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The Circular Lunisolar Calendar for 2014 was designed with a double purpose:
● to visualize the circular nature of time, according to which we live an eternal cosmic process on-helix basis rather than a linear path from a defined beginning to a defined ending.
● to bring out the role of the Moon in our existence in general and of course in our daily lives. The months of international -global trading- or «Gregorian» calendar express only arbitrary subdivisions of the solar cycle’s duration (1 year). The lunar synodic month is the cycle of time that directly reflects natural time. Time as defined by the movement of celestial bodies.
Besides, almost all of the ancient traditions emit the circularity of the cosmos and use lunisolar calendars, as well as do most of today's traditions too.
Circular Lunisolar Calendar consist of 9 full colour printed cards on both sides (18 card sides), into a frame made of microwelle cardboard, laminated with silver coloured paper. (See at explanatory photos how to handle insertion and extraction of the cards into the frame easily.)
13 of those card sides are illustrated by 13 Synodic lunar months full of data: New moon and Full moon precised time, Moon’s age for every single day, date and name of conventional (Gregorian calendar's) international month, Moon’s and Sun’s Ingress Time, Eclipses, Equinoxes, Solstices.
Some of the festivals of four traditions (Ancient Hellene’s, Hindu’s Christian’s and Buddhist’s) that measure time with lunisolar calendars are also noted. Asterisks marking the dates for each tradition are stained uniquely, and at the "hidden" part of every card the names of holidays and their time determination can be found. The important dates for each tradition are typically set according to the phase of the moon in relation to the season of the solar year.
Essentially, by their time placement, they mark the Sun’s and Moon’s circles. (See at explanatory photos a typical card side with all above illustrated data explained)
As it regards the eclipses, you will find a special card, illustrated to show the places they will be visible from.
Finally, you can find Synoptic Circular Lunisolar Calendar, where the lunar and Earth orbits are depicted, and exact time for all New and Full Moon of every Synodic Lunar Month are indicated. (See at explanatory photos)
Circular Lunisolar Calendar's 2014 Presentation (video)
March 20th 2014 - Spring Equinox - Athens, Greece - (Greek language) | 0.804893 | 3.606269 |
The sky is full of wonderful deep-sky objects to observe and photograph, but the variety of these can also be overwhelming. Let’s have a look at the main types of DSO!
First of all, in astronomy and astrophotography alike, a distinction is made between Solar System Objects and Deep Sky Objects. The main reason is that these are very different kind of targets, and they generally require a slightly different type of equipment to be observed and photographed.
Deep-sky objects represent anything that is alien to our solar system, such as distant stars, galaxies and nebulae. On the other hand, Solar System Objects include the Sun, the Moon and all the planets, but also comets and asteroids orbiting the Sun.
1. Galaxies (and Galaxy Clusters)
Galaxies are extremely big systems, and are actually the only type of deep-sky objects located outside the Milky Way. They host billions of stars, as well as nebulae and even black holes…
In the observable universe, scientists estimate the number of galaxies to be between 100 and 200 billions.Some of these are regrouped in clusters. But that is very hard to estimate, and the light that our telescopes receive, is sometimes billion years old… So who knows how many of them there are today, and what happened to them while the light they emit was reaching us?
Galaxies come in various sizes and shapes, and they actually work like a giant solar system. The billions of objects contained in a galaxy are orbiting its core, obeying the rules of gravity. Today, scientists believe that the core of some galaxies (including our galaxy, the Milky Way) contains a supermassive black hole, something so dense and heavy, that the whole galaxy would be orbiting it.
Evidence suggests that galaxies were formed by the action gravity, bigger galaxies attracting and eventually merging with smaller galaxies. These galactic collisions can be observed and photographed, like the famous Whirlpool Galaxy. The observation of these galaxies (and a phenomenon called red shift) also helped demonstrate that the universe is expanding.
From the Earth, the closest and biggest galaxy that can be photographed is the Andromeda Galaxy. And it will be easier to do so in the future: in a few billion years, the Andromeda will collide with our own galaxy, the Milky Way, and they’ll both create a new structure. I can’t imaging what a show that would be from the Earth!
In our skies, the Andromeda Galaxy is 4 to 5 times wider than the Moon… And, sadly, much dimmer. But still bright enough to take amazing pictures with standard equipment!
2. Star Clusters
Star clusters are groups of stars, held together by the gravitational force they exert on each other. There are two types of clusters:
- Globular clusters, which can be made of up to about a million stars.
- Open clusters, much smaller groups (up to about a hundred stars) but also much younger. The Pleiades are an open cluster, and can easily be spotted in the winter skies as a bright and compact group of stars.
Nebulae are probably the most beautiful deep-sky objects you can ever photograph. It’s difficult not to be amazed by the wonderful nebulae photographed by the Hubble Space Telescope! They are very colorful objects, and come in various shapes and sizes. Interestingly, some of these nebulae are the birthplace of our stars.
The term nebula comes from the Latin for cloud. Until recently, they were mysterious objects, and the term nebula actually included some galaxies and star clusters as well (i.e. anything diffused, cloudy).
Today, however, we know a bit more about these interstellar clouds. Scientists identified different types and sub-types of nebulae:
- Emission Nebulae
- “Standard” Emission Nebula (e.g. Ha region)
- Reflection Nebula
- Planetary Nebulae
- Supernova Remnants
- Absorption Nebulae (or Dark Nebula)
To photograph a nebula, a simple camera is enough. However, you can get much better results with a modified camera (especially for emission nebulae, mostly red), as well as with dedicated filters (e.g. Ha and OIII).
3. Emission Nebula
An emission nebula is a giant cloud of ionized gas and particles, glowing due to its proximity with one or several young and very hot stars.
The energy emitted by these nearby stars ionizes the atoms of gas, which in turn emit photons and produce a colored glow. The color of such nebula mainly depends on its composition:
- Hydrogen alpha (Ha) produces red, and is usually the most present element (about 90%)
- Hydrogen beta (Hb) produces blue
- Oxygen III (OIII) produces green
- Sulfur II (SII) produces red as well
4. Reflection Nebula
Reflection nebulae are different. They also reflect the light of nearby stars, but these stars aren’t hot enough to ionize the gas surrounding them (usually because the nearby stars are in formation).
Instead, we witness a phenomenon called light scattering: the light emitted by the nearby stars, is reflected by the dust and particles in the nebula. Therefore, acting like a mirror, this reflected light is very similar to that emitted by the nearby stars.
However, the amount of light being scattered depends on the wavelength: short ones (blue) are more scattered than long ones (red). This is the reason
why reflection nebulae are most of the time blue, but also why our sky looks blue!
The Pleiades star cluster is a famous reflection nebula. You can clearly see on this picture that the dust clouds near the main stars are blueish, while the rest of the clouds, further away, are much darker and grayer.
A reflection nebula is often seen together with an emission nebula, in which case they form what scientists call a diffuse nebula. The Trifid Nebula is an amazing object, as it contains an emission nebula (red) and a reflection nebula (blue), but also some absorption nebulae.
5. Supernova Remnant
A supernova remnant is another type of emission nebula. Within a star, there’s a constant battle between nuclear reactions (pushing) and the star’s own gravity (pulling). During most of the star’s life, it’s a rather balanced fight and the star is in a stable state.
Eventually, though, the star will run out of combustible. When this happens, there can be different outcomes, depending on the characteristics of the star (type, size, mass…). But sometimes, when the nuclear reactions cease, the gravity takes over and the star start collapsing on itself, before releasing in a huge explosion (a supernova) the gas contained in the outer layers (mostly hydrogen).
The Crab Nebula is an example of a very young supernova remnant. It is believed that the explosion took place in the 11th century, because it was observed and recorded by astronomers in China and Iraq.
6. Planetary Nebula
These nebulae have actually nothing to do with planets! They were named planetary nebulae, because the first observers believed the core was actually a planet.
Planetary nebulae have a lot in common with supernova remnants: they are both created when a star dies and collapses; they are both made of ionized gas, ejected by the star; and they are both hot enough to make this ionized gaz shells glow.
The key difference, however, is that for a planetary nebula, the star doesn’t explode in a giant supernova. They indeed look less chaotic. A supernova remnant is also much hotter and emit X-rays.
7. Dark Nebula
Dark nebulae are most peculiar objects, because they’re… dark. Unlike other observable deep-sky objects, they don’t emit nor reflect any light. Thus the name absorption nebula.
A dark nebula is a very dense cloud of interstellar dust, so dense in fact, that light cannot penetrate it. Any star, galaxy or nebula located behind that cloud of dust, won’t be visible.
A very famous example is the Horsehead Nebula. Located in the constellation of Orion, this dark cloud has the shape of a horse’s head, which contrasts with the red background of the emission nebula behind.
Other absorption nebulae can be seen in our own galaxy, the Milky Way, where they form noticeable dark patches.
- Helix Nebula: NASA, ESA, and C.R. O’Dell (Vanderbilt University)
- Cygnus Nebula: NASA, ESA and J. Hester (ASU)
- Veil Nebula: Ken Crowford
- Messier 15: NASA/ESA
- Messier 78:
ESO/APEX (MPIfR/ESO/OSO)/T. Stanke et al./Igor Chekalin/Digitized Sky Survey 2 | 0.830285 | 3.718563 |
New analyses of the rings reveal how and when they were made, from what and whether they’ll last.
Many dream of what they would do had they a time machine. Some would travel 100 million years back in time, when dinosaurs roamed the Earth. Not many, though, would think of taking a telescope with them, and if, having done so, observe Saturn and its rings.
Whether our time-traveling astronomer would be able to observe Saturn’s rings is debatable. Have the rings, in some shape or form, existed since the beginnings of the solar system, 4.6 billion years ago, or are they a more recent addition? Had the rings even formed when the Chicxulub asteroid wiped out the dinosaurs?
I am a space scientist with a passion for teaching physics and astronomy, and Saturn’s rings have always fascinated me as they tell the story of how the eyes of humanity were opened to the wonders of our solar system and the cosmos.
Our View of Saturn Evolves
When Galileo first observed Saturn through his telescope in 1610, he was still basking in the fame of discovering the four moons of Jupiter. But Saturn perplexed him. Peering at the planet through his telescope, it first looked to him as a planet with two very large moons, then as a lone planet, and then again through his newer telescope, in 1616, as a planet with arms or handles.
Four decades later, Giovanni Cassini first suggested that Saturn was a ringed planet, and what Galileo had seen were different views of Saturn’s rings. Because of the 27 degrees in the tilt of Saturn’s rotation axis relative to the plane of its orbit, the rings appear to tilt toward and away from Earth with the 29-year cycle of Saturn’s revolution about the Sun, giving humanity an ever-changing view of the rings.
But what were the rings made of? Were they solid disks as some suggested? Or were they made up of smaller particles? As more structure became apparent in the rings, as more gaps were found, and as the motion of the rings about Saturn was observed, astronomers realized that the rings were not solid, and were perhaps made up of a large number of moonlets, or small moons. At the same time, estimates for the thickness of the rings went from Sir William Herschel’s 300 miles in 1789, to Audouin Dollfus’ much more precise estimate of less than two miles in 1966.
Astronomers understanding of the rings changed dramatically with the Pioneer 11 and twin Voyager missions to Saturn. Voyager’s now famous photograph of the rings, backlit by the Sun, showed for the first time that what appeared as the vast A, B and C rings in fact comprised millions of smaller ringlets.
The Cassini mission to Saturn, having spent over a decade orbiting the ringed giant, gave planetary scientists even more spectacular and surprising views. The magnificent ring system of Saturn is between 10 meters and one kilometer thick. The combined mass of its particles, which are 99.8% ice and most of which are less than one meter in size, is about 16 quadrillion tons, less than 0.02% the mass of Earth’s Moon, and less than half the mass of Saturn’s moon Mimas. This has led some scientists to speculate whether the rings are a result of the breakup of one of Saturn’s moons or the capture and breakup of a stray comet.
The Dynamic Rings
In the four centuries since the invention of the telescope, rings have also been discovered around Jupiter, Uranus and Neptune, the giant planets of our solar system. The reason why the giant planets are adorned with rings and Earth and the other rocky planets are not was first proposed by Eduard Roche, a French astronomer in 1849.
A moon and its planet are always in a gravitational dance. Earth’s moon, by pulling on opposite sides of the Earth, causes the ocean tides. Tidal forces also affect planetary moons. If a moon ventures too close to a planet, these forces can overcome the gravitational “glue” holding the moon together and tear it apart. This causes the moon to break up and spread along its original orbit, forming a ring.
The Roche limit, the minimum safe distance for a moon’s orbit, is approximately 2.5 times the planet’s radius from the planet’s center. For enormous Saturn, this is a distance of 87,000 kilometers above its cloud tops and matches the location of Saturn’s outer F ring. For Earth, this distance is less than 10,000 kilometers above its surface. An asteroid or comet would have to venture very close to the Earth to be torn apart by tidal forces and form a ring around the Earth. Our own Moon is a very safe 380,000 kilometers away.
The thinness of planetary rings is caused by their ever-changing nature. A ring particle whose orbit is tilted with respect to the rest of the ring will eventually collide with other ring particles. In doing so, it will lose energy and settle into the plane of the ring. Over millions of years, all such errant particles either fall away or get in line, leaving only the very thin ring system people observe today.
During the last year of its mission, the Cassini spacecraft dived repeatedly through the 7,000 kilometer gap between the clouds of Saturn and its inner rings. These unprecedented observations made one fact very clear: The rings are constantly changing. Individual particles in the rings are continually jostled by each other. Ring particles are steadily raining down onto Saturn.
The shepherd moons Pan, Daphnis, Atlas, Pandora and Prometheus, measuring between eight and 130 kilometers across, quite literally shepherd the ring particles, keeping them in their present orbits. Density waves, caused by the motion of shepherd moons within the rings, jostle and reshape the rings. Small moonlets are forming from ring particles that coalesce together. All this indicates that the rings are ephemeral. Every second up to 40 tons of ice from the rings rain down on Saturn’s atmosphere. That means the rings may last only several tens to hundreds of millions of years.
Could a time-traveling astronomer have seen the rings 100 million years ago? One indicator for the age of the rings is their dustiness. Objects exposed to the dust permeating our solar system for long periods of time grow dustier and darker.
Saturn’s rings are extremely bright and dust-free, seeming to indicate that they formed anywhere from 10 to 100 million years ago, if astronomers’ understanding of how icy particles gather dust is correct. One thing is for certain. The rings our time-traveling astronaut would have seen would have looked very different from the way they do today. | 0.939581 | 3.944782 |
With more than two years of measurements by ESA’s Swarm satellite trio, changes in the strength of Earth's magnetic field are being mapped in detail.
Launched at the end of 2013, Swarm is measuring and untangling the different magnetic signals from Earth’s core, mantle, crust, oceans, ionosphere and magnetosphere – an undertaking that will take several years to complete.
Although invisible, the magnetic field and electric currents in and around Earth generate complex forces that have immeasurable effects on our everyday lives.
The field can be thought of as a huge bubble, protecting us from cosmic radiation and electrically charged atomic particles that bombard Earth in solar winds. However, it is in a permanent state of flux.
Presented at this week’s Living Planet Symposium, new results from the constellation of Swarm satellites show where our protective field is weakening and strengthening, and importantly how fast these changes are taking place.
The animation above shows the strength of Earth's magnetic field and how it changed between 1999 and May 2016.
Blue depicts where the field is weak and red shows regions where it is strong. As well as recent data from the Swarm constellation, information from the CHAMP and Ørsted satellites were also used to create the map.
It shows clearly that the field has weakened by about 3.5% at high latitudes over North America, while it has strengthened about 2% over Asia. The region where the field is at its weakest – the South Atlantic Anomaly – has moved steadily westward and weakened further by about 2%.
In addition, the magnetic north pole is wandering east, towards Asia.
The second animation shows the rate of change in Earth’s magnetic field between 2000 and 2015. Regions where changes in the field slowed are shown in blue while red shows where changes speeded up.
For example, changes in the field have slowed near South Africa, but have changed faster over Asia.
The magnetic field is thought to be produced largely by an ocean of molten, swirling liquid iron that makes up our planet’s outer core, 3000 km under our feet. Acting like the spinning conductor in a bicycle dynamo, it generates electrical currents and thus the continuously changing electromagnetic field.
It is thought that accelerations in field strength are related to changes in how this liquid iron flows and oscillates in the outer core.
Chris Finlay, senior scientist at DTU Space in Denmark, said, “Swarm data are now enabling us to map detailed changes in Earth's magnetic field, not just at Earth's surface but also down at the edge of its source region in the core.
“Unexpectedly, we are finding rapid localised field changes that seem to be a result of accelerations of liquid metal flowing within the core.”
Rune Floberghagen, ESA’s Swarm mission manager, added, “Two and a half years after the mission was launched it is great to see that Swarm is mapping the magnetic field and its variations with phenomenal precision.
“The quality of the data is truly excellent, and this paves the way for a profusion of scientific applications as the data continue to be exploited.”
It is clear that ESA’s innovative Swarm mission is providing new insights into our changing magnetic field. Further results are expected to lead to new information on many natural processes, from those occurring deep inside the planet to weather in space caused by solar activity.
In turn, this information will certainly yield a better understanding of why the magnetic field is weakening in some places, and globally. | 0.855275 | 3.679594 |
Prof Benjamin Stappers, Jodrell Bank - University of Manchester
In 2007 Astronomers discovered a very bright burst of radio emission which lasted just a few milliseconds which originated far outside of our own galaxy. The extreme brightness and the very short duration indicate that the source must be highly energetic and mostly likely associated with a black hole or neutron star. Another possibility is that they are caused by some cataclysmic event, like the collapse of a neutron star to form a black hole or the merger of two neutron stars. As these bursts travel great distances through space they are potentially great probes of the material and space between us and their origin helping us to understand more about the missing mass and energy in the Universe. There are now dozens of these bursts known and the race is on to find many more with new and existing telescopes around the world. I will discuss some of the history of FRBs, our current understanding, and look forward to the future including possibilities for South Africa’s very own MeerKAT telescope. | 0.817646 | 3.110759 |
A powerful new radio telescope will improve our understanding of galaxy formation and evolution, and other key questions in astrophysics, says Fernando Camilo, on behalf of the MeerKAT team.
After a decade in the works, South Africa’s MeerKAT telescope (Fig. 1), a precursor to the Square Kilometre Array (SKA) mid-frequency telescope, is beginning science operations. MeerKAT is a radio interferometer located in the semi-arid and sparsely populated Karoo region of the Northern Cape. The array consists of 64 antennas 13.5 m in diameter located on baselines of up to 8 km.
The distribution of the antennas, with three quarters of them located within a 1-km-diameter core, makes MeerKAT particularly suited to a variety of pulsar and neutral hydrogen studies. Several of the selected large survey projects (LSPs), which will use two thirds of the available observing time within five years, will address key questions related to galaxy formation and evolution. For instance, the unique combination of column density sensitivity and angular resolution will make MeerKAT a powerful probe for studying accretion onto galaxies in the nearby Universe. Projects will investigate the range of conditions from star-forming disks to low-density gas in dark matter haloes in isolated galaxies, and will examine how galaxies interact within rich clusters, while seeking to detect the cosmic web. Further afield, the 21-cm line of neutral hydrogen will be used to investigate the properties and evolution of galaxies across two thirds of cosmic time.
Although optimized for particular applications, MeerKAT is an extremely sensitive general-purpose radio telescope. The dishes are of a highly efficient offset Gregorian design, with up to four receiver systems positioned on a turret near the sub-reflector, without compromising the clean optical path. Three cryogenic receivers are currently being installed: L band (covering 900–1,670 MHz), UHF (580–1,015 MHz) and S band (1.75–3.5 GHz; provided by the Max Planck Institute for Radio Astronomy). The measured sensitivity of one 13.5-m MeerKAT antenna at L band is comparable to that of a 25-m Jansky Very Large Array antenna, with a much larger field of view.
The radio-frequency voltages for each of two linear polarizations are digitized in a shielded package just 1 m behind the receivers. The samples are then transmitted via buried optical fibre to the Karoo Array Processor Building (KAPB), located ~10 km away. There, the MeerKAT FX/B correlator/beamformer processes the 2 Tbps of data arriving from 64 dishes in real time. The correlator is based on the CASPER (Collaboration for Astronomy Signal Processing and Electronics Research) architecture, using Ethernet switches to handle data transfer between processing nodes. For MeerKAT, the processing nodes consist of SKARAB (SKA Reconfigurable Application Board) boards populated with field-programmable gate arrays, developed at SKA South Africa.
The flexibility of the MeerKAT architecture enables the deployment of multiple guest instruments that can subscribe to telescope data streams and simultaneously process them in a bespoke fashion tuned to each specific scientific requirement. In this way, for instance, while one LSP investigates the evolution of the cosmological star-formation rate density (through a continuum survey of selected fields), another team searches for fast radio bursts lasting a few milliseconds (which may be precisely localized because the back-end forms hundreds of beams tiling the large primary telescope beam), while yet another group searches for artificial signals from extraterrestrial sources.
The MeerKAT science data processor receives up to 300 Gbps from the correlator, which it averages in real time after applying appropriate flagging and calibration solutions. The resulting ~10 Gbps streams are archived, and further processed through imaging pipelines to produce ‘spectral cubes’: maps of sky brightness as a function of frequency. The scale of the computational and storage challenge is significant, with 1015 floating-point operations per second of computing power deployed at the KAPB, and 40 PB of storage at the Centre for High Performance Computing in Cape Town, where the permanent MeerKAT archive resides. Efficiency in both power and cost has been the dominant driving factor behind these solutions. For instance, careful specification, in-house integration and co-design with the software stack have yielded a massive-scale, high-performance storage cluster for a fifth of the cost of comparable commercial options.
MeerKAT is a South African-funded project, largely designed and built in South Africa. It is the result of an integrated plan that included careful consideration of multiple design options, development of technology demonstrators, training and investment in people through a human capital development programme and cooperation with industrial partners, and support from a wide variety of national stakeholders. First light occurred in 2016 using 16 antennas; the first science results were published in April 2018 (F. Camilo et al., Astrophys. J. 856, 180; 2018); and data collection has begun for the first LSPs using 64 antennas. The first call for open time proposals, for one-third of the available observing time, is expected in late 2018. Eventually, MeerKAT will be integrated into the international SKA Phase 1 mid-frequency array.
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Cite this article
Camilo, F. African star joins the radio astronomy firmament. Nat Astron 2, 594 (2018). https://doi.org/10.1038/s41550-018-0516-y | 0.884859 | 3.867925 |
The best evidence yet for a liquid ocean buried under the surface of Saturn's moon Titan has been found, scientists report.
New observations show that Titan warps during the gravitational tides it experiences, suggesting an ocean sloshes under its outer shell. This ocean has long been theorized but never confirmed.
Titan is the biggest of the more than 60 known moons orbiting Saturn, and is larger than the planet Mercury. Scientists have long suspected that an ocean might lurk under Titan's surface, as well as under Jupiter's moons Ganymede, Callisto and Europa. Previous observations have shown that the entire surface of Titan appears to be sliding around like cheese over tomato sauce on a pizza.
"Liquid water elsewhere in the solar system is one of the main goals of planetary exploration for NASA," said study lead author Luciano Iess, a planetary geodesist at Università La Sapienza in Rome. "This discovery points to the fact that many satellites in the outer solar system hide large amounts of liquid water."
To get a glimpse into Titan's mysterious interior, scientists relied on NASA's Cassini spacecraft, which has orbited Saturn since 2004. They focused on the extraordinarily powerful tides the planet's gravitational pull causes its moons to experience — tides ferocious enough to have once ripped apart titanic chunks of ice to produce the world's rings. Titan itself faces tidal effects up to 400 times greater than our moon's draw on Earth.
By monitoring how Cassini's acceleration changed during six close flybys past Titan between 2006 and 2011, the researchers deduced the strength of the moon's gravity field. Since a body's gravity stems from its mass, these details helped reveal how matter is distributed within Titan and how this changed depending on how near or far the moon was from Saturn during its oval-shaped 16-day orbit around the planet.
The strong way in which Titan deformed in response to Saturn hints that the moon has quite a flexible interior. This adds evidence to suggestions that an ocean lies concealed beneath a relatively thin shell 60 miles (100 kilometers) or less thick.
"An ocean inside Titan was expected, but it was a matter of speculation — these measurements now essentially tell you for sure there is a subsurface ocean," Iess told SPACE.com.
It remains uncertain just how deep this ocean might be. "We cannot say if it is 10 kilometers (6 miles) or 100 kilometers (60 miles) or more," Iess said. "We only know that there is a liquid layer."
These hidden seas might be seasoned with the chemical ingredients of life, just as Titan's surface and atmosphere are. "Our measurements do not say anything about the existence of life on Titan, but there is a large inventory of organic molecules there, and there is water, so there are all the ingredients that may lead to life," Iess said.
Future analysis of Titan's tides could reveal more about the moon's history, Iess said, such as why its orbit is so oval-shaped — whether its orbit began that way, or was due to a cosmic impact with another body.
The scientists detailed their findings online today (June 28) in the journal Science. | 0.919848 | 3.919272 |
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The most massive faraway cluster of galaxies has been found, thanks to a fortuitous astrophysical alignment that helped astronomers detect the mammoth grouping.
The galaxy cluster, named IDCS J1426.5+3508, is located a staggering 10 billion light-years away from Earth, and researchers spotted the behemoth because its gravitational field is so strong that it is warping the light coming from a galaxy behind it. Galaxy clusters are the most massive structures in our universe, and are made up of hundreds to thousands of galaxies that are bound together by gravity.
"When I first saw it, I kept staring at it, thinking it would go away," study lead author Anthony Gonzalez, an astronomer at the University of Florida in Gainesville, said in a statement. "The galaxy behind the cluster is a typical run-of-the-mill galaxy with a lot of young stars, but the galaxy cluster in front of it is a whopper for that range. However, it's really the way that the two systems are lined up that makes the occurrence truly remarkable."
This fluke alignment created what's called a gravitational lens, which occurs when a massive object, such as a black hole or galaxy cluster, lies directly between an observer (or telescope), and a more distant target in the background.
The powerful gravitational force of the object in the foreground warps the light being emitted by the more distant target, bending and twisting it on its path to the telescope.
Gravitational lensing from the faraway galaxy has never been observed behind a cluster at such an enormous distance, the researchers said.
Since this galaxy cluster is so distant — 10 billion light-years away — it existed when the universe was only one-quarter of its present age. The universe is estimated to be roughly 13.7 billion years old. Current theories for how the universe evolved suggest that relatively few of these galaxy clusters were present when the universe was in its infancy, the researchers said. [The Universe: Big Bang to Now in 10 Easy Steps]
Still, finding this galaxy cluster represents a serendipitous astrophysical discovery in itself, since the astronomers were scanning only a small 9-square degree section of the sky. For comparison, if you extend your arm in front of you and hold up your index finger, you will be covering approximately 1 square degree of the sky with your finger, Gonzalez explained.
"So finding a massive cluster at that range that is also gravitationally lensing is a real long shot, even if you were looking at the whole sky," he said.
The astronomers originally found the galaxy cluster using NASA's infrared Spitzer Space Telescope, but evidence of the gravitational lensing was seen in images taken by the Hubble Space Telescope in 2010.
To follow up on this find, and to narrow down the cluster's mass and distance, the researchers used data from the Combined Array for Research in Millimeter-wave Astronomy (CARMA) radio telescope in the Inyo Mountains in California, and NASA's Chandra X-ray Observatory in space.
The discovery of a massive galaxy cluster at such a great distance, in a limited field of observation, could indicate that current models of clusters in the early universe may need to be reworked, Gonzalez said. But right now, it is too soon to tell.
"We just don't know," Gonzalez said. "We need to find more clusters at this range so that we can get more data. So far we only have one example to study."
The study's detailed findings are published in the July 10 issue of The Astrophysical Journal. | 0.845755 | 3.944032 |
Image credit: NASA/Crew of STS-132 (Public Domain)
One of the joys of a hot, summer evening for me is the opportunity to have a swim after the sun goes down, before hopping into bed. I always make sure that there are no outside lights shining from the house and, because we live in the countryside where there is virtually no light pollution, on a clear night it’s a great place for star-gazing.
The most awe-inspiring sight has to be the Milky Way, the luminescent band of light made up entirely of stars, clearly visible in the Andalucían night sky.
There are other cosmic masterpieces to be seen at certain times of the year when our planet Earth passes through bands of dust and debris that circle the Sun. We see these as meteor showers, and a perfect example is the Perseids (a prolific meteor shower associated with the comet Swift-Tuttle), which occurs around the 12th August each year. Once again, I will be floating in the pool, watching these tiny fragments of space dust hurtling into our atmosphere at enormous speed, before burning up, to provide magnificent celestial fireworks.
Much slower are our own Earth-launched satellites which drift lazily by. There are so many satellites circling the planet these days, that you can usually spot one within a few minutes. Their speed is deceptive though, because the satellites are very high, they actually have to maintain about 18,000 miles per hour to remain in orbit.
Image credit: STS-116 spacewalk 1 by NASA (Public Domain)
But the object I’m always fascinated to see tracking overhead is the International Space Station – a man-made habitable satellite which serves as a microgravity research laboratory.
Flying at 27500 kilometres per hour (that’s an average speed of 7.65 kilometres per second), the ISS maintains its orbit at an altitude of between 330 km and 435 km. With an approximate size of 110 x 70 x 20 metres, the International Space Station (ISS) reflects plenty of sunlight and is usually the second brightest object in the night sky (after the moon), so is easily visible with the naked eye.
Image credit: NASA Flickr CC
Just look at the amazing view from the ISS!
One of the six crew members aboard the International Space Station recorded the above amazing photograph of the entire Iberian Peninsula (Spain and Portugal) on July 26, 2014. Part of France can be seen at the top of the image and the Strait of Gibraltar is visible at bottom, with a very small portion of Morocco visible near the lower right corner.
I’d LOVE to take photos through this window!
Image credit: NASA STS130 cupola view (Public Domain)
How can you get a good view of the International Space Station as it passes overhead?
Well, the first thing you should do is try to get away from the light pollution of a town or city, on a clear night. If there is cloud cover you are unlikely to see anything.
The ISS looks like an incredibly bright, fast-moving star which can easily be mistaken for an aircraft. What distinguishes it from an aircraft is that it has no flashing lights. The light we see from the ISS is reflected sunlight, meaning that the best time to observe the craft is in the evening, not long after sunset or in the early morning, before sunrise.
The next thing you should know is that the ISS always passes overhead starting from a westerly part of the sky, but not always from the same point. It can be low on the horizon for some passes and very high for others.
Image credit: NASA STS-129 Zvezda sunrise
When can you observe the International Space Station from where you are?
To see the current position of the International Space Station click HERE. Once you click through to that page, not only can you see what the astronauts can see, you can also view the ground track of the next orbit of the ISS.
Next, you need to click HERE and at the top right of the upcoming page you will see a box that says “Your location” and underneath that the default location is shown as New York City.
Type YOUR location in the box, hit SEARCH and you’ll get something like the image below. (This is the image I found last night when I did the same thing – that’s why it shows Spain).
So now you can see a list of the next sighting opportunities for YOUR location (on the left of the page), with the green bars indicating the brightness of the ISS on its pass. The list contains all visible passes of the ISS during the next ten days. If you select a particular pass, you can get more information about it.
In the photo above, you can see that for my location in Cómpeta, Spain there was an ISS pass last night (Friday August 8th) at 9.44pm lasting 5 minutes and 29 seconds with 2 green bars for brightness. My next best chance to view the ISS is next Saturday night (16th August) at 11.19pm.
Let me know if you’ve ever seen the ISS. Do you watch for it regularly? I know I do! | 0.892348 | 3.211234 |
Another instrument on board the spacecraft known as the Advanced Small Analyzer for Neutrals (ASAN), will measure how solar wind - a flow of charged particles from the sun - interacts with the lunar surface.
The landing appears to have been accomplished without any major issues, however, and the Chinese lander and rover will be able to begin exploring the moon's far side, an environment astronauts and spacecraft have until today only seen from afar.
"Lunar rover Yutu-2 or Jade Rabbit-2, left the first-ever "footprint" from a human spacecraft on the far side of the moon late at night on Thursday, after it separated from the lander smoothly", state-run Xinhua news agency reported.
On top of this, 28 universities in China, all led by Chongqing University, will conduct experiments involving the cultivation of vegetables and flowers in airtight containers within the spacecraft.
We're looking forward to the treasure trove of data Chang'e-4 sends back, but the CNSA aren't stopping here - Chang'e-5 is scheduled to launch by 2020, with the aim of landing on the Moon and then returning to Earth. The first data from this instrument is expected to be available before February 11.
The lunar far side is often referred to as the "dark side", though "dark" in this case means "unseen" rather than "lacking light". "Probably after some years ordinary people like us can also travel up there to take a look", he said. There was very little news of the Chang'e 4 landing attempt before the official announcement it had been a success.
That satellite was successfully launched back in May, and has now been used to confirm the successful landing of Chang'e-4 in the Moon's South Pole-Aitken Basin, which measures around 2,500 km across and 13 km deep (1,550 and 8 mi).
In 2003, China became the third country to put a man in space with its own rocket after the former Soviet Union and the United States, and in 2017 it said it was preparing to send a person to the moon.
"It's an important milestone for China's space exploration", Wu Weiren, chief designer of the lunar exploration program, said, according to Xinhua.
But Fred Watson, who promotes Australia's astronomy endeavours as its astronomer-at-large, says the secrecy could simply be down to caution, similar to that shown by the Soviet Union in the early days of its competition with Nasa.
Ye Quanzhi says China has made efforts to be more open. "PR skills take time to develop but I think China will get there", he said.
The far side of the moon was first photographed in 1959, and missions from Europe, India, Russia and America in the last two decades have already mapped it. | 0.826323 | 3.11135 |
The Compton Legacy: A Quarter-century of Gamma-ray Science
Twenty-five years ago this week, NASA launched the Compton Gamma Ray Observatory, an astronomical satellite that transformed our knowledge of the high-energy sky. Over its nine-year lifetime, Compton produced the first-ever all-sky survey in gamma rays, the most energetic and penetrating form of light, discovered hundreds of new sources and unveiled a universe that was unexpectedly dynamic and diverse.
Compton's many findings included the discovery of a new class of galaxy powered by supermassive black holes, the surprising detection of gamma rays from thunderstorms on Earth, and the most persuasive evidence to date that gamma-ray bursts (GRBs) were the most distant and powerful explosions in the cosmos. Astronomers were so ecited by the initial results, it wasn't long before discussions turned to the need for another mission with improved instruments to get a better look, a trail that ultimately led to NASA's Fermi Gamma-ray Space Telescope.
Compton was launched April 5, 1991, on STS-37, the eighth flight of the space shuttle Atlantis. At the time, the 17-ton observatory was the heaviest astrophysical payload ever flown, a record not broken until the launch of NASA's Chandra X-ray Observatory and its rocket booster in 1999. The crew deployed the satellite, then known simply as the Gamma Ray Observatory, on April 7.
NASA soon renamed the satellite in honor of Arthur Holly Compton, an American physicist and Nobel laureate who discovered that high-energy light underwent a change in wavelength when it scattered off electrons and other charged particles. This process played a central role in gamma-ray detection techniques used in all of the observatory's instruments.
Compton was the second of NASA's Great Observatories, a series of ambitious astronomical satellites designed to explore different parts of the electromagnetic spectrum. The first launch of the program was the Hubble Space Telescope in 1990. Compton was followed by the Chandra X-ray Observatory in 1999 and the infrared-sensitive Spitzer Space Telescope in 2003. All of them remain operational today except Compton, which was deliberately deorbited in 2000. Its scientific legacy continues in Fermi, Swift and other space observatories exploring the universe's highest-energy light and the extreme phenomena producing it.
For a more detailed summary of Compton's key results, download this NASA brochure published in late 1990s.
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>> Neutron Star
>> Earth Science
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>> Sun-earth Interactions
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>> Solar Flares
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>> Gamma Ray Burst
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 22.214.171.124.0 | 0.813474 | 3.84666 |
GMOS spectrum of J0045+41 with all identified lines labeled.
Full resolution JPEG
This graphic shows the Chandra data (blue in inset) of the source known as LGGS J004527.30+413254.3 (J0045+41 for short) in the context of optical images of Andromeda from the Hubble Space Telescope. J0045+41 likely contains a pair of supermassive black holes in close orbit around each other, separated by only a few hundred times the distance between the Earth and the Sun. The estimated total mass of the black holes is about two hundred million times the mass of our Sun. Credits: X-ray: NASA/CXC/University of Washington/T. Dorn-Wallenstein et. al.; Optical: NASA, ESA, J. Dalcanton et. al. and R. Gendler.
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Gemini observations played a critical role in research by scientists at the University of Washington in their quest to identify an object which appears to be “photobombing” the Andromeda Galaxy. The researchers determined that rather than being a binary star system within the neighboring Andromeda Galaxy, as previously thought, the object is really a distant galaxy containing a supermassive black hole binary – a pair of black holes orbiting each other very closely within the galaxy’s core.
“The Gemini spectroscopic observations revealed the true nature of this puzzling object as a background galaxy with an active nucleus,” said Gemini’s Chief Scientist John Blakeslee. “Careful analysis of the extreme velocities seen in the spectra then led the team to suspect that the supermassive black hole in the galaxy’s center is actually a tightly bound binary.”
Observations by NASA’s Chandra X-ray Observatory first cast suspicion that things weren’t as simple as they appeared due to the intensity of the X-ray source.
The results are published in the November 20th issue of The Astrophysical Journal and described in the press release that follows from Chandra/NASA. Gemini Observatory is funded through an international partnership led by the U.S. National Science Foundation (NSF), with contributions from the Canadian National Research Council (NRC), the Brazilian Ministério da Ciência, Tecnologia e Inovação (MCTI), the Argentinian Ministerio de Ciencia, Technología e Innovación Productiva (MCTIP), Tecnologia e Inovação and the Chilean Comisión Nacional de Investigación Científica y Tecnológica (CONICYT - Chile).
Giant Black Hole Pair Photobombs Andromeda Galaxy
It seems like even black holes can’t resist the temptation to insert themselves unannounced into photographs. A cosmic photobomb found as a background object in images of the nearby Andromeda galaxy has revealed what could be the most tightly separated pair of supermassive black holes ever seen.
Astronomers made this remarkable discovery using X-ray data from NASA’s Chandra X-ray Observatory and optical data from ground-based telescopes, Gemini-North in Hawaii and the Palomar Transient Factory in California.
This unusual source, called LGGS J004527.30+413254.3 (J0045+41 for short), was seen in optical and X-ray images of Andromeda, also known as M31. Until recently, scientists thought J0045+41 was an object within M31, a large spiral galaxy located relatively nearby at a distance of about 2.5 million light years from Earth. The new data, however, revealed that J0045+41 was actually at a much greater distance, around 2.6 billion light years from Earth.
“We were looking for a special type of star in M31 and thought we had found one,” said Trevor Dorn-Wallenstein of the University of Washington in Seattle, WA, who led the paper describing this discovery. “We were surprised and excited to find something far stranger!”
Even more intriguing than the large distance of J0045+41 is that it likely contains a pair of giant black holes in close orbit around each other. The estimated total mass for these two supermassive black holes is about two hundred million times the mass of our Sun.
Previously, a different team of astronomers had seen periodic variations in the optical light from J0045+41, and, believing it to be a member of M31, classified it as a pair of stars that orbited around each other about once every 80 days.
The intensity of the X-ray source observed by Chandra revealed this original classification was incorrect. Rather, J0045+41 had to be either a binary system in M31 containing a neutron star or black hole that is pulling material from a companion — the sort of system Dorn-Wallenstein was originally searching for in M31 — or a much more massive and distant system that contains at least one rapidly growing supermassive black hole.
However, a spectrum from the Gemini-North telescope taken by the University of Washington team showed that J0045+41 must host at least one supermassive black hole and allowed the researchers to estimate the distance. The spectrum also provided possible evidence that a second black hole was present in J0045+41 and moving at a different velocity from the first, as expected if the two black holes are orbiting each other.
The team then used optical data from the Palomar Transient Factory to search for periodic variations in the light from J0045+41. They found several periods in J0045+41, including ones at about 80 and 320 days. The ratio between these periods matches that predicted by theoretical work on the dynamics of two giant black holes orbiting each other.
“This is the first time such strong evidence has been found for a pair of orbiting giant black holes,” said co-author Emily Levesque of the University of Washington.
The researchers estimate that the two putative black holes orbit each other with a separation of only a few hundred times the distance between the Earth and the Sun. This corresponds to less than one hundredth of a light year. By comparison, the nearest star to our Sun is about four light years away.
Such a system could be formed as a consequence of the merger, billions of years earlier, of two galaxies that each contained a supermassive black hole. At their current close separation, the two black holes are inevitably being drawn closer together as they emit gravitational waves.
“We're unable to pinpoint exactly how much mass each of these black holes contains,” said co-author John Ruan, also of the University of Washington. “Depending on that, we think this pair will collide and merge into one black hole in as little as 350 years or as much as 360,000 years.”
If J0045+41 indeed contains two closely orbiting black holes it will be emitting gravitational waves, however the signal would not be detectable with LIGO and Virgo. These ground-based facilities have detected the mergers of stellar-mass black holes weighing no more than about 60 Suns and, very recently, one between two neutron stars.
“Supermassive black hole mergers occur in slow motion compared to stellar-mass black holes”, said Dorn-Wallenstein. “The much slower changes in the gravitational waves from a system like J0045+41 can be best detected by a different type of gravitational wave facility called a Pulsar Timing Array.”
A paper describing this result was accepted for publication in The Astrophysical Journal and a preprint is available online. NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.
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A podcast about Gemini Observatory and its role in the Era of Multi-Messenger Astronomy. Featuring news related to multi-messenger astronomy (MMA), time-domain astronomy (TDA), our visiting instrument program, and more through interviews with astronomers, engineers, and staff both here at Gemini (North and South) and abroad. | 0.909013 | 3.482779 |
In the summer of 2012, the 1,592-pound space probe Voyager 1 became the first man-made object to exit our solar system. NASA had launched the probe in 1977; the multi-billion-mile trek to the edge of our solar system took 35 years. (Good thing we weren't waiting for it to bring sugar back.)
There were no humans aboard the spacecraft, only machines. But imagine if there had been: How would NASA pay them? How would they shop, manage their bank accounts, pay taxes, and communicate with people back on Earth? What if they wanted to set up the first Interstellar (Free) Trade Agreement? How would this new economy work?
Just a year after the Voyager took flight, Paul Krugman — the voicey, often funny, economist and New York Times columnist — came up with The Theory of Interstellar Trade to iron out the financial intricacies of settling space. It was "a serious analysis of a ridiculous subject, which is of course the opposite of what is usual in economics," he wrote. It's also what's so great about it.
Let's quickly fast-forward to 2015. Voyager is still our only venture beyond our home system to date, but we have made some considerable advances since Krugman first theorized an interstellar economy. We landed on a comet. We're inching closer to Jupiter and Pluto. We landed on Mars, multiple times. Yes, these missions were unmanned, but Elon Musk is hard set on colonizing Mars, and others agree that it isn't some hair-brained idea.
"Certainly, within the solar system, one of the big things that will happen within this century is that people will start living off the Earth," Seth Shostak, the director of the Search for Extraterrestrial Intelligence Research program, told me. "Even if they're just living in a rotating aluminum can, they still need to earn a living, so they're going to have to trade."
In other words, Krugman's "ridiculous" theory is looking less bonkers now.
He imagined a future where our space vehicles moved close to or at the speed of light — a Hyperloop for space, if you will. At such mind-bending speeds, space travelers would experience time differently than stationary Earthlings, Martians or Tranton-ites, the inhabitants of the imaginary planet Krugman describes in his paper. As a result of this time shift, interest rates — and the value of goods — wouldn't be the same for the senders and receivers. The elapsed time would feel shorter to the persons in motion. (Thanks, Relativity!) But even at light speed, the travel time would still be considerable, so the goods would need to be worth the wait. You wouldn't want to order the iPhone 82 when everyone on Earth was using the iPhone 3000 by the time it arrived.
The big question is how you would price your interstellar purchase and the costs of delivery. How do you compute the cost of a Galactic Lyft ride or an Amazon StarPrime delivery? The value will hinge partly on interest rates (or rates of depreciation), and time is an important variable here. And to recap, time isn't equal for the sender, receiver, and courier. For the courier, who's in motion, time is shorter, so if the value of the goods is depreciating, the messenger would have a bit of an advantage. So Krugman concludes, it's best to use stationary clocks on planets, since that's where the goods come from and are ultimately headed.
So, what if you had assets in two different galaxies? How would the space-haves figure out the worth of their Earthly home compared to the one in the galactic suburbs? "Competition will equalize the interest rates on the two planets," Krugman wrote, so it will be possible to fairly assess their values.
Krugman had some of the economics pretty well figured out by 1978. "From this point," he wrote, "the picture of the world — or, rather, of the universe — which emerges is not a lunatic vision; stellar, maybe, but not lunatic. Is space the Final Frontier of economics? Certainly this is only the first probe of the subject, but the possibilities are surely endless."
And he was right. Even with a Nobel Prize-winning economist on the case, gaps in the workings of our future interstellar economy remained. His work inspired others to take on things like interstellar finance and taxation. But these are the issues we haven't figured out yet:
Energy and time
It's going to take a lot of fuel to transport goods from one planet to the next. "I think the biggest problem is the energy cost of sending something back. The transportation costs will dwarf the value of the goods," said Shostak. Even with digital goods whizzing through space at the speed of light, the time you'd have to wait to get them would be astronomical. Given those two constraints, Shostak predicts that the "local" fad we have today will become a necessity in most space economies of the future. Truly interstellar societies can only exist when we crack the energy problem. Another incentive to invest in green technologies.
Language and culture
Once we make contact with other alien communities how will we communicate with them? Will we be able to understand their social cues? These questions apparently bothered Berry College's John Hickman, according to the Australian website Chartered Accountants:
“Absence of a common language and all of the shared meaning that goes with it would be the largest problem,” he says. “We have scant chance of solving the other problems of exchange until we overcome the language barrier. We don’t know how different intelligence produced by a distinct process of development would think, but the difficulty we face in understanding the minds of non-human animals, with which we share a biological evolution, suggests that it will be daunting.”
And what happens when linguistic and cultural differences naturally evolve between communities separated by such vast distances? After all, if communication only happens once every 10 years, the process of learning and relearning each other's slang and cultural norms could be endless. Constant contact — even if it's only on the interstellar internet — is imperative. Otherwise we're always going to be dependent on Microsoft's Interstellar Skype Translator, equipped with state-of-the-art AI that can learn and translate spoken and body language on the fly.
Communication issues aside, what will save us from this?: "Such [interstellar] exchange also threatens the release of new and dangerous memes," Hickman wrote in a paper. Without having read the entire thing (everything but the abstract is behind a paywall), I'm going to go out on a limb here and say that he probably means some kind of super viral virus, and not annoying-yet-super-shareable photos of Grumpy AlienCat.
Evolution might be our strongest ally here. When we initially make contact, it's probable that the space contagions we'd encounter wouldn't know what to do with us. This kind of thing happens on Earth too. That's why a lot of animal diseases don't affect us. It's only when we're in close proximity that our viruses and theirs start to adapt to their potential new hosts. And when they do, boom! You've got an outbreak because we have no immunity to these new maladies. So, it might take a while for Hickman's predictions to come through, which gives us time to start doing research into what alien viruses are most likely to make that leap. The we can start creating the vaccines we'd need. Oh! And an Intergalactic Centers for Disease Control and Prevention would probably be a good idea. I just hope anti-vaxxers aren't a thing in space.
Hickman also worried about having a common currency. How could we trade if we used dollars and aliens used SpaceCoin? We'd have to set up an exchange capable of taking into account fluctuations over time. After all, remittances and payments wouldn't just happen instantly. They could take months or even years to reach their final destination… yes, even with Bitcoin.
Alien Super AIs
Here on earth, moviemakers constantly bring us superintelligent robots eradicating the human race. But the Terminator might look like Rosie the Robot compared to what we encounter in the great beyond. Scientists like Shostak think that outside our blue planet, the dominant life forms are superintelligent robots. With the ones we cook up, we at least stand the chance of being able to pull the plug. After all, we built them, so we know how they work and how to break them. (Throw some water on the transistors that make up a 'bot brain, and it short-circuits.) Humans 1. Robots 0.
But what about these super-alien robots that Shostak talks about? What's their biology? We'd really have no clue about how they function or what they're capable of. So, the real robo-apocalypse might await us once we venture out of own solar system.
The solution might be kind of meta. Once we collect enough data on these super space AIs (hopefully from afar), we can create a super-big-data AI model to predict how we should interact with them and how best to defeat them. Take that, robots!
Futures Past is a weekly look at the technologies and science that imagined the future, wrong or right. If you've got a tip, email me at [email protected]. Brownie points if you're from the future.
Daniela Hernandez is a senior writer at Fusion. She likes science, robots, pugs, and coffee. | 0.851536 | 3.089161 |
Stargazers in the UK got a rare treat Tuesday morning after Venus, Jupiter and the moon appeared together in the dawn sky.
Shots of the spectacular conjunction were a big hit on social media, with excited users posting some astonishing photos.
While the two planets appeared even closer in the sky on January 22, perfect conditions in the UK Tuesday sparked great public interest.
On January 22, the conjunction "was too low in the sky to be easily seen in the UK, but across North America the planets could be seen in the South East of the sky from around 4am to 7am EST," said Anna Ross, an astronomer at the Royal Observatory in London.
These conjunctions are fairly common, said Leigh Fletcher, a Jupiter scientist at the University of Leicester in the UK.
The two planets will continue to move further apart, Fletcher told CNN via telephone, adding that Tuesday morning was great for stargazers.
"The weather has been ideal for us to take a look at what's going on," he added.
Researchers like Fletcher have spent the past few months waiting for Jupiter to re-emerge from behind the sun, and the recent photos are some of the first Earth-based observations of the planet since late last year, he said.
Over the next few months Jupiter will become even easier to see, said Fletcher, with the best view on June 10.
Jupiter is five times further from the sun than the Earth is, while Venus sits between the Earth and the sun -- about 75% as far from the sun as we are -- and is the brightest object in our night sky aside from the moon, according to NASA.
"Although it's smaller than Jupiter, Venus appears brighter because it's much closer to the sun," said Morgan Hollis of the Royal Astrological Society. "This means that more light hits it and can be reflected off to be visible from Earth."
And while there are 14 planetary conjunctions due in 2019, according to Hollis, the combination of the two planets and a bright moon made for some nice photographs on Tuesday morning.
In December 2018, Fletcher co-authored a study that identified a regular pattern of unusual meteorological events at Jupiter's equator.
The research, published in the journal Geophysical Research Letters, predicted that the thick, white clouds that are often observed at the equator would have disappeared when Jupiter re-emerged from behind the sun, and Fletcher says initial observations have confirmed their predictions.
Excitement is also building as NASA's Juno probe prepares for its next close encounter with Jupiter on February 12.
The probe was launched in 2011 and reached Jupiter in 2016.
Since then it has been sending back amazing images of the giant planet, and the February 12 flyby will give scientists a chance to see how conditions have changed, said Fletcher.
The conjunction of Venus and Jupiter is the latest space event in what has been an exciting year so far for astronomers.
Earlier this month, stargazers in most parts of the globe were able to catch a glimpse of a rare super blood wolf moon. This was a total lunar eclipse that happened at the same time as a supermoon -- when the moon is full and closest to Earth in orbit.
If you're interested in celestial events, keep an eye on the skies from April 19 to May 28, when the Eta Aquarid meteor shower will put on a spectacular show. | 0.891368 | 3.190928 |
These infrasonic waves were detected world-wide on traditional barographs as small air pressure fluctuations. Due to its low-frequency content, infrasound hardly experiences attenuation in the atmosphere and travels to thermospheric altitudes of over 100 km. In addition to seismology, infrasound was used to measure the occurrence of atmospheric nuclear tests and to estimate their yield (2). It was also in this period that the possibility to use infrasound as passive atmospheric probe started to be recognized( 3). This interest diminished after nuclear tests were confined to the subsurface under the Limited Test Ban Treaty (1963).
Recently, the study of infrasound is experiencing a renaissance as it was chosen as a verification technique for the Comprehensive Nuclear-Test-Ban Treaty (CTBT), that opened for signing in 1996 (4). Infrasound science currently concentrates on source identification and passive remote sensing of the upper atmosphere.
The construction of the largest radio-telescope in the world in the northern part of the Netherlands and neighbouring countries, the Low Frequency Array (LOFAR), opened the possibility to co-locate geophysical sensors and realize an efficient multi-sensor network. The KNMI, Delft University of Technology and TNO, all partners in LOFAR, make use of the advanced LOFAR infrastructure to build-up an infrasound and seismological research network. This network consists of a temporary 80 element high density array, a permanent 30 element microbarometer array with an aperture of 100 km and, at the same locations, a 20 to 30 element seismological component. Here, we present the scientific background, goals and first results.
Sound waves below 20 Hz are inaudible for the human ear. These sound waves are called infrasound. The lower limit of infrasound is controlled by the thickness of the atmosphere or of an atmospheric layer. For the troposphere, the acoustic cut-off period is roughly 5 minutes. For longer period waves gravity acts as restoring force, instead of the molecular relaxation for sound waves, and hence these are called gravity waves. These gravity waves propagate with typical wind speed velocities of 5 to 10 m/s. Infrasonic waves travel with the sound speed which is 340 m/s for air of 20°C. The amplitudes of infrasonic waves are small with respect to the ambient pressure and vary between milli-pascals (Pa) to tens of Pa.
The propagation of infrasound is controlled by the effective sound speed, which is a function of the temperature and wind along the source-receiver trajectory (5). Infrasonic waves will be refracted if vertical gradients in the effective sound speed exist. Waves will be bended back towards the earth's surface in case these gradients are strong enough. There are three regions in the atmosphere where strong wind and/or temperature gradients (may) exist that lead to turning infrasonic waves. (1) In the troposphere, in case of a temperature inversion near the surface or a strong jet stream around the tropopause at 10 km altitude. (2) In the stratosphere, due to the combined effect of a temperature increase with increasing altitude due to presence of ozone and strong seasonal winds around the stratopause at 50 km altitude. (3) In the thermosphere, where from 100 km and upwards the temperature strongly increases with increasing altitude due to direct influence of solar radiation on the molecules. As an example, the temperature and wind for a winter and summer atmosphere in De Bilt (the Netherlands) are shown in Figure 1.
A large amount of infrasound is continuously being recorded from a variety of man-made and natural sources. Anthropogenic sources include: explosions, nuclear tests, mining, military activities and supersonic flights. The latter is the cause of frequent reports in the Netherlands of felt tremors in buildings, similar to the sensation of an earthquake. Natural sources comprise: avalanches, oceanic waves, severe weather, sprites (lightning from cloud top to ionosphere), earthquakes, meteors, lightning, volcanoes and aurora. The measurement of infrasound is affected by noise due to wind and turbulence in the boundary layer. Therefore, infrasound is measured with arrays to increase the signal-to-noise ratio (SNR) through signal summation. Arrays are also used to estimate the direction of arrival of a wave and its propagation velocity. Typical sizes, i.e., apertures, are in the order of 100 to 1000 meters. Additional noise reduction at each array element is achieved by a wind barrier, a porous hose or pipe array with discrete inlets6). The recorded signals are thus a function of the state of the boundary layer and the upper atmosphere, which changes with time and geographical location. To unravel this complex picture, is the major challenge in source identification (7).
The surface based microbarometers can also be used as a passive probe for the upper atmosphere (higher than 30 km) with the large amount of sources continuously present. Actual recordings of the basic properties, like wind and temperature, of the upper atmosphere are sparse. Meteorological balloons reach an altitude of roughly 35 km but lack spatial and temporal coverage. Rocket sondes can reach the upper atmosphere but also lack coverage. Satellites have global coverage but have a limited vertical resolution and are difficult to validate for stratospheric altitudes. Therefore, most information currently depends on numerical weather prediction model characteristics. Infrasound can validate such models, and even information on a finer temporal and spatial scale is expected to be retrieved. Such information is very welcome for future atmospheric research. The troposphere and stratosphere have long been considered two isolated layers, split by an impermeable tropopause. The influence of the stratosphere on our daily weather and climate has recently been firmly established, showing that processes in the upper atmosphere do couple to the troposphere8).
The geophysical application within LOFAR, i.e., GEO-LOFAR, consists of seismological and infrasound equipment. The astronomical application will be realized on antenna fields where infrastructure, like power and high-speed Internet, is being established. GEO-LOFAR will make use of this infrastructure. The acquired data will be gathered at Groningen University from where they are distributed to the GEO-LOFAR partners, which are TU Delft, TNO and KNMI. The infrasound contribution consists of a High Density Infrasound Array (HDIA) and a Large Aperture Infrasound Array (LAIA).
A six element infrasound array (EXL) was realized at LOFAR's Initial Test Station near Exloo. EXL has an aperture of 250 meter and contributed to the discovery of exceptional fast infrasonic phases observed after the explosion of an oil-depot in the UK (10,11) (see Figure 4). The array also showed its value in the detection of lightning, by combining infrasound and electro-magnetic measurements within LOFAR (12,13).
In order to also sense gravity waves, the KNMI-microbarometer (KNMI-mb) has been adapted to periods of 1000 seconds, as lower cut-off. The earlier version of the KNMI-mb had a cut-off at 500 seconds and was specially designed to measure acoustic waves. The influence of temperature on the differential KNMI-mb is of main concern when lowering the frequency response. Temperature stability is ensured by properly insulating the instrument's fault and by its subsurface mounting. A detailed study of the amplitude and frequency response has been carried out (16). | 0.811352 | 3.072982 |
The Fornax Dwarf and its Five Globulars
Submitted: Tuesday, 28th August 2012 by Dana De Zoysa
The Fornax Dwarf and Its Five Globulars
Part 1: Observations, Feb 21–25, 2012
They’re all here. But where? (Source: ESO//Digital Sky Survey 2 48 MB hirez)
Dwarf galaxies are the smallest, least luminous, and most common galaxy systems in the universe. Of the 30-odd dwarf galaxies orbiting the Milky Way, the Fornax Dwarf Spheroidal PGC 10074 is intrinsically the brightest. But it is also 460,000 light years away, so actually seeing it is another matter. Its RA of 2h 40m places it directly beneath M77 (which neatly bisects the celestial equator at -00°00’48”). But its declination of -34° 27’ puts the Dwarf rather low for many northern observers—in the same declination band of Scorpius’s sting in summer and 10° more southerly than Lepus and Canis Major in winter.
For me, though, Fornax is nearly overhead in November, and very accessible from October through early March. I observe from Weltevreden Farm, 18 km west of Nieu-Bethesda in the negligibly populated and totally un-light-polluted skies of the Great Karoo in South Africa. The nearest other farm is 10 km away, and no Karoo farmer would be so spendthrift as to donate nocturnal floodlighting to the sagebrush and rabbits. The owls are fat enough as it is. The climate is semi-desert and looks much like the American Southwest, with skies to match. On moonless nights in February (seasonally equivalent to mid-August in northern skies), visual magnitudes are commonly 7.5 to 7.9, transparency is usually 8 or 9 out of 10, and seeing is 6 to 8. In February the Sagittarius star cloud rises about 2 a.m. and casts my shadow when I stand a few feet from a whitewashed wall. My equipment is a two-saddle Alt-Az holding a Celestron C6 150/1500 SCT on one side and a Santel 180/1800 MCT on the other. This pairing works very well using the C6 as a 50x super finder and the Santel ranging from 60x to 360x. Finding is strictly star-hopping. Good charts and a laser finder usually put an object in the 1.1° field of the C6’s 30mm 80° eyepiece. The observations below were made in mid-February, when the Dwarf was still 40° to 45° elevation above my western horizon at astronomical dark.
Harlow Shapley discovered the Dwarf nearly 75 years ago on glass photographic plates using the 24 inch reflector at Boyden Observatory in South Africa. 1938 was a good year for Shapley: he also discovered the Sculptor Dwarf Irregular galaxy using the same sets of plates. But it was a bad year for the classical Hubble “tuning fork” classification system for galaxies because these two galaxies fit nowhere on the tuning-fork branches.
Shapley noticed three globular clusters which he felt to be associated with the galaxy. These were confirmed and studied 1939 by Walter Baade and Edwin Hubble using the 100-inch Hooker reflector at Mt. Wilson. But due to its southerliness for the big North American telescopes, nobody paid much attention to the region till 1957—the year of both Sputnik and the introduction of Boeing 707s—when astronomer Paul W. Hodge set off “going like a Boeing,” to use the picturesque South African expression, to “Boyden in Bloemi” (Bleomfontein) to add two more globulars to the three then known. The five globulars ranged in visual magnitude from 12.6 to 13.9.
Above is Paul Hodge’s 1958 75-minute unfiltered blue/visual ADH plate taken in South Africa. (Read his original paper here.) Hodge named them Hodge 1 through 5, in keeping with the nomenclature practice of the time, which associated discoverers of clusters and H2 regions with the larger objects of which the clusters were a part. Hodge was a busy man in the early 1960s. He and George Wallerstein founded the Astronomy Department at the University of Washington in 1965; Hodge is still there. Over the years his name appeared on at least 200 technical papers listed on the SAØNASA Astrophysics Database. A great many other objects bore a Hodge # identity. A 1977 paper he authored about Barnard's Galaxy identified 16 star forming H II regions there, designated Hodge 1 to Hodge 16. M31 boasts 140 globular clusters and 413 open clusters bearing Hodge numbers, though many of the globulars were first charted by Edwin Hubble as far back as 1932 and described in his 1936 book Realm of the Nebulae. The Hodge system worked for its time, much to the dismay of catalogers and bibliographers of our time, who prefer tidier arrangements. But in honor of the man and his accomplishments, I’m going to keep to Hodge’s nomenclature system for the Fornax Dwarf globulars, duly noting the ESO designations for readers whose go-to paddles and handheld-device apps have fits when you enter the name “Hodge.”
Hodge’s Fornax five became a challenge for amateur and professional astronomers alike. Professionals wanted to know why the Fornax Dwarf was the only dwarf spheroidal galaxy then known to contain a globular cluster system. In the prevailing knowledge of the time, the Dwarf was the least massive galaxy known to have globulars and should have been too much of a lightweight to acquire or hold on to them. Why didn’t the globulars migrate to the center of the galaxy to boost its density profile? By 2005 a vast gob of dark matter was adduced to have been associated with the Dwarf’s unusual star-formation history. That solved the “digestion” problem, but it didn’t settle a lot of other issues. Which is why an arXiv.org search comes up with 243 technical papers associated with the Dwarf. Save these for a really rainy night when a game of Solitaire is a bit rich for your blood.
For amateurs the Fornax five are worth going after just because they are there. It’s not often one can see five faint, difficult globulars in the same field as a faint, difficult galaxy. The Fornax Dwarf clan is all the more worthy for anyone who wants to sharpen their spotting skills before going after the M31 globulars, whose brightest member G1 or Mayall II is half a magnitude fainter than the 13.9 vm of Fornax’s faintest globular, Hodge 1.
Aside from the challenge of just seeing them, what else is interesting about the Dwarf’s globulars? Five globulars is a large number for such a low-mass galaxy. They are a laboratory for comparing their physical and chemical evolutions with those of our own Milky Way and also the Magellanic galaxies. The histories of the Fornax globulars are complex. They average two to three billion years younger than the Milky Way globular cluster population, and their metal abundances vary by an order of magnitude. Lighter metals such as the oxygen, nitrogen, and carbon you’re breathing as you read this, are forged in stars with masses between 0.8 and 8 times that of the Sun when these stars evolve into red giants, blow their atmospheres off into space, and end as white dwarfs. Heavier metals like the iron which we think of when we use the word “metals,” are forged in core-collapse supernovas. There are significant metallicity differences between the Fornax Dwarf’s globulars and the galaxy’s own stars. How does one account for a large spread in metal abundances in objects of seemingly uneventful origins?
First, let’s find them. Alvin Huey’s The Local Group (p.51) makes hunting much easier for Fornax fans. One can hop from the two brightest stars on Huey’s Mega Star-derived chart (named Lambda Fornacis 1 and 2 on some charts) directly to the Dwarf’s largest and brightest globular, NGC 1049. Despite its listed magnitude of 12.6, 1049 is not a quick hit in my Celestron C6 ‘finder’ at 50x and 1°36’ tfov. I need at least 100x to ID it. It helps that 1049 lies in an area with few distractingly bright stars—the nearest one is mag 8.4 SAO 193841 (HD 16690) 15' NNE. At first glimpse 1049 has the imprecise look of a star on a night of bad seeing. A close inspection reveals a dot 40” in diameter. 1049’s surface brightness is nearly half a magnitude brighter, 12.2/sq arcmin (21.1/sq arcsec). For some reason 1049 always seems faintly blue to me, resembling Neptune but four magnitudes fainter. It’s a curious illusion.
One reason for 1049’s initial soft look is that it is a Class X globular whose appearance to my eye resembles a starry form of solar rim-darkening. (The I - XII system was devised in 1927 by Harlow Shapley and Helen Sawyer.) Australian observer Andrew Murrell’s 2007 IAAC report using a 20" dob described 1049 as a 40" patch with a bright almost stellar nucleus. “The main body of the cluster has an even surface brightness . . . . well detached from the background sky. At 300x it . . . looked like a faint globular when viewed through a small telescope.” A 30 October 2010 note by Steve Gottlieb on the Australian forum IceInSpace reported Fornax 3 as “a moderately bright gc in the Fornax Dwarf. Appears small, round, ~30" diameter, gradually increases to a small brighter core.” An observer using Australia’s Coonabarabran Observatory 30” at 264x described 1049 as “very bright, moderately large, very sharply concentrated with a very small, very bright core surrounded by 1' halo that dims around the periphery.” If the Coonabarabran skies are especially good an observer with a 30” telescope might resolve a few of 1049’s four magnitude 18.4 red giants. (Note for Jimi Lowrey and his 48” Tyrannostarus Rexas [T*xas?], 1049’s 6th brightest is 19.7. Go for it!) The rest of us who log 1049 must console ourselves that we have seen a globular 460,000 ly out, nearly twice as remote as NGC 2419 the “Intergalactic Tramp” in Lynx at 280,000 ly. (In the 1950s & 60s, what we today call the “remote halo globulars” were collectively called “the intergalactic tramp globulars”; see Hodge’s 1961 paper, p.84, 1st paragraph.)
That’s as close as 1049 ever gets: a 2010 paper by Méndez et al. calculates that the entire Fornax Dwarf system is presently near its 460,000 light year apogalacticon point in a near-circular orbit (eccentricity 0.13 or roughly one-eighth thinner in the minor axis) that takes about 3.2 billion years and never brings it closer than 400,000 light years. The Méndez team found a handy cosmologically-distant quasar behind the Fornax Dwarf whose light is preferentially absorbed by the Dwarf, giving spectrographers all kinds of useful absorption features to fiddle with. (Quasars—what would we ever do without them?) The Dwarf’s orbit is also retrograde and highly inclined (approx. 101°) to the Milky Way’s disk. That its locale is so remote from the MW center, plus its near-circular, highly inclined orbit, have important ramifications in understanding how the Dwarf was formed and has evolved.
Despite the fact that the Dwarf visually presents as a faint ellipse, it is technically a dwarf spheroidal. Until the Andromeda Galaxy arrives in 3 billion years or so, the Fornax Dwarf will escape the assimilation fated to the Sagittarius Dwarf. While the shredded Sagg Dwarf’s gift to amateur astronomers was the globulars M54 in Sagittarius and Pal 12 in Capricornus, we won’t be getting any going-out-of-business globulars from the Fornax Dwarf anytime soon. The near-circularity of its orbit shields the Fornax Dwarf from most but not all of the tidal forces of crossing the Milky Way plane and having its star-forming gas stripped away by ram pressure as it plows through the Milky Way’s gas halo. Not that it makes much difference—the Dwarf has only 5,000 solar masses of star-forming gas left anyway. In the Milky Way that would make it a fairly peewee Barnard object.
To the naked-eye, the constellation Fornax can be an empty place. (The Hubble Ultra Deep Field was recorded close by, near NGC 1360.) I started my search with NGC 1049 because the Dwarf itself is spread out (roughly half the diameter of the moon as seen in my 180mm aperture) and faint at a mean surface brightness of mag 17.0. I assumed the average surface brightnesses of 12.7/sq. arcmin (21.6/sq. arsec) of its globulars would be an easier find. Also, the Dwarf’s star density is 9 per sq. arcmin down to visual magnitude 19.9, while the globulars’ visual densities are approx. 80 stars per sq. arcmin, though they average 0.6 mag fainter than the galaxy’s. Find the globulars first, my reasoning went, and the galaxy would be somewhere in the middle.
Visual astronomy is full of assumption-demolishing surprises. To paraphrase the humorist Woody Allen: “If you want to give the stars a laugh, tell them your plans.” After half an hour of obsessing over globulars at 100x to 269x in the 180mm Mak, I rechecked the 50x field in the C6 SCT and belatedly noticed a faint but unmistakable brightness in the sky covering a third of the field of the eyepiece. I hadn’t paid much attention to it because at the magnifications needed to locate the globulars, the glow seemed nothing more than a half-dozen stars in the mag 11 to 13 range in between a couple of 13th mag fuzzy dots. The two fuzzy dots turned out to be fuzzy for a good reason, but only with a larger exit pupil did the big hazy galaxy loom behind that little twinkly asterism. I felt a little like the “Pink Panther” scene where Inspector Clouseau notes down every detail of the crime scene except the presence of the gun on the table. I also gained more empathy for Messier’s “mistake” in confusing a close double for a nebula because information he received from Helvetius indicated he had observed a nebula there. My mistake was exactly the opposite, misidentifying a faint glow as a group of faint stars.
It was brighter and smaller to my eye than Andrew Murrell’s description, “a faint glow just above the sky background covering an area of more than 50'.” As measured against the 1°20’ and 49’ tfov in the 30mm and 18mm eyepieces of the 180 Mak, the glow was more like 20’ along the major axis. (The Deep Sky Browser M45.com gives 57.8' x 43.3' at position angle: 60°, visual mag 8.8.)
The Northern Hemisphere amateur forums can be a bit despairing over the Fornax Dwarf, the same way southern observers wring their hankies over Cepheus. Admittedly, 34° degrees south dec is not a great help whilst seeking an extended dwarf galaxy whose stars are vm 18 to 25. But Andrew Murrell also wrote, “One of my observing companions had a Televue Traveller scope with him and we tracked the galaxy down with this RFT. The Fornax Dwarf was visible as a faint haze.“ (Teaser: No matter what your aperture, an object being near-overhead in black skies enhances spotting prospects no end. South Africa has a beer and braai (barbie) tradition to match Australia’s, there’s always a spare room at Weltevreden, and you can tote along an 8” SCT and alt-az on a 20 kg bag limit if you skimp on the wardrobe and toothpaste till you get here.)
I swept the field horizontally and vertically several times to confirm. The Dwarf was an unmistakable diffuse brightening each time. I revisited the field several times on subsequent nights with both scopes, throwing in sweeps of the nearby general fields as a check, and the verdict was constant: confirmed sighting.
The phrase “a faint brightening” seems rather a modest bowl of rice considering that the Fornax Dwarf weighs in at 61 million solar masses. Omega Centauri’s roughly 10 million stars is visible naked-eye at magnitude 3.7 (and a dec 14° further south, -47°28’). But Omega Cen is only 13,700 light years away, while the Fornax Dwarf is 33.5 times further out. If we lived 13,700 ly from the Fornax Dwarf it might rival the Large Magellanic Cloud in brightness, though not in all the exciting things going on there.
OK, two fuzzies down, four to go. Now Alvin Huey’s “The Local Group” was joined by my hard-copy edition of John C. Vickers and Alexander Wassilief’s “Deep Space CCD Atlas: South.” NGC 1049 is visual magnitude 12.6. The other four are listed as 13.4, 13.5, 13.6, and 13.9. In principle all five should be visible in 150mm apertures in clear, dark skies. Andrew Morrell’s IAAC report documents the five, but there are no reports known to me of them all being seen in single observing sessions. Hence this. The globulars are positioned as marked in the above image, which emulates the view in an SCT with diagonal at 33° South, with the Dwarf descending at 45° elevation above the western horizon.
Below are individual images in the object’s numerical order. Their surface brightnesses are brighter than their visual magnitudes. There’s no sorting through the tantalizing hints, glimpses, or glimmers the mind introduces into wide magnitude/surface brightness gaps when the eye is at the limit of its luminance threshold. Still, Hodge 1, marked on these charts as Fornax 1, is so difficult at mag 13.9 that you might want to read the following description for reference, then track down the other four globulars first to familiarize yourself with the overall field.
Hodge 1 aka Fornax 1 and ESO 355-SC029, is RA 02 37 02 dec -34 11 00 and is the most difficult. It is only 1.2’ dia. You also may want to check the DSS view of Fornax 1 (patience, it takes time to load). Lucky you if it ever looks like this in your telescope! Hodge’s 1961 paper, based on visual plates, not spectrographic data, states, “No. 1 is unusually open and poor in stars. It has a very irregular appearance, but is quite certainly a globular cluster, for its brightest stars are similar in magnitude and color to those of the other four globulars.”
Andrew Murrell describes Hodge 1 as “a very low surface brightness and the most challenging of the 5 main clusters. The cluster had a diameter of about 1' and had no central brightening. The low surface brightness made this a difficult cluster to locate without a chart. It was best viewed at 300x, where it could be seen easily with direct vision. This cluster lies to the NNW of the Fornax Dwarf.” To my 180mm eye it was so faint and diffuse that I detected it only momentarily three times across a cumulative half-hour looking at the exact spot where I knew it to be. As a tough object for a 180mm scope in good skies it compares to NGC 4730, one of the Centaurus Cluster galaxies at visual 14.1 (sb 13.8), or for northern observers using a 150mm scope, NGC 6675 near Vega in Lyra at mag 13.3 sb 13.9.
Hodge 1’s visual magnitude of 13.9 emanates from a spare 37,000 solar masses. (See the table at the top of p.2 of Angus & Diaferio’s paper for solar mass and orbital details for all of the Dwarf’s globulars.) That seems a modest mass for a globular. Indeed, it is exceeded in the flyweight department mainly by Pal 5, which has been tidally stripped till a mere 10,000 stars are left. Testifying to the virtues of life in a galactic exurb, Fornax 1 has been coherent as a single body for over 10 billion years. It is the remotest of all the Dwarf’s globulars at 1.6 kparsecs (5,200 ly) out—though its orbital details are still sketchy. Small-mass globulars remote from periodic galaxy crossings can retain structural integrity on Hubble-time scales of 13.8 billion years. For the Fornax Dwarf, that is three “perigalacticons” (the technical term for an orbiting galaxy’s closest approach to a larger one; “apogalacticon” happens at the far end). Even as remote as it is, each perigalacticon subjects the Dwarf and its entourage to a certain amount of ram-stripping of gas (analogous to a hurricane leaving a vacuum behind) and to the gravitational analog of a tidal wave encountering an island, sweeping its sand away as the wave recedes. All this trial and tribulation is reversed at apogalcticon, in whose distant reaches the hot gas generated by earlier orbital compression and supernova shock fronts gradually radiates its high-energy photons away, cools, infalls to the galaxy’s center, and awaits the next perigalacticon to initiate another billion-year starburst cycle. Three energy purges and it’s no wonder things are so quiet out there in Fornax land.
It wasn’t always like that. While globulars form early and enjoy mostly graceful retirements, dwarf spheroidals can form later and undergo dramatic star formation histories. The similar “star ball” appearance of globulars and dwarf spheroidals belies composition and histories that are very different. All dwarf spheroidals, like globulars, contain a population of ancient stars, but most dwarf spheroidals have undergone one or more starburst episodes. Also, almost all new dwarf spheroidal star formation occurs at the center. The timing and intensity of the formation periods is traced by the chemical enrichment of their various star populations. Primordial hydrogen and helium gas clouds collapsed to form stars. Many evolved modestly, like the sun. Early solar-mass stars went through the planetary-nebula/white dwarf phase, while heavyweights went supernova. These happened so long ago the only traces are a richer array of heavier elements. These enriched clouds in turn were swept up into new cycles of star formation and subsequent enrichment. Stefania Salvadori et al. proposed a time frame of about 250 million years for a typical enrichment cycle. (Also see these papers: 1, 2, 3.)
These ancient star forming episodes show up today in the Fornax Dwarf as absorption dips in high-resolution spectrograms. The Dwarf itself is large enough that over 2,000 of its 47,000 photometrically logged stars can be sifted by hundredths of a magnitude and arc-second into orbital, age, and color-magnitude bins. The five globulars are a different story. High-resolution spectroscopy of such tiny, faint objects requires long exposure times in pricey 6-meter class telescopes hosting multiobject spectrographs. These transport photons via fibre-optic light threads instead of the pixel-based devices used by we folks lacking 6-meter budgets. But like pixel data, fibre optic data is degraded too, by crowding, source confusion, signal-to-noise ratios, and fiber crossings. These effects are as frustrating as bad seeing. The FLAMES instrument on the Very Large Telescope in Chile required four hours to obtain individual Fornax globular spectra to visual magnitude 18.5. That’s a lot of effort for a handful of stars from a globular 460,000 ly out.
Another method commonly used to determine object distances—proper motion studies—poses even more problems. An object with a transverse velocity of 100 km a second (roughly three times as fast as the Fornax globulars appear to move) at a distance of 325,000 light years traces a proper motion of 0.2 milli-arc-seconds per year. That comes to 0.03 pixels on the Hubble’s Advanced Camera for Surveys over the 15 year baseline during which the cluster data has been recorded (scroll through to the article’s section on the Leo I and II dwarf galaxies). Costly and arduous though it may be to acquire, the data reveal Fornax’s five globulars to be structurally simple compared with the galaxy itself. There are multiple gradients of carbon and intermediate-age stars in the galaxy, for example, but none in the globulars.
We can get an idea of what Fornax looked like to the Dwarflings residing there 3.5 billion years ago by panning across the northern reaches of the Large Magellanic Cloud, florid with pink supernova bubbles and magnetically twisted gas clouds. In a hundred million years these will be but traces. We would see a mass of new H2 and OIII bubbles much like the existing ones but richer in heavy elements. If these filaments and bubbles look disturbing, they are. Because of them, only a quarter or less of a collapsing gas cloud ends up in stars; the rest is enriched and redistributed; enriched and blown away; or enriched and turned into stars. (And we think OUR taxes get turned into a lot of hot air!)
While one marvels how objects like NGC 6791, the 6.9 billion-year-old open cluster in Lyra, can hang on for so imponderably long while porpoising above and beneath the gyres and eddies of the Milky Way, the answer shows up in 6971’s color-magnitude diagram: two distinct billion-year-long copious gestations of white dwarfs. In the case of the Fornax Dwarf’s globulars, the Angus & Diaferio paper analyzes several orbital models to find one that fits their known positions and orbital eccentricities, yet also supports the current information that their orbits are stable over Hubble time.
The best-fit model results in a rosette-like orbital eccentricity pattern. Note the number of orbits concentrated in the lobate donut 1.5 to 2 kpc (4875 to 6500 ly) from the center. This is a tidal-radius orbital pattern that circularizes an eccentric orbit. (A tidal radius is the outer limit of a cluster’s gravitational potential energy well, outside of which its stars can be pulled away by more massive objects like a galaxy.) De-ellipticization implies the presence of a very large mass of dark matter centered on the Dwarf, whose gravitational well is sufficient to circularize orbits but not great enough to decay the orbits into the center.
Hodge 2, aka Fornax 2 and ESO 356-SC001, at RA 02 38 44 dec -34 48 33, stands out easily from its star field. The Harris Globular Catalog classifies it as a Class VIII globular (see section III of the catalog) 1.2’ dia with a visual magnitude of 13.5 and a surface brightness of 13.6. A mag 12.5 field star near its core improves your chances. Andrew Murrell writes, “Fornax 2 Is a 1' haze of even surface brightness much brighter than cluster 1. It was easily visible and well defined against the background sky. The cluster was seen through a 12" scope with direct vision and could be seen with averted vision in a 10". A 15th magnitude star lies just off the SW edge of the cluster. Cluster 2 lies to the SW of the Dwarf.” My notes state, “Forms a near-right triangle with the bright, close 40” pair of stars TYC 7014-766-1/2 of mag 10.6/12.1 (the close pair in the annotated image) and TYC 7014-50-1 at 11.5; easily found; seen direct vision throughout this logging; presents a faint, tight, hard-edged core and weak-edged outer halo, lacks the blue cast of N1049; seems rather loosely packed for a Class 8; looks like NGC 7006 Delph in a 80mm at 125x.” Hodge 2 radiates the light of 182,000 solar masses and orbits 1.05 kpsc (3410 ly) from the Dwarf at a rate of roughly 4 kms/second.
Hodge 3 aka ESO 356-SC003, Fornax 3 is NGC 1049, the globular most Fornax ferreters find easiest. It lies RA 02 39 48 dec -34 15 30. It is a tiny globular, only 0.8’ dia., yet is the brightest of the Fornax Five (thanks to 363,000 solar masses) at visual magnitude 12.6 and surface brightness 12.2. It is bright enough to feature in Northern Hemisphere observing reports using telescopes upward of 5.5 inches. Steve Gottlieb’s observing notes on NGC/IC mention, “Located 15' NNE of mag 8.0 SAO 193841”, which is out of the field in this 10’x10’ image. The brighter star adjacent to NGC 1049 at 6:30 o’clock in this image is mag 14.15 and the fainter, closer star at 7:00 is 16.2. Australian Andrew Murrell reported, “Appears as a 40" patch with a bright almost stellar nucleus. The main body of the cluster has an even surface brightness. . . . The cluster was well detached from the background sky. It was best viewed at 300x where it even looked like a faint globular when viewed through a small telescope.” My own notes added: “Once spotted at 100x, 1049’s appearance barely changed while ascending the magnification scale to 369x. As the sky background darkened in response to magnification, the bluish cast became more pronounced, till at 369x it looked like Neptune. The core seemed to become denser and the halo thinner as the power went up.”
We’re going to skip over the youthful and problematic Fornax 4 for a moment and deal with the more straightforward and easily findable Hodge 5.
AKA Fornax 5 and ESO 356-SC008, Fornax 5 is at RA 02 42 21, Dec -34 06 05. This cluster is located away from the main body of the galaxy toward the North East. It is an easy star hop from the center of the Dwarf—look for the line of 4 stars marked “Pointers” on the annotated chart. The same diameter as 1049 but 0.8 magnitudes fainter at 13.4 (12.7 surface brightness), it radiates the luminosity of 178,000 solar masses. It is density Class III, with a tight core and faint, thin halo. With a mean distance of 4645 ly from the Dwarf’s center of mass and a moderately elliptical orbit with a perigee of 3900 ly, it whizzes along at the breathtaking (by Fornax Dwarf standards, anyway) speed of 34 km/second. To data-record anything more takes sophisticated equipment and photometry skills. Andrew Murrell writes, “Appears as the smallest of the clusters at an apparent diameter of just 30". My log states, “369x: N1049 lite, fainter nucleus, thinner halo.”
To professionals, Fornax 4 is the most interesting of the lot.
AKA Hodge 4 and ESO 356-SC005, it lies at RA 02 40 07, Dec -34 32 15 and is a tight Class IV globular 0.6’ dia. with a visual mag of 13.6, sb 12.1 /sq. armin (20.1 arcsec). Fornax 4’s high luminosity-to-size ratio makes for a visually dense core with fainter halo. Andrew Murrell confirms: “Lies just a few arc minutes SW of the 9th magnitude star [off-field on above image]. This cluster appears very similar to but fainter than NGC 1049 with the bright nucleus surrounded by an even surface brightness halo. It has a 15th magnitude star just off the northern edge of the cluster.” But while Fornax 1, 2, 3, and 5 are by-the-book color-magnitude globulars, Fornax 4 has astronomers busily writing papers. Sydney Van Den Bergh and Buonanno et al. (1999) used the Hubble Telescope to obtain Fornax 4’s color-magnitude diagram. Where 1, 2, 3, and 5 have horizontal branches that include a wide range of colors and many of the RR Lyrae variables used to evaluate globular distances, Fornax 4 combines a clumpy red giant horizontal branch with a narrower range of other colors. Its red branch stars are still evolving towards the planetary nebula/white dwarf stage, which the other Fornax globulars passed through billions of years ago. This and orbital path data puts Fornax 4 at three billion years younger than the other globulars.
More interesting, Fornax 4 formed in the center of the Dwarf, not out in the halo where dwarf galaxy globulars usually form coevally with the parent galaxy. Fornax is not alone in this, a number of other dwarf spheroidals have the same property. Van Den Bergh’s paper asked why is it that dwarf spheroidal galaxies can form globular clusters in the central regions long after globular formation has ceased in the galaxy’s halo. Buonanno’s paper asked how a globular cluster can form at all in the center of a low-mass galaxy that evolved billions of years earlier and shouldn’t have enough star-forming gas left. Where did the gas come from? Did the Fornax Dwarf somehow manage to accrete an even dwarfier dwarf? It’s not a far-fetched notion—the dwarf irregular NGC 4449 in Canes Venatici has elongated a nearby subdwarf into a stellar spindle and is now eating it like a noodle (see p.3 of the Martinez-Delgado paper).
“Zut alors!” exclaims Inspector Clouseau, “I smell something odd in this room. It smells like . . . smoke!”
Aaahh, is the Inspector on to something? The Fornax Dwarf system is a visual challenge. The thrill of seeing all five globulars dotted across the faint main galaxy is like seeing a rich Abell Cluster for the first time. Yet simply seeing it is a little like Inspector Clouseau noting everything at the crime scene except the evidence. Like the good Inspector, professional astronomers are devoting increasing telescope and computer modeling time to the Dwarf, and keep coming up with new questions as they answer old ones. Until recently the Fornax picture comprised two major star formation epochs, each consisting of several episodes. The first epoch, from metal-poor primordial gas, was coeval with the birth of globulars 1, 2, 3, and 5, ten billion years ago. Then a slow decline in star formation. Between 7 and 2.5 billion years ago Fornax formed the bulk of its present stellar populations from the gas enriched by the earliest stars. Star formation has continued at a declining rate in the central regions until as recently as 100 million years ago—and some reports now say 10 million years.
Hmmm, Inspector, is that a gun on the table?
“Zut alors!” Clouseau exclaims, “I smell le smoke! I see le gun. But what is ze connexion between les two? We must look for ze 2nd section of zis report!” | 0.914864 | 3.589684 |
The theory of general relativity is packed with strange predictions about how space and time are affected by massive bodies. Everything from gravitational waves to the lensing of light by dark matter. But one of the oddest predictions is an effect known as frame-dragging. The effect is so subtle it was first measured just a decade ago. Now astronomers have measured the effect around a white dwarf, and it tells us how some supernovae occur.
In general relativity, gravity is not a force. The presence of a mass bends space around it, and this means that objects moving near the mass are deflected from a straight path. This deflection looks as if the object is being pulled toward the mass as if by a force we call gravity. When a large mass is rotating, space also twists slightly in the direction of rotation. It is this effect that is known as frame-dragging.
You can see an illustration of frame-dragging in the figure. The central object is a massive rotating body, such as a black hole. The red dots represent points that are “at rest,” which means they aren’t moving through space. Instead, they move because space around the body is twisting due to the rotation. This frame-dragging effect is in addition to any orbital motion an object might have, and it is part of the reason why the accretion disk around a black hole can get so extremely hot.
Near Earth, the frame-dragging effect is very small. So small that it took a special satellite to measure it. Known as Gravity Probe B, the spacecraft contained one of the most spherical objects ever made. Once in space, the sphere was set spinning and watched over time.
Without frame-dragging, a spinning sphere orbiting the Earth should always keep the same orientation, like a gyroscope. Earth’s gravity can’t cause it to twist on its own. But frame-dragging can. Because of Earth’s rotation, the region of space closer to the Earth twists just slightly faster than the region of space farther away. This means the part of the sphere that’s closer to Earth gets a little push, and as a result, it’s orientation changes over time. We call this Lense–Thirring precession. In 2015 the team measured this precession, and it agreed perfectly with general relativity.1
While the frame-dragging effect is larger around massive bodies like white dwarfs and neutron stars, it isn’t easy to measure. To measure the frame-dragging of a body you need to have something orbiting it. Luckily for us, many white dwarfs and neutron stars are part of a binary system. So recently a team used a binary system to study frame dragging.2
In 1999, the Australian Parkes Radio Telescope discovered the pulsar PSR J1141-6545. It is a neutron star that’s in a binary orbit with a white dwarf star. The distance between these two stars is only about the width of the Sun, and they orbit each other every five hours.
Because pulsars emit a sharp radio pulse at regular intervals, astronomers can use them to make extremely accurate measurements of the pulsar’s motion and orbit. The measurements are so precise that we can use them to measure the effects of general relativity, including frame dragging. Because the white dwarf is rotating, the orbit of the pulsar precesses slightly over time. The amount of precession depends on the mass and rotational speed of the white dwarf.
After observing the pulsar for twenty years, the team not only observed frame-dragging, they used it to measure the rotational speed of the white dwarf. They found that it rotates once every 100 seconds, which is quite fast for a white dwarf.
The results agree with a popular model about how close binary systems evolve. Pulsars form when large stars die and become supernovae. This means the binary system was once a binary system where a large star orbited the white dwarf. As the star reached the end of its life, material from its outer layer would have been captured by the white dwarf, causing it to spin faster. The observations show that the white dwarf formed before the pulsar.
All this from an amazing work of astronomy, measuring relativistic frame-dragging in a star 12,000 light-years away.
Everitt, C. W. F., et al. “The Gravity Probe B test of general relativity.” Classical and Quantum Gravity 32.22 (2015): 224001. ↩︎
V. Venkatraman Krishnan, et al. “Lense–Thirring frame dragging induced by a fast-rotating white dwarf in a binary pulsar system” Science Vol. 367, Issue 6477, pp. 577-580 (2020) ↩︎ | 0.86902 | 4.14164 |
By Taylor Marvin
Enough policy, here’s something completely different:
How common is intelligent life in the universe?
This question reduces to four possibilities: that all forms of life are rare in the universe and Earth’s life is the result of extraordinary circumstances, that simple life is commonly found but the complex life we are most familiar with is very rare, that both simple and complex life are common, and finally that intelligent life is found throughout the universe.
It’s important to remember that this question and the entire field of exobiology is extremely speculative by definition. Many of the field’s core ideas and claims can’t be falsified or even observed. For the most part, the lens through which we view life is very limited. The only examples of life that we can observe are those found on Earth, which all share a common ancestor and are fundamentally similar. All of Earth’s species share a system of coding genetic information in DNA molecules and similar metabolisms. We don’t know if this is the only possible structure of life or even if this is the only type that evolved on Earth; it’s entirely possible that another alternate biochemistry arose on the early Earth and disappeared without a trace. What is true is if a form of extraterrestrial life is based on the same class of biochemistry found here it would share its broad environmental requirements with the life we’re familiar with. This is interesting- because we can investigate how common Earth-like environmental conditions are in the galaxy it’s possible to make educated guesses about the frequency of extraterrestrial life chemically similar to that found here. For life dissimilar to that of Earth its impossible to say. It’s easy to imagine some exotic form of life radically different than anything we have ever encountered- interesting to be sure, but this is ultimately speculation without any real scientific backing. Any discussion of the frequency of extraterrestrial intelligence is limited to life broadly similar to what we are familiar with here on Earth because the environmental requirements of hypothetical exotic forms of life are too far beyond our comprehension even to guess at. For this reason all estimates of intelligence in the universe are inherently conservative.
The first possibility is that life of any form is very rare in our universe and the Earth is exceptional. It’s entirely possible that life of any kind simply doesn’t exist beyond Earth. Many solar systems and even galaxies are fundamentally incompatible with life. Any form of life we can understand requires a terrestrial surface, and older stars and galaxies are so metal-poor that they don’t support this type of body. Additionally, large regions of our galaxy appear too hostile for life to exist. The outer rim of the galaxy is too poor in heavy elements to allow terrestrial planets to form, and the inner regions seem to be too saturated with dangerous radiation to support life. Additionally, because stars are so close together in the galactic core planet sterilizing stellar disasters like supernovas would be much more common, imperiling any life that did evolve there.
The view that all life is extremely rare is also supported by the uncertainty surrounding the origins of life on Earth. Life is an extremely complicated chemical process and scientist are unsure of the exact conditions necessary for its inception. Certainly an element of chance is present; there could be millions of worlds with the conditions that would permit the inception of life but where it never actually begins. Unfortunately our uncertainty about just how life begins is so great that questions about how frequently any type of life arises remain pure speculation.
One other possibility that would indicate a lack of life in the wider universe would be that while the conditions that allow life to begin are common they don’t last. In our solar system both Mars and Venus had climates similar to Earth in their early histories but changing solar and atmospheric conditions slowly transformed Venus into a burning hell and Mars into a dry cold desert. If this is a common path of planetary evolution many early biospheres could become more and more inhospitable, slowly suffocating their inhabitants and greatly reducing the total number of life-bearing planets in the galaxy.
Let’s consider the second possibility: perhaps simple life is common in the universe but complex multicellular life is not. After all, simple life like bacteria and archaea have much less strict environmental requirements than complex life like animals and plants. On Earth, simple organisms are found in all extreme environments. Microscopic extremophiles thrive in very acidic or basic environments or extreme heat or cold. Simple life is also found deep underground or at the hostile ocean bottom, using chemical sources for energy in the absence of the sun. It’s very hard to kill bacteria- it’s likely that some varieties of Earth’s microorganisms could survive on Mars, and bacteria have been demonstrated to be able to survive in the vacuum of space. These types of simple life could the survive hard radiation or drastic environmental changes that are the most common survival challenges in the universe. In fact, most varieties of simple life seem capable of enduring asteroid impacts, changes in solar energy, and nearby gamma-ray bursts, all of which are the greatest threats to nascent life’s long term survival.
For complex life, environmental requirements are much more stringent. Plant and animal-like life broadly similar to Earth’s would require a planet with a thick atmosphere and fairly constant environmental conditions. This rules out most of the galaxy; the inner core with its dense concentrations of stars suffers from high radiation and gravitation perturbations that increase the danger from asteroid impacts while the outer regions lack the heavier elements necessary for terrestrial planets or moons. In fact entire types of galaxies, notably globular clusters, are unfit from terrestrial-like life. Even worse, these conditions are not constant. Stars move through their galaxies in long orbits, and if a potentially life-supporting solar system’s movement brought it too close to an inhospitable galactic region its life would be extinguished. Also, the need for a constant climate excludes many types of stars; any star with a variable output or giant stars with short life spans would be incompatible with the emergence of advanced life. While terrestrial rocky planets seem to be common in our galaxy the specific conditions complex life requires would exclude many extraterrestrial planets. A life-bearing rocky planet cannot be too small: below a certain size a planet cannot gravitationally retain a significant atmosphere and will quickly exhaust its core’s heat necessary for the plate tectonics that stimulate evolutionary development. A life-bearing planet cannot be too close or too far away from its star- because all forms of biochemistry as we know it require a liquid solvent a planet’s climate must allow either liquid water or another exotic solvent, like ammonium.
While it is possible to imagine many exotic life forms able to thrive in environmental conditions very different from Earth’s it is clear that there are many more environments in the universe suitable for simple rather than complex life.
Just because the conditions that would permit the development of complex life are common does not imply that the life itself is. Complexity, like intelligence, is an evolutionary adaption and is not guaranteed to ever arise even on a fertile planet. Life first arose on Earth about four billion years ago, while animals only in the last 600 million years. It is entirely possible that a planet teeming with simple life would never experience the conditions or chance that sparked the emergence of more complex, familiar life.
A third possibility to our question is that, despite formidable environmental challenges, multicellular, complex life is common in the universe. This view is most supported by the size of the galaxy: the Milky Way contains hundreds of billions of stars, a sizable percentage of which host rocky planets. Supporters of this idea argue that it’s wrong to believe that the Earth is the only planet out of hundreds of millions to develop complex life. Furthermore, the specific environmental conditions found on Earth aren’t as rare as commonly thought. Mars certainly could have supported some form of life early in its history and other bodies in our solar system like the moons Titan and Europa offer tantalizing clues to their potential habitability. Astronomer have also discovered at least one extrasolar planet, Gliese 581 g, with surface temperatures that could support liquid water, a prerequisite for Earth-like biochemistry. In spite of its specific environmental requirements and vulnerability to varied environmental threats complex life could be common, an assertion that is ultimately best supported by the sheer size of the universe.
Just because multicellular life is common in the universe does not mean intelligence is. On Earth animal life existed for 600 million before the emergence of intelligent humans. What is important to understand is that the history of life is not a grand structured procession towards intelligence; rather, human intelligence is an evolutionary adaption that arose in response to specific environmental pressures. It foolish to expect an extraterrestrial world, after 600 million years of complex life, to suddenly see the emergence of consciousness. We have a poor understanding of exactly what conditions favored the beginning of advanced intelligence among early humans- it’s entirely possible that an extraterrestrial equivalent of the great apes could face different environmental pressures and would never evolve the extraordinary cognitive abilities that define us. Intelligence is only a tool for survival and if opportunity and environmental conditions don’t select for it advanced cognition won’t emerge.
However, there are plausible theories that support the notion that if complex life is common in the universe intelligence could be as well. One of the strongest arguments to support this idea is the history of human development here on Earth. On the surface, human intelligence seems excessive; while toolmaking and complex communications certainly had valuable evolutionary utility it is harder to imagine what environmental pressures would select for, say, the human preferences for visual art or music. Moreover, our intelligence comes at a high cost. Humans’ long vulnerable childhoods and need for large amounts of parental care is directly due to our intelligence: human babies must be born relatively premature so that infants’ large brain-cases can pass through women’s hip structure. Even then, human childbirth is uniquely dangerous; it’s rare in the animal world for so many mothers to die is such a fundamental activity. What then could have led to the emergence of humans’ fantastic intelligence in spite of its cost?
One of the most convincing theories, the ecological dominance-social competition model, holds that early humans grew so dominant over their environment that competition from other humans in a social group, not outside environmental pressures, became the single greatest determinant of reproductive success. In this environment it was the humans with greater intelligence and accompanying social skills needed to navigate increasingly complex group dynamics, not the strongest or most aggressive, that spread their genes the farthest. This led to intense reproductive competition that favored cognition and social abilities far beyond any pressure from the natural environment. Complex social structures, language, and the rest of otherwise superfluous human cognition all evolved due to social selection, rather than the pressures of a specific natural environment. What’s most interesting about this theory is that it appears to apply universally- any extraterrestrial social animal that achieved dominance over its natural habitat would experience the same slow shift from environmentally to socially driven evolutionary pressures and possibly subsequent runaway cognitive development.
There is another possibility. Perhaps intelligence is rare in the universe not because it rarely arises but because it is short lived. Most species survive for only a few million years before becoming extinct, and the natural world holds many hazards intelligent life is not immune too. Changing climates, asteroid impacts or a nearby supernova could all randomly end a extraterrestrial intelligence in its infancy. This threat is closer than most of us think; on Earth natural disasters have almost drove humans to extinction. 75,000 years ago a huge volcano on the Indonesian island of Sumatra erupted, lowering global temperatures and possibly reducing the human population to as few as 1,000 reproducing pairs. Such a close call wouldn’t be unique to humans and there is no reason to suspect another intelligent race would be so lucky.
More likely is the threat posed by intelligent species to themselves. Humans are the only species in the history of the world to have the power to terminate their own existence. Intelligence brings a high level of control of the natural environment- this presents a long-term danger. In the last century our civilization has developed technologies that have the potential to end much of life on Earth, and these same capabilities would be available to any sufficiently advanced extraterrestrial civilization. Acquiring potentially destructive technologies like nuclear weapons or bioengineering is a natural byproduct of scientific development and would probably be quite common to all intelligent species. It could be that civilizations as a rule don’t survive long after developing this armageddon capability; after all, humans have only managed to survive 60 years of nuclear armaments with several close calls, and we still have plenty of time to destroy ourselves. However, there is reason to hope: the technologies to develop world-ending weapons and advanced space travel are linked. It seems that most civilizations that survive their first few centuries of nuclear power would be able to spread their species over nearby worlds and greatly reduce their vulnerability to one species-ending disaster.
Of course, any attempt to answer the question of extraterrestrial intelligence is ultimately just and interesting exercise- informative and based in science, but ultimately no better than pure speculation. We simply don’t know enough about the universe or life itself to have any idea of what’s possible. However, this is one of the most fundamental questions people can ask, and one that has been a subject of human curiosity for millennia. From angels to modern science fiction the possibility of alien intelligence is universally fascinating. There are worse questions we can wonder about.
Note: This post borrows heavily from the excellent book Rare Earth. Other sources include:
Alexander, R. D. How did humans evolve? Reflections on the uniquely unique species. Museum of Zoology (Special Publication No. 1). Ann Arbor, MI: The University of Michigan, 1990.
Ambrose, Stanley H. “Late Pleistocene human population bottlenecks, volcanic winter, and differentiation of modern humans.” Journal of Human Evolution Volume 34, Issue 6. June 1998, 623-651. | 0.847913 | 3.235915 |
When it comes to orbital launch positioning, the Earth has something of a sweet spot: the equator. Like a gigantic planetary baseball bat, rockets jump off the Earth's center-line with ease, able to enter geostationary orbits using a fraction of the energy required anywhere else on the planet.
But the problem is that there isn't a whole lot of usable land along the equator—so one enterprising consortium has found a way to bring the land with it, so to speak, and launch rockets from the middle of the ocean.
Sea Launch is both the name of the detachable pier, normally docked at the port of Long Beach, that moves out into the remote waters of the Pacific for equatorial launches, and the four-company, non-governmental spacecraft launch consortium (Norway, Russia, Ukraine, and the US—headed by Boeing) that runs it.
Since the Earth's rotational speed is greatest at the equator (like the weight at the end of an angular-spinning string) it provides an extra bit of boost to the launch. Additionally, the phase change necessary to place an object in geosynchronous orbit around the equator is effectively reduced to zero. Since the spacecraft doesn't have to expend any extra energy to get into position over the equator, Sea Launch can replace the fuel needed for those maneuvers with 17.5- to 25-percent more cargo. And, in an industry where an extra ounce of cargo can cost an extra $10,000 or more, 25 percent more stuff for free is a huge deal.
What's more, since the equator is equidistant from both poles, it is equally capable of launching items into orbit in both hemispheres, something that launch sites like Cape Canaveral, which is 28.5 degrees North, cannot offer.
There's also the matter of safety. Since these rockets are launched from the middle of the ocean, even if they do fail—as three have over the course of 31 launches since 1999—there's practically zero chance of debris hitting a populated area. Nor is there any significant risk of interference from shipping or airline traffic.
The Sea Launch Zenit-3SL launch system itself is comprised of three parts: the Rocket Segment, the Marine Segment, and the Home Port Segment. The Rocket Segment is made up of the launch vehicle itself—a 200-foot-long, 14-foot-wide rocket capable of putting up to 11,000 pounds of cargo into orbit thanks to a 1.6 million-pound-thrust first-stage RD-171 Zenit rocket motor.
The Marine Segment is comprised of two parts: the Sea Launch Commander and the Launch Platform Odyssey. The Commander acts as the mother ship/command station, measures 600 feet long and 106 feet wide with a crew of 240. The Odyssey, on the other hand, is a modified, self-propelled oil rig capable of stabilizing itself in high seas and holding a GPS-guided stationary position on the open ocean. The two vessels communicate via a dedicated radio link wherein the entirety of the platform's operations are controllable from the Commander, making the Odyssey one of the largest radio controlled vehicles on the planet.
Both the Commander and the Odyssey, operate out of the Home Port segment, located in Long Beach, California. This 17-acre site houses all of the operational and logistics facilities, including payload processing, fueling equipment, tracking and communications suites—everything needed to put cargo into space.
While sea launches are relatively rare compared to land-based launches, a number of major companies, including EchoStar, DirecTV, XM Satellite Radio, PanAmSat, and Thuraya, have employed the service. And, with NASA budgets continuing to shrink, commercial launch ventures like this will have to step in if we want to keep enjoying the location-finding abilities geosynchronous satellites provide us. [Wiki - Sea Launch - Boeing] | 0.823934 | 3.08234 |
3.6.2. Virgocentric Flow
Shortly after the detection of the DA, Aaronson et al. (1980) presented evidence that the determination of H0 from the distance and observed velocity of the Virgo cluster yielded systematically lower values than using more distant clusters. This difference suggested that the observed velocity of Virgo was not equal to its cosmic velocity but instead was a combination of its cosmic velocity and the infall of the Local Group towards Virgo. This phenomenon is known as Virgocentric flow. A schematic illustration of the way that a virialized structure like Virgo perturbs the local Hubble flow is shown in Figure 3-16. Virgocentric flow seriously distorts the relation between redshift and distance as multiple distances can give rise to the same observed velocity.
Figure 3-16: Distortion of the Velocity Field which is caused by spherically symmetric infall into a virialized structure. Here the spatial distribution of infall galaxies is plotted with heads or tails on them to indicate the amplitude of their infall velocity. Note that the heads and tails always point at the center of the virialized cluster. This figure comes from Villumsen and Davis (1986).
Let's assume for the sake of illustration (and easy math) that the distance to Virgo is 15 Mpc and that H0 = 100. The cosmic velocity of Virgo is then 1500 km s-1. A galaxy in Virgo at this distance which was at rest with respect to the Virgo cluster would also have a velocity of 1500 km s-1. However, a galaxy located at a distance of 10 Mpc between us and Virgo could be accelerated by Virgo to a velocity of 500 km s-1 and thus its observed velocity would be 1000 + 500 = 1500 km s-1 even though its distance is 10 Mpc. Similarly, a galaxy located at 20 Mpc could have its expansion velocity with respect to us retarded by its proximity to Virgo at a value of 500 km s-1 and hence its observed velocity would be 2000 - 500 = 1500 km s-1. To understand that this was occurring would require the measurement of relative distances with sufficient accuracy that could resolve the differences between distances of 10,15 and 20 Mpc.
If Virgo is intrinsically at rest with respect to the CMB, then a determination of the Milky Way's infall velocity will provide the necessary correction to the observed velocity of Virgo to produce its cosmic velocity. From this cosmic velocity, H0 can be determined using the Virgo cluster distance modulus determined in the last chapter. Significant efforts to determine this infall velocity were made by Aaronsonet al. (1982) and Davis and Peebles (1983). Those efforts continue to the present day with no real convergence on the infall velocity. Values of 250 (Aaronson et al. 1982; Jerjen and Tammann 1992) - 350 km s-1 (Tonry et al. 1993) are consistent with the data and this range of values produces a 10% error in the determination of H0 even if we know the distance to the Virgo cluster with arbitrary accuracy.
This infall of the Local Group towards Virgo should also be reflected against some more distant reference frame. In 1986, Aaronson et al. were able to detect this reflex motion of the LG using a reference sample of clusters located at distances of 50 - 100 Mpc. Moreover, this detection also carried with it one of the initial indicators that the scale over which peculiar velocities are generated is significantly larger than the separation between Virgo and the LG. As discussed earlier, the DA does not point directly at the Virgo cluster. The vector difference between the DA and the Virgo cluster points in the general direction of the Hydra-Centaurus region. This suggests that the Local Supercluster is feeling the attraction of its nearest mass concentration, the Hydra-Cen Supercluster. This situation is schematically illustrated in Figure 3-17 and shows that Virgo itself may also be moving.
Figure 3-17: Schematic representation of the Local Velocity Field from Aaronson et al. (1986). Here the Milky Way is infalling towards Virgo at approximately 300 km/s and the entire local Supercluster is infalling towards Hydra-Cen at approximately 300 km/s. The vector sum of these two infall components to the motion of the Milky Way approximately accounts for the observed dipole anisotropy in the CMB.
Thus, a correction for Virgocentric Infall alone is insufficient to recover the cosmic velocity of Virgo. An additional correction for the motion of the entire Local Supercluster towards Hydra-Cen must now be formulated and applied. In a kinematic description of the local velocity field, the motion of the LG towards Virgo can be thought of as a form of dipole anisotropy. The influence of Hydra-Cen acts as a quadrupole anisotropy in the local velocity field. (see for instance Lijle et al. 1987). If mass concentrations other than Hydra-Cen are felt by the LG then higher order anisotropies need to be considered as well. | 0.87383 | 4.072473 |
Black hole research could aid understanding of how small galaxies evolve
(9 January 2018 - University of Portsmouth) Scientists have solved a cosmic mystery by finding evidence that supermassive black holes prevent stars forming in some smaller galaxies.
These giant black holes are over a million times more massive than the sun and sit in the centre of galaxies sending out powerful winds that quench the star-making process. Astronomers previously thought they had no influence on the formation of stars in dwarf galaxies but a new study from the University of Portsmouth has proved their role in the process.
The results, presented today at a meeting of the American Astronomical Society, are particularly important because dwarf galaxies (those composed of up to 100 million to several billion stars) are far more numerous than bigger systems and what happens in these is likely to give a more typical picture of the evolution of galaxies.
Size comparison of a dwarf galaxy (right inset, bottom) with a larger galaxy in the centre. Top inset: Dwarf galaxy overlain with some of the MaNGA data, revealing the winds from the supermassive black hole (courtesy: University of Portsmouth)
“Dwarf galaxies outnumber larger galaxies like the Milky Way 50 to one,” says lead researcher Dr Samantha Penny, of the University’s Institute of Cosmology and Gravitation. “So if we want to tell the full story of galaxies, we need to understand how dwarf systems work.”
In any galaxy stars are born when clouds of gas collapse under the force of their own gravity. But stars don’t keep being born forever – at some point star formation in a galaxy shuts off. The reason for this differs in different galaxies but sometimes a supermassive black hole is the culprit.
Supermassive black holes can regulate their host galaxy’s ability to form new stars through a heating process. The black hole drives energy through powerful winds. When this wind hits the giant molecular clouds in which stars would form, it heats the gas, preventing its collapse into new stars.
Previous research has shown that this process can prevent star formation in larger galaxies containing hundreds of billions of stars – but it was believed a different process could be responsible for dwarf galaxies ceasing to produce stars. Scientists previously thought that the larger galaxies could have been interacting gravitationally with the dwarf systems and pulling the star-making gas away.
Data, however, showed the researchers that the dwarf galaxies under observation were still accumulating gas which should re-start star formation in a red, dead galaxy but wasn’t. This led the team to the supermassive black hole discovery.
Dr Penny said: “Our results are important for astronomy because they potentially impact how we understand galaxy evolution. Supermassive black holes weren’t thought to influence dwarf systems but we’ve shown that isn’t the case. This may well have a big influence on future research as simulations of galaxy formation don’t usually include the heating effect of supermassive black holes in low-mass galaxies, including the dwarf systems we have examined in this work.”
The team of international scientists used data from the Sloan Digital Sky Survey (SDSS), which has a telescope based in New Mexico, to make their observations. Using SDSS’s Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, they were able to map the processes acting on the dwarf galaxies through the star systems’ heated gas, which could be detected. The heated gas revealed the presence of a central supermassive black hole, or active galactic nucleus (AGN), and through MaNGA the team were able to observe the effect that the AGN had on their host dwarf galaxies. | 0.804133 | 3.944416 |
Overcoming interference from a very active young sun-like star, a group of astronomers were able to find what they determined is the youngest exoplanet yet discovered. BD+20 1790b is 35 million years old (Earth is about 100 times older at 4.5 billion years) and is located about 83 light years away from our planet. Previously, the youngest known exoplanet was about 100 million years old. Studying this planet will help our understanding of planetary evolution.
While this new-found planet is young, it is a whopper, at six times the mass of Jupiter. It orbits a young active star at a distance closer than Mercury orbits the Sun.
Most planet-search surveys tend to target much older stars, with ages in excess of a billion years. Young stars usually have intense magnetic fields that generate solar flares and sunspots, which can mimic the presence of a planetary companion and so can make extremely difficult to disentangle the signals of planets and activity.
BD+201790 is a very active star, and astronomers announced last year that it could possibly have a companion. An international collaboration of astronomers, led by Dr. Maria Cruz Gálvez-Ortiz and Dr. John Barnes were able to “weed out” the data to determine the planet was actually there.
“The planet was detected by searching for very small variations in the velocity of the host star, caused by the gravitational tug of the planet as it orbits – the so-called “Doppler wobble technique,” said Gálvez-Ortiz. “Overcoming the interference caused by the activity was a major challenge for the team, but with enough data from an array of large telescopes the planet’s signature was revealed.”
The team has been observing the star for the last five years at different telescopes, including the Observatorio de Calar Alto (Almería, Spain) and the Observatorio del Roque de los Muchachos (La Palma, Spain).
Source: Alpha Galileo | 0.885288 | 3.742536 |
Mark the evenings of February 25th and 26th on your calendar. If clear, head out after sunset and look toward the western sky. There you will see two of the brightest objects in the night sky—the planets Venus and Jupiter—being “sideswiped” by the brightest of all nighttime objects, the Moon. The spectacle will be readily visible with the unaided eye, and a truly fascinating sight in binoculars.
Other than a meteor shower, the occasional bright comet, or an eclipse, most people think of the sky as static and unchanging. But nothing could be further from the truth—everything in the sky is constantly in motion! The most obvious example of this is the slow movement of the stars from east to west due to the daily rotation of the Earth on its axis. And the very word “planet” comes from the Greek for “wanderers,” indicating that ancient skywatchers recognized that these bodies moved in relation to the stars themselves.
Venus and Jupiter are currently slowly drawing closer together each week as they prepare to meet in a spectacular celestial embrace (or “conjunction”) in March that will be covered in the next issue of Sky Talk. Most of this movement is due to Venus rapidly gaining altitude in the sky and catching up to Jupiter. On the evening of February 25th, Venus will be joined by the beautiful crescent Moon to its upper right. The following evening, the Moon will have moved upward (actually eastward in the sky) and to the right of Jupiter. The view on either of these evenings through your Edmund binoculars will be quite a sight! And should you have a rich-field telescope with a very wide field of view such as the Scientifics’ Astroscan Plus, both Moon and planet may actually fit in the same eyepiece field for a brief time. Whether using binoculars or telescope, be sure to notice the “Earthshine” illuminating the dark portion of the Moon itself. As discussed in past Sky Talk installments, this is sunlight from the Pacific Ocean where it’s still daylight reflecting back onto our satellite. (This glow is also visible to the unaided eye.)
Through a telescope at a magnification of about 30x, Venus will appear just over half-full (or slightly gibbous) during February. The best time to observe it is during twilight when the bright sky background cuts down on the glare from this radiant orb, which overpowers the planet in a dark sky. At the same magnification, Jupiter’s four bright Galilean satellites will be visible in constantly changing positions as they orbit the giant planet. And after it passes Venus and Jupiter, the Moon moves out of the scene in its never-ending eastward journey, clipping along at an orbital velocity of over 2,200 miles per hour. Truly, the heavenly canopy above us is not static but rather an ever-changing (and absolutely free) skyshow!
Former assistant editor at Sky & Telescope magazine & author of eight books on stargazing. | 0.887647 | 3.741451 |
Scientists had another eureka moment as water was found on the moon's equator. New analysis of data from the moon mineralogy mapper ( M3) on board Chandrayaan- 1 shows water on the moon is not limited to its polar regions but extends to the equator.
" The new map shows water and hydroxyl ions detected by M3 is more extensive," US geologist Roger Clark and colleagues said at the ongoing 41st lunar and planetary science conference at Woodlands near Houston. Last September, NASA and ISRO scientists had announced the discovery of water molecules in the polar regions of the moon. M3 had also revealed hydroxyl, a molecule consisting of one oxygen atom and one hydrogen atom, in the lunar soil.
Data from instruments on board two NASA spacecraft, Cassini and Deep Impact , had also shown the presence of water and hydroxyl trapped or absorbed in the minerals on the lunar surface. It corroborated the initial M3 find. However, there was a problem. While the other spacecraft indicated the presence of water closer to the equator, the M3 data failed to show that. Scientists said the main reason for the mismatch was conservative processing of the M3 data.
Scientists also found that M3 had not completely covered certain wavelengths that denote the presence of water. So, they constructed a new map on the basis of finer data and it now confirms what Cassini and Deep Impact had indicated there is water close to the equator of the moon too.
Clark, who works with the US geological survey, is part of the team that analysed data from visual and infrared mapping spectrometer on board Cassini which had had a flyby of the moon in 1999 as well as M3.
NASA's Deep Impact spacecraft, en route to the comet Hartley 2, had also observed the moon for calibration. In June last year, it took detailed measurements of light from the north polar regions of the moon. Data from these two experiments had confirmed M3 findings last September.
However, the water found by M3 in the lit areas of the moon was not much. As much as 1,000 water molecule parts per million could be in the lunar soil. That means if you harvested one tonne of the top layer of the moon's surface, you could get as much as 32 ounces ( 946 ml) of water.
But what mini- synthetic aperture radar ( SAR) on board Chandrayaan- 1 found inside the lunar craters on the dark side of the moon was two metres of thick layers of ice, potentially yielding millions of tonnes of water, as NASA claimed. The tonnage, however, was not published in a journal article.
An ISRO spokesperson said the space agency would comment on the new equatorial water find only after Prof J. N. Goswami, the principal scientist of Chandrayaan- 1 , returns from the Houston conference later this week.
Reproduced From Mail Today. Copyright 2010. MTNPL. All rights reserved. (source: yahoo) | 0.82049 | 3.794386 |
Astronomers who thought they'd found a 100-trillion-Sun mass of pure dark matter have come up empty handed. A pair of quasar images that looked like an unusual case of gravitational lensing by such a mass has turned out to be simply a pair of quasars.
Astronomers put lots of effort into finding cosmic gravitational lenses. These are special alignments where a very distant object appears multiple or distorted, because its light is bent by the gravitational field of a foreground mass. One promising prospect was the close pair of quasars Q2345+007A and B in Pisces. These two faint specks, 7.3 arcseconds apart, show spectra with the same large redshift (2.15, corresponding to a distance of about 11 billion light-years) and other spectral features that match very closely. They certainly seemed like two images of a single object.
Their relatively wide separation hinted at something with a lot of gravitational force in the foreground, amounting to some 100 trillion solar masses (about the mass of 100 Milky Ways). But astronomers could see no trace of foreground objects. Was the lensing mass made of pure dark matter, something never before discovered?
The Chandra X-ray Observatory says no. Even though the objects' optical spectra appear the same, their X-ray spectra clearly show different features, proving that they are two separate objects after all. Their identical redshifts probably mean they are a binary pair.
However, the couple is interesting in its own right. Separated by 400,000 light-years or more, they are presumably the black-hole cores of galaxies that we can't see though the quasars' glare. They are probably close enough together that a near-collision stirred up interstellar matter in both galaxies, causing some of it to fall toward the central black holes and light up brilliantly. At least that's the theory. "Because there are so many more quasar pairs than you would expect," says quasar astronomer Chris Kochanek (Harvard-Smithsonian Center for Astrophysics), "it tells you that interactions have to trigger a certain amount of activity" and light up galaxy cores. | 0.872242 | 3.903518 |
Today the European Space Agency (ESA) launched a new high-energy observatory into orbit, setting out upon one of Europe's most ambitious astronomy missions. The International Gamma-Ray Astrophysics Laboratory (Integral) lifted off from the launch facility near Tyuratam, Kazakhstan, at 10:41 a.m. local time. A Russian Proton booster placed Integral into a highly elliptical, 72-hour orbit around the Earth.
The spacecraft carries a battery of four X- and gamma-ray telescopes, as well as a 5-centimeter optical monitor. Gamma-ray photons are too energetic to focus by conventional optics, so instead astronomers use coded-mask telescopes. These employ a pattern of holes to cast gamma-ray shadows, which computer software then transforms into images.
The spacecraft's largest coded-mask telescope is IBIS, which has a 1.1-meter aperture and two imagers covering 20,000 to 10 million electron volts in photon energy. This range is comparable to that monitored by the low-energy spectrometers on NASA's defunct Compton Gamma Ray Observatory but with much improved spatial resolution (12 arcminutes). France's Sigma telescope, which flew on the Soviet Union's Granat satellite in 1989, had a similar imaging capability but was a factor of 10 less sensitive. Integral also carries SPI, a high-resolution spectrometer with a 0.7-m aperture, and JEM-X, a pair of imaging 0.53-m telescopes to detect X-rays with energies of 3,000 to 35,000 electron volts. | 0.856404 | 3.249001 |
NASA's Genesis spacecraft returned to Earth this morning but made a crash landing in Utah instead of the planned capture by a precision-flying helicopter stunt pilot.
The homecoming was proceeding as planned up through the capsule's plunge into the atmosphere shortly before 10 a.m. Mountain Daylight Time. But as cameras homed in on the falling capsule, the pictures revealed that neither its drogue parachute nor parafoil had deployed. The capsule fell out of control and hit the desert floor at an estimated 190 miles per hour. The impact cracked the outer sample-return capsule and possibly ruptured the inner science capsule containing the solar-wind collectors.
Genesis was launched on August 8, 2001, and was sent into a "halo orbit" around the L1 Lagrangian point of gravitational equilibrium between the Earth and Sun. From December 2001 until April 2004, the spacecraft gathered particles streaming from the Sun, capturing them using wafers of silicon, sapphire, gold, and diamond. Scientists expected to have about 0.4 milligram of solar-wind material to study. Genesis marked the first of many planned sample-return missions from comets, asteroids, and Mars.
At a press conference held at the US Army Dugway Proving Grounds 2½ hours after the crash, mission personnel explained that the condition of the samples was unknown, but they are hopeful that some science results will be salvaged. The crash site will first be examined to ensure that recovery teams are in no danger from the unfired explosives that would have released the parachutes, or from chemicals in the onboard batteries. Following a physical assessment of the 225-kilogram (500-pound) capsule, the team will decide whether the entire capsule will be moved or only the science container will be extracted. Either way, the collectors are expected to reach a clean room for examination by the end of today.
A mishap review board will be assembled within 72 hours to study the crash. Although there had been some concern about the viability of a key battery in November 2001, the battery was later deemed fine. Nevertheless, if the battery failed, it would not have allowed the parachutes to deploy.
The board's final report could prove key in ensuring the success of future sample-return missions, such as Stardust, which is now on course back to Earth to drop off samples of interplanetary dust and cometary material from Comet Wild 2. Stardust will make its drop — also in Utah — in January 2006.
The reentry of Genesis itself was also the target of intense scrutiny. Scientists from NASA's Ames Research Center flew aboard a US Air Force research jet to watch the artificial meteor with a battery of cameras and spectrometers. The performance of the capsule's thermal-protection shell as it made its 10½-km-per-second reentry will have a direct bearing on future spacecraft designs. | 0.898295 | 3.05052 |
Now is the time of year when the zodiacal light appears in the western sky shortly after twilight. The zodiacal light is a faint ethereal glow rising in the west in a pyramid shape pointing toward the zenith. The zodiacal light gets its name from the glow it makes along the line of the ecliptic in the sky. The ecliptic is the line that the sun, moon and planets follow across the sky. It is also along this line that the zodiac constellations reside, hence the name, zodiacal light.
Putman Mountain Observatory maintains an All Sky Camera that records video of the heavens every night. See the link: All Sky Camera. You can see the zodiacal light in the images the All Sky Camera takes each night after twilight in the late winter and spring. In the All Sky Camera image below, can you see the Milky Way? Can you see Orion? Can you see the zodiacal light rising over the dome of the observatory?
The source of the zodiacal light is interplanetary dust left over from the original nebula from which the solar system was formed. This interplanetary dust lies along the plane of the solar system which is the line of the ecliptic in the sky. The dust is more easily seen when the ecliptic is at a high angle in the sky so that it is illuminated by the sun but far enough outside the glare from the sun. In the diagram below, you can see the interplanetary dust lying along the plane of the solar system and why it is visible in the west during twilight.
The zodiacal light appears like a pyramid extending up from the horizon and leaning toward the line of the ecliptic since the interplanetary dust is in the same plane as the solar system. The zodiacal light is brightest near the sun but can never be seen because it’s lost in the glare from the sun. One of the best times to see the zodiacal light is shortly after twilight in the spring because the Earth blocks the glare from the sun. In the image below, the zodiacal light is outlined in red to show the location of it’s faint glow.
There are a number of requirements for seeing the zodiacal light. First you need an extremely dark sky. The glow from the zodiacal light is much fainter than the Milky Way. Second, there can be no moon present in the sky. The light from the moon will overwhelm the zodiacal light and even the Milky Way. Third, the ecliptic must be high in the sky to make the zodiacal light more visible. This occurs in the western sky after dusk during late winter and spring and in September and October in the eastern sky before dawn.
The image below shows the Zodiacal Light captured with a simple digital camera pointed toward the west from the observatory. Take some time after twilight during the spring and go find the zodiacal light. And remember, turn out the lights! | 0.808354 | 3.454171 |
July 28, 2015 – Colorful new maps of Ceres, based on data from NASA’s Dawn spacecraft, showcase a diverse topography, with height differences between crater bottoms and mountain peaks as great as 9 miles (15 kilometers).
Scientists continue to analyze the latest data from Dawn as the spacecraft makes its way to its third mapping orbit.
“The craters we find on Ceres, in terms of their depth and diameter, are very similar to what we see on Dione and Tethys, two icy satellites of Saturn that are about the same size and density as Ceres. The features are pretty consistent with an ice-rich crust,” said Dawn science team member Paul Schenk, a geologist at the Lunar and Planetary Institute, Houston.
Some of these craters and other features now have official names, inspired by spirits and deities relating to agriculture from a variety of cultures. The International Astronomical Union recently approved a batch of names for features on Ceres.
The newly labeled features include Occator, the mysterious crater containing Ceres’ brightest spots, which has a diameter of about 60 miles (90 kilometers) and a depth of about 2 miles (4 kilometers). Occator is the name of the Roman agriculture deity of harrowing, a method of leveling soil.
A smaller crater with bright material, previously labeled “Spot 1,” is now identified as Haulani, after the Hawaiian plant goddess. Haulani has a diameter of about 20 miles (30 kilometers). Temperature data from Dawn’s visible and infrared mapping spectrometer show that this crater seems to be colder than most of the territory around it.
Dantu crater, named after the Ghanaian god associated with the planting of corn, is about 75 miles (120 kilometers) across and 3 miles (5 kilometers) deep. A crater called Ezinu, after the Sumerian goddess of grain, is about the same size. Both are less than half the size of Kerwan, named after the Hopi spirit of sprouting maize, and Yalode, a crater named after the African Dahomey goddess worshipped by women at harvest rites.
“The impact craters Dantu and Ezinu are extremely deep, while the much larger impact basins Kerwan and Yalode exhibit much shallower depth, indicating increasing ice mobility with crater size and age,” said Ralf Jaumann, a Dawn science team member at the German Aerospace Center (DLR) in Berlin.
Almost directly south of Occator is Urvara, a crater named for the Indian and Iranian deity of plants and fields. Urvara, about 100 miles (160 kilometers) wide and 3 miles (6 kilometers) deep, has a prominent central pointy peak that is 2 miles (3 kilometers) high.
Dawn is currently spiraling toward its third science orbit, 900 miles (less than 1,500 kilometers) above the surface, or three times closer to Ceres than its previous orbit. The spacecraft will reach this orbit in mid-August and begin taking images and other data again.
Ceres, with a diameter of 584 miles (940 kilometers), is the largest object in the main asteroid belt, located between Mars and Jupiter. This makes Ceres about 40 percent the size of Pluto, which NASA’s New Horizons mission flew by earlier this month.
On March 6, 2015, Dawn made history as the first mission to reach a dwarf planet, and the first to orbit two distinct extraterrestrial targets. It conducted extensive observations of Vesta in 2011-2012.
Dawn’s mission is managed by JPL for NASA’s Science Mission Directorate in Washington. Dawn is a project of the directorate’s Discovery Program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team. | 0.842946 | 3.682321 |
The building blocks of matter in our universe were formed in the first 10 microseconds of its existence, according to the currently accepted scientific picture. After the Big Bang about 13.7 billion years ago, matter consisted mainly of quarks and gluons, two types of elementary particles whose interactions are governed by quantum chromodynamics (QCD), the theory of strong interaction. In the early universe, these particles moved (nearly) freely in a quark-gluon plasma.
This is a joint press release of University Muenster and Heidelberg as well as the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt.
Then, in a phase transition, they combined and formed hadrons, among them the building blocks of atomic nuclei, protons and neutrons. In the current issue of the science journal "Nature", an international team of scientists presents an analysis of a series of experiments at major particle accelerators which sheds light on the nature of this transition.
The scientists determined with precision the transition temperature and obtained new insights into the mechanism of cooling and freeze-out of the quark-gluon plasma into the current constituents of matter such as protons, neutrons, and atomic nuclei. The team of researchers consists of scientists from the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, and from the universities of Heidelberg, Münster, and Wroclaw (Poland).
Analysis of experimental results confirm the predicted value of the transition temperature / One hundred and twenty thousand times hotter than the interior of the sun
A central result: The experiments at world-wide highest energy with the ALICE detector at the Large Hadron Collider (LHC) at the research center CERN produce matter where particles and anti-particles coexist, with very high accuracy, in equal amounts, similar to the conditions in the early universe.
The team confirms, with analysis of the experimental data, theoretical predictions that the phase transition between quark-gluon plasma and hadronic matter takes place at the temperature of 156 MeV. This temperature is 120,000 times higher than that in the interior of the sun.
"Snowballs in hell"
The physicists analyzed more precisely the yields of a number of particles and anti-particles. "Our investigations revealed a number of surprizing discoveries. One of them is that light nuclei and their anti-particles are produced at the same temperature as protons and anti-protons, although their binding energies are about 100 times smaller than the energy corresponding to the transition temperature", explains Prof. Dr. Anton Andronic who recently joined the University of Münster from the GSI Helmholtzzentrum für Schwerionenforschung.
The scientists presume that such "loosely bound objects" are formed at high temperature first as compact multi-quark objects which only later develop into the observed light nuclei and anti-nuclei. The existence of such multi-quark states was proposed a long time ago but no convincing evidence was found.
"Confinement": Charm quarks travel freely in the fireball
Another remarkable observation concerns a phenomenon long known but poorly understood: Normally, quarks are confined into the interior of protons and neutrons; isolated quarks have never been observed, a property which scientists describe as "confinement". In the interior of the fireball formed in nuclear collisions at high energy this confinement is lifted (deconfinement). The new study shows that charmonium states such as J/psi mesons, consisting of a pair of charm and anti-charm quarks, are produced far more often at LHC energies compared to observations at lower energies, such as at the "Relativistic Heavy Ion Collider" in the USA.
Because of the higher energy density at LHC the opposite, namely a reduction of J/psi mesons through dissociation was expected. In contradistinction, enhancement was predicted 18 years ago by two of the team members (Prof. Dr. Peter Braun-Munzinger, GSI, and Prof. Dr. Johanna Stachel, Universität Heidelberg) because of deconfinement of the charm quarks. The consequences of the prediction were worked out in detail in a series of publications by the whole team.
The now observed enhanced production of J/psi particles confirms the prediction: J/psi mesons can only be produced in the observed large quantities if their constituents, the charm- and anticharm quarks, can travel freely in the fireball over distances of a trillionth of a centimeter – corresponding to about ten times the size of a proton. "These observations are a first step towards understanding the phenomenon of confinement in more detail", underlines Prof. Dr. Krzysztof Redlich of the University of Wroclaw (Poland).
Experiments at CERN and at Brookhaven National Laboratory
The data were obtained during several years of investigations in the framework of the experiment "ALICE" at the Large Hadron Collider accelerator at the research center CERN near Geneva. In "ALICE", scientists from 41 countries investigated in collisions between two lead nuclei the state of the universe within microseconds after the Big Bang. The highest ever man-made energy densities are produced in such collisions.
These result in the formation of matter (quarks and gluons) as it existed at that time in the early universe. In each head-on collision more than 30,000 particles (hadrons) are produced which are then detected in the ALICE experiment. The actual study also used data from experiments at lower energy accelerators, the "Super Proton Synchrotron" at CERN and the "Relativistic Heavy Ion Collider" at the US-Brookhaven National Laboratory on Long Island, New York.
The investigations were supported in the framework of the "Collaborative Research Center" 1225 "Isolated quantum systems and universality under extreme conditions (ISOQUANT)" by the German Research Foundation (DFG). Furthermore, they were supported by the Polish National Science Center (NCN) (Maestro grant DEC-2013/10/A/ST2/00106).
Relativistic nuclear collisions at GSI
The investigation of relativistic nuclear collisions has a long tradition at GSI, first at the SIS18 accelerator, then at the CERN SPS. Until 1995 the group was led by Prof. Dr. Rudolf Bock, from 1996 on by Prof. Dr. Peter Braun-Munzinger.
The ALICE group at GSI is since 1993 member of the ALICE collaboration and has played a leading role in the design and construction of the experiment as well as in operation and analysis. Prof. Braun-Munzinger had, as project leader of the ALICE Time Projection Chamber TPC as well as in the design and construction of the ALICE Transition Radiation Detector TRD, together with his team an important impact on the whole successful experiment and is involved in ALICE data analysis as well as in the development of projects for the future of ALICE. Since 2011 Prof. Dr. Silvia Masciocchi leads the ALICE GSI group.
The phenomenological investigations towards interpretation of the ALICE data which are central to this Nature publication were performed within the framework of the ExtreMe Matter Institute EMMI, currently led by Prof. Braun-Munzinger.
The results reported in the Nature publication are also trail blazing for research at the future FAIR facility: especially the results on the production of light nuclei and hyper-nuclei open new perspectives for the CBM experiment at FAIR.
Andronic A., Braun-Munzinger P., Redlich K. und Stachel J. (2018): Decoding the phase structure of QCD via particle production at high energy. Nature Sep. 20, 2018 issue; DOI: 10.1038/s41586-018-0491-6
Dr. Ingo Peter | idw - Informationsdienst Wissenschaft
The broken mirror: Can parity violation in molecules finally be measured?
04.06.2020 | Johannes Gutenberg-Universität Mainz
K-State study reveals asymmetry in spin directions of galaxies
03.06.2020 | Kansas State University
In meningococci, the RNA-binding protein ProQ plays a major role. Together with RNA molecules, it regulates processes that are important for pathogenic properties of the bacteria.
Meningococci are bacteria that can cause life-threatening meningitis and sepsis. These pathogens use a small protein with a large impact: The RNA-binding...
An analysis of more than 200,000 spiral galaxies has revealed unexpected links between spin directions of galaxies, and the structure formed by these links...
Two prominent X-ray emission lines of highly charged iron have puzzled astrophysicists for decades: their measured and calculated brightness ratios always disagree. This hinders good determinations of plasma temperatures and densities. New, careful high-precision measurements, together with top-level calculations now exclude all hitherto proposed explanations for this discrepancy, and thus deepen the problem.
Hot astrophysical plasmas fill the intergalactic space, and brightly shine in stellar coronae, active galactic nuclei, and supernova remnants. They contain...
In living cells, enzymes drive biochemical metabolic processes enabling reactions to take place efficiently. It is this very ability which allows them to be used as catalysts in biotechnology, for example to create chemical products such as pharmaceutics. Researchers now identified an enzyme that, when illuminated with blue light, becomes catalytically active and initiates a reaction that was previously unknown in enzymatics. The study was published in "Nature Communications".
Enzymes: they are the central drivers for biochemical metabolic processes in every living cell, enabling reactions to take place efficiently. It is this very...
Early detection of tumors is extremely important in treating cancer. A new technique developed by researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from normal tissue. The work is published May 25 in the journal Nature Nanotechnology.
researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from...
19.05.2020 | Event News
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04.06.2020 | Life Sciences | 0.807946 | 4.01235 |
Gravity Waves in Mars’ Atmosphere
Today we have a guest post Dr. Nicholas G. Heavens. He is a Research Assistant Professor of Planetary Science at Hampton University in Hampton, Virginia. He studies the weather of present day Mars, the climate of late Paleozoic Earth, and the atmospheric evolution of Earth-like planets outside the Solar System. He is a member of the Mars Climate Sounder science team.
Dear Explorers of the Fourth Planet,
Chances are, at some point, you have found yourself by a still body of water on a rainy day. Entranced by the smooth surface of this lake or pond, you began to feel the rain fall on your head and shoulders. And as the rain fell on the water, you noticed circular ripples radiating out from each raindrop and moving toward the shore.
Those ripples are a particularly beautiful and elegant example of a type of wave known as a gravity wave (or sometimes buoyancy wave). The raindrop’s impact depresses the surface of the water, upsetting the balance between the force of gravity and the pressure exerted by the water. Water then moves into the hole to restore this balance, creating a further imbalance that spreads the energy of the impact (but not the water itself) outward as circular rings.
Gravity waves in water are a familiar sight in our everyday lives, but gravity waves are common in atmospheres as well, including Mars’s. On average, gravity and air pressure in Mars’s atmosphere are in balance, meaning that less dense air is higher in the atmosphere than more dense air. However, in some situations, denser air can be forced over less dense air, resulting in gravity waves that can propagate to higher altitudes and grow in amplitude as they do so. Some of those waves can be quite inconvenient, since they make up much of aircraft turbulence.
When you look at Planet Four images, you stare at high-resolution, mostly cloudless images of Mars near its poles. What I want to show you today is what might be happening in the atmosphere above, as seen in cloudy, low-resolution images of Mars. It is common to see visible indications of gravity waves in the winter hemisphere around 45 degrees south, but gravity waves are likely active at other times and places.
In the first image, do you see circular, whitish ripples near the center of the image? Something analogous to raindrops dropping in a pond has happened there. In the parts of the waves that correspond to rising air, water vapor is cooled and condenses into ice to clouds that trace out the waves.
In the second image, the wave fronts are not strongly curved and appear to be radiating in one direction, probably indicating that a strong wind is affecting the waves. In each case, the wavelength of the waves can be easily measured, around 40 km in the first case and around 20 km in the second case. The source of the first set of waves is unclear (at least to me). The source of the second set of waves is probably the interaction of dense cold air from the pole moving over less dense warmer air at lower latitudes. In some images, the source of the waves can be traced to wind dropping down into a crater.
Studying gravity waves can tell us much about how Mars’s atmosphere works from bottom to top. Future Martian glider pilots also might appreciate knowing when they occur and the conditions they will create. But I will admit that my interest in Mars’s atmospheric gravity waves continues to be fed by the disturbing beauty they bring to Mars’s thin atmosphere. | 0.830061 | 3.91417 |
About this book
Much of what is known about the universe comes from the study of celestial shadows—eclipses, transits, and occultations. The most dramatic are total eclipses of the Sun, which constitute one of the most dramatic and awe-inspiring events of nature. Though once a source of consternation or dread, solar eclipses now lead thousands of amateur astronomers and eclipse-chasers to travel to remote points on the globe to savor their beauty and the adrenaline-rush of experiencing totality, and were long the only source of information about the hauntingly beautiful chromosphere and corona of the Sun.
Long before Columbus, the curved shadow of the Earth on the Moon during a lunar eclipse revealed that we inhabit a round world. The rare and wonderful transits of Venus, which occur as it passes between the Earth and the Sun, inspired eighteenth century expeditions to measure the distance from the Earth to the Sun, while the recent transits of 2004 and 2012 were the most widely observed ever--and still produced results of great scientific value. Eclipses, transits and occultations involving the planets, their satellites, asteroids and stars have helped astronomers to work out the dimensions and shapes of celestial objects—even, in some cases, hitherto unsuspected rings or atmospheres—and now transits have become leading tools for discovering and analyzing planets orbiting other stars.
This book is a richly illustrated account of these dramatic and instructive astronomical phenomena. Westfall and Sheehan have produced a comprehensive study that includes historical details about past observations of celestial shadows, what we have learned from them, and how present-day observers—casual or serious—can get the most out of their own observations.
- DOI https://doi.org/10.1007/978-1-4939-1535-4
- Copyright Information Springer-Verlag New York 2015
- Publisher Name Springer, New York, NY
- eBook Packages Physics and Astronomy
- Print ISBN 978-1-4939-1534-7
- Online ISBN 978-1-4939-1535-4
- Series Print ISSN 0067-0057
- Series Online ISSN 2214-7985
- Buy this book on publisher's site | 0.842634 | 3.561796 |
Lots of towns hold a polar plunge fundraising event in the winter. Duluth, Minnesota’s version, where participants jump in Lake Superior every February, might just be the coldest. Comet Lovejoy’s a season behind, but sure enough, it’s following suit, diving deep into the dark waters of the north celestial pole this month.
I dropped in on our old friend last night, when it glowed only 8° from the North Star. In 8×40 binoculars, the comet was faintly visible as a hazy blob of light with a brighter center. Not a sight to knock you over, but the fact that this comet is still visible in binoculars after so many months makes it worthwhile to seek out. Moonless skies for the next 10-11 nights means lots of opportunities.
Unless a new comet is discovered, Lovejoy will continue to remain the only “bright” comet visible from mid-northern latitudes for some time. There’s a tiny chance Comet C/2014 Q1 PanSTARRS will wax bright enough to see in twilight in early July, but it will be very low in the northwestern sky at dusk and visible for a few nights at most. Only C/2013 US10 Catalina offers the chance for a naked eye / binocular appearance, when it re-emerges from the solar glare in the latter half of November in the morning sky.
Southern hemisphere observers have more to smile about with Comet C/2015 G2 MASTER currently flaunting its fluff at magnitude +6.6 or just under the naked eye limit. They’ll also get a far better view of C/2014 Q1 PanSTARRS come this July and August.
Through a telescope, Lovejoy still shows off a round, 6 arc minute diameter coma (one-fifth as wide as a full moon) and a denser, brighter core highlighted by a starlike false nucleus. We call it false because the true comet nucleus, probably no more than a few kilometers across, hides within a dusty cocoon of its own making. Only spacecraft have been able to get close enough for a clear view of comet nuclei. Each shows a unique and usually non-spherical shape because comets aren’t massive enough for their own self-gravity to crush them into spheres the way larger moons and planets do. If you’re a single object and big, being spherical comes naturally.
In my 15-inch (37-cm) telescope a faint wisp of a tail poked from the coma to the north. Looking at the map, you can see the comet’s headed due north through Cepheus toward Polaris, the North Star. Each passing night, it draws closer to the sky’s celestial pivot point, missing it by just 1° on the evenings of May 27 and 28. Closest approach to the north celestial pole, which marks the spot in the sky toward which Earth’s north polar axis currently points, occurs on May 29 with a separation of 54 arc minutes or just under a degree.
Finding Polaris is easy. Just draw a line through the two stars at the end of of the Big Dipper’s Bowl toward the horizon. The first similarly bright star you run into is the North Star. Using the map, you can navigate from Polaris to the fuzzy comet with either binoculars or telescope. | 0.861479 | 3.631603 |
Spectacular jets powered by the gravitational energy of a supermassive black hole in the core of the elliptical galaxy Hercules A illustrate the combined imaging power of two of astronomy’s cutting-edge tools, the Hubble Space Telescope’s Wide Field Camera 3, and the recently upgraded Karl G. Jansky Very Large Array (VLA) radio telescope in west-central New Mexico.
Some two billion light-years away, the yellowish elliptical galaxy in the center of the image appears quite ordinary as seen by Hubble in visible wavelengths of light. The galaxy harbors a 2.5-billion-solar-mass central black hole that is 1,000 times more massive than the black hole in our Milky Way. But the innocuous-looking galaxy, also known as 3C 348, has long been known as the brightest radio-emitting object in the constellation Hercules. Emitting nearly a billion times more power in radio wavelengths than our Sun, the galaxy is one of the brightest extragalactic radio sources in the entire sky.
The VLA radio data reveal enormous, optically invisible jets that, at one-and-a-half million light-years long, dwarf the visible galaxy from which they emerge. The jets are very-high-energy plasma beams, subatomic particles and magnetic fields shot at nearly the speed of light from the vicinity of the black hole. The outer portions of both jets show unusual ring-like structures suggesting a history of multiple outbursts from the supermassive black hole at the center of the galaxy.
The innermost parts of the jets are not visible because of the extreme velocity of the material; relativistic effects confine all the light to a narrow cone aligned with the jets, so that light is not seen by us.
The entire radio source is surrounded by a very hot, X-ray-emitting cloud of gas, not seen in this optical-radio composite.
Hubble’s view of the field also shows a companion elliptical galaxy very close to the center of the optical-radio source, which may be merging with the central galaxy. Several other elliptical and spiral galaxies that are visible in the Hubble data may be members of a cluster of galaxies. Hercules A is by far the brightest and most massive galaxy in the cluster.
National Radio Astronomy Observatory, Charlottesville, VA
Space Telescope Science Institute, Baltimore, MD
National Radio Astronomy Observatory, Socorro, NM | 0.863304 | 3.973503 |
Ever since the Cassini probe arrived at Saturn in 2004, it has revealed some startling things about the planet’s system of moons. Titan, Saturn’s largest moon, has been a particular source of fascination. Between its methane lakes, hydrocarbon-rich atmosphere, and the presence of a “methane cycle” (similar to Earth’s “water cycle”), there is no shortage of fascinating things happening on this Cronian moon.
As if that wasn’t enough, Titan also experiences seasonal changes. At present, winter is beginning in the southern hemisphere, which is characterized by the presence of a strong vortex in the upper atmosphere above the south pole. This represents a reversal of what the Cassini probe witnessed when it first started observing the moon over a decade ago, when similar things were happening in the northern hemisphere.
These finding were shared at the joint 48th meeting of the American Astronomical Society’s Division for Planetary Sciences and 11th European Planetary Science Congress, which took place from Oct 16th to 21st in Pasadena, California. As the second joint conference between these bodies, the goal of this annual meeting is to strengthen international scientific collaboration in the field of planetary science.
During the course of the meeting, Dr. Athena Coustenis – the Director of Research (1st class) with the National Center for Scientific Research (CNRS) in France – shared the latest atmospheric data retrieved by Cassini. As she stated:
“Cassini’s long mission and frequent visits to Titan have allowed us to observe the pattern of seasonal changes on Titan, in exquisite detail, for the first time. We arrived at the northern mid-winter and have now had the opportunity to monitor Titan’s atmospheric response through two full seasons. Since the equinox, where both hemispheres received equal heating from the Sun, we have seen rapid changes.”
Scientists have been aware of seasonal change on Titan for some time. This is characterized by warm gases rising at the summer pole and cold gases settling down at the winter pole, with heat being circulated through the atmosphere from pole to pole. This cycle experiences periodic reversals as the seasons shift from one hemisphere to the other.
In 2009, Cassini observed a large scale reversal immediately after the equinox of that year. This led to a temperature drop of about 40 °C (104 °F) around the southern polar stratosphere, while the northern hemisphere experienced gradual warming. Within months of the equinox, a trace gas vortex appeared over the south pole that showed glowing patches, while a similar feature disappeared from the north pole.
A reversal like this is significant because it gives astronomers a chance to study Titan’s atmosphere in greater detail. Essentially, the southern polar vortex shows concentrations of trace gases – like complex hydrocarbons, methylacetylne and benzene – which accumulate in the absence of UV light. With winter now upon the southern hemisphere, these gases can be expected to accumulate in abundance.
As Coustenis explained, this is an opportunity for planetary scientists to test out their models for Titan’s atmosphere:
“We’ve had the chance to witness the onset of winter from the beginning and are approaching the peak time for these gas-production processes in the southern hemisphere. We are now looking for new molecules in the atmosphere above Titan’s south polar region that have been predicted by our computer models. Making these detections will help us understand the photochemistry going on.”
Previously, scientists had only been able to observe these gases at high northern latitudes, which persisted well into summer. They were expected to undergo slow photochemical destruction, where exposure to light would break them down depending on their chemical makeup. However, during the past few months, a zone of depleted molecular gas and aerosols has developed at an altitude of between 400 and 500 km across the entire northern hemisphere .
This suggests that, at high altitudes, Titan’s atmosphere has some complex dynamics going on. What these could be is not yet clear, but those who have made the study of Titan’s atmosphere a priority are eager to find out. Between now and the end of Cassini mission (which is slated for Sept. 2017), it is expected that the probe will have provided a complete picture of how Titan’s middle and upper atmospheres behave.
By mission’s end, the Cassini space probe will have conducted more than 100 targeted flybys of Saturn. In so doing, it has effectively witnessed what a full year on Titan looks like, complete with seasonal variability. Not only will this information help us to understand the deeper mysteries of one of the Solar System’s most mysterious moons, it should also come in handy if and when we send astronauts (and maybe even settlers) there someday!
Further Reading: Europlanet | 0.816049 | 3.928572 |
In this both suggestive and interesting VIS image, taken by the NASA - Mars Odyssey Orbiter on April, 2nd, 2004, and during its 10.201st orbit around the Red Planet, we can see a small portion of the Martian Region known as Coprates Chasma (---> the "Coprates' Abyss"): a huge and (relatively) flat-floored Canyon, located in in the Coprates Quadrangle of Mars, and centered at 13,4° South Latitude and 61,4° West Longitude.
Coprates Chasma is part, as you should already know, of the Great Valles Marineris Canyon System; it is approx. 966 Km (such as about 599,886 miles) long and it was so named after a so-called "Classical Albedo Feature".
Latitude (centered): 15,2593° South
Longitude (centered): 303,7780° East
This image (which is an Original Mars Odyssey Orbiter falsely colored and Map-Projected frame published on the NASA - Planetary Photojournal with the ID n. PIA 19755) has been additionally processed, magnified to aid the visibility of the details, contrast enhanced and sharpened, Gamma corrected and then re-colorized in Absolute Natural Colors (such as the colors that a normal 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. | 0.851421 | 3.031895 |
Tethys – Learn All About The Frozen Ice Moon
Frozen Ice Ball!
Discovered in 1684 by Giovanni Cassini, Tethys is the 16th largest moon and has the lowest density of a major moon in the solar system! Saturn’s 5th largest moon is composed of water-ice, is heavily cratered, scared by a large chasm, marked with mysterious red streaks and is Saturn’s second-brightest moon after Enceladus.
Fast Summary Facts About Tethys!
- Discovered: March 21st 1684, by Giovanni Cassini
- Name: From Greek mythology, Tethys is the mythical sister of Kronos (Saturn in Roman)
- Size: Diameter of 1,060 kilometres (660 miles)
- Moon Rank: 16th Largest in the solar system
- Orbit: Prograde and Circular
- Orbit Radius: 294,600 km (183,060 miles)
- Orbital Period: 1 Day, 21 Hours, 18 Minutes
- Orbital Speed: 11.35 km/s
- Density: 0.97 g/cm3
- Surface Temperature: -187 °C (86 K)
- Surface: Water-ice
- Atmosphere: Tenuous (exosphere)
More Facts About Saturn’s Frozen Moon Tethys!
- Tethys was one of four Saturnian moons to be discovered by Giovanni Cassini (along with Dione, Rhea and Iapetus).
- Despite the moon being discovered in 1684, and initially being called Saturn III (being the 3rd moon from Saturn), it wasn’t until 1847 that its name was changed to Tethys to avoid confusion after additional moons around Saturn were discovered.
- Tethys is similar to the neighbouring moons Rhea and Dione; they are all small, cold, cratered and airless bodies.
- Like all but two of Saturn’s major moons, Tethys is ‘tidally locked’ to Saturn as it orbits; meaning the same face of Tethys always faces Saturn. This is similar to Earth’s Moon!
- Tethys also shares its orbit with two much smaller trojan moons that are gravitationally bound at Tethys’ Lagrangian points; the trojan moon Telesto is ahead (L4) and Calypso behind (L5) by 60° respectively.
- Tethys is locked in resonance with the nearby inner moon Mimas, with these tidal (and rotational forces) squashing Tethys into the irregular shape of a triaxial ellipsoid!
- Tethys’ density is 0.97 times that of liquid water which suggests Tethys’ is composed of almost entirely water-ice and a small amount of rocky material!
- The small frozen moon has a mass less than 1% of Earth’s Moon.
- Tethys’ high water-ice content is evident from its high reflectivity (Albedo) and is the second brightest Saturnian moon after Enceladus.
- Images from the Cassini space probe also revealed 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 ‘sand-blasted’ with young icy dust from Saturn's E-ring; formed from tiny particles ejected from Enceladus’ Tiger Stripes!
- Two major features dominate the cratered frozen geology of Tethys;
- The 445 km (275 miles) wide Odysseus impact crater
- And the valley called Ithaca Chasma which is 100 km wide, up to 5 km deep and extends for nearly 2000 km (which likely created as Tethys froze and expanded, cracking the frozen shell)
- A feature unique to Tethys is a series of curved red streaks on the moon's surface. They are a few kilometres wide and several hundred kilometres long. The red streaks are among the most unusual colour features found anywhere on Saturn's moons by the Cassini spacecraft. Their origin remaining a mystery. Weird isn’t it?! | 0.835764 | 3.597929 |
Apart from a billion Milky Way stars, ESA’s Gaia spacecraft also observes extragalactic objects. Its automated alert system notifies astronomers whenever Gaia spots a transient event. A team of astronomers have found out that by tweaking the existing automated system, Gaia can be used to detect hundreds of peculiar transients in the centres of galaxies. They found about 480 transients over a period of about a year. Their new method will be implemented in the system as soon as possible allowing astronomers to determine the nature of these events. The findings will be published in the November issue of MNRAS.
In 2013, ESA launched its Gaia spacecraft to measure the location of a billion stars in our Milky Way and tens of millions of galaxies. Each position on the sky enters Gaia’s view once every month, for a total of about seventy times during the mission. This allows the spacecraft to spot transient events, such as supermassive black holes ripping stars apart or stars exploding as a supernova. Gaia will notice a change in brightness when it returns to the same patch of sky a month later. A team of astronomers from SRON, Radboud University and the University of Cambridge now find nearly five hundred transients occurring in the centres of galaxies over a period of one year.
Astronomers Zuzanna Kostrzewa-Rutkowska, Peter Jonker (both affiliated with SRON and Radboud University), Simon Hodgkin and others searched the Gaia database for transient events around the nuclei of galaxies in the period between July 2016 and June 2017. They used a galaxy catalogue—from the Sloan Digital Sky Survey Release 12— and a custom-made mathematical tool. The new tool allows the researchers to identify rare luminous events coming from galactic centers. They dug up 480 events, of which only five were picked up before by the alert system.
Study previously invisible supermassive black holes
Rapidly alerting the astronomical community is key for many of the events found. For about one hundred transients nothing out of the ordinary was observed by Gaia the month before and the month after detection, indicating that the event leading to the enhanced emission of light was short. ‘Such events have great value because they could allow astronomers to study for a brief period previously invisible supermassive black holes,’ says Jonker. ‘Especially the short-duration events could point us to the location of the so far elusive intermediate-mass black holes ripping stars apart.’
The leading explanation for most events is that supermassive black holes residing in the nuclei of galaxies suddenly become much more active as the amount of gas falling into the black hole surges and lights up the close environment of the black hole. This fresh fuel may be extracted from a star which is ripped apart by the enormous gravitational pull of the black hole.
Decipher the nature of the new transients
Peter Jonker, with Zuzanna Kostrzewa-Rutkowska and others from his group, has recently started a dense campaign to decipher the nature of the 480 new transients using the La Palma-based William Herschel Telescope.
Publication: Z. Kostrzewa-Rutkowska, P.G. Jonker, S.T. Hodgkin, L. Wyrzykowski, M. Fraser, D.L. Harrison, G. Rixon, A. Yoldas, F. van Leeuwen, A. Delgado, M. van Leeuwen, Gaia transients in galactic nuclei. Monthly Notices of the Royal Astronomical Society, Volume 481, Issue 1, 21 November | 0.922733 | 4.013231 |
For London’s Jenni Sparks, it can take months to make a city map. And that’s just the planning process, in which the 25-year-old illustrator roams around checking out corners, snapping photos, watching documentaries, and interviewing locals.
See on Scoop.it – Miscellaneous
In the dusty sky toward the constellation Taurus and the Orion Arm of our Milky Way Galaxy, this broad mosaic follows dark and faint reflection nebulae along the region’s fertile molecular cloud. The six degree wide field of view starts with long dark nebula LDN 1495 stretching from the lower left, and extends beyond the (upside down) bird-like visage of the Baby Eagle Nebula, LBN 777, at lower right. Small bluish reflection nebulae surround scattered fainter Taurus stars, sights often skipped over in favor of the constellation’s better known, brighter celestial spectacles. Associated with the young, variable star RY Tau, the yellowish nebula VdB 27 is toward the upper left. Only 400 light-years or so distant, the Taurus molecular cloud is one of the closest regions of low-mass star formation. At that distance this dark vista would span over 40 light-years.
from NASA http://ift.tt/1K7yTsl
NGC 6240 offers a rare, nearby glimpse of a cosmic catastrophe in its final throes. The titanic galaxy-galaxy collision takes place a mere 400 million light-years away in the constellation Ophiuchus. The merging galaxies spew distorted tidal tails of stars, gas, and dust and undergo fast and furious bursts of star formation. The two supermassive black holes in the original galactic cores will also coalesce into a single, even more massive black hole and soon, only one large galaxy will remain. This dramatic image of the scene is a composite of narrowband and near-infrared to visible broadband data from Hubble’s ACS and WPC3 cameras, a view that spans over 300,000 light-years at the estimated distance of NGC 6240.
from NASA http://ift.tt/1FyeyfY
It was one of the quietest nights of aurora in weeks. Even so, in northern- Iceland during last November, faint auroras lit up the sky every clear night. The featured 360-degree panorama is the digital fusion of four wide-angle cameras each simultaneously taking 101 shots over 42 minutes. In the foreground is serene Lake Myvatn dotted with picturesque rock formations left over from ancient lava flows. Low green auroras sweep across the sky above showing impressive complexity near the horizon. Stars far in the distance appear to show unusual trails — as the Earth turned — because early exposures were artificially faded.
from NASA http://ift.tt/1ERQm3t
Like a pearl, a white dwarf star shines best after being freed from its shell. In this analogy, however, the Sun would be a mollusk and its discarded hull would shine prettiest of all! In the above shell of gas and dust, the planetary nebula designated NGC 2440, contains one of the hottest white dwarf stars known. The glowing stellar pearl can be seen as the bright dot near the image center. The portion of NGC 2440 shown spans about one light year. The center of our Sun will eventually become a white dwarf, but not for another five billion years. The above false color image was captured by the Hubble Space Telescope in 1995. NGC 2440 lies about 4,000 light years distant toward the southern constellation Puppis.
from NASA http://ift.tt/1PNOVt1
This close-up from the Mars Reconnaissance Orbiter’s HiRISE camera shows weathered craters and windblown deposits in southern Acidalia Planitia. A striking shade of blue in standard HiRISE image colors, to the human eye the area would probably look grey or a little reddish. But human eyes have not gazed across this terrain, unless you count the eyes of NASA astronauts in the scifi novel The Martian by Andy Weir. The novel chronicles the adventures of Mark Watney, an astronaut stranded at the fictional Mars mission Ares 3 landing site corresponding to the coordinates of this cropped HiRISE frame. For scale Watney’s 6-meter-diameter habitat at the site would be about 1/10th the diameter of the large crater. Of course, the Ares 3 landing coordinates are only about 800 kilometers north of the (real life) Carl Sagan Memorial Station, the 1997 Pathfinder landing site.
from NASA http://ift.tt/1IDwRmz
In this sharp snapshot, the Solar System’s largest moon Ganymede poses next to Jupiter, the largest planet. Captured on March 10 with a small telescope from our fair planet Earth, the scene also includes Jupiter’s Great Red Spot, the Solar System’s largest storm. In fact, Ganymede is about 5,260 kilometers in diameter. That beats out all three of its other fellow Galilean satellites, along with Saturn’s Moon Titan at 5,150 kilometers and Earth’s own Moon at 3,480 kilometers. Though its been shrinking lately, the Great Red Spot’s diameter is still around 16,500 kilometers. Jupiter, the Solar System’s ruling gas giant, is about 143,000 kilometers in diameter at its equator. That’s nearly 10 percent the diameter of the Sun.
from NASA http://ift.tt/1KQ6A1D | 0.921186 | 3.286462 |
Betelgeuse is one of the brightest and most easily recognisable stars in the night sky. It sits in the constellation of Orion and is visibly red. That’s because Betelgeuse is a luminous, red supergiant about 650 light years away.
And it is huge. If Betelgeuse sat at the centre of the Solar System, it would engulf, Mercury, Venus, Earth, Mars and the asteroid belt. In fact, this star is so big, that it is one of just a few stars that Earth-bound telescopes can see as a disc.
But there is one basic fact about Betelgeuse that astronomers have never been able to gauge accurately. Nobody knows its mass.
The main way of working out an astronomical object’s mass is to look at the objects that orbit it, since astronomers can use the orbital period to work out the mass. That has allowed them to work out the mass of all kinds of objects such as binary star systems, exoplanets and even entire galaxies.
But Betelgeuse doesn’t have a companion that astronomers can see. So they’ve had to rely on other ways to infer the mass.
One is to create a model of the way stars form and evolve and then work out how heavy a star like Betelgeuse ought to be. The answer according to this method turns out to be about 20 solar masses.
Another way is to measure the light the star produces which is the result of conditions at the star surface. This reveals the strength of gravity there. Combining this with measurements of the star’s radius gives a mass. The best answer for Betelgeuse turns out to be about 10 solar masses.
Clearly, these two methods do not agree, which is troubling for astrophysicists.
So Hilding Neilson at the University of Bonn in Germany and a few pals have come up with a new method. They’ve looked at Betelgeuse as a disc and measured how it appears to darken towards is edges, a well known effect that can be described in mathematical models.
In fact, so-called limb darkening models produce a relation between the amount of limb darkening and the ratio of the radius and mass.
Given that these guys know Betelgeuse’s radius and also its the limb-darkening, they’ve plugged the numbers in and come up with a value for the mass. The answer (drum roll) is about 12 solar masses, give or take a few.
So Betelgeuse really is about ten times bigger than the Sun.
Well, maybe. To be frank there’s no reason to think this number is much more reliable than the others. That’s because of uncertainty over Betelgeuse’s exact distance (and hence its measured radius) and also uncertainty over the accuracy of the mathematical model.
But if other astronomers can make a better fist of these, who knows how accurately they can measure Betelgeuse’s mass?
Ref: arxiv.org/abs/1109.4562: Weighing Betelgeuse: Measuring The Mass Of α Orionis From Stellar Limb-Darkening | 0.864224 | 4.019313 |
Flowing water on Mars:
Yesterday's 'mystery solved' release from NASA seems to point to a certain kind of dark feature on the Martian surface being due to liquid water, stabilised against freezing in the Martian cold, or evaporating in the thin martian air, by the naturally occurring perchlorate salts in the Martian soil. It's a process that occurs on earth (well, similar to) and keeps a very strange lake called 'Don Juan Pond in Antarctica filled.
|Above: Don Juan Pond, Antarctica, is the saltiest lake in the world - it never freezes, not even in the - 50 degrees Celsius of Antarctic winter. Courtesy of the British Antarctic Survey.|
Still others point out that the water in these RSL's will be incredibly salty - maybe too salty for even the toughest extremophiles to drink. But it's still (in my opinion) a good find, and it shows us a (slightly!) friendlier side to the red planet. But don't look to me for the answers, here's the video of the conference (above) - judge for yourselves!
Parts of Africa, the America's, and the Atlantic suffered a radio blackout yesterday, as a result of a solar flare.The map below shows the most severely affected areas. This isn't an unusual event, and although really big solar events have been known to knock out power grids, there doesn't seem to be any danger of that happening here.
It seems that, for a while now, ESA's Rosetta spacecraft has been exploring not one comet but two - The famous double-lobed shape of comet 67-P is due to it actually being two comets stuck together:“It is clear from the images that both lobes have an outer envelope of material organised in distinct layers, and we think these extend for several hundred metres below the surface,” says Matteo Massironi, lead author from the University of Padova, Italy, and an associate scientist of the OSIRIS team.
“You can imagine the layering a bit like an onion, except in this case we are considering two separate onions of differing size that have grown independently before fusing together.”
|Above: Two infographics from ESA, showing the layering on Comet 67-P| | 0.858058 | 3.112562 |
NASA launching twin moon probes to measure gravity
Four decades after landing men on the moon, NASA is returning to Earth's orbiting companion, this time with a set of robotic twins that will measure lunar gravity while chasing one another in circles.
By creating the most precise lunar gravity map ever, scientists hope to figure out what's beneath the lunar surface, all the way to the core. The orbiting probes also will help pinpoint the best landing sites for future explorers, whether human or mechanical.
Near-identical twins Grail-A and Grail-B - short for Gravity Recovery and Interior Laboratory - are due to blast off Thursday aboard an unmanned rocket.
Although launched together, the two washing machine-size spacecraft will separate an hour into the flight and travel independently to the moon.
It will be a long, roundabout trip - three to four months - because of the small Delta II rocket used to boost the spacecraft. NASA's Apollo astronauts used the mighty Saturn V rocket, which covered the approximately 240,000 miles to the moon in a mere three days.
NASA's Grail twins will travel more than 2 million miles to get to the moon under this slower but more economical plan.
The mission, from start to finish, costs $496 million.
The moon's appeal is universal.
"Nearly every human who's every lived has looked up at the moon and admired it," said Massachusetts Institute of Technology planetary scientist Maria Zuber, Grail's principal investigator. "The moon has played a really central role in the human imagination and the human psyche."
Since the Space Age began in 1957, 109 missions have targeted the moon, 12 men have walked its surface during six landings, and 842 pounds of rock and soil have been brought back to Earth and are still being analyzed.
Three spacecraft currently are orbiting the moon and making science observations. A plan to return astronauts to the moon was nixed in favor of an asteroid and Mars.
Despite all the exploration, scientists still don't know everything about the moon, Zuber noted. For example, its formation still generates questions - Grail's findings should help explain its origin - and its far side is still mysterious.
"You would think having sent many missions to the moon we would understand the difference between the near side and the far side, but in fact we don't," she said.
Recent research suggests Earth may have had a second smaller moon that collided with our present moon, producing a mountainous region. The Grail mission may help flush out that theory, Zuber said.
Grail-A will arrive at the moon on New Year's Eve, followed by Grail-B on New Year's Day. They will go into orbit around the lunar poles and eventually wind up circling just 34 miles above the surface.
For nearly three months, the spacecraft will chase one another around the moon, meticulously flying in formation. The distance between the two probes will range from 40 miles to 140 miles. Radio signals bouncing between the twins will provide their exact locations, even on the far side of the moon.
Scientists will be able to measure even the slightest variations in the gap between orbiting Grail-A and Grail-B - every single second. These subtle changes will indicate shifting masses below or at the lunar surface: mountains in some places, enormous lava tubes and craters in others.
The moon actually has the most uneven gravitational field in the solar system, according to NASA. The moon's gravity is about one-sixth Earth's pull.
"We measure the velocity change between the two spacecraft to a couple of fractions of a tenth of a micron per second. It is an extremely accurate measurement that has to be made," Zuber said.
A tenth of a micron is about half the size of a red blood cell.
By the time their science mission ends in late spring, Grail-A and Grail-B will be within 10 miles of the lunar surface. Barring a change in plans, they will crash into the moon.
Each spacecraft holds one science instrument- for sending and receiving radio signals between the two - as well as a digital video camera system, MoonKAM, intended for use by middle school students worldwide. Sally Ride, the first American woman in space, and her science education company in San Diego is leading the photo-gathering effort. It's billed as "eyes on the moon for Earth's students."
This is NASA's second robotic mission to be launched since the end of the shuttle program in July. A probe named Juno is headed for Jupiter following an Aug. 5 liftoff.
NASA officials will be thrilled if Grail generates even a portion of the immense interest ignited by the Juno launch. A large crowd is expected at Cape Canaveral for Thursday's morning liftoff, which features a pair of split-second launch windows a half-hour apart.
"We're just delighted by the way the country is responding to these exciting missions," said Jim Green, director of NASA's planetary science division.
NASA: http://www.nasa.gov/mission-pa … rail/main/index.html target=-blank>http://www.nasa.gov/mission-pa … rail/main/index.html
©2011 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. | 0.856999 | 3.376364 |
Gathering detailed information on exoplanets is extremely difficult. The light from their host star overwhelms the light from the exoplanet, making it difficult for telescopes to see them.
But now a team using cutting-edge technology at the Keck Observatory has taken a big leap in exoplanet observation and has detected water in the atmosphere of a planet 179 light years away.
The solar system at the heart of this features a star called HR 8799, and its planets: HR 8799 b, c, d, and e. The system is 179 light years away in the constellation Pegasus.
The star itself is a 30 million year old main sequence star. It’s notable for a number of reasons, including its own odd stellar properties.
But it’s been noteworthy for another important reason.
In 2008, scientists announced that they had directly observed three exoplanets around the star – HR 8799b, c, and d – using the Keck and Gemini telescopes. Then in 2010 they announced the discovery of a fourth planet, HR 8799 e.
This newest announcement builds on the earlier work from 2008, and the astronomers behind this study call the latest announcement a ‘stepping stone’ on the way to better and better images of exoplanets.
The new observations are of HR 8799 c, first observed in 2008. It’s a young giant gas planet about 7 times the mass of Jupiter that orbits its star every 200 years.
These new direct imaged observations confirm the presence of water in the atmosphere, and confirm the lack of methane.
These new observations arise from a potent combination of two telescope technologies at Keck. The first is adaptive optics.
Adaptive optics counteract the blurring effects of the Earth’s atmosphere. The second is a spectrometer on the Keck 2 telescope called the Near-Infrared Cryogenic Echelle Spectrograph (NIRSPEC), a high-resolution spectrometer that works in infrared light.
“This type of technology is exactly what we want to use in the future to look for signs of life on an Earth-like planet. We aren’t there yet but we are marching ahead,” says Dimitri Mawet, an associate professor of astronomy at Caltech and a research scientist at JPL, which Caltech manages for NASA, and co-author of the study that presented these findings.
The new findings were published in the Astronomical Journal. The lead author is Ji Wang, formerly a postdoctoral scholar at Caltech and now an assistant professor at Ohio State University.
So far, astronomers have directly-imaged more than a dozen exoplanets. The HR 8799 system is the first multi-planet system to have been directly-imaged. But the images are only the first step in this study.
Once taken, the images can be analyzed for the chemical composition in their atmospheres. This is where spectroscopy comes in. In this case, the refined abilities of NIRSPEC were key.
NIRSPEC is an instrument on the Keck 2 telescope that operates in the infrared L-band. The L-band is a type of infrared light with a wavelength of around 3.5 micrometers, and a region of the spectrum with many detailed chemical fingerprints.
“The L-band has gone largely overlooked before because the sky is brighter at this wavelength,” says Mawet. “If you were an alien with eyes tuned to the L-band, you’d see an extremely bright sky. It’s hard to see exoplanets through this veil.”
By combining L-band spectography with adaptive optics, they overcame the difficulties of observing a planet who’s light is almost drowned out by its star. They were able to make the most precise measurements yet of the planet, confirming the presence of water and the absence of methane.
“Right now, with Keck, we can already learn about the physics and dynamics of these giant exotic planets, which are nothing like our own solar system planets,” says Wang.
“We are now more certain about the lack of methane in this planet.”
“This may be due to mixing in the planet’s atmosphere. The methane, which we would expect to be there on the surface, could be diluted if the process of convection is bringing up deeper layers of the planet that don’t have methane,” Wang added
Mawet’s team is already preparing for the next and newest instrument at the Keck Observatory. It’s called the KPIC, (Keck Planet Imager and Characterizer).
KPIC will use adaptive optics and spectroscopy, but to even better effect. With KPIC, astronomers will be able to image planets that are even fainter, and closer to their star than HR 8799c is.
And the future is even brighter for exoplanet imaging. The technology behind adaptive optics and spectroscopy that helped image this planet will be put into use on our future telescopes.
“KPIC is a springboard to our future Thirty Meter Telescope instrument,” says Mawet.
“For now, we are learning a great deal about the myriad ways in which planets in our universe form.” | 0.885709 | 3.920217 |
The movement of a star close to our galaxy’s supermassive black hole has proved Albert Einstein right about gravity once again. After 27 years of observation, we have finally nailed down the orbit of this star, called S2, precisely enough to spot a strange effect predicted by his general theory of relativity.
S2 circles the supermassive black hole at the centre of the Milky Way about once every 16 years. Since 1992, astronomers have been observing it with some of the most powerful telescopes on Earth to precisely trace its looping orbit.
“The precision we now have in measurements of the relative positions of the black hole and the star is comparable to watching a football game on the moon. Then you have to measure the size of the football to within of a few centimetres,” says Frank Eisenhauer at the Max Planck Institute for Extraterrestrial Physics in Germany.
He and his colleagues examined the piles of observations of S2 and found that its orbit isn’t as we would expect under Isaac Newton’s basic theory of gravity. Instead of simply following the same path on orbit after orbit, it swings around the black hole in a new direction each time, tracing out a shape that looks a bit like a daisy flower.
“Normally, if you put a star in orbit, it moves along an ellipse and the orbit closes,” says Eisenhauer. “But when the gravity is very strong, the ellipse moves from orbit to orbit and makes a rosette shape.”
This sort of movement is predicted by Einstein’s general theory of relativity, which dictates that the black hole should distort space-time around it, dragging the orbits of nearby stars as well.
It has been observed in our own solar system – Mercury’s orbit is also rosette-shaped rather than elliptical – but the effect is much more pronounced at the centre of the galaxy because the black hole is far more massive than the sun and thus stretches space-time in a more extreme way. Yet again, Einstein was right.
Journal reference: Astronomy & Astrophysics, DOI: 10.1051/0004-6361/202037813
More on these topics: | 0.841109 | 3.829202 |
Solar flares are the most powerful explosions in the Solar System, releasing enormous energy in the form of radiation, high energy particles and magnetic fields. A new spacecraft, Solar B, developed by the Japanese Space Agency (JAXA) is set to launch on September 22, 2006, and will be able to detect these flares as they’re forming. The spacecraft will measure the movement of magnetic fields across the surface of the Sun, to help scientists predict when they will build up to a flare.
Solar flares are tremendous explosions on the surface of our Sun, releasing as much energy as a billion megatons of TNT in the form of radiation, high energy particles and magnetic fields. The Suns magnetic fields are known to be an extremely important factor in producing the energy for flaring and when these magnetic fields lines clash together, dragging hot gas with them, an enormous maelstrom of energy is released. This boiling cauldron of plasma is ejected at huge speeds into the solar system and high energy particles, such as protons, can arrive at Earth within tens of minutes, to be followed a few days later by Coronal Mass Ejections, huge bubbles of gas threaded with magnetic field lines, which can cause major magnetic disturbances on Earth, sometimes with catastrophic results. Whilst scientists understand the flaring process very well they cannot predict when one of these enormous explosions will occur. The Solar-B mission, designed and built by teams in the UK, US and Japan, will investigate the so called trigger phase of these events.
Solar flares are fast and furious they can cause communication black-outs at Earth within 30 minutes of a flare erupting on the Suns surface. Its imperative that we understand what triggers these events with the ultimate aim of being able to predict them with greater accuracy said Prof. Louise Harra, the UK Solar-B project scientist based at University College Londons Mullard Space Science Laboratory [UCL/MSSL].
Solar-B will measure the movement of magnetic fields and how the Suns atmosphere responds to these movements. Since the Sun is constantly changing on small timescales Solar-B will be able to distinguish between steady movements and the changes that will build-up to a flare.
The spacecraft will be launched on the 22nd September 22:00 UT from the Japan Aerospace Exploration Agency (JAXA) Uchinoura Space Centre at Uchinoura Kagoshima in southern Japan. Solar-B will be launched into a Sun-synchronous orbit allowing uninterrupted viewing.
The Sun behaves unpredictably and will be as likely to flare during spacecraft night when Solar-B would be behind the Earth, which is why we have chosen a special type of polar orbit that will give us continuous coverage of the Sun for more than 9 months of the year, said Prof. Len Culhane from UCL/MSSL, Principal Investigator of the Extreme Ultraviolet Imaging Spectrometer [EIS] instrument on Solar-B.
Solar-B carries three instruments which have been designed to explore the critical trigger phase of solar flares. The UK (UCL/MSSL) led EIS instrument, an extremely lightweight 3-metre long telescope, will measure the dynamical behaviour of the Suns atmosphere to a higher accuracy than ever before, allowing measurement of small-scale changes occurring during the critical build-up to a flare.
In order to make the EIS as light as possible we used the same type of carbon fibre structure, from McClaren Composites, that is used to build racing cars, although being in space will subject the material to many more demands than the average racing car said Dr Ady James, EIS Instrument Project Manager at UCL/MSSL.
The EIS instrument is complemented by optical and X-ray telescopes and all three instruments will help solve the long-standing controversies on coronal heating and dynamics.
Solar-B will give us an increased understanding of the mechanisms which give rise to solar magnetic variability and how this variability modulates the total solar output and creates the driving force behind space weather, said Prof. Keith Mason, CEO of the Particle Physics and Astronomy Research Council [PPARC], the funding agency behind UK involvement in the spacecraft. Prof. Mason added, With an understanding of what triggers solar flares our opportunities for reliable prediction increase substantially”.
The Rutherford Appleton Laboratory, part of the Council for the Central Laboratory of the Research Councils [CCLRC], provided the EIS calibration and observing software.
Original Source: PPARC News Release | 0.816112 | 3.892445 |
“They have likewise discovered two lesser stars, or satellites, which revolve around Mars, whereof the innermost is distant from the centre of the primary exactly three of his diameters, and the outermost five: the former revolves in the space of ten hours, and the latter in twenty-one and a half.”
So wrote Jonathon Swift in Gulliver’s Travels when Gulliver travels on from Lilliput to floating island of Laputa, a land inhabited by mathematicians and astronomers. Swift was writing in 1726, a century and a half before the two small Martian moons were actually discovered.
Swift’s description is surprisingly accurate. The innermost moon, Phobos, orbits at a mean distance of 9,376 km (2.76 Mars radii) from the Martian centre; the outermost, Deimos, orbits at a mean distance of 23,463 km (6.92 Mars radii) from the Martian centre. The orbital period of Phobos is 7 hrs 39 mins; that of Deimos is 30 hrs 18 min.
Inevitably, there has been speculation that Swift learned about the moons from visiting Martians. In fact, there is nothing particularly mysterious about the ‘discovery’. At the time, Jupiter was known to have four moons; Earth has one, and Mars could therefore have two. Any Martian moons had to be small and close to the planet, or they would already have been observed. Swift would have used Kepler’s laws of planetary motion to calculate the orbital periods. Voltaire, writing in 1752, also mentions two Martian moons. It is presumed that he was influenced by Swift.
The actual discovery came in August 1877. Asaph Hall was an astronomer at the United States National Observatory in Washington, DC. In 1875, he was put in charge of the Observatory’s 26-inch (66 cm) refracting telescope, then the largest refractor in the world (it would be surpassed by the 28-inch refractor at the Royal Greenwich Observatory in 1893). In 1877, Mars made a close approach to Earth, and Hall’s wife, mathematician Angeline Stickney, encouraged him to look for Martian moons. Hall himself had believed that the chance of finding any moons was so small that without Angeline’s encouragement he might have given up.
On 12 August, Hall sighted Deimos, but soon lost it due to fog rising from the Potomac River. Not until the 17th were weather condition again favourable, and he recovered Deimos on the other side of Mars to where he had first seen it. On the 18th, while waiting for Deimos to come into view, he found Phobos. Further observations confirmed the existence of the two satellites, and the discovery was announced by the USNO Superintendent, Admiral John Rogers the next day.
Hall named the moons Phobos (fear) and Deimos (terror) at the suggestion of Henry Madan, Science Master of Eton. Madan was inspired by Book XV of Homer’s Iliad in which Ares summons Fear and Fright.
Phobos has an apparent magnitude of +11.80 and Deimos +12.45, within the range of a good amateur telescope of 25 cm (10 inch) or more.
Although by no means the smallest moons in the Solar System, Phobos and Deimos are tiny. Phobos measures 27 x 22 x 18 km (17 x 14 x 11 miles) mean diameter 22.2 km (13.8 miles) and its mass is 1.08×1016 kg, and Deimos is 15 x 12 x 11 km (9 x 7.5 x 7 miles) mean diameter 12.6 km (7.8 miles) and a mass of 2.0×1015 kg. The surface gravity of Phobos is 0.0057 ms-2 or 5.8 x 10-4 times that of Earth and the escape velocity is 11.39 ms-1 or 41 km/hr (25 mph); for Deimos the surface gravity is 0.0030 ms-2 or 3.0 x 10-4 times that of Earth and the escape velocity is 5.56 ms-1 or 20 km/hr (12.5 mph). A high jump athlete could just about jump into space from Deimos, though not from Phobos.
Phobos orbits just 6,000 km (3,700 miles) above the Martian surface, closer to its primary than any other Solar System body, and it is only slightly further from Mars than London is from New York. It is so close to Mars that it is not visible south of 70.4°S or north of 70.4°N. The orbital period is far shorter than the Martian day of 24 hrs 37 mins, so as seen from the surface of Mars it rises in the west, moves across the sky in 4 hours and 15 minutes, and sets in the east.
The orbit of Phobos is decaying at a rate of 1.8 cm per year, meaning that it will eventually collide with Mars or be pulled apart by tidal forces. This could happen in 30 to 50 million years from now. In 1958, the Russian astrophysicist Iosif Samuilovich Shklovsky suggested that based on the braking effect of the Martian upper atmosphere and the observed rate of orbital decay, Phobos would have to be hollow – possibly a sphere with a diameter of 16 km (10 miles) but a thickness of only 6 cm (2.5 inch). The suggestion that Phobos was an alien space station cropped up in the science fiction of the time, for example Mission to the Heart Stars, by James Blish. Shklovsky was assuming a decay rate of 5 cm per years, which was later shown to be an overestimate. In fact, purely tidal effects can account for the orbital decay; because Phobos is orbiting faster than Mars rotates, these effects are pulling it down rather than pushing it further away, as is the case for Deimos. Both moons are tidally locked, keeping the same face to Mars at all times.
Phobos is heavily cratered. The largest crater, the 9 km (5.6 mile) diameter Stickney, is named for Asaph Hall’s wife Angeline Stickney. The crater takes up a substantial portion of the surface area of Phobos, and the impact that created it must have nearly shattered the moon. Hall has had to make do with a much smaller crater. Two other features, Laputa Regio and Lagado Planitia are named after places in Gulliver’s Travels. The surface also bears many grooves and streaks, typically less than 30 meters (98 ft) deep, 100 to 200 meters (330 to 660 ft) wide, and up to 20 km (12 miles) in length. The grooves were once thought to have been caused by the impact that formed Stickney, but they appear to be of different ages. One possibility is that they are ‘stretch marks’ caused by the tidal deformation of Phobos, but these are too weak to deform a solid body. The suggestion, therefore, is that Phobos is a ‘rubble pile’ surrounded by a layer of powdery regolith (loose material) about 100 m (330 ft) deep. If so, it will break up when it falls to within a distance of 2.1 Mars radii (6,800 km; 4,225 miles) of the centre at which point its feeble gravity will be overwhelmed by that of Mars. At all events, the density of Phobos is too low for it to be composed of solid rock.
Deimos is less heavily cratered than Phobos. Only two features have been given names: the craters Swift and Voltaire.
Phobos and Deimos both appear to be composed of C-type rock, similar to blackish carbonaceous chondrite asteroids. The traditional view is that they are captured asteroids, but the low eccentricity and inclination of their orbits argues against this. One possibility is that they were formed from ejecta produced a large asteroid collided with Mars.
Very little was known about the physical condition of either satellite prior to the space age. The first photographs were taken by the Mariner 7 fly-by probe in August 1969; two years later the first closeups were obtained by the Mariner 9 orbiter. The satellites have been extensively photographed since. Both have also been photographed by rovers on the Martian surface. Due to its low orbital inclination, Phobos regularly causes annular eclipses of the Sun, but as its apparent diameter from the Martian surface is only a third that of the moon, it is too small to cause a total eclipse. The eclipses last around thirty seconds.
No successful landings have yet been made on either, although the Russians have made two attempts to land probes on Phobos. Phobos 1 and Phobos 2 were launched in 1988. Phobos 1 was lost en route to Mars after a technician accidentally shut down the probe’s attitude thrusters. Phobos 2 reached Mars orbit successfully, and it returned images of both Mars and Phobos. It was then supposed to approach to within 50 m of Phobos and deploy a pair of landers, but during this phase a computer malfunction caused the probe to lose contact with Earth.
In November 2011, the Russians tried again. Fobos-Grunt (‘Phobos Ground’) was supposed to be a sample-return mission, but the spacecraft failed to leave orbit and eventually fell back to Earth. Since the failure of this mission, there have been a number of proposals for a sample return mission to Phobos, but none are likely to launch in the next few years.
Many proposals for human exploration of Mars call for landings on Phobos and Deimos as a first stage. Human missions to the Martian moons would result in the development and operation of new technologies, many of which would be required for an eventual landing on Mars, but without the attendant complexities and risks. | 0.8934 | 3.71755 |
The US space probe Dawn began orbiting the dwarf planet Ceres Friday on a voyage of discovery into the solar system’s main asteroid belt, NASA said Friday.
The probe — the first to orbit a dwarf planet — will stay over the mysterious body for 16 months to study its structure and gather clues to help mankind better understand how the planets were created.
The space probe was captured by the dwarf planet’s gravity at 1239 GMT, some 38,000 miles (61,000 kilometers) from Ceres’s surface.
About an hour later, it sent a signal to mission controllers at NASA’s Jet Propulsion Laboratory in Pasadena, California to say it was “healthy and thrusting with its ion engine,” the space agency said in a statement.
When it was discovered in 1801, Ceres was classified as a planet, only to be reclassified later as an asteroid and then a dwarf planet.
“Now, after a journey of 3.1 billion miles (4.9 billion kilometers) and 7.5 years, Dawn calls Ceres home,” said Dawn chief engineer Marc Rayman, who is also mission director at JPL.
The dwarf planet, which has an average diameter of 590 miles, was first spotted by Sicilian astronomer Father Giuseppe Piazzi.
It makes a full rotation every nine hours, and NASA is hoping for a wealth of data to begin pouring in as the spacecraft orbits Ceres.
“We feel exhilarated,” said Dawn principal investigator Chris Russell from the University of California, Los Angeles.
“We have much to do over the next year and a half, but we are now on station with ample reserves, and a robust plan to obtain our science objectives.”
– Two bright spots –
Around April or May, the probe will start to move in closer to make a first full assessment of the planet, and by November will be as near as 230 miles from Ceres’s surface.
Scientists will be looking for signs of geologic activity via changes in two bright spots on the planet, or other features on Ceres’ surface over time.
The mission will also help to better understand the origins of the solar system and the possibility of life (in the form of micro-organisms) on Ceres.
“Studying Ceres allows us to do historical research in space, opening a window into the earliest chapter in the history of our solar system,” said Jim Green, director of NASA?s Planetary Science Division.
“Data returned from Dawn could contribute significant breakthroughs in our understanding of how the solar system formed.”
The last images of Ceres were taken in March, and show a slim silver crescent, with most of the dwarf planet shrouded in darkness. But NASA scientists hope to capture sharper images during the mission once Dawn emerges from the planet’s dark side.
Though this is the first mission to orbit a dwarf planet, Dawn explored the giant Vesta asteroid in 2011 and 2012. It gathered information and thousands of images before it set off for the years-long journey to Ceres.
Ceres and Vesta are the two largest bodies in the asteroid belt between Mars and Jupiter.
Launched in 2007, the $473 million Dawn mission is equipped with a high definition camera and two spectrometers. It is outfitted with an ion propulsion engine that allows it to reach high speeds and also make a slow approach to drop into orbit.
The US space agency has also set its sights on Pluto, and in 2006 launched the New Horizons spacecraft to study the dwarf planet.
Next year, the US space agency plans to launch its Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer (OSIRIS-REx) spacecraft, to “study a large asteroid in unprecedented detail and return samples to Earth,” NASA has said.
Ocasio-Cortez blasts her NYC mayor for ‘making excuses’ for NYPD violence against protesters
The youngest woman ever elected to Congress ripped her city's mayor on Saturday for "making excuses" for New York Police Department actions.
In videos that circulated widely on social media, NYPD cruisers can be seen driving into pedestrian protesters.
Rep. Alexandria Ocasio-Cortez (D-NY) blasted New York City Mayor de Blasio for defending the NYPD.
On Twitter, she told the mayor, "your comments tonight were unacceptable."
‘Light ’em up’: Police open fire on people filming them from their front porch
Video reportedly taken from the Wittier neighborhood of Minneapolis on Saturday shows authorities shooting projectiles upon people filming them from a front porch.
On Friday, Minneapolis Mayor Jacob Frey imposed a curfew on the city, but his emergency order did not apply to citizens' homes or front porches.
Yet a video posted on Twitter shows a Minnesota National Guard humvee rolling down residential streets, followed by a group of police.
"Look at this, they just keep coming," a woman is heard saying as the camera shows the police.
"Go inside. Get inside," the police shouted.
‘They just fired on us’: Horrifying videos of cops ‘using journalists for target practice’ in Minneapolis
Journalists covering the protests in Minneapolis reported on being targeted by police on Saturday.
Multiple reports -- including live coverage on CNN -- showed police firing rubber bullets at journalists.
It’s open season on the media for the cops in Minneapolis. Evil. https://t.co/ZR3Nnf9ofH
— Nick Stellini (@StelliniTweets) May 31, 2020 | 0.880041 | 3.332884 |
Thanks to the success of the Kepler mission, we know that there are multitudes of exoplanets of a type called “Hot Jupiters.” These are gas giants that orbit so close to their stars that they reach extremely high temperatures. They also have exotic atmospheres, and those atmospheres contain a lot of strangeness, like clouds made of aluminum oxide, and titanium rain.
A team of astronomers has created a cloud atlas for Hot Jupiters, detailing which type of clouds and atmospheres we’ll see when we observe different Hot Jupiters.
Continue reading “Extremely Hot Exoplanets Can Have Extreme Weather, Like Clouds of Aluminum Oxide and Titanium Rain”
In the past few decades, the number of planets discovered beyond our Solar System has grown exponentially. To date, a total of 4,158 exoplanets have been confirmed in 3,081 systems, with an additional 5,144 candidates awaiting confirmation. Thanks to the abundance of discoveries, astronomers have been transitioning in recent years from the process of discovery to the process of characterization.
In particular, astronomers are developing tools to assess which of these planets could harbor life. Recently, a team of astronomers from the Carl Sagan Institute (CSI) at Cornell University designed an environmental “decoder” based on the color of exoplanet surfaces and their hosts stars. In the future, this tool could be used by astronomers to determine which exoplanets are potentially-habitable and worthy of follow-up studies.
Continue reading “What Are Some Clues to the Climates of Exoplanets?”
In 2017, astronomers used ALMA (Atacama Large Millimeter/sub-millimeter Array) to look at the star AB Aurigae. It’s a type of young star called a Herbig Ae star, and it’s less then 10 million years old. At that time, they found a dusty protoplanetary disk there, with tell-tale gaps indicating spiral arms.
Now they’ve taken another look, and found a very young planet forming there.
Continue reading “This is an Actual Image of a Planet-Forming Disc in a Distant Star System”
We’ve found thousands and thousands of exoplanets now. And spacecraft like TESS will likely find thousands and thousands more of them. But most exoplanets are gassy giants, molten hell-holes, or frozen wastes. How can we find those needles-in-the-haystack habitable worlds that may be out there? How can we narrow our search?
Well, first of all, we need to find water. Oceans, preferably, since that’s where life began on Earth. And according to a new study, those oceans need to circulate in particular ways to support life.
Continue reading “Ocean Circulation Might Be the Key to Finding Habitable Exoplanets”
Planet formation is a notoriously difficult thing to observe. Nascent planets are ensconced inside dusty wombs that resist our best observation efforts. But recently, astronomers have made progress in imaging these planetary newborns.
A new study presents the first-ever direct images of twin baby planets forming around their star.
Continue reading “Astronomers Are Sure These Are Two Newborn Planets Orbiting a Distant Star”
Jupiter is the Boss.
Well, in terms of planets in our Solar System it is. It’s played a huge role in shaping the Solar System due to its mass and its gravity. Here’s a few ways it’s shaped our system:
Continue reading “Astronomers Find a Planet With Three Times the Mass of Jupiter”
We’re waiting patiently for telescopes like the James Webb Space Telescope to see first light, and one of the reasons is its ability to study the atmospheres of exoplanets. The idea is to look for biosignatures: things like oxygen and methane. But a new study says that exoplanets with hydrogen in their atmospheres are a good place to seek out alien life.
Continue reading “Worlds With Hydrogen in Their Atmospheres Could Be the Perfect Place to Search for Life”
Some very powerful telescopes will see first light in the near future. One of them is the long-awaited James Webb Space Telescope (JWST.) One of JWST’s roles—and the role of the other upcoming ‘scopes as well—is to look for biosignatures in the atmospheres of exoplanets. Now a new study is showing that finding those biosignatures on exoplanets that orbit white dwarf stars might give us our best chance to find them.
Continue reading “Rocky Planets Orbiting White Dwarf Stars Could be the Perfect Places to Search for Life”
To date, astronomers have confirmed the existence of 4,152 extrasolar planets in 3,077 star systems. While the majority of these discoveries involved a single planet, several hundred star systems were found to be multi-planetary. Systems that contain six planets or more, however, appear to be rarer, with only a dozen or so cases discovered so far.
This is what astronomers found after observing HD 158259, a Sun-like star located about 88 light-years from Earth, for the past seven years using the SOPHIE spectrograph. Combined with new data from the Transiting Exoplanet Space Satellite (TESS), an international team reported the discovery of a six planet system where all were in near-perfect rhythm with each other.
Continue reading “Astronomers Find a Six-Planet System Which Orbit in Lockstep With Each Other”
In 2017, an international team of astronomers announced a momentous discovery. Based on years of observations, they found that the TRAPPIST-1 system (an M-type red dwarf located 40 light-years from Earth) contained no less than seven rocky planets! Equally exciting was the fact that three of these planets were found within the star’s Habitable Zone (HZ), and that the system itself has had 8 billion years to develop the chemistry for life.
At the same time, the fact that these planets orbit tightly around a red dwarf star has given rise to doubts that these three planets could maintain an atmosphere or liquid water for very long. According to new research by an international team of astronomers, it all comes down to the composition of the debris disk that the planets formed from and whether or not comets were around to distribute water afterward. | 0.909741 | 3.777486 |
celestia − A real-time visual space simulation
This manual page documents briefly celestia, a 3D space simulator. Celestia is a real-time visual simulation of space in our local region of the universe. Choose a point within about 1000 light years of Earth, and Celestia will show you an approximation of how it would appear to your eyes were you actually there. Some of what Celestia shows is necessarily hypothetical--the farther away from Earth you get, the less real data there is and the more guesswork is involved. Thus Celestia supplements observational data with good guesses based on models of stellar and planetary processes.
Celestia is unique in its ability to allow you to navigate at an immense range of scales. Orbit a couple kilometers above the surface of a tiny, irregular asteroid, then head off toward Jupiter, watching it grow from a bright point of light into a looming sphere filling your field of vision. Leave our solar system entirely and observe the sun as it fades from a brilliant disk to a bright star, disappearing almost entirely as you head off toward the Upsilon Andromeda system to orbit around its innermost giant planet.
Celestia will start up in a window, display a welcome message and some information about your target (top left corner), your speed, and the current time (Universal Time, so it’ll probably be a few hours off from your computer’s clock.) In Celestia, you’ll generally have an object selected; currently, it’s Eros, but it could also be a star, planet, spacecraft, or galaxy. The simplest way to select an object is to click on it. Try clicking on a star to select it. Right drag the mouse to orbit arround the selected target. Left dragging the mouse changes your orientation too, but the camera rotates about its center instead of rotating around the target. Rolling the mouse wheel will change your distance to the space station--you can move light years away, then roll the wheel in the opposite direction to get back to your starting location. If your mouse lacks a wheel, you can use the Home and End keys instead.
Press G and you’ll zoom through space toward the selected star. If you press G again, you’ll approach the star even closer. Press H to select our Sun, and then G to go back to our solar system. You’ll find yourself half a light year away from the Sun, which looks merely like a bright star at this range. Press G three more times to get within about 30 AU of the Sun and you will be to see a few planets become visible near the Sun.
It’s possible to choose a star or planet by name: press Enter and type in the name, and pressing Enter again. You can use common names, or Bayer designations and HD catalog numbers for stars. Bayer and Flamsteed designations need to be entered like "Upsilon And" and "51 Peg". The constellation must be given as a three letter abbreviation and the full Greek letter name spelled out. HD catalog numbers must be entered with a space between HD and the number.
The glut based version accepts the usual X Window System specific options, namely:
Specify the X server to connect to. If not specified, the value of the DISPLAY environment variable is used.
Determines where window’s should be created on the screen. The parameter following -geometry should be formatted as a standard X geometry specification. The effect of using this option is to change the GLUT initial size and initial position the same as if glutInitWindowSize or glutInitWindowPosition were called directly.
Requests all top-level windows be created in an iconic state.
Force the use of indirect OpenGL rendering contexts.
Force the use of direct OpenGL rendering contexts (not all GLX implementations support direct rendering contexts). A fatal error is generated if direct rendering is not supported by the OpenGL implementation.
If neither -indirect or -direct are used to force a particular behavior, GLUT will attempt to use direct rendering if possible and otherwise fallback to indirect rendering.
After processing callbacks and/or events, check if there are any OpenGL errors by calling glGetError. If an error is reported, print out a warning by looking up the error code with gluErrorString. Using this option is helpful in detecting OpenGL run-time errors.
Enable synchronous X protocol transactions. This option makes it easier to track down potential X protocol errors.
Celestia has been written by Chris Laurel <claurel AT www DOT shatters DOT net> and it’s available under the terms and conditions of the GNU General Public LIcense from http://celestia.sf.net/ | 0.914048 | 3.380171 |
Twinkle Technical Blog
This is the first in a series of blog posts that will discuss key technical considerations on the Twinkle spacecraft design. These posts will provide an insight into technical aspects of the mission and will cover a range of engineering topics. Here we introduce our orbit selection, the impact of Earth’s obstruction and how many exoplanet science targets are accessible within the field of regard.
Twinkle is a space-based spectroscopic observatory that will operate simultaneously across the visible and infrared wavelengths, enabling the characterisation of exoplanet atmospheres, solar system objects and stellar targets. We take a new approach on delivering Twinkle: we focus on maximising technology heritage and cost-effectiveness, without the added public body remit of driving forward engineering and technological innovation. For additional information on our approach see the “Mission” page.
Selecting the right orbit for Twinkle
In selecting an orbit for Twinkle there were several primary concerns that needed to be considered: the thermal stability of the orbit, the cost of launch and the impact of the orbit on observations due to Earth obstruction. Feeding into the cost concern is the impact of the radiation environment on the spacecraft systems and the overall mass and size of the spacecraft when determining launch costs.
A number of potential orbits have been considered for Twinkle, each of which has been reviewed to understand its benefits and drawbacks. One option was to send the spacecraft to the second Lagrange point (L2), which has been used for a number of missions (e.g. Herschel, Planck) and will be used in the near future for Euclid, JWST and ARIEL. From a thermal perspective, L2 would be an ideal orbit, with negligible Earth flux, stable solar conditions and little to no variability with seasons or years. L2 is, however, a costly orbit to reach with a harsh radiation environment that would require radiation-hardened electronics. More bespoke orbits, such as the one used by TESS, or one which is Earth trailing/leading (e.g. Spitzer, Kepler), were also considered but suffer from the same issues as the L2 option.
Figure 1: Examples of Low Earth orbits used by Twinkle, CHEOPS and Hubble, showing their orientation with respect to Earth’s axis of rotation (Credit: ESA).
Low Earth Orbits (LEOs), typically defined as those with an altitude of less than 2,000km, [have a more benign radiation environment], are more affordable to reach than MEO or GEO altitudes and have also been used for many astrophysics missions. The Hubble Space Telescope operates in an equatorial LEO while CHEOPS operates in a dawn-dusk sun-synchronous LEO. Some other recent scientific satellites to have operated in a LEO include CoRoT, AKARI and WISE/NEOWISE.
Sun-Synchronous orbit description and selection
After considering the various options, a dawn dusk sun-synchronous LEO similar to the CHEOPS spacecraft was selected. Twinkle orbits the Earth along the terminator, pointing away from the Sun along the Sun-Earth vector (see Fig 1). This orbit tightly constrains the Sun-Spacecraft-Earth geometry, providing the highly stable thermal environment that is essential for maintaining the cryogenic temperatures necessary for infrared spectroscopy. Viewed from the Earth, sun-synchronous orbits are those where the spacecraft always passes overhead at the same time of day, meaning that the orbit of the spacecraft needs to shift each day as the Earth rotates around the sun. Given that there are 365 days a year, the satellite has to shift its orbit by approximately one degree per day to maintain the same angle of the orbital plane to the sun. For a well-chosen altitude and inclination this shift is natural; it is caused by the fact that the Earth is an oblate spheroid, wider at the Equator, causing additional gravitational forces to act on the satellite.
LEOs also offer the least onerous radiation environment besides L2, which further helps to reduce the complexity of the spacecraft design and, as a result, the overall mission cost.
With LEO selected the primary parameter left to consider is altitude, with the final determination to be made once construction starts. After reviewing several small launch vehicles and determining a preliminary mass budget with the industrial suppliers, an orbit altitude of 700 km was baselined and this blog post considers that altitude in the analysis shown.
Shielding constraints on Field of Regard
The Twinkle spacecraft makes use of a sun-shield to reject incident flux from the sun. The design also makes use of thermal blankets on the telescope and ensures that the shields are also shaped to minimise Earth flux. Considering the mechanical design of the spacecraft and the constraints of fairing size on launch, we have defined the field of regard of Twinkle to be ± 40◦ from the anti-sun vector.
Each day the plane of the orbit of the spacecraft, relative to the stars, processes by just under 1°. This means that the stars visible to the field of regard change each day. This is compounded when we consider seasonal variations. The geometry of the orbit with respect to the sun changes throughout the year as the sun rises and falls along the ecliptic plane. This change in Earth Obstruction can be seen visually in Figure 2; during the spring periods the orbit is more closely aligned with the perpendicular plane of the sun vector, while during winter the two planes are more separated causing more cases of Earth obstruction.
Figure 2: Spring (left) with orbit in blue and Winter (right) with orbit in black graphics showing Earth obstruction (Credit: Airbus, Stevenage).
For a telescope orbiting at 700 km, the Earth occupies a significant portion of the sky and must be considered when reviewing what is observable day to day. The further a target is from the ecliptic plane, the larger the angle from the anti-sun vector, and the closer to an Earth limb the target becomes. Beyond ~25° inclination from the ecliptic, the observation will begin to be directly obstructed by the Earth for parts of each orbit and periodic slewing by the spacecraft will be required to avoid observing the Earth.
This means that in order to determine when targets can be best viewed by Twinkle one must consider the time of year during scheduling. The further a target is from the ecliptic plane, the more restricted its availability for unobstructed observations. For targets closer to the ecliptic the overlap of daily fields of regard is larger and there will be more days per year when the target is observable with Twinkle – this can be seen in Figure 3.
Figure 3: Total time spent in Twinkle’s Field of Regard with locations of known exoplanets and predicted TESS detections overlaid (Credits: Twinkle/Blue Skies Space).
The seasonal variations also cause brief eclipse periods in Twinkle’s orbit, although the duration of these eclipses should not impact the ability of the spacecraft to continue mission operations with the design accounting for this with sufficient battery capacity and a low power payload system. The peak duration of the eclipse is less than 20 minutes per ~100 minute orbit and the eclipse season is approximately four months in length.
Science opportunities for Twinkle observations
One important consideration is how long a given exoplanet may be continuously observed with Twinkle, as this determines the viability of various science cases for each target. Several hundred potentially observable exoplanets lie within Twinkle’s field of regard. Depending on their position in the sky there will be a maximum duration for which they are visible without obstruction by the Earth. Long, uninterrupted periods allow not only for the observation of a complete transit or eclipse but potentially also permit the planet to be studied for the entirety of its orbit, providing an unbroken phase curve.
When considering known exoplanets in Twinkle’s field of regard we find that a majority (>70%) of targets are available for continuous observations of longer than 24 hours – a breakdown is given in Figure 4. The large number of planets with long continuous observation periods is due to many discovered planets being located close to the ecliptic plane, largely thanks to the K2 mission.
The coverage of the sky closely repeats each year and for a given target there will be a well-defined revisit time where it will be possible to review scientific data and evaluate the continued observation of target. For a target on the ecliptic the revisit time will be approximately 285 day.
Figure 4: Maximum continuous observation time for known planets within Twinkle’s Field of Regard to a granularity of one day. This chart does not account for stray light limitations, which will be quantified for the day and night Earth limb during Twinkle’s detailed design phase (Credit: Twinkle/Blue Skies Space).
Twinkle is optimised for bright exoplanet targets on short orbits, but it can also observe more challenging targets. All current known targets are captured in Twinkle’s exoplanet catalogue and new targets will be added as they are discovered by other missions and surveys.
About the author
Lead Systems Engineer
Ian leads the technical development of the Twinkle mission working on spacecraft and ground systems. As a System Engineer, Ian works closely with our industrial partners in developing the design. Ian previously worked for Surrey Satellites as a Lead Systems Engineer across multiple LEO missions and constellations. | 0.874538 | 3.157388 |
eso1833 — Science Release
Largest Galaxy Proto-Supercluster Found
Astronomers using ESO’s Very Large Telescope uncover a cosmic titan lurking in the early Universe
17 October 2018
An international team of astronomers using the VIMOS instrument of ESO’s Very Large Telescope have uncovered a titanic structure in the early Universe. This galaxy proto-supercluster — which they nickname Hyperion — was unveiled by new measurements and a complex examination of archive data. This is the largest and most massive structure yet found at such a remote time and distance — merely 2 billion years after the Big Bang.
A team of astronomers, led by Olga Cucciati of Istituto Nazionale di Astrofisica (INAF) Bologna, have used the VIMOS instrument on ESO’s Very Large Telescope (VLT) to identify a gigantic proto-supercluster of galaxies forming in the early Universe, just 2.3 billion years after the Big Bang. This structure, which the researchers nicknamed Hyperion, is the largest and most massive structure to be found so early in the formation of the Universe . The enormous mass of the proto-supercluster is calculated to be more than one million billion times that of the Sun. This titanic mass is similar to that of the largest structures observed in the Universe today, but finding such a massive object in the early Universe surprised astronomers.
“This is the first time that such a large structure has been identified at such a high redshift, just over 2 billion years after the Big Bang,” explained the first author of the discovery paper, Olga Cucciati . “Normally these kinds of structures are known at lower redshifts, which means when the Universe has had much more time to evolve and construct such huge things. It was a surprise to see something this evolved when the Universe was relatively young!”
Located in the COSMOS field in the constellation of Sextans (The Sextant), Hyperion was identified by analysing the vast amount of data obtained from the VIMOS Ultra-deep Survey led by Olivier Le Fèvre (Aix-Marseille Université, CNRS, CNES). The VIMOS Ultra-Deep Survey provides an unprecedented 3D map of the distribution of over 10 000 galaxies in the distant Universe.
The team found that Hyperion has a very complex structure, containing at least 7 high-density regions connected by filaments of galaxies, and its size is comparable to nearby superclusters, though it has a very different structure.
“Superclusters closer to Earth tend to a much more concentrated distribution of mass with clear structural features,” explains Brian Lemaux, an astronomer from University of California, Davis and LAM, and a co-leader of the team behind this result. “But in Hyperion, the mass is distributed much more uniformly in a series of connected blobs, populated by loose associations of galaxies.”
This contrast is most likely due to the fact that nearby superclusters have had billions of years for gravity to gather matter together into denser regions — a process that has been acting for far less time in the much younger Hyperion.
Given its size so early in the history of the Universe, Hyperion is expected to evolve into something similar to the immense structures in the local Universe such as the superclusters making up the Sloan Great Wall or the Virgo Supercluster that contains our own galaxy, the Milky Way. “Understanding Hyperion and how it compares to similar recent structures can give insights into how the Universe developed in the past and will evolve into the future, and allows us the opportunity to challenge some models of supercluster formation,” concluded Cucciati. “Unearthing this cosmic titan helps uncover the history of these large-scale structures.”
The moniker Hyperion was chosen after a Titan from Greek mythology, due to the immense size and mass of the proto-supercluster. The inspiration for this mythological nomenclature comes from a previously discovered proto-cluster found within Hyperion and named Colossus. The individual areas of high density in Hyperion have been assigned mythological names, such as Theia, Eos, Selene and Helios, the latter being depicted in the ancient statue of the Colossus of Rhodes.
The titanic mass of Hyperion, one million billion times that of the Sun, is 1015 solar masses in scientific notation.
Light reaching Earth from extremely distant galaxies took a long time to travel, giving us a window into the past when the Universe was much younger. This wavelength of this light has been stretched by the expansion of the Universe over its journey, an effect known as cosmological redshift. More distant, older objects have a correspondingly larger redshift, leading astronomers to often use redshift and age interchangeably. Hyperion’s redshift of 2.45 means that astronomers observed the proto-supercluster as it was 2.3 billion years after the Big Bang.
This research is published in the paper “The progeny of a Cosmic Titan: a massive multi-component proto-supercluster in formation at z=2.45 in VUDS”, which will appear in the journal Astronomy & Astrophysics.
The team behind this result was composed of O. Cucciati (INAF-OAS Bologna, Italy), B. C. Lemaux (University of California, Davis, USA and LAM - Aix Marseille Université, CNRS, CNES, France), G. Zamorani (INAF-OAS Bologna, Italy), O.Le Fèvre (LAM - Aix Marseille Université, CNRS, CNES, France), L. A. M. Tasca (LAM - Aix Marseille Université, CNRS, CNES, France), N. P. Hathi (Space Telescope Science Institute, Baltimore, USA), K-G. Lee (Kavli IPMU (WPI), The University of Tokyo, Japan, & Lawrence Berkeley National Laboratory, USA), S. Bardelli (INAF-OAS Bologna, Italy), P. Cassata (University of Padova, Italy), B. Garilli (INAF–IASF Milano, Italy), V. Le Brun (LAM - Aix Marseille Université, CNRS, CNES, France), D. Maccagni (INAF–IASF Milano, Italy), L. Pentericci (INAF–Osservatorio Astronomico di Roma, Italy), R. Thomas (European Southern Observatory, Vitacura, Chile), E. Vanzella (INAF-OAS Bologna, Italy), E. Zucca (INAF-OAS Bologna, Italy), L. M. Lubin (University of California, Davis, USA), R. Amorin (Kavli Institute for Cosmology & Cavendish Laboratory, University of Cambridge, UK), L. P. Cassarà (INAF–IASF Milano, Italy), A. Cimatti (University of Bologna & INAF-OAS Bologna, Italy), M. Talia (University of Bologna, Italy), D. Vergani (INAF-OAS Bologna, Italy), A. Koekemoer (Space Telescope Science Institute, Baltimore, USA), J. Pforr (ESA ESTEC, the Netherlands), and M. Salvato (Max-Planck-Institut für Extraterrestrische Physik, Garching bei München, Germany)
ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 16 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and with Australia as a Strategic Partner. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.
INAF Fellow – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna
ESO Public Information Officer
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Tel: +49 89 3200 6670 | 0.881274 | 3.864043 |
Research Highlight | March 29, 2019
Hayabusa, a robotic spacecraft developed by the Japan Aerospace Exploration Agency (JAXA), returned to Earth in June 2010 after taking a sample from a small near-Earth asteroid named 25143 Itokawa. Professor Hisayoshi Yurimoto at the Faculty of Science, a member of the project is now analyzing the sample to find clues for elucidating how the solar system was born 4.6 billion years ago. He is also preparing to analyze a sample from Hayabusa2, which is scheduled to return to Earth in 2020 after collecting a sample from another asteroid, Ryugu, in February 2019.
Yurimoto is a born scientist. He has had a keen interest in science, especially beautiful minerals, ever since he was young. “I was so elated when I found quartz in a nearby mikan tangerine field,” Yurimoto said with a grin. Yurimoto researched minerals and obtained a doctor’s degree in the study of peridots, a green transparent variety of olivine often used as semi-precious gems. Olivine is found in lava and meteorites.
A turning point came more than two decades ago when Yurimoto was around 30 years old. During a meeting with a meteorite specialist, Yurimoto learned that meteorites contain minerals that are not found on Earth. More specifically, some minerals have isotopic ratios different from that of substances on Earth. Isotopes — two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, thus differing in their mass — exist in a certain ratio in elements on our planet.
“I was astounded to discover a meteorite’s isotopic ratio was different from the projected figure even though minerals in the meteorite were formed based on the same established laws of physics and chemistry,” Yurimoto said, explaining why he started focusing his research on meteorites to unravel the origin and evolution of the solar system. In those days, however, meteorites were hard to come by in Japan. Yurimoto proceeded with his research by borrowing samples from the aforementioned specialist. He also started developing an isotope microscope, a one-of-a-kind device weighing 10 tons, to unlock the mysteries enveloping the isotopic ratio in meteorites. The huge microscope, which was completed after 20 years of research and development, enabled researchers to distinguish isotopes of the same element in meteorites.
Yurimoto’s group used this isotope microscope to analyze the sample from Itokawa. His group examined the isotopic ratio of oxygen, the most abundant element in meteorites, which has three kinds of isotopes. The results showed the isotopic ratio in the sample was the same as that of ordinary chondrites, which account for 80 percent of meteorites that fall to Earth, demonstrating that meteorites are asteroid fragments and contain vital information from the time when the solar system was born. This finding was reported by the media and fueled discussions around the globe.
It is possible to deduce the pressure, temperature and time required to form meteorites by examining meteorites with the isotope microscope. “We are trying to figure out how the mysterious conditions in meteorites were created, based on isotopic microscopic analyses,” Yurimoto said, referring to the different isotopic ratios. “There are various theories about this. Some researchers suggest it is a result of lightening in space, and others point to the effects of collisions between celestial bodies. Nobody knows for certain. It is difficult to think about a phenomenon nobody has seen, but I’d definitely like to unlock that mystery.”
Use of the microscope is not limited to space science. As it is suitable for examining molecular movements, the microscope is used for research in fields including medicine, biology, agricultural science and engineering. “It is interesting to talk to many researchers in different fields who would like to use the microscope,” Yurimoto said. “Doing so sometimes has led to joint research with my team.”
Yurimoto’s curiosity about the unknown has not dimmed since he was looking for pieces of quartz as a boy. He is determined to decipher information hidden in meteorites and the original materials that created them, which Hayabusa collected from Itokawa. Driven by his unlimited curiosity that culminated in the development of a groundbreaking device, Yurimoto’s ultimate goal is to take a glimpse into a world nobody has seen before. | 0.878853 | 3.593182 |
Scientists taking a new look at old data from NASA’s Mars Odyssey spacecraft, which has been orbiting Mars since 2001, have found large deposits of what may be permafrost-like ice near the Martian equator.
The discovery is unexpected, because the region was assumed to be dry, and may one day provide sustenance and food for astronauts.
The water lies in a region of Mars called the Medusae Fossae, which consists of deep layers of easily erodible sediments along the boundary between the planet’s northern lowlands and southern highlands.
It was found by the spacecraft’s neutron spectrometer, which analyses neutron radiation emitted from the Martian surface as it is bombarded by high-energy cosmic rays raining down from outer space.
“These interact with the top metre of the soil and kick out particles, neutrons included,” says Jack Wilson, a planetary astronomer at Johns Hopkins University’s Applied Physics Laboratory in Laurel, Maryland, and lead author of the paper describing the find.
By studying the energy distribution of these neutrons, scientists can determine the elements contained in the top layer of the planet’s surface, particularly hydrogen, a marker for water.
Early on, the Mars Odyssey data showed abundant water in soils near the Martian poles — a finding confirmed in 2008 when NASA’s Phoenix lander dug up chunks of pure ice only centimetres below the surface. But these same early analyses showed very little water at the planet’s equator.
Those early studies, however, had extremely low resolution – in the order of just 520 kilometres. By applying a mathematical technique called Bayesian image reconstruction, Wilson’s team was able to redo the analysis with a resolution of 290 kilometres.
“[It’s] similar to lowering the altitude of the spacecraft by 50%,” he says. “You’re getting a better view of what’s going on.”
They found that while most of the equatorial regions remained low in water, two parts of Medusae Fossae, each several hundred kilometres across, popped out with high concentrations — up to 40% by weight.
It was a startling find, because the Martian equator is warm enough that any ice that close to the surface should long since have vaporised.
Nevertheless, it was there, somehow preserved from a time hundreds of thousands or millions of years ago when variations in the planet’s tilt would have produced climates in which it could have accumulated. Perhaps, Wilson says, there’s a cap-like layer of crusty soil that has helped preserve it. Or perhaps the water is included in heavily hydrated minerals that have somehow been protected from breaking down and releasing their water over the course of geologic time.
Either way, it’s an important find for future manned exploration of Mars, because that much water — whether in the form of ice or heavily hydrated minerals — can be converted not only into drinking water but into rocket fuel, which Wilson notes, “is in large part hydrogen and oxygen.” That means fuel for the return to Earth could be manufactured on Mars — hugely better than having to transport it there from Earth.
Other scientists agree. Rebecca Williams, a Wisconsin-based researcher with the Planetary Science Institute, calls the study “interesting,” adding, “the search is on for equatorial water to support future human exploration. One interesting implication [of this study] is that sites near the Medusae Fossae Formation are more appealing.”
Richard A Lovett
Richard A. Lovett is a Portland, Oregon-based science writer and science fiction author. He is a frequent contributor to COSMOS.
Read science facts, not fiction...
There’s never been a more important time to explain the facts, cherish evidence-based knowledge and to showcase the latest scientific, technological and engineering breakthroughs. Cosmos is published by The Royal Institution of Australia, a charity dedicated to connecting people with the world of science. Financial contributions, however big or small, help us provide access to trusted science information at a time when the world needs it most. Please support us by making a donation or purchasing a subscription today. | 0.887875 | 4.076562 |
Learning about planets through inference is a necessary procedure, given the state of our technology. We do have a few direct images of exoplanets now, but when relying on radial velocity data or transits, we’re looking at the effects planets cause upon our measurements of their stars. With CoRoT and Kepler now yielding high-quality transit data, it’s encouraging to see how we can go to work on this information to learn even more about the systems they study. Thus the announcement of WASP-3c, a second planet found around a star in the constellation Lyra, whose existence was pegged by its effect on the previously known planet.
WASP-3b was discovered by the Wide Angle Search for Planets project (SuperWASP), a British extrasolar planet detection program that uses robotic observatories that monitor stars for transit events. Eight wide-angle cameras monitor millions of stars, with 26 exoplanets now discovered. The new work, led by Gracjan Maciejewski (Jena University, Germany) went to work on WASP-3b using a method called Transit Timing Variation (TTV), which studies whether any variation in time between planetary transits of a known world can be detected.
The timing of known transiting exoplanets may prove to be an important tool, one that has already been studied on several transiting planet systems. If this work proves out, it will be the first planetary detection using the method. From the paper:
In a single-planet extrasolar system a planet orbits its host star on a Keplerian orbit. If one assumes that the inclination of its orbit plane is close to 90◦, transits occur at equal intervals. If there is another (not necessarily transiting) planet in the system it interacts gravitationally with the transiting planet and generates deviations from the strictly Keplerian case. These perturbations result in a quasi-periodic signal in an O−C diagram [analysis of observations minus calculations] of the transiting planet.
In this case, WASP-3b, a planet of 1.76 Jupiter masses in a 1.85 day orbit around a F7-class star, is shown to be perturbed by another body. Gracjan Maciejewski comments on the find:
“We detected periodic variations in the transit timing of WASP-3b. These variations can be explained by an additional planet in the system, with a mass of 15 Earth-mass (i.e., one Uranus mass) and a period of 3.75 days. In line with international rules, we called this new planet WASP-3c.”
Image: This is the so-called O-C diagram. We plot the difference between observed (O) transit time and calculated (C) expected transit time on the y-axis in minutes versus the time given as orbital periods of the known planet WASP-3b. We plot the previously published transit times as blue dots and our own new measurements as red dots. If there would be only one planet around the star WASP-3, then all points should be on one straight line. If there would be a second planet with 15 Earth masses and 3.75 day orbital period (called WASP-3c), then this second planet would modify the orbital period of the first known planet (WASP-3b, 2 Jupiter masses in 2 day orbit) in such a way as shown by the black line, which we have calculated. This is the best fitting configuration, i.e. indirect evidence for such a new planet WASP-3c. Credit: G. Maciejewski/Jena University.
The detection is now being followed up via radial velocity studies with the 10-meter Hobby-Eberly telescope in Texas, where the new planet’s existence can be confirmed. The gravitational interactions that make Transit Timing Variation so useful are studied in terms of period and amplitude to derive the parameters of the perturbing planet, a matter of intense computer work analyzing possible configurations in a given planetary system. As we refine TTV, it’s worth noting that the method is sensitive to small perturbing planets down to Earth mass. In fact, a ‘hot Jupiter’ whose orbit is affected by a one Earth mass planet will show a definite TTV signal of up to a minute, detectable by 1-meter class telescopes.
The paper is Maciejewski et al., “Transit timing variation in exoplanet WASP-3b,” accepted at Monthly Notices of the Royal Astronomical Society and available as a preprint. | 0.910242 | 3.945504 |
Were deviations in Jupiter’s magnetic field, recorded by Galileo’s magnetometer during a flyby of Europa in 2000, an indication of a cryovolcanic eruption? The data on this event have been evaluated by several independent groups in Europe and the US, an indication of how much interest such a plume would generate. If, like Enceladus, Europa occasionally blows off material from below the surface, we would have the possibility of collecting water from its ocean without having to drill through kilometers of ice.
Now a team of European Space Agency scientists led by Hans Huybrighs, working with colleagues at the Max Planck Institute for Solar System Research (MPS), has gone to work on the question, this time through the measurements made by Galileo’s Energetic Particles Detector (EPD), an instrument with roots both at MPS and the Applied Physics Laboratory of Johns Hopkins University (APL). EPD recorded significantly fewer fast-moving protons near Europa than expected during the same flyby. This adds weight to the conclusions of those finding evidence for a plume in the magnetometer data.
Jupiter’s magnetic field is twenty times stronger than Earth’s, extending far enough into space that Europa orbits within it. What Huybrighs and company set out to do was to simulate conditions during the flyby, modeling high-energy proton movements that correspond with what the EPD recorded.
The question raised by the EPD instrument is why these energetic protons were disappearing during the E26 flyby, an observation earlier considered to be caused by Europa itself obscuring the detector, making the measurement unreliable. But the paper makes the case that some of the proton depletion could only be explained by a plume of water vapor that disrupted Europa’s tenuous atmosphere and perturbed magnetic fields in the region. Indeed, the simulations are only successful under the assumption of a plume, whose effects are added into those caused by the atmosphere. Evidence for a plume noted by earlier researchers is thus strengthened by an analysis drawn from an independent dataset.
Image: Color image data from the Galileo mission recorded between 1995 and 1998 were used to create this depiction of Europa’s cracked and icy surface. The inset shows dark reddish, disrupted regions dubbed Thera and Thrace. Credit: Galileo Project, Univ. Arizona, JPL, NASA.
The authors’ conclusion also highlights how much we do not know about the environment at Europa, while pointing to a helpful tool for planning purposes on future missions:
Large uncertainties remain in the properties (density profile, 3D structure, temporal variability…) of Europa’s tenuous atmosphere and plumes (Plainaki et al., 2018). This study emphasizes that energetic ions are an important tool that can contribute to the detection and characterization of Europa’s tenuous atmosphere and plumes and probe its moon-magnetosphere interaction, independently of other methods. This is in particular relevant for the upcoming JUICE mission (Grasset et al., 2013), which has the instrumentation to detect both energetic ions and ENAs, using the Particle Environment Package (PEP)…
The ability of JUICE to detect energetic charged and neutral particles near Europa will help us spot future plumes. Note this ESA description of the Particle Environment Package:
A plasma package with sensors to characterise the plasma environment in the Jovian system.
PEP will measure density and fluxes of positive and negative ions, electrons, exospheric neutral gas, thermal plasma and energetic neutral atoms in the energy range from <0.001 eV to >1 MeV with full angular coverage. The composition of the moons’ exospheres will be measured with a resolving power of more than 1000.
For more on the science payload of this mission, with 10 instruments onboard, click here. JUICE launches in 2022 in a mission aimed at Europa, Callisto and eventual orbit at Ganymede.
The paper is Huybrighs et al., “An active plume eruption on Europa during Galileo flyby E26 as indicated by energetic proton depletions,” Geophysical Research Letters 12 May 2020 (abstract). | 0.825618 | 4.076794 |
Five years ago this week, ESA’s Rosetta mission flew by asteroid Steins en route to comet Churyumov–Gerasimenko, where it will finally arrive next year after a decade in space.
This image is based on data collected by Rosetta during its closest approach to Steins on 5 September 2008, at a distance of about 800 km of the 5 km-wide diamond-shaped asteroid.
It is best viewed using stereoscopic glasses with red–green or red–blue filters.
Around 40 impact craters are seen on the asteroid, including the large 2 km-wide and 300 m-deep crater at the ‘top’ of Steins, and a chain of several smaller craters that stretch from the asteroid’s north pole (bottom in this image) up to the large crater.
Rosetta has since passed by asteroid Lutetia in July 2010 and is now in deep-space hibernation. But at the end of January 2014 it will be roused from slumber to prepare for its rendezvous with comet 67P/Churyumov–Gerasimenko a few months later.
Rosetta will escort the comet around the Sun, witnessing for the first time how a frozen comet is transformed by the warmth of the Sun.
The mission also includes a lander, Philae, which will settle on the comet’s surface in November 2014 in the first landing of its kind.
Comets are considered to be the most primitive building blocks of the Solar System, and likely helped to ‘seed’ Earth with water, the very ingredient needed for life to flourish.
By studying the nature of the comet’s solid and gaseous constituents, Rosetta will help scientists to learn more about the role of comets in the evolution of the Solar System. | 0.818949 | 3.454935 |
A Remarkable Chance Encounter:
Thanks to happenstance and a 4-VA grant to investigate the origins of super massive black holes (SMBH), Professor of Physics and Astronomy Shobita Satyapal and her team discovered a noteworthy find: A distant colliding galaxy hosting a binary active galactic nucleus (AGN).
This significant revelation is important because although there are strong theoretical rationales why binary AGN should exist, finding them is extremely rare – as only a handful have currently been identified with separations of less than a few tens of light years apart. With Satyapal’s sighting, a supposition was developed that a significant population of binary AGNs may be hidden from optical wavelengths. A heavenly breakthrough.
It’s where you look and how you look
Thus begat a concerted collaborative effort between Satyapal’s group at Mason, with their expertise in analysis of X-ray data; Dr. Anca Constantin at Madison who established a program to study the reduction of data from the Large Binocular Telescope (LBT) in Arizona; and Dr. Sabrina Stierwalt from UVA — an expert on very large array (VLA) data.
- To determine the true frequency of binary AGNs and to estimate their black hole masses
- To compare AGN incidences and properties to host galaxy and merger potential
- To compare infrared-selected binary AGNs to optically-identified binary AGNs
Then, the search was on to find binary AGNs in a sample of 15 colliding galaxies for which the team secured highly competitive Chandra and XMM-Newton observations. Each participating university brought on both graduates and undergraduates to assist in data analysis and modeling.
They found a notable eight additional binary AGNs in their sample of 15 — increasing the fraction of known binary AGNs in the universe at these close separations by 30%!
What’s more, the study resulted in a NASA press release recognizing Mason; an accepted publication in the Astrophysical Journal (with another in the works). Further, the collaboration encouraged an undergrad from Madison to move forward into Mason’s graduate program — helping build an even stronger bridge between the two institutions.
“This 4-VA funding gave us the seed money which allowed us to do the exploring we needed at the outset of this project,” explains Satyapal. “What began as a lucky accident has morphed in to a statewide study which has received national and international attention and garnered additional research dollars – for that we are very grateful!”
- Shobita Satyapal
- James Madison
- Anca Constantin
- University of Virginia
- Sabrina Stierwalt
- Current and Former Students
- Paul McNulty, Ryan Pfeifle, Jason Ferguson, Jenna Cann
- Astrophysics Journal
- Secured Chandra and SMM-Newton observations | 0.864924 | 3.680082 |
Next stop the ocean worlds of Enceladus and Europa
Space news (planetary science: water worlds of the solar system; Enceladus and Europa) –planets and moons around the solar system and exoplanets across the universe covered with water–
The solar system’s awash in water! NASA missions have provided verifiable facts showing ocean worlds and moons exist in our solar system and beyond,other than Earth. Planetary bodieswhere water is locked in a frozen embrace and even flowing beneath miles of ice. Liquid water exobiologists are keen to explore for life forms they would love to meet and get to know a little better during the next phase of the human journey to the beginning of space and time. Watch this YouTube video on NASA’s search for life on the ocean worlds of the solar system.
Papers published bythe journal Science and written by Cassini mission scientists and researchers working with the Hubble Space Telescope indicate hydrogen gas believed pouring from the subsurface ocean of Enceladus could potentially provide chemical energy life could use to survive and evolve. Watch this YouTube videocalled “NASA: Ingredients for Life at Saturn’s moon Enceladus“, itshowsthe proof scientists used to come to these conclusions. Their work provides new insights concerning possible oceans of water on moons of Jupiter and Saturn and other ocean moons in the solar system and beyond.
“This is the closest we’ve come, so far, to identifying a place with some of the ingredients needed for a habitable environment,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at Headquarters in Washington. ”These results demonstrate the interconnected nature of NASA’s science missions that are getting us closer to answering whether we are indeed alone or not.”
Researchers believe they have found evidence indicating hydrogen gas could be pouring out of hydrothermal vents on the floor of Saturn’s moon Enceladus and into these oceans of water. Any microbes existing in these distant waters could use this gas as a form of chemical energy to operate biological processes. By combining hydrogen with carbon dioxide dissolved in this ocean of water in a chemical reaction called methanogenesis, geochemists think methane could be produced which could act as the basis of a tree of life similar to the one observed on Earth.
On Earth, this process is thought to be at the root of the tree of life, and could even be essential, critical to the origin of life on our little blue dot. Life existing on our planet requires three main ingredients, liquid water, a source of energy for metabolic processes, and specific chemical ingredients to develop and continue to thrive. This study shows Enceladus could have the right ingredients for life to exist, but planetary scientists and exobiologists are looking for evidence of the presence of sulfur and phosphorus.
Previous data shows the rocky core of this moon is similar to meteorites containing these two elements, so they’re thought to be chemically similar in nature, and scientists are looking for the same chemical ingredients of life found on Earth, primarilycarbon, nitrogen, oxygen, and of course hydrogen, phosphorus, and sulphur.
“Confirmation that the chemical energy for life exists within the ocean of a small moon of Saturn is an important milestone in our search for habitable worlds beyond Earth,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.
Cassini detected hydrogen in plumes of gas and frozen matter spewing from Enceladus during the spacecraft’s deepest pass over its surface on October 28, 2015. This combined with previous data obtained by Cassini’s Ion and Neutral Mass Spectrometer (INMS) during earlier flybys around 2005,helped scientists determine that nearly 98 percent of the material spraying from the surface of the moon is water. The remaining two percent is thought to be around 1 percent hydrogen with some carbon dioxide, methane,ammonia and assorted unknown molecules in the mix.
Cassini has shown us two independent detections of possible water spewing from the surface of Enceladus. NASA and its partners are currently looking over proposals to send spacecraft to determineif there is an ocean of water beneath its surface by taking a sample. The Europa Life Finder (ELF)is the proposal NASA’s seriously looking at undertaking at this point, but reports indicate a few other proposals are also being discussed.We’ll provide additional information on other proposals as they’re released to media outlets.
“Although we can’t detect life, we’ve found that there’s a food source there for it. It would be like a candy store for microbes,” said Hunter Waite, lead author of the Cassini study.
Two different observations of possible plumes of water spraying from the icy surface of Saturn’s moon Enceladus provides proof hydrothermal activity is occurring beneath. Geophysicists believe hot water is combining chemically with rock and other matter at the bottom of an ocean of water underneath its icy surface to produce hydrogen gas. Hydrogen gas exobiologists think could be used as energy, food of a sort, to sustain life forms exobiologists want to meet and learn more about. A meeting that would change our place in the cosmos, the way we think about the universe, and reality.
Astronomers and researchers working with the Hubble Space Telescope in 2016 reported on an observation of a possible plume erupting from the icy surface of Europa in the same general location Hubble observed a possible plume in 2014. This location also corresponds to the unusually warm region with cracks in the icy surface observed by NASA’s Galileo spacecraft back in the 1990s.This provides evidence this phenomenon could be periodic, intermittent in this region of the moon. Mission planners are looking at this region as a possible location to obtain a sample ofwater erupting from a possible ocean of water beneath its icy surface. Watch this video on Europa.
Estimates of the sizeof this most recently observed plume indicate it rose about 62 miles (~100 kilometers) from the surface of Europa, while the plume in 2014 only reached a height of around 30 miles (50 kilometers).
“The plumes on Enceladus are associated with hotter regions, so after Hubble imaged this new plume-like feature on Europa, we looked at that location on the Galileo thermal map. We discovered that Europa’s plume candidate is sitting right on the thermal anomaly,” said William Sparks of the Space Telescope Science Institute in Baltimore, Maryland. Sparks led the Hubble plume studies in both 2014 and 2016.
One interesting thought’s the plumes and the hot spot is somehow linked. If this is the case, it could mean the vented water’s falling onto the surface of the moon, which would change the structure and chemistry of the surface grains and allow them to retain heat longer than the surrounding region. This location would be a great place to search for the ingredients of life and a possible entry point into an ocean of water beneath.
These observations by the Hubble Space Telescope and future looks enable future space missions to Europa and other ocean worlds in the solar system. Specifically, laying the groundwork for NASA’s Europa Clipper mission, which is setfor a launch sometime in the 2020s.
“If there are plumes on Europa, as we now strongly suspect, with the Europa Clipper we will be ready for them,” said Jim Green, Director of Planetary Science, at NASA Headquarters.
NASA has indicated they’re looking to identify a possible site with persistent, intermittent plume activity as a target location for a mission to Europa to explore using its powerful suite of science instruments. Another team’s currently at work on a powerful ultraviolet camera to add to the Europa Clipper that would offer data similar to that provided by the Hubble Space Telescope, while some members of the Cassini team areworking on a very sensitive, next generation INMS instrument to put on the spacecraft.
Water’s the story of life on Earth! Science has shown it played and plays the main part in the birth,evolution, and sustenance of life on Earth.
NASA’s planning on taking the human journey to the beginning of space and time to the ocean worlds of the solar system during the decades ahead. To search for the ingredients of life and even possibly simple one-celled life forms, of an unknown type. We plan on going along for the ride to have a look for ourselves and we hope to see your name on the ship manifest. We’ll save a seat for you.
Join the human journey to the beginning of space and time by taking part in NASA’s Backyard Worlds: Planet 9. Participants take part in the search for hidden worlds between Neptune and Proxima Centauri. | 0.884318 | 3.255762 |
Stargazing can be a lonely preoccupation. Sometimes its so hard to convince your loved ones to travel to the middle of nowhere in the dark to see a bunch of sparkly things, as beautiful as they may be.
Most seasoned stargazers have spent an evening or twenty alone in the middle of some farmer’s field, lost in the vastness of space and, frankly, scared out of their minds.
The sounds of the night are the scariest part — the rustle of a corn stalk can be the sure sign that Bigfoot is approaching stealthily through the darkness.
Come on, it could have been Bigfoot. I don’t usually stop to notice any details. I’m too busy running for the car to see the blood dripping from its hideous, razor-sharp fangs.
Take heart, solitary stargazers. This time of year, the patron star of lonely astronerds afraid of giant, beast-like humanoids sits low and forlorn in the south. It’s Fomalhaut, the “Solitary One.”
Look directly south around midnight and you’ll see a single star amidst a large patch of darkness. The other stars in Piscis Austrinus, the Southern Fish, are too faint to see from all but the darkest rural skies. Fomalhaut sticks out like Bigfoot’s big toe.
The star’s name comes from the Arabic expression “Fum al Hut,” which means the “Mouth of the Fish.” It is traditionally associated with the coming of autumn and the loss of summer. Add to that its isolated location, and you have one depressing star.
Because it never gets very high above the horizon, it often takes on a dim orange cast as its light is filtered through the thick layer of air close to the horizon.
Don’t let appearances fool you. Fomalhaut is a hot, young star that burns with an almost pure, white flame.
It has the distinction of being one of the first stars around which a disk of cool dust and gas was discovered. Astronomers believe that such disks eventually form into planets like those in our own solar system. Fomalhaut’s dusty disk was discovered in 1983 by IRAS, the Infra-Red Astronomical Satellite, which was sent into orbit to examine not the light, but the heat, emanating from the stars.
In 1908, astronomers announced the existence of a planet orbiting just inside the outer debris ring. It is massive, at least as large as Neptune and perhaps three times the size of our largest planet, Jupiter. Fomalhaut b, as it is officially called, was the first-ever extra-solar planet photographed in visible light by the Hubble Space Telescope.
In 2014, the International Astronomical Union began public voting to give informal names of some of the extra-solar planets. In December 2016, they announced that Fomalhaut’s planet would be forever known as Dagon.
Most people have heard the story of Sampson, the great Israelite hero and strong man who was seduced by the Philistine woman Delilah. However, they don’t know that the story has an astronomical connection.
Sampson derived his strength from his body hair, and men of his clan were not permitted to shave or cut. Delilah learned his secret and had his hair shaved off. The weakened Sampson was at the mercy of his Philistine enemies, who had his eyes gouged out.
The Philistines decided to offer a sacrifice to the fish-god Dagon in honor of their triumph. It’s hard to blame them. Sampson had slain more than a few Philistines in his time.
So the Philistines had an enormous debauch in Dagon’s temple in the town of Gaza. To add insult to injury, they paraded the blinded and weakened Sampson before the assembled multitude. Summoning his last reserve of strength, Sampson pushed on the pillars of the temple, and managed to take thousands more Philistines with him as the falling temple debris crushed him.
Dagon is none other than the star Fomalhaut. The Philistines worshipped the starry representation of the god at their temple at Gaza. The IAU voters couldn’t rename the star, so they very rightly restored its Biblical connection by renaming its planet.
The temple’s rubble has long since turned to dust, but the star remains as a symbol of Sampson’s power. At the time of his death, Sampson was as alone and isolated as the star. Surrounded by his enemies, he was able to summon the power to triumph.
I hope it’s clear this weekend. Saturn is still visible at our Friday night program, and I’ll be there for that, of course. But Saturday night is free. It just seems like a good time to stand alone under the stars and watch Fomalhaut flicker in the south. Watch out, Bigfoot. Take heed, Dagon. Here I come.
Tom Burns is director of the Perkins Observatory in Delaware. | 0.846033 | 3.550486 |
Earth-Mars Transfer Trajectory
An Earth-Mars transfer trajectory is an orbital path which a spacecraft follows to travel between Earth and Mars. Several types of trajectories have been studied, but all will satisfy the following conditions:
- The starting point must be near the Earth in its orbit around the sun
- The ending point must intersect Mars in its orbit around the sun
- The intervening trajectory must be heliocentric, though one or more gravitational swing-bys of other bodies are allowed
Not all Mars transfer orbits are Hohmann transfers. This is due to the difference in the plane of Earth and Mars's orbit, and can also be due to constraints on launch windows. There are many variations on this theme, such as whether the spacecraft ends in a Mars-centered orbit or if the spacecraft directly enters the atmosphere from the heliocentric transfer orbit. Other less common variations include the starting orbit at Earth, which could be a low Earth orbit or could instead the mission could begin from geostationary transfer orbit (GTO) as in the MEGA proposals of the late 90's, or one could vary the heliocentric portion of the flight to include a low-thrust trajectory.
The NASA Ames research center offers a practical Trajectory Browser application than can calculate Mars transfer orbits.
A launch period is a span of days during which a launch vehicle can place the spacecraft in the desired Earth-Mars transfer orbit. A launch period is different from a launch window which is a specific time that a launch can take place on a particular day in the launch period. There are many launch windows in a launch period. Sometimes the phrase launch opportunity is used to refer to the specific year in which a launch period takes place.
Launch periods are generally constrained by the power of the launch vehicle whereas launch windows are also constrained by launch geometry. One way to visualize an acceptable launch period for various values of delta-v is a porkchop plot, which plots contours of constant delta-V on top of launch dates and landing dates. Pick a value of delta-V, and then use that contour to determine the launch period by observing the earliest launch date and latest launch date.
The gap in the porkchop plot is caused by non-planar delta-v in the transfer burns. Since the Earth and Mars orbit in slightly different planes, the most expensive time to launch is when the earth and Mars are at points where their planes are separated by the maximum amount. Conversely, the cheapest time to launch is when their planes intersect.
One drawback of porkchop plots is that they are only for single-arc transfers, which is why they have such large gaps as a result of launch and arrival plane changes. A different transfer trajectory could be constructed which uses a mid-course plane change maneuver at the intersection of the Earth and Mars orbital planes. However, most launch vehicles would not offer this capability.
There are other real-world considerations which affect the launch period; the ability of MRO to be at the right place at the right time to serve as a relay satellite during entry, descent, and landing constrained the end of Insight's launch period.
Typically a mission will first launch into a relatively low Earth-centered parking orbit, then it will coast in that orbit for a variable amount of time, and finally the second or third stage of the launch vehicle will inject the spacecraft into a Mars transfer orbit. This injection can either take place all at once, as with the 8 minute burn for Curiosity's launch, or it can take place over several orbits with gradual apogee-raising maneuvers as in the case of Mars Orbiter Mission.
The parking orbit can be of any inclination. A heavy spacecraft like Curiosity may need to launch into a lower inclination parking orbit so it can take more advantage of the Earth's rotation at launch, however a small spacecraft like Insight might not. Insight launched south from Vandenberg into a polar orbit, coasted for 3/4 of a parking orbit, and the second stage reignited its engines approximately over Alaska to place Insight on the Mars transfer orbit.
At the completion of this Mars transfer insertion burn, the spacecraft will not be exactly on its final course. The spacecraft will be set on a course which intentionally misses Mars so that the non-sterilized launch vehicle does not accidentally hit and contaminate the surface of Mars. After the Mars-transfer orbit burn is completed, the spacecraft will separate from the launch vehicle. The spacecraft will eventually perform a trajectory correction maneuver which will set it on the correct course, but the expended rocket parts will remain on their initial trajectory and miss Mars.
There are other ways of leaving Earth. One such way is the Moon and Earth Gravity Assist (MEGA) scheme, which has never been performed. In this scheme, a small (~200 kg) spacecraft hitches a ride as a secondary payload on a launch to geostationary transfer orbit (GTO). Once in GTO, the spacecraft will perform a burn at perigee which will raise its apogee enough to take it out beyond the Moon, but not quite escape Earth's gravitational pull. At this far apogee the spacecraft might perform a small burn to target a lunar gravity assist as it comes back towards the Earth. Finally, at the next perigee, the spacecraft will perform its Mars transfer orbit insertion burn.
Another way to escape Earth would be a low-thrust trajectory, where the spacecraft slowly spirals out away from Earth until its eventual escape into heliocentric orbit.
Regardless of the escape scheme, practical considerations impose constraints on the trajectory and timing of maneuvers. For instance, a mission might need to time things so that spacecraft separation occurs in view of a deep space tracking station such as Goldstone.
I'm not sure what is used for targeting the initial transfer orbit insertion burn, but the trajectory correction maneuver burns target a point on the "B-plane" of Mars. The B-plane is defined in a JPL glossary as the "plane perpendicular to the asymptote of the incoming hyperbolic trajectory of the object relative to the Earth." I think of it as the "bullseye" plane, which is the plane of the dartboard from the perspective of the person throwing darts. B-plane targeting was originally developed for gravity-assist maneuvers, but it has come to be used for missions where the destination is the planet itself as well.
Aerocapture and hypersonic entry
Using the concepts of Aerocapture and hypersonic entry a vehicle can arrive at Mars with a high residual velocity, and use friction with the planetary atmosphere to slow down and eventually land. This allows for much shorter travel times with about the same fuel use as more conventional transfer orbits. An average Hohmann transfer orbit to Mars requires 259 days and a delta-v of 3,9 km/s. An hyperbolic orbit depending on aerocapture for braking can reduce this to 90-150 days depending on the year of travel. For example in aug. 2020 for a delta-V of 4,8 km/s Mars could be reached in 96 days according to the Trajectory Browser .
topics to elaborate on
- opposition vs conjunction class transfers
- plane changes
- low-thrust trajectories
- earth orbit part, launch sites, equatorial vs polar parking orbits (or lack of difference between them)
- GTO to Mars transfer scheme
- mars capture schemes: aerobraking, ballistic capture
- https://trs.jpl.nasa.gov/bitstream/handle/2014/44336/13-0679_A1b.pdf?sequence=1 Ryan C. Woolley and Charles W. Whetsel "On the nature of Earth-Mars porkchop plots" 2014 AAS
- Paul Penzo, "Mission design for Mars mission using the Ariane ASAP launch capability," 1999. https://trs.jpl.nasa.gov/bitstream/handle/2014/16879/99-0288.pdf?sequence=1 | 0.801447 | 3.849209 |
Dark Energy Survey scientists have developed a new algorithm to match Type Ia supernovae (SNe Ia) to their host galaxies. These supernovae are critical tools for understanding the history of our Universe. In 1998, these incredibly bright stellar explosions were used to determine that our Universe is not only expanding, but that this expansion is accelerating!
We can use the brightness of a SN Ia explosion to estimate distances in space: the brighter an explosion is, the closer it is to us. By studying the relationship between the distance to the event and how long ago it occurred, signified by its redshift, we can figure out at what rate the Universe has been expanding at different times. This is crucial information in figuring out the overall makeup of our Universe, such as how much of our Universe is made of dark energy and what properties dark energy may have.
Knowing the redshift precisely is incredibly important – using the wrong redshift can dramatically change your predictions! While the most reliable way to confirm a redshift is by looking at the spectrum (the amount of light at each visible wavelength) of the SN Ia itself, obtaining real-time spectra for the thousands of SNe detected by DES is not an easy, or realistic, task. However, getting redshifts of the host galaxies (i.e., the galaxies in which the SNe explode) long after the SNe have faded away is easier to do. While the DES telescope in Chile does not take spectra itself as part of the survey, DES has partnered with programs such as OzDES (an Australian-led team) that measures spectra, often following up DES discovered objects.
Using these host galaxy redshifts in lieu of SN redshifts is common practice when you have such a large set of SNe Ia. But this relies on the fact that you’re correctly matching the explosion to its host! In theory, this should be pretty straightforward – just pick the galaxy closest to the SN Ia. However, determining what is “closest” becomes tricky when your data consists of two-dimensional images that are actually projections of a three-dimensional space.
As shown in Figure 1, it can be unclear which galaxy is the correct host for a given SN Ia. In the figure, the center of the smaller galaxy to the right is “closer” to the explosion than the larger galaxy on the left; yet, it’s possible that the smaller galaxy is actually a distant background galaxy, unassociated with the SN.
Dr. Ravi Gupta and his colleagues in the DES supernova working group have created a new, automated algorithm to match SNe Ia to their hosts. This technique uses information about galaxies near the SN Ia, such as their shapes, sizes, and orientations. Another piece of information used is something called the host confusion parameter. The host confusion parameter describes, in a numerical way, the degree to which a SN Ia might get mismatched to the wrong host.
Quantifying host confusion turned out to be useful, but this parameter by itself was not as powerful of a tool as the authors had hoped. This led them to consider using machine learning, which harnesses the power of computers to solve problems with greater flexibility by recognizing patterns in large amounts of data. “The idea of using machine learning came to me when I was trying to write down some optimal function for quantifying the level of host confusion [the host confusion parameter], and I thought: ‘A computer could probably figure this out better than I could,’ ” says Dr. Gupta. So they proceeded to develop a machine learning classifier that uses information about the galaxies near each SN (including the host confusion parameter) to determine the probability that the SN Ia is correctly matched to its host galaxy.
This new algorithm was tested with catalogs of galaxies and simulated SNe Ia positions, and results in a matching accuracy of 97%. The method Dr. Gupta and his colleagues created can be used for other supernova programs besides DES, but in their work they caution that exact results are dependent on the details of the survey. In the future, they hope to study how the cases where the SN Ia is mismatched will affect other science results using SNe Ia.
You can read more about this analysis, Host Galaxy Identification for Supernova Surveys, online on the arxiv.
About the Paper Author
Ravi Gupta is a post-doc at Argonne National Laboratory. He did his graduate work on SN Ia host galaxies at the University of Pennsylvania and has been working with the DES supernova group for the past 5 years. His hobbies include music, movies, photography, and drawing. You can find some of his drawings in The Dark Bites.
About The DArchive Authors & Editors
Rachel C. Wolf is an astrophysics PhD candidate at the University of Pennsylvania. She is primarily interested in how to best use Type Ia supernovae to understand more about the evolution of our universe. Most of her work has focused on studying correlations between supernova brightness and host-galaxy properties and on creating new statistical techniques to compare observational data to cosmology theory. Rachel is also very passionate about science education and public outreach. She is involved in many projects in the Philadelphia community and serves as one of the co-coordinators of Education & Public Outreach for DES.
Chicago. He works on various projects studying the large scale structure
of the Universe using the millions of galaxies DES observes. These
projects include galaxy clustering, correlations of structure with the
cosmic microwave background, and using the structure of the Universe to infer redshifts of galaxies. Ross is also an active science communicator, volunteering at Chicago’s Adler Planetarium as well as writing and editing for The Darchives. He also loves observing for DES in Chile, where he has observed more than 30 nights. | 0.840364 | 4.127209 |
What��������s higher than the Himalayas? Although the Himalayan Mountains are the tallest on planet Earth, they don’t measure up to the Milky Way. Visible above the snow-capped mountains in the featured image is the arcing central band of our home galaxy. The bright spot just above the central plane is the planet Jupiter, while the brightest orange spot on the upper right is the star Antares. The astrophotographer braved below-zero temperatures at nearly 4,000-meters altitude to take the photographs that compose this image. The featured picture is a composite of eight exposures taken with same camera and from the same location over three hours, just after sunset, in 2019 April, from near Bimtang Lake in Nepal. Over much of planet Earth, the planets Mercury (faint) and Venus (bright) will be visible this week after sunset.
Inside the head of this interstellar monster is a star that is slowly destroying it. The huge monster, actually an inanimate series of pillars of gas and dust, measures light years in length. The in-head star is not itself visible through the opaque interstellar dust but is bursting out partly by ejecting opposing beams of energetic particles called Herbig-Haro jets. Located about 7,500 light years away in the Carina Nebula and known informally as Mystic Mountain, the appearance of these pillars is dominated by dark dust even though they are composed mostly of clear hydrogen gas. The featured image was taken with the Hubble Space Telescope. All over these pillars, the energetic light and winds from massive newly formed stars are evaporating and dispersing the dusty stellar nurseries in which they formed. Within a few million years, the head of this giant, as well as most of its body, will have been completely evaporated by internal and surrounding stars.
The largest canyon in the Solar System cuts a wide swath across the face of Mars. Named Valles Marineris, the grand valley extends over 3,000 kilometers long, spans as much as 600 kilometers across, and delves as much as 8 kilometers deep. By comparison, the Earth’s Grand Canyon in Arizona, USA is 800 kilometers long, 30 kilometers across, and 1.8 kilometers deep. The origin of the Valles Marineris remains unknown, although a leading hypothesis holds that it started as a crack billions of years ago as the planet cooled. Several geologic processes have been identified in the canyon. The featured mosaic was created from over 100 images of Mars taken by Viking Orbiters in the 1970s.
Stars shine and satellites glint in this clear, dark, night sky over Wannon Falls Reserve, South West Victoria, Australia. In fact the fuzzy, faint apparition above the tree tops is the only cloud visible, also known as the Large Magellanic Cloud, satellite galaxy of our own Milky Way. In the foreground, an Omphalotus nidiformis (ghost fungus) from planet Earth shines with a surprisingly bright bioluminescence. Like the Magellanic cloud, the ghost fungus was easily seen with the eye. Its ghostly glow was actually a dull green, but it appears bright green in digital camera picture. Two images were blended to create the scene. One focused on the distant stars and Large Magellanic Cloud some 160,000 light-years away. Another was focused on the foreground and glowing fungus several light-nanoseconds from the camera lens.
With natal dust clouds in silhouette against glowing atomic gas, this colorful and chaotic vista lies within one of the largest star forming regions in the Milky Way galaxy, the Great Carina Nebula. The telescopic close-up frames a field of view about 80 light-years across, a little south and east of Eta Carinae, the nebula’s most energetic and enigmatic star. Captured under suburban skies improved during national restrictions, a composite of narrowband image data was used to create the final image. In it, characteristic emission from the nebula’s ionized sulfur, hydrogen, and oxygen atoms is mapped to red, green, and blue hues, a color palette also popular in Hubble Space Telescope images. The celestial landscape of bright ridges of emission bordered by cool, obscuring dust lies about 7,500 light-years away toward the southern constellation Carina.
Just as the Moon goes through phases, Venus’ visible sunlit hemisphere waxes and wanes. This composite of backyard telescopic images illustrates the steady changes for Venus during its current stint as our evening star, as the inner planet grows larger but narrows to a thin crescent. Images from bottom to top were taken during 2020 on dates February 27, March 20, April 14, April 24, May 8, and May 14. Gliding along its interior orbit between Earth and Sun, Venus grows larger during that period because it is approaching planet Earth. Its crescent narrows, though, as Venus swings closer to our line-of-sight to the Sun. Closest to the Earth-Sun line but passing about 1/2 degree north of the Sun on June 3, Venus will reach a (non-judgmental) inferior conjunction. Soon after, Venus will shine clearly above the eastern horizon in predawn skies as planet Earth’s morning star. After sunset tonight look for Venus above the western horizon and you can also spot elusive innermost planet Mercury.
It is not a coincidence that planets line up. That’s because all of the planets orbit the Sun in (nearly) a single sheet called the plane of the ecliptic. When viewed from inside that plane — as Earth dwellers are likely to do — the planets all appear confined to a single band. It is a coincidence, though, when three of the brightest planets all appear in nearly the same direction. Such a coincidence was captured about a month ago. Featured above, Earth’s Moon, Mars, Saturn, and Jupiter were all imaged together, just before sunrise, from the Black Sea coast of Bulgaria. A second band is visible diagonally across this image — the central band of our Milky Way Galaxy. If you wake up early, you will find that these same planets remain visible in the morning sky this month, too. | 0.928245 | 3.689089 |
Looking up at the night sky — expansive and seemingly endless, stars and constellations blinking and glimmering like jewels just out of reach — it’s impossible not to wonder: Are we alone?
For many of us, the notion of intelligent life on other planets is as captivating as ideas come. Maybe in some other star system, maybe a billion light years away, there’s a civilization like ours asking the exact same question.
Imagine if we sent up a visible signal that could eventually be seen across the entire universe. Imagine if another civilization did the same.
The technology now exists to enable exactly that scenario, according to UC Santa Barbara physics professor Philip Lubin, whose new work applies his research and advances in directed-energy systems to the search for extraterrestrial intelligence (SETI). His recent paper “The Search for Directed Intelligence” appears in the journal REACH – Reviews in Human Space Exploration.
“If even one other civilization existed in our galaxy and had a similar or more advanced level of directed-energy technology, we could detect ‘them’ anywhere in our galaxy with a very modest detection approach,” said Lubin, who leads the UCSB Experimental Cosmology Group. “If we scale it up as we’re doing with direct energy systems, how far could we detect a civilization equivalent to ours? The answer becomes that the entire universe is now open to us.
“Similar to the use of directed energy for relativistic interstellar probes and planetary defense that we have been developing, take that same technology and ask yourself, ‘What are consequences of that technology in terms of us being detectable by another ‘us’ in some other part of the universe?’” Lubin added. “Could we see each other? Can we behave as a lighthouse, or a beacon, and project our presence to some other civilization somewhere else in the universe? The profound consequences are, of course, ‘Where are they?’ Perhaps they are shy like us and do not want to be seen, or they don’t transmit in a way we can detect, or perhaps ‘they’ do not exist.”
The same directed energy technology is at the core of Lubin’s recent efforts to develop miniscule, laser-powered interstellar spacecraft. That work, funded since 2015 by NASA (and just selected by the space agency for “Phase II” support) is the technology behind billionaire Yuri Milner’s newsmaking, $100-million Breakthrough Starshot initiative announced April 12.
Lubin is a scientific advisor on Starshot, which is using his NASA research as a roadmap as it seeks to send tiny spacecraft to nearby star systems.
In describing directed energy, Lubin likened the process to using the force of water from a garden hose to push a ball forward. Using a laser light, spacecraft can be pushed and steered in much the same way. Applied to SETI, he said, the directed energy system could be deployed to send a targeted signal to other planetary systems.
“In our paper, we propose a search strategy that will observe nearly 100 billion planets, allowing us to test our hypothesis that other similarly or more advanced civilizations with this same broadcast capability exist,” Lubin said.
“As a species we are evolving rapidly in photonics, the production and manipulation of light,” he explained. “Our recent paper explores the hypothesis: We now have the ability to produce light extremely efficiently, and perhaps other species might also have that ability. And if so, then what would be the implications of that? This paper explores the ‘if so, then what?’”
Traditionally and still, Lubin said, the “mainstay of the SETI community” has been to conduct searches via radio waves. Think Jodie Foster in “Contact,” receiving an extraterrestrial signal by way of a massive and powerful radio telescope. With Lubin’s UCSB-developed photonics approach, however, making “contact” could be much simpler: Take the right pictures and see if any distant systems are beaconing us.
“All discussions of SETI have to have a significant level of, maybe not humor, but at least hubris as to what makes reason and what doesn’t,” Lubin said. “Maybe we are alone in terms of our technological capability. Maybe all that’s out there is bacteria or viruses. We have no idea because we’ve never found life outside of our Earth.
“But suppose there is a civilization like ours and suppose — unlike us, who are skittish about broadcasting our presence — they think it’s important to be a beacon, an interstellar or extragalactic lighthouse of sorts,” he added. “There is a photonics revolution going on on Earth that enables this specific kind of transmission of information via visible or near-infrared light of high intensity. And you don’t need a large telescope to begin these searches. You could detect a presence like our current civilization anywhere in our galaxy, where there are 100 billion possible planets, with something in your backyard. Put in context, and we would love to have people really think about this: You can literally go out with your camera from Costco, take pictures of the sky, and if you knew what you were doing you could mount a SETI search in your backyard. The lighthouse is that bright.” | 0.922158 | 3.26484 |
The new measurements of the Universe’s expansion rate, directed by astronomers from the University of California, Davis, have added some more spice to the puzzle: a fundamental constant’s estimations made with diverse techniques keep yielding dissimilar answers. “There’s so much of enthusiasm, a lot of bafflement and from my standpoint, it’s too much fun,” stated Chris Fassnacht, Physics Professor at UC Davis and an associate of the international SHARP/H0LICOW association that worked out the measurement utilizing the W.M. Keck telescopes situated in Hawaii.
The Universe’s expansion id described as Hubble constant and stated in kilometers per second per megaparsec. It enables researchers to decipher the Universe’s age and size as well as the distances between things. Fassnacht, graduate student Geoff Chen, and team observed light from very far-off galaxies that are twisted and divided into several pictures by the galaxies’ lensing effect between the source and the Blue Planet. By computing the time delay for light to stir diverse routes via the foreground lens, the Hubble constant can be estimated by the team. Utilizing the W.M. Keck telescopes’ adaptive optics technology, the research team reached at a guesstimate of 76.8 kilometers per second per megaparsec. Utilizing the records from the Hubble Space Telescope and the same before-mentioned technique, the H0LICOW team divulged a guesstimate of 71.9 in 2017.
On a similar note, the latest SHARP/H0LICOW estimations are analogous to that made by a group directed by Adam Reiss of Johns Hopkins University, 74.03, making use of measurements of a cluster of variable stars known as the Cepheids. However, it is quite a lot distinct from estimations of the Hubble constant from a completely distinct method founded on the cosmic microwave background. That technique, derived from the Big Bang’s afterglow, presents a Hubble constant of 67.4, considering that the Universe’s standard cosmological model is accurate. | 0.815689 | 3.803345 |
The Large Synoptic Survey Telescope (LSST) is one of the largest astronomy projects of the next decade. It aims to survey 10 billion galaxies out to a redshift of four including the ability to detect objects 100 times fainter than those seen with current large surveys. LSST will take pictures of the entire southern sky every few days for a decade, creating a motion picture of the heavens. Comparing these images will allow scientists to, for example, see when stars change in brightness or explode.
OKC researchers will be at the heart of this groundbreaking project thanks to a generous research project grant from the Knut and Alice Wallenberg (KAW) Foundation. The KAW project, entitled “Understanding the Dynamic Universe”, is led by Hiranya Peiris with Co-Is Ariel Goobar, Jesper Sollerman, Matthew Hayes, and Jens Jasche. It will allow OKC researchers to discover and study transient phenomena. Also, researchers will learn about dark matter by mapping its distribution and evolution and studying low surface brightness galaxies which are currently not explained in cold dark matter galaxy formation scenarios.
Hiranya says, “in the spirit of interdisciplinary collaboration underlying the Oskar Klein Centre, this grant will get researchers in the Physics and Astronomy Departments working together in new ways, bringing different strands of expertise to bear on some of the biggest questions in physics. I am particularly looking forward to that interdisciplinary aspect.”
Connecting the structure of the early universe, as seen in the cosmic microwave background, to the structures we see in the nearby universe is one of the goals of cosmology. This is complicated by the fact that galaxies are embedded in a web of dark matter whose structure is not explicitly visible. A detailed map of the dark matter distribution and its evolution can be made from the enormous LSST galaxy catalog using Bayesian Origin Reconstruction from Galaxies, a method developed by co-I Jens Jasche. Jens says, “for the first time, we might be able to discriminate between a cosmological constant and models of dark energy or large scale modifications of gravity that are believed to affect the growth of cosmological structures.“
Understanding the connection between galaxies and dark matter is important for probing the fundamental physics of the dark matter models we use today. Recently discovered types of low surface brightness, dark matter dominated, galaxies are unexplained in current cold dark matter models. Co-I Matthew Hayes says, “my part is to conduct a galaxy survey, targeting the lowest possible surface brightnesses we can reach. The ultra-deep co-adds from a telescope like LSST will be optimal for this kind of work, and the idea is to create a representative census of faint galaxies that are missing from surveys which used telescopes that are designed for compact source observations.”
Another LSST research focus at the OKC will be on rare cosmic explosions. Co-I Ariel Goobar says, “LSST will allow us to discover and study transient phenomena which are either too rare, too faint or too fast for existing telescopes. Some exciting objects we are sure to find are gravitationally lensed supernovae, from which we can measure the expansion rate of the Universe, and possibly detect the first generation of cosmic explosions. History also shows that opening new windows to the Universe is typically rewarded with the discovery of unknown phenomena. Exploration of short time-scales over large cosmic volumes could very well help us chart new physics territory. Ultimately, we hope to be able to resolve the dark matter and dark energy puzzles.”
Co-I Jesper Sollerman says, “LSST is really Big Science, and KAW grants are important for Swedish scientists who want to be part of such projects.” | 0.87163 | 3.9676 |
Ground zero for the impact that caused a Mars mega-tsunami more than 3 billion years ago may have been found.
The meteor that spawned that ancient flood probably blasted out Lomonosov Crater, a 75-mile-wide (120 kilometers) hole in the ground in the icy plains of the Martian Arctic, a new study reports.
Lomonosov's large size suggests that the impactor itself was big — similar in scale to the 6-mile-wide (10 km) asteroid that hit Mexico's Yucatan Peninsula 66 million years ago, sparking a mass extinction that killed off 75% of Earth's species, including the dinosaurs.
Such big space rocks don't hit the Red Planet (or Earth) very often. So, the new study provides some important clues about Mars' ancient northern ocean, and the planet's past potential to host life as we know it, team members said.
"The implication is that the ocean would have retained a liquid component for a very long time," study co-author Alexis Rodriguez, a senior scientist at the Planetary Science Institute in Tucson, Arizona, told Space.com. He offered 4 million to 5 million years as a representative figure, but stressed that the number is just an estimate.
A cold and mysterious ocean
Mars' big, salty northern ocean likely formed about 3.4 billion years ago. The ocean's existence is widely accepted by Mars researchers, Rodriguez said, but there is considerable debate about its nature.
For example, some scientists believe the ocean was relatively long-lived, if quite cold. But others don't think the ancient Martian climate could have supported stable bodies of surface water for long, and therefore argue that the ocean froze over very quickly — perhaps in a few thousand years or less.
The new study, which was published in late June in the Journal of Geophysical Research: Planets, bolsters the former viewpoint.
Rodriguez and his colleagues, led by François Costard of the French National Center for Scientific Research, built upon several years of previous research into the ocean and its imprints on the landscape of ancient Mars.
For example, Rodriguez led a 2016 study that identified huge lobes in the northern plains — features that strongly resemble marks left by tsunamis here on Earth. The team determined that the lobes were carved out by two different mega-tsunamis, which flooded the region more than 3 billion years ago.
Mars does not have significant plate-tectonic activity, so the big waves were probably unleashed by impacts. So, Costard, Rodriguez and their colleagues hunted for craters left behind by the cosmic culprits, narrowing the search over the next few years.
That search may now be over, at least for one of the two impactors. Multiple lines of evidence point to Lomonosov, the scientists report in the new study. For example, Lomonosov is in the right place, it's the right age (as determined by crater counts), and it looks a lot like marine craters here on Earth.
Lomonosov fits the bill in other ways as well. For instance, the crater is about as deep as scientists think the shallow northern ocean was at the time of impact. And part of Lomonosov's rim is missing, which is consistent with a mega-tsunami; the displaced water may have knocked this big chunk free as it raged.
While this evidence is suggestive, however, it does not yet rise to the level of a smoking gun, Rodriguez said.
"This crater is a candidate," he said. "I would not go so far as to say this is definitely the crater that produced the tsunami."
That tsunami, by the way, is probably the first of the two big floods that Rodriguez and his colleagues identified back in 2016. That earlier mega-tsunami featured both runoff and backwash flows, the latter of which are caused by water returning to the sea. Lomonosov seems to have been carved by both types of flows.
The second mega-tsunami caused runoff but not backwash, suggesting that Mars, and the ocean, may have been colder at the time. It's possible the northern ocean had a significant amount of ice cover when this other impactor came crashing down, he added.
Boosting the case for Mars life?
Lomonosov is interesting enough on solely geological grounds.
"This is possibly the first time that a potential marine crater associated with a tsunami has been investigated outside Earth," Rodriguez said.
And then there are the astrobiological implications. As noted above, Lomonosov's size suggests the northern ocean — a potentially habitable environment — persisted for a relatively long time. It's statistically unlikely, after all, that the Lomonosov impact occurred right after this liquid ocean formed.
And even if the ocean were largely frozen at the time, the impact would have created an environment favorable to life as we know it: The tremendous energy unleashed would have melted lots of ice and created a hydrothermal system at Lomonosov, Rodriguez said.
The crater is therefore a tantalizing target for future life-hunting missions. Robotic explorers probably aren't up to the task, however, because the Lomonosov area is covered by an ice layer about 33 feet (10 meters) thick, Rodriguez said.
But human explorers could probably drill down through the ice and access sediments on the crater floor. And these pioneers could use the abundant water ice for life support, providing an exploration twofer.
"That would be very interesting," Rodriguez said.
- How Tsunamis Work
- Water on Mars: Exploration & Evidence
- Photos: Ancient Mars Lake Could Have Supported Life
Mike Wall's book about the search for alien life, "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), is out now. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook. | 0.887308 | 3.860753 |
April 25, 2013 feature
New phase of water could dominate the interiors of Uranus and Neptune
(Phys.org) —While everyone is familiar with water in the liquid, ice, and gas phases, water can also exist in many other phases over a vast range of temperature and pressure conditions. One lesser known phase of water is the superionic phase, which is considered an "ice" but exists somewhere between a solid and a liquid: while the oxygen atoms occupy fixed lattice positions as in a solid, the hydrogen atoms migrate through the lattice as in a fluid. Until now, scientists have thought that there was only one phase of superionic ice, but scientists in a new study have discovered a second phase that is more stable than the original. The new phase of superionic ice could make up a large component of the interiors of giant icy planets such as Uranus and Neptune.
The scientists, Hugh F. Wilson (now at the Commonwealth Scientific and Industrial Research Organisation [CSIRO] in Australia), Michael L. Wong, and Burkhard Militzer at the University of California, Berkeley, have published a paper on the new phase of superionic ice in a recent issue of Physical Review Letters.
"Superionic water is a fairly exotic sort of substance," Wilson told Phys.org. "The phases of water we're familiar with all consist of water molecules in various arrangements, but superionic water is a non-molecular form of ice, where hydrogen atoms are shared between oxygens. It's somewhere between a solid and a liquid—the hydrogen atoms move around freely like in a liquid, while the oxygens stay rigidly fixed in place. It would probably flow more like a liquid, though, since the planes of oxygen atoms can slide quite freely against one another, lubricated by the hydrogens."
The original phase of superionic ice, called the body centered cubic (bcc) phase, was first predicted with ab initio computer simulations in 1999 by Carlo Cavazzoni, et al. Scientists predict that the bcc phase exists at pressures in excess of 0.5 Mbar (500,000 times greater than atmospheric pressure) and temperatures of a few thousand Kelvin. The bcc phase derives its name from the fact that the oxygen atoms occupy body centered cubic lattice sites. Hints of the bcc phase's instability have been previously observed, but the new study shows for the first time that the bcc phase is less stable than the new phase where the oxygen atoms occupy sites on a face centered cubic (fcc) lattice.
The scientists predict that the fcc phase exists at pressures in excess of 1.0 Mbar, even higher than the pressure for the bcc phase. The scientists' ab initio molecular dynamics simulations also show that the fcc phase has a higher density and lower hydrogen mobility than the bcc phase. That is, the hydrogen atoms in the fcc structure move less frequently to nearby voids between the oxygen atoms, while in the bcc structure, they migrate more freely between different sites. This difference affects the water's thermal and electrical conductivity. In addition, the simulations show that a phase transition between the bcc and fcc phases may exist at pressures of 1.0 ± 0.5 Mbar.
Although superionic ice doesn't exist under normal conditions on Earth, the high pressures and temperatures where it is thought to exist are very similar to the predicted conditions in the interiors of Uranus and Neptune.
"Uranus and Neptune are called ice giants because their interiors consist primarily of water, along with ammonia and methane," Wilson said. "Since the pressure and temperature conditions of the predicted new phase just happen to line up with the pressure and temperature conditions of the interiors of these planets, our new fcc superionic phase may very well be the single most prevalent component of these planets."
The researchers predict that understanding superionic ice—particularly the stable fcc phase—will offer insight into these ice giants.
"Uranus and Neptune remain very poorly understood at this stage, and their interiors are deeply mysterious," Wilson said. "The observations we have are very limited—every other planet in the solar system we've visited multiple times, but Uranus and Neptune we've just done brief flybys with Voyager 2. What we do know is that they have bizarre non-axisymmetric non-dipolar magnetic fields, totally unlike any other planet in our solar system. We also know that they're extremely similar in mass, density and composition, yet somehow fundamentally different, because Neptune has a significant internal heat source and Uranus hardly emits any heat at all."
It's possible that the predicted bcc-to-fcc phase transition may explain the planets' unusual magnetic fields, although more research is needed in this area.
"Our results imply that Uranus's and Neptune's interiors are a bit denser and have an electrical conductivity that is slightly reduced compared to previous models," Militzer added.
Understanding Uranus and Neptune's interiors could have implications far beyond our solar system, as well.
"One thing we're learning from the Kepler mission is that Uranus-like or Neptune-like exoplanets are extremely common," Wilson said. "They appear to be more common than Jupiter-like gas giants. So understanding our local ice giants is important, because they're an archetypal example for a huge class of planets out there in the universe."
In the future, the researchers plan to investigate the possible existence of a third superionic phase, as well as attempt to detect the predicted transition between the bcc and fcc phases.
"Shock wave experiments combined with X-ray diffraction techniques will enable one to detect the predicted bcc-to-fcc transition," Militzer said. "Shock waves allow one to reach megabar pressure and heat the sample to thousands of Kelvin at the same time. X-ray diffraction measurements allow one to determine whether the oxygen atoms reside on bcc or fcc positions. This leads to an obvious change in the X-ray diffraction pattern. Shock waves and X-ray diffraction have rarely been combined so far, but Dr. Jon Eggert at Lawrence Livermore National Laboratory is in the process of preparing such experiments."
Copyright 2013 Phys.org
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of Phys.org. | 0.849185 | 3.889255 |
Study corroborates the influence of planetary tidal forces on solar activity
One of the big questions in solar physics is why the sun's activity follows a regular cycle of 11 years. Researchers from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), an independent German research institute, now present new findings, indicating that the tidal forces of Venus, Earth and Jupiter influence the solar magnetic field, thus governing the solar cycle. The team of researchers present their findings in the journal Solar Physics.
In principle, it is not unusual for the magnetic activity of a star like the sun to undergo cyclic oscillation. And yet past models have been unable to adequately explain the very regular cycle of the sun. The HZDR research team has now succeeded in demonstrating that the planetary tidal forces on the sun act like an outer clock, and are the decisive factor behind its steady rhythm. To accomplish this result, the scientists systematically compared historical observations of solar activity from the last thousand years with planetary constellations, statistically proving that the two phenomena are linked. "There is an astonishingly high level of concordance: what we see is complete parallelism with the planets over the course of 90 cycles," said Frank Stefani, lead author of the study. "Everything points to a clocked process."
As with the gravitational pull of the Moon causing tides on Earth, planets are able to displace the hot plasma on the sun's surface. Tidal forces are strongest when there is maximum Venus-Earth-Jupiter alignment; a constellation that occurs every 11.07 years. But the effect is too weak to significantly perturb the flow in the solar interior, which is why the temporal coincidence was long neglected. However, the HZDR researchers then found evidence of a potential indirect mechanism that may be able to influence the solar magnetic field via tidal forces: oscillations in the Tayler instability, a physical effect that, from a certain current, can change the behavior of a conductive liquid or of a plasma. Building on this concept, the scientists developed their first model in 2016; they have since advanced this model in their new study to present a more realistic scenario.
Small trigger with a major impact: tides utilize instability
In the hot plasma of the sun, the Tayler instability perturbs the flux and the magnetic field, itself reacting very sensitively to tiny forces. A small thrust of energy is enough for the perturbations to oscillate between right-handed and left-handed helicity (the projection of the spin onto the direction of momentum). The momentum required for this may be induced by planetary tidal forces every eleven years—ultimately also setting the rhythm at which the magnetic field reverses the polarity of the sun.
"When I first read about ideas linking the solar dynamo to planets, I was very skeptical," Stefani recalled. "But when we discovered the current-driven Tayler instability undergoing helicity oscillations in our computer simulations, I asked myself: What would happen if the plasma was impacted on by a small, tidal-like perturbation? The result was phenomenal. The oscillation was really excited and became synchronized with the timing of the external perturbation."
Solar dynamo with an added touch
In the standard scenario of a dynamo, the rotation of the sun and the complex motion of the solar plasma create a cyclically changing magnetic field. Two effects interact here: the plasma rotates more quickly at the sun's equator than at the poles. This leads to the omega effect: the magnetic field lines frozen in the plasma stretch around the sun and convert the magnetic field into a field aligned almost parallel to the sun's equator. The alpha effect describes a mechanism that twists magnetic field lines, forcing the magnetic field back into a north-south direction.
What exactly causes the alpha effect, however, is a subject of dispute. Stefani's model indicates that the Tayler instability is partly responsible for this. The researchers consider the most plausible scenario to be one in which a classic solar dynamo is combined with the modulations excited by the planets. "Then the sun would be a completely ordinary, older star whose dynamo cycle, however, is synchronized by the tides," summarized Stefani. "The great thing about our new model is that we are now easily able to explain effects that were previously difficult to model, such as 'false' helicities, as observed with sunspots, or the well-known double peak in the sun's activity curve."
Besides influencing the 11-year cycle, planetary tidal forces may also have other effects on the sun. For example, it is also conceivable that they change the stratification of the plasma in the transition region between the interior radiative zone and the outer convection zone of the sun (the tachocline) in such a way that the magnetic flux can be conducted more easily. Under those conditions, the magnitude of activity cycles could also be changed, as was once the case with the Maunder Minimum, when there was a strong decline in solar activity for a longer phase.
In the long term, a more precise model of the solar dynamo would help scientists to quantify climate-relevant processes such as space weather more effectively, and perhaps even to improve climate predictions one day. The new model calculations also mean that, besides tidal forces, potentially other, hitherto neglected mechanisms would have to be integrated into the solar dynamo theory, mechanisms with weak forces that can nevertheless—as researchers now know—have a major impact. To be able to investigate this fundamental question in the laboratory, too, the researchers are currently setting up a new liquid metal experiment at HZDR. | 0.805144 | 4.076966 |
Skywatchers can expect an exciting month of cosmic phenomena, starting with a meteor shower to mark a beautiful start to Cinco de Mayo. The Eta Aquarids meteor shower is expected to peak in the early hours of Tuesday, May 5.
With most people stuck inside, isolating due to thepandemic, May's celestial events present a much-needed opportunity to connect with nature.
What are the Eta Aquarids?
The Eta Aquarids meteor shower peaks each year during early May as Earth passes through the debris trail from Halley's Comet (1P/Halley). The Orionids meteor shower in October also originates from this comet.
The famous Halley's Comet is visible from Earth about every 76 years. It was last seen in 1986 and won't be visible again until 2061.
Each year, when Earth collides with the comet's orbit, vaporizing debris comes flying into our atmosphere at a whopping 148,000 miles per hour, according to NASA, making the meteors well known for their speed. Fast meteors tend to leave glowing dust "trains" behind them, producing magnificent "shooting stars."
Under normal conditions, the annual meteor shower typically produces about 30 meteors per hour. It's named for its radiant, or direction of origin, which appears to come from the constellation Aquarius.
The Eta Aquarids are one of the best meteor showers of the year for people in the Southern Hemisphere because Aquarius is higher up in the sky there. However, it is also visible in the northern hemisphere.
When and where to watch the Eta Aquarids
The shower is visible in both hemispheres, with the best viewing occurring just before dawn. Locating the radiant point is not necessary for viewing — all you need to do is look up.
Viewing in the Southern Hemisphere is preferable but not necessary. From the northern hemisphere, the shooting stars often appear as "earth grazers" — long meteors that appear to skim the surface of the Earth near the horizon.
To view any meteor shower, it is always advised to escape harsh city lights and find an open area. Lie flat on your back with your feet facing east and look up, allowing about 30 minutes in the dark for your eyes to adjust.
Be patient, and don't forget a blanket!
Unfortunately, the shower is peaking very close to a full moon, so only the brightest of shooting stars will be visible. On May 7, the "Super Flower Moon" arrives just in time for the spring flowers to bloom. It will be the fourth and final supermoon of 2020. | 0.829853 | 3.771042 |
Understanding the core tenets of the flat-Earth hypothesis
The Flat Earth theory has gained a surprising amount of traction in recent years, thanks largely to YouTube. What exactly do Flat Earthers believe?
In 1492, Columbus set sail for the New World based on the assumption that Earth was round. Why not? After all, according to historian Jeffrey Burton Russell, “no educated person in the history of Western Civilization from the third century B.C. onward believed that the Earth was flat."
But nearly 500 years later, an American man was planning a voyage based on the exact opposite assumption. Mike Hughes, a 61-year-old limo driver, was going to launch himself into space to prove that Earth is flat. Mechanical complications and the federal government shot that idea down, however. (For now at least.)
Hughes isn't alone in his theory. Thousands of people — from musicians to football players — believe Earth is flat, and that the world's elite are duping citizens around (across?) the globe with a “globularist" conspiracy.
How is that possible?
Many cultures in world history conceptualized the physical world in ways that didn't include a spherical Earth. The ancient Chinese believed Earth to be a flat square, and that only the heavens were spherical. In multiple Indian models of the physical world, Earth was comprised of four continents surrounding a mountain. And the ancient Norse peoples pictured Earth as a disc floating in the middle of a sea inhabited by a giant serpent.
These ideas, however, were first challenged as early as 2,500 years ago. In the 4th century BC, Aristotle provided some of the first evidence showing that Earth was round: ships disappear hull first when sailing over the horizon, Earth casts a round shadow on the moon during lunar eclipses, and different constellations are visible at different latitudes.
Aristotle's evidence would be corroborated and elaborated upon extensively over the following millennia. But it seems that nothing — not even GPS technology or manned space flights — can convince some people that Earth is round.
In the modern era, the Flat Earth movement started in 1956 with a young British man named Samuel Shenton. Inspired by an 1881 book titled Zetetic Astronomy: Earth Not a Globe, Shenton founded the Flat Earth Society. A year later the Soviets launched Sputnik 1., rendering the plausibility of his theory questionable, to say the least. Shenton died believing Earth was flat. The next leader, Charles K. Johnson, passed away in 2001, leaving the dwindling organization with just 3,500 members. Then the Internet breathed new life into this ancient worldview.
So what exactly do modern Flat Earthers believe? There isn't one exclusive Flat Earth model, but the Flat Earth Society's website provides a general outline on what seems to be the community's consensus.
The World Is Disc-Shaped
According to Flat Earthers, the world is a disc with edges beyond which no one knows what exists.
"The earth is surrounded on all sides by an ice wall that holds the oceans back. This ice wall is what explorers have named Antarctica," reads the Flat Earth Society's FAQ. "Beyond the ice wall is a topic of great interest to the Flat Earth Society. To our knowledge, no one has been very far past the ice wall and returned to tell of their journey. What we do know is that it encircles the earth and serves to hold in our oceans and helps protect us from whatever lies beyond."
Some believe an infinite plane lies beyond the wall. Some believe you'd fall into outer space if you crossed it, which seems to be a tough feat — estimates vary, but the average proposed height of the wall seems to be something like 150 feet.
The Moon and the Sun are the Same Size
Flat Earthers believe the moon and the sun are the same size — a relatively tiny 32 miles in diameter — and that they orbit around the North Pole.
Gravity Doesn't Exist
Our understanding of gravity largely depends on Earth being a spherical object — that explains why objects maintain essentially the same weight across the globe. But Flat Earthers disagree: "Objects simply fall," reads the society's website. Flat Earthers have a few theories as to why objects fall, but they seem pretty confident that the common conception of gravity isn't the ticket: "What is certain is sphere earth gravity is not tenable in any way shape or form."
The Moon Landing Was Faked and Astronauts Are Lying
The U.S. was so caught up in the Space Race, Flat Earthers claim, that it faked the moon landing and only later discovered that Earth was indeed flat. The government then decided to perpetuate this lie, for a multitude of reasons. As for the astronauts in the space shuttles?
"Most Flat Earthers think Astronauts have been bribed or coerced into their testimonies," the Flat Earth Society's website reads. "Some believe they have been fooled or are mistaken."
Easy Ways To Prove Earth Is Round
Want to find out for yourself that Earth is round without launching yourself into space on a homemade rocket? One of the coolest and cheapest ways is to attach a camera onto a high-altitude balloon and let it rise until the curvature of the planet is visible to the naked eye.
You can also observe the constellations from different parts of the world. You'll soon notice that different stars are visible from different vantage points, as Aristotle pointed out in the 4th century BC. This implies that Earth is round — that or all of the stars in the universe are orbiting around Earth at a fixed speed.
If all else fails, take a note from Aristotle and go to the harbor — you'll notice that ships disappear hull first.
To create wiser adults, add empathy to the school curriculum.
- Stories are at the heart of learning, writes Cleary Vaughan-Lee, Executive Director for the Global Oneness Project. They have always challenged us to think beyond ourselves, expanding our experience and revealing deep truths.
- Vaughan-Lee explains 6 ways that storytelling can foster empathy and deliver powerful learning experiences.
- Global Oneness Project is a free library of stories—containing short documentaries, photo essays, and essays—that each contain a companion lesson plan and learning activities for students so they can expand their experience of the world.
Philosophers like to present their works as if everything before it was wrong. Sometimes, they even say they have ended the need for more philosophy. So, what happens when somebody realizes they were mistaken?
Sometimes philosophers are wrong and admitting that you could be wrong is a big part of being a real philosopher. While most philosophers make minor adjustments to their arguments to correct for mistakes, others make large shifts in their thinking. Here, we have four philosophers who went back on what they said earlier in often radical ways.
Numerous U.S. Presidents invoked the Insurrection Act to to quell race and labor riots.
- U.S. Presidents have invoked the Insurrection Act on numerous occasions.
- The controversial law gives the President some power to bring in troops to police the American people.
- The Act has been used mainly to restore order following race and labor riots.
It looks like a busy hurricane season ahead. Probably.
- Before the hurricane season even started in 2020, Arthur and Bertha had already blown through, and Cristobal may be brewing right now.
- Weather forecasters see signs of a rough season ahead, with just a couple of reasons why maybe not.
- Where's an El Niño when you need one?
Welcome to Hurricane Season 2020. 2020, of course, scoffs at this calendric event much as it has everything else that's normal — meteorologists have already used up the year's A and B storm names before we even got here. And while early storms don't necessarily mean a bruising season ahead, forecasters expect an active season this year. Maybe storms will blow away the murder hornets and 13-year locusts we had planned.
NOAA expects a busy season
According to NOAA's Climate Prediction Center, an agency of the National Weather Service, there's a 60 percent chance that we're embarking upon a season with more storms than normal. There does, however, remain a 30 percent it'll be normal. Better than usual? Unlikely: Just a 10 percent chance.
Where a normal hurricane season has an average of 12 named storms, 6 of which become hurricanes and 3 of which are major hurricanes, the Climate Prediction Center reckons we're on track for 13 to 29 storms, 6 to 10 of which will become hurricanes, and 3 to 6 of these will be category 3, 4, or 5, packing winds of 111 mph or higher.
What has forecasters concerned are two factors in particular.
This year's El Niño ("Little Boy") looks to be more of a La Niña ("Little Girl"). The two conditions are part of what's called the El Niño-Southern Oscillation (ENSO) cycle, which describes temperature fluctuations between the ocean and atmosphere in the east-central Equatorial Pacific. With an El Niño, waters in the Pacific are unusually warm, whereas a La Niña means unusually cool waters. NOAA says that an El Niño can suppress hurricane formation in the Atlantic, and this year that mitigating effect is unlikely to be present.
Second, current conditions in the Atlantic and Caribbean suggest a fertile hurricane environment:
- The ocean there is warmer than usual.
- There's reduced vertical wind shear.
- Atlantic tropical trade winds are weak.
- There have been strong West African monsoons this year.
Here's NOAA's video laying out their forecast:
ArsTechnica spoke to hurricane scientist Phil Klotzbach, who agrees generally with NOAA, saying, "All in all, signs are certainly pointing towards an active season." Still, he notes a couple of signals that contradict that worrying outlook.
First off, Klotzbach notes that the surest sign of a rough hurricane season is when its earliest storms form in the deep tropics south of 25°N and east of the Lesser Antilles. "When you get storm formations here prior to June 1, it's typically a harbinger of an extremely active season." Fortunately, this year's hurricanes Arthur and Bertha, as well as the maybe-imminent Cristobal, formed outside this region. So there's that.
Second, Klotzbach notes that the correlation between early storm activity and a season's number of storms and intensities, is actually slightly negative. So while statistical connections aren't strongly predictive, there's at least some reason to think these early storms may augur an easy season ahead.
Image source: NOAA
Batten down the hatches early
If 2020's taught us anything, it's how to juggle multiple crises at once, and layering an active hurricane season on top of SARS-CoV-2 — not to mention everything else — poses a special challenge. Warns Treasury Secretary Wilbur Ross, "As Americans focus their attention on a safe and healthy reopening of our country, it remains critically important that we also remember to make the necessary preparations for the upcoming hurricane season." If, as many medical experts expect, we're forced back into quarantine by additional coronavirus waves, the oceanic waves slamming against our shores will best be met by storm preparations put in place in a less last-minute fashion than usual.
Ross adds, "Just as in years past, NOAA experts will stay ahead of developing hurricanes and tropical storms and provide the forecasts and warnings we depend on to stay safe."
Let's hope this, at least, can be counted on in this crazy year.
Got any embarrassing old posts collecting dust on your profile? Facebook wants to help you delete them. | 0.871096 | 3.251044 |
W.Nawrot "The Hafele and Keating Paradox" - Phys. Essays 17, 518 (2004)
WThe results of the Hafele and Keating experiment prove that Earth does not rotate around the Sun.
W.Nawrot "Critical Reflections on the Hafele and Keating Experiment" - Proc. of Conf. "Mathematics, Physics and Philosophy in the Interpretations of Relativity Theory" Budapest, 7-9 Sept. 2007.
In 1971 Hafele and Keating performed their famous experiment which confirmed the time dilation predicted by SRT by use of macroscopic clocks. As it had already been shown , the continuation of reasoning applied by Hafele and Keating leads to the absurd conclusion that the Earth is not rotating around the Sun. Hafele and Keating derived a proper formula starting from false reasoning and this is the origin of the paradox. They tried to derive the formula from SRT, while the proper derivation can only be obtained from GRT . There were also serious doubts concerning the experimental part of their work [4,5], but it does not matter now because today the GPS system confirms what H&K wanted to prove. Finally, H&K wanted to confirm SRT but their experiment confirmed, in fact, the GRT. If we take a closer look at other experiments confirming SRT, we will come to the conclusion that all the experiments in fact confirm GRT similarly to the H&K experiment, because in order to compare times in two reference frames we have to disturb motion of one of the frames and this brings the problem to problems described by GRT. The pure inertial motion makes observation from two observed each other frames fully symmetrical, and we are not able to define in which of the frames the time flies slower. In this case we can draw the conclusion that the slowing of time in pure inertial motion can be only an observational effect. Only the change of speed of one of the participants transforms the observed time dilation into the real one. Therefore we can ask the questions – are there any serious experimental evidences confirming SRT? And - if in order to register the shortening of time the change of speed is necessary – can we assume, as it is done in SRT, that time slows down as a function of velocity.? Maybe the slowing of the time is rather a function of the change in velocity than the velocity itself?
A new concept of four dimensional reality is presented. The fourth dimension of the reality is now described with a dimension different from the time of the observer. Consequently, the Euclidean model of reality is obtained, description of phenomena is simplified in relation to the four-dimensional Lorentzian space-time and the singularities taking place in the description of the reality become now an effect of performing the observation and are not the property of reality any more. The new model also predicts certain new experimental effects which can be a reliable test for the new model.
This paper presents the new concept of time - the SUPERTIME. The SUPERTIME is the time identical for all bodies, independently of their relative motion. The SUPERTIME, together with the earlier FER model (Four-dimensional Euclidean Reality), justifies in a simple way the wave structure of matter and allows to introduce the new way of finding functions which describe the particles as waves. The new approach also greatly extends the class of these functions.
W.Nawrot "Four Dimensional Euclidean Reality - The basic properties of the model" Proc. International Scientific Congress "Fundamental Problems of Natural Science and Engineering" Saint-Petersburg, Russia 2008
Recently, more and more papers have been published concerning the alternative for Minkowski space - a Euclidean space model, in which time and spatial dimensions are identical [1-12]. The main idea of the Four Dimensional Euclidean Reality (FER) is the assumption that the reality is constructed of different dimensions than the observed space and time dimensions. The observed space and time dimensions are only certain projections of the "true" Euclidean dimensions. Such an assumption allows for the construction of the model of Euclidean reality from 4 identical dimensions, none of which is initially specified as being a time- or space dimension. It is only the choice of the pair: observer - the observed body, which determines which directions in FER are perceived as the spatial dimensions, and which as the time dimension. According to the FER model, the "real" reality is Euclidean, and while observing bodies in this reality we get the impression that the reality is actually Lorentzian. As a result we obtain several promising conclusions, i.e. the speed of E-M waves and the speed limit for mass bodies are described with two totally different mechanisms, which easily justifies the constancy of the speed of light. The singularities present in SRT are now only an effect of observation and not the real physical limitations of physical phenomena. Hence, the body can be accelerated to the velocity observed as the speed of light, but we will not be able to register this process. The new definition of time enables us to describe a sequence of events from the point of view of the body moving with the speed of light. The particle described with a wave function, in space-time, is described in FER as an ordinary wave, etc. The theory predicts new physical phenomena which can serve as experimental tests for the new model.
W.Nawrot "Euclidean Reality Theory - Spectacular Conclusions and New Problems" - Proc. International Scientific Congress "Fundamental Problems of Natural Science and Engineering" Saint-Petersburg, Russia 2008
The model of Euclidean space, in which all four dimensions are identical, and the time- and spatial dimensions we observe, are only certain directions in FER (Four-dimensional Euclidean Reality), depending on the choice of the observer and the observed body [1 3], allows for the derivation of many spectacular conclusions [4,5]. Such conclusions may suggest that our ideas about the construction of the reality differ greatly from what actually surrounds us. The FER model predicts the new method of the composition of velocities, which does not allow for exceeding the speed of light, but allows for accelerating the body to the velocity observed as the speed of light, using finite energy. The new method of the composition of velocities results from a different transformation of coordinates than the Lorentz one. Such transformation anticipates the time dilation analogically to the Relativity Theory, but does not anticipate the Lorentzian shortening of spatial dimensions in case of macroscopic observations. When observers are moving along linear trajectories which have a common beginning, and they are observing each other, they are observing the increasing of mutual velocities proportionally to the distance between the observers. This phenomena allows for describing the increase of the velocity of the galaxies in a very simple way. The increase of velocities of galaxies is now a seeming effect, and is not the result of any real acceleration resulting from enigmatic repulsion interactions. The increase of the velocity, the Hubble's constant, as well as the definition of the Hubble's constant as the reverse of the age of the Universe, are obtained here from a very simple formula consisting of just a few symbols. According to the FER model we are able to observe only half of the real Universe.
In the Relativity Theory equations are written in a form that conserves the value of the space-time interval during the transition from one observer's system to another. The Lorentz Transformation is a generally known solution of the space-time interval equation so that the equations of the RT are invariant in relation to this transformation. According to the Four dimensional Euclidean Reality Model (FER) there is another solution of this equation and this solution allows to draw some other conclusions than the conclusions obtained on the grounds of the Lorentz Transformation. Derivation of the Lorentz Transformation according to the FER model is still possible but the derivation can be performed only at the cost of breaking certain laws. Therefore, although the Lorentz Transformation is mathematically correct, it is not correct from the physical point of view.
Recent papers show that the space-time can be described with the Four-dimensional Euclidean Reality (FER) in which all dimensions have identical properties. According to the new model, the dimensions of time and space which we are able to observe are not the dimensions that create the reality. They are only certain directions in FER, which are interpreted by us as the dimensions of space. The directions interpreted by us as the time- and space dimensions depend on the choice of an observed body and an observer, that is to say the directions are different for every pair: the observer and the observed body. According to the new model of the reality, observers that move in FER along trajectories having a common origin - as it takes place in case of the galaxies - observe other bodies/observers as moving with the velocity proportional to the distance from the observer. The velocity proportional to the distance is now the result of observation only and has nothing to do with any acceleration.
Original version available at http://www.phil-inst.hu/~szekely/PIRT_BP_2/papers/NAWROT_09_FT.doc
In 1971 Hafele and Keating performed their famous experiment which confirmed the time dilation predicted by SRT by use of macroscopic clocks. As it had already been shown , the continuation of reasoning applied by Hafele and Keating leads to the absurd conclusion that the Earth is not rotating around the Sun. Hafele and Keating derived a proper formula starting from false reasoning and this is the origin of the paradox. They tried to derive the formula from SRT, while the proper derivation can only be obtained from GRT . There were also serious doubts concerning the experimental part of their work [4,5], but it does not matter now because today the GPS system confirms what H&K wanted to prove. Finally, H&K wanted to confirm SRT but their experiment confirmed, in fact, the GRT. If we take a closer look at other experiments confirming SRT, we will come to the conclusion that all the experiments in fact confirm GRT similarly to the H&K experiment, because in order to compare times in two reference frames we have to disturb motion of one of the frames and this brings the problem to problems described by GRT. The pure inertial motion makes observation from two observed each other frames fully symmetrical, and we are not able to define in which of the frames the time flies slower. In this case we can draw the conclusion that the slowing of time in pure inertial motion can be only an observational effect. Only the change of speed of one of the participants transforms the observed time dilation into the real one. Therefore we can ask the questions - are there any serious experimental evidences confirming SRT? And - if in order to register the shortening of time the change of speed is necessary - can we assume, as it is done in SRT, that time slows down as a function of velocity.? Maybe the slowing of the time is rather a function of the change in velocity than the velocity itself?
W. Nawrot, "Euclidean model of the spacetime - is the reality exactly as we can observe it?" - Mathematics, Physics and Philosophy in the Interpretations of Relativity Theory Budapest, 4 - 6 September 2009.
Original version available at http://www.phil-inst.hu/~szekely/PIRT_Budapest/
The new model of Four dimensional Euclidean Reality (FER), which recently, more and more often, appears in publications, can significantly change the manner in which we interpret the reality surrounding us. According to the approach presented here, the reality we are able to observe differs from the "true" reality. Living, in fact, in the Four dimensional Euclidean Reality, we get an impression that we are living in the four dimensional Lorentzian reality. The impression is a consequence of the seemingly obvious assumption that the space and time distances that we are able to observe are the actual dimensions creating the reality. However, an assumption saying that the distances we measure during the observation of surrounding objects are describing the true dimension of the reality can be similar to the assumption, accepted through centuries, saying that the motions of heavenly bodies, observed by us on the firmament from the Earth, are the motions that the bodies are actually performing. Perhaps it is just the improper model of the reality that is the source of all the troubles, misunderstandings and complications of the models based on the Relativity Theory, which, although correctly describing a wide class of phenomena, did not lead to solutions which at the beginning of the XX-th century seemed to be just a step away, i.e. unification of the electromagnetic and gravitational interactions . It should be noticed that a few hundred years ago, the geocentric theory, though complicated, was describing motions of heavenly bodies in a more accurate way than the later heliocentric theory however, the progress of science and, for instance, planning cosmic travels, would not be possible with the geocentric model. The new, Euclidean model of reality allows us to answer the questions asked already in my other paper concerning SRT: is the slowing of time, in a frame of body in motion, actual slowing or it is only a result of mutual observation, and why registering of the shortening of the time requires the change of velocity of the observed body. An additional argument for the necessity of more serious treatment of new models, alternative to the hitherto ones, would be the recently observed anomalies of motions of satellites which are impossible to explain with the help of the Relativity Theory.
W. Nawrot, The New Concept of Ether" Submitted to Galilean Electrodynamics Feb. 2012
The new model of the Euclidean Reality FER (Four dimensional Euclidean Reality) introduces the new concept of the motion of bodies, which allows for returning to the idea of the ether. In the FER, the motion of bodies in relation to the ether and the relative motion of the bodies are two separate phenomena. The FER Model allows for describing a body as a wave moving with constant velocity relative to the ether, along a certain trajectory. The relative velocity of bodies which we are able to observe is not connected with the motion of the bodies-waves relative to the ether but it is only the measure of an angle between the trajectories that the bodies-waves are moving along. The velocity described in such a way is not connected with the velocity of the bodies-waves relative to the ether. Therefore, the experimental investigations examining the relative motion of bodies (measuring an angle between the trajectories) are not able to detect the motion of bodies-waves relative to the ether.
W. Nawrot, "New philosophy of Aether in Euclidean Reality model and interpretation of indications of Sagnac and MM interferometers" Proceedings of the 20 NPA Minneapolis, MN USA 2013
According to the new model of Four dimensional Euclidean Reality, motion of bodies in relation to Aether and relative motion of bodies are two separate phenomena, therefore there is no necessity for introducing the idea of "entrained Aether". According to this model, the MM and Sagnac interferometers are not able to detect any motion in relation to Aether, however the rule of propagation of light, introduced by the new model, explains the difference between indications of these two interferometers.
W. Nawrot, "Explanation of twin paradox according to the Euclidean Reality Model" Proceedings of the 20 NPA Minneapolis, MN USA 2013
The Four dimensional Euclidean Reality model clearly explains why during the uniform, rectilinear motion, the time dilation effect is symmetrical for both twins, and why and when the time dilation is eventually measured in a system of one of the travelling twin.
W. Nawrot, "The Hafele-Keating paradox - Serious problems of the special theory of relativity (SRT)?" Phys.Ess. 27, 4, pp 598-600 (2014)
Conclusions from the Hafele–Keating paradox indicate that the hitherto experiments confirming predictions of special theory of relativity, concerning the phenomena of time dilation in moving frames, did not prove unequivocally whether the time dilation is only the result of the velocity itself or of the change of the velocities of bodies
W. Nawrot, "Proposal of experiment disproving the Theory of Relativity" Accepted for publication in the Galilean Electrodynamics, 2015
This paper presents an idea for an experiment which should give results contradicting the predictions of the Theory of Relativity. The experiment consists of using two low energy (below 0,4Ge.V) colliding beams, the relative velocity of which, according to the model of Euclidean Reality, should be equal to the speed of light. The possibility of obtaining the relative velocity of objects equal to the speed of light with the help of finite energies results from the new transformation of velocities published independently in two papers in Galilean Electrodynamics. According to the article presented here, during the measuring of pp total cross sections in a collider, for the relative speed of colliding protons equal (and almost equal) to the speed of light, in a very strict and very narrow range of energies, a sharp spike should be visible on the pp cross section diagram. Existence of this spike will prove that the hitherto rule of transformation of velocities and consequently the Lorentz transformations are wrong. Moreover it will prove that the idea of deformation of dimensions as a function of speed is wrong as well.
Witold Nawrot "Alternative Idea of Relativity" International Journal of Theoretical and Mathematical Physics, p-ISSN: 2167-6844 e-ISSN: 2167-6852, 2017; 7(5): 95-112
A new, alternative idea of the reality is presented. Instead of four-dimensional space-time with the signature defined with the metric tensor and dimensions deformed as a function of body’s motion, a four-dimensional absolute Euclidean space is proposed whose dimensions do not have a predetermined meaning of time or space. The dimensions of time and space are not the dimensions creating the reality any more, but they are only certain directions in Euclidean four-dimensional space. And these directions depend on the pair of observer – observed body. While observing bodies moving with various velocities we interpret various directions in the Euclidean reality as the space-time dimensions and that’s, in general, the difference of directions interpreted by us as the space-time dimensions and not the deformation of dimensions, becomes responsible for relativistic phenomena. The new approach significantly simplifies the description of reality – through the description in Euclidean space, it eliminates singularities and additionally answers many questions that the Theory of Relativity was not able to answer to for almost 100 years. | 0.837193 | 3.565429 |
“15 Million Degrees: Journey to the centre of the Sun”
Public lecture by Prof. Lucie Green, University College London
110 times wider than Earth; 15 million degrees at its core; an atmosphere so huge that Earth is actually within it: come and meet the star of our solar system.
Light takes eight minutes to reach Earth from the surface of the Sun. But its journey within the Sun takes hundreds of thousands of years. What is going on in there? What are light and heat? How does the Sun produce them and how on earth did scientists discover this? Join Lucie Green for an enlightening talk, taking you from inside the Sun to its surface and to Earth, to discover how the Sun works, how a solar storm can threaten the modern technology that society relies on and more of the latest research in solar physics.
Lucie Green is a British science communicator and solar researcher. Since 2005 Green has been a Royal Society University Research Fellow at Mullard Space Science Laboratory of the University College London.
“Venus – an Exoplanet next door”
Public lecture by Dr Sanjay S. Limaye, University of Wisconsin, Madison, USA
In 1761 Lomonosov observed the transit of Venus as it crossed the Sun’s disc, making the first observed discovery about another planet – that our nearest solar system neighbor had an atmosphere. This technique has led to the discovery of thousands of planets around other stars. Nearly two hundred years later in 1962, the Mariner 2 spacecraft successfully flew past Venus and made the major discovery that the planet’s surface was extremely hot. Since then Venus has been explored by atmospheric entry probes, landers, balloons and orbiters in addition to being observed by spacecraft on their way to other destinations. We have discovered that the cloud covered planet which takes longer to rotate about itself than to orbit the Sun is still shrouded in mystery. If we cannot understand our closest planetary neighbor, how can we really appreciate with confidence the mysteries of other exoplanets beyond our own solar system?
Sanjay Limaye is a planetary scientist at the Space Science and Engineering Center at the University of Wisconsin-Madison.
“Space Weather – How the Sun’s activity influences Earth’s environment”
Public lecture by Dr Erwin Verwichte, University of Warwick
We all know that the light from the Sun is responsible for the right conditions on Earth for life to thrive. But as humanity started taming electricity and entered the space era, we realised that the Sun influences the Earth environment in many more ways. In this lecture I will explore, using the latest imagery from satellite missions, how the activity of the Sun causes disturbances at Earth that are responsible for the northern lights but also for interruptions in communication, damaging satellites, and an increased risk for human space explorations.
Dr Erwin Verwichte is an Associate Professor in the Physics Department of the University of Warwick with more than 20 years experience in the research of dynamics in the atmosphere of the Sun. | 0.863034 | 3.512828 |
ESO’s Very Large Telescope (VLT) has observed the central part of the Milky Way with spectacular resolution and uncovered new details about the history of star birth in our galaxy. Thanks to the new observations, astronomers have found evidence for a dramatic event in the life of the Milky Way: a burst of star formation so intense that it resulted in over a hundred thousand supernova explosions.
“Our unprecedented survey of a large part of the Galactic center has given us detailed insights into the formation process of stars in this region of the Milky Way,” says Rainer Schödel from the Institute of Astrophysics of Andalusia in Granada, Spain, who led the observations. “Contrary to what had been accepted up to now, we found that the formation of stars has not been continuous,” adds Francisco Nogueras-Lara, who led two new studies of the Milky Way central region while at the same institute in Granada.
In the study, published December 16, 2019, in Nature Astronomy, the team found that about 80% of the stars in the Milky Way central region formed in the earliest years of our galaxy, between eight and 13.5 billion years ago. This initial period of star formation was followed by about six billion years during which very few stars were born. This was brought to an end by an intense burst of star formation around one billion years ago when, over a period of less than 100 million years, stars with a combined mass possibly as high as a few tens of million Suns formed in this central region.
“The conditions in the studied region during this burst of activity must have resembled those in ‘starburst’ galaxies, which form stars at rates of more than 100 solar masses per year,” says Nogueras-Lara, who is now based at the Max Planck Institute for Astronomy in Heidelberg, Germany. At present, the whole Milky Way is forming stars at a rate of about one or two solar masses per year.
“This burst of activity, which must have resulted in the explosion of more than a hundred thousand supernovae, was probably one of the most energetic events in the whole history of the Milky Way,” he adds. During a starburst, many massive stars are created; since they have shorter lifespans than lower-mass stars, they reach the end of their lives much faster, dying in violent supernova explosions.
This research was possible thanks to observations of the Galactic central region done with ESO’s HAWK-I instrument on the VLT in the Chilean Atacama Desert. This infrared-sensitive camera peered through the dust to give us a remarkably detailed image of the Milky Way’s central region, published in October in Astronomy & Astrophysics by Nogueras-Lara and a team of astronomers from Spain, the US, Japan, and Germany. The stunning image shows the galaxy’s densest region of stars, gas, and dust, which also hosts a supermassive black hole, with an angular resolution of 0.2 arcseconds. This means the level of detail picked up by HAWK-I is roughly equivalent to seeing a football (soccer ball) in Zurich from Munich, where ESO’s headquarters are located.
This image is the first release of the GALACTICNUCLEUS survey. This program relied on the large field of view and high angular resolution of HAWK-I on ESO’s VLT to produce a beautifully sharp image of the central region of our galaxy. The survey studied over three million stars, covering an area corresponding to more than 60 000 square light-years at the distance of the Galactic center (one light-year is about 9.5 trillion kilometers).
“GALACTICNUCLEUS: A high angular resolution JHKs imaging survey of the Galactic Centre: II. First data release of the catalogue and the most detailed CMDs of the GC” by F. Nogueras-Lara, R. Schödel, A. T. Gallego-Calvente, H. Dong, E. Gallego-Cano, B. Shahzamanian1, J. H. V. Girard, S. Nishiyama, F. Najarro and N. Neumayer, 15 October 2019, Astronomy & Astrophysics.
“Early formation and recent starburst activity in the nuclear disc of the Milky Way” by Francisco Nogueras-Lara, Rainer Schödel, Aurelia Teresa Gallego-Calvente, Eulalia Gallego-Cano, Banafsheh Shahzamanian, Hui Dong, Nadine Neumayer, Michael Hilker, Francisco Najarro, Shogo Nishiyama, Anja Feldmeier-Krause, Julien H. V. Girard and Santi Cassisi, 16 December 2019, Nature Astronomy.
The team of the Astronomy & Astrophysics paper is composed of F. Nogueras-Lara (Instituto de Astrofísica de Andalucía, Granada, Spain [IAA-CSIC]), R. Schödel (IAA-CSIC), A. T. Gallego-Calvente (IAA-CSIC), H. Dong (IAA-CSIC), E. Gallego-Cano (IAA and Centro Astronómico Hispano-Alemán, Almería, Spain), B. Shahzamanian (IAA-CSIC), J. H. V. Girard (Space Telescope Science Institute, Baltimore, USA), S. Nishiyama (Miyagi University of Education, Sendai, Japan), F. Najarro (Departamento de Astrofísica, Centro de Astrobiología CAB (CSIC-INTA), Torrejón de Ardoz, Spain), N. Neumayer (Max Planck Institute for Astronomy, Heidelberg, Germany).
The team of the Nature Astronomy paper is composed of F. Nogueras-Lara (Instituto de Astrofísica de Andalucía, Granada, Spain [IAA-CSIC]), R. Schödel (IAA-CSIC), A. T. Gallego-Calvente (IAA-CSIC), E. Gallego-Cano (IAA-CSIC), B. Shahzamanian (IAA-CSIC), H. Dong (IAA-CSIC), N. Neumayer (Max Planck Institute for Astronomy, Heidelberg, Germany), M. Hilker (European Southern Observatory, Garching bei München, Germany), F. Najarro (Departamento de Astrofísica, Centro de Astrobiología, Torrejón de Ardoz, Spain), S. Nishiyama (Miyagi University of Education, Sendai, Japan), A. Feldmeier-Krause (The Department of Astronomy and Astrophysics. The University of Chicago, Chicago, US), J. H. V. Girard (Space Telescope Science Institute, Baltimore, USA) and S. Cassisi (INAF-Astronomical Observatory of Abruzzo, Teramo, Italy).
ESO is the foremost intergovernmental astronomy organization in Europe and the world’s most productive ground-based astronomical observatory by far. It has 16 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland, and the United Kingdom, along with the host state of Chile and with Australia as a Strategic Partner. ESO carries out an ambitious program focused on the design, construction, and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organizing cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. ESO is also a major partner in two facilities on Chajnantor, APEX, and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-meter Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky.” | 0.854476 | 3.935492 |
A white dwarf star, just imaged by a team at the University of Warwick, has a bright red ring circling it, created by the dead star’s oblitertion of space debris that orbits overly close. The rock ring circling the white dwarf star is composed of rock and dust particles. The new photo shows an asteroid destroyed by the star’s gravitational forces and sent in to an orbit around the star.
The work was compiled by a group of researchers in the university’s Astrophysics Dept. The leader of the research team stated:
The diameter of the gap inside of the rock ring is about half the size of the Sun.
The reddish glow is caused by ultraviolet light from within the star. Although scientists have been aware for some decades that these debris rings exist, this is the first time a group has been able to capture imagery of the ring type, giving scientists unprecedented access to the data.
The photograph of the rings is a composite of a number of images taken utilizing Doppler tomography.. Using this system, the scientists were able to capture certain aspects of the structure that would not have been captured using a single photo.
This photo is a glimpse of what our own solar system will look like in the distant future. | 0.925048 | 3.128156 |
It sounds like a vintage sci-fi movie: Karst Conquers the Ionosphere!
In the late Fifties, Cornell physicist and astronomer William Gordon, PhD ’53, wanted to study Earth’s upper atmosphere. A mountainous region of northwest Puerto Rico—with a topography of dramatically sloping valleys known as karst—offered a natural setting for a giant dish. And that gave Gordon an idea.
In 1960, construction began on what would become Arecibo Observatory—the world’s largest and most sensitive radio telescope, with a 305-meter-wide dish comprising nearly 39,000 aluminum panels. Although the dish is fixed to the ground, the instruments suspended above it can be reoriented, allowing the telescope to observe some 40 percent of the sky. “It was an enormous technical marvel,” says Joseph Burns, PhD ’66, a professor of theoretical and applied mechanics who specializes in planetary sciences. “Even the way it was put together—by modern standards, it was built in a split second.”
Fifty years ago this month—on November 1, 1963—Arecibo officially opened. In the intervening half-century, it has made countless contributions to science—from studies on the molten core and rotation rate of Mercury to Nobel Prize-winning work on binary pulsars that proved the theory of general relativity. The telescope has tracked asteroids that may threaten Earth and listened for extraterrestrial life as part of the SETI project; in 1974, it broadcast an interstellar greeting to a star cluster 25,000 light years away. “Arecibo has been incredibly important, because it’s the most sensitive radio telescope that’s existed,” says Martha Haynes, the Goldwin Smith Professor of Astronomy. “It’s also a really interesting telescope, because it doesn’t just do passive radio astronomy—detecting signals from pulsars, galaxies, and stars—it also does planetary radar mapping. You transmit a signal from Puerto Rico and bounce it off Saturn’s rings and it comes back; that’s pretty amazing. And it also studies the Earth’s ionosphere. So it’s a multidisciplinary facility—which means that the scientists have to interact and understand each others’ work. That has made it an exciting, dynamic place.”
Arecibo is a federal facility, and for most of its existence the National Science Foundation contracted with Cornell to administer it. But in 2011—a few years after the telescope survived a round of funding cuts and avoided being decommissioned—management was transferred to SRI International, a nonprofit research institute. The reasons, Burns says, are complicated—but the fact remains that the leadership of national labs is generally intended to migrate among institutions, and Cornell had Arecibo for nearly half a century. “It was a loss to Cornell for sentimental and loyalty reasons, but the bigger loss was to the observatory and the scientific community,” says Haynes, who’s now analyzing data from a seven-year study using the telescope to inventory gas-bearing galaxies. “People at Cornell have always been responsible for thinking of the next big thing for Arecibo. A lot of revolutionary things—instrumentation and technology, approaches to taking data—were developed by faculty and staff here. Because we’re not so closely tied anymore, that tight connection is gone.”
Arecibo is open to the public, and its visitor center has greeted about half the students in Puerto Rico—making it a vital symbol of scientific achievement and possibility in an economically disadvantaged region. But to get a good look at the dish, you don’t have to fly to San Juan. Just rent the movie version of Carl Sagan’s novel Contact, which was partially shot there. Or for a more fantastical take, screen the 1995 James Bond film GoldenEye. In it, the dish—hidden beneath a lake—serves as the villain’s lair. | 0.831543 | 3.788707 |
- Planets move around the sun in elliptic orbits. The sun is in one of the two foci of the orbit.
- A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.
- The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit.
Johannes Kepler found these laws, between 1609 and 1619.
Comparison to CopernicusEdit
- The planetary orbit is a circle
- The Sun at the center of the orbit
- The speed of the planet in the orbit is constant
The eccentricities of the orbits of those planets known to Copernicus and Kepler are small, so the rules above give good approximations of planetary motion; but Kepler's laws fit the observations better than Copernicus's.
Kepler's corrections are not at all obvious:
- The planetary orbit is not a circle, but an ellipse.
- The Sun is not at the center but at a focal point of the elliptical orbit.
- Neither the linear speed nor the angular speed of the planet in the orbit is constant, but the area speed is constant.
The eccentricity of the orbit of the Earth makes the time from the March equinox to the September equinox, around 186 days, unequal to the time from the September equinox to the March equinox, around 179 days. A diameter would cut the orbit into equal parts, but the plane through the sun parallel to the equator of the earth cuts the orbit into two parts with areas in a 186 to 179 ratio, so the eccentricity of the orbit of the Earth is approximately
which is close to the correct value (0.016710219) (see Earth's orbit). The calculation is correct when perihelion, the date the Earth is closest to the Sun, falls on a solstice. The current perihelion, near January 4, is fairly close to the solstice of December 21 | 0.823537 | 3.894747 |
Newborn stars may be starving their parent galaxy of the ingredients to produce more offspring.
The affected galaxy has a name that is rather hard to remember: SDSS J0905+57. Astronomers have just measured starlight from its fledgling stars. And they seem to be pushing out enough hydrogen to form billions more stars. The observations should help astronomers understand more about how and why star formation begins to shut down in a galaxy.
Details appear in a report published December 4 in Nature.
Stars form when gravity causes clouds of dust and gas to collapse into tight masses. Most of that gas is hydrogen. Hydrogen can be difficult to observe. So astronomers looked for it indirectly. They measured levels of a second gas — carbon monoxide. Why that gas? The proportion of carbon monoxide in a galaxy is usually closely related to how much hydrogen is present.
Using these data, the team concluded that huge quantities of hydrogen gas must be streaming out of the galaxy. That galaxy sits about 8 billion light-years away in the constellation Ursa Major (or the Great Bear).
This galaxy is churning out new stars roughly 100 times as fast as is our galaxy, the Milky Way.
Astronomer James Geach works at the University of Hertfordshire in England. He and his colleagues found that the intense light from all those newborn stars in SDSS J0905+57 provides enough energy to expel much of the surrounding hydrogen gas.
At the current rate of hydrogen loss, that galaxy could run out of stellar ingredients in just 10 million years. After that, it could become a galactic retirement home filled with aging stars.
Astronomers have debated whether starlight, stellar explosions or super-massive black holes force gas out of galaxies. All three probably have roles to play. However, the new observations show that light from newborn stars alone can be enough to do the job.
astronomy The area of science that deals with celestial objects, space and the physical universe as a whole. People who work in this field are called astronomers.
black hole A region of space having a gravitational field so intense that no matter nor radiation (including light) can escape.
carbon monoxide A toxic gas whose molecules include one carbon atom and one oxygen atom. (The “mono” in “monoxide” is a prefix from Greek that means “one”.) One common source: fossil-fuel burning.
constellation Patterns formed by prominent stars that lie close to each other in the night sky. Modern astronomers divide the sky into 88 constellations, 12 of which (known as the zodiac) lie along the sun’s path through the sky over the course of a year. Cancri, the original Greek name for the constellation Cancer, is one of those 12 zodiac constellations.
galaxy A massive group of stars bound together by gravity. Galaxies, which each typically include between 10 million and 100 trillion stars, also include clouds of gas, dust and the remnants of exploded stars.
gravity The force that attracts anything with mass, or bulk, toward any other thing with mass. The more mass that something has, the greater its gravity.
hydrogen The lightest element in the universe. As a gas, it is colorless, odorless and highly flammable. It’s an integral part of many fuels, fats and chemicals that make up living tissues.
light-year The distance light travels in a year, about 9.48 trillion kilometers (almost 6 trillion miles). To get some idea of this length, imagine a rope long enough to wrap around the Earth. It would be a little over 40,000 kilometers (24,900 miles) long. Lay it out straight. Now lay another 236 million more that are the same length, end-to-end, right after the first. The total distance they now span would equal one light-year.
mass A number that shows how much an object resists speeding up and slowing down — basically a measure of how much matter that object is made from. Or the term can refer to anything containing mass.
Milky Way The galaxy in which Earth’s solar system resides.
star Thebasic building block from which galaxies are made. Stars develop when gravity compacts clouds of gas. When they become dense enough to sustain nuclear-fusion reactions, stars will emit light and sometimes other forms of electromagnetic radiation. The sun is our closest star.
stellar An adjective that means of or relating to stars.
supernova (plural: supernovae or supernovas) A massive star that suddenly increases greatly in brightness because of a catastrophic explosion that ejects most of its mass. | 0.839589 | 3.924109 |
Yesterday I talked about the Fermi gamma ray telescope, and how it allowed us to make much more precise observations of gamma rays in the universe. Part of the purpose of the Fermi telescope is to observe gamma ray bursts, but its broader purpose is to make a sky survey of gamma ray sources in the universe. Already it has found something quite interesting.
The image above shows the plane of the Milky Way with x-rays indicated in blue and gamma rays indicated in purple. The x-ray regions had been observed earlier by the ROSAT satellite, but it took FGST (Fermi Gamma-ray Space Telescope) to observe the gamma rays. Neither the x-ray nor gamma ray sources are particularly bright. Instead they come from a diffuse region producing these rays.
What’s particularly striking about these “bubbles” is that that are quite large. The regions span 25,000 light years in either direction of the central region of our galaxy. It is so large that it spans more than half the sky. It is caused by a process known as inverse Compton scattering. Electrons moving at speeds near the speed of light collide with low energy (radio or infrared) photons, giving them a massive energy boost and making them gamma rays.
The large size of these bubbles means that they were caused by a large process. They also seem to have a clearly defined boundary. Given that they are caused by electrons moving at nearly the speed of light, and the fact that they extend about 25,000 light years out from galactic center, a likely cause would seem to be from jets emanating from the supermassive black hole in the center of our galaxy. Currently the black hole doesn’t seem to be producing jets, but the bubbles could be evidence of past activity.
Last year new evidence hinted at even more interesting effects. A study published in the Journal for Cosmology and Astroparticle Physics has proposed that some of the gamma rays in the bubbles could be produced by the decay of dark matter in the galaxy.1 The paper looks at the energy distribution of gamma rays near the galactic plane, and seems to find a spike of gamma rays at an energy of 130 GeV. Such a spike could be evidence of dark matter, but the research looked at such a narrow energy band that the data set consists of only 50 gamma ray photons. Even the author of the paper says this result should be considered very tentative.
Gamma ray astrophysics is still a relatively new field of study, but it is quickly providing us with new results and new mysteries to ponder.
Weniger, Christoph. “A tentative gamma-ray line from dark matter annihilation at the Fermi Large Area Telescope.” Journal of Cosmology and Astroparticle Physics 2012.08 (2012): 007. ↩︎ | 0.889167 | 4.145079 |
Nibiru Causing Venus To Brighten, says R.I.T. Astronomer
One need not be a professional stargazer to have noticed the unusually bright pinprick of light illuminating the heavens. Venus, the scorching, sulfurous planet discovered by Galileo in 1610, has been a nocturnal companion to anyone peering into the cosmos this winter. But why Venus has markedly brightened is a question that has allegedly baffled some of society’s brightest minds, including many prominent astronomers and astrophysicists. A Cornell-educated astronomer and Rochester Institute of Technology astronomy professor believes he has an explanation—Nibiru.
Dr. Richard Stephen Hathaway had first learned of the Nibiru system while attending an astronomy symposium in Perth. During the lectures, a colleague of his violated policy and began a power point presentation about Nibiru, hypothesizing that Nibiru’s lateral position, relative to the inner solar system, was responsible for increased surface temperatures within the dark star’s sphere of influence. That presenter had been dragged off the stage for embracing a taboo subject eschewed by mainstream academia.
But Dr. Hathaway had found merit in that hypothesis and clandestinely used his spare time to learn all he could about the dark star and its seven companion planets. Having studied the teachings of Zachharia Sitchen and famed naval astronomer Robert Sutton Harrington, Dr. Hathaway unearthed a correlation between the heating and the brightening of the inner planets.
“There is no doubt Nibiru is responsible,” Dr. Hathaway told our source. “Once Nibiru completed its first cycle around the dark side of the sun and achieved breakaway speed, Venus became much brighter. Several factors are responsible for this dramatic change. First, although the brown dwarf star at the center of the Nibiru system casts very little visible light of its own, it does reflect and refract light directed at it—shedding light at 1600 angstroms. In essence, it acts like a prism, largely because of the dense clouds of red iron dust. Light from the sun strikes Nibiru, and is reflected at Venus, causing an increase in luminosity.”
He says he has observed Venus every night this winter, weather and astronomical conditions permitting, and has discovered an alarming truth: over a period of 120 days, Venus has increased in brightness by a magnitude of fifty. This marked change, he said, should have triggered a worldwide response to the impending Nibiru apocalypse.
“Imagine if Proxima Centuri suddenly exploded in space,” Dr. Hathaway said, “its visibility would mirror how Venus now appears in the sky. This is unprecedented. People deserve to know. Despite Trump’s best efforts, dark forces are still working behind the scenes to conceal the Nibiru truths. Soon, very soon, Venus will be as bright as a full moon in a cloudless sky.”
Nibiru’s auxiliary posterior position relative to its elongated elliptical orbit, he added, has created an effect he calls the Carbolic Point. In non-technical language, Nibiru’s dynamic interaction with our own sun is generating enough electricity to increase surface temperatures on all planets in the solar system, including Earth, resulting in geothermic instability.
“This conductive heating is another reason Venus has brightened,” Dr. Hathaway explained. “Think of a fire—the hotter it gets, the brighter it gets. Same principle.”
According to Dr. Hathaway, Nibiru’s transit through the inner solar system will likely cause Earth to brighten in July or August this year; moreover, he predicts a 3c increase in global surface temperatures, an event likely to herald the end of the industrial revolution and plunge society back to the Bronze Age.
Thanks to Mike at: http://www.someonesbones.com | 0.841384 | 3.850836 |
Sometimes science imitates art. The Greeks myths told how Enceladus, a Giant who was buried beneath Mount Etna, caused earthquakes and volcanic eruptions. At Versailles, Louis XIV built a fountain in his honor. When the Giant’s name was given to one of Saturn’s moons in the 19th century, no one had any idea what was on that faint dot in the sky, but it turns that Enceladus really does have underground rumblings and a mysterious fountain.
For two years, since the Cassini spacecraft in 2006 revealed a geyser-like plume of vapor and icy grains of dust being ejected near the south pole of this 300-mile wide moon, scientists have been intrigued by this rare phenomenon. Now a team of researchers in Germany and at the University of Leicester, writing in Nature, have explained some of the mechanics of these eruptions.
The geysers emerge from cracks in the moon’s surface that are hundreds of yards deep. In places where the cracks narrow, changes in pressure and temperature cause some of the vapor to condense into icy grains of dust. The mixture of vapor and dust erupt rapidly toward the surface, but the dust particles are slowed by collisions with the walls, and so they emerge more slowly than the vapor, according to the researchers, who say their work “suggests liquid water below Enceladus’ south pole.”
Given how few places in the solar system are believed to have water, Enceladus is high on many scientists’ list for future explorations. As my colleague Ken Chang reported, Enceladus is among “the small, highly select group of places in the solar system that could plausibly support life” because it has water, carbon-based molecules and heat. The source of the heat appears to be friction caused by the rubbing of the sides of the fissures against each other, which in turn is due to tidal forces related to Saturn’s gravitational pull — an interesting phenomenon, even it doesn’t have the literary appeal of a Giant writhing beneath the surface. | 0.873747 | 3.725286 |
The mystery of how blisteringly hot "Vulcan planets" form may now be one step closer to being solved, researchers say.
In the past two decades or so, researchers have confirmed the existence of more than 1,800 exoplanets orbiting distant stars. These discoveries have revealed very different kinds of planets from those seen in the solar system, such as super-Earths, which are rocky worlds up to 10 times the mass of Earth.
Unexpectedly, astronomers recently found a strange new class of alien planets — worlds in the Earth- to super-Earth size range whose orbits, which are tightly packed together very near their host stars, range from just 1 to 100 days long. Most of these planets are both far larger and much closer to their stars than Mercury, which is only about two-fifths the diameter of Earth and has an orbit 88 days long. [The Strangest Alien Planets]
"Almost 99 percent of the Vulcans are on orbits that are smaller than Mercury's orbit," said study co-author Jonathan Tan, an astrophysicist at the University of Florida in Gainesville. "Some are 100 times closer to their star than the Earth is to the sun."
Scientists have nicknamed these large, hot, rocky worlds "Vulcan planets." The name does not come from the home world of Spock's race in "Star Trek," but from the Roman god of fire, and it was also the name given to a planet that some astronomers had thought might exist inside Mercury's orbit in our solar system. The temperatures of Vulcans can be as high as about 1,340 degrees Fahrenheit (725 degrees Celsius), "similar to that of molten lava," Tan said. "Oceans of lava are a distinct possibility."
These compact systems of Vulcan planets "appear to be very common," Tan told Space.com. "Perhaps most planets in the galaxy are found in such systems."
However, explaining how Vulcan worlds could have formed remains a challenge for scientists. Some theorists propose Vulcan planets may have originated farther from their host stars, and each other, than they exist today. They would have then spiraled in to their present orbits, explaining what astronomers see now. However, some details of the spacing between these tightly packed exoplanets do not fit the pattern one would expect if this migration scenario were true.
Another possibility is that Vulcan planets gradually formed where they are now from a disk of so-called planetesimals — rocks the size of asteroids and moons. However, to get Vulcan planets to form this way so near their stars, one would need disks of planetesimals at least 20 times more massive than the disk that gave rise to Earth and the other planets in the solar system — an unlikely scenario, researchers say.
Recently, Tan and his colleague Sourav Chatterjee proposed a theory known as "inside-out planet formation" that may solve the mystery of how Vulcans take shape. It suggests that these worlds originated in the scorching-close orbits they occupy now from a stream of pebbles and small rocks that spiraled inward from more distant parts of their system. These stones accumulate in a ring around their star, and are kept from getting any closer by pressure forces in the inner disk around the star.
"We hypothesize that a planet will eventually form from this ring and will keep growing," Tan said.
Eventually, this planet grows massive enough to scoop up most of the matter near it, creating a mostly empty gap in the disk of gas and dust around the star. Pebbles and small rocks that continue to spiral inward from more distant parts of the system then form into a ring slightly farther away from the star, and this process of planetary formation begins anew.
"Planets form sequentially, one after another, from inner orbits to outer orbits, hence 'inside-out,'" Tan said.
In a new study of 629 Vulcan planets, the researchers now find that the greater the distance of these exoplanets from their parent star, the larger their mass. This matches a prediction of inside-out planetary formation.
"I am very excited to see that the observations appear to match the prediction," Tan said. "This may indicate that we are on the right track in understanding how they formed."
There are many aspects of this new theory that still need to be worked out in detail, Tan said. "One big question is why don't all disks form planets in this way — for example, why is our solar system different?"
Chatterjee and Tan detailed their findings online Dec. 29 in the Astrophysical Journal Letters. | 0.879491 | 3.781461 |
The existence of the elusive Planet 9 has been debated for years. If the mysterious planet really exists why haven’t we been able to detect it yet?
Astronomers are now saying that the mythical “Planet X” may actually be real. Scientists are calling it “Planet 9” and while it’s very difficult to produce clear evidence of its existence, some scientists are absolutely convinced that it’s out there. Something big is hiding beyond Pluto and we must find out what it is.
According to Konstantin Batygin, a planetary astrophysicist at Caltech in Pasadena, California, there are now five different lines of observational evidence pointing to the existence of Planet 9.
The planet has a mass ten times that of Earth’s, and is most likely situated twenty times as far from the Sun as Neptune.
“If you were to remove this explanation and imagine Planet Nine does not exist, then you generate more problems than you solve. All of a sudden, you have five different puzzles, and you must come up with five different theories to explain them,” Batygin said.
Elizabeth Bailey, Batygin’s graduate student showed that Planet Nine could have tilted the planets of our solar system during the last 4.5 billion years. This could explain a longstanding mystery: Why is the plane in which the planets orbit tilted about 6 degrees compared to the sun’s equator?
“Over long periods of time, Planet Nine will make the entire solar-system plane precess or wobble, just like a top on a table,” Batygin said.
The last telltale sign of Planet Nine’s presence involves the solar system’s contrarians: objects from the Kuiper Belt that orbit in the opposite direction from everything else in the solar system. Planet Nine’s orbital influence would explain why these bodies from the distant Kuiper Belt end up “polluting” the inner Kuiper Belt.
“No other model can explain the weirdness of these high-inclination orbits,” Batygin said. “It turns out that Planet Nine provides a natural avenue for their generation. These things have been twisted out of the solar system plane with help from Planet Nine and then scattered inward by Neptune.”
Not long ago, Spanish astronomers used a novel technique to analyze the orbits of the so-called extreme trans-Neptunian objects and, once again, they point out that there is something perturbing them: a planet located at a distance between 300 to 400 times the Earth-Sun separation.
Previous calculations supporting the theory Planet 9 does exists, were motivated by the peculiar distribution of the orbits found for the trans-Neptunian objects (TNO) of the Kuiper belt, which apparently revealed the presence of a Planet Nine or X in the confines of the Solar System.
Batygin and his team will now use the Subaru Telescope at Mauna Kea Observatory in Hawaii. The sophisticated tool is especially good for picking out dim, extremely distant objects lost in huge swaths of sky.
But where did Planet Nine come from? Batygin says he spends little time ruminating on its origin — whether it is a fugitive from our own solar system or, just maybe, a wandering rogue planet captured by the sun’s gravity.
“I think Planet Nine’s detection will tell us something about its origin,” he said.
Astronomers think Planet 9 could turn out to be our missing super Earth. | 0.83521 | 3.460444 |
The radial velocity of an object with respect to a given point is the rate of change of the distance between the object and the point. That is, the radial velocity is the component of the object's velocity that points in the direction of the radius connecting the point and the object. In astronomy, the point is usually taken to be the observer on Earth, so the radial velocity then denotes the speed with which the object moves away from the Earth (or approaches it, for a negative radial velocity).
In astronomy, radial velocity is often measured to the first order of approximation by Doppler spectroscopy. The quantity obtained by this method may be called the barycentric radial-velocity measure or spectroscopic radial velocity. However, due to relativistic and cosmological effects over the great distances that light typically travels to reach the observer from an astronomical object, this measure cannot be accurately transformed to a geometric radial velocity without additional assumptions about the object and the space between it and the observer. By contrast, astrometric radial velocity is determined by astrometric observations (for example, a secular change in the annual parallax).
Spectroscopic radial velocity
Light from an object with a substantial relative radial velocity at emission will be subject to the Doppler effect, so the frequency of the light decreases for objects that were receding (redshift) and increases for objects that were approaching (blueshift).
The radial velocity of a star or other luminous distant objects can be measured accurately by taking a high-resolution spectrum and comparing the measured wavelengths of known spectral lines to wavelengths from laboratory measurements. A positive radial velocity indicates the distance between the objects is or was increasing; a negative radial velocity indicates the distance between the source and observer is or was decreasing.
In many binary stars, the orbital motion usually causes radial velocity variations of several kilometers per second (km/s). As the spectra of these stars vary due to the Doppler effect, they are called spectroscopic binaries. Radial velocity can be used to estimate the ratio of the masses of the stars, and some orbital elements, such as eccentricity and semimajor axis. The same method has also been used to detect planets around stars, in the way that the movement's measurement determines the planet's orbital period, while the resulting radial-velocity amplitude allows the calculation of the lower bound on a planet's mass using the binary mass function. Radial velocity methods alone may only reveal a lower bound, since a large planet orbiting at a very high angle to the line of sight will perturb its star radially as much as a much smaller planet with an orbital plane on the line of sight. It has been suggested that planets with high eccentricities calculated by this method may in fact be two-planet systems of circular or near-circular resonant orbit.
Detection of exoplanets
The radial velocity method to detect exoplanets is based on the detection of variations in the velocity of the central star, due to the changing direction of the gravitational pull from an (unseen) exoplanet as it orbits the star. When the star moves towards us, its spectrum is blueshifted, while it is redshifted when it moves away from us. By regularly looking at the spectrum of a star—and so, measuring its velocity—it can be determined if it moves periodically due to the influence of an exoplanet companion.
From the instrumental perspective, velocities are measured relative to the telescope's motion. So an important first step of the data reduction is to remove the contributions of
- the Earth's elliptic motion around the sun at approximately ± 30 km/s,
- a monthly rotation of ± 13 m/s of the Earth around the center of gravity of the Earth-Moon system,
- the daily rotation of the telescope with the Earth crust around the Earth axis, which is up to ±460 m/s at the equator and proportional to the cosine of the telescope's geographic latitude,
- small contributions from the Earth polar motion at the level of mm/s,
- contributions of 230 km/s from the motion around the Galactic center and associated proper motions.
- in the case of spectroscopic measurements corrections of the order of ±20 cm/s with respect to aberration.
- Sin i degeneracy is the impact caused by not being in the plane of the motion.
- Resolution C1 on the Definition of a Spectroscopic "Barycentric Radial-Velocity Measure". Special Issue: Preliminary Program of the XXVth GA in Sydney, July 13–26, 2003 Information Bulletin n° 91. Page 50. IAU Secretariat. July 2002. https://www.iau.org/static/publications/IB91.pdf
- Lindegren, Lennart; Dravins, Dainis (April 2003). "The fundamental definition of "radial velocity"" (PDF). Astronomy and Astrophysics. 401 (3): 1185–1201. arXiv:astro-ph/0302522. Bibcode:2003A&A...401.1185L. doi:10.1051/0004-6361:20030181. Retrieved 4 February 2017.
- Dravins, Dainis; Lindegren, Lennart; Madsen, Søren (1999). "Astrometric radial velocities. I. Non-spectroscopic methods for measuring stellar radial velocity". Astron. Astrophys. 348: 1040–1051. arXiv:astro-ph/9907145. Bibcode:1999A&A...348.1040D.
- Resolution C 2 on the Definition of "Astrometric Radial Velocity". Special Issue: Preliminary Program of the XXVth GA in Sydney, July 13–26, 2003 Information Bulletin n° 91. Page 51. IAU Secretariat. July 2002. https://www.iau.org/static/publications/IB91.pdf
- Huggins, W. (1868). "Further observations on the spectra of some of the stars and nebulae, with an attempt to determine therefrom whether these bodies are moving towards or from the Earth, also observations on the spectra of the Sun and of Comet II". Philosophical Transactions of the Royal Society of London. 158: 529–564. Bibcode:1868RSPT..158..529H. doi:10.1098/rstl.1868.0022.
- Anglada-Escude, Guillem; Lopez-Morales, Mercedes; Chambers, John E. (2010). "How eccentric orbital solutions can hide planetary systems in 2:1 resonant orbits". The Astrophysical Journal Letters. 709 (1): 168–78. arXiv:0809.1275. Bibcode:2010ApJ...709..168A. doi:10.1088/0004-637X/709/1/168.
- Kürster, Martin; Trifonov, Trifon; Reffert, Sabine; Kostogryz, Nadiia M.; Roder, Florian (2015). "Disentangling 2:1 resonant radial velocity oribts from eccentric ones and a case study for HD 27894". Astron. Astrophys. 577: A103. arXiv:1503.07769. Bibcode:2015A&A...577A.103K. doi:10.1051/0004-6361/201525872.
- Ferraz-Mello, S.; Michtchenko, T. A. (2005). "Extrasolar Planetary Systems". Lect. Not. Phys. 683. pp. 219–271. Bibcode:2005LNP...683..219F. doi:10.1007/10978337_4.
- Reid, M. J.; Dame, T. M. (2016). "On the rotation speed of the Milky Way determined from HI emission". The Astrophysical Journal. 832 (2): 159. arXiv:1608.03886. Bibcode:2016ApJ...832..159R. doi:10.3847/0004-637X/832/2/159.
- Stumpff, P. (1985). "Rigorous treatment of the heliocentric motion of stars". Astron. Astrophys. 144 (1): 232. Bibcode:1985A&A...144..232S. | 0.936639 | 4.20556 |
240 B.C. Chinese astronomers observe a new broom-shaped "star" in the sky. It's the first confirmed sighting of Halley's Comet.
Some have made the case that a sighting in the third millennium B.C. is responsible for the alignment of the Sphinx and the pyramids of Giza. Interesting. Even a supposed Chinese sighting in 613 B.C. would be seven years later than the calculated 620 B.C. for a Halley's passage. Was that a record-keeping error or a different comet?
The 240 B.C. observation coincides with Halley's computed orbit, but its exact date is a matter of some imprecision. The existing Chinese record is the Records of the Grand Historian, or Shiji (or Shi Chi), written more than a century later around 100 B.C. What the Chinese called a "broom star," because of its bristly tail, appeared first in the east and then later in the north.
The text adds that it was also seen in the west during the lunar month of May 24 to June 23. Several astronomers calculated in the 1980s that the comet's closest approach to the sun was between March 22 and May 25 of 240 B.C. Those calculations also confirmed its apparent motion from east to north to west. March 30 is frequently given as the likely date for its first, though not necessarily the brightest, sighting.
Every subsequent passage of the comet was observed and recorded by astronomers in the Middle East, Asia and, eventually Europe. The 1066 appearance coincided with the Battle of Hastings, and an image of the comet was woven into the Bayeux Tapestry. Contemporary accounts say the comet looked to be four times bigger than Venus.
So, Halley: How did this guy get his name on what's probably the world's most famous comet? Edmond Halley was the British astronomer who first realized that some of history's recorded comets were in fact the same darn comet periodically returning to visibility from Earth.
Halley was using a newly discovered mathematical tool: Newton's calculus. He computed the parabolic orbits in 1705 for 24 comets that had been seen from 1337 until 1698. Hmm. The comets of 1531, 1607 (observed by Johannes Kepler) and 1682 moved in almost identical orbits, about 75 years apart.
Halley tried to account for variations in the orbit that would be caused by the comet passing the large outer planets, and then he predicted its return in 1758. He was right, but just barely, with the comet first seen on Christmas of that year.
Other astronomers took up the cudgels and discovered the same comet had in fact been seen and recorded on most of its 26 previous visits since 240 B.C., every 75 to 76 years. It reappeared in 1835, 1910 and 1986.
So, Halley: How do you pronounce that name, anyway? The conventional pronunciation rhymes with valley. Many Americans rhyme it with daily, thanks largely to the classic 1950s rockers, Bill Haley and the Comets. But if you really want to rock around the orbital clock, linguists and the dude's descendants agree it's pronounced Hawley, rhymes with folly.
See you in 2061.
Source: So various, so beautiful, so new
This article first appeared on Wired.com March 30, 2009.
- In Your Face: Close-Up Look at Doomed Comet
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- March 30, 1848: Niagara Falls Runs Dry | 0.814926 | 3.808502 |
Astronomers have discovered two new super-Earths orbiting an ancient 11.5 billion year-old star a "mere" 13 light-years from here. One planet is in the habitable zone, prompting a researcher to wonder what kind of life could have evolved over such a long period.
For comparison, these exoplanets are 2.5 times older than Earth and only two billion years younger than the universe itself, which is about 13.7 billion years-old. If there's life on one of these planets — and that's a big if — it's been there for a potentially very long time.
And amazingly, it's "only" 13 light-years away. That makes it the closest confirmed potentially habitable exoplanet to Earth, not including Tau Ceti e, an unconfirmed planet located 11.9 light-years away. The next best bet after that is Gliese 581-d, which is 20.2 light-years away. It's also worth noting that Alpha Centauri, the closest star to our own — just 4.3 light-years away — hosts a planet, but it's parked way to close to the sun to be habitable (its year is a mere three days long).
So, a bit about this discovery. These planets orbit Kapteyn's Star, a halo red dwarf that was discovered at the end of the 19th century by Dutch astronomer Jacobus Kapteyn. It's the second fastest moving star in the sky and the 25th closest star to our solar system. With a magnitude of nine it can be seen through a telescope or with a pair of binoculars. It has a third of the mass of the sun and can be seen in the southern constellation of Pictor.
New data analyzed by astronomers at the Queen Mary School of Physics now shows that Kapteyn is not alone; it's orbited by at least two super-Earths, Kapteyn-b and Kapteyn-c. The astronomers were looking at data collected from the HARPS spectrometer at the ESO's La Silla observatory in Chile. The findings were corroborated by data from HIRES at Keck Observatory and PFS at Magellan/Las Campanas Observatory. The new planets were found using the Doppler Effect, which shifts the star's light spectrum depending on its velocity. This technique allows astronomers to determine several properties of extrasolar planets, including their masses and orbital periods.
Kapteyn-b has a mass that's nearly five times that of Earth's. It may be able to sustain liquid water at its surface; Kapteyn-b orbits every 48 days, which places it in the circumstellar habitable zone. That might sound close — and it is — but keep in mind that red dwarfs are not as powerful as G-type main sequence stars like our own. The astronomers, a team led by Guillem Anglada-Escude, say it's the oldest potentially habitable planet known to date. And by my calculations, it's the closest known and confirmed potentially habitable planet to Earth.
The other planet, Kapteyn-c, is less promising in terms of habitability. It's a massive super-Earth that's seven times heavier than Earth, requiring about 121 days to complete an orbit. Astronomers think it's too cold to support liquid water.
The atmospheric composition of the planets is not known.
Kapteyn's Star has an interesting history. It was born in a dwarf galaxy that was absorbed and disrupted by the ancient Milky Way. This galactic event put the star in a rapid halo orbit. The likely remnant core of the original dwarf galaxy is thought to be Omega Centauri — a globular cluster located about 16,000 light-years from Earth which contains hundreds of thousands of similarly old suns.
This video simulation shows the merging and formation of the characteristic tidal streams of stars resulting from such a galactic merging event. | 0.913983 | 3.929654 |
By studying light echoes, rings of x-rays observed around binary star system Circinus X-1
Space news (astrophysics: measuring distances of objects; light echoes) – 30,700 light-years from Earth in the plane of the Milky Way Galaxy, observing X-rays emitted by a neutron star in double star system Circinus X-1 reflecting off massive, surrounding clouds of gas and dust –
Determining the apparent distance of objects tens of thousands of light-years from Earth across the breadth of the Milky Way was a difficult problem to solve during the early days of the human journey to the beginning of space and time. During the years since these early days, astronomers have developed a few techniques and methods to help calculate distances to stellar objects on the other side of the galaxy.
The most recently measured distance to an object on the other side of the Milky Way used the newest method developed. By detecting the rings from X-ray light echoes around the star Circinus X-1, a double star system containing a neutron star. Astronomers were able to determine the apparent distance to this system is around 30,700 light-years from Earth.
“It’s really hard to get accurate distance measurements in astronomy and we only have a handful of methods,” said Sebastian Heinz of the University of Wisconsin in Madison, who led the study. “But just as bats use sonar to triangulate their location, we can use the X-rays from Circinus X-1 to figure out exactly where it is.”
The rings are faint echoes from an outburst of x-rays emitted by Circinus X-1 near the end of 2013. The x-rays reflected off of separate clouds of gas and dust surrounding the star system, with some being sent toward Earth. The reflected x-rays arrived from different angles over a three month period, which created the observed X-ray rings. Using radio data scientists were able to determine the distance to each cloud of gas and dust, while detected X-ray echoes and simple geometry allowed for an accurate measurement of the distance to Circinus X-1 from Earth.
“We like to call this system the ‘Lord of the Rings,’ but this one has nothing to do with Sauron,” said co-author Michael Burton of the University of New South Wales in Sydney, Australia. “The beautiful match between the Chandra X-ray rings and the Mopra radio images of the different clouds is really a first in astronomy.”
In addition to this new distance measurement to Circinus X-1, astrophysicists determined this binary system’s naturally brighter in X-rays and other light than previously thought. This points to a star system that has repeatedly passed the threshold of brightness where the outward pressure of emitted radiation is balanced by the inward force of gravity. Astronomers have witnessed this equilibrium more often in binary systems containing a black hole, not a neutron star as in this case. The jet of high-energy particles emitted by this binary system’s also moving at 99.9 percent of the speed of light, which is a feature normally associated with a
The jet of high-energy particles emitted by this binary system’s also moving at 99.9 percent of the speed of light, which is a feature normally associated with a relativistic jet produced by a system containing a black hole. Scientists are currently studying this to see if they can determine why this system has such an unusual blend of characteristics.
“Circinus X-1 acts in some ways like a neutron star and in some like a black hole,” said co-author Catherine Braiding, also of the University of New South Wales. “It’s extremely unusual to find an object that has such a blend of these properties.”
Astronomers think Circinus X-1 started emitting X-rays observers on Earth could have detected starting about 2,500 years ago. If this is true, this X-ray binary system’s the youngest detected, so far, during the human journey to the beginning of space and time.
This new X-ray data is being used to create a detailed three-dimensional map of the dust clouds between Circinus X-1 and Earth.
Astrophysicists are preparing to measure distances to other stellar objects on the other side of the Milky Way using the latest distance measurement method. This new astronomy tool’s going to come in handy during the next leg of the human journey to the beginning of space and time.
Become a NASA Disk Detective and help classify embryonic planetary systems.
Read about the final goodbye of the Rosetta spacecraft, just before it crashes into the surface of comet 67P/Churyumov-Gerasimenko
Assess NASA’s contribution to the human journey to the beginning of space and time here.
Discover the Milky Way.
You can view the published results of this study in The Astrophysical Journal and online here.
Learn about astronomy at the University of Wisconsin.
Discover astronomy at the University of New South Wales.
Learn more about Circinus X-1.
Learn what NASA’s Chandra X-ray Observatory has shown us about the cosmos here. | 0.884005 | 3.902389 |
After studying for more than a decade the movements of the tectonic plates, those immense blocks of rock which form the surface of the earth, the physicist Marcelo Sousa de Assumpção came to an important conclusion. It had already been known that the continents, the visible parts of the tectonic plates, didn’t drift like a small wooden fishing raft without sails. The energy which moves them is certainly the heat contained within the interior of the planet. However, the tectonic plates are going towards or away from each other through convection currents, as in a pan of water being boiled and producing movement on the surface. A professor of the Astronomy and Geophysics Institute (IAG) of the University of São Paulo (USP), Assumpção coordinated a team which discovered that this movement may be much deeper than was at first thought.
According to him, all of the upper mantle, the layer below the crust, moves with the surface plates, at a depth which, at least here in Brazil, can reach to 700 kilometers – not just the 100 or 200 kilometers as it was previously accepted. This movement, now of amplified limits, involves just as much the upper mantle next to the crust, as the lower mantle, much deeper. “However, we can discard one of the previous hypothesis previously accepted which suggested that the convection movement was entirely confined to the upper mantle”, comments Assumpção, who is part of an international group of researchers in this area, also including specialists from the Carnegie Institution of Washington, United States and of the University of Montpellier in France.
This discovery will contribute to the refinement of the theory of the tectonic plates formulated at the beginning of the century by the German geophysicist Alfred Lothar Wegener (1880-1930). Until Wegener published his study Origins of the Continents and Oceans in 1915, it had been taken as certain that the surface of the earth was immovable – and there was no way of explaining in a reasonable and scientific manner, for example, earthquakes, today looked upon as a consequence of the meeting of plates. Killed during the last of three expeditions to Greenland, the German geophysicist proposed that in the geological past there was a unique continent, baptized as Pangaea, surrounded by an ocean called Panthalassa. The breaking up of Pangaea produced smaller blocks and one of them, Gondwana, as it broke up led to the origin of Africa, South America and Antarctica.
The starting point for Wegener to establish his theory of tectonic plates was the similarity between the coasts of Brazil and West Africa, which he saw as pieces which fitted together as in a giant jigsaw puzzle. Wegener thought that the continents drifted aimlessly, floating like enormous rocky boats on a layer of fluid rock which would be the mantle. He substantiated the idea of the drifting of the continents even if the mantle was solid and not fluid (the rocks of the mantle merely behave in a viscous manner when they are viewed on a scale over millions of years). Since that time, researchers from all over the world have mapped the trajectory of various plates, but only during the last few decades has it come about that the convection currents in the interior of the earth, linked directly to the movement of the plates, have begun to be detected by way of seismic tomography, a technique which maps the structures of the interior of the planet through the waves generated by earthquakes.
The team from USP investigated an area which forms a rectangle of 1,700 kilometers of length by 1,000 kilometers of breadth and has a depth of 1,400 kilometers in the Paraná river basin and surrounding area (see map on page 24). The first phase of the work, restricted to a rectangle of 800 kilometers by 400 kilometers, finished in 1995. It was successful enough to the point of justifying the present phase which began in July of 1997 and should be finished in July of this year.
In this project, Structure of the Crust and Upper Mantle in the Southeast of Brazil, with financing of R$173,400 by FAPESP, Assumpção carried out the surveying of the field and the interpretation of the data with the participation of the German geophysicist Martin Schimmel, who took his post doctorate at USP. In Brazil, the data collected during the project has been used as well in other pieces of research by the University of Brasilia, by the Technological Research Institute (IPT) of São Paulo, and by the National Observatory of Rio de Janeiro.
In the beginning, the researchers from USP and Carnegie, most directly involved with this work, used as sources of data the shock waves liberated by earthquakes, the P waves (longitudinal waves which are the first to reach the surface) and S waves (transversal waves) from different regions of the planet. Published in the magazine Nature on the 4th of November 1995, this preliminary research revealed, between the municipalities of São José do Rio Preto, Riberão Preto and Franca, in the interior of São Paulo, the existence of a structure interpreted as a very old volcanic channel in the mantle caused by a plume.
Deduced from studies on the computer and in a reduced laboratory scale, the plumes are columns of hot rock which originate at a profound depth in the mantle, and rise to the surface and cause extensive volcanic activity. In the last few years the plumes are finally being detected, such as that of the island of Iceland in the North Atlantic. According to Assumpção, this matter coming from the interior of the earth can perforate the crust with enormous projectiles and had an important role in the process of the rupture of the supercontinent Gondwana.
A piece of the fossil plume – however no longer active – of the interior of the state of São Paulo is situated at a depth of between 200 and 700 kilometers and has a width of approximately 300 kilometers. The temperature of this structure, according to the data obtained, is in the region of 1,700 degrees Celsius, at 200 degrees hotter than the region of its surroundings. According to Assumpção, this structure was at one point in the middle of the Atlantic ocean associated with the archipelago of Tristan da Cunha, a territory of the United Kingdom, of volcanic origin in the middle of the South Atlantic.
Afterwards, the rupture of Gondwana, which originated the present territories of Africa and South America, gave birth to the Atlantic Ocean around 130 million years ago. Evidently the tectonic plates have not quietened down. Even today, on the sea floor, where the crust is least thick, the movement of the plates produces fractures through which springs hot material from the mantle. This is the mechanism responsible for the Mid-Atlantic Ridge, of which the archipelago Tristão da Cunha is part. We are speaking of an area in which the plumes are still active – the so-called hot spots.
The data obtained in the Paraná Basin indicate that a piece of the plume, a column of hot material of the mantle, diverged to the west and, in this manner, accompanied the movement of the South American plate, it being today inactive and consequently a fossil. In the evaluation of the researchers, merely this discovery already brings an important contribution to the study of the dynamics of plates. Brazil is right in the middle of the South American plate which is moving west at a speed of 1.5 centimeters per year. Since the African plate is itself moving to the east at the same speed, the two continents are distancing themselves at a total velocity of three centimeters per year.
Moving towards the west, as a consequence of the movement of the mantle, the plume of the interior of the State of São Paulo is keeping itself under the Paraná basin until today. A little before the rupture of Gondwana, it was responsible for spilling of volcanic rock (basalt) which covered the surface for more than a thousand kilometers, starting from the point of origin. In this manner the researchers explain a geological characteristic of the Paraná Basin, the outcrops of basalt. Basalt, a volcanic rock of dark color, transformed itself into soil over millions of years and gave origin to the red and fertile soils of Paraná and part of the interior of São Paulo, which helped to maintain one of the most agriculturally productive areas of the country.
In the most recent study, Assumpção and Schimmel demarcate in a more exact way the column of hot material, the piece of the fossil plume, by way of some 38 seismographic stations distributed along the area of study, which extends from Brasilia until part of the state of Paraná. For this reason they had to travel close to 20,000 kilometers during the three years which the study has already taken. Every two months the researchers or the technicians traveled to the stations to collect the data which were stored by the computerized seismographs. Installed in small cabins normally on a farm, the sensors registered the soil vibrations, detecting on a daily basis, earthquakes which occurred in the whole world. At times, they also recorded the small low intensity earth tremors which take here in Brazil.
The speed which the shock waves of earthquakes reach the stations depends on the temperature of the rocks through which they pass. Thus, the researchers trace a profile of the lithosphere (the crust and a small rigid part of the upper mantle) and of the mantle up to a depth of 1,400 kilometers. Images made by computer also permit the visualization of the plume, contained within the mantle (see above).
One of the consequences of the plates dynamics is mountain formation as it has happened in the west of South America where we have the Andes.
This mountain chain, which runs from Chile up to Colombia, originated from the shock of the South American plate with another tectonic plate, that of Nazca, located under the Pacific. The shock ended up with the heavier Nazca plate diving under the lighter South American plate, drifting in the opposite direction. The shock of the plates amasses and thickens the border of the lighter plate. In the case of the South America and Nazca plates, the thickening of the western border of the South American plate resulted in the structure of the Andes, a still active process, and responsible for the frequent earthquakes and volcanoes of the Andean countries such as Ecuador and Colombia.
The technical advance of the detectors throughout the nineties permitted a qualitative leap in the gathering of data and the refining of models of the tectonic plates proposed by Wegener. With investigations deeper and deeper into the mantle it was possible to learn, for example, that in the processes of subduction – as are called the diving of one plate under another – the destruction of the plate which is diving only occurs at great depths, at times more than 1,000 or 2,000 kilometers.
“We have superseded the previous model which supposed that the diving plate dissolved itself away at a depth of only 700 kilometers”, comments Schimmel “Instead of this, on diving it remains intact without dissolving itself away.” Though constituted from the same material of the mantle, the plate is colder, more rigid and heavier – consequently it goes down more easily. The new technological resources allow us also to know that a plate can change its inclination, and from an almost vertical dive, can change to a horizontal movement. “What we know today, for certain, is that the deep earthquakes which occur up to 700 kilometers below the South American plate, are linked to the diving of the Nazca plate”, explains Assumpção “And it is also probable that the plate will continue diving to greater depths.” The tomography indicates a block of colder rock at approximately 1,300 kilometers below the region of the Southeast of Brazil in a range which extends from Brasilia to Curitiba, which seems to be a piece of the Nazca plate.
The discovery of a plume under the Paraná Basin was surprising. The researchers intend to study the region in order to make a comparison with other areas considered geologically to be very old, such as some regions in Canada. The interest was to discover how the earth’s lithosphere was formed in these areas known as cratons, a term which defines the geological provinces which have suffered little or no deformation since pre-Cambrian time, more or less 600 million years ago. Another objective of the work will be to determine the thickness of the crust and of the lithosphere plate in the Southeast, until now unknown, and to investigate the possibility that they might contain blocks just as old as those of the São Francisco craton in the basin of the São Francisco river in Minas Gerais.
The São Francisco craton, dating from around 3 billion years, is one of the oldest structures on the face of the planet. Now, the work of USP has defined the thickness of the craton which extends from the surface to a depth of around 300 kilometers. It also revealed the existence of a fossil plume giving evidence to the drag of the crust by the upper mantle. For Assumpção it is too early to evaluate if the discovery of the fossil plume might help in things as to forecast earthquakes, especially on the borders of the clashing of plates.
The immediate contribution to be seen, is to show that the upper mantle moves with the crust and in this way we will understand the forces to which a plate is submitted even in its internal part. In these areas also frequent earthquakes may occur. “One reason for earthquakes could be the concentration of tensions due to the variation of the thickness of the lithosphere”, he explains. This is what could be happening in a region with constant earth tremors which cut across the State of Goiás in the southwest to northeast direction. The region presents behavior similar to the central region of the United States where there has been satisfactorily established a relationship between earthquakes and a lower thickness of the lithosphere.
The USP researchers believe that the discovery of the structure of the plumes, associated with the understanding of great depths of diving of the plates, can lead to a greater interest in the investigation of the region of contact between the base of the mantle and the fluid core of the earth (the liquid sphere at the center of the earth has, in its interior a solid core). This region is layer D ’’ (read as D two lines) situated at approximately 2.700 kilometers from the surface. It is an area of physical and chemical reactions, very complex, between the fluid core and the pasty mantle whose structure may remind one of the irregular teeth of a spherical saw.
The geophysicists estimate that in this region the basic mechanism for the convection currents are located, the same type of force which makes water, which is boiling, circulate from bottom to top in the pan. “All that goes down has to come up”, argues Schimmel to establish the relationship between the diving of plates formed from cold material and the ascending currents of material at elevated temperatures. According to the theory in place, the heat from the core of the earth, a result of enormous gravitational energy which gave birth to the plates some 4.6 billion years ago along with the important addition contribution from natural radiation. When the earth was formed, the heat was so much that it melted everything. Iron, heavier, went into the center where it is until today. It could be that over the next few years that these consecrated ideas will be revised, from what we now know with respect to the movements of the tectonic plates and of the convection currents of the mantle.
Marcelo Sousa de Assumpção is 49 years of age. He graduated in physics from the Physics Institute of the University of São Paulo (USP) and is a doctor in Geophysics from the University of Edinburgh in Scotland. He has been a professor of the Astronomy and Geophysics Institute since 1974.
The Structure of the Crust and Upper Mantle in the South East of Brazil (nº 97/03640-6); Investment: R$ 173.478,14 | 0.811134 | 3.325767 |
The Dark Matter Particle Explorer (DAMPE) satellite China launched 310 miles in space in 2015 to collect cosmic ray data just picked up something extraordinary.
While hunting for traces of dark matter in the universe, the satellite nicknamed “Wukong” or “Monkey King,” detected a huge spike of unknown matter.
Fan Yizhong, deputy chief designer of DAMPE’s scientific application system, added that the spike was highly unusual. “The signals might have originated from either dark matter or pulsars,” he said.
Chinese Academy of Sciences’ scientists have been recording the DAMPE satellite’s findings for two years now and have measured over 3,500,000,000 high energy particles. This is the first anomaly in their electron and positron data spectrum. They are very excited but careful to not overreact to their discovery, waiting for higher probability scores from further analysis to confirm their expectations.
Why is this Important?
Basically, out of the 100% of the matter in the universe, we can only actually see ~5% of it. Then ~27% is “dark matter” that we cannot see but know exists because we can measure its gravitational influence. The last ~68% is the mysterious “dark energy” supposedly expanding everything in the universe.
A main dark matter theory is that whatever it is can decay into some matter we can see: electrons, positrons, photos, etc. So this is what China’s “Monkey King” DAMPE satellite has been scanning for.
Since scientists have painstakingly searched for hard proof of dark matter for decades with only failure after failure, you can see why this long-awaited little “blip” in the data is actually a huge deal.
The latest findings were published in Nature and show the spectral break at 0.9 TeV (tera-electron-volts) and a potential spike at 1.4 TeV. This discovery helps fine-tune the parameters for future models of cosmic phenomena like pulsars, supernovas, and dark matter.
In other words, they found visible particles of an invisible needle in the universal haystack and using those to help find evidence of more invisible needles.
“Together with data from the cosmic microwave background experiments, high energy gamma-ray measurements, and other astronomical telescopes, the DAMPE data may help to ultimately clarify the connection between the positron anomaly and the annihilation or decay of particle dark matter,” Fan Yizhong, said in a statement.
“DAMPE has opened a new window for observing the high-energy universe, unveiling new physical phenomena beyond our current understanding,” Chang Jin, chief scientist of DAMPE, told Xinhua.
“Our data may inspire some new ideas in particle physics and astrophysics. We never expected such signals.”
So this could propel scientists beyond the bounds of previous limitations. They could have the means to find and interact with the invisible matter of our universe. The potential implications and opportunities are indeed intriguing.
Chang continued: “The spike might indicate that there exists a kind of unknown particle with a mass of about 1.4 TeV. All the 61 elementary particles predicted by the standard model of particle physics have been found. Dark matter particles are beyond the list. So if we find a new elementary particle, it will be a breakthrough in physics. Even if they were from pulsars, it would be quite a strange astrophysical phenomenon that nobody had known before.”
But for now, the team will just keep logging cosmic ray data to increase their accuracy.
“So far, we are 99.99 percent sure this spike is real, but we need to collect more data. If the statistical probability exceeds 99.99994 percent, it will be a groundbreaking discovery in particle physics and astrophysics,” Chang said.
Even if this new data doesn’t solve the dark matter question, astrophysicist at Princeton University David Spergel says, “These measurements will inform our understanding of cosmic ray acceleration [and] will tell us about the physical processes in shocks around supernova and the physics of pulsars.”
And then what? I can’t wait for someone will invent a device that can see dark matter and reflect that onto a human’s brain so we can “see” the rest of the universe. Well, until then keep exploring outside the box. | 0.844466 | 3.950368 |
Supersonic winds stopped in their tracks – that’s what dunnit. This is the latest explanation for the giant bubbles that stick out above and below our galaxy.
In 2010, NASA’s FERMI gamma-ray telescope unveiled a stunning image of two bubbles – each 25,000 light years high – that emerge from the centre of the Milky Way, on either side of the galactic plane.
Several explanations have been put forward. One suggestion is that cosmic winds, made of gases and particles produced during intense episodes of star formation, blow out these Fermi bubbles, but the exact mechanism is unclear.
Now, Brian Lacki of the Institute for Advanced Study in Princeton, New Jersey, says the bubbles’ defined borders are the result of the cosmic winds coming to an abrupt stop.
These winds move at well over 1000 kilometres per second. Lacki suggests that they come to a sudden halt when their pressure equals the pressure of the gas around them. The abrupt transition from supersonic to subsonic speeds creates a termination shock wave, giving the Fermi bubbles their sharply defined boundaries (arxiv.org/abs/1304.6137).
The theory could solve another mystery: the source of the highest-energy cosmic rays that hit Earth. Lacki says that charged particles, accelerated by the shock wave, get trapped by magnetic fields in the bubble. They go around and around the fields until they become so energetic that they are ejected from the bubbles. Some arrive on Earth as high-energy cosmic rays.
More on these topics: | 0.869713 | 3.537607 |
Guest Opinion; Dr. Tim Ball
A recent article in the British newspaper The Express titled, “Northern Lights in the UK: Can you watch Aurora Borealis from UK? Where can you see it?” raises interesting questions and comparisons with historical events. It also appears to reinforce the climate forecasts for the next few decades.
Source: Daily Express
Sir Edmund Halley (1656 – 1742) was one of the great astronomers in history. He proved his science in the best way possible by making an accurate prediction. He predicted the return of a comet that they then named after him. I became familiar with his work while working on the climate record of the Hudson’s Bay Company (HBC) at Churchill, Manitoba.
The record was given a great scientific boost when in 1768/9 two astronomers, William Wales and Joseph Dymond arrived in Churchill to measure the Transit of Venus. Halley first identified this event and devised a procedure to gather data to determine the distance of the Earth from the Sun. This distance was critical to accurately testing Newton’s theory of gravity. A Transit occurred in 1761, but lack of knowledge and a useable technique resulted in failure. The 1769 Transit was critical because another Transit would not occur for 105 years.
Sir Neville Maskelyne, President of the Royal Society, sent the astronomers. They brought a range of instruments made specifically for them by the Society to carry out a range of scientific measures including thermometers and barometers. They left them at Churchill where the HBC employees continued to maintain some of the earliest instrumental records in North America.
In an interesting irony, Halley’s life spanned the coldest portion of the Little Ice Age with the nadir in 1680. To my knowledge, he did not write about this, but he did write about astronomical events related to it. For example, he was invited by the Royal Society to visit Scotland to observe and submit a report on the newly seen Aurora Borealis. His submission was published in their Philosophical Transactions, in 1714 under the magnificent title,
An account of the late surprizing appearance of the lights seen in the air, on the sixth of March last; with an attempt to explain the principal phænomena thereof; as it was laid before the Royal Society by Edmund Halley, J. V. D. Savilian Professor of Geom. Oxon, and Reg. Soc. Secr.
His abstract is very different from those we see in today’s academic or scientific journals, but this is a time when the title scientist did not exist. He wrote,
The Royal Society, having received accounts from very many parts of Great Britain, of the unusual lights which have of late appeared in the heavens ; were pleased to signify their desires to me, that I should draw up a general resation (sic) of the fact, and explain more at large some conceptions of mine I had proposed to them about it, as seeming to some of them to render a tollerable solution of the very strange and surprizing phænomena thereof.
He knew about them from earlier reports, and he also knew about their relationship with sunspots. He knew about sunspots from Galileo’s work but had not seen them either because his life also spanned a period with very few sunspots. The diagram shows the most accepted reproduction of sunspot numbers with only a few over Halley’s lifetime.
Aurora borealis or northern lights are among the most spectacular atmospheric displays. Called Aurora australis in the southern hemisphere they are visible evidence of the relationship between the sun and climate. In early days they called them Petty Dancers from the French petite danseurs. In England, they were also called Lord Derwentwater’s lights because they were unusually bright on February 24th, 1716, the day he was beheaded. A bad omen for him, but they were also an indicator of the bad weather and harvest failures of the period.
Ionized particles streaming out from the sun are called the solar wind. The term is misleading because they are solid electrically charged particles. Activity on the Sun is seen as sunspots and solar flares and coincides with variations in the strength of the solar wind. When these charged particles reach the upper levels of the earth’s atmosphere, they collide with the molecules of nitrogen and oxygen. This collision creates electrical charges that make the gas molecules glow. The gas determines the colours of the Aurora. Nitrogen produces red and oxygen the shades from almost white through yellow to green.
Many northern North American First Nations people used them to predict the weather. The Cree in Manitoba expected three to four weeks of cold weather after a prolonged period of display. This is very accurate as it relates to the average eastward movement of the Rossby Waves. Henry Youle Hind, leader of a scientific expedition across Canada, wrote on the 19th of September 1858 about Ojibway predictions:
We arrived at the mouth of the river at 10 A.M. and hastened to avail ourselves of a south-east wind just to rise. Last night the aurora was very beautiful, and extended far beyond the zenith, leading the voyageurs to predict a windy day. The notion prevails with them that when the aurora is low, the following day will be calm; when high, stormy.
Samuel Hearne spent two and one-half years with the Chipewyan, (then called the Northern Indians.) His report on their explanation of the aurora is fascinating.
The Northern Indians call the Aurora Borealis, Ed-thin; and when that meteor is very bright, they say that deer is plentiful in that part of the atmosphere;,,, Their ideas in this respect are founded on a principle one would not imagine. Experience has shewn tham, (sic) that when a hairy deer-skin is briskly stroked with the hand in a dark night, it will emit many sparks of electrical fire, as the back of a cat will.
This describes the phenomenon of static electricity and is remarkably close to the current explanation of the Aurora.
The composite image from NASA shows the Aurora from space as a circle around the Magnetic Pole.
Although at a higher altitude it is coincident with the dome of cold air that sits over the Pole.
The auroral ring expands and contracts as the cold air dome expands and contracts. This means when the Aurora is seen closer to the Equator there is cold pervading the Northern hemisphere. This is the situation of the last several years. It is accentuated by the change of pattern in the Rossby Waves along the Polar Front from low to high amplitude Waves. It results in more extreme outbreaks of cold air pushing further toward the Equator and warm air penetrating further to the Pole as the cold air moves out of the way.
Similar conditions occurred in the 17th century. Diarist Samuel Pepys (1633-1703) wrote about the conditions on many occasions. They were especially concerned about the mild winters, so the government recommended action. On January 15, 1662, Pepys wrote,
“And after we had eaten, he (Mr. Bechenshaw, a friend) asked me whether we have not committed a fault in eating today, telling me that it is a fastday, ordered by the parliament to pray for more seasonable weather it hitherto had been some summer weather, that is, both as to warm and every other thing, just as if it were the middle of May or June, which doth threaten a plague (as all men think) to follow, for so it was almost all last winter, and the whole year after hath been a very sickly time, to this day.”
The prayers paid off. On January 26th Pepys wrote,
“It having been a very fine clear frosty day. God send us more of them, for the warm weather all this winter makes us fear a sick summer.”
Pepys’ concern mirrors an old English saying that,
“A green winter makes a fat churchyard.”
His concern was well-founded because the plague returned, reaching London in 1665.
When you read the entire series of weather entries in Pepys’ diaries that cover the period 1660 – 1690, the pattern of remarkably variable weather is symptomatic of a Meridional Rossby Wave flow.
It was a similar pattern described in Barbara Tuchman’s 1978 book “A Distant Mirror; The Calamitous Fourteenth Century.” It was another example, like Halley of an important person, the nobleman Enguerrand VII de Courcy, whose life spanned an important climate period the 14th century, with weather comparable to the 17th century and the early 21st century. It lasted longer and was more profound because it was a transitional century as the world cooled from the Medieval Warm Period (MWP) to the Little Ice Age (LIA).
The current debate attracting more and more people is that we are cooling with the only question left as to the extent and intensity. Will it be weather similar to the cooler period coincident with the Dalton Minimum from 1790 – 1830? Alternatively, will it be colder with similar conditions to those by the early fur traders in Hudson Bay or those that spanned the life of Sir Edmund Halley? The appearance of Aurora in northern England suggests the latter, although I can predict who will protest this suggestion. | 0.823607 | 3.270634 |
Unlocking the Secrets of the Cosmos: The First Five years of AMS on the International Space Station
The Alpha Magnetic Spectrometer (AMS) Collaboration announces the fifth anniversary of the AMS Experiment on the International Space Station (ISS) and summarizes its major scientific results to date.
The AMS Experiment (shown in Figure 1) is the most sensitive particle detector ever deployed in space and is exploring a new and exciting frontier in physics research. As a magnetic spectrometer, AMS is unique in physics research as it studies charged particles and nuclei in the cosmos before they are annihilated in the Earth’s atmosphere. The improvement in accuracy over previous measurements is made possible through its long duration time in space, large acceptance, built in redundant systems and its thorough calibration in the CERN test beam. These features enable AMS to analyze the data to an accuracy of ~1%. The first five years of data from AMS on the International Space Station are beginning to unlock the secrets of the cosmos.
Figure 1. From its vantage point ~240 miles (400 km) above the Earth, the Alpha Magnetic Spectrometer (AMS) collects data from passing cosmic rays from primordial sources in the universe before they pass through the Earth’s atmosphere.
Since its installation on the ISS in May 2011, AMS has collected data from more than 90 billion cosmic rays with up to multi-TeV energies and published its major physics results in Physical Review Letters (Appendix I).
A note about cosmic rays: As the products of exploding supernovae, primary cosmic rays can travel for millions of years in the galaxy before reaching AMS. Secondary cosmic rays come from the interaction of primary cosmic rays with the interstellar media. Uniquely positioned on the International Space Station, AMS studies cosmic rays passing through its precision detectors, shown in Appendix II, to define the charge, energy, and momentum of the passing particles in order to obtain an understanding of dark matter, the existence of complex antimatter in space, the properties of primary and secondary cosmic rays as well as new, unexpected phenomena. These are among the fundamental issues in modern physics. Appendix III contains a brief summary of AMS for reference.
There are hundreds of different kinds of charged elementary particles. Only four of them – electrons, protons, positrons and antiprotons – have infinite lifetimes so they can travel through the cosmos forever. Electrons and positrons have much smaller mass than protons and antiprotons so they lose much more energy in the galactic magnetic field due to synchrotron radiation.
As shown in Figure 2, AMS has observed that the electron flux and positron flux display different behaviors both in their magnitude and in their energy dependence.
Figure 2. The electron flux and the positron flux are different in their magnitude and energy dependence.
Most surprisingly, from 60 to 500 GeV, positrons, protons and antiprotons display identical momentum dependence but electrons exhibit a totally different dependence as shown in Figure 3. The reason that this observation is surprising is that both electrons and positrons lose energy (or momentum) equally when travelling through the galactic magnetic field and at a much higher rate than protons or antiprotons.
Figure 3. The positron, proton, and antiproton spectra have identical momentum dependence from 60 to 500 GeV. The electron spectrum exhibits a totally different behavior, it decreases much more rapidly with increasing momentum.
There has been much interest over the last few decades in understanding the origin and nature of dark matter. When particles of dark matter collide, they produce energy that transforms into ordinary particles, such as positrons and antiprotons. The characteristic signature of dark matter is an increase with energy followed by a sharp drop off at the mass of dark matter as well as an isotropic distribution of the arrival directions of the excess positrons and antiprotons.
Figure 4 shows the latest results from AMS on the positron flux. As seen from the figure, after rising from 8 GeV above the rate expected from cosmic ray collisions, the spectrum exhibits a sharp drop off at high energies in excellent agreement with the dark matter model predictions with a mass of ~1 TeV. There is great interest in the physics community on the AMS measurements of elementary particles. For example, an alternative speculation for positron spectrum is that this rise and drop off may come from new astrophysical phenomena such as pulsars.
Figure 4. The current AMS positron flux measurement compared with theoretical models.
AMS has also studied the antiproton to proton ratio. The excess in antiprotons observed by AMS cannot easily be explained as coming from pulsars but can be explained by dark matter collisions or by other new astrophysics models. Antiprotons are very rare in the cosmos. There is only one antiproton in 10,000 protons therefore a precision experiment requires a background rejection close to 1 in a million. It has taken AMS five years of operations to obtain a clean sample of 349,000 antiprotons. Of these, AMS has identified 2200 antiprotons with energies above 100 billion electron volts. Experimental data on cosmic ray antiprotons are crucial for understanding the origin of antiprotons in the cosmos and for providing insight into new physics phenomena.
Protons are the most abundant particles in cosmic rays. AMS has measured the proton flux to an accuracy of 1% with 300 million protons and found that the proton flux cannot be described by a single power law, as had been assumed for decades, and that the proton spectral index changes with momentum.
AMS contains seven instruments (shown in Appendix II) with which to independently identify different elementary particles as well as nuclei. Helium, lithium, carbon, oxygen and heavier nuclei up to iron have been studied by AMS. It is believed that helium, carbon and oxygen were produced directly from primary sources in supernova remnants whereas lithium, beryllium and boron are believed to be produced from the collision of primary cosmic rays with the interstellar medium. Primary cosmic rays carry information about their original spectra and propagation, and secondary cosmic rays carry information about the propagation of primary and secondary cosmic rays and the interstellar medium.
Helium is the second most abundant cosmic ray. Helium has been studied over the past century. Although lithium is a secondary cosmic ray, its spectrum behaves similarly to protons and helium in that none of the three fluxes can be described by a single power law and they do change their behavior at the same energy.
Since protons, helium, carbon and oxygen are primary cosmic rays and produced at the same sources; thus their flux ratios should be rigidity independent. Rigidity is momentum per unit charge and is the metric by which magnetic fields, such as those experienced by cosmic rays between their origin and AMS, act on charged particles. From the AMS measurements, for carbon-to-helium and for carbon-to-oxygen these ratios are, indeed, independent of rigidity, i.e., flat, as expected. Unexpectedly, the proton-to-helium flux ratio drops quickly but smoothly with rigidity.
Other secondary cosmic rays being measured by AMS include boron and beryllium. The unstable isotope of beryllium, 10Be, has a half-life of 1.5 million years and decays into boron. The Be/B ratio therefore increases with energy due to time dilation when the Be approaches the speed of light. Hence, the ratio of beryllium to boron provides information on the age of the cosmic rays in the galaxy. From this, AMS has determined that the age of cosmic rays in the galaxy is ~12 million years.
The flux ratio between secondary cosmic rays (boron) and primary cosmic rays (carbon) provides information on propagation and the average amount of interstellar material (ISM) through which the cosmic rays travel in the galaxy. Cosmic ray propagation is commonly modeled as a fast moving gas diffusing through a magnetized plasma. Various models of the magnetized plasma predict different behavior of the boron-to-carbon (B/C) flux ratio. Remarkably, above 65 GeV, the B/C ratio measured by AMS is well described by a single power law B/C= kRδ with δ = -0.333±0.015. This is in agreement with the Kolmogorov turbulence model of magnetized plasma where δ = -1/3 asymptotically. Of equal importance, the B/C ratio does not show any significant structures in contrast to many cosmic ray models.
The carbon and oxygen fluxes, which are both primary cosmic rays, and the boron, lithium, and beryllium fluxes, which are secondary, have characteristically different rigidity dependences.
The Big Bang origin of the Universe requires that matter and antimatter be equally abundant at the very hot beginning of the universe. The search for the explanation for the absence of antimatter in a complex form is known as Baryogenesis. Baryogenesis requires both a strong symmetry breaking and a finite proton lifetime. Despite the outstanding experimental efforts over many years, no evidence of strong symmetry breaking nor of proton decay have been found. Therefore, the observation of a single anti-helium event in cosmic rays is of great importance.
In five years, AMS has collected 3.7 billion helium events (charge Z = +2). To date we have observed a few Z = -2 events with mass around 3 He. At a rate of approximately one antihelium candidate per year and a required signal (antihelium candidates) to background (helium) rejection of one in a billion, a detailed understanding of the instrument is required. In the coming years, with more data, one of our main efforts is to ascertain the origin of the Z = -2 events.
Most importantly, AMS will continue to collect and analyze data for the lifetime of the Space Station. As the results to date have demonstrated, whenever a precision instrument such as AMS is used to explore the unknown, new and exciting discoveries can be expected.
Major AMS Publications in Physical Review Letters
“First Result from the Alpha Magnetic Spectrometer on the International Space Station : Precision Measurement of the Positron Fraction in Primary Cosmic Rays of 0.5-350 GeV”, M. Aguilar et al., Phys. Rev. Lett. 110, 141102 (2013) (Selected as Editors’ Suggestion).
“High Statistics Measurement of the Positron Fraction in Primary Cosmic Rays of 0.5-500 GeV with the Alpha Magnetic Spectrometer on the International Space Station”, L. Accardo et al., Phys. Rev. Lett. 113, 121101 (2014) (Selected as Editors’ Suggestion)
“Electron and Positron Fluxes in Primary Cosmic Rays Measured with the Alpha Magnetic Spectrometer on the International Space Station”, M. Aguilar et al., Phys. Rev. Lett. 113, 121102 (2014) (Selected as Editors’ Suggestion).
“Precision Measurement of the (e+ + e-) Flux in Primary Cosmic Rays from 0.5 GeV to 1 TeV with the Alpha Magnetic Spectrometer on the International Space Station”, M. Aguilar et al., Phys. Rev. Lett. 113, 221102 (2014).
“Precision Measurement of the Proton Flux in Primary Cosmic Rays from Rigidity 1 GV to 1.8 TV with the Alpha Magnetic Spectrometer on the International Space Station”, M. Aguilar et al., Phys. Rev. Lett. 114, 171103 (2015) (Selected as Editors’ Suggestion).
“Precision Measurement of the Helium Flux in Primary Cosmic Rays of Rigidities 1.9 GV to 3 TV with the Alpha Magnetic Spectrometer on the International Space Station”, M. Aguilar et al., Phys. Rev. Lett., 115, 211101 (2015) (Selected as Editors’ Suggestion)
“Antiproton Flux, Antiproton-to-Proton Flux Ratio, and Properties of Elementary Particle Fluxes in Primary Cosmic Rays Measured with the Alpha Magnetic Spectrometer on the International Space Station”, M. Aguilar et al., Phys. Rev. Lett., 117, 091013 (2016).
“Precision Measurement of the Boron to Carbon Flux Ratio in Cosmic Rays from 1.9 GV to 2.6 TV with the Alpha Magnetic Spectrometer on the International Space Station”, M. Aguilar et al., Phys. Rev. Lett., 117, 231102 (2016) (Selected as Editors’ Suggestion). | 0.813856 | 4.008986 |
Three extrasolar comets have been discovered around the star Beta Pictoris, 63 light years away, by an international team including a University of Warwick researcher.
Analysis of data from the current NASA mission TESS has revealed the objects for the first time thanks to Sebastian Zieba and Konstanze Zwintz from the Institute of Astro- and Particle Physics at the University of Innsbruck, together with colleagues from Leiden University (Netherlands) and the University of Warwick (UK).
Just about a year after the launch of NASA mission TESS, the first three comets orbiting the nearby star Beta Pictoris outside our solar system were discovered in data from the space telescope.
The main goal of TESS is to search for exoplanets - planets orbiting other stars. The recognition of signals from much smaller exocomets compared to planets requires the analysis of a precise light curve, which can now be obtained using the technical sophistication of the new space telescope.
Sebastian Zieba, Master’s student in the team of Konstanze Zwintz at the Institute of Astro- and Particle Physics at the University of Innsbruck, discovered the signal of the exocomets when he investigated the TESS light curve of Beta Pictoris in March this year. "The data showed a significant decrease in the intensity of the light of the observed star. These variations due to darkening by an object in the star's orbit can clearly be related to a comet," Sebastian Zieba and Konstanze Zwintz explain the sensational discovery.
In collaboration with Matthew Kenworthy from the Leiden University (Netherlands) and Grant Kennedy from the University of Warwick (UK), they analysed and interpreted the signals of the exocomets. The results will now be published in the international journal "Astronomy and Astrophysics". Three similar exocomet systems have recently been found around three other stars during data analysis by NASA's Kepler mission. The researchers suggest that exocomets are more likely to be found around young stars. "The space telescope Kepler concentrated on older stars similar to the Sun in a relatively small area in the sky. TESS, on the other hand, observes stars all over the sky, including young stars. We therefore expect further discoveries of this kind in the future," says Konstanze Zwintz. Zwintz’s research focuses on young stars and is regarded as an internationally renowned expert in the field of asteroseismology.
Dr Grant Kennedy, from the University of Warwick Department of Physics, assisted with the modelling and interpretation of the data. He said: "This discovery is really important for the science of extrasolar comets for several reasons. Beta Pictoris had been thought to host exocomets for three decades from a different technique, and the TESS data provide long overdue and independent evidence for their existence. Our next aim is to find similar signatures around other stars, and this discovery shows that TESS is up to the task.”
The young and very bright star Beta Pictoris is a "celebrity" among astronomers for many reasons: "Already in the 1980s, investigations of Beta Pictoris provided convincing evidence for planetary systems around stars other than our Sun - a decade before exoplanets were even discovered for the first time. In addition, there was already indirect evidence for comets at that time based on the characteristic signature of evaporating gas coming off them," adds Konstanze Zwintz. At about 23 million years old, Beta Pictoris is a relatively young star, "a young adult star compared to human age," says the astronomer.
The discovery of exocomets around Beta Pictoris was predicted in 1999 in a paper by the astrophysicists Alain Lecavelier des Etangs, Alfred Vidal-Madjar and Roger Ferlet. "Together with our colleagues from Leiden and Warwick, we are pleased to have finally confirmed this theory," say Zieba and Zwintz. The scientists expect to discover many more comets and asteroids in this area, as it is a young star. "In the future, we want to find answers to the question of how often exocomets occur and whether their number really decreases with the age of a star. Information about this is important because by analysing the comets around a young star we can also draw conclusions about the history of our own solar system. Because we know that our solar system showed considerably more comets in 'young years'", explains Konstanze Zwintz.
In the future, the researchers want to investigate the composition of exocomets, for example regarding their water content. The comets themselves are smaller than exoplanets, but have very large tails, which can be up to many millions of kilometres long. "What we are seeing is not the comet nucleus itself, but the material blown off the comet and trailing behind it. So the TESS data do not tell us how big the comets were, since the extent of the dust tail could be very big and not very dense, or less big and more dense. Both situations would give the same light curve," explains Zwintz. | 0.930559 | 3.901472 |
How could life arise in young solar systems? We’re still not sure of the answer on Earth, even for something as basic as if water arose natively on our planet or was carried in from other locations. Seeking answers to life’s beginnings will require eyes in the sky and on the ground looking for alien worlds like our own. And just yesterday, the European Space Agency announced it is going to add to that search.
The newly selected mission is called PLATO, for Planetary Transits and Oscillations. Like NASA’s Kepler space telescope, PLATO will scan the sky in search of stars that have small, periodic dips in their brightness that happen when planets go across their parent star’s face.
“The mission will address two key themes of Cosmic Vision: what are the conditions for planet formation and the emergence of life, and how does the solar system work,” stated ESA, referring to its plan for space science missions that extends from 2015 to 2025.
PLATO will operate far from Earth in a spot known as L2, a relatively stable Lagrange point about 1.5 million kilometers (930,000 miles) away from Earth in the opposite direction from the sun. Sitting there for at least six years, the observatory (which is actually made up of 34 small telescopes and cameras) will examine up to a million stars across half of the sky.
A 2010 science proposal of the mission suggests that the satellite gather enough planetary transits to achieve three things:
- Find “statistically significant” Earth-mass planets in the habitable regions of several kinds of main-sequence stars;
- Figure out the radius and mass of the star and any planets with 1% accuracy, and estimate the age of exoplanet systems with 10% accuracy;
- Better determine the parameters of different kinds of planets, ranging from brown dwarfs (failed stars) to gas giants to rocky planets, all the way down to those that are smaller than Earth.
Adding PLATO’s observations to those telescopes on the ground that look at the radial velocity of planets, researchers will also be able to figure out each planet’s mass and radius (which then leads to density calculations, showing if it is made of rock, gas, or something else).
“The mission will identify and study thousands of exoplanetary systems, with an emphasis on discovering and characterising Earth-sized planets and super-Earths in the habitable zone of their parent star – the distance from the star where liquid surface water could exist,” ESA stated this week.
The telescope was selected from four competing proposals, which were EChO (the Exoplanet CHaracterisation Observatory), LOFT (the Large Observatory For x-ray Timing), MarcoPolo-R (to collect and return a sample from a near-Earth asteroid) and STE-Quest (Space-Time Explorer and QUantum Equivalence principle Space Test).
You can read more about PLATO at this website. It’s expected to launch from Kourou, French Guiana on a Soyuz rocket in 2024, with a budget of 600 million Euros ($822 million). And here’s more information on the Cosmic Vision and the two other M-class missions launching in future years, Euclid and Solar Orbiter.
Source: European Space Agency | 0.913749 | 3.839165 |
Cassini Sees Collisions of Moonlets on Saturn's Ring
June 6, 2008
(Source: The Science and Technology Facilities Council)
A team of scientists led from the UK has discovered that the rapid changes in Saturn's F ring can be attributed to small moonlets causing perturbations. Their results are reported in Nature (5th June 2008).
Saturn's F ring has long been of interest to scientists as its features change on timescales from hours to years and it is probably the only location in the solar system where large scale collisions happen on a daily basis. Understanding these processes helps scientists understand the early stages of planet formation.
Prof Carl Murray of Queen Mary, University of London and member of the Cassini Imaging Team led the analysis. He says “Saturn’s F ring is perhaps the most unusual and dynamic ring in the solar system; it has multiple structures with features changing on a variety of timescales from hours to years.”
The team used images gathered by the NASA-ESA Cassini Huygens mission. Images snapped by Cassini in 2006 and 2007 show the formation and evolution of a series of structures (called "jets" in the paper) that are the result of collisions between small nearby moonlets and the core of the F ring.
A ~5km object discovered by Cassini in 2004 (called S/2004 S 6) is the best candidate to explain some of the largest jets seen in the images.
Prof Murray adds “Previous research has noted the features in the F ring and concluded that either another moon of radius about 100km must be present and scattering the particles in the ring, or a much smaller moonlet was colliding with its constituent particles. We can now say that the moonlet is the most likely explanation and even confirm the identity of one culprit.”
The F ring and all the nearby objects are being continually perturbed by encounters with the shepherding moon Prometheus and this allows the gravitational signature of the embedded objects to be detected, even when the objects themselves cannot be seen.
Dr Sébastien Charnoz of Université Paris 7 / CEA Saclay is a co-author on the paper. He says “Large scale collisions happen in Saturn’s F ring almost daily – making it a unique place to study. We can now say that these collisions are responsible for the changing features we observe there.”
The Cassini images also show new features (called "fans") which result from the gravitational effect of small (~1km) satellites orbiting close to the F ring core.
Prof Keith Mason, STFC Chief Executive Officer, which funds UK involvement in Cassini-Huygens said “This incredibly successful mission has taught us a great deal about the solar system and the processes at work in it. Understanding how small objects move within the dust rings around Saturn gives an insight into the processes that drive planetary formation, where the proto-planet collects material in its orbit through a dust plane and carves out similar grooves and tracks.”
Notes for Editors
"The determination of the structure of Saturn's F ring by nearby moonlets"
Carl D. Murray, Kevin Beurle, Nicholas J. Cooper, Michael W. Evans, Gareth A. Williams & Sébastien Charnoz
Further images showing Saturn's F ring are available below:
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL.
For more information on the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov .
For more information on STFC, visit http://www.scitech.ac.uk/about/introduction.aspx
STFC Press Office
Tel: +44 (0)1793 442 094
Mob: +44 (0)7901 514 975
Prof Carl Murray
Queen Mary, University of London
Tel: +44 (0)20 7882 5456
Mob: +44 (0)7976 243 883
Dr Sébastien Charnoz
Université Paris 7 / CEA Saclay
Tel : +33 1 69 086 130
Fax: +33 1 69 086 577 | 0.813649 | 3.871859 |
In Strange New Worlds, renowned astronomer Ray Jayawardhana brings news from the front lines of the epic quest to find planets – and alien life – beyond our solar system. Only in the past two decades, after millennia of speculation, have astronomers begun to discover planets around other stars – thousands in fact. Now they are closer than ever to unraveling distant twins of the Earth. In Strange New Worlds, Jayawardhana vividly recounts the stories of the scientists and the remarkable breakthroughs that have ushered in this extraordinary age of exploration. He describes the latest findings – including his own – that are challenging our view of the cosmos and casting new light on the origins and evolution of planets and planetary systems. He reveals how technology is rapidly advancing to support direct observations of Jupiter-like gas giants and super-Earths – rocky planets with several times the mass of our own planet – and how astronomers use biomarkers to seek possible life on other worlds.
Strange New Worlds provides an insider's look at the cutting-edge science of today's planet hunters, our prospects for discovering alien life, and the debates and controversies at the forefront of extrasolar-planet research.
In a new afterword, Jayawardhana explains some of the most recent developments as we search for the first clues of life on other planets.
Chapter 1: Quest for Other Worlds: The Exciting Times We Live In 1
Chapter 2: Planets from Dust: Unraveling the Birth of Solar Systems 16
Chapter 3: A Wobbly Start: False Starts and Death Star Planets 46
Chapter 4: Planet Bounty: Hot Jupiters and Other Surprises 67
Chapter 5: Flickers and Shadows: More Ways to Find Planets 94
Chapter 6: Blurring Boundaries: Neither Stars nor Planets 123
Chapter 7: A Picture's Worth: Images of Distant Worlds 149
Chapter 8: Alien Earths: In Search of Wet, Rocky Habitats 172
Chapter 9: Signs of Life: How Will We Find E.T? 203
Selected Bibliography 239
About the Author 259
Ray Jayawardhana is professor and Canada Research Chair in Observational Astrophysics at the University of Toronto, as well as an award-winning science writer.
"Jayawardhana's small book is a gem. It brings readers up to date on the rapidly progressing quest for exoplanets and their potential inhabitants, and also interweaves the very human details about the people behind these discoveries. Read this book if you want a picture of how modern astronomy and astrobiology are helping to calibrate our place in the universe. A most delightful read."
– Jill Tarter, director of the Center for SETI Research
"Jayawardhana brings the latest cutting-edge science to all those astounding science-fictional visions of alien worlds, showing us that the universe is every bit as exciting as the masters of science fiction have always claimed. It's no accident that his title invokes the opening of the original Star Trek. In this terrific book, he boldly goes out into the galaxy, showing us strange – and wondrous – new worlds."
– Robert J. Sawyer, Hugo Award-winning author of Wake, Watch, and Wonder
"If you have ever wanted to know how astronomers are going to find an Earth-like planet, this engaging book explains it all. Not only is Strange New Worlds fantastic storytelling about the checkered and dramatic history of exoplanet discovery, but it also gives a compelling description of the path to future discoveries."
– Sara Seager, author of Exoplanet Atmospheres
"Strange New Worlds is a very satisfying book that does a thorough and excellent job of tracing the discovery and characterization of extrasolar planets. It is the only popular-level book that gives full, up-to-date, and in-depth coverage of one of the most exciting and fast-moving fields of scientific research."
– Greg Laughlin, coauthor of The Five Ages of the Universe: Inside the Physics of Eternity | 0.873805 | 3.454305 |
The discovery that supermassive black holes (SMBHs) with masses greater than 109 solar masses are in place within a billion years after the Big Bang represents a formidable theoretical challenge for current models of structure formation in the early Universe. How are such behemoths assembled in such a short time? The answer to this fundamental question relies on the solution to yet another unsolved problem: What are the pre-cursor black hole (BH) seeds and how do they form?
These are very pressing questions as a plethora of observations unequivocally suggest that the most massive SMBHs likely play a critical role in the formation and evolution of galaxies over cosmic time. For instance, the ionizing radiation produced by accreting massive BHs strongly affects the thermodynamics of the intergalactic medium (IGM), contributing to reionization of hydrogen at redshifts 6 − 8 and likely dominating the reionization of helium at redshift 3.5. Another is the direct impact that SMBHs have on their host galaxies. The current paradigm asserts that feedback from active galactic nuclei (AGN) is the dominant mechanism responsible for the observed truncation of star formation in the most massive galaxies. These are only a few examples of the influence that SMBHs exert on the assembly of structure in the universe. This underlines the need for a synthetic and comprehensive understanding of the life cycle a SMBH, from its birth at z > 10, through its youth as a rapidly growing quasar, and ultimately its adulthood, providing feedback that modulates its surroundings.
Our Theoretical and Computational Astrophysics Network (TCAN) is focused on the understanding that the cosmological role of SMBHs ultimately requires a detailed study and treatment of the multi-scale physics at work during formation and growth of the most massive SMBHs, as well as the feedback of these SMBHs on galactic structure. We will tackle this ambitious goal through collaborative research that cuts across traditional sub-disciplines of theoretical and computational astrophysics. To do so our network consists of a collaboration of scientists from 3 institutions: The University of Maryland at College Park, Georgia Institute for Technology and Yale University.
This material is based upon work supported by the National Science Foundation under Grant Numbers AST-1332858, AST-1333360, AST-1333514. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. | 0.893798 | 4.136542 |
- Scientific Article
(due to its nature, please prefer to read via Astronomy & Astrophysics)
Volume 584, December 2015
|Number of page(s)||13|
|Section||Galactic structure, stellar clusters and populations|
|Published online||16 November 2015|
1 Centro de Astrobiología, INTA-CSIC, Depto Astrofísica, ESAC Campus, PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain e-mail: [email protected]
2 Department of Astrophysics, University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
We construct a 3D map of the spatial density of OB stars within 500 pc from the Sun using the Hipparcos catalogue and find three large-scale stream-like structures that allow a new view on the solar neighbourhood. The spatial coherence of these blue streams and the monotonic age sequence over hundreds of parsecs suggest that they are made of young stars, similar to the young streams that are conspicuous in nearby spiral galaxies. The three streams are 1) the Scorpius to Canis Majoris stream, covering 350 pc and 65 Myr of star formation history; 2) the Vela stream, encompassing at least 150 pc and 25 Myr of star formation history; and 3) the Orion stream, including not only the well-known Orion OB1abcd associations, but also a large previously unreported foreground stellar group lying only 200 pc from the Sun. The map also reveals a remarkable and previously unknown nearby OB association, between the Orion stream and the Taurus molecular clouds, which might be responsible for the observed structure and star formation activity in this cloud complex. This new association also appears to be the birthplace of Betelgeuse, as indicated by the proximity and velocity of the red giant. If this is confirmed, it would solve the long-standing puzzle of the origin of Betelgeuse. The well-known nearby star-forming low-mass clouds, including the nearby T and R associations Lupus, Cha, Oph, CrA, Taurus, Vela R1, and various low-mass cometary clouds in Vela and Orion, appear in this new view of the local neighbourhood to be secondary star formation episodes that most likely were triggered by the feedback from the massive stars in the streams. We also recover well-known star clusters of various ages that are currently cruising through the solar neighbourhood. Finally, we find no evidence of an elliptical structure such as the Gould belt, a structure we suggest is a 2D projection effect, and not a physical ring.
Because of their relatively short lifetimes, massive O and B stars are a good tracer of recent star formation in the Milky Way and nearby galaxies. It was noted very early on that O and B stars are not distributed randomly on the sky (Herschel 1847; Gould 1879). Following the early canonical work of Eddington (1914), Kapteyn (1914), Charlier (1926), and Pannekoek (1929), Blaauw (1964) analysed the spatial and velocity distributions of OB stars in the solar neighbourhood to identify and study the content of nearby stellar groups. At the end of the last century, the accuracy and whole-sky coverage of the Hipparcos mission led to a major improvement in the definition and characterization of nearby OB associations and clusters, which profoundly changed our knowledge and understanding of the solar vicinity (e.g. Figueras et al. 1997; de Zeeuw et al. 1999; Platais et al. 1998; Subramaniam & Bhatt 2000; Hoogerwerf 2000; de Bruijne 2000; Branham 2002; Elias et al. 2006a,b).
There are two predominant methods for identifying stellar groups in the literature. The first consists of searching for concentrations in 2D projections of the position and/or velocity spaces. Starting with John Herschel and Benjamin Gould’s original observations, OB stars were grouped in a “belt” on the projected sky; this is known today as the Gould belt. As precise photometric or parallactic distance measurements were accumulating, the searches were performed in all possible 2D projections of their X, Y, Z Cartesian galactic coordinates (e.g. Charlier 1926; Stothers & Frogel 1974; Westin 1985; Elias et al. 2006b,and references therein). At the beginning of the twentieth century, the advent of precise proper motion measurements (and to a lesser extent, radial velocities) opened the search space to velocities. When the mean proper motion of a group is sufficiently high to distinguish it from the quasi-random velocity distribution of disk stars, its co-moving members are identified in 2D vector-point diagrams. Whenever radial velocities were also available, the search for co-moving stars was often made in 2D projections of their Cartesian galactic velocities (U vs. V, V vs. W, and U vs. W, e.g. Eggen 1984; Torres et al. 2006; Elias et al. 2006a, and references therein). But 2D projections are incapable of describing all the features of a 3D space, even if multiple projections are considered simultaneously. Important structures can be lost, hidden in the projection, while artificial structures can appear.
The second main procedure used to identify stellar groups relies on the convergent point method originally developed by Charlier that continued to be refined over the years (e.g. de Bruijne 1999; Galli et al. 2012). Because of perspective effects, groups of co-moving stars tend to move towards a common convergence point on the sky, while unrelated stars will move towards random directions. If a co-moving group exists, the paths defined by its members will intersect at the convergence point and the distribution of intersection points will be denser in that direction. The convergent point method has been widely and successfully used and led to the discovery or confirmation of most well-known OB associations and clusters listed in the extensive inventory of de Zeeuw et al. (1999). But it suffers from a major bias towards groups with high tangential motion. When the motion of a stellar group is mostly radial, the convergent point coincides with the projected geometric centre of the group. The discovery of such a group is often impeded because the typical relative error on the proper motion of current surveys is usually too large. This bias will in particular affect the identification of stellar groups at large heliocentric distances or located towards the solar apex or antapex. We show in the course of the present study the surprising consequences in the Orion and Vela star-forming complexes.
Finally, both methods can be affected by the presence of companions. The orbital motion of long-period binaries can add a significant non-linear component to the apparent motion and alter the proper motion measurements. This effect is particularly relevant for OB stars because of their high multiplicity rate. It did not affect the discovery of large conspicuous groups of OB stars whose co-motion will statistically dominate (de Zeeuw et al. 1999). But it might prevent the discovery of smaller and sparser groups of OB stars by shuffling the velocity measurements of a significant fraction of their members and diffusing the group coherence in the convergent point diagram. Therefore velocities should be used with caution when blindly searching for small groups of OB stars, and in particular in the subsequent assignment of membership probabilities to individual stars.
In the present study, we use the Hipparcos catalogue to revisit the cosmography of OB stars in the solar neighbourhood. Because of the drawbacks mentioned above, we focus on the 3D spatial distribution using modern full 3D data analysis and interactive visualization techniques instead of 2D projections, and refrain from using velocities as a discovery criterion for stellar groups.
…⇒ continue reading via Astronomy & Astrophysics | 0.846287 | 3.840329 |
It acquired its moniker because of its shape and its apparent color when seen in early images from Earth. This strikingly detailed Hubble image reveals how, when seen from space, the nebula, rather than being rectangular, is shaped like an X with additional complex structures of spaced lines of glowing gas, a little like the rungs of a ladder.
The star at the center is similar to the sun, but at the end of its lifetime, pumping out gas and other material to make the nebula, and giving it the distinctive shape. It also appears that the star is a close binary that is surrounded by a dense area of dust — both of which may help to explain the very curious shape.
The Red Rectangle is an unusual example of what is known as a proto-planetary nebula. These are old stars, on their way to becoming planetary nebulae. Once the expulsion of mass is complete a very hot white dwarf star will remain and its brilliant ultraviolet radiation will cause the surrounding gas to glow. The Red Rectangle is found about 2,300 light-years away in the constellation Monoceros (the Unicorn).
Text credit: European Space Agency
Image credit: ESA/Hubble and NASA | 0.88162 | 3.579829 |
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We live in an age in which tools are available that enable us to ''see'' some truly remarkable celestial vistas, writes Ian Griffin.
Have you ever wondered what your surroundings would look like if, rather than utilising visible light, your eyes could receive and process other wavelengths?
For stargazers' however, the fact that our visual cortex has evolved to see the world using a narrow band of colours can be a tad frustrating.
That's because the relative lack of sensitivity of the human eye means we miss out on some of the most wonderful sights in the universe. Luckily for us, we live in an age in which tools are available that enable us to ''see'' some truly remarkable celestial vistas which would otherwise be invisible.
To show you what I mean, let's turn our attention to the constellation Orion. This much-storied star assemblage rises just after midnight, and by dawn is high in the northern sky. Even to the much-maligned human eye, Orion is actually rather pretty.
It contains the bright stars Regulus and Betelgeuse and the region of the sky bounded by this constellation contains some marvellous objects, including the beautiful Orion Nebula, a dim fuzzy patch of light (just visible to the unaided eye on a clear dark night) which powerful telescopes reveal to be a stellar factory, where cosmic forces are forging a new generation of stars from cosmic dust and gas.
While Orion is certainly appealing at visual wavelengths, much is hidden from our eyes. To see what I have been missing, last week, in my Portobello back garden, I attached a special filter to my camera which only allowed passage of a narrow band of colours emitted by hydrogen atoms and then used this device to take a series of pictures of the sky.
In hydrogen light Orion becomes a veritable celestial wonderland, festooned by extraordinarily beautiful objects like Barnard's Loop, a massive bubble of gas some 300 light years in diameter that was created by an exploding star some two million years ago. It's amazing what you can ''see'' from your garden these days! | 0.865152 | 3.074854 |
Milky Way Photography
See the Milky Way
Look heavenward on a moonless summer night (in the Northern Hemisphere) far from city light. The first thing to strike you is the shear volume of stars, but as your eyes adjust, your gaze is drawn to a luminous band spanning the sky. Ranging from magnificently brilliant to faintly visible, this is the Milky Way, home to our sun and nearly a half trillion other stars of varying age, size, and temperature.
Size and shape
Though every star you’ve ever seen is part of our Milky Way galaxy, stargazers use the Milky Way label more specifically to identify this river of starlight, gas, and dust spanning the night sky. As you feast your eyes, appreciate that some of the Milky Way’s starlight has traveled 25,000 years to reach your eyes, and light from a star on one edge of the Milky Way would take 100,000 years to reach the other side.
The rest of the sky appears to be filled with far more discrete stars than the region containing the Milky Way, but don’t let this deceive you. Imagine that you’re out in the countryside where the lights of a distant city blend into a homogeneous glow—similarly, the stars in the Milky Way’s luminous band are simply too numerous and distant to resolve individually. On the other hand, the individual pinpoints of starlight that we name and mentally assemble into constellations are just closer, much like the lights of nearby farmhouses. And the dark patches in the Milky Way aren’t empty space—like the trees and mountains that block our view of the city, they’re starlight-blocking interstellar dust and gas, remnants of exploded stars and the stuff of future stars.
Just as it’s impossible to know what your house looks like by peering out a window, it’s impossible to know what the Milky Way looks like by simply looking up on a dark night. Fortunate for us, really smart people have been able to infer from painstaking observation, measurement, reconstruction, and comparison with other galaxies that our Milky Way is flat (much wider than it is tall) and spiral shaped, like a glowing pinwheel, with two major arms and several minor arms spiraling out from its center. Our solar system is in one of the Milky Way’s minor arms, a little past midway between the center and outer edge.
Blinded by the light
Sadly, artificial light and atmospheric pollution have erased the view of the Milky Way for nearly a third of the world’s population, and eighty percent of Americans. Worse still, even though some part of the Milky Way is overhead on every clear night, many people have never seen it.
Advances in digital technology have spurred a night photography renaissance that has enabled the Milky Way challenged to enjoy images of its splendor from the comfort of their recliner, but there’s nothing quite like viewing it in person. With just a little knowledge and effort, you too can enjoy the Milky Way firsthand; add the right equipment and a little more knowledge, and you’ll be able to photograph it as well.
Horizon to Horizon
Understanding that our Solar System is inside the Milky Way’s disk makes it easier to understand why we can see some portion of the Milky Way on any night (assuming the sky is dark enough). In fact, from our perspective, the plane of the Milky Way forms a complete ring around Earth (but of course we can only see half the sky at any given time), with its brightness varying depending on whether we’re looking toward our galaxy’s dense center or sparse outer region.
Where the action is
Though the plane of the Milky Way stretches all the way across our sky, when photographers talk about photographing the Milky Way, they usually mean the galactic core—the Milky Way’s center and most densely packed, brightest region. Unfortunately, our night sky doesn’t always face the galactic core, and there are many months when this bright region is not visible at all.
To understand the Milky Way’s visibility in our night sky, it helps to remember that Earth both rotates on its axis (a day), and revolves around the sun (a year). When the side of the planet we’re on rotates away from the sun each day, the night sky we see is determined by our position on our annual trip around the sun—when Earth is between the sun and the galactic core, we’re in position to see the most brilliant part of the Milky Way; in the months when the sun is between earth and the galactic core, the bright part of the Milky Way can’t be seen.
Put in terrestrial terms, imagine you’re at the neighborhood playground, riding a merry-go-round beneath a towering oak tree. You face outward, with your back to the merry-go-round’s center post. As the merry-go-round spins, your view changes—about half of the time you’d rotate to face the oak’s trunk, and about half the time your back is to the tree. Our solar system is like that merry-go-round: the center post is the sun, the Milky Way is the tree, and in the year it takes our celestial merry-go-round to make a complete circle, we’ll face the Milky Way about half the time.
Finding the Milky Way
Just like every other celestial object outside our solar system, the Milky Way’s position in our sky changes with the season and time of night you view it, but it remains constant relative to the other stars and constellations. This means you can find the Milky Way by simply locating any of the constellations in the galactic plane. Here’s an alphabetical list of the constellations* through which the Milky Way passes (with brief notes by a few of the more notable constellations):
- Canis Major—faint
- Cassiopeia—faint; its easily recognized “w” (or “m”) shape makes Cassiopeia a good landmark for locating the Milky Way in the northern sky
- Orion—faint; another easy to recognize constellation that’s good for finding the galactic plane
- Sagittarius—brightest, galactic core
* Constellations are comprised of stars that only appear connected by virtue of our Earth-bound perspective—a constellation is a direction in the sky, not a location in space.
If you can find any of these constellations, you’re looking in the direction of some part of the Milky Way (if you can’t see it, your sky isn’t dark enough). But most of us want to see the center of the Milky Way, where it’s brightest, most expansive, and most photogenic. The two most important things to understand about finding the Milky Way’s brilliant center are:
- From our perspective here on Earth, the galactic core is in Sagittarius (and a couple of other constellations near Sagittarius)—when Sagittarius is visible, so is the brightest part of the Milky Way (assuming you can find a dark enough sky)
- Earth’s night side most directly faces Sagittarius in the Northern Hemisphere’s summer months (plus part of spring and autumn)
Armed with this knowledge, locating the Milky Way’s core is as simple as opening one of my (too many) star apps to find out where Sagittarius is. Problem solved. Of course it helps to know that the months when the galactic core rises highest and is visible longest are June, July, and August, and to not even consider looking before mid-March, or after mid-October. If you can’t wait until summer and don’t mind missing a little sleep, starting in April, Northern Hemisphere residents with a dark enough sky can catch Sagittarius and the galactic core rising in the southeast shortly before sunrise. After its annual premier in April, the Milky Way’s core rises slightly earlier each night and is eventually well above the horizon by nightfall.
People who enjoy sleep prefer doing their Milky Way hunting in late summer and early autumn, when the galactic core has been above the horizon for most of the daylight hours, but remains high in the southwest sky as soon as the post-sunset sky darkens enough for the stars to appear. The farther into summer and autumn you get, the closer to setting beneath the western horizon the Milky Way will be at sunset, and the less time you’ll have before it disappears.
Into the darkness
The Milky Way is dim enough to be easily washed out by light pollution and moonlight, so the darker your sky, the more visible the Milky Way will be. To ensure sufficient darkness, I target moonless hours, from an hour or so after sunset to an hour before sunrise. New moon nights are easiest because the new moon rises and sets (more or less) with the sun and there’s no moon all night. But on any night, if you pick a time before the moon rises, or after it sets, you should be fine. Be aware that the closer the moon is to full, the greater the potential for its glow to leak into the scene from below the horizon.
Getting away from city lights can be surprisingly difficult (and frustrating). Taking a drive out into the countryside near home is better than nothing, and while it may seem dark enough to your eyes, a night exposure in an area that you expect to be dark enough reveals just how insidious light pollution is as soon as you realize all of your images are washed out by an unnatural glow on the horizon. Since the galactic core is in the southern sky in the Northern Hemisphere, you can mitigate urban glow in your Milky Way images by heading south of any nearby population area, putting the glow behind you as you face the Milky Way.
Better than a night drive out to the country, plan a trip to a location with a truly dark sky. For this, those in the less densely populated western US have an advantage. The best resource for finding world-class dark skies anywhere on Earth is the International Dark-Sky Association. More than just a resource, the IDA actively advocates for dark skies, so if the quality of our night skies matters to you, spend some time on their site, get involved, and share their website with others.
Photograph the Milky Way
Viewing the Milky Way requires nothing more than a clear, dark sky. (Assuming clean, clear skies) the Milky Way’s luminosity is fixed, so our ability to see it is largely a function of the darkness of the surrounding sky—the darker the sky, the better the Milky Way stands out. But because our eyes can only take in a fixed amount of light, there’s a ceiling on our ability to view the Milky Way with the unaided eye.
A camera, on the other hand, can accumulate light for a virtually unlimited duration. This, combined with technological advances that continue increasing the light sensitivity of digital sensors, means that when it comes to photographing the Milky Way, well…, the sky’s the limit. As glorious as it is to view the Milky Way with the unaided eye, a camera will show you detail and color your eyes can’t see.
Knowing when and where to view the Milky Way is a great start, but photographing the Milky Way requires a combination of equipment, skill, and experience that doesn’t just happen overnight (so to speak). But Milky Way photography doesn’t need to break the bank, and it’s not rocket science.
Bottom line, photographing the Milky Way is all about maximizing your ability to collect light: long exposures, fast lenses, high ISO.
In general, the larger your camera’s sensor and photosites (the “pixels” that capture the light), the more efficiently it collects light. Because other technology is involved, there’s not an absolute correlation between sensor and pixel size and light gathering capability, but a small, densely packed sensor almost certainly rules out your smartphone and point-and-shoot cameras for anything more than a fuzzy snap of the Milky Way. At the very least you’ll want a mirrorless or DSLR camera with an APS-C (1.5/1.6 crop) size sensor. Better still is a full frame mirrorless or DSLR camera. (A 4/3 Olympus or Panasonic sensor might work, but as great as these cameras are for some things, high ISO photography isn’t their strength.
Another general rule is that the newer the technology, the better it will perform in low light. Even with their smaller, more densely packed sensors, many of today’s top APS-C bodies outperform in low light full frame bodies that have been out for a few years, so full frame or APS-C, if your camera is relatively new, it will probably do the job.
If you’re shopping for a new camera and think night photography might be in your future, compare your potential cameras’ high ISO capabilities—not their maximum ISO. Read reviews by credible sources like DP Review, Imaging Resource, or DxOMark (among many others) to see how your camera candidates fare in objective tests.
An often overlooked consideration is the camera’s ability to focus in extreme low light. Autofocusing on the stars or landscape will be difficult to impossible, and you’ll not be able to see well enough through a DSLR’s viewfinder to manually focus. Some bodies with a fast lens might autofocus on a bright star or planet, but it’s not something I’d count on (though I expect within a few years before this capability will become more common).
Having photographed for years with Sony and Canon, and working extensively with most other mirrorless and DSLR bodies in my workshops, I have lots of experience with cameras from many manufacturers. In my book, focus peaking makes mirrorless the clear winner for night focusing. Sony’s current mirrorless bodies (a7RII/RIII, a7S/SII) are by far the easiest I’ve ever used for focusing in the dark—what took a minute or more with my Canon, I can do in seconds using focus peaking with my Sony bodies (especially the S bodies). I use the Sony a7SII, but when I don’t want to travel with a body I only use for night photography, the Sony a7RIII does the job too. Of the major DSLR brands, I’ve found Canon’s superior LCD screen (as of 2019) makes it much easier to focus in extreme low light than Nikon. (More on focus later.)
Put simply, to photograph the Milky Way you want fast, wide glass—the faster the better. Fast to capture as much light as possible; wide to take in lots of sky. A faster lens also makes focus and composition easier because the larger aperture gathers more light. How fast? F/2.8 or faster—preferably faster. How wide? At least 28mm, and wider is better still. I do enough night photography that I have a dedicated, night-only lens—my original night lens was a Canon-mount Zeiss 28mm f/2; my current night lens is the Sony 24mm f/1.4.
It goes without saying that at exposure times up to 30 seconds, you’ll need a sturdy tripod and head for Milky Way photography. You don’t need to spend a fortune, but the more you spend, the happier you’ll be in the long run (trust me). Carbon fiber provides the best combination of strength, vibration reduction, and light weight, but a sturdy (albeit heavy) aluminum tripod will do the job.
An extended centerpost is not terribly stable, and a non-extended centerpost limits your ability to spread the tripod’s legs and get low, so I avoid tripods with a centerpost. But if you have a sturdy tripod with a centerpost, don’t run out and purchase a new one—just don’t extend the centerpost when photographing at night.
Read my tips for purchasing a tripod here.
To eliminate the possibility of camera vibration I recommend a remote release; without a remote you’ll risk annoying all within earshot with your camera’s 2-second timer beep. You’ll want a flashlight or headlamp for the walk to and from the car, and your cell phone for light while shooting. And it’s never a bad idea to toss an extra battery in your pocket. And speaking of lights, never, never, NEVER use a red light for night photography (more on this later).
Getting the shot
Keep it simple
There are just so many things that can go wrong on a moonless night when there’s not enough light to see camera controls, the contents of your bag, and the tripod leg you’re about to trip over. After doing this for many years, both on my own and helping others in workshops, I’ve decided that simplicity is essential.
Simplicity starts with paring down to the absolute minimum camera gear: a sturdy tripod, one body, one lens, and a remote release (plus an extra battery in my pocket). Everything else stays at home, in the car, or if I’m staying out after a sunset shoot, in my bag.
Upon arrival at my night photography destination, I extract my tripod, camera, lens (don’t forget to remove the polarizer), and remote release. I connect the remote and mount my lens—if it’s a zoom I set the focal length at the lens’s widest—then set my exposure and focus (more on exposure and focus below). If I’m walking to my photo site, I carry the pre-exposed and focused camera on the tripod (I know this makes some people uncomfortable, but if you don’t trust your tripod head enough to hold onto your camera while you’re walking, it’s time for a new head), trying to keep the tripod as upright and stable as possible as I walk.
Flashlights/headlamps are essential for the walk/hike out to to and from my shooting location, but while I’m there and in shoot mode, it’s no flashlights, no exceptions. This is particularly important when I’m with a group. Not only does a flashlight inhibit your night vision, its light leaks into the frame of everyone who’s there. And while red lights may be better for your night vision and are great for telescope view, red light is especially insidious about leaking into everyone’s frame, so if you plan to take pictures, no red light! If you follow my no flashlight rule once the photography begins, you’ll be amazed at how well your eyes adjust. I can operate my camera’s controls in the dark—it’s not hard with a little practice, and well worth the effort to learn. If I ever do need to see my camera to adjust something, or if I need to see to move around, my cell phone screen (not the phone’s flashlight, just its illuminated screen) gives me all the light I need.
A good Milky Way image is distinguished from an ordinary Milky Way image by its foreground. Simply finding a location that’s dark enough to see the Milky Way is difficult enough; finding a dark location that also has a foreground worthy of pairing with the Milky Way usually takes a little planning.
Since the Milky Way’s center is in the southern sky (for Northern Hemisphere observers), I look for remote (away from light pollution) subjects that I can photograph while facing south (or southeast or southwest, depending on the month and time of night). Keep in mind that unless you have a ridiculous light gathering camera (like the Sony a7S or a7S II) and an extremely fast lens (f/2 or faster), your foreground will probably be more dark shape than detail. Water’s inherent reflectivity makes it a good foreground subject as well, especially if the water includes rocks or whitewater.
When I encounter a scene I deem photo worthy, not only do I try to determine its best light and moon rise/set possibilities, I also consider its potential as a Milky Way subject. Can I align it with the southern sky? Are there strong subjects that stand out against the sky? Is there water I can include in my frame?
I’ve found views of the Grand Canyon from the North Rim, the Kilauea Caldera, and the bristlecone pines in California’s White Mountains that work spectacularly. And its hard to beat the dark skies and breathtaking foreground possibilities at the bottom of the Grand Canyon. On the other hand, while Yosemite Valley has lots to love, you don’t see a lot of Milky Way images from Yosemite Valley because not only is there a lot of light pollution, and Yosemite’s towering, east/west trending granite walls give its south views an extremely high horizon that blocks much of the galactic core from the valley floor.
The last few years I’ve started photographing the Milky Way above the spectacular winter scenery of New Zealand’s South Island, where the skies are dark and the Milky Way is higher in the sky than it is in most of North America.
To maximize the amount of Milky Way in my frame, I generally (but not always) start with a vertical orientation that’s at least 2/3 sky. On the other hand, I do make sure to give myself more options with a few horizontal compositions as well. Given the near total darkness required of a Milky Way shoot, it’s often too dark to see well enough to compose that scene. If I can’t see well enough to compose I guess at a composition, take a short test exposure at an extreme (unusable) ISO to enable a relatively fast shutter speed (a few seconds), adjust the composition based on the image in the LCD, and repeat until I’m satisfied.
Needless to say, when it’s dark enough to view the Milky Way, there’s not enough light to autofocus (unless you have a rare camera/lens combo that can autofocus on a bright star and planet), or even to manually focus with confidence. And of all the things that can ruin a Milky Way image (not to mention an entire night), poor focus is number one. Not only is achieving focus difficult, it’s very easy to think you’re focused only to discover later that you just missed.
Because the Milky Way’s focus point is infinity, and you almost certainly won’t have enough light to stop down for more depth of field, your closest foreground subjects should be far enough away to be sharp when you’re wide open and focused at infinity. Before going out to shoot, find a hyperfocal app and plug in the values for your camera and lens at its widest aperture. Even though it’s technically possible to be sharp from half the hyperfocal distance to infinity, the kind of precise focus focusing on the hyperfocal point requires is difficult to impossible in the dark, so my rule of thumb is to make sure my closest subject is no closer than the hyperfocal distance.
For example, I know with my Sony 24mm f/1.4 wide open on my full frame Sony a7SII, the hyperfocal distance is about 50 feet. If I have a subject that’s closer (such as a bristlecone pine), I’ll pre-focus (before dark) on the hyperfocal distance, or shine a bright light on an object at the hyperfocal distance and focus there, but generally I make sure everything is at least 50 feet away. Read more about hyperfocal focus in my Depth of Field article.
By far the number one cause of night focus misses is the idea that you can just dial any lens to infinity; followed closely by the idea that focused at one focal length means focused at all focal lengths. Because when it comes to sharpness, almost isn’t good enough, if you have a zoom lens, don’t even think of trying to dial the focus ring to the end for infinity. And even for most prime lenses, the infinity point is a little short of all the way to the end, and can vary slightly with the temperature and f-stop. Of course if you know your lens well enough to be certain of its infinity point by feel (and are a risk taker), go for it. And that zoom lens that claims to be parfocal? While it’s possible that your zoom will hold focus throughout its entire focal range, regardless of what the manufacturer claims, I wouldn’t bet an entire shoot on it without testing first.
All this means that the only way to ensure night photography sharpness is to focus carefully on something before shooting, refocus every time your focal length changes, and check focus frequently by displaying and magnifying an image on your LCD. To simplify (there’s that word again), when using a zoom lens, I usually set the lens at its widest focal length, focus, verify sharpness, and (once I know I’m focused) never change the focal length again.
While the best way to ensure focus is to set your focal length and focus before it gets dark, sometimes pre-focusing isn’t possible, or for some reason you need to refocus after darkness falls. If I arrive at my destination in the dark, I autofocus on my headlights, a bright flashlight, or a laser 50 feet or more away. And again, never assume you’re sharp by looking at the image that pops up on the LCD when the exposure completes—always magnify your image and check it after you focus.
For more on focusing in the dark, including how to use stars to focus, read my Starlight Photo Tips article.
Exposing a Milky Way image is wonderfully simple once you realize that you don’t have to meter—because you can’t (not enough light). Your goal is simply to capture as many photons as you can without damaging the image with noise, star motion, and lens flaws.
Basically, with today’s technology you can’t give a Milky Way image too much light—you’ll run into image quality problems before you overexpose a Milky Way image. In other words, capturing the amount of light required to overexpose a Milky Way image is only possible if you’ve chosen an ISO and/or shutter speed that significantly compromises the quality of the image with excessive noise and/or star motion.
In a perfect world, I’d take every image at ISO 100 and f/8—the best ISO and f-stop for my camera and lens. But that’s not possible when photographing in near total darkness—a usable Milky Way image requires exposure compromises. What kind of compromises? The key to getting a properly exposed Milky Way image is knowing how far you push your camera’s exposure settings before the light gained isn’t worth the diminished quality. Each exposure variable causes a different problem when pushed too far:
- ISO: Raising ISO to increase light sensitivity comes with a corresponding increase in noise that muddies detail. The noise at any particular ISO varies greatly with the camera, so it’s essential to know your camera’s low-light capability(!). Some of the noise can be cleaned up with noise reduction software (I use Topaz DeNoise 6)—the amount that cleans up will depend on the noise reduction software you use, your skill using that software, and where the noise is (is it marring empty voids or spoiling essential detail?).
- Shutter speed: The longer the shutter stays open, the more motion blur spreads the stars’ distinct pinpoints into streaks. I’m not a big fan of formulas that dictate star photography shutter speeds because I find them arbitrary and inflexible, and they fail to account for the fact that the amount of apparent stellar motion varies with the direction you’re composing (you’ll get less motion the closer to the north or south poles you’re aimed). My general shutter-speed rule of thumb is 30-seconds or less, preferably less—I won’t exceed 30 seconds, and do everything I can to get enough light with a faster shutter speed.
- F-stop: At their widest apertures, lenses tend to lose sharpness (especially on the edges) and display optical flaws like comatic aberration (also called coma) that distorts points of light (like stars) into comet shaped blurs. For many lenses, stopping down even one stop from wide open significantly improves image quality.
Again: My approach to metering for the Milky Way is to give my scene as much light as I can without pushing the exposure compromises to a point I can’t live with. Where exactly is that point? Not only does that question require a subjective answer that varies with each camera body, lens, and scene, as technology improves, I’m less forgiving of exposure compromises than I once was. For example, when I started photographing the Milky Way with my Canon 1DS Mark III, the Milky Way scenes I could shoot were limited because my fastest wide lens was f/4 and I got too much noise when I pushed my ISO beyond 1600. This forced me compromise by shooting wide open with a 30-second shutter speed to achieve even marginal results. In fact, given these limitations, despite trying to photograph the Milky Way from many locations, when I started the only Milky Way foreground that worked well enough was Kilauea Caldera, because it was its own light source (an erupting volcano).
Today (mid-2019) I photograph the Milky Way with a Sony a7S II and a Sony 24mm f/1.4 lens. I get much cleaner images from my Sony at ISO 6400 than got a ISO 1600 on my Canon 1DSIII, and the night light gathering capability of an f/1.4 lens revelatory. At ISO 6400 (or higher) I can stop down slightly to eliminate lens aberrations (though I don’t seem to need to with the Sony lens), drop my shutter speed to 20 or 15 seconds to reduce star motion 33-50 percent, and still get usable foreground detail by starlight.
I can’t emphasize enough how important it is to know your camera’s and lens’s capabilities in low light, and how for you’re comfortable pushing the ISO and f-stop. For each of the night photography equipment combos I’ve used, I’ve established a general exposure upper threshold, rule-of-thumb compromise points for each exposure setting that I won’t exceed until I’ve reached the compromise threshold of the other exposure settings. For example, with my Sony a7SII/24mm f/1.4 combo, I usually start at ISO 6400, f/1.4, and 20 seconds. Those settings will usually get me enough light for Milky Way color and pretty good foreground detail. But if I want more light (for example, if I’m shooting into the black pit of the Grand Canyon from the canyon rim), my first exposure compromise might be to increase to ISO 12800; if I decide I need even more light, my next compromise is to bump my shutter speed to 30 seconds. Or if I want a wider field of view than 24mm, I’ll put on my Sony 16-35 f/2.8 G lens and increase to ISO 12800 and 30 seconds.
These thresholds are guidelines rather than hard-and-fast rules, and they apply to my preferences only—your results may vary. And though I’m pretty secure with this workflow, for each Milky Way composition I try a variety of exposure combinations before moving to another composition. Not only does this give me a range of options to choose between when I’m at home and reviewing my images on a big monitor, it also gives me more insight into my camera/lens capabilities, allowing me to refine my exposure compromise threshold points.
One other option that I’ve started applying automatically is long exposure noise reduction, which delivers a noticeable reduction in noise for exposures that are several seconds and longer.
* In normal situations the Sony a7SII can handle ISO 12,800 without even breathing hard, but the long exposure time required of night photography generates a lot of heat on the sensor with a corresponding increase in noise.
It’s time to click that shutter
You’re in position with the right gear, composed, focused, and exposure values set. Before you actually click the shutter, let me remind you of a couple of things you can do to ensure the best results: First, lower that center post. A tripod center post’s inherent instability is magnified during long exposures, not just by wind, but even by nearby footsteps, the press of the shutter button, and slap of the mirror (and sometimes it seems, by ghosts). And speaking of shutter clicks, you should be using a remote cable or two-second timer to eliminate the vibration imparted when your finger presses the shutter button.
When that first Milky Way image pops up on the LCD, it’s pretty exciting. So exciting in fact that sometimes you risk being lulled into a “Wow, this isn’t as hard as I expected” complacency. Even though you think everything’s perfect, don’t forget to review your image sharpness every few frames by displaying and magnifying and image on your LCD. In theory nothing should change unless you changed it, but in practice I’ve noticed an occasional inclination for focus to shift mysteriously between shots. Whether it’s slight temperature changes or an inadvertent nudge of the focus ring as you fumble with controls in the dark, you can file periodically checking your sharpness falls under “an ounce of prevention….” Believe me, this will save a lot of angst later.
And finally, don’t forget to play with different exposure settings for each composition. Not only does this give you more options, it also gives you more insight into your camera/lens combo’s low light capabilities.
The bottom line
Though having top-of-the-line, low-light equipment helps a lot, it’s not essential. If you have a full frame mirrorless or DSLR camera that’s less than five years old, and a lens that’s f/2.8 or faster, you probably have all the equipment you need to get great the Milky Way images. Even with a cropped sensor, or an f/4 lens, you have a good chance of getting usable Milky Way images in the right circumstances. If you’ve never photographed the Milky Way before, don’t expect perfection the first time out. What you can expect is improvement each time you go out as you learn the limitations of your equipment and identify your own exposure compromise thresholds. And success or failure, at the very least you’ll have spent a magnificent night under the stars.
A Milky Way Gallery
Click an image for a closer look and slide show. Refresh the window to reorder the display. | 0.865789 | 3.694897 |
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