ray burst of sufficient strength and determining the direction by the relative brightness in each of the eight detectors pointed in different directions. The Dutch-Italian BeppoSAX actually was able to catch gamma-ray bursts in real time by quickly slewing the telescope on the spacecraft after a detection.
Today, experiments like the High Energy Transient Experiment (HETE) and SWIFT offer the best chances we’ve ever had to catch a gamma ray burst "in the act" either by detecting the gamma-ray or x-ray emission as the burst is occurring, or shortly after it has begun.
|HESS Gamma Ray Telescope. Cherenkov light develops within an air shower. Because the particle moves faster than the speed of light in air, there is a sonic boom or shock wave, which sends out a flash of blue light in the direction of the primary gamma quantum and lasts a few billionths of a second. This happens about ten kilometers (6.3 miles) above the earth’s surface.
Credit: Hess Collection
AM: Because atmospheres shield gamma rays, could such gamma telescopes be turned to closer objects like Venus or Titan to pick off novel features of their atmospheres as opaque in this wavelength?
JH: The Earth’s atmosphere does prevent gamma-ray radiation from reaching the ground, and gamma-rays are usually associated with far more energetic objects such as black-holes, neutron stars, supernovae, and quasars. Turning a space-based gamma-ray telescope at a planet is not terribly useful, since these planets are "dark" in gamma-rays, and their angular sizes as seen from the Earth are incredibly small compared to the resolution of a gamma-ray telescope.
In gamma-rays, the Sun isn’t even the brightest object in the sky. The Crab Nebula, Cygnus X-1, and a host of other sources typically are brighter in gamma-rays.
The universe is just far too plentiful in exotic, energetic, and explosive phenomena to spend time trying to detect gamma-rays from Venus. One thing that was learned from BATSE, however, is that thunderstorms on Earth do create large but short-lived flashes of intense, upward-moving gamma radiation observable from low-earth orbit. This was a total surprise, and one of those kinds of discoveries that happen in science that one would never have predicted prior to the launch of BATSE in 1991.
AM: One question that is curious about HESS and its relation to gamma ray detectors of the past, is the basis for having a space telescope. How does HESS see such objects when the atmosphere is opaque–is it looking for byproducts in the upper atmosphere, like Cerenkov radiation, thus making it more of a Cerenkov eye, not a true gamma eye?
JH: HESS does not detect the gamma-rays directly, since they do not reach the ground. So yes, it is detecting the evidence of a gamma-ray, not the gamma-ray itself.
|Crab Nebula in X-rays showing its main central jet.
This evidence is called Cerenkov radiation, produced when an object such as a high-energy particle moves faster than the speed of light in the medium it is travelling through. Please note, this speed is NEVER faster than the speed of light in a vacuum. As an example, the speed of light in water is slower than the speed of light in a vacuum. Nothing can travel faster than the speed of light in a vacuum. But if you move an electron through water at a speed less than the vacuum speed, but more than water velocity, it will emit radiation that can be detected, called Cerenkov radiation. This is what HESS is detecting, from particles created through interactions between the incoming gamma-rays and the upper atmosphere.
AM: The origin of cosmic rays are being attributed to supernova, because of a glowing ring. Aren’t there theories that cosmic rays are just accelerated in the plasma of a supernova, not originating there?
JH: The origin of cosmic rays is a long-standing question, and the prediction of an association between cosmic rays and supernovae dates back to the late 1930’s. So this result helps put that question to bed, and may allow scientists to get on with understanding the detailed physics of how the production takes place in this environment.
AM: Any ideas for where to point this next, like at our Sun or even burst afterglows?
JH: I’d love to see some Northern hemisphere objects, such as the Crab Nebula, Cygnus X-1, or the possibility of detection of things like X-ray transients from the Galactic Center. In fact, this is one of the most interesting things about the high-energy sky: it changes very frequently, and the brightest object in the sky today, might not be the brighest object in the sky tomorrow.
Things can change on timescales of minutes, days, or weeks.
The HESS telescopes are ten times more sensitive than earlier Cherenkov telescopes. Each HESS collector has a diameter of twelve meters (~40 feet) and 380 individual round mirrors that make up a light-collecting surface area of 108 square meters (~1000 sq. ft.). The camera enables exposure times of a mere one hundred millionth of a second. The HESS acronym alludes to the Austrian physicist Viktor Franz Hess (1883-1964) who discovered cosmic rays during ten balloon flights between 1911 and 1913. In 1936, he was awarded the Nobel Prize for Physics.
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Inevitability Beyond Billions | 0.931237 | 3.905188 |
A Spiral Galaxy is Visited by a Trojan War Hero
Creator: Wide-field Infrared Survey Explorer, Berkeley, CA, USA
Its a bird! Its a plane! Nope, its an asteroid tracking its way across the sky with a beautiful spiral galaxy in the background. In the center of this new mosaic image captured by NASAs Wide-field Infrared Survey Explorer (WISE) is the galaxy Messier 74, with its spiral arms seen face-on. The bright reddish object moving across the lower right part of the image is the much closer asteroid 3540 Protesilaos, seen at different points in its orbit around the Sun. WISE observed and detected this previously known asteroid a total of ten times, although only a few of those frames were used in this mosaic.
Also known as NGC 628, the Messier 74 galaxy is between 24.5 and 36 million light-years away, and has a diameter of about 100,000 light-years. It is suspected to have a black hole at its center, with a mass equal to 10,000 Suns. It is one of only a handful of known black holes with masses intermediate between the relatively smaller ones that form from collapsing stars and the supermassive black holes millions of times more massive than the sun, which are more typically found at the centers of galaxies Although it is called a Messier object, Messier 74 was actually discovered by Pierre Mechain in 1780, who then told his friend Charles Messier about it. As one of the dimmest of all Messier objects, this galaxy is a challenge for amateur astronomers to see in visible light, but the WISE cameras captured it clearly in infrared light.
The colors used in this image represent different wavelengths of infrared radiation. Blue and cyan represent light at 3.4 and 4.6 microns, respectively. These colors show both nearby stars inside the Milky Way Galaxy and the combined light of billions of stars that make up Messier 74. Green and red represent light from 12 and 22 microns, respectively. These colors show light from cooler objects and material. Dust in star-forming regions in Messier 74 traces its spiral structure. The coolest object in the picture is the asteroid 3540 Protesilaos.
This asteroid was first seen in 1973 by the German astronomer Freimut Brngen, who discovered more than 500 asteroids while he was researching galaxies. At the time that WISE observed 3540 Protesilaos, it was at a distance of 772 million kilometers from Earth (480 million miles, or about 43 light-minutes). It is classified as a Jupiter Trojan minor planet, which are small rocky bodies that share the same orbit around the Sun as the planet Jupiter. Based on the infrared observations, the WISE team estimates the asteroid to be about 90 kilometers (56 miles) across and to reflect only a few percent of the light that lands on it, which makes it about as dark as coal.
By convention, Trojan asteroids are named after the heroes from the Trojan War. In this case, asteroid 3540 is named after the hero Protesilaos. According to Greek mythology, Protesilaos was the first Greek to set foot on Trojan land during the war. Unfortunately for him, there was a prophecy that the first soldier in the war to step onto land from a battle ship would die. The prophecy quickly came true and Protesilaos was killed by the Trojan hero, Hector.
Image Use Policy: Pulic Domain
- Image Type
- Object Name
- Messier 74 • M74 • NGC 628
- Subject - Local Universe
- Galaxy » Type » Spiral
- Galaxy » Activity » Normal
|WISE||Infrared (Near-IR)||3.4 µm|
|WISE||Infrared (Near-IR)||4.6 µm|
|WISE||Infrared (Mid-IR)||12.0 µm|
|WISE||Infrared (Mid-IR)||22.0 µm| | 0.830987 | 3.776688 |
The planet Mercury is the closest world to the Sun, and lies in a region of the solar system inhabited by rocks from comets that that never made a safe passing around our parent star. Also leftover debris from the origin of the Sun's family. In this month's program I present a Guide to Mercury.
13 Jun 2017
Jupiter formed in a geologic blink. Its rocky core coalesced less than a million years after the beginning of our Solar System, scientists reported Monday in the Proceedings of the National Academy of Sciences. Within another 2 or 3 million years, that core grew to 50 times the mass of Earth.
Scientists have previously built computer models of the birth of Jupiter. But this study "is the first time that we can say something about Jupiter based on measurements done in the lab," said study co-author Thomas Kruijer, a researcher at the Lawrence Livermore National Laboratory in California.
To probe the planet's creation, experts sampled extra-terrestrial material that happens to land on Earth - ancient meteorites.
Our Solar System began as a disk of dust and gas 4.6 billion years ago. Of the planets, first came the gas giants, followed by such rock-and-metal terrestrial worlds as Earth. Jupiter is the biggest of the brood.
Despite being mostly gas by bulk, it's more than 300 times the mass of Earth. For that reason astronomers suspect the planet was the oldest, able to scoop up more material out of the disk before its younger siblings appeared.
The new study supports the idea of a firstborn Jupiter. When Jupiter formed, the growing planet swept up a great swath of gas and dust as it circled the sun.
What's more, it acted as a barrier to shield the inner Solar System from wayward meteorites. When the Solar System was about 1 million years old, Jupiter's gravity was strong enough to prevent rocks from crossing beyond its orbit, like a club bouncer who forces latecomers to wait on the sidewalk.
"At about 1 million years, you have Jupiter getting big enough to cut off the inner Solar System from the outer Solar System," said Brown University's Brandon Johnson, a planetary scientist who was not involved with the new research.
Then, when the Solar System was around 4 million years old, Jupiter grew to about 50 Earth masses and headed toward the sun. This lowered the bouncer's velvet rope, allowing the outer asteroids to mix with the inner rocks.
Today, they're jumbled together in a single belt, which exists between Jupiter and Mars. Rocks from this mixture land on Earth, where scientists such as Kruijer can study them.
The new study adds evidence to the idea that Jupiter temporarily split the population of meteorites in the Solar System in two: those between Jupiter and the Sun, and those beyond Jupiter.
If a pair of inner and outer space rocks landed in your front yard, and you picked them up after they cooled down and the dust settled, you wouldn't be able to spot a difference.
But Kruijer and his colleagues can measure specific chemical signatures in meteorites - which reveal not only the rocks' age but which of the two groups they once belonged to.
It was only recently that technological advances allowed scientists to measure the differences in the two, Kruijer said.
The meteorite groups separated around 1 million years after the Solar System formed, and stayed apart until about 4 million years post-formation, according to the new analysis. Crucially, the two populations existed simultaneously for a few million years.
"It cannot be a temporal change. It must be a spatial separation," Kruijer said.
Something must have kept them apart. The most likely culprit, the authors of the study say, is a young Jupiter. "It's hard to think of any other possibility," he said.
"This is interesting work and presents an interesting result, which conforms well with our existing understanding," said Konstantin Batygin, a planetary astrophysicist at the California Institute of Technology who was not involved with the research. "It may very well be what had happened."
Planetary scientists are like detectives, Batygin said, scouring a scene for hints about what transpired.
"In a crime scene it's the little splatters of blood on the ceiling," he said, "that will tell you more than the dismembered limbs."
In this analogy the planets are the chopped limbs and the meteorites the bloody spray. But, as with hunting for murder clues, he added, "there's always room for doubt with these types of problems."
It might be that the structure of the early disk kept the meteorite groups isolated, said Kevin Walsh, an astronomer at Southwest Research Institute in Colorado who was not involved with this work.
"The key point the authors make is that Jupiter must form to keep these asteroid reservoirs separate while they form," he said in an email.
"It is possible that we have a naïve understanding of the way asteroid building blocks could move in an early Solar System, and that a Jupiter mass planet isn't necessary."
But such an early Jupiter jibes with other ideas about the early Solar System.
One concept, called the grand tack hypothesis, casts Jupiter as a wanderer. In the grand tack hypothesis, first proposed by Walsh and other scientists in 2011, Jupiter began to barrel toward the centre of the Solar System.
That was, until Saturn formed, pulling Jupiter backward. This pendulous wrecking-ball motion could be responsible for, among other things, the mixing of the meteorite groups into one belt.
And it's likely that this young and massive Jupiter is responsible for a small Earth with a thin atmosphere. "We occupy a somewhat strange world, galactically speaking," Batygin said.
Earth, which formed about 100 million years after the solar nebula, lacked the gravity for a thick "nasty hydrogen helium atmosphere" found on other worlds.
Thank Jupiter for sucking up most of that material.
Exoplanet hunters looking at other star systems have found several super-Earths, planets larger than Earth but smaller than gas giants like Neptune. Few exoplanets are as small as two Earths and exist in the habitable zone of their star.
Kruijer speculated that the young Jupiter is the reason our Solar System does not have any super-Earths close to our star.
In this light Jupiter is a pillar of the Solar System. "Even in its infancy, Jupiter really controlled the dynamics and evolution of the Solar System," Johnson said.
"It's the biggest thing there is. Even at a million years it's changing the way that our Solar System looked."
12 Jun 2017
THE MOONS OF THE PLANETS MARS, JUPITER AND SATURN DURING JUNE 2017
Please click on the images to enlarge
Comet C/2015 V2 Johnson is at perihelion today at a distance of just over 152 million miles from the Sun. The ‘green’ comet is visible in a pair of 10x50 binoculars, and can be found in the constellation of Bootes, before moving south into Virgo on 15 June. RA 14h 24m 24.8s DEC +07 13’ 27”.
Today THE MOON lies in the constellation of Sagittarius RA 20h 57m33s Dec -15 56’ 55” Lunation 19.21 days, illuminated 82.6% Libration, Position Angle -17.8° Latitude -00° 42’ in Longitude -05h 56m.
Today MERCURY is visible in the morning RA 04h 50m 28.7s Dec +22° 18’ 35” Mag -2.0 Diameter 5.28” Phase 0.930
Today Venus (Mag ‒4.4) is also visible in the morning sky. RA 2h 24m 47.8s Dec +11° 35’ 04” Diameter 20.84” Phase 0.56.
Today MARS (Mag +1.7) lies in the constellation Gemini close to the open cluster M35 RA 06h 27m 05.7” Dec +24° 13’ 45” Diameter 3.8”. The planet is visible in the west after sunset.
The Asteroid CERES was in conjunction with the Sun on 6 June
Juno (Mag +10) Constellation Scutum RA 18h 50m 11s Dec –04 52’ 21”
Today Jupiter (Mag‒2.2) lies in the constellation of Virgo with the nice double star Gamma-Virginis --- Porrima --- to the upper right. RA 12h 50m 53.9s Dec -03° 57’ 19” Diameter 39.9.” The longitude of the Great Red Spot is 270 degrees (System II) and will be visible on these dates.
Today Saturn (Mag 0.0) lies in the constellation of Ophiuchus RA 17h 36m 45.5s Dec -21° 58’ 16” Diameter 18.38”
Today Uranus (Mag +5.9) lies close to the star Omicron Piscium RA 01h 43m 04s Dec+10° 03’ 56.2”
Today Neptune (Mag +7.9) lies in the constellation Aquarius (Transit 05h 40m UT) RA 23h 03m 24” Dec -07 01’ 20.4”
10 Jun 2017
All times are given in UT ‘Universal Time’
Comet C/2015 V2 Johnson is visible in a pair of 10x50 binoculars, and can be found in the constellation of Bootes, and moves south into Virgo on 15 June.
RA 14h 26m 42.2s
DEC +07 13’ 21”.
In addition, comet 289/P Blanpain Mag +20 is at opposition. It lies in the constellation of Ophiuchus just below the planet Saturn.
The Asteroid 1674 Groeneveld (Mag 16.9) Occults the 6.4 Mag star HIP 42516 which can be seen by amateur astronomers in Brazil and Peru. RA 08h 40m Dec -20° 00’ 27.6”
The Apollo class Asteroid 2017 KF3 (Mag 21) flies by the Earth at a distance of about 3 million miles. The Amor class Asteroid 397 Vienna (1894 BM) also flies by the Earth today at a distance of 161,650 million miles.
Today THE MOON lies in the constellation of Sagittarius RA 19h 16m35s Dec -19 06’ 55” Lunation 17.21 days, and is at minimum Libration (Size 5.5°) Position Angle 128° Latitude -03° 14’ Longitude –03 50’.
Today Mercury is visible in the morning sky 5° north of Aldebaran RA 04h 33m 04.2s Dec +21° 23’ 41” Mag -2.0 Diameter 5.38” Phase 0.893
Today Venus is at Aphelion. The planet (Mag -4.4) is also visible in the morning sky. RA 2h 16m 54.7s Dec +10° 58’ 10” Diameter 21.71” Phase 0.540.
Today Mars (Mag +1.7) lies in the constellation Gemini close to the open cluster M35 RA 06h 21m 18.2” Dec +24° 16’ 28” Diameter 3.65”. The planet is visible in the west after sunset.
The Asteroid Ceres was in conjunction with the Sun on 6 June
The Asteroid Juno (Mag +10) lies in the Constellation Scutum RA 18h 57m 16s Dec –04 54’ 11”
Today Jupiter (Mag‒2.2) lies in the constellation of Virgo with the nice double star Gamma-Virginis --- Porrima --- to the upper right. RA 12h 50m 50.2s Dec -03° 56’ 21” Diameter 39.9”
Today Saturn (Mag 0.0) lies in the constellation of Ophiuchus RA 17h 37m 23.6s Dec -21° 58’ 29” Diameter 18.38”
Today Uranus (Mag +5.9) lies close to the star Omicron Piscium RA 01h 42m 47s Dec+10° 02’ 19.3”
Today Neptune (Mag +7.9) lies in the constellation Aquarius (Transit 05h 40m) RA 23h 03m 23.7” Dec -07 01’ 21.3”
8 Jun 2017
One of the largest and most famous annual meteor showers may have taken a sinister turn, as the risk of the shower heralding a large asteroid on a track to smash into Earth and cause untold devastation has become more and more significant, according to Czech astronomers.
The Astronomical Institute of the Czech Academy of Sciences came to their grim conclusions after observing the Taurid meteor shower, which appears twice a year in the night sky: once during the early summer and once around Halloween.
A meteor shower occurs when Earth's movements send it through a stream of cosmic debris. Typically, the meteoroids that would hit Earth either disintegrate or are shrunken to a tiny size by Earth's atmosphere.
"We performed careful analysis of 144 Taurid fireballs observed by new digital autonomous fireball observatories of the European Fireball Network displaced over Czech Republic at 13 stations, Austria and Slovakia in 2015, when the activity was enhanced," researchers said.
The brightest fireball studied "was caused by a body in excess of 1,000 kg (2,204 lb), which corresponds to diameter more than one meter. Based on orbital similarity, we argue that asteroids of several hundred meters in diameter are members of the Taurid new branch as well."
The good news is that the larger asteroids seem to be porous and fragile, meaning they're more likely to split apart and subsequently disintegrate when they enter Earth's atmosphere. However, there's no guarantee that will happen.
Many of the Taurids come from Encke, a comet that orbits the sun and has been slowly crumbling over the last 30,000 years. Some astronomers have suggested that the Tunguska event, when a 500-foot asteroid exploded a few miles off the ground and flattened 770 square miles of Siberian wilderness in 1908, was caused by a fragment of Encke. The explosion was comparable to that of a 20-megaton nuclear bomb and would have been cataclysmic had it hit a densely populated area.
7 Jun 2017
Researchers just confirmed a theory originally proposed by Albert Einstein nearly a century ago, and it’s something that even the famed physicist thought was impossible. A team of scientists led by Kailash Sahu has observed a gravitational phenomenon in which light from stars is bent as it makes its way past neighbouring stars, and will publish their report in the journal Science on June 9th.
Einstein’s idea — that the gravitational pull of stars can actually manipulate light passing by from extreme distances — is commonly called “gravitational micro lensing.” The famous scientist never actually observed the effect, and had no proof that it indeed existed, but his knowledge of the effects of gravity told him it was not only possible, but likely. In 1936, he wrote in Science that, because of the distance between stars, “there is no hope of observing this phenomenon directly.”
Now, modern technology makes such an observation possible, and researchers have just confirmed that Einstein was indeed correct. That isn’t to say there was any doubt — examples of gravitation micro lensing have been detected in space before, but never in this context, as Einstein predicted, and never studied and measured in this way.
“When a star in the foreground passes exactly between us and a background star, gravitational micro lensing results in a perfectly circular ring of light – a so-called ‘Einstein ring.'” said Terry Oswalt, astronomer with Embry-Riddle Aeronautical University and chair of the Department of Physical Sciences. “The ring and its brightening were too small to be measured, but its asymmetry caused the distant star to appear off-centre from its true position,” Oswalt says. “This part of Einstein’s prediction is called ‘astrometric lensing’ and Sahu’s team was the first to observe it in a star other than the Sun.”
So what would Einstein think of this? “Einstein would be proud,” Oswalt said. “One of his key predictions has passed a very rigorous observational test.”
6 Jun 2017
In a 2013 observational study, University of Wisconsin-Madison astronomer Amy Barger and her then-student Ryan Keenan showed that our galaxy, in the context of the large-scale structure of the universe, resides in an enormous void -- a region of space containing far fewer galaxies, stars and planets than expected.
Now, a new study by a UW-Madison undergraduate, also a student of Barger's, not only firms up the idea that we exist in one of the holes of the Swiss cheese structure of the cosmos, but helps ease the apparent disagreement or tension between different measurements of the Hubble Constant, the unit cosmologists use to describe the rate at which the universe is expanding today.
Results from the new study were presented here today (June 6, 2017) at a meeting of the American Astronomical Society.
The tension arises from the realization that different techniques astrophysicists employ to measure how fast the universe is expanding give different results. "No matter what technique you use, you should get the same value for the expansion rate of the universe today," explains Ben Hoscheit, the Wisconsin student presenting his analysis of the apparently much larger than average void that our galaxy resides in. "Fortunately, living in a void helps resolve this tension."
The reason for that is that a void -- with far more matter outside the void exerting a slightly larger gravitational pull -- will affect the Hubble Constant value one measures from a technique that uses relatively nearby supernovae, while it will have no effect on the value derived from a technique that uses the cosmic microwave background (CMB), the leftover light from the Big Bang.
The new Wisconsin report is part of the much bigger effort to better understand the large-scale structure of the universe. The structure of the cosmos is Swiss cheese-like in the sense that it is composed of "normal matter" in the form of voids and filaments. The filaments are made up of super clusters and clusters of galaxies, which in turn are composed of stars, gas, dust and planets. Dark matter and dark energy, which cannot yet be directly observed, are believed to comprise approximately 95 percent of the contents of the universe.
The void that contains the Milky Way, known as the KBC void for Keenan, Barger and the University of Hawaii's Lennox Cowie, is at least seven times as large as the average, with a radius measuring roughly 1 billion light years. To date, it is the largest void known to science. Hoscheit's new analysis, according to Barger, shows that Keenan's first estimations of the KBC void, which is shaped like a sphere with a shell of increasing thickness made up of galaxies, stars and other matter, are not ruled out by other observational constraints.
"It is often really hard to find consistent solutions between many different observations," says Barger, an observational cosmologist who also holds an affiliate graduate appointment at the University of Hawaii's Department of Physics and Astronomy. "What Ben has shown is that the density profile that Keenan measured is consistent with cosmological observables. One always wants to find consistency, or else there is a problem somewhere that needs to be resolved."
The bright light from a supernova explosion, where the distance to the galaxy that hosts the supernova is well established, is the "candle" of choice for astronomers measuring the accelerated expansion of the universe. Because those objects are relatively close to the Milky Way and because no matter where they explode in the observable universe, they do so with the same amount of energy, it provides a way to measure the Hubble Constant.
Alternatively, the cosmic microwave background is a way to probe the very early universe. "Photons from the CMB encode a baby picture of the very early universe," explains Hoscheit. "They show us that at that stage, the universe was surprisingly homogeneous. It was a hot, dense soup of photons, electrons and protons, showing only minute temperature differences across the sky. But, in fact, those tiny temperature differences are exactly what allow us to infer the Hubble Constant through this cosmic technique."
A direct comparison can thus be made, Hoscheit says, between the 'cosmic' determination of the Hubble Constant and the 'local' determination derived from observations of light from relatively nearby supernovae.
The new analysis made by Hoscheit, says Barger, shows that there are no current observational obstacles to the conclusion that the Milky Way resides in a very large void. As a bonus, she adds, the presence of the void can also resolve some of the discrepancies between techniques used to clock how fast the universe is expanding.
5 Jun 2017
On 15 August 1977, the Ohio State University Radio Observatory detected a strong narrowband signal in the constellation Sagittarius (Sgr). The frequency of the signal, which matched closely with the hydrogen line (1420.40575177 MHz), peaked at approximately 23:16:01 EDT. The signal was so strong that astronomer Jerry Ehman, who first spotted it, circled it in red pen and wrote "Wow!" in the margin. The "Wow! signal," as it would come to be known, became the best evidence ever obtained for extra-terrestrial life.At least, until now. One astronomer believes he's figured out what really caused the Wow! signal and—spoiler alert—it's not aliens.
On the same date and time, comet 266P/Christensen was transiting in the vicinity where the “Wow!”
Signal was detected. The purpose of this investigation, therefore, was to collect and analyse radio emission spectra and determine if comet 266P/Christensen and/or any other previously unknown celestial body in the Solar System was the source of the 1977 “Wow!” Signal. This investigation, moreover, was designed to improve our understanding of the content and origin of the “Wow!’ Signal by determining if a neutral hydrogen cloud emitted from a short-period comet could be detected by a terrestrial radio telescope.
USE THIS LINK TO DOWN LOAD THE FULL SCIENCE PAPER
Astronomer Antonio Paris has been studying the Wow! signal for a long time. In 2016, he released a paper along with fellow astronomer Evan Davies suggesting that the signal could have been caused by a comet orbiting in the inner solar system. Specifically, the 2016 paper identified two comets, 266P/Christensen and P/2008 Y2 (Gibbs), that were both in the area where the Wow! signal was detected.
Both of these comets have large hydrogen clouds surrounding them that could produce the kind of signal detected in 1977. Paris spent about four months in late 2016 and early 2017 with a telescope pointed at comet 266P, and found strong signals of the same type as the Wow! signal.
Paris also examined several other similar comets and found the same type of hydrogen cloud and the same type of signal, which means that even if comet 266P wasn't the specific source of the Wow! signal, another comet is most likely the culprit.
This is bad news for anyone holding out hope that the Wow! signal would be aliens, but it's a solid conclusion to one of the biggest mysteries in astronomy. Now that we know comets can create these otherworldly signals, any future signals we get will have to be vetted much more carefully.
29 May 2017
Scientists have discovered that almost every galaxy has a supermassive black hole with a mass several million to several billion times that of the Sun at its centre. With their mighty gravitational attraction, the supermassive black holes engulf the surrounding gas and dust.
When a black hole swallows too much, the excess matter is converted into two jet-flows perpendicular to the accretion disk of the black hole, which is like a glutton with a bloated belly belching.
The jet-flows and accretion disk of the supermassive black hole generate X-ray radiation strong enough to travel billions of light years. These galaxies have very bright nuclei -- so bright the central region can be more luminous than the remaining galaxy. Scientists call them active galactic nuclei.
The Hard X-ray Modulation Telescope (HXMT), developed by Chinese scientists, will observe some active galactic nuclei.
"Since the active galactic nuclei are very far from the Earth, our telescope can only detect the brightest ones," says Zhang Shuangnan, lead scientist of HXMT and director of the Key Laboratory of Particle Astrophysics at the Chinese Academy of Sciences (CAS).
The big eaters are full of mysteries. Scientists have found the double jet phenomenon is very common in galaxies with active galactic nuclei, but they don't understand why supermassive black holes cannot engulf all the matter falling into them.
Supermassive black holes are very different from black holes of stellar mass, which are formed when very massive stars collapse at the end of their life cycles. Scientists are still not clear how supermassive black holes are formed and grow, which is a key to understanding the evolution of galaxies.
HXMT's observation is expected to help scientists see the core region close to the event horizon of supermassive black holes at the centre of active galaxies and gather information about the extremely strong gravitational fields, Zhang says.
28 May 2017
China will soon launch its first X-ray space telescope, the Hard X-ray Modulation Telescope (HXMT), with the aim of surveying the Milky Way to observe celestial sources of X-rays.
"Our space telescope has unique capabilities to observe high-energy celestial bodies such as black holes and neutron stars. We hope to use it to resolve mysteries such as the evolution of black holes and the strong magnetic fields of neutron stars," says Zhang Shuangnan, lead scientist of HXMT and director of the Key Laboratory of Particle Astrophysics at the Chinese Academy of Sciences (CAS).
"We are looking forward to discovering new activities of black holes and studying the state of neutron stars under extreme gravity and density conditions, and the physical laws under extreme magnetic fields. These studies are expected to bring new breakthroughs in physics," says Zhang.
Compared with X-ray astronomical satellites of other countries, HXMT has larger detection area, broader energy range and wider field of view. These give it advantages in observing black holes and neutron stars emitting bright X-rays, and it can more efficiently scan the galaxy, Zhang says.
The telescope will work on wide energy range from 1 to 250 keV, enabling it to complete many observation tasks previously requiring several satellites, according to Zhang.
Other satellites have already conducted sky surveys, and found many celestial sources of X-rays. However, the sources are often variable, and occasional intense flares can be missed in just one or two surveys, Zhang says.
New surveys can discover either new X-ray sources or new activities in known sources. So HXMT will repeatedly scan the Milky Way for active and variable celestial bodies emitting X-rays.
"There are so many black holes and neutron stars in the universe, but we don't have a thorough understanding of any of them. So we need new satellites to observe more," Zhang says.
The study of black holes and neutron stars is often conducted through observing X-ray binary systems. The X-ray emissions of these binary systems are the result of the compact object (such as black hole or neutron star) accreting matter from a companion regular star.
By analysing binary system X-ray radiation, astronomers can study compact objects such as black holes or neutrons stars.
How do the black holes or neutron stars accrete matter from companion stars? What causes X-ray flares? These are questions scientists want to answer, and China's new space telescope might help.
Lu Fangjun, chief designer of the payload of HXMT, says the space telescope will focus on the Galactic plane. If it finds any celestial body in a state of explosion, it will conduct high-precision pointed observation and joint multiband observation with other telescopes either in space or on the ground.
26 May 2017
Astronomers have found what looks to a fresh trove of supermassive black hole pairs, increasing the number of known pairs by about 50 percent, after new image analysis techniques were used to study two of our most detailed sky surveys.
Finding these black hole pairs is crucial to understanding more about how they form and how galaxies eventually collide, with the new findings giving astronomers five new pairs to analyse.
At the centre of the new research is the hunt for dual active galactic nuclei (AGN) - the technical term for what's formed when two supermassive black holes get caught in a death spiral after the collision of their respective galaxies.
These two black holes get closer and closer before eventually crashing into each other to form an even larger supermassive black hole, shooting out huge amounts of energy at the same time - or at least that's the current hypothesis.
Occasionally, the collision seems to send the resulting black hole speeding off through space, but that's another story.
The AGNs are formed from the massive amounts of gas and dust stirred up as a result of this black hole death spiral, causing the final, really supermassive black hole to be heavier.
Active galactic nuclei can form around any black hole, giving us a better chance of spotting them from Earth, but to understand how all this works, we need to find more of them.
"Our model of the universe tells us [AGNs] should be there, but we have failed miserably to find them," lead research Sara Ellison from the University of Victoria in Canada told New Scientist.
Ellison and her colleagues looked at the WISE All Sky Survey and the Sloan Digital Sky Survey for their work, hunting for signs of recent galaxy collisions as well as high readings from the infrared part of the spectrum, which indicates lots of dust.
Further confirmation was found from luminosity measurements taken by the Chandra X-ray Observatory. The new technique turned up five new examples of dual AGNs, to add to the nine that had already been confirmed by X-ray studies.
That's "a significant new haul", write the researchers, and there could be more on the way.
We should point out that the research has yet to go through the peer-review process, so further confirmation of the findings is needed before they're confirmed, but this could end up being a very useful way of detecting more of these AGNs.
Once astronomers know where they are, they can study how they evolve, and how the resulting supermassive black holes grow.
These AGNs could also teach us more about gravitational waves, another after-effect of a collision of two black holes: or at least they will when the shock reaches us, in tens of millions of years.
25 May 2017
Early science results from NASA's Juno mission to Jupiter portray the largest planet in our solar system as a complex, gigantic, turbulent world, with Earth-sized polar cyclones, plunging storm systems that travel deep into the heart of the gas giant, and a mammoth, lumpy magnetic field that may indicate it was generated closer to the planet's surface than previously thought.
"We are excited to share these early discoveries, which help us better understand what makes Jupiter so fascinating," said Diane Brown, Juno program executive at NASA Headquarters in Washington. "It was a long trip to get to Jupiter, but these first results already demonstrate it was well worth the journey."
Juno launched on Aug. 5, 2011, entering Jupiter's orbit on July 4, 2016. The findings from the first data-collection pass, which flew within about 2,600 miles (4,200 kilometers) of Jupiter's swirling cloud tops on Aug. 27, are being published this week in two papers in the journal Science, as well as 44 papers in Geophysical Research Letters.
"We knew, going in, that Jupiter would throw us some curves," said Scott Bolton, Juno principal investigator from the Southwest Research Institute in San Antonio. "But now that we are here we are finding that Jupiter can throw the heat, as well as knuckleballs and sliders. There is so much going on here that we didn't expect that we have had to take a step back and begin to rethink of this as a whole new Jupiter."
Among the findings that challenge assumptions are those provided by Juno's imager, JunoCam. The images show both of Jupiter's poles are covered in Earth-sized swirling storms that are densely clustered and rubbing together.
"We're puzzled as to how they could be formed, how stable the configuration is, and why Jupiter's north pole doesn't look like the south pole," said Bolton. "We're questioning whether this is a dynamic system, and are we seeing just one stage, and over the next year, we're going to watch it disappear, or is this a stable configuration and these storms are circulating around one another?"
Another surprise comes from Juno's Microwave Radiometer (MWR), which samples the thermal microwave radiation from Jupiter's atmosphere, from the top of the ammonia clouds to deep within its atmosphere. The MWR data indicates that Jupiter's iconic belts and zones are mysterious, with the belt near the equator penetrating all the way down, while the belts and zones at other latitudes seem to evolve to other structures. The data suggest the ammonia is quite variable and continues to increase as far down as we can see with MWR, which is a few hundred miles or kilometres.
Prior to the Juno mission, it was known that Jupiter had the most intense magnetic field in the solar system. Measurements of the massive planet's magnetosphere, from Juno's magnetometer investigation (MAG), indicate that Jupiter's magnetic field is even stronger than models expected, and more irregular in shape. MAG data indicates the magnetic field greatly exceeded expectations at 7.766 Gauss, about 10 times stronger than the strongest magnetic field found on Earth.
"Juno is giving us a view of the magnetic field close to Jupiter that we've never had before," said Jack Connerney, Juno deputy principal investigator and the lead for the mission's magnetic field investigation at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Already we see that the magnetic field looks lumpy: it is stronger in some places and weaker in others. This uneven distribution suggests that the field might be generated by dynamo action closer to the surface, above the layer of metallic hydrogen. Every flyby we execute gets us closer to determining where and how Jupiter's dynamo works."
Juno also is designed to study the polar magnetosphere and the origin of Jupiter's powerful auroras -- its northern and southern lights. These auroral emissions are caused by particles that pick up energy, slamming into atmospheric molecules. Juno's initial observations indicate that the process seems to work differently at Jupiter than at Earth.
Juno is in a polar orbit around Jupiter, and the majority of each orbit is spent well away from the gas giant. But, once every 53 days, its trajectory approaches Jupiter from above its north pole, where it begins a two-hour transit (from pole to pole) flying north to south with its eight science instruments collecting data and its JunoCam public outreach camera snapping pictures. The download of six megabytes of data collected during the transit can take 1.5 days.
"Every 53 days, we go screaming by Jupiter, get doused by a fire hose of Jovian science, and there is always something new," said Bolton. "On our next flyby on July 11, we will fly directly over one of the most iconic features in the entire solar system -- one that every school kid knows -- Jupiter's Great Red Spot. If anybody is going to get to the bottom of what is going on below those mammoth swirling crimson cloud tops, it's Juno and her cloud-piercing science instruments."
NASA's Jet Propulsion Laboratory in Pasadena, California, manages the Juno mission for NASA. The principal investigator is Scott Bolton of the Southwest Research Institute in San Antonio. The Juno mission is part of the New Frontiers Program managed by NASA's Marshall Space Flight Center in Huntsville, Alabama, for the agency's Science Mission Directorate. Lockheed Martin Space Systems, in Denver, built the spacecraft.
21 May 2017
At one stage in its history rain storms on Mars were so heavy – and the raindrops so large – that they changed the planet’s surface, carving valleys and altering the shape of meteorite impact craters, new research shows.
Soon after its formation around 4.5 billion years ago, atmospheric pressure on the red planet was around four bars. To compare, Earth’s is one.
At that pressure, Craddock and Lorenz say, rain would have looked more like mist. Raindrops could not have grown to more than three millimetres in diameter, and would not have penetrated the ground when they hit it.
Over deep time, however, the atmospheric pressure decreased to around 1.5 bars. This, combined with lower gravity than that of Earth, meant that raindrops as large as 7.3 millimetres across could form – substantially bigger than the 6.5 millimetre whoppers sometimes recorded on our own planet.
The geologists calculate that the intensity of big falls would have been only about 70% of those found on Earth, but would still have been easily strong enough to put a dent or two in the ground.
Indeed, they suggest that the falls would have overwhelmed the soil’s ability to absorb moisture, thus creating run-off currents that eventually formed valley networks and reshaped impact craters.
“We have shown that Mars would have seen some pretty big raindrops that would have been able to make more drastic changes to the surface,” comments Lorenz, from Johns Hopkins University in the US.
Craddock, who works at the Smithsonian Institute, adds that their paper represents the first time scientists have used physics to gain insight into the Martian climate.
“There will always be some unknowns, of course, such as how high a storm cloud may have risen into the Martian atmosphere, but we made efforts to apply the range of published variables for rainfall on Earth,” he adds.
“It’s unlikely that rainfall on early Mars would have been dramatically different than what's described in our paper.”
9 May 2017
Late last month, 35 scientists met for 7 hours in Houston to discuss the basic blueprint and science goals of a potential Pluto orbiter mission. Such an effort would build upon the knowledge gained during the epic Pluto flyby performed in July 2015 by NASA's New Horizons probe.
Participants came away from the April 24 workshop fired up and committed to doing their best to make such a project happen, said New Horizons principal investigator Alan Stern, who was there. [Destination Pluto: NASA's New Horizons Mission in Pictures]
The meeting was reminiscent, Stern said, of New Horizons' earliest days: the late 1980s, when he and a few other people first raised the possibility of launching a flyby mission to Pluto.
"It felt a lot like that, but [with] a new generation of people," Stern, who's based at the Southwest Research Institute in Boulder, Colorado, told Space.com.
New Horizons' flyby revealed Pluto to be a stunningly diverse world with vast plains of nitrogen ice, 2-mile-high (3.2 kilometers) mountains of water ice and a wealth of other surface features. But the probe got just a fleeting look at the dwarf planet system while zooming by; an orbiter would linger and lift Pluto's veil even more, Stern said.
"You could map every square inch of the planet and its moons," he said. "It would be a scientific spectacular."
As the possible mission is currently envisioned, the orbiter would cruise around the Pluto system, using gravity assists from the dwarf planet's largest moon, Charon, to slingshot it here and there, Stern said. The strategy would be similar to that employed by NASA's Cassini spacecraft, which has shaped its path through the Saturn system over the years via flybys of the ringed planet's largest moon, Titan.
The current concept is therefore different from one Stern proposed shortly after New Horizons' flyby, which would have put a lander down on Charon.
With a Charon lander, "you're stuck looking at one side of Pluto," Stern said. (Charon and Pluto are tidally locked, meaning each world always shows the same face to the other.)
"And you can't get in superclose. You can't get down in the atmosphere," he added. "This, I think, is a better mission concept."
Though the mission would be Cassini-like, the Pluto orbiter itself would resemble NASA's Dawn probe, which is currently circling the dwarf planet Ceres, Stern said. Like Dawn, the Pluto probe would likely use electric propulsion and have a half-dozen science instruments, he said.
However, because the Pluto orbiter would be operating so far from the sun, it would rely on nuclear power to generate its electricity, rather than sunlight, as Dawn does, Stern added. And the price tag would be higher than Dawn's $467 million; the Pluto effort would probably qualify as a New Frontiers mission or a small flagship. (New Frontiers missions cost about $1 billion, whereas flagships run about $2 billion.)
Stern said a Pluto orbiter could get off the ground in the late 2020s or so. A 2030 launch would have ceremonial significance, coming on the 100th anniversary of Pluto's discovery, he added. The probe would spend seven or eight years journeying to the dwarf planet, then perhaps four or five years studying Pluto and its moons.
When the probe's work there was done, Stern said, the spacecraft could conceivably use one last Charon flyby to escape the Pluto system and head toward another object in the Kuiper Belt, the ring of frigid bodies beyond Neptune's orbit. (New Horizons is doing something similar; it's now headed for a Jan. 1, 2019, flyby of a small Kuiper Belt object called 2014 MU69.)
But a Pluto orbiter mission is a long way from becoming reality, Stern stressed. He said he and his fellow researchers aim to mature the concept in time for it to be considered during the next Planetary Science Decadal Survey, a U.S. National Research Council effort that sets exploration priorities for NASA every 10 years.
The next decadal survey will start in 2020, finish in 2022 and be published in 2023, Stern said.
"The curtain is opening," he said of the Pluto orbiter idea. "This thing is going to be a topic of discussion now for the next few years."
24 Apr 2017
Hidden Horizons, which specialises in science and natural history-based tours including coastal fossil hunting, began running stargazing safaris in 2016 as part of the inaugural Dark Skies Festival run jointly by the North York Moors and Yorkshire Dales National Parks.
The success of the 2016 and this February’s Festivals led to a spike in visitor interest for eyeing the dark skies and a surge in bookings for Hidden Horizons’ celestial exploring events.
Now, aided by a 50% grant from the North York Moors National Park Authority and additional support from the Forestry Commission, Hidden Horizons has purchased an inflatable planetarium, solar telescope and one of the county’s largest publicly-accessible portable telescopes to meet the growing interest.
The portability of the equipment means the company can now bring the wonders of the universe to schools, pubs, hotels and other public and private venues right across the region.
The beauty of the planetarium, which spans four-metres in diameter and can accommodate up to 30 children or 20 adults, means that Hidden Horizons can run sessions even if the weather prevents trips outdoors.
During the day the powerful solar telescope will enable visitors to safely observe sunspots and dramatic flares while the night sky telescope will lead budding astronomers on a journey deep into the universe, with its ability to reveal up to 40,000 objects at any one time.
Andy Exton, director and astronomer for Hidden Horizons comments:
“We’re very fortunate to have a great, expansive dark skies area on our doorstep and people are catching on to this.
Increasing numbers of stargazing bookings are coming from visitors outside the region, from as far afield as Manchester, London and even Singapore, and so this investment will really boost our offer, particularly as it increases our flexibility to stage pop-up astronomy evenings at a huge variety of venues.”
You can contact them here
Catriona McLees, Head of Promotion and Tourism for the North York Moors National Park Authority adds:
“We were delighted to extend grant funding for this initiative as it is a great legacy of the Dark Skies Festival and taps into the nation’s growing enthusiasm for stargazing. It will also help support other tourism businesses by providing a further draw for people to visit and stay in the National Park particularly during those months when footfall tends to drop off.”
23 Apr 2017
Aurora hunters were treated to an unusually intense and widespread display of the Southern Lights over the weekend, and it's not over yet, says Otago University astronomer Ian Griffin.
The Aurora Australis, or the Southern Lights, were spotted all over the country - and as far north as Auckland.
"This was quite an interesting display, I saw mostly greens, but other people who have got better eyes than me were seeing reds, but the photographs showed all the colours much better and there were some lovely purples in there as well. So it was a pretty stunning display, all told."
This week's display was caused by a large coronal hole on the sun, said Dr Griffin.
"It's basically a gap in the sun's magnetic field that starts spewing material towards the Earth - and it races towards the Earth at between 600 and 800 kilometres per second - and it's that material that interacts with the Earth's magnetic field and causes the atmosphere to glow.
"And that glow is the aurora, and the colour of the glow is different gases in the atmosphere, so the green glow is mainly oxygen and if you can see the red colour, that's nitrogen."
He said Sunday was unfortunately cloudy in Otago, but that he had seen some "brilliant' pictures of lights in Christchurch and Wellington, and even further north.
"One of the most amazing things was that somebody photographed it in Auckland, which is pretty incredible really, because to see the aurora that far north is very unusual. You may only see it in Auckland once every couple of years."
Dr Griffin said the current round of lights could continue for a few more days.
"It'll probably tail off, but if it's clear tonight, I would nip out and have a look."
Brown University researchers have published the most detailed geological history to date for a region of Mars known as Northeast Syrtis Major, a spot high on NASA's list of potential landing sites for its next Mars rover to be launched in 2020.
The region is home to a striking mineral diversity, including deposits that indicate a variety of past environments that could have hosted life. Using the highest resolution images available from NASA's Mars Reconnaissance Orbiter, the study maps the extent of those key mineral deposits across the surface and places them within the region's larger geological context.
"When we look at this in high resolution, we can see complicated geomorphic patterns and a diversity of minerals at the surface that I think is unlike anything we've ever seen on Mars," said Mike Bramble, a Ph.D. student at Brown who led the study, which is published in the journal Icarus. "Within a few kilometres, there's a huge spectrum of things you can see and they change very quickly."
If NASA ultimately decides to land at Northeast Syrtis, the work would help in providing a roadmap for the rover's journey.
"This is a foundational paper for considering this part of the planet as a potential landing site for the Mars 2020 rover," said Jack Mustard, a professor in Brown's Department of Earth, Environmental and Planetary Sciences and a co-author on the paper. "This represents an exceptional amount of work on Mike's part, really going into the key morphologic and spectroscopic datasets we need in order to understand what this region can tell us about the history of Mars if we explore it with a rover."
Northeast Syrtis sits between two giant Martian landforms—an impact crater 2,000 kilometres in diameter called the Isidis Basin, and a large volcano called Syrtis Major. The impact basin formed about 3.96 billion years ago, while lava flow from the volcano came later, about 3.7 billion years ago. Northeast Syrtis preserves the geological activity that occurred in the 250 million years between those two events. Billions of years of erosion, mostly from winds howling across the region into the Isidis lowlands, have exposed that history on the surface.
Within Northeast Syrtis are the mineral signatures of four distinct types of watery and potentially habitable past environments. Those minerals had been detected by prior research, but the new map shows in detail how they are distributed within the region's larger geological context. That helps constrain the mechanisms that may have formed them, and shows when they formed
relative to each other.
The lowest and the oldest layer exposed at Northeast Syrtis has the kind of clay minerals formed when rocks interact with water that has a fairly neutral pH. Next in the sequence are rocks containing kaolinite, a mineral formed by water percolating through soil. The next layer up contains spots where the mineral olivine has been altered to carbonate—an aqueous reaction that, on Earth, is known to provide chemical energy for bacterial colonies. The upper layers contain sulphate minerals, another sign of a watery, potentially life-sustaining environment.
Understanding the relative timing of these environments is critical, Mustard says. They occurred around the transition between the Noachian and Hesperian epochs—a time of profound environmental change on Mars.
"We know that these environments existed near this major pivot point in Mars history, and in mapping their context we know what came first, what came next and what came last," Mustard said. "So now if we're able to go there with a rover, we can sample rock on either side of that pivot point, which could help us understand the changes that occurred at that time, and test different hypotheses for the possibility of past life."
And finding signs of past life is the primary mission of the Mars2020 rover. NASA has held three workshops in which scientists debated the merits of various landing targets for the rover.
Mustard and Bramble have led the charge for Northeast Syrtis, which has come out near the top of the list at each workshop. Last February, NASA announced that the site is one of the final three under consideration.
Mustard and Bramble hope this latest work might inform NASA's decision, and ultimately help in planning the Mars2020 mission.
"As we turn our eyes to the next target for in situ exploration on the Martian surface," the researchers conclude, "no location offers better access of the gamut of geological processes active at Mars than Northeast Syrtis Major."
21 Apr 2017
The upgrade gives McDonald’s 10-meter telescope the ability to create a 3-D map of the universe to study dark energy, a little understood concept that could explain the accelerating expansion of the universe.
Photo Credit: Courtesy of Ethan Tweedie Photography | Daily Texan Staff
The telescope, the world’s third largest in size, can now see light that is close to 12 billion years old and can view 120 times more of the night sky than it previously could. Not even the largest telescope in the world at the Kek Observatory in Hawaii has as large of a field of view.
“It is sort of one of a kind right now,” McDonald Observatory director Taft Armandroff said. “It’s going to allow us to study a lot of areas of astronomy that are on the cutting edge.”
The Observatory received funding from the State of Texas, other universities and private donors to add four new instruments to the telescope along with expanding its view and depth. Two of these instruments, high and low resolution spectrographs, will be used to study the light from both galaxies and individual stars, Armandroff said.
Another new instrument allows the telescope to see high red-shift galaxies, or galaxies that are 10 to 12 billion light years away and were formed shortly after the Big Bang, Armandroff said.
Finally, Armandroff said the telescope now has a habitable zone planet finder which detects wobbles in the movement of a star to see if it has any orbiting planets.
Together, these devices will help astronomers at the University and elsewhere create a 3-D map they can use to measure how fast the universe’s expansion is accelerating and thereby give them an idea as to what force might be causing it, astrophysics professor Karl Gebhardt said.
“It’s crazy exciting. No one has looked at the universe in this way in the past,” Gebhardt said. “We may redefine what gravity actually is, (or dark energy) could be something like a new type of particle.”
Already, students at the University are analysing the data the telescope collects each night. After nightfall in West Texas, the telescope collects information that is sent to a server that both undergraduate and graduate students have access to.
After a class with Gebhardt last semester, aerospace engineering senior Jamie McCullough began working with the McDonald Observatory data. Most of the time, McCullough analyses the data sent over to adjust the information based on how much light was hitting the telescope. McCullough has also been working on writing a code that will perform these calibrations automatically.
“The upgrade is fantastic, and there’s so much data coming off of it, and there’s so much potential for so much advancement,” McCullough said. “It’ll really just be exciting to see what comes of it.”
19 Apr 2017
Radar images of asteroid 2014 JO25 were obtained in the early morning hours on Tuesday, with NASA's 70-meter (230-foot) antenna at the Goldstone Deep Space Communications Complex in California. The images reveal a peanut-shaped asteroid that rotates about once every five hours. The images have resolutions as fine as 25 feet (7.5 meters) per pixel.
Asteroid 2014 JO25 was discovered in May 2014 by astronomers at the Catalina Sky Survey near Tucson, Arizona -- a project of NASA's Near-Earth Objects Observations Program in collaboration with the University of Arizona. The asteroid will fly safely past Earth on Wednesday at a distance of about 1.1 million miles (1.8 million kilometres), or about 4.6 times the distance from Earth to the moon. The encounter is the closest the object will have come to Earth in 400 years and will be its closest approach for at least the next 500 years.
"The asteroid has a contact binary structure - two lobes connected by a neck-like region," said Shantanu Naidu, a scientist from NASA's Jet Propulsion Laboratory in Pasadena, California, who led the Goldstone observations. "The images show flat facets, concavities and angular topography."
The largest of the asteroid's two lobes is estimated to be 2,000 feet (620 meters) across.
Radar observations of the asteroid also have been conducted at the National Science Foundation's Arecibo Observatory in Puerto Rico. Additional radar observations are being conducted at both Goldstone and Arecibo on April 19 20, and 21, and could provide images with even higher resolution.
Radar has been used to observe hundreds of asteroids. When these small, natural remnants of the formation of the solar system pass relatively close to Earth, deep space radar is a powerful technique for studying their sizes, shapes, rotation, surface features, and roughness, and for more precise determination of their orbital path.
NASA's Jet Propulsion Laboratory, Pasadena, California, manages and operates NASA's Deep Space Network, including the Goldstone Solar System Radar, and hosts the Center for Near-Earth Object Studies for NASA's Near-Earth Object Observations Program within the agency's Science Mission Directorate.
18 Apr 2017
For hundreds of years there have been reports of people hearing the sound of meteors—shooting stars—as they streak across the sky. As early as 1714, astronomy Edmond Halley (yes, that Halley, of comet fame) dismissed these accounts of hissing, sizzling, and popping as figments of the imagination. After all, sound travels much more slowly than light—see: every thunderstorm ever—so any sound from the meteor breaking up in the atmosphere would arrive long after the streak of ionized gas has faded from the sky. But hearing and seeing a meteor at the same time is not a scientific impossibility. A new hypothesis published in Geophysical Research Letters might explain just how it happens, and why the described noises sound a lot like radio static.
When a meteor hits the atmosphere, at between 25,000 and 160,000 miles per hour, it releases electromagnetic radiation, including both light and what are known as very low frequency radio waves. Twenty-five years ago, scientists demonstrated that these waves, which travel just as fast as light, can cause objects, especially metal ones, to vibrate in a way that produces sound.
“The conversion from electromagnetic waves to sound waves … is exactly how your radio works,” Colin Price of Tel Aviv University, co-author of the new study, told Science. The study proposes that these waves come from an electrical current generated as the meteor interacts with the atmosphere. Though it involves coma ions, an am bipolar electric field, and Hall current, it’s the simplest explanation for the phenomenon yet.
The Square Kilometre Array (SKA) SA project office has acquired half of the land it needs to create a radio-quiet zone around the large radio telescope and is on track to complete the process by the end of 2018, says spokesman Lorenzo Raynard.
It is an important milestone in a sensitive process as, if the farmers in the area refuse to sell their land, the government can expropriate it. The SKA is an international science project located in SA and Australia and will be the world’s most powerful radio telescope once completed. The South African core is 90km from Carnarvon in the Northern Cape.
About 131,500ha of land surrounding the telescope’s 176-dish core needs to be free from radio-frequency interference. The project acquired 13,500ha of this land in 2008. In 2016 it embarked on a process to acquire another 118,000ha comprising 36 parcels of land close to the core as well as access rights to servitudes that will hold another 21 dishes.
The SKA SA project office has acquired 14 parcels of land, comprising 61,000ha and needs to buy another 18 parcels of land totalling 57,000ha. Four parcels of land originally earmarked for purchase no longer needed to be bought, but would provide access rights to servitudes, said Raynard. The land-acquisition project is one of three SKA processes under way in SA. The Department of Science and Technology has been driving the implementation of legislation to protect the site from radio interference.
17 Apr 2017
Despite having been told he would not make it past his 25th birthday, now 75-year-old renowned cosmologist and science author Stephen Hawking is being sent to space on billionaire Richard Branson’s Virgin Galactic ship. While confined to a wheelchair and communicating via a speech generator attached to a single cheek muscle, Stephen Hawking continues to contribute to the advancement of science in incredible ways. Over the course of his career, Hawking has also been a fierce advocate of disability rights and has shattered the glass ceiling of what people with disabilities are perceived to be capable of time and time again.
While the physical and intellectual capabilities of human beings differ greatly, they do not necessarily define us nor do they render us incapable of accomplishing significant feats. Stephen Hawking has visited one of Earth’s last thresholds, Antarctica, and has experienced weightlessness on a sub-orbital space flight. He is the Director of Research at the Centre for Theoretical Cosmology at the University of Cambridge and has written several novels, of which A Brief History of Time was a record-breaking best-seller. The physicist famously theorized that black holes emit radiation and is a recipient of the Presidential Medal of Freedom, the greatest award for civilians available in the United States. These are just a few of his accomplishments.
Hawking’s incredible career signifies the extent to which the empowerment of people with disabilities through increased accessibility and technological advancement can provide greater opportunities for everyone to pursue their dreams regardless of their circumstances. At age 21, Hawking was diagnosed with a rare early-onset form of amyotrophic lateral sclerosis (ALS) that has slowly paralyzed him. While this disease is generally fatal within five years, Hawking has lived more than five decades since his initial diagnosis. While not everyone diagnosed with ALS may have access to the same treatment and care as this academic celebrity, the longevity and success of Hawking’s career demonstrates that investing in people with disabilities is a worthy pursuit.
While Stephen Hawking’s physical capabilities have continued to decline over the decades, his mind and intellect have remained intact. By providing Hawking with a vehicle to communicate his brilliance, the pursuit of science has benefited as a whole. People with disabilities are often erased in both science and science fiction. Becoming a spacefaring species was one of the greatest defining moments for human beings. Now, we look to colonizing other terrestrial bodies in the event that one day our own planet can no longer harbour life.
In a visit to London’ Space Museum in 2015, Stephen Hawking stated that space travel “represents an important life insurance for our future survival, as it could prevent the disappearance of humanity by colonizing other planets.” One of the cosmologist’s biggest dreams has been to travel to space himself which will, in the near future, become a reality. As an icon for disability rights activism, Hawking’s journey will allow people with disabilities to see themselves represented in the voyage to the stars.
In science fiction, writers imagine future worlds in which anything is possible. In these imaginings of tomorrow, be they utopian, dystopian or complex, nuanced worlds with problems like our own, disability is often perceived as something to be cured, fixed or erased altogether. In pathologizing disability or removing it entirely from futurist contexts, people with disabilities often do not find themselves represented or as fitting into the grand scheme. As a result, Stephen Hawking’s projected spaceflight matters immensely as it exemplifies that he, like anyone else, is an individual with his own physical and intellectual capacities, of which having a disability is not his sole-defining characteristic.
It is evident that Hawking’s career has been greatly empowered due to his intelligence and access to economic capital which others with his disease may not be as fortunate to have. However, he is a shining example of the potential that can be realized when society works to develop technology and increase accessibility for everyone. Today, accessibility can take on the form of ensuring all stations on public transit lines have elevators or that all new buildings use levers instead of door knobs. The shift towards accessibility in urban planning and the design of all things means that people with disabilities have a bright future ahead.
The rise of space tourism by private companies like Virgin Galactic and SpaceX are disrupting the entire space exploration industry. The CEO of SpaceX, founder of PayPal and Tesla Motors’ Elon Musk has launched private vehicles into space and enabled them to return to Earth with reusable rockets. In doing so, Musk has greatly reduced the cost of spaceflight and in turn made it more accessible. As these companies continue to develop space technology, the goal of taking humans to other planets becomes more realistic. Not only this but also sending human beings to space from all walks of life including those, like Stephen Hawking, with disabilities.
Stephen Hawking being sent so space matters for every dreamer who has imagined themselves leaving Earth to gaze down in wonder upon the curvature of the pale blue dot. It has traditionally only been astronauts with unparalleled physical and intellectual ability who have had the enormous privilege of leaving our planet’s atmosphere. Now, the extremely wealthy can purchase a ticket to the stars via private space travel companies. However, as evidenced by this change and while it may take centuries, it is only a matter of time before space travel becomes available to everyone. | 0.963596 | 3.517888 |
“I call it ‘the awakening.’ The whole world is waking up to the fact that we’re getting close to finding other Earths and signs of life…It will change the way we see our place in the universe,” says Sara Seager, an astrophysicist and 2013 winner of a MacArthur “genius” award, who is working to find life on other planets outside the solar system.
Every star in the sky is a sun. “And if our sun has planets, we expect that other stars will have planets too, and they do,” says the professor of planetary science and physics who holds the Class of 1941 Professorship. In fact, such exoplanets are common. More than 2,000 have been discovered since 1995, and there are probably many more.
“Statistically we think each of the approximately 100 billion stars in the Milky Way has at least one planet,” says Seager. Of those, as many as one in five stars like the sun has a rocky, Earth-sized planet that could have the right surface temperatures for life.
Those are the exoplanets that Seager, who was recruited by MIT to build its exoplanet program, is searching for. And it’s a challenge. “Other Earths are so small and dim compared to the star they’re right beside.” Our own sun, for example, is ten billion times brighter than Earth.
Although a few Earth-sized candidates have already been found, current telescopes are not powerful enough to tell us if they harbor life. Many projects are in the works, however, to change that; each will get us closer to that goal, Seager says.
She is working on three of these projects. One, dubbed ExoplanetSat, involves a space-based fleet of some 50 to 100 rectangular telescopes roughly the size of a milk carton. Each ExoplanetSat—the first could launch in a year—will be pointed at an individual star with the goal of detecting any planet that passes in front of the star during its orbit. The changes in brightness associated with such a transit can be analyzed to determine, among other things, the planet’s density. ExoplanetSat was first developed by Seager at MIT and is now a collaboration with Draper Lab and NASA/JPL.
The light from a transiting planet can also give insights into its atmosphere—something Seager predicted that led to the first-ever discovery of an exoplanet atmosphere. Another part of her work is searching for the atmospheric gases that could indicate life. Seager notes that although her research is focused on the detection of an Earth twin, it has other applications. “Some of the technology developed for ExoplanetSat is being adapted for long-distance laser communication and also Earth-imaging applications. Basic research inspires fundamental discoveries on which applications flourish.”
Seager is excited about the future. “We stand on a great threshold in the human history of space exploration,” she told Congress last December. “… If life is prevalent in our neighborhood of the galaxy, it is within our resources and technological reach to be the first generation in human history to finally cross this threshold, and to learn if there is life of any kind beyond Earth.” | 0.900462 | 3.669901 |
Neptune’s largest moon, Triton. Image credit: NASA. Click to enlarge
Neptune’s moon Triton is unique in the Solar System because it’s the only large moon that orbits in the opposite direction to its planet’s rotation. Researchers have developed a computer model that explains how Neptune could have captured Triton from another planet during a close approach. Under this scenario, Triton was originally part of a binary system with another planet. They got too close to Neptune and Triton was torn away.
Neptune’s large moon Triton may have abandoned an earlier partner to arrive in its unusual orbit around Neptune. Triton is unique among all the large moons in the solar system because it orbits Neptune in a direction opposite to the planet’s rotation (a “retrograde” orbit). It is unlikely to have formed in this configuration and was probably captured from elsewhere.
In the May 11 issue of the journal Nature, planetary scientists Craig Agnor of the University of California, Santa Cruz, and Douglas Hamilton of the University of Maryland describe a new model for the capture of planetary satellites involving a three-body gravitational encounter between a binary and a planet. According to this scenario, Triton was originally a member of a binary pair of objects orbiting the Sun. Gravitational interactions during a close approach to Neptune then pulled Triton away from its binary companion to become a satellite of Neptune.
“We’ve found a likely solution to the long-standing problem of how Triton arrived in its peculiar orbit. In addition, this mechanism introduces a new pathway for the capture of satellites by planets that may be relevant to other objects in the solar system,” said Agnor, a researcher in UCSC’s Center for the Origin, Dynamics, and Evolution of Planets.
With properties similar to the planet Pluto and about 40 percent more massive, Triton has an inclined, circular orbit that lies between a group of small inner moons with prograde orbits and an outer group of small satellites with both prograde and retrograde orbits. There are other retrograde moons in the solar system, including the small outer moons of Jupiter and Saturn, but all are tiny compared to Triton (less than a few thousandths of its mass) and have much larger and more eccentric orbits about their parent planets.
Triton may have come from a binary very similar to Pluto and its moon Charon, Agnor said. Charon is relatively massive, about one-eighth the mass of Pluto, he explained.
“It’s not so much that Charon orbits Pluto, but rather both move around their mutual center of mass, which lies between the two objects,” Agnor said.
In a close encounter with a giant planet like Neptune, such a system can be pulled apart by the planet’s gravitational forces. The orbital motion of the binary usually causes one member to move more slowly than the other. Disruption of the binary leaves each object with residual motions that can result in a permanent change of orbital companions. This mechanism, known as an exchange reaction, could have delivered Triton to any of a variety of different orbits around Neptune, Agnor said.
An earlier scenario proposed for Triton is that it may have collided with another satellite near Neptune. But this mechanism requires the object involved in the collision to be large enough to slow Triton down, but small enough not to destroy it. The probability of such a collision is extremely small, Agnor said.
Another suggestion was that aerodynamic drag from a disk of gas around Neptune slowed Triton down enough for it to be captured. But this scenario puts constraints on the timing of the capture event, which would have to occur early in Neptune’s history when the planet was surrounded by a gas disk, but late enough that the gas would disperse before it slowed Triton’s orbit enough to send the moon crashing into the planet.
In the past decade, many binaries have been discovered in the Kuiper belt and elsewhere in the solar system. Recent surveys indicate that about 11 percent of Kuiper belt objects are binaries, as are about 16 percent of near-Earth asteroids.
“These discoveries pointed the way to our new explanation of Triton’s capture,” Hamilton said. “Binaries appear to be a ubiquitous feature of small-body populations.”
The binary Pluto and its moon Charon and the other binaries in the Kuiper belt are especially relevant for Triton, as their orbits abut Neptune’s, he said.
“Similar objects have probably been around for billions of years, and their prevalence indicates that the binary-planet encounter that we propose for Triton’s capture is not particularly restrictive,” Hamilton said.
The exchange reaction described by Agnor and Hamilton may have broad applications in understanding the evolution of the solar system, which contains many irregular satellites. The researchers plan to explore the implications of their findings for other satellite systems.
This research was supported by grants from NASA’s Planetary Geology and Geophysics, Outer Planet Research, and Origins of Solar Systems programs.
Original Source: UC Santa Cruz | 0.882232 | 3.79722 |
NASA Headed For Outer Limit of Solar System, Ultima Thule, On Jan. 1, 2019
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What a great way to bring in the new yearl! The on-going NASA New Horizons mission, which on New Years Day, 2019, has achieved the most distant spacecraft flyby in history!
On this New Year’s Day, NASA has a special reason to celebrate: Its spacecraft New Horizons has made a successful flyby of Ultima Thule, an object orbiting in space about four billion miles from Earth. Science correspondent Miles O’Brien joins Jeffrey Brown to explain the immense difficulty of this mission and its larger significance for the U.S. space program, in the video “Why the latest New Horizons flyby represents a space exploration milestone“, below:
- Ultima Thule, a traditional name of distant places beyond the known world
- Ultima Thule (minor planet), unofficial name for (486958) 2014 MU69, a Kuiper belt asteroid visited on New Year’s Day, 2019, by NASA’s New Horizons spacecraft
Below, is the excerpt from wikipedia, in italics, on the topic of Ultima Thule:
(486958) 2014 MU69, nicknamed Ultima Thule, is a trans-Neptunian object located in the Kuiper belt. It is a contact binary with an estimated diameter of 30 km (20 mi). With an orbital period of 295 years and a low inclination and eccentricity, it is classified as a classical Kuiper belt object and suspected to have not undergone significant perturbations and to be only moderately cratered. It seems to have a binary-like shape as seen during a stellar occultation, yet has a very flat light curve more consistent with a spherical body. 2014 MU69 was discovered on 26 June 2014 by astronomers using the Hubble Space Telescope as part of a search for a Kuiper belt object for the New Horizons mission to target in its first extended mission; it was chosen over two other candidates to become the primary target of the mission. Its nickname, a Latin metaphor for a place located beyond the borders of the known world, was chosen as part of a public competition in 2018. The New Horizons team plans to submit a proper name to the International Astronomical Union after the spacecraft’s flyby on 1 January 2019, when the nature of the object is better known. It is the farthest object in the Solar System visited by a spacecraft.
When 2014 MU69 was first observed, it was labelled 1110113Y, nicknamed “11”, for short. Its existence as a potential target of the New Horizons probe was announced by NASA in October 2014and it was unofficially designated as “Potential Target 1”, or PT1. Its official designation, 2014 MU69 (a provisional designation indicating that it was the 1745th object discovered during the second half of June 2014), was assigned by the Minor Planet Center (MPC) in March 2015 after sufficient orbital information was gathered. After further observations pinning down its orbit, it was given the permanent minor planet number 486958 on 12 March 2017 (as announced in M.P.C. 103886).
An official name for the object, consistent with the naming guidelines of the International Astronomical Union, will be selected by the New Horizons team after the spacecraft’s flyby in January 2019, when the properties of (486958) 2014 MU69 are known well enough to choose a suitable name. In the interim, NASA invited suggestions from the public on a nickname to be used. The campaign involved 115,000 participants from around the world, who suggested some 34,000 names. Of those, 37 reached the ballot for voting and were evaluated for popularity–this included eight names suggested by the New Horizons team and 29 suggested by the public. “Ultima Thule” (/ˈθjuːliː/ THEW-lee [US THOO-lee or TOO-lee]), which was selected on 13 March 2018, was nominated by about 40 members of the public and was one of the highest vote-getters among the nominees. It is named after the Latin phrase ultima Thule (literally farthermost Thule), an expression referencing the most distant place beyond the borders of the known world.
In 2014, 2014 MU69 was estimated to have a diameter of 30–45 km (20–30 mi) based on its brightness and distance.Observations in 2017 concluded that 2014 MU69 is no more than 30 km (20 mi) long and very elongated, possibly a close or contact binary. The distance between the center of 2014 MU69‘s observed lobes is about 16 kilometres (9.9 mi). Based on models from the New HorizonsPluto flyby, it has been predicted that 2014 MU69 is only moderately cratered, with no more than 25 to 50 craters larger than the effective resolution limit of 200 metres (660 ft). Unlike in the inner Solar System, where collisions typically occur at velocities above 10 km per second, it is expected that most craters on 2014 MU69 were formed at much lower speeds. Their morphology may differ from that seen on previously visited asteroids. If the cratering rate is low then most of the surface is expected to be pristine, possibly showing signs of the original accretion, 4.6 billion years ago. 2014 MU69 has a red spectrum, and is the smallest Kuiper belt object to have its colors measured.
2014 MU69‘s orbital period around the Sun is slightly more than 295 years and it has a low inclination and low eccentricity compared to other objects in the Kuiper belt.These orbital properties mean that it is a cold classical Kuiper belt object which is unlikely to have undergone significant perturbations. Observations in May and July 2015 as well as in July and October 2016 greatly reduced the uncertainties in the orbit. Results from Hubble Space Telescope observations show that the brightness of 2014 MU69 varies by less than 20 percent as it rotates. This placed significant constraints on the axis ratio of 2014 MU69 to <1.14, having assumed an equatorial view. Despite 2014 MU69‘s irregular shape, there is no detectable light curve amplitude, as its axis is oriented on its side, pointing towards the Sun. Distant satellites of 2014 MU69 have been excluded to a depth of >29th magnitude.
New Horizons is the first mission to the Kuiper Belt, a gigantic zone of icy bodies and mysterious small objects orbiting beyond Neptune. This region also is known as the “third” zone of our solar system, beyond the inner rocky planets and outer gas giants. Johns Hopkins University Applied Physics Laboratory (APL) in Maryland, designed, built and operates the New Horizons spacecraft, and manages the mission for NASA’s Science Mission Directorate in Washington. The Year of Pluto – NASA New Horizons is a one hour documentary which takes on the hard science and gives us answers to how the mission came about and why it matters. Interviews with Dr. James Green, John Spencer, Fran Bagenal, Mark Showalter and others share how New Horizons will answer many questions. New Horizons is part of the New Frontiers Program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. The video, “The Year of Pluto-New Horizons Documentary Brings Humanity Closer To The Edge of the Solar System“, below:
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For casual terrestrial observations and quick looks at the Moon the TS PhotoLine 60mm, f/6 is quite at home on a sturdy photo tripod such as the author’s Manfrotto 055 shown here. Image: Ade Ashford. I built my first telescope out of a 100mm diameter, two-element government surplus lens of 500mm focal length in the early 1970s. While I was immensely proud of my four-inch, f/5 refractor, its images of the Moon and bright planets were surrounded by a vivid purple halo. Thus I had my introduction to the bane of simple lens-based instruments: chromatic aberration. I quickly learned that a simple compound lens composed of a sandwich of two types of glass with opposing dispersive (prismatic colour-making) qualities only goes a limited way to cancelling out this annoying inherent defect of refractors.
In fact, the use of crown and flint types of glass to fashion a so-called ‘achromatic’ lens capable of bringing two wavelengths of the colour spectrum (usually red and blue) to focus dates back to the British inventor Chester Moore Hall, in around 1730. However, for an achromat of typically encountered sizes to have an acceptable level of colour correction, an optician needs to make the instrument’s focal length at least twelve times the diameter (or aperture) of the lens, which immediately explains the long tubes of classical refractors.
The 60mm, f/6 air-spaced doublet is fully multi-coated and composed of highly desirable low-dispersion FPL53 glass and a matching lanthanum element for excellent colour correction for both visual and photographic applications. The anti-reflection coatings are so good that it requires a bright source to render them visible to the camera. Image: Ade Ashford. In the intervening years, opticians have developed so-called ‘apochromatic’ (or ‘apo’) refractors, typically composed of a three-glass element sandwich capable of bringing three colours of the visible spectrum (typically red, green and blue) to a common focus. Such exquisitely crafted instruments from high-end manufacturers such as Takahashi and Astro-Physics use exotic glasses, ground and polished to complex geometries, to create compact refractors that provide essentially perfect imagery for visual and photographic use, but they usually command an eye-watering price.
However, comparatively recent optical research has led to the mass production of extra-low-dispersion (‘ED’) glass types capable of curbing the tendency of a lens to split white light into a spectrum to such an extent that short focal-ratio refractors with excellent colour correction can now be produced from a two-element lens, sometimes referred to as a doublet. Calcium fluoride (CaF2), which occurs naturally as the mineral fluorite, makes a superior ED lens element, but it is a somewhat fragile material to grind and polish, plus it’s thermally unstable (meaning that it’s shape changes slightly with temperature).
An ED glass manufactured by Ohara in Japan, known as S-FPL-53 (commonly written FPL53), has very similar optical characteristics to fluorite, but it is less expensive, far easier to polish and is more stable, both chemically and thermally. Ohara also produces S-FPL-51, which is an ED glass that is cheaper than FPL53 and even easier to work with. With the correct prescription of lens geometry and mating glass element, FPL51 is capable of producing an excellent ED refractor, but the choice of FPL53 glass wherever possible gives the optical designer far greater freedom to produce a doublet with a performance deserving of the name ‘apo’. Such is the on-paper prescription of the TS-Optics PhotoLine 60mm, f/6 FPL53 that I review here.
When a 17 × 21 × 31 centimetre shipping box arrived at my door from Telescope-Service (TS) in Germany, I initially thought that I’d been sent the wrong product: could a package this small really contain a 60mm, f/6 refractor? It turns out that it can, for once it’s divested of packaging, the instrument is just 23 centimetres long from the front lens cap to the rear of its 2-to-1.25-inch eyepiece adapter when both its dewshield and focuser drawtube are fully retracted.
Being so small, the TS PhotoLine 60mm, f/6 forgoes tube rings and a dovetail bar in favour of a reversible, hinged split-ring collar with an L-shaped foot possessing two ¼–20 and one central 3/8ths-inch photo-tripod connections. Straight out of the box, the instrument tips the scales at just 1.52 kilograms.
In ‘compact mode’ the TS-Optics PhotoLine 60mm f/6 Apo refractor seems almost pocket-sized. With both its dewshield and focuser drawtube retracted it’s just 23cm long and tips the scales at 1.52kg. Image: Ade Ashford. The objective, which has a full aperture of 60mm, is fully multi-coated with the unblemished deep green hue that one comes to expect of a quality lens these days. The rear collar of the sliding dewshield, fine focusing knob, two-inch eyepiece-locking collar at the end of the focuser and the drawtube lock knob are all anodised in a striking red that contrasts with the otherwise wholly black and white livery. (For the more conservative among you, TS-Optics provide a version of this instrument in a black and white finish with a gold-coloured fine focus knob.)
Inside the optical tube, which has an effective matte black coating, there is a single baffle about two centimetres behind the doublet. The remaining suppression of scattered internal light is provided by the 14.2 centimetre-long focuser drawtube that has an internal diameter of 50.8mm (two inches) and a finely milled finish with a matte black coating, a combination that is particularly effective. The 118mm-long helically-cut brass rack has no discernible backlash against the pinion, and one full rotation of the 1:9:3 ratio fine focusing wheel advances the drawtube 2.25mm over a total travel of 75mm.
The drawtube’s engraved millimetre scale is useful for reproducing approximate visual and photographic foci (more on imaging later). The focuser doesn’t rotate with respect to the tube, but should the focusing knobs not lie in a convenient position for you, then slackening a knurled knob on the hinged split-ring collar enables you to rotate the entire optical tube relative to the L-shaped foot. The drawtube is lockable once precise focus is found. Two-inch push-fit diagonals and accessories are secured by a non-marring brass compression ring via three clamping bolts at 120-degree intervals.
The instrument’s L-shaped mounting foot has two ¼–20 and one central 3/8ths-inch thread photo-tripod connections. Image: Ade Ashford. While the machining and finish of the tube, lens cell and focuser are all first rate and the instrument feels reassuringly robust in hand, I have a few niggles with the design. The end of the extended dewshield lies just 50mm in front of the objective, which is barely adequate. Given that there is still 50mm of tube behind the retracted dewshield, why not make it 50mm longer to ensure a full 100mm of dew protection and an effective light shield for daytime use?
I think that Telescope-Service also missed an opportunity to make the L-shaped mounting foot’s cross-section compatible with the Vixen-style dovetail block used on the vast majority of small telescope mounts; TS expects you to purchase a Vixen-compatible dovetail rail for an extra €24.89. Furthermore, while there are two domed-head Allen mounting bolts on either side of the focuser, a finderscope mounting shoe is a €24 add-on. I appreciate that margins are tight these days, but a Vixen dovetail mounting rail and a finderscope mounting shoe should be standard equipment for a telescope of this calibre.
Since the PhotoLine 60mm, f/6 has a drawtube focusing range of 75mm, then just about every two- and 1.25-inch (50.8 and 31.75mm) push-fit star diagonal and eyepiece combination should permit you to reach focus at infinity – every eyepiece at my disposal compatible with this instrument certainly did. Given the focal length of 360mm and the focal ratio, mature observers with fully dilated pupils of around 5mm would be advised not to use eyepieces with a focal length longer than 30mm if they wish to accommodate the full exit pupil. At the magnification of 12× delivered by such an eyepiece, even 1.25-inch oculars will deliver true fields of view well in excess of four degrees; two-inch eyepieces will give you fields in excess of six degrees for monocular-like views.
At the upper magnification range, one should be mindful that this is just a 60mm aperture telescope, so eyepieces with focal lengths shorter than about 3mm (or the Barlowed equivalent) are to be avoided. For my high-power tests I used a 3.2mm focal length TMB Optical Planetary II eyepiece delivering 113× magnification in conjunction with a TeleVue 1.25-inch mirror diagonal. Used in this configuration during the daytime, tiny yet intense specular reflections viewed in distant beads of dew revealed that the review instrument was perfectly collimated with a vanishingly small amount of under-correction.
Defocusing the instrument a few waves intra-focally revealed symmetrical diffraction rings with a faint purple tinge, while the diffraction rings viewed the same distance extra-focally displayed a central reddish hue and greenish-blue periphery. However, at focus, even on extremely bright examples of water droplet ‘artificial stars’ in sunlight, the colour correction of the review model TS PhotoLine 60mm, f/6 was undoubtedly impressive.
For those observers intending to also use the instrument as a daytime spotter-scope for nature study or sporting events, I could focus on subjects just 7.5 metres away while using the TeleVue 1.25-inch diagonal and a 10mm Plössl eyepiece at 36×. However, for regular terrestrial use, an Amici prism star diagonal for delivering a fully erect image, plus a quality zoom eyepiece, would be good investments.
The instrument has just one light baffle in the optical tube, but the interior of the drawtube has a finely milled finish with a matte black coating that is effective at suppressing scattered light. Note the non-marring brass compression ring and three clamping bolts at 120-degree intervals to securely hold push-fit optical accessories or the supplied eyepiece adaptor. Image: Ade Ashford. Turned to the night-time sky, the TS-Optics PhotoLine 60mm, f/6 FPL53 apo excels at lunar observations. On an evening of moderately good seeing at the end of civil twilight on Monday 2 December, the six-day-old waxing lunar crescent presented a wealth of detail in the 3.2mm TMB eyepiece at 113× magnification. My observing notes relate that in the Moon’s northern polar region, the horn-shaped crescent tapered to a jagged point with three nearby high lunar peaks beyond the terminator catching the rays of sunlight, looking like tiny islands in a jet-black sea separated from an isthmus of land.
Heading south along the sunrise line on the lunar surface, 95-kilometre-wide impact crater Posidonius, on the north-eastern edge of Mare Serenitatis, was replete in detail, in particular showing the almost semi-circular concentric rim of the inner lava-flooded crater, as well as the central craterlet Posidonius A and hints of the main crater’s extensive rille system. In Mare Serenitatis itself, wrinkle ridges parallel to its eastern shore were similarly well seen. Further south, 40-kilometre-wide Plinius prominently marked the boundary of Mare Tranquillitatis and I lingered a while on the southern edge of this lunar sea, near the famous landing site of Apollo 11.
The highlight of this particular lunar excursion was the prominent and similarly sized trio of craters Theophilus, Cyrillus and Catharina, to the west of Mare Nectaris in the Moon’s southern hemisphere. One-hundred-kilometre-wide Theophilus intrudes into Cyrillus, the former clearly displaying its massive, terraced rim and central triple peak. Something that I had probably noticed before at this waxing lunar phase but not really appreciated was the hourglass-like ‘waist’ separating craters Cyrillus and Catharina that was wreathed in shadow on the night of 2 December. At magnifications ranging from 33× to 113×, I placed the lunar crescent just outside the edge of the field of view and couldn’t detect any spurious glows from scattered light in any orientation.
Given its relatively short f/6 focal ratio, this instrument will show signs of field curvature with both cropped and full-frame DSLRs, or large-format CCD/CMOS devices. This is not a fault of the TS PhotoLine 60mm f/6 FPL-53 apo per se, since all fast refractors without some form of field-flattening accessory will display stars as short streaks in the corners of the frame, while those stars in the centre of view are perfectly round and sharp.
Fortunately, Telescope-Service supplies an optional flattener and field corrector known as the TSFlat60. Just 95mm long and adding 237 grams to the mass of the telescope, the TSFlat60 has a male M54×0.75 thread on the telescope side that screws securely into the focuser’s drawtube once the two-inch eyepiece locking collar is unthreaded. On the camera side of the TSFlat60 there’s a standard male M48×0.75 photo thread, so all you need is the T-mount bayonet adaptor appropriate for your DSLR camera body to automatically establish the optimal back focus of 55mm from the male M48 thread.
Field curvature is virtually eliminated across full-frame-sized DSLRs and CCD/CMOS devices with the optional 1.0× TSFlat60 field flattener, shown here. It incorporates a 360-degree rotation collar for composing your image that’s secured by the knurled lock knob. Image: Ade Ashford. The optics of the TSFlat60 are fully multi-coated like the telescope’s objective lens, while all inside surfaces of the field flattener are milled and coated matte black to prevent internal reflections. Given that there is no provision for rotating the telescope’s focuser for framing a shot, the TSFlat60 neatly incorporates a robust 360-degree rotation collar secured by a single knurled lock knob. Another feature of the field flattener is that it’s designed to preserve the f/6 focal ratio (and 360mm focal length) of the TS-Optics PhotoLine 60mm f/6 FPL-53 apo.
Furthermore, the TSFlat60 is also designed to deliver a fully corrected and illuminated field of view that is 41mm wide, hence cameras with full-frame sensors (43.25mm diagonal) are almost fully covered. In tests with my full-frame Canon 5D Classic, aggressive image processing revealed negligible vignetting, while plate solving revealed a true field of view of 5.54 × 3.69 degrees and a scale of 4.57 arcseconds per pixel. Given that the Canon 5D Mark 1 has 8.2 micron pixels, a combination of the TS PhotoLine 60mm, f/6 FPL-53 apo plus the TSFlat60 plus a DSLR delivers a true focal length of 370mm, hence the TSFlat60 is really a 1.03× field flattener. However, the field was indeed flat, albeit with negligible pincushion distortion.
The TSFlat60 is designed to provide a fully corrected and illuminated field of view 41mm wide, hence cameras with full-frame sensors (43.25mm diagonal) will experience tiny amounts of vignetting, while cropped-sensor (APS-C) DSLRs will be fully illuminated. In tests with my full-frame Canon 5D Classic, the focusing range was from infinity down to just three metres away. Image: Ade Ashford. Conclusions
The TS PhotoLine 60mm, f/6 FPL-53 apo arrives on the market amid some stiff competition from the suspiciously similar Astro-Tech AT60ED, the Altair 60EDF and the William Optics Zenithstar 61 apo (the Zenithstar’s 61mm, f/5.9 specification likely results from a lens cell with a slightly larger entrance pupil). It’s worth noting that the Altair 60EDF also includes as standard the 360-degree rotation collar supplied with the TSFlat60 but at a similar price, which is a big plus in the Altair’s favour. All of these telescopes are a perfect match for camera tracking mounts such as the Sky-Watcher Star Adventurer or iOptron SkyGuider Pro.
However, the fact that one has to buy a Vixen-style dovetail bar and a finderscope mounting shoe in order to fully exploit these instruments for serious astronomical imaging almost suggests that celestial imaging is of secondary importance to the manufacturers – or it could just be that margins are so tight that these items are considered extras. Whichever way you look at it, there’s no denying that the TS PhotoLine 60mm, f/6 apo is a cheaper alternative to certain prime camera lenses, and its marriage of well-figured FPL53 and lanthanum glass ensures it delivers a notable photo-visual performance, both on land and in the sky.
Optical design: FPL53 and lanthanum air-spaced doublet refractor
Coating: multi-coated on all air-to-glass surfaces
Focal length: 360mm
Focal ratio: f/6
Resolution: 1.9 arcseconds
Tube length: 230mm (retracted)/355mm (extended)
Focuser: two-inch rack-and-pinion focuser with 1:9:3 reduction gearing
Drawtube travel: 75mm
Flattener and field corrector:
Overall length: 95mm
Illuminated and corrected image field: 41mm
Image scale: 1.03×
Connection at telescope side: M54 × 0.75 thread (male)
Connection at camera side: M48 × 0.75 thread (male), length 4mm
Working distance: 55mm from the male M48 thread | 0.84781 | 3.553493 |
NASA’s discovered several million new black holes – along with a thousand or so galaxies obscured by dust – using the Wide-field Infrared Survey Explorer (WISE) telescope.
Images show millions of dusty black hole candidates across the universe, together with about 1,000 even dustier objects thought to be among the brightest galaxies ever found. Burning brightly with infrared light, they’re nicknamed hot DOGs.
“WISE has exposed a menagerie of hidden objects,” says WISE program scientist Hashima Hasan. “We’ve found an asteroid dancing ahead of Earth in its orbit, the coldest star-like orbs known and now, supermassive black holes and galaxies hiding behind cloaks of dust.”
WISE scanned the whole sky twice in infrared light, finishing early last year, and astronomers are trawling through the results.
And they’ve now found about 2.5 million actively feeding supermassive black holes across the full sky, some more than 10 billion light-years away. About two-thirds of these black holes never had been detected before, as dust blocks their visible light.
Also discovered are around 1,000 of the brightest galaxies known, which can pour out more than 100 trillion times as much light as our sun, as well as churning out new stars.
“These dusty, cataclysmically forming galaxies are so rare WISE had to scan the entire sky to find them,” says Peter Eisenhardt, project scientist for WISE at JPL.
“We are also seeing evidence that these record setters may have formed their black holes before the bulk of their stars. The ‘eggs’ may have come before the ‘chickens’.”
More than 100 of these objects, located about 10 billion light-years away, have now been confirmed using other telescopes. They appear to be more than twice as hot as other infrared-bright galaxies – possibly because their dust is being heated by an extremely powerful burst of activity from the supermassive black hole.
“We may be seeing a new, rare phase in the evolution of galaxies,” says Jingwen Wu of JPL. | 0.885179 | 3.762536 |
The above image is a chart of charged particle flux observations of the Radiation Assessment Detector (RAD) aboard NASA's Mars Science Laboratory (MSL) during approximately 7 months of cruising between Earth and Mars. The inset at the upper-right compares the RAD particle flux observations with those of the Advanced Composition Explorer (ACE) spacecraft for March 5th through 15th. Image Credit: NASA
This is pretty cool. NASA's Mars Science Laboratory (MSL) has not even reached Mars, yet. But MSL is already doing work that benefit's future human spaceflight to Mars.
For nine months, ending in July, the MSL/Curiosity rover acted as a stunt double for astronauts, exposing itself to the same cosmic radiation humans would experience following the same route to Mars. During that time Curiosity was hit by five major solar flares and solar particle events. But rest assured that Curiosity is fine, though the data it transmitted back is invaluable.
Unlike previous Mars rovers, Curiosity is equipped with an instrument that measures space radiation, called the Radiation Assessment Detector (RAD). It counts cosmic rays, neutrons, protons and other particles over a wide range of biologically-interesting energies. RADs prime mission is to investigate the radiation environment on the surface of Mars, but NASA turned it on during the cruise phase so that it could sense radiation en route to Mars as well.
Curiosity’s location inside the spacecraft was key to the experiment. Being inside the MSL aeroshell and heat shield is similar to the way an astronaut would travel in a spacecraft. So Curiosity would absorb deep-space radiation storms the same way real astronauts would. Computer simulations on the effects of radiation exposure can be very complicated. But Curiosity's cruise time gave scientists a chance to measure what happens in a real-life situation.
Only the strongest radiation storms made it inside the spacecraft. Moreover, charged particles penetrating the hull were slowed down and fragmented by their interaction with the spacecraft's metal skin. And in addition, the spacecraft's hydrazine tanks and other components contributed some protection, too.
Data from Curiosity will help sort out how different subsystems block and respond to cosmic rays and solar radiation. This is information designers of human-crewed spacecraft urgently need to know. The MSL mission team plan to publish results in a peer-reviewed journal later this year.
RAD was turned off July 13th in preparation for landing. Mission controllers will turn it on again after Curiosity sets down in Gale crater. Then researchers will learn what radiation awaits astronauts on the surface of Mars itself.
And now, the mission particulars...
The Mars Science Laboratory / Curiosity rover mission is managed for NASA’s Science Mission Directorate, Washington, D.C., by the Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology in Pasadena (Caltech). More information about Curiosity is online at www.nasa.gov/msl and mars.jpl.nasa.gov/msl . You can follow the mission on Facebook at: www.facebook.com/marscuriosity and on Twitter at: www.twitter.com/marscuriosity . | 0.805021 | 3.808892 |
The first thing that is the matter with dark matter is that it is not “dark” at all. It’s invisible. It neither emits nor absorbs light.
The second thing that is the matter with dark matter is that the fate of mankind depends on something that science only “infers” to exist. This invisible, theoretical, dark matter holds the existence of the universe in its unseen “hands”. Scientific principles regarding gravity conclude that without this elusive dark matter every star, planet, and all humans as well, would go flying willy-nilly into outer space.
The third thing that is the matter with dark matter is that if it exists, it is then possible that dark matter creates a parallel, invisible world. All the happenings of another civilization could very well be happening right under our very noses and humankind is completely left out of the loop. How utterly curious. Could this parallel world have a cure for cancer? Does cancer even exist there? Are there political factions squabbling for power? Would such a world even need governance? What a fascinating idea.
These matters are why such a hubbub is made within the scientific community about dark matter. The simplest definition of dark matter is that it is nonluminous (dark, invisible) material that is hypothesized (scientifically assumed) to exist in space. It is thought that it can have different forms such as:
- Cold Dark Matter: particles that are slow moving when compared to the speed of light and interact weakly with ordinary matter and electromagnetic radiation
- Warm Dark Matter: particles with properties that could possibly be sterile neutrinos and/or gravitinos, and travel faster than cold dark matter but slower than hot dark matter
- Hot Dark Matter: (no, not an erotic vampire novel) high-energy particles, moving randomly, and do not interact with electromagnetic radiation
Dark matter is theorized to have been created soon after the Big Bang. Therefore understanding dark matter is critical to understanding and supporting the Big Bang theory. Scientists tend to gravitate toward the theory of the creation of the Universe through the building blocks of cold dark matter after the Big Bang. Structures would grow from the bottom up by smaller objects collapsing because of their own gravity. These collapsed structures would then merge and form larger objects with greater mass. Theorizing that the Universe evolved from cold dark matter collapsing and structural fragments merging resolves the questions of how individual galaxies formed.
Warm dark matter and hot dark matter alone could not hold up under scientific scrutiny as to being the original building blocks of the Universe. Although, it may very well have been a mixed bag of all three forms of dark matter creating structures that ultimately resulted in the Universe as we know it today, such a theory, the Mixed Dark Matter theory, is generally rejected.
The universe that is currently known to man consists of about five percent of matter that is classified as “ordinary”. That means that about five percent of the universe consists of matter with mass that is comprised of atoms, or ions, with a nucleus and protons and neutrons. Cosmologists call these “baryons”. This is the matter humans can see.
If ordinary matter only makes up about five percent of the universe, what is the remaining ninety-five percent made up of? About seventy percent is “dark energy”, or, a theoretical energy in the form of a repulsive force counteracting gravity which results in an accelerated expansion of the universe. Dark matter is thought to make up the balance. It sounds like a recipe straight out of Frankenstein’s laboratory: seven cups of dark energy, three cups of dark matter, and a splash of ordinary matter. Voila, Universe!
Detecting dark matter requires a whole new level of thinking. It does not absorb light. It does not emit light. It produces no detectable levels of electromagnetic radiation. If it’s invisible, and cannot be seen with a telescope, how do cosmologists and astronomers know it exists? Scientists infer the existence of dark matter. When astrophysicists measure the mass of large objects in space, such as stars, they discover discrepancies with regard to gravitational effects. When things just don’t add up, the scientists scratch their heads and ask, “Why do these heavenly bodies generate a gravitational effect that should actually be created by an object with greater mass?”
Questions such as these were being asked as early as 1932 when scientist Jan Oort, a Dutch astronomer, suggested dark matter was to blame for the orbital speed of the stars within the Milky Way galaxy. The following year Swiss astronomer, Fritz Zwicky, also believed dark matter was the culprit for the “missing mass” issue. However, it would take another thirty years before compelling evidence could assist the theory of dark matter in gaining ground in the scientific community.
In the 1960’s and 1970’s, American astronomer, Vera Rubin, was deeply entrenched in her controversial work on galaxy clusters. Working alongside Kent Ford, an astronomer and instrument maker, the pair used his spectrometer design to view the light spectrums of spiral galaxies. Their discovery is called the Rubin-Ford effect.
This phenomenon describes the movement of the Milky Way galaxy relative to sample galaxies. Rubin and Ford theorized that the difference in motion of these galaxies, compared to the Milky Way’s motion, was relative to cosmic microwave background radiation. Rubin then focused on studying the rotation curves of galaxies. This led to the discovery of discrepancies between predicted angular motion of galaxies and the actual observed motion of the galaxies.
The gravity of stars within rotating galaxies is what prevents these galaxies from flying apart. Such strong gravitational forces require immense mass. Rubin’s calculations revealed that such galaxies contained much more mass than could be accounted for by the stars they contained. Attempting to explain this discrepancy became known as the “galaxy rotation problem” and led to the conclusion that dark matter must then exist.
One of Rubin’s observations showed that as much as six times more “dark” mass existed in galaxies than ordinary matter. Her work was highly controversial at the time and continued to be studied, tested, debated and discussed. As more astronomers did their own studies with conclusions that supported Rubin’s assertions, it became well established within the scientific community that most galaxies are predominately “dark matter”.
The result of Rubin and Ford’s work has led to innovative methods of observing galaxies. One such method, gravitational lensing, was used to examine background objects within the Bullet Cluster in attempts to identify the presence of dark matter. Light bends as it travels away from the source to the observer. It is the mass of the observed object which causes the light to bend. The greater the mass, the stronger the gravitational field it creates, thus a greater degree of bending of the rays of light. When light is then bent to a degree greater than would be indicated by the known mass of the astronomical object, dark matter is then assumed to be at play to account for this mathematical anomaly.
Scientists have used gravitational microlensing to conduct large searches throughout the Milky Way galaxy. Astronomical evidence indicates that the universe contains much more matter than what is visible to mankind. Some scientists have even speculated that a parallel world is possible that consists of dark matter and can only interact with the universe as we know it through gravity.
When measuring the velocity of rotation as compared to the distance from the center of a spiral galaxy, such as the Milky Way galaxy, the mathematical discrepancy reveals that the cluster’s mass consists of very little of the ordinary matter objects that are visible. Scientists then suggest that dark matter is concentrated in a halo formation surrounding the visible matter. A dark matter parallel world could perhaps be found in the “halos” around astronomical objects. Since dark matter contains no atoms, like ordinary matter, it cannot interact with ordinary matter through electromagnetics. Dark matter contains no electrical charge. Hence, gravity is the only interactive relationship between dark matter and ordinary matter as the theory is understood at this time.
Spiral galaxies are not alone in containing dark matter. Studies conducted with gravitational lensing reveal that dark matter may very well be present in elliptical galaxies. Within dark halos that surround such galaxies, X-ray emissions indicate atmospheric extensions of hot gas which could support the existence of dark matter. Using X-ray emissions to estimate dark matter existence is achieved by measuring the energy and fluctuation of the X-rays. These measurements can be used to estimate the temperature and density of the gas producing the X-rays as well as the pressure of the gas. A profile of mass can be created by assuming that the gas pressure balances with the present gravity. Discrepancies would then be attributed to dark matter.
As with anything, there are, of course, exceptions to the rule. Globular clusters are thought to perhaps contain no dark matter. Cardiff University astronomers discovered galaxy VIRGOHI21 in 2005 and believe it to be made up entirely of dark matter and absent of any visible stars. So, there is diversity and oddities even amongst the stars.
Dark matter within our very own Milky Way galaxy is, apparently, “wimpy”. Every second of every day millions, perhaps even billions, of weakly interacting massive particles, also known as WIMPs, pass through this globe humans call home. Experiments of detection are vigorously underway searching for these invisible invaders. Because WIMPs do not interact with matter, it is thought that they can be detected by measuring energy and momentum discrepancies as they zip about, collide and annihilate each other. This is one of the studies conducted in supercolliders.
What does the discovery of dark matter mean for mankind? For the scientific community, it is simply another wonderful puzzle to be solved. For the regular person moving through life every day, it might mean a new awareness of the possibility of an invisible world right next to you. Average people who simply want to rise from a chair and cross the room may find themselves compelled to politely mutter the words, “Please excuse me.” These words may appear to be uttered to an empty room containing no one who needs their pardon begged. No, these people are not crazy and talking to themselves, they are simply considering that the room could contain invisible, dark matter co-habitants that find it very disturbing when a human walks right through them without even a, “How do you do?” | 0.815342 | 3.034078 |
Over the past few days a pair of spectacular fireballs have graced Australia’s skies.
The first, in the early hours of Monday, May 20, flashed across the Northern Territory, and was seen from both Tennant Creek and Alice Springs, more than 500km apart.
The second came two days later, streaking over South Australia and Victoria.
Such fireballs are not rare events, and serve as yet another reminder that Earth sits in a celestial shooting gallery. In addition to their spectacle, they hold the key to understanding the Solar system’s formation and history.
Crash, bang, boom!
On any clear night, if you gaze skyward long enough, you will see meteors. These flashes of light are the result of objects impacting on our planet’s atmosphere.
Specks of debris vaporise harmlessly in the atmosphere, 80-100km above our heads, all the time – about 100 tons of the stuff per day.
The larger the object, the more spectacular the flash. Where your typical meteor is caused by an object the size of a grain of dust (or, for a particularly bright one, a grain of rice), fireballs like those seen this week are caused by much larger bodies – the size of a grapefruit, a melon or even a car.
Such impacts are rarer than their tiny siblings because there are many more small objects in the Solar system than larger bodies.
That was probably the largest impact on Earth for 100 years, and caused plenty of damage and injuries. It was the result of the explosion of an object 10,000 tonnes in mass, around 20 metres in diameter.
On longer timescales, the largest impacts are truly enormous. Some 66 million years ago, a comet or asteroid around 10km in diameter ploughed into what is now the Yucatan Peninsula, Mexico. The result? A crater some 200km across, and a mass extinction that included the dinosaurs.
Even that is not the largest impact Earth has experienced. Back in our planet’s youth, it was victim to a truly cataclysmic event, when it collided with an object the size of Mars.
When the dust and debris cleared, our once solitary planet was accompanied by the Moon.
Impacts that could threaten life on Earth are, thankfully, very rare. While scientists are actively searching to make sure no extinction-level impacts are coming in the near future, it really isn’t something we should lose too much sleep about.
Smaller impacts, like those seen earlier this week, come far more frequently – indeed, footage of another fireball was reported earlier this month over Illinois in the United States.
In other words, it is not that unusual to have two bright fireballs in the space of a couple of days over a country as vast as Australia.
Pristine relics of planet formation
These bright fireballs can be an incredible boon to our understanding of the formation and evolution of the Solar system. When an object is large enough, it is possible for fragments (or the whole thing) to penetrate the atmosphere intact, delivering a new meteorite to our planet’s surface.
Meteorites are incredibly valuable to scientists. They are celestial time capsules – relatively pristine fragments of asteroids and comets that formed when the Solar system was young.
Most meteorites we find have lain on Earth for long periods of time before their discovery. These are termed “finds” and while still valuable, are often degraded and weathered, chemically altered by our planet’s wet, warm environment.
By contrast, “falls” (meteorites whose fall has been observed and that are recovered within hours or days of the event) are far more precious. When we study their composition, we can be confident we are studying something ancient and pristine, rather than worrying that we’re seeing the effect of Earth’s influence.
Tracking the fireballs
For this reason, the Australian Desert Fireball Network has set up an enormous network of cameras across our vast continent. These cameras are designed to scour the skies, all night, every night, watching for fireballs like those seen earlier this week.
If we can observe such a fireball from multiple directions, we can triangulate its path, calculate its motion through the atmosphere, and work out whether it is likely to have dropped a meteorite. Using that data, we can even work out where to look.
In addition to these cameras, the project can make use of any data provided by people who saw the event. For that reason, the Fireballs team developed a free app, Fireballs in the Sky.
It contains great information about fireballs and meteor showers, and has links to experiments tied into the national curriculum. More importantly, it also allows its users to submit their own fireball reports.
As for this week’s fireball over southern Australia, NASA says it was probably caused by an object the size of a small car. As for finding any remains, they are now likely lost in the waters of the Great Australian Bight. | 0.883931 | 3.731519 |
Enshrouded in a dense golden hydrocarbon mist, Saturn's largest moon Titan is a mysterious mesmerizing world in its own right. For centuries, Titan's veiled, frigid surface was completely camouflaged by this hazy golden-orange cloud-cover that hid its icy surface from the prying eyes of curious observers on Earth. However, this misty moisty moon-world was finally forced to show its mysterious face, long-hidden behind its obscuring veil of fog, when the Cassini Spacecraft's Huygens Probe landed on its surface in 2004, sending revealing pictures back to astronomers on Earth. In September 2018, astronomers announced that new data obtained from Cassini show what appear to be gigantic, roaring dust storms, raging through the equatorial regions of Titan. The discovery, announced in the September 24, 2018 issue of the journal Nature Geoscience, makes this oddball moon-world the third known object in our Solar System--in addition to Earth and Mars--where ferocious dust storms have been observed. The observations are now shedding new light on the fascinating and dynamic environment of Titan, which is the second largest moon in our Solar System, after Ganymede of Jupiter. Envision that astrology is made up of the study of all of the planets and the sun. The astrological birth chart and the study of how planetary alignments affect sun signs are based on these aspects of astrology. The moon actually influences this overall picture, and can cause certain aspects of astrological phenomena to influence our lives differently than was otherwise predicted. However, it was little Enceladus that gave astronomers their greatest shock. Even though the existence of Enceladus has been known since it was discovered by William Herschel in 1789, its enchantingly weird character was not fully appreciated until this century. Indeed, until the Voyagers flew past it, little was known about the moon. However, Enceladus has always been considered one of the more interesting members of Saturn's abundantly moonstruck family, for a number of very good reasons. First of all, it is amazingly bright. The quantity of sunlight that an object in our Solar System reflects back is termed its albedo, and this is calculated primarily by the color of the object's ground coating. The albedo of the dazzling Enceladus is almost a mirror-like 100%. Basically, this means that the surface of the little moon is richly covered with ice crystals--and that these crystals are regularly and frequently replenished. When the Voyagers flew over Enceladus in the 1980s, they found that the object was indeed abundantly coated with glittering ice. It was also being constantly, frequently repaved. Immense basins and valleys were filled with pristine white, fresh snow. Craters were cut in half--one side of the crater remaining a visible cavity pockmarking the moon's surface, and the other side completely buried in the bright, white snow. Remarkably, Enceladus circles Saturn within its so-called E ring, which is the widest of the planet's numerous rings. Just behind the moon is a readily-observed bulge within that ring, that astronomers determined was the result of the sparkling emission emanating from icy volcanoes (cryovolcanoes) that follow Enceladus wherever it wanders around its parent planet. The cryovolanoes studding Enceladus are responsible for the frequent repaving of its surface. In 2008, Cassini confirmed that the cryovolanic stream was composed of ordinary water, laced with carbon dioxide, potassium salts, carbon monoxide, and a plethora of other organic materials. Tidal squeezing, caused by Saturn and the nearby sister moons Dione and Tethys, keep the interior of Enceladus pleasantly warm, and its water in a liquid state--thus allowing the cryovolcanoes to keep spewing out their watery eruptions. The most enticing mystery, of course, is determining exactly how much water Enceladus holds. Is there merely a lake-sized body of water, or a sea, or a global ocean? The more water there is, the more it will circulate and churn--and the more Enceladus quivers and shakes, the more likely it is that it can brew up a bit of life. | 0.852443 | 3.782676 |
[[UPDATE: Talk about good timing! I guess the person who wrote this article, dated today, does need Columbo; –MSH]]
I’m hoping my reference to the venerable TV detective doesn’t date me too much here!
Way back in 2009 I wrote the only post on this blog about the so-called “Sirius Mystery.” This mystery has to do with how a primitive African tribe, the Dogon, had advanced knowledge of a system of stars that make up what we see with the naked eye as one star — Sirius. My post was brief, directing readers’ attention to another brief, but well done, post on the Bad Archaeology website devoted to the subject, as well as two articles on how the Dogon could have visually seen “beyond” the single star Sirius. (After all, that is the issue — how did they know that naked eye Sirius is actually a cluster of stars?) It doesn’t take much imagination to discern that this is serious (pardon the pun) fodder for ancient astronaut believers.
It’s time to revisit the “Sirius Mystery” in a bit more detail. There has been some additional recent work on the subject by anthropologists to which I want to draw your attention. But to make it easier to follow, let’s start at the beginning.
The Dogon and Sirius
The Bad Archaeology page on the Sirius Mystery has summarize the basic details well:
In 1976, Robert K G Temple (born 1945), an American living in the UK, published what was to become a seminal work of Bad Archaeology, The Sirius Mystery. A revised edition was published in 1998 with the new subtitle New scientific evidence of alien contact 5,000 years ago…. Temple begins with the work of Marcel Griaule (1898-1956) and Germaine Dieterlen (1903-1999), a pair of French anthropologists who worked in what is now Mali from 1931 to 1956. They reported an apparently anomalous knowledge of astronomy that formed part of the traditional lore of the Dogon, a people of the central plateau of Mali. This knowledge is alleged to include accounts of the rings of Saturn, the presence of four moons orbiting Jupiter and, most surprisingly of all, an account of two companions of the star Sirius. Griaule first published this data in Dieu d’eau (‘God of Water’, 1948), in which he records his conversations with a blind hunter, Ogotemmêli, who claimed to have extensive knowledge of Dogon lore, much of which was restricted to certain tribal elders. Griaule and Dieterlen were able to synthesise the cosmogony from Ogotemmêli’s statements. Temple was most impressed by the Dogon belief in a complex system of stars making up what we see as the single star, Sirius. This is the brightest star in our skies and, according to the Dogon, as reported by Griaule and Dieterlen, is actually a bright star with several smaller (even ‘invisible’) companions. Focusing especially on a representation of the system drawn by Ogotemmêli (who, it must be remembered, was blind), Temple recognised the highly elliptical orbit of Sirius B, a white dwarf first photographed in 1970, around the principal star of the system, Sirius A. Moreover, Temple found reference to a third component of the system, dubbed Sirius C by the astronomers who accepted its existence (its existence had been suggested but never observed). According to the Dogon, this knowledge had been imparted by the Nommo, fish-like water spirits, in the distant past.
From this information, Temple goes on to theorize that the “fish-like water spirits” were extraterrestrials. He finds proof for his notion from the Babylonian writer Berosssus who wrote of a hybrid fish-man who “emerged from the Persian Gulf to teach humanity various arts of civilisation. This creature is thought to be the Uan (or Uanna) of Babylonian myth, sometimes identified with Adapa, the equally mythical first king of Eridu, also identified by some with Atrahasis, the hero of the Babylonian version of the flood legend.” (Bad Archaeology)
While this string of non-sequiturs on the ancient Mesopotamian material is interesting enough, I want to stick to the item that started Temple down this rabbit hole: the Dogon knowledge of Sirius.
Recent Work on the Dogon and Sirius: 1980s and 1990s
In my earlier post on this subject, I linked readers to two essays from the book Blacks in Science: Ancient & Modern (Journal of African Civilizations), by Ivan Van Sertima (Transaction Publishers, 1983). The first essay speculated about whether the Dogon may have had a primitive optical instrument and, more importantly, how early Chinese records indicated that astronomers had been able to make naked eye observations of one of Jupiter’s moons. Another example came from an 1852 letter from a missionary who documented the same observation. Further, under optimal conditions, people in contemporary times with good visual acuity can see two galaxies (M31, the Andromeda) and M33 (a spiral galaxy in the constellation Triangulum) with the naked eye. These examples are concrete, secure parallels to the Dogon knowledge of the Sirius cluster. No aliens needed. The article went on to discuss techniques used by ancients for making such observations (called “dark eye” techniques). The second essay discusses how the Dogon may have been able to see Sirius B, a star in the cluster that, due to its high magnitude, should not be viewable to the naked eye. Collectively, these essays show there is no reason to suspect that a member of the ancient Dogon tribe, or others at any other place on the globe, thousands of years ago, could not see these things. This undermines the entire premise of Temple and his Sirius Mystery.
The Bad Archaeology site notes:
… by the time Temple had published the second edition of The Sirius Mystery in 1998, the whole question of the Dogon’s apparently inexplicable knowledge of Sirius had been blown apart. No-one had questioned Griaule and Dieterlen’s findings until the early 1990s. And this is where the problems for the hypothesis began. In 1991, the anthropologist Walter van Beek undertook fieldwork among the Dogon, hoping to find evidence for their knowledge of Sirius. As the earlier authors had indicated that aorund 15% of the adult males were initiated into the Sirius lore, this ought to have been a relatively easy task. However, van Beek was unable to find anyone who knew about Sirius B. As ought to have been obvious from the outset, Griaule and Dieterlen’s reliance on a single informant – Ogotemmêli – severely compromises the validity of their data. But it gets worse. The Dogon themselves do not agree that Sigu tolo is Sirius: it is the bright star that appears to announce the beginning of a festival (sigu), which some identify with Venus, while others claim it is invisible. To polo is not Sirius B, as it sometimes approaches Sigu tolo, making it brighter, while it is sometimes more distant, when it appears as a group of twinkling stars (which sounds like a description of the Pleiades). All in all, the ‘inexplicable’ astronomical knowledge turns out to be too confused to bear the interpretation put on it by Griaule and Dieterlen.
The research of van Beek (and co-authors) alluded to above can be found in this 1991 article:
Walter E. A. van Beek, R. M. A. Bedaux, Suzanne Preston Blier, Jacky Bouju, PeterIan Crawford, Mary Douglas, Paul Lane, Claude Meillassoux, “The Dogon Restudied: A Field Evaluation of the Work of Marcel Griaule [and Comments and Replies],” Current Anthropology Vol. 32, No. 2 (Apr., 1991), pp. 139-167
The abstract of the article notes:
“This restudy of the Dogon of Mali asks whether the texts produced by Marcel Griaule depict a society that is recognizable to the re- searcher and to the Dogon today and answers the question more or less in the negative. The picture of Dogon religion presented in Dieu d’eau and Le renard pale proved impossible to replicate in the field, even as the shadowy remnant of a largely forgotten past. The reasons for this, it is suggested, lie in the particular field situation of Griaule’s research, including features of the ethnographer’s approach, the political setting, the experience and predilections of the informants, and the values of Dogon culture.”
Note: In what follows, van Beek uses the following abbreviations for books written by Griaule on the Dogon:
DE = In Dieu d’eau: Entretiens avec Ogotemmeli [“God of Water: Conversations with Ogotemmeli”] (Griaule 1948, hereafter DE); this is the book that made Griaule world-famous. It was published before his collaboration with Dieterlen — the next book:
RP = Le renard pale [“The Pale Fox”] (Griaule and Dieterlen I965, hereafter RP); this book is the one referred to by Bad Archaeology. It is the one that contains most of the material about Sirius and the Dogon.
I recommend the article to readers, as it has a very good summary of Dogon cosmology (pp. 140-141, 148-151), drawing on DE and RP, and the fact that the cosmological recounting of the single informant of Griaule and Dieterlen (Ogotemmêli) differs from all other Dogon accounts. This means that, among other issues, the source upon which Robert Temple based his ancient astronaut speculations are quite idiosyncratic, as the Bad Archaeology site noted. Van Beek goes even further than that, though. Quoting from his re-study, Van Beek notes that the views of Ogotemmêli are simply not recognizable to those leaders he talked to (p. 148) and “that Sirius is a double star is unknown; astronomy is of very little importance in religion. Dogon society has no initiatory secrets beyond the complete mastery of publicly known texts . . . The water spirit Nommo is not a central figure in Dogon thought and has none of the characteristics of a creator or a redeemer … Cosmological symbolism is not the basis of any Dogon cultural institutions . . . Confronted with parts of the stories provided by Ogotemmeli or given in the Renard pale, my informants emphatically state that they have never heard of them.” (p. 148)
On page 149 van Beek adds:
Is Sirius a double star? The ethnographic facts are quite straightforward. The Dogon, of course, know Sirius as a star (it is after all the brightest in the sky), calling it dana tolo, the hunter’s star (the game and the dogs are represented by Orion’s belt). Knowledge of the stars is not important either in daily life or in ritual. The position of the sun and the phases of the moon are more pertinent for Dogon reckoning. No Dogon outside the circle of Griaule’s informants had ever heard of sigu tolo or p6 tolo, nor had any Dogon even heard of eme ya tolo (according to Griaule in RP Dogon names for Sirius and its star companions). Most important, no one, even within the circle of Griaule informants, had ever heard or understood that Sirius was a double star (or, according to RP, even a triple one, with B and C orbiting A). Consequently, the purported knowledge of the mass of Sirius B or the orbiting time was absent. The scheduling of the sigu ritual is done in several ways in Yugo Doguru, none of which has to do with the stars.” (pp. 149-150)
In a nutshell, the foundation of Robert Temple’s Sirius Mystery (and the nonsense that has accrued to it since its publication) consists of three conversations with one Dogon tribesman, whose ideas differ from all subsequent Dogon elders interviewed to date. (And then there are the flaws in what Temple does with this idiosyncratic musings). Nice. A word like “flimsy” doesn’t begin to tell the story.
Contemporary Work on the Dogon: 2004
In 2004 Dr. van Beek published an essay in a scholarly journal that is, in essence, a retrospect of his work on Griaule of 1991 and the Sirius silliness:
Walter E. A. van Beek, “Haunting Griaule: Experiences from the Restudy of the Dogon,” History in Africa 31 (2004), pp. 43-68
Van Beek begins the article whimsically:
“It really was a chance occasion, just before Christmas 2003. On my way to the Dogon area I had greeted my friends in Sangha, and was speaking with a Dutch friend, when a French tourist lady suddenly barged into the hall of the hotel and asked me: “There should be a cav- ern with a mural depicting Sirius and the position of all the planets. I saw it in a book. Where is it?”. My friend smiled wrily, amused by the irony of situation: by chance the lady had fallen upon the one who had spent decennia to disprove this kind of “information”. “In what book?” I asked, and named a few. It was none of these, and she could not tell me. Cautiously (maybe she had planned her whole trip around this Sirius “experience”) I explained to her that though there was a lot to see, this particular mural did not exist. She left immediately, proba- bly convinced she stumbled on a real ignoramus.”
I wonder what book the lady had read (!)
Van Beek’s essay tells the reader how his decades-long interest in the Dogon began (it had nothing to do with Griaule) and how that interest drew him into pop (cult, fringe) archeology and anthropology. It’s an interesting, light read for the most part. Some excerpts are worth citing for our purposes here:
But at the time-we are writing 1979 for the start of my own field- work-the Griaule ethnography had already come under criticism. The most severe came from a Belgian dissertation by Dirk Lettens, defended at Nijmegen University under Albert Trouwborst (Lettens 1971). Later, after the publication of my Current Anthropology article, Trouwborst-with whom I shared many interuniversity committees, as well as the board of the Dutch Africanist Association-confided me that at the time he thought Lettens overly critical: surely it could not have been that bad. But Lettens was right on target. His title, Mythagogie et Mystification, still is unsurpassed as a characterization of Griaule’s post-1948 writings. Although criticism was given in many countries, (Saccone 1984), the discussion through David Tait (1950), Mary Douglas (1967, 1968) and eventually James Clifford (1983) was to be much more influential. (p. 48)
One wonders why Robert Temple’s work on the “Sirius Mystery” fails to interact with these criticisms of Griaule. Simply put, that isn’t how scholarship is done.
Van Beek continues:
All these discussions, however, were based on secondary sources. It was astonishing how little genuine fieldwork had been done after Griaule’s untimely death in 1956. The publication of Le Renard pale was clearly the outcome of his own work, finished by Germaine Dieterlen. She was still publishing, wholly within his tradition. The same holds for the only other major publication based on field data, the work of Genevieve Calame-Griaule, his daughter. She published a major study on Dogon language cum culture, in which she combined her father’s approach with the results of her own linguistic research. . . . The problem started with what is still the best known publication of Griaule, his small book describing his talks with a blind Dogon elder Ogotemmelli, under the title Dieu d’eau (Griaule 1948) (=DE above), translated in English under its French subtitle: Conversations with Ogotemmelli. . . . The book was a tremendous success and was translated into over twenty languages. (p. 49)
Griaule’s ethnography proved to be incoherent. Griaule’s later publications, which incidentally never could match his first success nor receive the wide circulation and renown of Ogotemmelli, depicted yet another Dogon culture. The posthumously published Le Renard pale (Griaule/Dieterlen 1956) and the articles leading up to it (Griaule 1954, Griaule/Dieterlen 1950) came up with even “deeper” myths, systems of classification, and a totally different creation story, at least with a totally different construction of the myth. These two sets of creation myths, of 1948 and 1956, are totally incon- sistent with each other … (p. 50)
Renard pale (= RP above) picked up one major following, somewhat to the embarrassment of Dieterlen. One of its spectacular “findings” had to do with astronomy. The Dogon ritual calendar allegedly was dominat- ed by a star system, that of Sirius, the main star in the constellation of Canis Major. The message of the book was that Sirius had a small white dwarf companion, Sirius B, whose revolving time punctuated the long-term rhythm of Dogon ritual life, such as the famous sigi cycle. An even smaller companion (the presumed Sirius C) then circled Sirius B. The notion of Sirius as a double star is an astronomical fact (though Sirius C is not known and has never been observed). But then, how did the Dogon know this? The naked eye cannot detect the white dwarf. The most extended treatment of this problem was given by Robert Temple in a book that has long haunted popular astronomy, The Sirius Mystery, published in 1976, (reprinted in 1999). Temple took the Dogon data as unvarnished truth and questioned how this knowledge arrived at the Bandiagara cliff. He found the answers in Egypt, and thus became a kind of trailblazer for a whole generation of authors who were even less restrained. For those convinced of extra-terrestrial visits to the planet Earth, an idea very much in vogue during the late seventies … “Cosmonautologists” like von Diniken [sic], Guerrier (1975) and many others of their ilk had a field day with this material and the Dogon enigma quickly became established as one of the pillars in their empir- ical grounding of the “flying saucer vision” and extraterrestrial inter- pretations of the pyramids. In their reasoning the implications of the Dogon “facts” were clear: there was no way the Dogon without any astronomical instruments could know these exotic facts. Definitely this implied that they must have been taught these astronomical lessons by extraterrestrials. Thus, the Dogon notion of Sirius B (C was conve- niently forgotten) came on a par with the riddles of the Gizeh pyra- mids, the Nazca lines and Stonehenge. (pp. 50-51)
The article has a good deal else. I especially like the part where, after years spent becoming accepted by the Dogon, he began to carefully expose them to the ideas that Griaule had “learned” from Ogotemmelli, only to have his Dogon friends burst out laughing! One of the major services is van Beek’s lengthy descriptions (with illustrations) of how Griaule came to create the myths of the Dogon himself (which were uncritically absorbed by Temple and passed on to the populace in his book). Basically, there was a good amount of cultural mis-communication. Van Beek relates several anecdotes you can read for yourself, but his own epiphany in this regard is worth quoting here:
Recently, in her excellent study of Dogon masks, Anne Doquet has zoomed in on one aspect I rather neglected, i.e. the conversations with Ogotemmelli themselves, and the fieldwork genesis of the first “Griaulian myths” (Doquet 1999:90-91). Analyzing Griaule’s field notes in detail from microfiches, she noticed the two-fold influence Griaule had exerted on the material he collected with the old man. This period, from 20 October 1946 to 2 December 1946, marked his famous conversations. The field notes are a haphazard collection of ref- erences to Dogon symbols and pieces of mythology, a veritable bricolage of odds and ends, without coherence or internal consistency. However, the book gives an account of a series of systematic revela- tions, each startling myth and intricate symbol tying in nicely with the great revelations of the former day, and logically leading to the revela- tions yet to come. Recently, in her excellent study of Dogon masks, Anne Doquet has zoomed in on one aspect I rather neglected, i.e. the conversations with Ogotemmelli themselves, and the fieldwork genesis of the first “Griaulian myths” (Doquet 1999:90-91). Analyzing Griaule’s field notes in detail from microfiches, she noticed the two-fold influence Griaule had exerted on the material he collected with the old man. This period, from 20 October 1946 to 2 December 1946, marked his famous conversations. The field notes are a haphazard collection of ref- erences to Dogon symbols and pieces of mythology, a veritable brico- lage of odds and ends, without coherence or internal consistency. However, the book gives an account of a series of systematic revela- tions, each startling myth and intricate symbol tying in nicely with the great revelations of the former day, and logically leading to the revela- tions yet to come. (p. 59)
Van Beek’s account of how his 1991 critique of Griaule and his co-author Dieterlen was received — by Dieterlen herself — is also of interest:
Before submitting it to the editor, I decided to give Dieterlen a chance at first reaction. She read English only with difficulty, as I knew, so I translated the article into French, sent her a copy, and made an appointment. When I arrived at her apartment in Paris, she received me as gracefully as ever. She had been expecting a publication for some time, and appreciated my effort to give her the chance at a first reaction and my effort at making a (passable) French version. She had also admired the French version of the Time-Life book (Pern/Alexander/van Beek 1982) I had sent her some time before. In that publication I had avoided the question of Griaulian validity, as a book for the general public should not be burdened with a detailed academic debate. I braced myself for a long critique, but she had just one question: “Pourqois le publier?” Only that, why publish? She had no answer to my arguments, in fact during our two-hour conversation that followed she never ventured into the content of the article at all, but just pleaded not to publish it. It was, evidently, also the most difficult question to answer, and one I had been reflecting on very long. I answered, truth- fully I think, that publishing is the very soul of science, and that debate is the way to proceed in getting closer to the truth. She had no comments on that, but instead started reminiscing on the past. (pp. 62-63; emphasis mine – MSH)
Think about that. The only other person alive who could rebut van Beek’s criticisms of the Dogon “knowledge” had nothing to say in rebuttal, even in private. All she wanted was for the criticisms not to be published. | 0.884419 | 3.113689 |
Today’s job: Discovering two ninja moves that will allow us to pack way more worlds in the habitable zone.
The last post (part 3: choosing the right orbits) was pretty simple stuff. You can cram more small planets into the habitable zone than big ones. Nothing too shocking. Well, learning the basics always comes before the ninja moves.
What makes these moves ninja (to use ninja as an adjective) is that they put more than one world on the same orbit. This means that we can pack a lot more worlds into our star’s habitable zone. It’s like the 6-pack: a way to cram more awesomeness into a limited space.
Let’s meet the ninjas.
NINJA MOVE 1: MOONS. A planet’s moons orbit the star just like the planet does. I used this to my advantage this when I built a better Solar System.
Here are the large moons in the Solar System:
The biggest Solar System moons orbit the biggest planets (Jupiter and Saturn). Systems of moons form like mini-Solar Systems, in disks of gas and dust around gas giant planets. [In fact, large Solar System moons have some properties in common with extra-solar planets]. The moons are located very close to the gas giants. The orbits of the most distant large moons are only about 30 times larger than the radius of their host planet. In comparison, Earth’s orbit is about 200 times larger than the radius of the Sun.
We want worlds in our ultimate Solar System that are a little bigger than these large moons. We want worlds about half to twice Earth’s size. Although there is some debate, I’m going to allow any gas giant that is Saturn-sized or larger to have large moons.
In the Solar System, Jupiter has the most (four). Given how close-in the Solar System moons are located, large moons are likely to stay close. But how many big moons could a gas giant have? Well, at least as many as Jupiter (four). But probably not that many more. The orbits of planets and moons tend to be spaced logarithmically. Think, 1, 10, 100, 1000 rather than 10, 20, 30, 40. The farther from the star/planet, the bigger the spaces between planets/moons. If the zone with large moons extends from 5 to 50 times the planet’s radius, this only gives us room for 5 large moons spaced like Jupiter’s. We’ll stick with a maximum of 5 large moons per gas giant planet.
Could a planet like Earth have a moon large enough for life? The jury is still out on how to form such a moon (probably by a giant impact between two big growing planets). But there is no reason not to consider this possibility. However, an Earth-sized planet probably could not have more than one large moon remain stable. [Note that Earth may have had a second large moon that crashed into the Moon!] In fact, if an Earth-sized planet had an Earth-sized moon, this would essentially be a binary planet. Each planet would orbit the other, as the pair orbited the star. Pretty awesome concept! Pluto and Charon are basically a binary (minor) planet. Charon is about half as big as Pluto and about 10% as massive.
A binary Earth would behave mostly like the Earth-Moon system does today. But tides would be much stronger. The two Earths always show each other the same face as their orbit their common center of gravity.
The planets each make one full rotation for each orbit around each other. This means that a day should be about a month in length. This may have some impact on the planets’ climate, but probably in a good way. Slowly-rotating planets may remain habitable closer to their stars than fast-rotating planets.
NINJA MOVE 2: CO-ORBITAL PLANETS. When you hear the word “Trojan”, you probably don’t think of asteroids. But they are real! What is interesting about the Trojan asteroids is that they share the same orbit as Jupiter. And so do the “Greek” asteroids. This image shows where these asteroids are located.
The Trojan and Greek asteroids are about 60 degrees in front of and behind Jupiter. Normally, when an asteroid comes close to Jupiter, the planet’s strong gravity deflects the asteroid. Eventually the asteroid’s orbit takes it close to Jupiter. Jupiter launches the asteroid out of the Solar System.
The Trojan and Greek asteroids live on islands of stability. It turns out that the positions 60 degrees ahead and behind Jupiter are protected from its strong gravity. These are called the L4 and L5 points (the L is for Lagrange, who discovered that they are stable). Since they share the same orbit, they are also called co-orbitals.
Asteroids that orbit at L4 or L5 are stable. They can orbit happily at those points forever. They don’t stay exactly at L4 or L5; rather, they trace little circles about those points. That is why the Trojans and Greeks are clouds instead of all being found at a single point.
Co-orbital (aka Trojan) planets are like a person walking with a man-eating tiger but always staying behind it, just in its blind spot. Perfectly safe, it turns out, but with mortal (gravitational) danger right nearby.
L4 or L5 would be stable islands for an Earth-sized planet. Even one with a large moon. In fact, two Earth-sized planets — one at L4 and one at L5 — could be stable. In some circumstances L4 or L5 could even be stable for another gas giant (but just one).
Now switch out Jupiter for Earth. Earth also has L4 and L5 points. Earth even has a Trojan asteroid. Two Earth-sized planets can share an orbit in their mutual L4/L5 points. Separated by 60 degrees, the two planets’ orbits are stable.
Systems of planets that include co-orbitals have to be a bit more widely-spaced. Otherwise they become unstable. That means that we can’t cram quite as many orbits into the habitable zone.
Even though there are fewer orbits in the habitable zone, there are more planets. With just one planet per orbit we were able to fit 14, 7, and 3 orbits of planets of 0.1, 1 or 10 times Earth’s mass. Including co-orbitals we can only fit 9, 5 and 2 orbits. But two planets per orbit makes it 18, 10 and 4 planets in the habitable zone. Give them each a large moon and the numbers are doubled. Boom!
As we saw previously, a system of gas giant planets tends to have different orbital spacing (in resonances). The gravitational effects of Earth-sized Trojan planets don’t change anything in that case. So we could still fit four gas giant planets in the habitable zone of our chosen star. Of course, we can add in some ninja moves there too…
SUMMARY: Given one planet orbiting a star, stable islands exist on the same orbit: 60 degrees in front and 60 degrees behind the planet. A gas giant planet can have an Earth-sized planet in each of these points with no effect on orbital stability. Two (but not three) Earth-sized planets can share the same orbit, separated by 60 degrees. These are called co-orbital or Trojan planets. Wider orbital spacing is needed for a system of co-orbital planets.
OVERALL SUMMARY: We are becoming ninjas! With moons and co-orbitals, many worlds can share the same orbit. This means we can pack more Earth-sized worlds into the habitable zone. | 0.864452 | 3.465776 |
Moon* ♐ Sagittarius
Moon phase on 24 May 2013 Friday is Waxing Gibbous, 14 days young Moon is in Scorpio.Share this page: twitter facebook linkedin
Previous main lunar phase is the First Quarter before 6 days on 18 May 2013 at 04:35.
Moon rises in the afternoon and sets after midnight to early morning. It is visible to the southeast in early evening and it is up for most of the night.
Moon is passing about ∠24° of ♏ Scorpio tropical zodiac sector.
Lunar disc appears visually 3.2% wider than solar disc. Moon and Sun apparent angular diameters are ∠1955" and ∠1894".
Next Full Moon is the Flower Moon of May 2013 after 1 day on 25 May 2013 at 04:25.
There is medium ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at very acute angle, so their combined tidal force is moderate.
The Moon is 14 days young. Earth's natural satellite is moving from the first to the middle part of current synodic month. This is lunation 165 of Meeus index or 1118 from Brown series.
Length of current 165 lunation is 29 days, 15 hours and 28 minutes. This is the year's longest synodic month of 2013. It is 10 minutes longer than next lunation 166 length.
Length of current synodic month is 2 hours and 44 minutes longer than the mean length of synodic month, but it is still 4 hours and 19 minutes shorter, compared to 21st century longest.
This New Moon true anomaly is ∠143.3°. At beginning of next synodic month true anomaly will be ∠168.8°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
10 days after point of apogee on 13 May 2013 at 13:31 in ♊ Gemini. The lunar orbit is getting closer, while the Moon is moving inward the Earth. It will keep this direction for the next day, until it get to the point of next perigee on 26 May 2013 at 01:45 in ♐ Sagittarius.
Moon is 366 614 km (227 803 mi) away from Earth on this date. Moon moves closer next day until perigee, when Earth-Moon distance will reach 358 375 km (222 684 mi).
Moon is in ascending node in ♏ Scorpio at 00:40 on this date, it crosses the ecliptic from South to North. Moon will follow the northern part of its orbit for the next 12 days to meet descending node on 6 June 2013 at 00:59 in ♉ Taurus.
At 00:40 on this date the Moon is completing its previous draconic month and is entering the new one.
11 days after previous North standstill on 12 May 2013 at 12:30 in ♊ Gemini, when Moon has reached northern declination of ∠20.170°. Next day the lunar orbit moves southward to face South declination of ∠-20.182° in the next southern standstill on 26 May 2013 at 04:47 in ♐ Sagittarius.
After 1 day on 25 May 2013 at 04:25 in ♐ Sagittarius, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.848363 | 3.11128 |
In this VIS image, taken by the NASA - Mars Odyssey Orbiter on April, 28th, 2014, and during its 54.883rd orbit around the Red Planet, we can see a very small portion of the Martian Volcanic sub-Region (whose total length is approx. 240 Km - such as about 149,04 miles) known as Rubicon Valles: in fact, Rubicon Valles is a Complex sub-Region full of Channels (all of them having, according to Logic as well as to the studies that have been carried out so far by Planetary Scientists, a Volcanic Origin) that is located on the North/Western Flank of the large Martian Volcano named Alba Mons.
Even in this specific case, the general Cratering of the area is relatively low, and all the visible Impact Craters appear to be small-to-medium-sized and quite young (Geologically speaking). An interesting (yet tiny) Crater-Cluster can be seen on the lower right (Dx) margin of the picture; notice - also - that a few Impact Craters which appear to be "Double" are, in fact, Single Craters. The reason of such a misleading appearence is due to a poorly-made assembling of the different frames that form the full image.
Latitude (centered): 45,1688° North
Longitude (centered): 243,2630° East
This image (which is a crop taken from an Original Mars Odyssey Orbiter b/w and Map-Projected frame published on the NASA - Planetary Photojournal with the ID n. PIA 18546) has been additionally processed, magnified to aid the visibility of the details, contrast enhanced and sharpened, Gamma corrected and then colorized in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Mars Odyssey Orbiter and then looked down, towards the Surface of Mars), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team. | 0.867817 | 3.605679 |
Micro Moon – What is a Micro Moon?
hat is a Micro Moon
? A Micro Moon is the phenomenon where the moon is a “Full Moon” and is at its farthest point from earth during its yearly orbit, resulting in the appearance of a smaller and dimmer than normal moon (at least from our viewpoint). More specifically, a Micro Moon is the coincidence of a Full Moon or a New Moon with the farthest approach the Moon makes to the Earth on its elliptical orbit, resulting in the smallest apparent size of the lunar disk as seen from Earth. For comparison purposes NASA
, a Supermoon
is up to 14% larger and 30% brighter than a Micro Moon.
What is a Micro Moon, in more scientific terms?
Interestingly, the term Micro Moon is not used within the astrological community. The more scientific name for a Micro Moon is an Apogee Moon
. Apogee means the point at which the Moon is farthest in its orbit to the Earth. Even more technically, a Micro Moon is the apogee-syzygy of the Earth-Moon-Sun system. Syzygy is when the Earth, the Moon and the Sun are aligned, which happens at every Full Moon or New Moon. Got it? The result is that a Micro Moon can be regarded as the coincidence of the two, although they do not perfectly coincide each so. So, some Micro Moons are smaller than other Micro Moons.
Where did the name Micro Moons come from?
The term Micro Moon is not astronomical, but originated in modern astrology. Actually, we first have to start with the term “Supermoon,” which was invented by an astrologer named Richard Nolle in 1979. He arbitrarily defined the term Supermoon as follows:
…a new or full moon which occurs with the Moon at or near (within 90% of) its closest approach to Earth in a given orbit (perigee). In short, Earth, Moon and Sun are all in a line, with Moon in its nearest approach to Earth.
Once the term Supermoon was popularized, the community quickly adopted the term Micro Moon to describe Full Moons that smaller than normal Full Moons.
When do Micro Moons happen?
In case you are interested, the full moon cycle is the period between alignments of the lunar perigee with the sun and the earth, which is about about 411.8 days. With some simple math, we’ve calculated that approximately every 14th Full Moon will be a Micro Moon. However, there may be as many as three Micro Moons per full moon cycle since halfway through the cycle the Full Moon will be close to apogee, and the New Moons immediately before and after can be Micro Moons.
What qualifies as a Micro Moon?
There are no universal rules as to how far away the Moon must be to qualify as a Micro Moon. However, here are some general guidelines:
- If it is further away than 400,000 kilometers at apogee, it is listed as a Micro Moon.
- If a full moon is closer than 360,000 kilometers at perigee, it is considered a Supermoon.
Do Micro Moons affect the tides?
We are glad you asked. Since a Micro Moon is farther from Earth than a non-Micro Moon, the combined effect of the Sun and Moon on the Earth’s oceans (the “tide”) is at its weakest point. In general, the tide is greatest when the Moon is either a New Moon or a Full Moon, so a Micro Moon makes it just a little bit weaker. However, even at this powerful point, the force is still relatively weak, causing tidal differences of inches at most.
Do Micro Moons cause natural disasters?
We just learned about the somewhat minor effect a Micro Moon has on tides, but can a Micro Moon cause natural disasters? Well, the evidence is not convincing as no evidence has been found of any correlation between Micro Moons with major earthquakes. The theory is that the association of the Moon with both oceanic and crustal tides may lead to increased risk of events such as earthquakes and volcanic eruptions. This is an interesting topic, so we will see if our astronomers and scientists can find anything conclusive.
Best place to view a Micro Moon?
The best place to view a Micro Moon is a place with clear skies!
Are Micro Moon dangerous?
Although there is some superstition about Micro Moon and Full Moons in general, a Micro Moon isn’t likely to bring about the end of life as we know it. Although it could bring out the werewolf in you.
Popular Full Moon Calendars
Some popular full moon calendars, in addition to the 2025 Full Moon Calendar, include the following: Moon Calendar 2011,Moon Calendar 2012
, Moon Calendar 2013
, Moon Calendar 2014
, Moon Calendar 2015
, Moon Calendar 2016
, Moon Calendar 2017
, Moon Calendar 2018
, Moon Calendar 2019
, Moon Calendar 2020
, Moon Calendar 2021
, Moon Calendar 2022
, Moon Calendar 2020
, Moon Calendar 2023
, Moon Calendar 2024
, Moon Calendar 2025
You can also check out our Full Moon Calendar
, Lunar Calendar
, Lunar Eclipse Calendar
and Solar Eclipse Calendar
Full Moon Names History
2025 Full Moon Calendar
Full Moon names
have been used by many cultures to describe the full moon throughout the year. Specifically, Native American tribes used moon phases and cycles to keep track of the seasons by giving a distinctive name to each recurring full moon, including the Flower Moon
. The unique full moon names were used to identify the entire month during which each occurred.
Although many Native American tribes gave distinct names to the full moon, the most well known full moon names come from the Algonquin tribes who lived in the area of New England and westward to Lake Superior. The Algonquin tribes had perhaps the greatest effect on the early European settlers in America, and the settlers adopted the Native American habit of naming the full moons. | 0.80167 | 3.401958 |
Dione – Learn Fun Facts On Saturn’s Fourth Moon
Cratered & Cracked
Discovered in 1684 by Giovanni Cassini, Dione is the 15th largest moon in the solar system. It is composed primarily of water-ice and is very similar to its neighbouring moons Rhea and Tethys which also orbit close to Saturn. Dione completes an orbit of Saturn every 2.7 days, despite orbiting at about the same distance as Earth’s Moon does from Earth!
Fast Summary Facts About Dione!
- Discovered: March 21st 1684, by Giovanni Cassini
- Name: From Greek mythology, Dione is the mythical sister of Kronus (Saturn in Roman)
- Size: Diameter of 1,122 kilometres (697 miles)
- Moon Rank: 15th Largest in the solar system
- Orbit: Prograde and Circular
- Orbit Radius: 377,400 km from Saturn
- Orbital Period: 2 Days, 17 Hours, 41 Minutes
- Density: 1.478 g/cm3
- Surface Temperature: -186 °C (87 K)
- Surface: Water-ice
- Atmosphere: Tenuous (exosphere)
More Cool Fun Facts About Saturn’s 4th Major Moon!
- Despite the moon being discovered in 1684, and initially called Saturn IV (being the 4th moon from Saturn), it wasn’t until 1847 that its name was changed to Dione to avoid confusion after additional moons around Saturn were discovered.
- Dione was one of four to be discovered by Giovanni Cassini (along with Tethys, Rhea and Iapetus).
- Dione is similar to the moons Rhea and Tethys; they are all small, cold and airless bodies.
- Dione is the fourth moon from Saturn and orbits at about the same distance as Earth’s Moon, but because of Saturn’s larger mass (95 times bigger), Dione orbits ten times faster!
- Like many moons, Dione is ‘tidally locked’ to Saturn as it orbits; meaning the same face of Dione always faces Saturn. This is similar to Earth’s Moon!
- Dione also shares its orbit with two much smaller trojan moons that are gravitationally bound at Dione’s Lagrangian points; the trojan moon Helene is ahead (L4) and Polydeuces behind (L5).
- Dione is also in resonance with the two nearby inner moons, Mimas and Enceladus, helping to tidally heat Enceladus (and Dione) due to the 1:2 resonance.
- Dione’s density is 1.48 times that of liquid water which suggests Dione is 2/3rd water-ice and 1/3rd rocky material!
- Dione’s high water-ice content is evident from its high reflectivity (Albedo).
- According to data from the Cassini spacecraft, Dione has a global liquid water ocean ~65 km thick under an icy shell that is ~100 km thick; likely the result of tidal heating.
- Images from the Cassini spacecraft also reveal that the trailing hemisphere is darker in colour due to the natural darkening which occurs to water-ice over millions of years as radiation alters its surface. The lighter-coloured leading hemisphere is painted with young icy dust from Saturn's E-ring; formed from tiny particles ejected from Enceladus’ geysers!
- The Voyager spacecraft (1 & 2) observed Dione ‘up-close’ for the first time, revealing a surface with a varied cratering history as well as “wispy” lines which the later Cassini spacecraft, revealed to be bright fractures and ice cliffs several hundred meters high and that extend across Dione for hundreds of kilometres. Predominately on the trailing hemisphere. | 0.832943 | 3.52545 |
Bid to £475,000 in a London auction was a 1543 first of the work that cataloguer Barbara Scalvini had picked as one of three astronomical works being offered in King Street sales that had “caused the human race to rethink its place in the grand scheme of things”.
Copernicus’ De revolutionibus orbium coelestium was part of a wide-ranging July 10 auction held at Christie’s (25/20/13.5% buyer’s premium).
At the beginning of the 16th century the Earth was still believed to be the centre of the universe. However, in 1543, at the encouragement of mathematician and fellow astronomer Georg Joachim Rheticus – who three years earlier had been allowed to publish a summary of Copernicus’ heliocentric theories – the great work was printed in full in Nuremburg.
Fearing that he might fall foul of the church authorities, Andreas Osander (who had taken over editing and proof-reading responsibilities when Rheticus took up an academic post in Leipzig) added an address warning the reader that, in his view, it presented hypotheses that “need not be true or even possible…”
This infuriated Rheticus and presumably Copernicus as well, but the latter was by this time very ill and died shortly after.
The rare survivor offered in London this summer, which had been valued at £500,000-700,000, showed some repairs and was partially washed in a modern binding fashioned from old vellum.
Only a handful of copies have made more, the most expensive at $1.9m (then £974,360) being a copy in the 2008 Christie’s New York sale of Richard Green’s great scientific library. Largely untrimmed, unwashed and unpressed, it was in a simple period vellum binding.
The original manuscript survives to this day in the Jagellonian Library at Cracow University.
The previous day’s £2.59m Christie’s sale of scientific books from the collections of Peter and Margarethe Braune had also contained its share of astronomical rarities.
It was on a November night in 1572 that the great Danish astronomer Tycho Brahe realised that a bright new star had appeared in the night skies.
Nowadays it is identified as supernova SN 1572, thought to be some 7500 light years from Earth, but even then it was clear evidence that the long-held Aristotelian view of an unchanging celestial realm was wrong.
Brahe first published his findings in De nova… stella, a slim work of 1573 that is now of great rarity.
There was some waterstaining to the copy in the Braune sale, which also lacked a couple of preliminaries and was bound in 19th century boards with an incomplete 1577 work on a comet sighting by D Chytraeus, a Rostock theologian.
However, only two copies are recorded at auction since the 1930s, and that sold for £380 in 1978 as part of the great Honeyman scientic library had the last six leaves present in facsimile. The Braune copy sold well over estimate at £140,000.
It was in 1610 that Galileo published Sidereus Nuncius, a work in which he describes and illustrates what he had seen with the aid of the telescope of 30-times magnification he had constructed.
As well as confirming what Copernicus and Brahe had found, he could see that the moon was mountainous, the Milky Way was composed of numerous stars and four moons orbited Jupiter,
Nowhere in his book does Galileo explicitly endorse heliocentrism, but a few years later his books were banned by the Catholic church under a papal decree that declared such a view of the Earth’s motion to be false and contrary to scripture. On the same day that Galileo’s work was banned, so too was Copernicus’ De revolutionibus orbium coelestium.
In 1633 a second judgment of heresy was handed down and Galileo spent the rest of his life under house arrest. It was only in 1758, that the church finally dropped its prohibition against books promoting heliocentrism.
Also part of the Braune sale was a 1619, Frankfurt first of Johannes Kepler’s cosmological treatise, Harmonices mundi, a work which contains his third law of planetary motion. Sold at £80,000, this copy was bound with the Apologia, an appendix of 1620-21 containing his objections to the rival theories of Robert Fludd.
Other Braune successes included, at £26,000, an 1842, Prague offprint of Johann Christian Doppler’s first statement of a principle now known as the ‘Doppler Effect’. Now a fundamental tool of modern astronomy, it involves the increase or decrease in the frequency of sound, light, or other waves as the source and observer move towards or away from each other. | 0.945779 | 3.003537 |
Moon ♐ Sagittarius
Moon phase on 23 December 2087 Tuesday is Waning Crescent, 28 days old Moon is in Sagittarius.Share this page: twitter facebook linkedin
Previous main lunar phase is the Last Quarter before 6 days on 16 December 2087 at 20:11.
Moon rises after midnight to early morning and sets in the afternoon. It is visible in the early morning low to the east.
Moon is passing about ∠15° of ♐ Sagittarius tropical zodiac sector.
Lunar disc appears visually 9.7% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1770" and ∠1951".
Next Full Moon is the Wolf Moon of January 2088 after 15 days on 8 January 2088 at 09:37.
There is medium ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at very acute angle, so their combined tidal force is moderate.
The Moon is 28 days old. Earth's natural satellite is moving from the second to the final part of current synodic month. This is lunation 1087 of Meeus index or 2040 from Brown series.
Length of current 1087 lunation is 29 days, 19 hours and 19 minutes. This is the year's longest synodic month of 2087. It is 1 hour and 23 minutes longer than next lunation 1088 length.
Length of current synodic month is 6 hours and 35 minutes longer than the mean length of synodic month, but it is still 28 minutes shorter, compared to 21st century longest.
This lunation true anomaly is ∠183°. At the beginning of next synodic month true anomaly will be ∠208.8°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
1 day after point of apogee on 22 December 2087 at 02:07 in ♏ Scorpio. The lunar orbit is getting closer, while the Moon is moving inward the Earth. It will keep this direction for the next 14 days, until it get to the point of next perigee on 6 January 2088 at 19:17 in ♊ Gemini.
Moon is 404 998 km (251 654 mi) away from Earth on this date. Moon moves closer next 14 days until perigee, when Earth-Moon distance will reach 360 758 km (224 165 mi).
2 days after its ascending node on 21 December 2087 at 00:25 in ♏ Scorpio, the Moon is following the northern part of its orbit for the next 11 days, until it will cross the ecliptic from North to South in descending node on 4 January 2088 at 02:18 in ♉ Taurus.
2 days after beginning of current draconic month in ♏ Scorpio, the Moon is moving from the beginning to the first part of it.
At 22:55 on this date the Moon is meeting its South standstill point, when it will reach southern declination of ∠-20.078°. Next 14 days the lunar orbit will move in opposite northward direction to face North declination of ∠20.031° in its northern standstill point on 6 January 2088 at 13:10 in ♊ Gemini.
After 1 day on 25 December 2087 at 01:42 in ♑ Capricorn, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.062006 |
Photographs STAR Moving 4800 MILES A SECOND (May, 1930)
This article is interesting for a number of reasons. One of the most interesting is that M.L Humasen was a high-school dropout who got a job as a janitor at Mt. Wilson Observatory where the was later made a member of the astronomical staff . He went on to take many of the observation that Edwin Hubble used to formulate Hubble’s Law. It’s odd that in the interview Humasen says he doesn’t believe the universe is “blowing up” which is precisely what Hubble’s Law says, though a bit less dramatically.
I’m a little confused about calling the object a star. N.G.C 4800 is actually a galaxy. Hubble was the one who proved, in the early 1920’s that these distant objects were outside the Milky Way and were in fact galaxies. Since they also refer to it as a nebula (which was sort of a catch-all term for blurry stellar objects at the time) I’m going to guess that it was just the reporter who decided it was a star.
I don’t know enough about solar spectra to be sure, but it seems like you wouldn’t be able to make a direct comparison of the spectra from a whole galaxy to that of one star. Incidentally N.G.C 4800 is actually 97.14 million light years away not the 50 million the article states.
Photographs STAR Moving 4800 MILES A SECOND
Sitting with his eye glued to a telescopic camera for 45 hours, M. L. Humason, Mt. Wilson astronomer, has succeeded in setting a record for long distance photographs. The nebula on which he trained his camera is 50,000,000 light years away from the earth.
FOR 45 hours in total darkness, Milton L. Humason, member of the astronomical staff at the Mt. Wilson observatory at Pasadena, California, trained the world’s largest telescope toward a far distant point in the heavens and obtained a photograph of a nebula 50,000,000 light years away from the earth—a total of 300 quintillion miles.
While the actual picture of the nebula shows it to be only a pin point among other and less distant stars, what Mr. Humason actually pictured was one of the brightest nebulae in the heavens.
Due to the distance, the amount of light which reached his photographic plate from this nebula is so faint that ordinary telescopes cannot photograph its spectrum. Even the 100-inch telescope had to be held on it all night every night for a week before the inflowing waves of light could be gathered together in the world’s largest reflector and funnelled into an image strong enough to record the spectrum on a photographic plate.
While the nebula has no name, it is known as N. G. C. 4860, which merely means that it is number 4860 in the Mt. Wilson new general catalogue.
Mr. Humason worked in total darkness, because light from any other source than the object would have spoiled the picture. He pointed the telescope toward the object and a driving clock held it in the proper position despite the earth’s rotation. Without the driving clock the telescope would have moved with Mt. Wilson out of alignment.
While the driving clock is as accurate as clock works can be made, Mr. Humason kept his eyes constantly on the slit through which the focused light passes to the prisms and the camera, and corrected any wanderings of the image.
“The light entered the barrel of the telescope striking the 100-inch reflector at the lower end and was reflected back to a smaller mirror at the top,” Mr. Humason explains.
“This reflected the light down the tube again, bringing it to a focus at a slit under the eyes of the observer. Passing through the slit the focused light would strike a series of prisms which broke it into colors, and that is the spectrum I photographed. Falling for a long time on a sensitive photographic plate, even this very faint light finally made an impression.”
The spectrum of the nebulae, when compared with the spectrum of the sun, revealed that the object is moving away from the earth at a speed of 4800 miles a second.
“Interpreting this in the established way,” says Mr. Humason, “it would look as if the whole universe were exploding, scattering into space, entire nebulae flying away faster than shells from a cannon, but I don’t believe the universe is blowing up.”
While photographing this rapidly receding nebulae, Mr. Humason had to control the focus and the comparison spectrum, keep the temperature of the spectrograph exactly right throughout the night. Sitting in total darkness with his eyes on a slit of dim light little larger than a pin head, he worked levers and pushed buttons for seven nights without moving the photographic plate or losing sight of the faintly luminous spot in the sky. Here Mr. Humason brought romance of the heavens down to earth.
Mr. Humason and his fellow astronomers have been unable to determine whether the huge velocity—4800 miles a second —is real, or whether the indication comes from a slowing down of the light waves due to distortion in space, or to forces acting on the waves during their long journey to earth.
By the taking of this long distance photograph and other experiments at Mt. Wilson, the astronomers are attempting to test Einstein’s contention that the entire universe of space and time are curved. They are attempting to test it not mathematically, but by actual observation.
Mr. Humason’s long distance photograph goes to the very heart of the problem. The light by which the photograph was taken comes from the remotest region of the universe. It is not local light, not light radiated from within our own galaxy. It originates far outside. | 0.879357 | 3.345872 |
An all-sky cosmic-ray proton anisotropy search with Fermi-LAT
Cosmic rays observed at Earth do not point back to their sources due to deflection in interstellar magnetic fields. So, despite over a century of research, direct evidence for the sources of cosmic rays remains elusive. By the time they are observed at Earth’s surface, cosmic rays are highly isotropic, i.e., uniform from all directions. Cosmic-ray anisotropy is any non-uniformity in their arrival directions—it can be thought of as excesses or deficits in the cosmic-ray flux from particular directions. It is important because it tells us about the distribution of sources of cosmic rays and even probes the structure of the local interstellar magnetic field.
Ground-based experiments have made precision measurements of cosmic-ray anisotropy, but each observatory on Earth sees only part of the sky. Furthermore, they use analysis techniques that do not allow all of the information about the anisotropy to be recovered. Specifically, the variation of the anisotropy along the direction of Earth’s rotation axis—called declination—has never been measured below the 1018 eV energy scale.
That’s where the space-based Fermi Large Area Telescope (LAT) can help. While it is primarily a gamma-ray telescope, most of the particles that Fermi-LAT records are cosmic rays. Being in space, it does not have the same limitations that afflict ground-based telescopes, allowing it to shed new light on the cosmic-ray anisotropy mystery.
Collaborators from this project realized that the abundance of cosmic-ray protons in the LAT data set might enable them to measure cosmic-ray anisotropy, and so they conducted the first search for cosmic-ray proton anisotropy using Fermi-LAT data. They present their results in a paper published last week in The Astrophysical Journal.
Standard diffusion theory, which describes how cosmic rays travel through space, predicts that there should be a large-scale anisotropy in cosmic-ray arrival directions. This anisotropy has been consistently observed, though the size of the effect is at least an order of magnitude smaller than that predicted by standard diffusion theory. There is evidence that this discrepancy, along with the observed direction of the anisotropy, is the result of a confluence of effects: the distribution of local sources of cosmic rays, the local interstellar magnetic field, and systematic effects in the observations from ground-based observatories.
WIPAC researcher Justin Vandenbroucke realized the Fermi-LAT’s potential for measuring cosmic-ray proton anisotropy. “Fermi has proven to be an incredibly flexible instrument, making breakthrough measurements of not only cosmic gamma rays, but also of cosmic electrons, positrons, and now protons.”
To conduct the search, the researchers first came up with a data selection algorithm to gather a large sample of cosmic-ray protons for the analysis—the larger, the better. However, since the LAT is optimized for gamma-ray analyses, they had to take extra care to understand the data and any effects introduced by the algorithms that reconstruct physical quantities, such as energy and direction, under the assumption that the particles are gamma rays
Because the anisotropy in cosmic-ray arrival directions is very small, researchers used a data-driven approach to measure it and created a “reference map,” or their best guess of what the sky would look like if it were isotropic, i.e., the same from all directions. They then compared the observed sky map to the reference map to search for deviations larger than the expected statistical fluctuations, which might be evidence of anisotropy.
“Since we know that cosmic-ray anisotropy is very small, the trickiest part of the analysis was to ensure that we understood the data set and reference map algorithm very well,” says Matthew Meehan, a recent WIPAC PhD graduate who, with Vandenbroucke, led the analysis and paper. Any uncertainties or irregularities in the reference map had to be smaller than 0.1 percent. The researchers also had to study systematic effects that could mimic an anisotropy, such as geomagnetic effects, and make sure those were understood to be less than 0.1 percent.
The researchers found that the cosmic-ray sky at 100 GeV is consistent with isotropy. While the analysis did reveal a slight excess (with statistical significance approximately 2.5 sigma), it may be due to statistical fluctuations. Because of this, they set upper limits on the strength of the anisotropy of cosmic-ray protons at these energies. The upper limits on the declination component of the anisotropy are the most constraining of any analysis by any instrument, for any energy range. “This is new constraining information about cosmic-ray anisotropy that hasn’t been measured before,” says Meehan.
Improving these limits would likely require years for another space-based observatory to acquire significantly more cosmic rays. In the immediate future, scientists can incorporate the information from these results about the full shape of the anisotropy to constrain the direction of the local interstellar magnetic field and its influence on cosmic rays.
“These results from the Fermi-LAT collaboration provide a new complement to ground-based measurements,” says Vandenbroucke, “not only by extending to a lower energy range, but by covering the full sky, constraining the declination component, and by applying purely to cosmic-ray protons without ambiguity as to which cosmic-ray nuclei are involved.”
+ info “A Search for Cosmic-ray Proton Anisotropy with the Fermi Large Area Telescope,” The Fermi-LAT Collaboration: M. Ajello et al. Published in The Astophysical Journal. | 0.812933 | 4.135496 |
Using the European Space Agency’s Integral and XMM-Newton observatories, an international team of astronomers has found more evidence that massive black holes are surrounded by a doughnut-shaped gas cloud, called a torus. Depending on our line of sight, the torus can block the view of the black hole in the centre. The team looked ‘edge on’ into this doughnut to see features never before revealed in such a clarity.
From European Space Agency:
ESA’s high-energy observatories spot doughnut-shaped cloud with a black-hole filling
Using ESA’s Integral and XMM-Newton observatories, an international team of astronomers has found more evidence that massive black holes are surrounded by a doughnut-shaped gas cloud, called a torus. Depending on our line of sight, the torus can block the view of the black hole in the centre. The team looked `edge on’ into this doughnut to see features never before revealed in such a clarity.
Black holes are objects so compact and with gravity so strong that not even light can escape from them. Scientists think that `supermassive’ black holes are located in the cores of most galaxies, including our Milky Way galaxy. They can contain the mass of thousands of millions of suns, confined within a region no larger than our Solar System. They appear to be surrounded by a hot, thin disk of accreting gas and, farther out, the thick doughnut-shaped torus.
Depending on the inclination of the torus, it can hide the black hole and the hot accretion disc from the line of sight. Galaxies in which a torus blocks the light from the central accretion disc are called `Seyfert 2′ types and are usually faint to optical telescopes. Another theory, however, is that these galaxies appear rather faint because the central black hole is not actively accreting gas and the disc surrounding it is therefore faint.
An international team of astronomers led by Dr Volker Beckmann, Goddard Space Flight Center (Greenbelt, USA) has studied one of the nearest objects of this type, a spiral galaxy called NGC 4388, located 65 million light years away in the constellation Virgo. Since NGC 4388 is relatively close, and therefore unusually bright for its class, it is easier to study.
Astronomers often study black holes that are aligned face-on, thus avoiding the enshrouding torus. However, Beckmann’s group took the path less trodden and studied the central black hole by peering through the torus. With XMM-Newton and Integral, they could detect some of the X-rays and gamma rays, emitted by the accretion disc, which partially penetrate the torus. ”By peering right into the torus, we see the black hole phenomenon in a whole new light, or lack of light, as the case may be here,” Beckmann said.
Beckmann’s group saw how different processes around a black hole produce light at different wavelengths. For example, some of the gamma rays produced close to the black hole get absorbed by iron atoms in the torus and are re-emitted at a lower energy. This in fact is how the scientists knew they were seeing `reprocessed’ light farther out. Also, because of the line of sight towards NGC 4388, they knew this iron was from a torus on the same plane as the accretion disk, and not from gas clouds `above’ or `below’ the accretion disk.
This new view through the haze has provided valuable insight into the relationship between the black hole, its accretion disc and the doughnut, and supports the torus model in several ways.
Gas in the accretion disc close to the black hole reaches high speeds and temperatures (over 100 million degrees, hotter than the Sun) as it races toward the void. The gas radiates predominantly at high energies, in the X-ray wavelengths.
According to Beckmann, this light is able to escape the black hole because it is still outside of its border, but ultimately collides with matter in the torus. Some of it is absorbed; some of it is reflected at different wavelengths, like sunlight penetrating a cloud; and the very energetic gamma rays pierce through. ”This torus is not as dense as a real doughnut or a true German Krapfen, but it is far hotter – up to a thousand degrees – and loaded with many more calories,” Beckmann said.
The new observations also pinpoint the origin of the high-energy emission from NGC 4388. While the lower-energy X-rays seen by XMM-Newton appear to come from a diffuse emission, far away from the black hole, the higher-energy X-rays detected by Integral are directly related to the black hole activity.
The team could infer the doughnut’s structure and its distance from the black hole by virtue of light that was either reflected or completely absorbed. The torus itself appears to be several hundred light years from the black hole, although the observation could not gauge its diameter, from inside to outside.
The result marks the clearest observation of an obscured black hole in X-ray and gamma-ray `colours’, a span of energy nearly a million times wider than the window of visible light, from red to violet. Multi-wavelength studies are increasingly important to understanding black holes, as already demonstrated earlier this year. In May 2004, the European project known as the Astrophysical Virtual Observatory, in which ESA plays a major role, found 30 supermassive black holes that had previously escaped detection behind masking dust clouds.
Note for editors
This result will appear on The Astrophysical Journal. Besides Volker Beckmann, the author list includes Neil Gehrels, Pascal Favre, Roland Walter, Thierry Courvoisier, Pierre-Olivier Petrucci and Julien Malzac.
For more information about the Astrophysical Virtual Observatory programme and how it has allowed European scientists to discover a number of previously hidden black holes, see:
More about Integral
The International Gamma Ray Astrophysics Laboratory (Integral) is the first space observatory that can simultaneously observe celestial objects in gamma rays, X-rays and visible light. Integral was launched on a Russian Proton rocket on 17 October 2002 into a highly elliptical orbit around Earth. Its principal targets include regions of the galaxy where chemical elements are being produced and compact objects, such as black holes.
More information on Integral can be found at:
More about XMM-Newton
XMM-Newton can detect more X-ray sources than any previous observatory and is helping to solve many cosmic mysteries of the violent Universe, from black holes to the formation of galaxies.
It was launched on 10 December 1999, using an Ariane-5 rocket from French Guiana. It is expected to return data for a decade. XMM-Newton’s high-tech design uses over 170 wafer-thin cylindrical mirrors spread over three telescopes.
Its orbit takes it almost a third of the way to the Moon, so that astronomers can enjoy long, uninterrupted views of celestial objects.
More information on XMM-Newton can be found at: | 0.900332 | 3.995781 |
Science, Tech, Math › Science What Are Comets? Origins and Scientific Findings Share Flipboard Email Print Comet P1/McNaught, taken from Siding Spring, Australia in 2007. SOERFM/Wikimedia Commons CC BY-SA 3.0 Science Astronomy Solar System An Introduction to Astronomy Important Astronomers Stars, Planets, and Galaxies Space Exploration Chemistry Biology Physics Geology Weather & Climate By John P. Millis, Ph.D Professor of Physics and Astronomy Ph.D., Physics and Astronomy, Purdue University B.S., Physics, Purdue University John P. Millis, Ph.D. is a professor of physics and astronomy at Anderson University. He conducts research at the VERITAS gamma-ray observatory in southern Arizona. our editorial process John P. Millis, Ph.D Updated November 16, 2018 Comets are the great mystery items of the solar system. For centuries, people saw them as evil omens, appearing and disappearing. They looked ghostly, even frightening. But, as scientific learning took over from superstition and fear, people learned what comets really are: chunks of ice and dust and rocks. Some never get close to the Sun, but others do, and those are the ones we see in the night sky. Solar heating and the action of the solar wind change the appearance of a comet drastically, which is why they are so fascinating to observe. However, planetary scientists also treasure comets because they represent a fascinating part of our solar system's origin and evolution. They date back to the earliest epochs the history of the Sun and planets and thus contain some of the oldest materials in the solar system. Comets in History and Exploration Historically, comets have been referred to as "dirty snowballs" since they are large chunks of ice mixed with dust and rock particles. Interestingly, it has only been in the past hundred years or so that the idea of comets as icy bodies was ultimately proved to be true. In more recent times, astronomers have viewed comets from Earth, as well as from spacecraft. Several years ago, a mission called Rosetta actually orbited the comet 67P/Churyumov-Gerasimenko and landed a probe on its icy surface. The Origins of Comets Comets come from distant reaches of the solar system, originating in places called Kuiper belt (which extends out from the orbit of Neptune, and the Oört cloud which forms the outermost part of the solar system. Comet orbits are highly elliptical, with one focus at the Sun and the other end at a point sometimes well beyond the orbit of Uranus or Neptune. Occasionally a comet's orbit will take it directly on a collision course with one of the other bodies in our solar system, including the Sun. The gravitational pull of various planets and the Sun also shape their orbits, making such collisions more likely as the comet makes more trips around the Sun. The Comet Nucleus The primary part of a comet is known as the nucleus. It's a mixture of mostly ice, bits of rock, dust and other frozen gases. The ices are usually water and frozen carbon dioxide (dry ice). The nucleus is very hard to make out when the comet is closest to the Sun because it's surrounded by a cloud of ice and dust particles called the coma. In deep space, the "naked" nucleus reflects only a small percentage of the Sun's radiation, making it almost invisible to detectors. Typical comet nuclei vary in size from about 100 meters to more than 50 kilometers (31 miles) across. There's some evidence that comets may have delivered water to Earth and other planets early in the solar system's history. The Rosetta mission measured the type of water found on Comet 67/Churyumov-Gerasimenko, and found that its water was not quite the same as Earth's. However, more study of other comets is needed to prove or disprove just how much water comets may have made available to the planets. The Comet Coma and Tail As comets approach the Sun, radiation begins to vaporize their frozen gases and ice, creating a cloudy glow around the object. Known formally as the coma, this cloud can extend many thousands of kilometers across. When we observe comets from Earth, the coma is often what we see as the "head" of the comet. The other distinctive part of a comet is the tail area. Radiation pressure from the Sun pushes material away from the comet, forming two tails. The first tail is the dust tail, while the second is the plasma tail — made up of gas that has been evaporated from the nucleus and energized by interactions with the solar wind. Dust from the tail gets left behind like a stream of bread crumbs, showing the path the comet has traveled through the solar system. The gas tail is very tough to see with the naked eye, but a photograph of it shows it glowing in a brilliant blue. It points directly away from the Sun and is influenced by the solar wind. It often extends over a distance equal to that of the Sun to the Earth. Short-Period Comets and the Kuiper Belt There are generally two types of comets. Their types tell us their origin in the solar system. The first are comets that have short periods. They orbit the Sun every 200 years or less. Many comets of this type originated in the Kuiper Belt. Long-period Comets and the Oort Cloud Some comets take more than 200 years to orbit the Sun once. Others can take thousands or even millions of years. The ones with the long periods come from the Oort cloud. It extends more than 75,000 astronomical units away from the Sun and contains millions of comets. (The term "astronomical unit" is a measurement, equivalent to the distance between Earth and the Sun.) Sometimes a long-period comet will come in toward the Sun and veer off into space, never to be seen again. Others get captured into a regular orbit that brings them back again and again. Comets and Meteor Showers Some comets will cross the orbit that the Earth takes around the Sun. When this happens a trail of dust is left behind. As Earth traverses this dust trail, the tiny particles enter our atmosphere. They quickly begin to glow as they are heated up during the fall to Earth and create a streak of light across the sky. When a large number of particles from a comet stream encounters Earth, we experience a meteor shower. Since the comet tails are left behind in specific locations along Earth's path, meteor showers can be predicted with great accuracy. Key Takeaways Comets are chunks of ice, dust, and rock that originate in the outer solar system. Some orbit the Sun, others never get closer than the orbit of Jupiter.The Rosetta Mission visited a comet called 67P/Churyumov-Gerasimenko. It confirmed the existence of water and other ices on the comet.A comet's orbit is called its 'period'. Comets are observable by both amateur and professional astronomers. | 0.910957 | 3.857007 |
I was quoted in the newspaper today. One problem with talking to journalists, is that you don’t always know quite how they’re going to represent what you said, or – even – if you’re going to end up having said something silly; you don’t get much warning and you, typically, don’t get a chance to proof read what they end up writing. This article, however, seems fine; I’m not sure if I actually said what I’m quoted as saying, but it seems pretty close to something I would have said.
The article itself is about the recent announcement, by NASA, of 1284 new exoplanets. Just in case anyone doesn’t know, an exoplanet is a planet in orbit around a star other than the Sun. These new exoplanets were discovered by NASA’s Kepler satellite, which uses the transit method. The transit method basically works by staring at as many stars as possible (150000 in the case of the Kepler satellite) and trying to find those that show periodic dips in brightness. This would indicate something passing in front of the star. The relative dip in brightness can then be used to infer the radius of this object, and the period can be used to infer its distance from the star.
One problem with this method is that there can be lots of false positives; there are many things that aren’t planets that can cause what appear to be periodic dips in a star’s brightness. However, the Kepler data is so exquisite that they can rule out many of these false positives. That’s what’s happened here. These new exoplanets were amongst many candidate exoplanets detected a few years ago. The analysis now indicates that these 1284 candidates are almost certainly exoplanets, and hence have been announced as such.
This gives me an opportunity to discuss some of my own research. As the article says, I’m part of the HARPS-N consortium. Although the transit method has been extremely successful, it essentially only allows one to determine the radius of the planet and its distance from the star. If there are multiple planets, one can sometimes infer the planet masses from the timing of the transits, but this doesn’t work for all systems. However, in a planetary system, the star and planets all orbit the common centre of mass. This means that at some times the star will be coming towards us, and at other times away.HARPS-N is a high-resolution spectrograph, part built in Edinburgh and located on the 3.6m Telescopio Nazionale Galileo. What it does is measure small shifts in the star’s spectrum which can then be used – via the Doppler effect – to determine the star’s radial (line-of-sight) velocity:
where is the rest-frame wavelength of a specific spectral line, is the shift in this wavelength, is the radial velocity of the star, and is the speed of light. From these small shifts in the spectral lines, you can determine the radial velocity of the star. If the radial velocity of the star shows periodic features, then one can infer that it must have companions (planets) and one can use this to infer the mass of these companions, their distance from their host star, and the eccentricity (or the circularity) of their orbits.The figure on the left shows the radial velocity curves for 3 rocky planets in a 4 planet system that we discovered last year. I should be clear that the radial velocity is that of the star, and each radial velocity curve has removed the contribution due to all the other planets in the system. The top two curves are quite sinusoidal and indicate that these two planets are on roughly circular orbits. The asymmetry in the bottom curve indicates that this planet’s orbit is somewhat eccentric.
Okay, this post is getting rather long, but we’re getting to the point I was wanting to highlight. If you look at the figure on the left, you’ll note that the radial velocity amplitudes are a few m/s. The spectral resolution of HARPS-N is . This is the inverse of the smallest relative wavelength change that can be measured by the instrument
If you look at the formula for the Doppler shift that I included above, you can relate this to the spectral resolution through
If HARPS-N has and , then . Hmmmm, if this is the smallest radial velocity that we can measure, how can we have measured radial velocities of only a few m/s? The reason is that we measure across a wavelength range (383nm – 690nm) where there are lots and lots and lots of spectral lines, and then we cross-correlate with the known spectrum of the type of star we’re observing. The peak in the cross correlation function then gives the wavelength shift, from which we can determine the radial velocity of the star. You then need to repeat this a number of times (maybe 30 to 60) over the course of a year or so, to then produce the radial velocity curve from which you can determine if there is a companion planet, and – if there is – the properties of that planet.
So, even though we can’t directly determine the shift in individual lines, we can still determine the wavelength shift and – hence – the radial velocity of the host star. Given that we can’t actually see the shifts directly, how can we be confident that what we’ve measured really is indicative of a companion planet? One way is that different teams observe the same system and get the same result. Another is that some of the systems we observe are Kepler targets that are already known to probably host planets. The radial velocity results for those systems are consistent with what is already known from the transit measurements. Finally, and this applies to the 4-planet system I mentioned earlier; some of those detected via the radial velocity measurement are then found to also transit their host stars. Again, the results are consistent.Maybe I’ll finish by pointing out another reason why combining radial velocity and transit measurements can be so powerful. The radial velocity measurements give the mass of the planet, while the transit meaurement gives its radius. Together they give the density, from which one can infer the internal compostion. The figure on the right shows the mass-radius relation for a number of known exoplanets, including Kepler-78b (K78b) which our team characterised a few years ago and is still the most similar – in composition and size – to the Earth, and HD219134b, one of those shown in the radial velocity figure above.
What’s clear is that there are a number of known exoplanets with compositions that appear very similar to the Earth. However, to date, these are all planets that are very close to their parent stars and, therefore, are almost certainly far too hot to host life. To date, we do not know of any genuine Earth-like exoplanets, in terms of composition, size, and distance from a star similar to the Sun. This is one reason why I think we have to be careful when talking to journalists about this topic. It’s easy to make them think that we’ve found something Earth-like and, hence, habitable, when really it is simply a rocky planet with a composition similar to that of the Earth, but almost certainly too hot to harbour life. For the moment, I would be very cautious about accepting any claims of having found a habitable, or even potentially habitable, planet. In 10-20 years time, though……. | 0.855497 | 3.258358 |
Secondary muons are generated in interactions of primary cosmic rays (CR) with nuclei of atoms of the atmosphere and keep quite well the directions of parent particles. Therefore, variations of primary CR caused by various phenomena associated with solar activity may be studied on the basis of the analysis of variations of the angular distribution of the muon flux measured in a real- time mode. This approach is the basis of the method of muon diagnostics developed in the Moscow Engineering Physics Institute using a specially designed muon hodoscope URAGAN (Shutenko et al. 2009; Astapov et al. 2013). Objects of the muon diagnostics are processes in the heliosphere of solar origin, which may cause negative influence on the vital activity of people (transpolar flights, orbital and interplanetary missions, and others). For implementation of the muon diagnostics method, large-area tracking detectors are needed to provide a necessary statistical accuracy for each angular direction within the device aperture. The registration system should not only provide localization of the anomaly but also trace its further propagation. This imposes quite high requirements to the system of primary analysis, formation and presentation of the obtained physical information in real time.
The main advantage of wide-aperture muon hodoscopes compared to multidirectional muon telescopes is the possibility of reconstruction in real time of the track of each muon arriving from any direction of the upper hemisphere. To provide acceptable flows of processed and accumulated information, a matrix method of representing experimental data has been applied, which is described below.
Muon hodoscope (MH) URAGAN (Chernov et al. 2005; Barbashina et al. 2008), a wide-aperture coordinate-tracking detector which detects in a real-time mode the muon flux at the Earth’s surface in a wide range of zenith angles (0–80°) with a high angular resolution (~1°), was constructed in the Scientific and Educational Centre NEVOD, MEPhI. The main objective of the facility is the study of variations of the angular distribution of the muon flux caused by various atmospheric and extra-atmospheric processes. The URAGAN consists of four independent supermodules. Each supermodule (SM) (Figure 1) represents an assembly of eight planes of streamer tube chambers blown with a gas mixture Ar + CO2 + n-pentane. Sixteen gas discharge tubes with size 9 × 9 × 3500 mm3 and resistive cathode coating operated in a limited streamer mode are enclosed in a single plastic container. Each plane contains 320 tubes equipped with an external X-Y-strips coordinate readout system. Sensitive area of one SM is ~11.5 m2. Trigger condition of the event detection is the coincidence of signals from the strips of 4 or more X-strip planes within the time gate of 250 ns. The scheme of the muon detection in the SM is shown in Figure 2.
As described in the article (Yashin et al. 2015a), the track parameters (two projection angles) are reconstructed in a real-time mode by means of the software which is based on the histogramming technique in each projection plane XZ and YZ and are stored in a two-dimensional data matrix over one-minute time interval. This data array is a “muon snapshot” of the upper hemisphere (limited by the detector aperture) acquired with a one-minute exposure. The monitoring data include results of testing of serial data readout circuits, measurements of the SM plane noise rate, hit channel maps and estimates of the efficiency of particle track detection by the planes.
The angular distribution of the tracks for 1 minute measurement interval is stored in the forms of three types of matrices with dimensions of 90 × 90 cells: zenith and azimuth angles (θ, φ) Ma ≡ [θi, φj]; in projection angles (θX, θY), Mpa ≡ [θXi, θYj]; in tangents of projection angles (tgθX, tgθY); Mtg ≡ [tgθXi, tgθYj]. Different types of matrices are used for solution of different tasks. The matrix Ma is used to study angular characteristics of the muon flux (for example, the anisotropy and energy dependences of the muon flux during Forbush decreases). The Mtg matrix is used to construct images-muonographs (Yashin et al. 2015a) (projection on the muon generation layer in the atmosphere to study thunderstorm events or projection on a magnetopause to study geoeffective events during the disturbances on the Sun). The Mpa matrix is used to more accurately study the effects in the directions close to the vertical (for example, Ground Level Enhancement (GLE) analysis).
Every matrix contains the angular distribution of muons measured during 1-minute interval. The sequence of such matrices gives a unique possibility to study the temporal changes of muon angular distributions. Depending on the analysis to be performed, matrices can be combined in different time intervals Δt. For example, for the analysis of muon flux variations of heliospheric origin, the matrix data summed during Δt = 1 h may be used. For the study the dynamics of rapidly developing atmospheric processes that cause variations in the intensity of muons, five-minute matrices are analyzed.
Data processing is carried out in a real-time mode. Time series of averaged over 1- and 60-min intervals atmospheric pressure, counting rates of reconstructed tracks (without the barometric and temperature corrections), and “live”-times for every supermodule are formed. These series are stored in 1- and 60-min daily files in a text format. At the beginning of each hour, an additional processing is carried out, for which the data of three SM (SM1, SM3 and SM4) are used, while SM2 is used mainly for methodical and calibration purposes. The purpose of data processing procedures is the creation of time series of the angular distribution of muons and of parameters of the counting rate analysis. Results of additional processing are:
Images of time series graphs and of matrices of variations of the angular distribution are presented at the web pages (Yashin et al. 2015b):
Changes of the atmospheric conditions modulate the muon flux at the Earth’s surface, and variations of the extra-atmospheric origin are of the same order. Therefore, to study the extra-terrestrial effects it is necessary first to correct all the matrices for the main atmospheric effects, barometric and temperature ones.
Barometric effect is the anti-correlation of cosmic ray intensity with the pressure at the observation level. Temperature effect is caused by changes of the temperature at all altitudes of the atmosphere. Corrected angular matrix Mcorr(θ,φ,t,Δt) can be calculated in a following way:
where θ and φ are zenith and azimuth angles for matrix cell centers; M(θ,φ) is the number of reconstructed events in a cell (θ,φ) of the matrix M; t is the time of the beginning and Δt is the time interval of the matrix accumulation; ΔMT and ΔMP are corrections for temperature and barometric effects. Barometric correction is calculated as
where P is the current pressure at registration level, P0 = 993 mbar is the averaged over a long time period pressure at the registration level, B(θ) are barometric coefficients. Temperature correction is
where M0(θ) is the over a long period averaged number of reconstructed events for zenith angle θ, WT(h, θ) are differential in altitude temperature coefficients (DTC) (Dmitrieva et al. 2011), ΔT(h)=TSMA(h)–T(h) is the change of the temperature, h is the atmospheric depth, Δh = 0.05 atm, T(h) is the current temperature profile of the atmosphere, TSMA(h) is the temperature profile for the standard model of the atmosphere. In calculations, a six-layer stationary spherical model of the atmosphere is used, contributions of both pions and kaons are taken into account. Also for muons, the relation between specific energy loss and muon energy. The altitude above sea level and threshold energies of the muon hodoscope URAGAN have been taken into account.
Information about the temperature profile of the atmosphere can be obtained from the following sources (Dmitrieva et al. 2015):
In Figure 3, 10-minute average counting rates of the URAGAN hodoscope without and with corrections for meteorological effects are shown for a one year period. Barometric coefficients for URAGAN slightly depend on the zenith angle and are about ~0.18%/mbar. After correction for barometric effect, annual variations caused by the temperature effect (~8%) become well visible. After correction for the temperature effect, variations caused by extra-atmospheric processes appear.
For the study of the response of muon flux variations registered by the muon hodoscope URAGAN, the local anisotropy vector A, one of the main characteristics of the angular distribution of muon flux, which is the sum of unit vectors with directions of reconstructed tracks in individual events normalized to the total number of muons was used. The local anisotropy vector A indicates the average arrival direction of muons and is close to the vertical. For the study of its deviations from the average direction, a relative anisotropy vector that is the difference between the current value of the vector and the average anisotropy vector calculated over a long period of time is used: r = A–<A>. The length of the horizontal projection of the relative anisotropy vector characterizes the “side influence” on the angular distribution of the muon flux and is given by:. For the convenience of comparison of different events, its value is expressed in units of the RMS deviation (σ).
The rh parameter is sensitive to the changes in the interplanetary magnetic field induced by the active processes on the Sun. The variations of the horizontal projection of the vector of local anisotropy can be used to identify the time intervals of the increased anisotropy, which are observed during the passage of various irregularities in the solar wind and the interplanetary magnetic field in the Earth’s vicinity. Study of the muon flux anisotropy during periods of heliospheric disturbances is based on the comparison of data of satellite detectors and muon hodoscope URAGAN. To estimate the state of the interplanetary space, the values of the modulus of the magnetic induction vector B and the solar wind velocity Vsw were used in the work. To estimate the state of the magnetosphere, the values of the geomagnetic activity index Kp were used (OMNI Database https://omniweb.gsfc.nasa.gov/). Figure 4 shows changes in the parameters B, Vsw, Kp-index, counting rate N (normalized to one SM) and the parameter of the local anisotropy according to URAGAN for the period from September 9 to October 10, 2016 (Astapov et al. 2015).
The horizontal lines in the graphs indicate the boundaries for the determination of perturbations in the interplanetary space (B, Vsw), the Earth’s magnetosphere (Kp) and the cosmic-ray muon flux (). The vertical line marks the coronal mass ejection (CME) recorded by the coronagraph from the STEREO satellite on September 15, 2016 at 00:23 UT with an average speed of 625 km/s.
As can be seen from the upper graphs, the ejection affected the interplanetary magnetic field. The increase in the values of magnetic induction began on September 18, the maximum was reached on September 19 and amounted to 18.9 nT. There was also a disturbance in the values of the solar wind speed, its maximum occurred on September 20 and amounted to 727 km/s. The perturbations of these parameters in the interplanetary space were confirmed by the geomagnetic activity index Kp = 4.
The response of the muon hodoscope to the CME was visible one day after ejection. Three distinct peaks were repeated at regular intervals once per day and are clearly seen on the last graph. The projection of the relative anisotropy vector rh inunits reached a maximum value on September 16 at 01:00, = 6.4. The second peak was observed on September 17 at 03:00 and amounted to = 5.8, which in both cases corresponded to a perturbation of the local anisotropy of the muon flux.
Muon hodoscope is a cosmic-ray detector designed to study the relations between the spatial and temporal variations of the cosmic ray muon flux and various dynamic processes in the heliosphere and magnetosphere of the Earth. Development of the URAGAN hodoscope offers a chance to attain a new qualitative level in investigating and monitoring processes in the near-Earth space, in particular those of a dangerous character. For implementation of fast and effective primary processing of a large flow of multidimensional information from the muon hodoscope URAGAN in a real time, a matrix approach to data representation was proposed and realized. Characteristics of the anisotropy of the angular distribution of muons provide a convenient tool for the study of the processes of cosmic ray flux modulation of atmospheric and extra-terrestrial origin.
This work was performed in the Scientific and Educational Center NEVOD with the state financial support provided by the Russian Scientific Foundation (RSF), project No. 17-17-01215 “Creation of a method for early diagnostics of geomagnetic storms based on digital processing of time series of observational matrices of a muon hodoscope”.
The authors have no competing interests to declare.
Astapov, II, Barbashina, NS, Dmitrieva, AN, et al. 2013. Study of heliospheric disturbances on the basis of cosmic ray muon flux anisotropy. J. Phys.: Conf. Ser, 409: 012196. DOI: https://doi.org/10.1088/1742-6596/409/1/012196
Astapov, II, Barbashina, NS, Dmitrieva, AN, et al. 2015. Local anisotropy of muon flux – the basis of the method of muon diagnostics of extra-terrestrial space. Advances in Space Research, 56: 2713–2718. DOI: https://doi.org/10.1016/j.asr.2015.05.039
Barbashina, NS, Kokoulin, RP, Kompaniets, KG, et al. 2008. The URAGAN wide-aperture large-area muon hodoscope. Instrum. Exp. Tech, 51: 180–186. DOI: https://doi.org/10.1134/S002044120802005X
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Dmitrieva, AN, Ampilogov, NV, Astapov, II, et al. 2015. Temperature effect corrections for URAGAN based on CAO, GDAS, NOAA data. Journal of Physics: Conference Series, 632: 012054. DOI: https://doi.org/10.1088/1742-6596/632/1/012054
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Yashin, II, Astapov, II, Barbashina, NS, et al. 2015b. Real-time experimental data of the muon hodoscope URAGAN accessible in www. Journal of Physics: Conference Series, 632: 012086. DOI: https://doi.org/10.1088/1742-6596/632/1/012086
Yashin, II, Astapov, II, Kokoulin, RP, et al. 2015a. Real-time data of muon hodoscope URAGAN. Advances in Space Research, 56: 2693–2705. DOI: https://doi.org/10.1016/j.asr.2015.06.003 | 0.844238 | 3.857811 |
Using the X-ray eyes of three space telescopes, astronomers have captured a behind-the-scenes look at the dramatic behavior of a newborn sun-like star, as it spins rapidly and churns out powerful and long-lasting eruptions.
The infant star, called V1647 Orionis, is known as a protostar, and was formed by clouds of surrounding gas and dust. The star is located 1,300 light-years away in McNeil's Nebula, which is a bustling hotspot of star formation in the constellation of Orion.
V1647 rotates once each day, which is around 30 times faster than the sun, and has two active X-ray emitting spots, where gas flows from a surrounding disk and feeds the growing star.
The young star has intrigued astronomers since it erupted in 2004 and lit up McNeil's Nebula for two years, dying down in early 2006, the researchers said. The stellar newborn acted up again in 2008, and has remained bright ever since.
In a new study, astronomers studied the source of the high-energy emissions using three separate X-ray space telescopes: NASA's Chandra X-ray Observatory, the Japanese Suzaku satellite, and the European Space Agency's XMM-Newton.
The researchers began studying V1647 Orionis shortly after it erupted in 2004, and monitored it through 2010, capturing data from both outbursts.
"The observations give us a look inside the cradle at a very young star," study co-author Joel Kastner, a professor at Rochester Institute of Technology in Henrietta, N.Y., said in a statement. "It's as though we're able to see its beating heart. We're actually able to watch it rotate. We caught the star at a point where it is rotating so fast as it gains material that it's barely able to hold itself together. It's rotating at near break-up speed."
The researchers used the star's X-ray light curves to determine its spin, which makes V1647 one of the youngest stars whose spin has been determined using an X-ray based technique, they said. The scientists were also able to identify the object as a protostar that is still in the process of forming.
"Based on infrared studies, we suspect that this protostar is no more than a million years old, and probably much younger," study lead author Kenji Hamaguchi, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Md., said in a statement.
V1647 is being fueled by gas from a surrounding disk, and could continue to grow this way for millions of years, before it is able to generate its own energy by fusing hydrogen into helium in its core, the way the sun and other mature stars do, the researchers explained. [Top 10 Star Mysteries]
Hamaguchi and his colleagues also studied two regions of V1647 that are emitting X-rays and are thousands of times hotter than the rest of the star. The two dynamic spots are located on opposite sides of the star, with the southerly one five times brighter than the other, the researchers said.
The newborn star's low density puffs it up to almost five times the size of the sun, making each of these hotspots sprawling birthmarks, measuring roughly the width of the sun.
During the star's extended eruptions, the researchers noted that V1647 gathers mass, spews plasma and X-rays, and exhibits a staggering increase in temperature.
"We think that magnetic activity on or around the stellar surface creates the super-hot plasma," Hamaguchi said. "This behavior could be sustained by the continual twisting, breaking, and reconnection of magnetic fields, which connect the star and the disk, but which rotate at different speeds. Magnetic activity on the stellar surface could also be caused by accretion of material onto it."
The X-ray emissions observed as the star rotates indicate that for its size, V1647 is spinning as fast as it can without shredding itself to pieces, the scientists said.
But despite the violent behavior witnessed from V1647 and the surrounding disk, the star appears to have been relatively stable since the researchers began studying it in 2004. The research combining observations from multiple X-ray satellites is expected to give astronomers better insight into what may be happening inside the dust-cloaked disks of young stars.
The detailed results of the study are published in the July 20 edition of the Astrophysical Journal. | 0.836085 | 3.916786 |
Meet the Ploonets
Our Moon might not always be the dedicated companion to Earth that it is now.
An international team of researchers has proposed a hypothetical new type of world it calls a “ploonet”: a former moon that escaped its host planet’s orbit and began circling its host star instead.
The team thinks ploonets could explain several unusual astronomical phenomena — and that our own Moon could one day join their ranks.
Hot Jupiters are a class of exoplanets that orbit incredibly close to their host stars. However, some astronomers believe they may have actually formed on the outskirts of their solar systems and migrated inward.
In a yet-to-be-peer-reviewed paper published on the pre-print server arXiv, the researchers detail their simulations of what might happen if a hot Jupiter started that migration with an exomoon in tow.
Based on their simulations, about 48 percent of the exomoons would detach from their hot Jupiters and begin orbiting their stars instead — as ploonets.
Theory of Some Things
The team believes ploonets could explain several unusual astronomical phenomenon.
An icy moon’s water could evaporate as it escapes its planet’s orbit and moves toward its star, for example, giving the ploonet a comet-like tail. The passage of such a ploonet across its star might explain why some stars appear to flicker.
Meanwhile, a ploonet that eventually crashed into its former host could create debris that might explain the strange rings found around some exoplanets.
“Those structures [rings and flickers] have been discovered, have been observed,” researcher Mario Sucerquia told Science News. “We just propose a natural mechanism to explain [them].”
Ploonethood could also explain why astronomers have yet to definitively find any exomoons despite predictions that the universe should be rife with them — the moons may get kicked out of their planets’ orbits before we can detect them. If we see the former moons after that point, we might just mistake them for new exoplanets.
Based on the researchers’ simulations, ploonets also have incredibly short lifespans, astronomically speaking — roughly 50 percent crash into their star or former host planet within half a million years, while others meet the same fate after less than a million years of ploonethood — which could further explain why we haven’t found any.
As for Earth’s own Moon, Sucerquia told Science News that it “is a potential ploonet” given that it moves about 4 centimeters farther away from Earth every year. But we don’t have to worry about it going its own way any time soon — at this rate, it won’t break free from Earth’s orbit for about 5 billion years.
READ MORE: Moons that escape their planets could become ‘ploonets’ [Science News]
More on the exomoons: Researchers Think They’ve Discovered the First Moon Outside Our Solar System | 0.861727 | 3.635417 |
Researchers have known for a while that a star called Gliese 710 is headed straight for our solar system, but they've now worked out precisely when it should arrive.
The star is currently hurtling through space at about 32,000 mph, and is around 64 lightyears away. (One lightyear is around 5,878,000,000,000 miles.)
Gliese 710 is about half the size of our sun, and it is set to reach Earth in 1.35 million years, according to a paper published in the journal Astronomy & Astrophysics in November.
And when it arrives, the star could end up a mere 77 light-days away from Earth — one light-day being the equivalent of how far light travels in one day, which is about 26 billion kilometers, the researchers worked out.
As far as we know, Gliese 710 isn't set to collide directly with Earth, but it wil be passing through the Oort Cloud, a shell of trillions of icy objects at the furthest reaches of our solar system.
So although 77 light-days sounds like a relatively safe distance, the speeding star could burst through the cloud and shoot these icy objects and comets all around our solar system. Any one of these is pretty likely to collide with Earth.
"Gliese 710 will trigger an observable cometary shower with a mean density of approximately ten comets per year, lasting for three to 4 million years," wrote the authors.
The team, who hails from Adam Mickiewicz University in Poland, used measurements from the European Space Agency's Gaia space observatory.
This new observatory is constructing the largest and most precise 3D space catalog ever made, totalling approximately 1 billion astronomical objects, which means the data are ten times more accurate than previous predictions.
There's still an error rate of around 50% though, which means Gliese 710 could actually scrape past at a mere 40 light-days away.
Some scientists speculate that a similar event of a star passing through the Oort cloud triggered the asteroid that wiped out the dinosaurs around 65 million years ago.
However, the Gliese 710 event could make the dinosaur extinction look relatively minor. At its closest distance, it will be the brightest and fastest observable object in the sky, and as the authors say in the paper, it will be the "strongest disrupting encounter in the future and history of the solar system."
But it's also not the only galactic body to worry about. There are as many as 14 other stars that could come within a 3 light-year distance to us any time over the next few million years. | 0.879635 | 3.888555 |
The futuristic bowels of the internet quaked today at the news that NASA will make some kind of holy-shit announcement next Monday. Already, some are speculating that it will concern whether Mars has flowing water, or other preconditions, for growing life.
Couple that with the impending launch of the Mars Insight Rover, set to launch next March and scheduled to perform experiments to determine Mars’ geophysical capabilities, and there’s a good possibility that Mars’ colonizability will take several giant leaps forward in this lifetime.
But what about after Mars? It’s hard to believe the colonization effort will stop, after all, at one destination. There isn’t enough room, or enough gravity, on Mars, to consider it for a long-term stay. Furthermore, the explorers of the past didn’t reach America, or Florida, or Missouri, and say, “Enough’s enough.”
No, the effort to establish other bases for human life should be expected to be ongoing. What are some of the most viable spots for a colony after Mars? Check out what they are and what to expect below.
The moon is still the likeliest place humankind will look to for establishing life after, or during, a Mars colonization. Of course, the same constraints still apply: almost non-existent gravity, non-existent atmosphere, no life and little chance for growing any.
Contrasted with Mars, the Moon is barren, which will mean a colonization effort will have to be, as many have imagined, a closed-bubble affair. That will be expensive, but pursuit of the matter is ongoing. Last year, Russia announced that it is aiming to colonize the moon by 2030.
Nevertheless, it will take a lot of money — more than Russia can afford alone — before the project is realized. But one should remain hopeful that if the effort to colonize Mars is a success, an international Moon colony becomes a slightly smaller leap for humankind to make.
With its comparable surface gravity to Earth (0.904 g-forces, versus Mars’ 0.38, the latter which could lead to complications like muscle loss and bone decalcification) and a relatively short commute (580 days to Mars 760), Venus makes a superficially welcoming sister planet for visits. Too bad its atmosphere is dense, poisonous, and tempestuous.
Then came the NASA scientist who postulated that a balloon of human-breathable air could float at cloud-top level, shielded from the sun by Venus’ outer atmosphere.
Though far-fetched, time and large expense could see experiments like a floating city attempted even in this lifetime. If they succeed, they could propel Venus from fantastic colonial what-if to Earth’s friendly, though slightly air-headed, next-door neighbor.
The dwarf planet Ceres is a part of the asteroid belt between Mars and Jupiter. The NASA satellite Dawn entered Ceres’ orbit earlier this year and has been tweeting images of its crater-covered surface.
Given Ceres’ location, its lack of atmosphere, etc., it is unlikely it would be viable as a full-on liveable colony until some major advances in deep space science.
That said, Ceres’ attractiveness could be as a work colony and base of location for asteroid mining. The reflections in the craters are believed to be ice, and Ceres also may contain an internal ocean of liquid water. Thus, if water becomes a scarce resource (as it most likely will, and arguably is already), Ceres could provide one way to plumb it en masse.
Mercury’s proximity to the sun and, consequently, its profound volatility in temperature, push it down the list of colonizable destinations. Seven-hundred-degree surface temps and no atmosphere make for a brutal place to establish shop.
Furthermore, Mercury’s surface gravity is twice that of the moon’s, and close to that of Mars, meaning if we can solve the physical challenges that low-gravity poses on our bodies on Mars first, we can implement that science on Mercury.
Like with Venus and its plant-growing capabilities, consider Mercury’s proximity for generating energy. That close to the sun, it could make for one hell of a charging station.
Or we could blow the planet to smithereens, Death Star-style, and harvest the energy of the Sun using Dyson spheres …
Ever since the Cassini spacecraft flyover in 2004 discovered Titan’s incredible atmosphere of hydrocarbons, imaginative thinkers like Julian Nott have speculated on Titan as a distant but enticing destination for human life.
Of course, temperature (70 Kelvin, positively cryogenic) and travel distance are an issue, but if future colonies need to keep the engine of exploration running, remember that Titan. | 0.835035 | 3.13939 |
Looking deep into the stars
The Large Binocular Telescope (LBT) on Mount Graham in Arizona, USA, is already one of the world’s most advanced optical telescopes. It consists of two 8.4-meter primary mirrors on a common mount structure. The LINC-NIRVANA near-infrared imaging instrument will combine the light from the two mirrors and provide a resolution comparable to a telescope that has a diameter of 23 meters.
Put another way, the LINC-NIRVANA instrument is like a camera app on your smartphone that would allow you to take pictures of the centre of a galaxy 53.5 million light-years away. But also an app that weighs 9.5 tons, has 139 motors, and took a team of international engineers ten years to build.
Involved in the complex LINC-NIRVANA project since the start, Ralf-Rainer Rohloff is an engineer and the head of the Mechanical Design Office of the Max Planck Institute for Astronomy in Heidelberg, Germany. He says that there are currently about 40 engineers from many different fields working on the project, as well as several astronomers.
“When planning the instrument, the astronomers attended meetings between the scientists and engineers where we discussed what is possible,” Rohloff says. “These astronomers needed to have a bit of a technical background, so they understood what we said, and on our side we needed a little bit of an astronomical background to understand what they wanted.”
The instrument will serve a number of functions, including imaging planets outside our solar system and studying the most distant galaxies in the universe. Given the size and cost of the LINC-NIRVANA project, several institutes from around the world have been involved in its development. Rohloff’s institute is responsible for coordinating the work of the German institutes working on the instrument, in cooperation with institutes in Italy and in the USA.
The instrument was completed in June 2015, then carefully packed during the summer and shipped from Germany to Arizona in September. Rohloff and the team visited Arizona in November to conduct a number of tests on the instrument on site.
“It was very exciting because we had no real problems and everything fit,” Rohloff says. “With such a long design and development process, we were all happy that it went very smoothly. The final installation will take place in 2016.”
When mounting an instrument that weighs 9.5 tons to an extremely sensitive telescope, precision and stability are essential. Nord-Lock Superbolt tensioners and wedge-locking washers were selected to mount the frame of the instrument to the frame of the telescope and play a key role.
“We chose Nord-Lock Superbolts and wedge-locking washers because they are the most secure,” Rohloff says. “When we were looking for washers, we learned that 70 percent of them are not really safe. In our case, the instrument must be completely secure – even slippage of a few hundred microns would be unacceptable.”
Nord-Lock products were also chosen because of the very precise clamp load needs to be achieved in the bolts in a very limited space.
“There is no room around the instrument for large wrenches,” he says. “With the Nord-Lock Superbolt solution, we can apply the exact torque needed using a small torque wrench, which is a big advantage.”
Now that this decade-long project is almost complete, Rohloff says he has plenty of other projects to keep him busy. His work often takes him to the remote, arid locations that make the best sites for telescopes, from the deserts of Spain to the mountaintops of Chile. He says that he has had a lifelong passion for astronomy.
“In my childhood I was already very interested in astronomy,” he says. “I even built my own small telescope then. It’s amazing to me now that I am helping build one of the largest telescopes in the world.”
The LINC-NIRVANA near-infrared imaging instrument will use the full binocular capability of the LBT. The instrument allows the coherent superposition of light from the twin 8.4-metres LBT single-eye telescopes on a single science detector, providing a resolution comparable to a telescope that has a 23-metre diameter.
Measuring approximately 5 x 4 x 4.5 metres, the LINC-NIRVANA weighs 9.5 tonnes and has 139 motors. Given the extraordinary requirements of such as system, it is absolutely crucial that the instrument and its optical bench maintain their 3-dimensional spatial position, leaving no margin for error regarding the components used.
FACTS: In a galaxy far, far away
The new astronomical instrument for the Large Binocular Telescope (LBT) will enable astronomers to see planets and galaxies extremely far away. One galaxy that astronomers may study is the giant elliptical galaxy Messier 87 (M87), also known as Virgo A or NGC 4486. It was discovered by the French astronomer Charles Messier in 1781 and has been popular with astronomers ever since.
M87 is part of the Virgo Cluster, located 53.5 million light-years away from Earth. The galaxy contains an exceptionally large population of so-called globular clusters, approximately 12,000 compared to 150 to 200 in the Milky Way.
In particular, the LBT telescope would investigate the nucleus of this galaxy, which has shooting out of it a jet of high-energetic plasma, which travels at relativistic speed, and is close to 5,000 light-years long. The plasma is being ejected from a supermassive black hole at the centre of the galaxy.
In the image above, cold matter from the Virgo Cluster falls towards the core of M87. Met by the relativistic jet it produces shock waves in the galaxy’s interstellar medium.
FACTS: The perfect spot
To reach optimum results modern telescopes need a special environment. The requirements for ground-based observatories include many clear nights per year as well as minimal light pollution from urban areas and low water vapour content in the atmosphere. That is why these telescopes are located in dry regions at high altitudes, such as USA’s southwest. LBT is located at an altitude of 3.221 metres on Mount Graham, Arizona.
FACTS: The Nord-Lock solution
Customer: Max Planck Institute for Astronomy in Heidelberg, Germany.
End-Customer: Large Binocular Telescope (LBT).
Location: Mount Graham, Arizona, USA.
Application: Mounting an astronomical instrument to the telescope frame.
Nord-Lock solution: 30 Superbolt CY-M20 tensioners and wedge-locking washers.
Product Benefits: Absolute stability with zero slippage. Able to apply the exact torque needed in a small space. | 0.859599 | 3.40001 |
On Saturn and the Flood
(Editor’s note: This excerpt comes from a book called Worlds on Collision by Immanuel Velikovsky. I came across this after I talked about the hypothetical symbology of Jupiter eating Saturn during the Great Conjunction on December 20-22 of 2020. Its interesting what this book says about the Flood/Deluge of Noah and these two planets having involvement. Keep all that in mind and I will link the blog where I mention Jupiter “eating” Saturn here. You can download Velikovsky’s book here from my Google Drive.)
Worlds in Collision comprises only the last two acts of a cosmic drama—one that occurred in the middle of the second millennium before the present era; the other during the eighth and early part of the seventh century before the present era. Prior to the events described in Worlds in Collision, Venus—following its expulsion from Jupiter—was on a highly eccentric orbit for a period of time measured certainly by centuries, perhaps millennia, before its near-encounters with the Earth.
While the actual beginning of the drama is shrouded in the mist of grey antiquity and difficult to pinpoint with exactitude, there is a point at which a clearer picture emerges. This is the time when the two giant planets—Saturn and Jupiter—approached each other closely. Possibly they were close for a long period of time, passing near one another as they traveled along orbital paths quite dissimilar to those of today.
Saturn and Jupiter are so often associated in cosmological history that sometimes I even considered the possibility that they may have constituted a double star system, of which there are many in the universe. I said that Saturn and Jupiter were stars, though today we know them as planets. Actually, in Worlds in Collision, in the last chapter, I also used the word “star” in referring to the two giant planets. There I wrote, with respect to the future, that “some dark star, like Jupiter or Saturn, may be in the path of the sun, and may be attracted to the system and cause havoc in it.”1 At that time it was said that they were planets, not stars, while today it is known that Jupiter and Saturn, too, are star-like, producing several times the amount of heat they receive from the Sun.2
Today Jupiter moves on an orbit of twelve terrestrial years and is about half a billion miles away from the Sun, whereas we are some ninety-three million miles distant. Saturn is much farther: it is the next planet beyond Jupiter, approximately another half billion miles outside Jupiter’s orbit. They are presently not of the same size or volume. Jupiter is more than three hundred times more massive than the Earth, but Saturn only ninety-five times. In volume, Jupiter is about thirteen hundred times that of the Earth, whereas Saturn is only about eight hundred times that of the Earth. Today Jupiter is actually more massive than all the other planets, Saturn and the rest, put together.
The cosmological thought of ancient peoples conceived of the history of the Earth as divided into periods of time, each ruled by a different planet. Of these the epoch of Saturn, or Kronos, was remembered as a time of bliss, and it was made to precede the period during which Jupiter was the dominant deity. Insofar as I could understand the physical events that affected the globe in times preceding the Middle Kingdom in Egypt, I was able to explain them as the results of a disturbance in which both Jupiter and Saturn participated. Various peoples witnessed the events and described them, as a celestial-human drama in different forms: the Greeks, for example, had Jupiter-Zeus, the son of Saturn-Kronos, dethrone his father and banish him, and take his place to become the supreme deity. In Egyptian folklore or religion the participants in the drama are said to be Osiris-Saturn, brother and husband of Isis-Jupiter. And it is not that the wife dethrones the husband, nothing of the kind — there is, instead, a fight going on in the sky in which some body, described as Seth, attacks Osiris and kills, actually dismembers him; and after this lsis travels in search of the dismembered parts of Osiris. You see how the two dramas are hardly at all alike. I believe that my long experience in interpreting dreams and associations of my fellow men probably was of help to me to see similarities where the similarities were not easily seen.
An Egyptologist, one of the most prominent Egyptologists of the last forty years (he died several years ago), Sir Alan Gardiner, wrote—and I read it twice in his writings3— that he could not understand who Osiris was. Osiris occupied an extremely important role in the religion, folklore, and rites of Egypt. But who was he? Was he a king who had been killed? — Gardiner could not figure it out. He did not understand that Osiris represented a planet, Saturn, as did Tammuz in Babylon. Sir James Frazer, author of The Golden Bough, describes in the volume Adonis, Osiris, Attisthe great lamentations and crying for the fate of Tammuz. Similar rites were observed in Egypt for Osiris; and it should be understood that these lamentations were actually for Saturn, because the time of Saturn—the Golden Age of Saturn, or Kronos—came to its end when the supreme god of that period, the planet Saturn, was broken up.
The Tractate Brakhot of the Babylonian Talmud, points to the celestial body Khima as the source of the Deluge; Khima is to be identified with Saturn.4
Also in the Mexican codices it is said that the first world age, at the end of which the Earth was destroyed by a universal deluge, and which was therefore called “the sun of water” or Atonatiuh, was presided over by Ce-acati, or Saturn.5
The ancient sources all point to Saturn; but how did Saturn cause the Deluge? What did really happen?
Suppose that two bodies, such as Jupiter and Saturn, were to approach one another rather closely, so as to cause violent perturbations and huge tidal effects in each other’s atmospheres. As a double star, or binary, they might interact to the extent that, under certain conditions, their mutual perturbation will lead to a stellar explosion, or nova. If what today we call Jupiter and Saturn are the products of such a sequence of events, their appearance and respective masses must formerly have been quite different. Prior to its cataclysmic disruption and dismemberment Saturn must have exceeded Jupiter in size. At some point, during a close approach to Jupiter, Saturn became unstable; and, as a result of the influx of extraneous material, it exploded, flaring as a nova which, after subsiding, left a remnant that the ancients still recognized as Saturn, even though it was but a fraction of the size of the celestial body of earlier days.
In Saturn’s explosion much of the matter absorbed earlier was thrown off into space. Saturn was greatly reduced in size and removed to a distant orbit—the binary system was broken up and Jupiter took over the dominant position in the sky. The ancient Greeks saw this as Zeus, victorious over his father, forcing him to release the children he earlier had swallowed, and banishing him to the outer reaches of the sky. In Egyptian eyes it was Horus-Jupiter assuming royal power, leaving Osiris to reign over the kingdom of the dead.
My conclusion that, as a result of its interplay with Jupiter, Saturn exploded as a nova, I found confirmed in many ancient sources, in which Saturn is regularly associated with brilliant light; but I was led to this idea first of all by a certain clue contained in the Biblical account of the Deluge. The story as found in the book of Genesis starts with these words: “And it came to pass after seven days, that the waters of the Flood were upon the earth”(Genesis 7:10). It is not explained, after seven days of what? Some words seem to be missing here from our text of the Old Testament. It is clear, however, that Isaiah refers to the same seven days in his description of the messianic age to come, when “the light of the moon shall be as the light of the sun, and the light of the sun shall be sevenfold, as the light of the seven days…” (Isaiah 30:36). It is conceivable that the Earth was, at that time, a satellite of Saturn, afterwards possibly becoming a satellite of Jupiter.
With the end of the seven days of light the Earth became enveloped in waters of cosmic origin, whether coming directly from Saturn—and Saturn is known to contain water—or formed from clouds of hydrogen gas ejected by the nova, which combined, by means of powerful electrical discharges, with the Earth’s own free oxygen. There are definite indications of a drastic drop in the atmospheric oxygen at the time of the Deluge—the survivors of the catastrophe are said in several sources to have been unable to light fires. The Midrashim and other ancient sources describe the waters of the Flood as being warm;6 in addition the waters may have been rich in chlorine, an element which in combination with sodium forms common salt.
Marine geologists are unable to trace the origin of the huge amounts of chlorine locked in the salt of the Earth’s oceans, the Earth’s own rocks being rather poor in this element and incapable of supplying it in the needed quantities. Chlorine may thus be of extraneous origin; being a very active element, it could possibly be present in some different combination on Saturn.
After the Deluge many new forms of life came into being, especially plant life. Thus it happened that Saturn was later called a god of vegetation. Frazer in his Golden Bough considered Osiris and Tarnmuz to be nothing more than vegetation gods—so strong was Saturn’s connection with the new forms in the plant kingdom that appeared following the Deluge.
The Midrashic sources relate that, during the Deluge, all volcanoes erupted;7 and other ancient accounts assert the same. Changes took place in the lithosphere as well as in the biosphere. Most pronounced, however, were the changes in the hydrosphere — the volume of water on the Earth was vastly increased. And it is of interest that the Atlantic Ocean was called by the ancients “the sea of Kronos”8—indicating that it came to be only after the Deluge.
The memory of these stupendous events survived for millennia and vestiges of the cult of Saturn persist even till today. One of these memorials is the feast of light, celebrated in mid-winter: Hannukah or Christmas, both stemming from the Roman Saturnalia. These are all festivals of light, of seven days’ duration, and they commemorate the dazzling light in which the world was bathed for the seven days preceding the Deluge; in their original form these festivals were a remembrance and a symbolic re-enactment of the Age of Saturn. It was said that in that age there had been no distinction between masters and servants — thus in Rome, for the duration of the Saturnalia festival, the household slaves were freed, and were actually waited on by their masters.
Also the statue of Saturn which used to stand in the Roman Forum was for a time released from its bonds. This statue, which had bands around its feet, represented the planet Saturn with its rings — it was understood that it was Jupiter that had bound Saturn with these bonds after he had overthrown Saturn. Astronomers are unable to explain their origin, but they must have formed in that event in which Jupiter disrupted Saturn.
There is evidence that the ancient Maoris of New Zealand were also aware of the rings around Saturn. They called the planet Parearau, which means “her band quite surrounds her.”9
Saturn was the chief deity of, among other peoples, the Phoenicians and the Scythians—in cuneiform sources the Scythians are called Urnman-Manda, or “the people of Saturn.” The Phoenicians used to bring human sacrifices to the planet, calling it Moloch, or “king.” Usually children were the victims, consumed by Moloch, as Saturn had devoured his own children. Porphyry records the persistence in some cities of the Greek world of human sacrifices to Saturn well into Roman times.10″
Now I also want to point out that some scholars associate Jupiter with “birthing” comets. This makes some sense when looking at the Birth of Jesus and the star that the magi saw and followed from the East. Some believe that this star was connected to Jupiter and Venus while some believe it was Jupiter as Saturn. Scholars are even led to believe that these conjunctions somehow were connected to a comet like they believe the flood was connected to a comet. Some modern scholars even go so far to say the deluge comet was Haleys comet. Here are a few screenshots from Larry Radka’s book on Jupiter and comets.
You can find his book here for free. | 0.927195 | 3.475371 |
Questo prodotto non è più in magazzino e pertanto non può essere acquistato fino ad ulteriore avviso.
Prego, tenga presente che questo prodotto è in inglese
Purtroppo, questa descrizione non è stato tradotto in italiano, in modo da trovare a questo punto una descrizione inglese.
Sky & Telescope's updated model of Venus relied on a mosaic of images from the Magellan mission to Venus (1990-1994). Magellan mapped more than 98% of Venus at a resolution of about 100 meters (330 feet); the effective resolution of this globe is 5 kilometers. Other data used for the globe came from the Pioneer Venus mission, the Soviet Venera 15 and 16 spacecraft, and radar images from Arecibo Observatory. Altogether this globe, which comes with a 16-page booklet, offers a beneath-the-clouds glimpse of our sister planet in unprecedented detail. Sky & Telescope produced the globe in collaboration with NASA and the U.S. Geological Survey.
Venus is the planet in our solar system most like Earth in size and mass. Yet it’s a very different place, with a runaway greenhouse effect that creates surface temperatures exceeding 850°F (450°C) — hot enough to melt lead! The Venus globe is particularly intriguing because we can actually see the surface without the planet’s dense, opaque cloud cover getting in the way, thanks to global radar mapping conducted by orbiting Soviet spacecraft. The surface of S&T’s globe is color-coded with blues, greens, and browns, and much topographical diversity. Altogether it looks like another Earth, though obviously it’s utterly different. But that won’t stop you exploring the landscape virtually.
Did You Know?
Venus is an intensely volcanic planet whose geology has been shaped by vast eruptions throughout its history. Lava plains cover 85% of its surface, and geologists have mapped more than 1,000 volcanic features — some of which might be actively erupting today. | 0.841112 | 3.272976 |
The earth’s coordinates, latitude is the angle between the equatorial plane and the straight line that passes through that point and is normal to the surface and longitude the angle east or west from a reference meridian to another meridian that passes through that point.
Is very important to calculate it accurately (up to 6 decimal places) to get a more accurate sundial, you can use this tool, find your home, zoom in and move the marker over your wall. 回到顶部
Declination of wall
The declination of a wall is the angle in degree between the south and perpendicular axis of the wall (north for the southern hemisphere), is counted positive towards West and negative towards East.
There are more method to calculate the declination, let’s see some:
A compass indicates the direction of the magnetic pole, but there can be several errors in the measurement, bisurbation like mountains. You can use a easy tool 在地图上测量
select distance mode, move the marker over the wall use max zoom and click to get a second marker parallel to the wall, read the value of the direction and add 90 degrees to get the declination
Get the sun position with this tool 太阳位置
set coordinates date and time (accurately around noon), move the mouse over the sun icon and read the azimuth and elevation, whit this data you can calculate the shadow of a nail, the the difference (theory for south and real value) in degrees is the declination 回到顶部
It is equivalent to the difference of time, early or late, between the meridian passage of the sun (time zones which are adjusted our watches, 15° every hour), and that the longitude of the sundial. 回到顶部
Equation of time and analemma
The dials do not convert the common apparent solar time in standard time. It therefore has a variation of 15 minutes in a year, known as the equation of time, caused by the fact that the Earth’s orbit is elliptical and not circular, and is inclined with respect to the equator (see ecliptic)
The visual representation of this equation is the analemma, in astronomy indicates a particular geometric figure-eight curve that describes the position of the sun on different days of the year, at the same time and in the same locality.
Due to the tilt of Earth’s axis ( 23.5° ) and ellipticity Earth’s orbit, the height of the Sun above the horizon is not the same, day after day, and the combined effect is that of the figure described. The vertical coordinate of each point corresponds to the declination of the Sun at that time, while the horizontal coordinate indicates the deviation of the solar position earlier or later than the average time ( as shown by the clocks ) .
A Simple Expression for the Equation of Time:
n = day of the year.
Δt = 9.873 sin( 4π / 365.242 ( n - 81 )) - 7.655 sin( 2π / 365.242 ( n - 1 )) 回到顶部
Build a sundial manually
The most important element of the sundial is the gnomon, which consists of a rod that casts its shadow on a sundial on which the hour lines must be drawn. By the type of sundial (vertical, horizontal, equatorial ring, etc.), the size, from the coordinates and from the declination determines the length and its position. 回到顶部
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Houston, we have a planet!
Tom Wagg has become one of the youngest people to discover a new planet now that after two years of research, scientists have confirmed that Wagg in fact identified a new planet when he was just 15 years old, working as an intern at a research university in the U.K.
Wagg, now 17, was interning with Keele University’s astrophysics department, called WASP (Wide Angle Search for Planets), when he identified what he thought looked like a planet.
“I was looking through thousands of these light curves and I just happened to see one that was really good and I kind of was in disbelief for a moment," Wagg told TODAY.com. "I did all the usual checks and they all kind of confirmed it."
According to Coel Hellier, a professor of astrophysics at Keele and a project leader of WASP South for almost 10 years, there is a lot of work that goes into proving a tiny dip in a star is actually a planet, which is why it's taken two years to confirm Wagg's finding was really a planet.
“You have to do lots of follow-up, observations," Hellier said. "You’ve got to prove that it’s got the right mass to be a planet, the right size to be a planet.”
WASP monitors millions of stars in search of tiny dips in the light of those stars, which indicate that a planet has orbited in front of a star thus blocking out a little part of the light. It's a process that over the last 10 years, astronomists have greatly improved upon, to the point that there now 1,000 known planets orbiting other stars in our galaxy.
Hellier said Wagg’s finding is important to the world of astrophysics, because it helps research institutions such as Keele map out exactly what sort of planetary systems exist in the universe.
“Tom’s planet helps us fill out the picture of what sort of planetary systems there are around stars in our galaxy,” said Hellier.
Researchers say Wagg's planet is a a lot like Jupiter, a large gas giant planet. While it's about the same mass and size as Jupiter and made almost entirely of hydrogen, the main difference is that Jupiter takes 10 years to go around it star (the sun) whereas the planet Wagg found does its orbit in only two days. As a result it will be much hotter than Jupiter.
Hellier says this means Wagg’s planet is much closer to its star, and that a planet of that size and atmosphere so close to a star is unlike anything in our solar system.
Although it could take years for Wagg’s planet to be named (for the time being it's name is WASP-142b), the 17-year-old says if it were up to him he would name his planet “Zeus,” the Greek equivalent of the Roman God “Jupiter,” who the Greeks described to be a bit more temperamental and angry.
Wagg said his plan is to study physics in college. He starts his college application process, and that this experience has also helped him discover more about himself.
“No matter how young you are, you can do and find anything," he said. "It reminds you to work harder, and even though I'm quite young, I can still go on to do something quite good.”
How’s that for making the most out of an internship? | 0.887726 | 3.336834 |
By Jorge Lillo Box, European Southern Observatory (ESO)
Like a person, planets are born, evolve rapidly in the early stages of their lives, and spend most of their time interacting with others in their surroundings (in this case stars, other planets, comets, asteroids, etc.). At last, they die in a joint evolution with the system where they lived. The large crop of extrasolar planets discovered to date (around two thousand) is providing valuable information about how exactly these processes take place. But there are still many open questions that are key to understanding the whole picture. Starting from a planet’s birth and finishing with its death, I will briefly review some big projects and facilities aimed at answering these crucial questions.
Planets are byproducts of stellar formation. Stars are formed after the collapse of a molecular cloud. The result of this process is a massive object (the star) surrounded by a circumstellar disc composed of gas and dust. This disc is indeed the incubator where planets will be formed. However, the exact mechanism of planet formation is still a mystery, with different theories trying to explain the process and to conjugate theory and the observations. A property that seems to have a key role in planet formation is the amount of gas and its lifetime in the disc. Also, the amount of warm water, and in general the chemical contents available in the disc will determine the type of planets that can be formed. Two key projects using data from the Herschel mission of the European Space Agency (ESA) aim at characterizing these parameters in the different stages of planet formation: GASPS and DUNES. They are producing impressive results with the detection of warm water vapor in these protoplanetary discs, a crucial ingredient linked with planet formation and the development of life. Additionally, the observations carried out by the ALMA radio-interferometer (Chile) are shedding light on the formation process, detecting protoplanets in the first stages of their live as well as possible signatures of multi-planetary formation.
During the process of forming a planet within a protoplanetary disc, other minor objects are also created. Moons, comets, asteroids, and minor planets are also by-products of this process and could play a key role in the subsequent evolution of the planetary system, as well as being crucial for the development and support of life. For example, we know that tidal forces induced by the Moon on our Earth have an important role in transporting heat from the equator to the poles, contributing to the climate patterns of our planet. Similarly, in other extrasolar systems, these objects may exist and play similar or even more important roles. Additionally, the properties of their orbits (inclinations, eccentricities, etc.) are a direct consequence of the dynamical evolution of the system during its first stages. Hence, the detection of minor bodies in extrasolar systems will contribute to our knowledge on planet formation and evolution, and potentially the evolution of life. The HET and TROY projects aim at detecting these minor objects. First, the HET project has the challenging goal of detecting the first exomoons—natural satellites orbiting around known planets. They have obtained different candidates, although no confirmation has been published as for today. The TROY project aims at detecting exotrojan planets—bodies co-orbiting with known extrasolar planets in the stability points of their orbit. In the Solar System, we know that a cloud of trojans inhabits the Lagrangian points L4 and L5 of Jupiter’s orbit. Indeed, even our Earth has a long-term 300-meter diameter object co-orbiting with us.
On the other side, important space missions are discovering large amounts of exoplanets with which we can start doing statistics of planet populations. For instance, thanks to NASA’s Kepler mission, we now know that solar-like stars in our Galaxy harbor on average 0.77 earth-size planets. This is a crucial discovery since it tells us that earths are more or less commonly formed in the Universe. In the forthcoming years, new space missions such as TESS, CHEOPS, PLATO, Gaia, or JWST will each contribute to improve these numbers by detecting, and characterizing, extrasolar systems in other niches (for example, long-period planets).
The end of the story, as it happens in our own lives, is tragic. After several billion years, the host star exhausts its internal fuel (hydrogen) and starts to contract, while the external layers expand, making the star several times bigger than it was during its adult phase—becoming a red giant. The consequence of this process for the surrounding planets can be traumatic and catastrophic, possibly being engulfed by the star after a spiraling in-fall. But some of them can still survive. Determining the conditions for a planet to be engulfed by its host star is still a matter of debate. It is important to note that this process will also take place in our Solar System (although in several billion years). Hence, it is crucial to understand how planets die, and under which conditions, to know the future and the expiration date of our Earth. Several projects like EXPRESS, TAPAS or JOTA are currently looking for planets orbiting giant stars in order to contrast the theoretical predictions with actual data to shed light on the end of planetary systems.
A great technological and scientific effort is being put in to the study of all these processes. Understanding how planets are formed, evolve, and interact with other bodies in the system along their lives and finally finish their lives, is crucial to understanding our own world. The Pale Red Dot project is contributing to this by trying to detect the closest planetary system that we can find, a cousin of our own Solar System. Who knows what surprises this work will bring? Just a few months left to get the answer…
About the author.
Dr. Jorge Lillo-Box is a fellow at the European Southern Observatory (Santiago de Chile). Jorge studied Physics at the Complutense University and University of La Laguna. Afterwards he moved to the Astrobiology Center (INTA-CSIC, Madrid) where he got his PhD in 2015. Since last year he is settled in Chile where, if he is not pointing to a star at the Paranal Observatory, he would be delving into the study of the evolution of planetary systems in the last stages of their lives and in the detection of minor bodies through the TROY project. Among the several planets he has discovered in different niches, we highlight the first planet transiting a giant star or the closest planet to a host star ascending the Red Giant Branch, Kepler-91b. | 0.916601 | 3.925414 |
Star-quake vibrations lead to new estimate for Milky Way age. Data gathered by NASA’s now defunct Kepler telescope provides a solution to an astronomical mystery.
Star-quakes recorded by NASA’s Kepler space telescope have helped answer a long-standing question about the age of the “thick disc” of the Milky Way.
In a paper published in the journal Monthly Notices of the Royal Astronomical Society, a team of 38 scientists led by researchers from Australia’s ARC Centre of Excellence for All Sky Astrophysics in Three Dimensions (ASTRO-3D) use data from the now-defunct probe to calculate that the disc is about 10 billion years old.
“This finding clears up a mystery,” says lead author Dr. Sanjib Sharma from ASTRO-3D and Australia’s University of Sydney.
“Earlier data about the age distribution of stars in the disc didn’t agree with the models constructed to describe it, but no one knew where the error lay — in the data or the models. Now we’re pretty sure we’ve found it.”
The Milky Way — like many other spiral galaxies — consists of two disc-like structures, known as thick and thin. The thick disc contains only about 20 percent of the Galaxy’s total stars, and, based on its vertical puffiness and composition, is thought to be the older of the pair.
To find out just how much older, Dr. Sharma and colleagues used a method known as asteroseismology — a way of identifying the internal structures of stars by measuring their oscillations from star quakes.
“The quakes generate soundwaves inside the stars that make them ring, or vibrate,” explains co-author Associate Professor Dennis Stello from ASTRO-3D and the University of New South Wales.
“The frequencies produced tell us things about the stars’ internal properties, including their age. It’s a bit like identifying a violin as a Stradivarius by listening to the sound it makes.”
This age-dating allows researchers to essentially look back in time and discern the period in the Universe’s history when the Milky Way formed; a practice known as Galactic-archaeology.
Not that the researchers actually hear the sound generated by star-quakes. Instead, they look for how the internal movement is reflected in changes to brightness.
“Stars are just spherical instruments full of gas,” says Sharma, “but their vibrations are tiny, so we have to look very carefully.
“The exquisite brightness measurements made by Kepler were ideal for that. The telescope was so sensitive it would have been able to detect the dimming of a car headlight as a flea walked across it.”
The data delivered by the telescope during the four years after it was launched in 2009 presented a problem for astronomers. The information suggested there were more younger stars in the thick disc than models predicted.
The question confronting scientists was stark: were the models wrong, or was the data incomplete?
In 2013, however, Kepler broke down, and NASA reprogrammed it to continue working on a reduced capacity — a period that became known as the K2 mission. The project involved observing many different parts of the sky for 80 days at a time.
The first tranche of this data represented a rich new source for Dr. Sharma and colleagues from Macquarie University, Australian National University, University of New South Wales and the University of Western Australia. They were joined in their analysis by others from institutions in the US, Germany, Austria, Italy, Denmark, Slovenia and Sweden.
A fresh spectroscopic analysis revealed that the chemical composition incorporated in the existing models for stars in the thick disc was wrong, which affected the prediction of their ages. Taking this into account, the researchers found that the observed asteroseismic data now fell into “excellent agreement” with model predictions.
The results provide a strong indirect verification of the analytical power of asteroseismology to estimate ages, says Professor Stello.
He added that additional data still to be analyzed from K2, combined with new information gathered by NASA’s Transiting Exoplanet Survey Satellite (TESS), will result in accurate estimates for the ages of even more stars within the disc and this will help us to unravel the formation history of the Milky Way.
Reference: “The K2-HERMES Survey: age and metallicity of the thick disc” by Sanjib Sharma, Dennis Stello, Joss Bland-Hawthorn, Michael R Hayden, Joel C Zinn, Thomas Kallinger, Marc Hon, Martin Asplund, Sven Buder, Gayandhi M De Silva, Valentina D’Orazi, Ken Freeman, Janez Kos, Geraint F Lewis, Jane Lin, Karin Lind, Sarah Martell, Jeffrey D Simpson, Rob A Wittenmyer, Daniel B Zucker, Tomaz Zwitter, Timothy R Bedding, Boquan Chen, Klemen Cotar, James Esdaile, Jonathan Horner, Daniel Huber, Prajwal R Kafle, Shourya Khanna, Tanda Li, Yuan-Sen Ting, David M Nataf, Thomas Nordlander, Mohd Hafiz Mohd Saadon, Gregor Traven, Duncan Wright and Rosemary F G Wyse, 12 October 2019, Monthly Notices of the Royal Astronomical Society. | 0.8801 | 3.988565 |
A surprisingly inexpensive setup of amateur equipment is helping astronomers on their quest to find Kuiper Belt objects of every size to better understand how planets formed in our solar system.
Blink and you’ll miss it.
Every now and then a star appears to flicker out for a fraction of a second, its light blocked when a small object in the outer solar system passes in front of it. While some of these objects are large enough to be seen by the sunlight they reflect, most are far too small and thus too faint to be detected directly. So-called stellar occultations, where the light of a background star briefly winks out, are one of the only ways to know these objects exist.
Now, astronomers using amateur equipment to monitor some 2,000 stars have discovered what appears to be a kilometer-size object — a missing link between the size of the dwarf planets and the many, much smaller objects in the far-out Kuiper Belt. Its mere existence points to a great many more where it came from and promises to shed light on how planets formed in the solar system.
A Belt of Ancient Remnants
The Kuiper Belt is a sparse disk of icy rocks extending 20 a.u. beyond Neptune’s orbit. These objects are the building blocks leftover from our solar system’s planet formation. Thanks to their cold, dark and lonely environment, they’ve remained largely unchanged over the past 4.5 billion years or so. The largest and more famous representatives are the three dwarf planets Pluto, Haumea, and Makemake, which span 2,400 km, 1,600 km, and 1,400 km, respectively. But the disk probably contains hundreds of thousands of smaller objects, too.
Planets are thought to have formed by accretion, pieces glomming onto each other to build successively bigger bodies. The leftovers of this process ought to include a good deal more smaller objects than larger ones; indeed, monitoring stars for occultations has turned up several candidates less than a kilometer in size. But until now, surveys hadn’t seen kilometer-size objects.
To extend the search toward the rarer, larger Kuiper Belt objects, Ko Arimatsu (National Astronomical Observatory of Japan) led a team in setting up two identical observing systems using off-the-shelf equipment. The two setups each included an 11-inch Celestron astrograph, equipped with a ZWO ASI1600 MM-C CMOS camera, on a Takahashi equatorial mount. Combined with a focal reducer, control computer, and data storage, the total cost of each system came to $16,000 — relatively cheap compared to most professional equipment.
Dubbed the Organized Autotelescopes for Serendipitous Event Survey (OASES), the telescopes were set up on the rooftop of the Miyako open-air school on Miyako Island, Japan. Having two identical systems helped the astronomers correct for other objects that might block or alter a star’s light, such as birds, airplanes, or atmospheric turbulence.
A Kilometer-size Kuiper Belt Object
Observing for a little over a year, the telescopes amassed 60 hours under good weather conditions over the course of about 13 months. Put in terms of observing hours per star in the field of view, OASES captured the equivalent of 60,500 “star hours.” Out of all of this data — which amounts to 50 terabytes — Arimatsu and colleagues found a single blip that marked a candidate Kuiper Belt object between 1.2 and 2.1 kilometers in radius. The discovery appeared in Nature Astronomy on January 28th.
“This is a real victory for little projects,” Arimatsu says. “Our team had less than 0.3% of the budget of large international projects. We didn’t even have enough money to build a second dome to protect our second telescope! Yet we still managed to make a discovery that is impossible for the big projects.”
Granted, the scientists only have a single kilometer-size detection in hand, but even that one event is more than they expected based on the number of smaller Kuiper Belt objects. The fact that they were able to detect even a single kilometer-size object suggests an abundance of icy rocks of this size, perhaps indicating that this was the typical size of protoplanetary bodies in the primordial solar system.
For the researchers, the event marks a proof of concept: “Now that we know our system works, we will investigate the Kuiper Belt in more detail,” Arimatsu says. | 0.844422 | 3.934163 |
Scientific intuition tells us that a comet's nucleus should be a frozen mountain of ice and dust. But that's not what Deep Space 1 discovered when it flew past Comet 19P/Borrelly last year. A recently released analysis of spacecraft spectra finds that Borrelly's "icy heart" exhibits no trace of water ice or any water-bearing minerals. Moreover, the nucleus is actually quite hot — ranging from 300° to 345° Kelvin (80° to 160° F).
What this means, according to Laurence Soderblom (U.S. Geological Survey), who led the analysis team, is that virtually all of the comet's surface has become inactive ice is present on too little of it to be detected spectroscopically. As further evidence, Soderblom notes that gas and dust appear to be escaping only from localized jets totaling less than 10 percent of the surface seen by the spacecraft. Ground-based observations also show Borrelly to be a weak producer of gas and dust, typically releasing less than a ton of water per second. Because this comet has been trapped in a 7-year-long orbit around the Sun for at least two centuries, scientists believe it has exhausted most of the volatile consituents needed to create an impressive coma and tail.
Deep Space 1's spectra weren't entirely featureless: the comet's inky black nucleus exhibits an unexplained absorption at 3.29 microns. Soderblom guesses that this might be the signature of polyoxymethylene (a chained polymer of formaldehyde, H
Mission scientists are thrilled to have any spectra at all to work with. Just as it passed 2,170 kilometers from the comet last September 22nd, Deep Space 1 scored a direct hit with its camera-spectrometer, recording 45 scans across the 8-km-long nucleus. And because only a handful of tightly collimated jets were spewing into space, the spacecraft had a clear sightline through the inner coma. The resulting images record features on the nucleus as small as 48 meters — far more detailed than the views of Comet Halley returned by the Giotto and Vega spacecraft in 1986. | 0.820127 | 3.87752 |
X-ray echoes from binary star system Circinus X-1 are helping astronomers measure its distance from Earth.
Imagine ripples spreading out from a drop of water falling on a tepid lake. The concentric circles that radiate out from the center all have a common center, a geometry common in wave interactions, such as sound waves radiating from a speaker or light echoing in space.
Light echoes occur when a flash of radiation from an astronomical source collides with intervening matter, giving astronomers a new perspective on celestial happenings. In the case of the X-ray-emitting binary system named Circinus X-1, light echoes provide an unexpected opportunity to measure its distance directly, putting an end to years of debate. On June 20th Sebastian Heinz (University of Wisconsin-Madison) and colleagues reported on X-ray light echoes around this system in the Astrophysical Journal.
In late 2013 the neutron star at the center of Circinus X-1 flared, creating four concentric rings that astronomers spotted a few months later. The brief flare bounced off intervening dust clouds to form the concentric circles, which look like they circle the neutron star — but it turns out this is an optical illusion
How did the Rings Form?
When the neutron source flared, it emitted a brief flash of X-rays in every direction. Some of these X-rays traveled straight to Earth, but some of them scattered off intervening dust. The scattered X-rays take longer to arrive, and the lag in their arrival time gives a precise geometric measurement of the distance to the source.
The figure on the right outlines light echoes’ optical illusion. An X-ray travels outward from the neutron star at an angle “α,” but bounces off a screen of dust between the neutron star and the observer. Because of its detour, the observer sees the photon arrive at an angle “θ,” as if it came not from the neutron star but from above it. In a given moment, the observer will see all the X-rays scattering at a certain angle. Just like a protractor, all of these scattered photons come in at the same angle and form an illusory ring of light. If astronomers watched for long enough, they would see this circle ripple outward, as X-rays come in from ever larger angles.
In the case of Circinus X-1, there’s not just one but four dust clouds between the neutron star and us. So rather than watch a single ring ripple outward over time, the astronomers spotted four concentric rings.
The team collected the X-ray data via the Chandra X-Ray Observatory. They also studied carbon monoxide maps of the clouds themselves, compiled by the Mopra radio telescope in Australia, which told them how far away the clouds were from Earth. Together, these data sets allowed them to calculate Circinus X-1’s distance from Earth using simple geometry: 30,700 light-years, more than twice a previously published distance.
Knowing an object’s distance from Earth can tell us a lot about it, such as its intrinsic brightness. Just as a lamp right next to you seems to shine brighter than one across the street, knowing the distance to Circinus X-1 puts its apparent brightness into perspective. Now astronomers can begin to understand how the neutron star’s flares fit into its total energy output. | 0.812055 | 4.012805 |
What causes Moon phases? Why can’t Earth’s shadow explain Moon phases? How does the geometry of the sun, Earth, and Moon cause lunar phases? During what phase can an eclipse occur? This simulation demonstrates how moon phases occur. Students use a white ball to represent the Moon and a lamp to represent the Sun. Holding the ball and turning to simulate the Moon’s orbit, students watch how the lit portion of the ball changes depending on its relative position.
This is the written activity. To see the video instructions for the same activity click here: Video: Moon Phases—Modeling how they occur; including Solar and Lunar Eclipses
❑ Where is the Moon in its orbit during each of its phases?
❑ How does the Moon's position determine whether or not we experience an eclipse?
❑ Why can't a crescent moon be caused by Earth's shadow?
♦ Eclipses can only happen on two days per cycle, but are rare.
♦ Moon phases depend on the geometry between the Sun, Earth, and the Moon.
♦ Solar eclipses can only occur during the new moon phase.
♦ Lunar eclipse can only occur during the full moon phase.
♦ Moon phases occur in regular, repeating, logical patterns.
TEKS 6.11A, 8.7B
VA SOL ES.3.b
White ball on stick (one per student--suggestions are included); bright, clear bulb in free-standing lamp (one per class); extension cord if needed.
Set up the lamp in the center of the room. Close blinds, etc Full darkness isn't necessary depending on how bright your bulb is.
This lab takes about 30 minutes (more with writing assignments)
Extensive teacher notes address the many questions that come up. You shouldn’t have to do outside research on this topic unless you want to.
• Scaffolded writing prompts & lab reporting
Answer Keys and Teacher Notes address most questions and issues that might arise in this study—you shouldn’t have to do any outside research unless you want to.
Connect with me: If you have questions or problems, please let me know and I’ll get back to you as soon as I can.
This resource (along with all resources sold on this site) can be found inside the membership. For information on that option, click here. | 0.800259 | 3.206739 |
The spacecraft New Horizons is on schedule to get a good view of Pluto on July 14th 2015.
We should soon have some measurements that will help determine how much of the icy planet is made up of water. On board New Horizons are instruments like Ralph, Alice, Rex, and Lorri. The requirements for these devices are that they need to be small, lightweight, powerful and robust, which sounds a lot like the specifications we desire for our field instruments on earth. There will be trickle down of these technologies for visible and infrared spectrometry and thermal mapping; UV spectrometry; Passive radiometry; and reconnaissance imaging into devices that will enable us to measure more parameters with greater reliability and resolution than ever before in our own watersheds.
There is a lot of interest in measuring water in space.
For one thing, water is the best predictor for the evolution of anything that we would recognize as life that there is. Furthermore, if we do eventually need to abandon our planet sometime in the future (say, because a big lump of space ice is on a collision course) we might want to stop by and replenish our supply 9 years into our journey (i.e. the time it took New Horizons to reach Pluto).
On board the International Space Station (ISS), astronauts have been recycling all of their water for many years with about 93% efficiency.
This seems pretty good but if you are losing 7% per cycle it won’t take too long before you might need to re-fresh the system with clean water, which on a long mission might mean stopping on Europa (a moon of Jupiter with about 3x as much water as there is on earth) or Pluto on your way out of the solar system.
Emerging technology for water recycling is already part of an integrated water management program in Singapore which includes rainwater capture, desalination and NEWater recycled water. NEWater is planned to meet up to 55% of Singapore’s future water demand. In a water-stressed future, it may be that we will only need to source water from the environment to offset the inefficiency in our water recycling program. In essence, we are already doing that but we currently need to supplement a recycling efficiency that is near 0%. Singapore’s current efficiency of 30% and the ISS efficiency of 93% are clear indications that we can do better.
Knowing how much water in our own watershed is important.
It is also interesting to know how much water there is 7.5 billion kilometers away. The technology for measurement is different, for now, but that is changing. If we can use our knowledge of water on earth to manage it a bit better, we may be able postpone the date that we need to leave the planet to take advantage of what we are learning about water in space.
Photo credit: NASA | “Recent Measurements of Pluto and Charon Obtained by New Horizons – A view of Pluto and Charon as they would appear if placed slightly above Earth’s surface and viewed from a great distance.” | 0.817599 | 3.445321 |
Earth has a lot of water – over 70% of the planet is below sea level. Less than 3% fresh water – almost all of that hiding as groundwater or frozen glaciers and ice-caps. Earth commands a orbital sweet spot around the sun – not too far, not too close, but just right to set us apart with liquid surface water. Water responsible for another unique distinction – plate tectonics. Water lubricates continental plates, facilitating constant bump and grind across our molten outer core. Movement responsible for mountain ranges, weather patterns and life as we know it.
Not often pondered outside quality, supply and demand – our most basic element is taken for granted. Understanding frozen objects litter the universe doesn’t often translate to consideration of how we ended up with all that water.
A study led by Ilsedore Cleeves, an Astrochemist from the University of Michigan Ann Arbor, indicates much of our water was present before the sun formed – more importantly 30-50% of Earth’s water not only escaped heat,radiation, and vaporization when the sun booted up, some 4.6 billion years ago – it prevailed despite those conditions. When a star first “lights up”, the surrounding cosmic cloud (imagine a chaotic jumble of cosmic dust particles and ice) it’s subjected to intense heat and radiation – vaporizing ice, and separating some water molecules into oxygen and hydrogen.
Science could only speculate as to how much water survived this bombardment – in other words, what might have remained as a “universal ingredient” in planet formation. Of particular interest, the study of two very different waters – regular old water and heavy water. Heavy water contains an element called Deuterium or heavy hydrogen – Deuterium rich water (identified as having a hydrogen isotope containing a neutron in addition to proton in the nucleus) is the product of substantial exposure to cosmic radiation.
Cleeves led researchers in creating a “planetary disk” – essentially a laboratory mock up of what happened to ice and water when the sun “lit” up. How much heat, direct solar radiation, and distance traveled by outside cosmic radiation were needed to account for measurable heavy water in our solar system. Their conclusion, published Sept. 26 in the journal Science – water and heavy water didn’t add up. A whole lot of water – perhaps as high as 50% came from icy interstellar space, millions of years before our sun got down to business.
“Our findings show that a significant fraction of our solar system’s water, the most-fundamental ingredient to fostering life, is older than the sun, which indicates that abundant, organic-rich interstellar ices should probably be found in all young planetary systems.” – Conel Alexander, research team member from the Carnegie Institute of Science.
Ponder that statement a moment – “abundant, organic-rich interstellar ices should probably be found in all young planetary systems” – that is so cool. | 0.853847 | 3.822489 |
On Wednesday, a team of astronomers from University College London announced that they detected water vapor in the atmosphere of a “ super-Earth” planet outside our own solar system. This is the first time water has been detected in the atmosphere of an exoplanet that is not a gas giant, which the researchers say makes it the most habitable exoplanet currently known. The planet, known by the catchy name K2-18b, is 110 light years away and orbits a red dwarf star about half the size of the sun. The planet is twice the size of Earth, eight times as massive, and orbits its host star once every 33 days.
“This is the only planet outside the solar system that has the correct temperature to support water and has an atmosphere that has water in it, making this planet the best candidate for habitability that we know right now,” says Angelos Tsiaras, an astronomer at University College London and the lead author of the study published today in Nature Astronomy.
A planet’s atmosphere holds many tantalizing clues. It can help determine if there are oceans on the surface, or if there’s a surface at all. It can tell you about a planet’s structure and evolution. And it can reveal whether a planet is capable of sustaining life. In this case, the data suggests that K2-18b either has a dense rocky core and a thick atmosphere, like Neptune, or is covered in a planet-wide ocean.
The detection of water vapor in the atmosphere of K2-18b brings some clarity to this exoplanet, but like any big discovery, the data raised more questions than it answered. For example, the researchers developed three models that fit the observational data and led to wildly different estimates of atmospheric water. In one model, the planet has a hydrogen-rich atmosphere with a lot of water and nothing else. Another had a lot of hydrogen and nitrogen, and very little water. The third model had a bit of water floating around in the upper atmosphere, but a lot of high-altitude clouds that obscured any water that may have been lower in the atmosphere. So how much water is in the atmosphere of K2-18b? According to the models, it could be anywhere between 0.01 percent to 50 percent of the atmosphere.
To detect K2-18b’s vapor, astronomers used a custom algorithm to analyze data that the Hubble Space Telescope collected in 2016 and 2017. By observing how the light from an exoplanet’s host star changes as the planet passes in front of it, they can pick up signatures of its atmosphere. Different atmospheric molecules absorb different amounts of light, and water in particular produces a strong signal, even if it’s present in only small amounts.
But there are limitations. The Hubble camera used to study K2-18b can detect wavelengths associated with water, but not all other molecules. It can see water in the atmosphere and little else, making it a bit like a photographer taking pictures in one color. To learn how much water vapor is in the atmosphere, or what it’s like on the surface, you need access to a broader spectrum of wavelengths.
The UCL astronomers used Hubble data collected by a group of researchers led by Björn Benneke, an astronomer at the University of Montreal’s Institute for Research on Exoplanets. Hubble data becomes public after a year, and although Benneke says his team has been analyzing K2-18b for nearly three years and originally commissioned the observation, the UCL team swooped in on the data and published its own analysis first. | 0.845435 | 3.930492 |
Crescent ♈ Aries
Moon phase on 6 June 2010 Sunday is Waning Crescent, 23 days old Moon is in Aries.Share this page: twitter facebook linkedin
Previous main lunar phase is the Last Quarter before 1 day on 4 June 2010 at 22:13.
Moon rises after midnight to early morning and sets in the afternoon. It is visible in the early morning low to the east.
Moon is passing first ∠3° of ♈ Aries tropical zodiac sector.
Lunar disc appears visually 5.7% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1787" and ∠1891".
Next Full Moon is the Strawberry Moon of June 2010 after 19 days on 26 June 2010 at 11:30.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 23 days old. Earth's natural satellite is moving from the second to the final part of current synodic month. This is lunation 128 of Meeus index or 1081 from Brown series.
Length of current 128 lunation is 29 days, 10 hours and 10 minutes. It is 1 hour and 44 minutes longer than next lunation 129 length.
Length of current synodic month is 2 hours and 34 minutes shorter than the mean length of synodic month, but it is still 3 hours and 35 minutes longer, compared to 21st century shortest.
This lunation true anomaly is ∠282.4°. At the beginning of next synodic month true anomaly will be ∠311.3°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
2 days after point of apogee on 3 June 2010 at 16:50 in ♒ Aquarius. The lunar orbit is getting closer, while the Moon is moving inward the Earth. It will keep this direction for the next 9 days, until it get to the point of next perigee on 15 June 2010 at 14:54 in ♋ Cancer.
Moon is 401 208 km (249 299 mi) away from Earth on this date. Moon moves closer next 9 days until perigee, when Earth-Moon distance will reach 365 937 km (227 383 mi).
6 days after its ascending node on 30 May 2010 at 18:07 in ♑ Capricorn, the Moon is following the northern part of its orbit for the next 7 days, until it will cross the ecliptic from North to South in descending node on 13 June 2010 at 21:54 in ♋ Cancer.
6 days after beginning of current draconic month in ♑ Capricorn, the Moon is moving from the beginning to the first part of it.
8 days after previous South standstill on 28 May 2010 at 22:09 in ♐ Sagittarius, when Moon has reached southern declination of ∠-25.029°. Next 5 days the lunar orbit moves northward to face North declination of ∠25.030° in the next northern standstill on 12 June 2010 at 07:06 in ♊ Gemini.
After 5 days on 12 June 2010 at 11:15 in ♊ Gemini, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.1085 |
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