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Authors: Ana H. Lobo and Simona Bordoni
First Author’s Institution: California Institute of Technology
Status: Published in Icarus [closed access]
Imagine a cross between Earth and Uranus—a planet with water and high insolation (sunlight) but tilted to Uranus’ crazy 98º. No planet like that exists in our solar system today, but one might have billions of years ago. Mars’ tilt varies wildly over millions of years and it is theorized that Mars once contained global oceans. The authors of today’s paper propose the fundamental question: would an earth-like, high obliquity planet be habitable?
Look to the GCM
To answer this question, the researchers use a general circulation model (GCM). A GCM is an advanced simulation that solves the fluid equations for a planetary atmosphere. It takes into account multiple factors, such as land-air boundaries, cloud formation, seasonal variability, and atmospheric chemistry. The authors choose to model a planet like Earth but with a “slab ocean” of a universal depth of 1 meter around the whole planet instead of the Earth’s true topography. Such a configuration is called an “aquaplanet” and has the benefit of isolating the effects of obliquity on the atmosphere from other potential factors. The models were run with obliquities varying from 10º to 85º.
Hot Summers and Cold Winters
In contrast to the Earth, on a planet with greater than 54º obliquity, the poles receive more sunlight on average than the equator. This results in strong heating of the poles during the summer and rapid cooling during winter, which can be seen in Figure 1. In a 23.5º tilt planet (top panel), the mid-latitudes see mild winters and summers. However, an 85º tilt planet (bottom panel) heats up about 20 K more in the summer and cools down 20 K more in the winter. An average temperature difference of 20 K may not seem like much, yet it’s the difference between Miami in July and the North Pole.
Extreme obliquity has a profound impact on precipitation.
The heat of Earth’s equatorial region is transferred toward the poles via Hadley Cells.
Rising air near the equator brings moisture with it, keeping the equator humid.
Falling air around 30ºN and 30ºS dries out those regions, which is why most of Earth’s deserts
can be found there.
The authors notice that as they increase obliquity to 85º, the equator becomes dry instead of tropical and the higher latitudes become extremely wet. Figure 2 shows the precipitation that falls in a planet with a 23.5º tilt (left panel) compared to that of an 85º tilt planet (right panel). The tropical bands of moisture move much farther north and south for the 85º tilt, creating a monsoon-like climate in the mid-latitudes even more extreme than the climate pattern in Southeast Asia, for example.
The middle panel shows annual mean precipitation (solid lines) and evaporation (dashed lines). The difference determines the atmospheric moisture. The average patterns on a 23.5º planet are nearly reversed on an 85º planet, causing desertification of the equatorial region and shifts in moisture. The principal reason for this precipitation pattern is changes in the atmospheric storage capacity.
Three primary factors contribute to atmospheric moisture. (1) Mean moisture flux is the transport of water vapor by converging winds. For example, on Earth, the winds between 30º N and 30º S (from the Hadley Cells) blow toward the equator, pushing water vapor in the same direction. (2) Eddy transport is due to local winds. (3) Water vapor storage is the amount of water that can be held in the air without condensing out into clouds or rain and generally increases with temperature.
Figure 3 compares these three factors. For a 23.5º tilt planet (left panels), most of the net precipitation is caused by mean moisture flux near the equator. In contrast, the 85º planet (right panels) has intense precipitation due to the changes in storage capacity. This difference fits to what was shown in Figure 1: high obliquity planets have much more extreme temperature swings. When the 85º planet heats up in the northern summer, its storage capacity goes way up and the atmosphere fills with water. But winter on that planet comes on quickly, unlike the gradual seasons on Earth, and the sudden temperature drop plummets the atmospheric storage capacity, causing all that water to precipitate out.
These variations add up to substantially different moisture control systems on planets with different obliquities.
So…is it Habitable?
Though high obliquity planets with global monsoon seasons and temperature extremes may not seem like home to us, the authors of today’s paper have shown that some regions might still be habitable. It just would be in different places than on Earth. Running a more realistic model with deep oceans instead of an aquaplanet would likely improve habitability because water dampens temperature extremes. In the never-ending search for extraterrestrial life, exoplanet astronomers should not rule out extremely tilted planets.
Cover Image: Tech Insider | 0.85393 | 3.865067 |
Understanding the make-up and dynamics of atmospheric clouds is crucial to our interpretations of how weather and climate behave on Earth, and so it should come as no surprise that clouds are similarly essential to learning the nature and behavior of exoplanets.
On many exoplanets, thick clouds and related, though different, hazes have been impediments to learning what lies in the atmospheres and on surfaces below. Current technologies simply can’t pierce many of these coverings, and scientists have struggled to find new approaches to the problem.
One class of exoplanets that has been a focus of cloud studies has been, perhaps unexpectedly, hot Jupiters — those massive and initially most surprising gas balls that orbit very close to their suns.
Because of their size and locations, the first exoplanets detected were hot Jupiters. But later work by astronomers, and especially the Kepler Space Telescope, has established that they are not especially common in the cosmos.
Due to their locations close to suns, however, they have been useful targets of study as the exoplanet community moves from largely detecting new objects to trying to characterize them, to understanding their basic features. And clouds are a pathway to that characterization.
For some time now, scientists have understood that the night sides of the tidally-locked hot Jupiters generally do have clouds, as do the transition zones between day and night. But more recently, some clouds on the super-hot day sides — where temperatures can reach 2400 degrees Fahrenheit –have been identified as well.
Vivien Parmentier, a Sagan Fellow at the University of Arizona, Tucson, as well as planetary scientist Jonathan Fortney of the University of California at Santa Cruz have been studying those day side hot Jupiter clouds to see what they might be made of, and how and why they behave as they do.
“Cloud composition changes with planet temperature,” said Parmentier, who used a 3D General Circulation Model (GCM) to track where clouds form in hot Jupiter atmospheres, and what impact they have on the light emitted and reflected by the planets. “The offsetting light curves tell the tale of cloud composition. It’s super interesting, because cloud composition is very hard to get otherwise.”… Read more | 0.902391 | 3.899112 |
Fr.: binaire à une seule raie
A → spectroscopic binary in which only one set of → spectral lines is detectable. The binary nature of the system is deduced from the fact that the spectral lines exhibit periodic → Doppler shifts due to orbital motions in the system. Same as → SB1 binary. See also: → double-lined binary.
Fr.: binaire mou
In → stellar dynamics studies of → three-body encounters, a → binary system whose → binding energy is smaller than the typical → kinetic energy of the relative motion of an incoming third body. See also → hard binary.
Fr.: binaire spectroscopique
A binary system that cannot be resolved by a telescope, but can be identified by means of the Doppler shift of the spectral lines. As stars revolve, they alternately approach and recede in the line of sight. This motion is shown up in their spectra as a periodic oscillation or doubling of spectral lines.
Fr.: binaire visuelle
A → binary system of stars whose components can be resolved telescopically and which have detectable orbital motion.
Fr.: binaire écarté
A binary system with semi-major axis as large as 10,000 → astronomical units.
dorin-e partow-e iks
Fr.: binaire X
A binary star system where one of the stars has evolved and collapsed into an extremely dense body such as a → white dwarf, a → neutron star, or a → black hole. The enormous gravitational attraction of the massive, dense, but dim component pulls material from the brighter, less massive star in an → accretion disk. The gravitational potential energy of the accreted matter is converted to heat by → viscosity and eventually to high-energy photons in the X-ray range. The brightest X-ray binary is → Scorpius X-1. | 0.808636 | 3.488161 |
One of the big ticket astronomical events of 2014 will be the close passage of Comet C/2013 A1 Siding Spring past the planet Mars in October 2014. Discovered just over a year ago from the Australian-based Siding Spring Observatory, this comet generated a surge of excitement in the astronomical community when it was discovered that it was going to pass very close to the planet Mars in late 2014.
Now, a fleet of spacecraft are poised to study the comet in unprecedented detail. Some of the first space-based observations of the comet have been conducted by NASA’s Hubble Space Telescope and the recently reactivated NEOWISE mission. And although the comet may not look like much yet in the infrared eyes of NEOWISE, its estimated 4 kilometre in diameter nucleus is already active and shedding about 100 kilograms of dust per second.
And although an impact has been since ruled out, it’s that dust that may present a hazard for Mars orbiting spacecraft, as well as a unique scientific observing opportunity.
“Our plans for using spacecraft at Mars to observe Comet A1 Siding Spring will be coordinated with plans for how the orbiters will duck and cover, if we need to do so that,” said NASA/JPL Mars Exploration Program chief scientist Rich Zurek.
Comet A1 Siding Spring is projected to pass within just 138,000 kilometres of Mars on October 19th, 2014. This is one-third the Earth-Moon distance, and 10 times closer than the closest recorded passage of a comet by the Earth, which was Comet D/1770 Lexell in the late 18th century. The comet will also miss the Martian moons of Phobos and Deimos, which have the closest orbits of any moons in the solar system at just 5,989 and 20,063 kilometres above the surface of Mars, respectively.
Assets in orbit around the Red Planet are also slated to observe the close approach and passage of Comet A1 Siding Spring, as well as any extraterrestrial meteor shower that its dust may generate.
“We could learn about the nucleus – its shape, its rotation, whether some areas on its surface are darker than others,” Zurek said in a recent NASA/JPL press release.
The rovers Curiosity and Opportunity are currently active on the surface of Mars. Above in orbit, we’ve got the European Space Agency’s Mars Express, and NASA’s Mars Odyssey and the Mars Reconnaissance Orbiter (MRO). These will be joined by India’s Mars Orbiter Mission and NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft just weeks prior to the comet’s passage.
“A third aspect for investigation could be what effect the infalling particles have on the upper atmosphere of Mars,” Zurek said. “They might heat it and expand it, not unlike the effect of a global dust storm.”
Just last year, Mars based spacecraft caught sight of the ill-fated sungrazer Comet C/2012 S1 ISON as it passed Mars. But that dim passage yielded a scant pixel-sized view in the eyes of MRO’s HiRISE camera; Comet A1 Siding Spring will pass 80 times closer than Comet ISON and could yield a view of its nucleus dozens of pixels across.
Though the tenuous Martian atmosphere will shield to surface rovers from any micro-meteoroid impacts, they may also be witness to a surreptitious meteor shower from the debris shed by the comet, a first seen from the surface of another world.
But engineers will also be assessing the potential hazards that said particles may posed to spacecraft orbiting Mars as well.
“It’s way too early for us to know how much of a threat Siding Spring will be to our orbiters,” said JPL’s Mars Exploration Program chief engineer Soren Madsen recently. “It could go either way. It could be a huge deal or it could be nothing – or anything in between.”
In a worst case scenario, Mars orbiting spacecraft would be shuttered and oriented to “shelter in place” as the dust from the comet passes. There’s precedent for this in Earth orbit, as precious assets such as the Hubble Space Telescope were closed for business during the Leonid meteor storm of 1998.
“How active will Siding Spring be in April and May? We’ll be watching that,” Madsen continued. “But if the red alarm starts sounding in May, it would be too late to start planning how to respond. That’s why we’re doing what we’re doing right now.”
Comet A1 Siding Spring was the first comet discovered in 2013 at 7.2 Astronomical Units (AUs) distant. From our Earth based perspective, the comet will reach opposition on August 25th at 0.96 AU from the Earth, and approach 7’ from Mars on October 19th in the constellation Ophiuchus in evening skies. The comet reaches perihelion just 4 days later, and is slated to be a binocular comet around that time shining at magnitude +8.
The comet nucleus itself is moving in a retrograde orbit relative to Mars. Particles from A1 Siding Spring will slam into the atmosphere of Mars — and any spacecraft that happens to be in their way — at a velocity of 56 kilometres per second. For context, the recent January Quadrantids have a more sedate atmospheric impact velocity of 41 kilometres a second.
The unfolding 2014 drama of “Mars versus the Comet” will definitely be worth keeping an eye on… more to come! | 0.858361 | 3.806814 |
It took less than two billion years for our Milky Way Galaxy to emerge from the chaos of the Hot Big Bang some 13.8 billion years ago. Another 7 billion years would elapse before our Sun and Solar System took form. During this time, the thermonuclear processing of matter in the cores of stars and during the violent deaths of massive stars collectively forged the heavy elements that characterize our rocky home planet.
On Earth’s moist surface, microbial life took hold less than a billion years after the Sun turned on. Yet another three billion years would have to pass, before multi-cellular life forms began to leave fossil records in the accumulating sediments of sand, mud, and limestone. The remaining 500 million years up to the present day have witnessed the successive flourishing of primitive sea animals, land animals, flowering plants, dinosaurs, mammals, and – in the last two million years – humans.
Timeline of Earth’s history, including the origin of microbial life 3.8 billion years ago and the evolution of multi-cellular life forms to the present day. Courtesy of Andree Valley (see http://www.geology.wisc.edu/zircon/Earliest%20Piece/Earliest.html ).
Homo sapiens began creating their distinctive and enduring stone tools, middens, and burials about 100,000 years ago. Only in the last century (1/1000 the history of modern humans and 1/ 50-million the history of Earth) have we begun to telecommunicate beyond Earth. Using radio and television transmitters, we have become inadvertent players on the galactic stage. Already, our broadcasts have faintly traveled past thousands of stars and their associated planetary systems.
We have also begun the search for distinctive electromagnetic signals from technologically communicative life forms beyond Earth. What those species may be and what sort of signals that they may be sending out remain highly challenging questions. Once the exclusive province of science fiction authors, the topic of Interstellar Communications has come into its own as a scientific and technological field worthy of deliberate investigation.
The following journals currently host peer-reviewed technical articles on the Search for Extraterrestrial Intelligence (SETI) and the even more provocative topic of Communications with Extraterrestrial Intelligence (CETI).
Acta Astronautica (Amsterdam: Elsevier Publications)
Astrobiology (New Rochelle, NY: Mary Ann Liebert Inc., Publications)
International Journal of Astrobiology (Cambridge, UK: Cambridge University Press)
CALL FOR CONTRIBUTIONS:
One of the key missions of The Galactic Inquirer is to bridge the gap between the rigorous researcher and the curious public. Towards these ends, the editors of The Galactic Inquirer welcome publicly-accessible communications that help to illuminate the topics of Interstellar Communications. We seek non-technical articles, commentaries, book reviews, profiles, and photo-essays that are well-crafted and engaging.
Submissions should be in Word 97-2003 (.doc) or later formats (.docx), and should contain from 500 to 2000 words. The latter requirement is to ensure that The Galactic Inquirer is much more than an aggregator of word “bites.” All photos and figures should include captions, credits, and associated permissions. Any references at the end of a contribution should help the general-interest reader make greater sense of the subject at hand. Articles in Scientific American and American Scientist can provide a helpful template for formatting your submission.
You can contact us using the Contact form available in the main menu. All submissions should be e-mailed to us here . They should include the names and e-mail addresses of all authors along with a picture of the author(s). The author(s) should state their status as a student or professional as part of a 1-3 sentence biography.
All contributions will be vetted for appropriate content and edited for clarity. All contributions that are published in The Galactic Inquirer are the property of the author(s) and The Galactic Inquirer. Therefore, subsequent use of published contributions must follow “fair use” guidelines, including written permission from the author(s) and explicit attribution to the author(s) and The Galactic Inquirer. | 0.815034 | 3.215366 |
When you look into the night's sky, you'd expect to see stars, the moon, an occasional meteor and, if you're lucky, rippling curtains of light created by the impact of the sun's energetic particles raining through our atmosphere. If you're really lucky, you also might see Steve.
Steve is a newly identified and mysterious space weather phenomenon that — with the help of social media, a dedicated team of citizen scientists and a European fleet of satellites — may finally get the recognition it deserves.
The streak in the sky came to the attention of researcher Eric Donovan, who works at the University of Calgary, Canada, after chatting with members of the Alberta Aurora Chasers, a group of enthusiasts who observe and photograph the aurora borealis (also known as the northern lights). By turning to social media, dozens of other observer reports were collected, meaning that Steve actually was well-known.
The phenomenon got its name from the 2006 animated movie "Over the Hedge" in which the characters name a talking hedge "Steve" to make it less scary.
But what's so peculiar is that there's no clear explanation as to what Steve really is. Yet.
Appearing as a long and beautiful purple ribbon of light in the sky during periods of auroral activity, it was originally thought to be an aurora itself. Auroras are generated when particles from the sun, mainly electrons, interact with the gases in our atmosphere.
To the naked eye, most auroras will appear green — that's the color oxygen glows when hit by these particles. But Steve looks and behaves very differently.
In the past, sightings of "Steve" have been attributed to "proton arcs." These auroras occur when solar wind protons (not electrons) precipitate through the atmosphere. But there's a problem with this explanation: Proton auroras generate mainly UV light, radiation that isn't visible to the naked eye. Also, if they were to generate any visible light, the light would be very diffuse. Steve is obviously a very different beast as it generates a very visible purplish hue.
To research this mystery further, Donovan turned to space for help.
The European Space Agency currently has a trio of satellites called Swarm flying in formation over Earth's poles. They're charged with monitoring Earth's magnetic field. A bit like a Fitbit can monitor your physical activity levels, Swarm can precisely monitor fluctuations in the magnetism surrounding our planet.
In this age of ultra-responsive social media, Donovan used the Aurorasaurus website to track eyewitness accounts of auroras around the globe and collate these accounts with all-sky cameras in the Northern Hemisphere. All-sky cameras are excellent tools to monitor the whole night's sky with their 360-degree field of view.
With all this data in hand, Donovan found a sighting of Steve at just the right time — the Swarm satellites had made an orbital pass directly overhead, and they were recording the conditions of the magnetic field and atmosphere below.
"The temperature 300 kilometers above Earth's surface jumped by 3000-degrees Celsius and the data revealed a 25-kilometer-wide ribbon of gas flowing westwards at about 6 kilometers per second (over 13,000 miles per hour) compared to a speed of about 10 meters per second (200 miles per hour) either side of the ribbon," said Donovan in an ESA news release.
In other words, Steve is made from very hot and speedy gas.
"It turns out that Steve is actually remarkably common, but we hadn't noticed it before. It's thanks to ground-based observations, satellites, today's explosion of access to data and an army of citizen scientists joining forces to document it," he added. "Swarm allows us to measure it and I'm sure will continue to help resolve some unanswered questions."
That's handy because the sun and Earth have a magnetic relationship. Eruptions in the solar atmosphere can have dramatic effects on the environment surrounding our planet, creating geomagnetic storms, triggering auroras and driving global electric currents. So far, it's not clear how Steve fits into this relationship, but through efforts by enthusiasts, scientists and satellites, we may soon find out what triggers this mysterious yet surprisingly common sight in our atmosphere.
"It is amazing how a beautiful natural phenomenon, seen by observant citizens, can trigger scientists' curiosity," added ESA Swarm mission scientist Roger Haagmans. | 0.800256 | 3.922485 |
Peter Becker More Content Now
Ever wave to the astronauts?
Anyone born from 1957 on, has lived their entire lives in the Space Age. Spaceships passing overhead are literally commonplace.
Most are unmanned. Thousands of satellites sent into Earth orbit pass over every day and night. You don’t have to watch long on the next starry night, to see one. They look like a star, except that they are moving must faster than the stars appear to shift, and usually they are traveling west to east, northwest to southeast, southwest to northeast, or north to south or south to north. The stars, however, seem to be moving east to west.
Seeing a manned spacecraft is especially interesting.
These days this is limited to the most enormous manmade satellite (in contrast to our lone, natural satellite, the Moon) — the International Space Station (ISS).
NASA has a website to inform you in advance when the ISS is passing over your area of the planet at a time you can see it, and where in the sky to look.
Log on to: https://spotthestation.nasa.gov/.
Just enter your city or town and follow the simple steps that follow.
You can even receive a “Heads Up” from NASA if you request to be alerted by an email or text about the next passage of the Space Station.
The ISS is very bright, brighter than an star in the night sky especially when it is overhead (and therefore closest to you). If the station is seen not far from the horizon, it is not quite as bright but still easily visible.
Watch as the station passes into the shadow of the Earth. In the evening, you can track the station until a certain point where it quickly fades from view, somewhere opposite from where the Sun set.
The view from on board must be fantastic. You can see pictures and videos online, of what the astronauts witness when they have opportunity to look out their windows.
If their eyes are adjusted to the darkness they will be able to see the canopy of stars in the sky of space, like never available from the surface of the Earth under our blanket of air. The dark side of the Earth, where clouds are not over land masses, will show what may seem like more “stars” — only these are constellations of towns and cities, lit by clusters of streetlights and other sources. Oceans of course would be black. If the Moon is shining, however, they could see its illumination and reflection off the waters of this great blue world.
Satellites other than the Space Station hold their own fascination. You may see a few that fade and brighten on a regular cycle as it passes over. This may be tumbling rocket stage, varying in how much sunlight it is reflecting back.
Through a telescope, you will see many more satellites, far too dim to catch with eyes alone. They seem to travel extremely fast, when spotted under magnification of a telescope eyepiece; try following it as it zooms past the stars.
One night I was able to catch ISS in the telescope. I could actually discern some of its shape, including its solar panels, as it rushed along.
Even more common, however, are jet airliners, if you like under ant flight paths. Earth satellites shine with a steady, white light. Airliners have three lights, amber, white and red. A few seconds after seeing one, you may hear the engine’s roar. Be sure to wave at them as well. Someone is likely looking down and seeing the lights of YOUR town and wondering who lives there.
Last quarter Moon is on Oct. 12.
Keep looking up.
— Peter Becker is Managing Editor at The News Eagle in Hawley, Pennsylvania. Notes are welcome at [email protected]. Please mention in what newspaper or web site you read this column.
Looking Up: Waving at the Space Station
Peter Becker More Content Now | 0.823533 | 3.361289 |
Interstellar visitor reveals its icy secrets
The first confirmed comet from another planetary system arrived last year. Astronomers scrambled to take advantage of this fleeting opportunity. Using the ALMA radio telescope, we captured molecular emission from 2I/Borisov, revealing an unusual chemical composition for this interstellar object.
The surprise apparition of two interstellar objects (ISOs) in the last three years is transforming the science of small Solar System bodies. 1I/'Oumuamua and 2I/Borisov arrived in our inner Solar System in September 2017 and December 2019, respectively, delivering to our doorstep an unprecedented opportunity to investigate the physical and chemical properties of a new and truly alien class of object, leading to a paradigm-shift in our ability to study in detail the properties of distant planetary systems.
Interstellar comet 2I/Borisov was first discovered by amateur astronomer G. Borisov on August 30th 2019, more than three months before perihelion. Subsequent observations over the following days confirmed a strongly hyperbolic orbit, and the presence of a clear, extended gas/dust coma, allowing 2I/Borisov to be unequivocally categorized as an interstellar comet (originating in the direction of Cassiopeia, with an inbound heliocentric velocity of 33 km/s).
But 2I/Borisov was faint. It reached a visual magnitude of only 16, with a relatively large perihelion distance of 2 au, which made it a very challenging target for spectroscopic observations. The most powerful telescopes in the world (and in orbit) were called into action. Initial reports from optical observations of CN and atomic oxygen fluorescence showed close similarities with normal Solar System comets, but the information that could be gleaned from those gases, regarding the interstellar comet's intrinsic composition, was limited.
Our team (led by myself and Stefanie Milam at NASA Goddard Space Flight Center) obtained two sets of observations of 2I/Borisov in 2019 using the Atacama Large Millimeter/submillimeter Array (ALMA): the first set was in late September using the (7 m) Atacama Compact Array, and the second was in mid-December using the main (12 m) ALMA array. Reliable detections of molecular emission were only obtained from the (more sensitive), second set of observations, which also benefitted from the comet being closer to the Sun, and thus, more active. Our ALMA images of HCN and CO emission in the 0.9 mm wave band are shown in the following figure:
Full details of these observations are given in our published Nature Astronomy article. While exhilarating to detect any "native volatiles" (gases stored as ices inside the nucleus) of the first interstellar comet, it was the detection of carbon monoxide (CO) that really got us excited. We have looked for CO in seven of the previous Solar System comets targeted with ALMA, but never once detected it until now. It seemed impossible that CO would be found in such a faint comet as 2I/Borisov, but its signal was clear and unambiguous, alerting us to the idea that this interstellar voyager might have a distinctly different chemical composition to that of our own Solar System comets.
Our derived molecular production rates confirmed an unusually large CO abundance with respect to both HCN and H2O - higher than observed before in any comet within 2 au of the Sun. The heliocentric distance is important since beyond about 2.5 au, comets can be significantly less active, with reduced H2O sublimation, and their comae tend to be more enriched in the most volatile gases such as CO. Among all comets previously observed in our Solar System, only one - the chemically peculiar comet C/2017 R2 (PAnSTARRS) - had a higher CO/HCN mixing ratio.
2I/Borisov's extremely high CO/HCN ratio with respect to Solar System comets is highlighted in the following figure from our published article:
2I/Borisov has many characteristics in common with our own Solar System comets, suggesting a commonality in the basic physical and chemical conditions occurring during planet formation around other stars in our Galaxy. However, the remarkable, elevated CO abundance shows that key details regarding its formation must have been different. Given the importance of CO as the basis for the formation of more complex organic molecules in the solid phase in protoplanetary disks and star-forming regions, we may therefore expect differences is the inventory of possible prebiotic molecules, between different planetary systems.
Based on a single data point, we cannot know the extent to which 2I/Borisov may be representative of the broader population of interstellar comets, but statistically, it is probable that the first confirmed interstellar comet should provide a template for future ISOs. Although the frequency of ISO apparitions bright enough for compositional studies is not currently well-constrained, more interstellar comets are expected to pass through the inner Solar System in the coming years. We should be prepared for surprises when the next opportunity to observe one arises. | 0.900667 | 4.072855 |
Astronomers have precisely measured the strength of a fundamental force of Nature in a galaxy seen eight billion years in the past.
Researchers from Swinburne University of Technology and the University of Cambridge have confirmed that electromagnetism in a distant galaxy has the same strength as here on Earth.
They observed a quasar — a supermassive black hole with enormously bright surroundings — located behind the galaxy. On its journey toward Earth, some of the quasar’s light was absorbed by gas in the galaxy eight billion years ago, casting shadows at very specific colours.
“The pattern of colours tells us how strong electromagnetism is in this galaxy, and because the quasar is one of the brightest ones known, we were able to make the most precise measurement so far,” says lead author of the study, Swinburne PhD candidate Srđan Kotuš.
“We found electromagnetism in this galaxy was the same as here on Earth within just one part per million — about the width of a human hair compared to the size of a sports stadium.”
Electromagnetism is one of the four known fundamental forces of Nature.
“Electromagnetism determines almost everything about our everyday world, like the light we receive from the Sun, how we see that light, how sound travels through the air, the size of atoms and how they interact,” says Swinburne’s Professor Michael Murphy, co-author of the new work.
“But no one knows why electromagnetism has the strength it has and whether it should be constant, or vary, and why.”
Most previous attempts to measure electromagnetism have been limited by instruments called spectrographs — the ‘light rulers’ used to measure the pattern of shadows in the quasar’s rainbow of colours. The researchers used spectrographs at the European Southern Observatory’s Very Large Telescope (VLT) and 3.6-m Telescope in Chile to make their observations.
“The VLT’s spectrograph is a little inaccurate: it’s a high-quality ruler for measuring light, but the numbers on that ruler are a little offset. So, to make the best measurement, we also used the 3.6-m Telescope’s spectrograph to provide very accurate numbers,” says Mr Kotuš.
“For me, finding that electromagnetism is constant over more than half the Universe’s age just deepens the mystery — why is it that way? We still don’t know,” Professor Murphy says.
“It’s remarkable that distant galaxies provide such a precise probe of such a fundamental question. With even larger telescopes now being built, we’ll be able to test it even better in the near future.”
The research has been published in the Monthly Notices of the Royal Astronomical Society.
Source: Science Daily | 0.833681 | 4.022489 |
Nine months after capturing its first images from atop Maunakea in Hawaii, the scientific instrument SPIRou (SpectroPolarimètre InfraRouge) got the green light to begin its first scientific observation campaign at the Canada-France-Hawaii Telescope (CFHT). The instrument was delivered at the CFHT in January 2018 and has since undergone a battery of performance tests to ensure it will be able to achieve the international SPIRou team’s scientific goals.
The idea behind SPIRou
SPIRou was first conceptualized in 2010. At that time, the Kepler Space Telescope had already begun its observing campaign and was detecting a surprising number of exoplanet candidates using the transit method. This method does not, however, allow the measurement of a number of important characteristics of the detected exoplanet, such as its mass, or of its host star. Researchers from France, Canada, Brazil, Taiwan, Switzerland, and Portugal thus decided to build an instrument together that would provide this missing information in follow-up studies of Kepler exoplanets and allow us to answer important questions such as “Where are the closest habitable worlds?” and “How do the magnetic fields of stars affect planet formation?”.
SPIRou, a high-resolution infrared spectropolarimeter and a high-precision velocimeter, was designed to detect the tiny motion of stars due to the presence of one or more Earth-like exoplanets orbiting them, and to study the magnetic fields of stellar systems. Lead by Principal Investigator Jean-François Donati (Université de Toulouse, IRAP) and co-PI René Doyon, this instrument will be particularity effective in finding and characterising exoplanets that have a size similar to Earth orbiting red dwarfs, stars that are colder and less massive than our Sun and that are very common in our solar neighbourhood. It will not only be able to perform follow-up observations of Kepler candidates, but will also become a workhorse instrument to measure the mass of new nearby transiting exoplanets soon to be discovered by the NASA Transiting Exoplanet Survey Satellite (TESS) mission. These planets will be prime candidates to have their atmospheres detected and characterised by the James Webb Space Telescope (JWST).
A strong instrumentation team in Québec
Building off their strong expertise in instrumentation, the astronomy research group at the Université de Montréal and the optical engineering group at the Université Laval were uniquely positioned to help with the construction of SPIRou. Both universities have a long history of developing astronomical instruments which has lead to the creation of the Laboratoire d’astrophysique expérimentale at the Observatoire du Mont-Mégantic which they own jointly.
Université Laval professor and iREx associate member Simon Thibault and his team contributed heavily to the optical design of SPIRou’s spectrograph and science camera. The team also worked on the optomechanical integration of SPIRou’s camera which required a micro-level accuracy for the centring of the lenses. Prof. Thibault, who is an NSERC Industrial Research Chair and the Director of the Optical Engineering Research Laboratory in Quebec has overseen the development of many advanced optical systems. Through international collaborations, he is very involved in the design and development of major astronomical instruments for the next generation of astronomical telescopes.
The Université de Montréal team, lead by iREx Director and SPIRou Co-PI Prof. René Doyon, lead the efforts for the design and development of SPIRou’s spectrograph camera and infrared detector and contributed to a number of the project’s other components. The lead Project Scientists are iREx’s Étienne Artigau and Xavier Delfosse from the Institut of planétologie et d’astrophysique de Grenoble in France. The project has also, until recently, been expertly managed by Olivier Hernandez, one of iREx’s founding members and now the Director of the Rio Tinto Alcan Planetarium of Montreal.
In order to observe cooler red dwarf stars, SPIRou’s instruments have to operate in the infrared, and the UdeM/ULaval team has accumulated impressive amounts of experience in this field working on other infrared instruments such as JWST’s NIRISS, CFHT’s WIRCAM and Gemini-South’s GPI.
Putting it to the test
For the last year, SPIRou has been submitted to strict testing by the project team to measure its performance on important observation parameters, including its radial velocity precision. Acceptance tests and a review panel have confirmed that the instrument is ready for scientific operations, and it has been green lit to begin its ambitious science campaign in mid-February.
iREx members Étienne Artigau and Neil Cook were especially crucial in reaching the current precision threshold in radial velocity of 2 m/s, among the best ever achieved in the infrared for this kind of complex instrument. The SPIRou team is very confident that improvement in the data reduction pipeline and the correction for spectral lines due to the Earth’s atmosphere will improve SPIRou’s performance near the initial goal of a precision of 1 m/s. These small velocities, equivalent to the average walking speed of a human on Earth, are the level of precision needed to detect the wobble of red dwarfs caused by an Earth-like planet orbiting them.
Fifty nights have already been scheduled for semester 2019A for the SPIRou Legacy Survey which will seek to answer SPIRou’s biggest science questions, and 300 nights have been allocated towards this program over the next four years. Many high-profile targets will be observed by SPIRou soon, including the famous TRAPPIST-1 system which contains seven Earth-sized rocky planets orbiting a dwarf star approximately 40 light-years away. The exoplanets studied by SPIRou will likely be ideal candidates for the upcoming JWST mission which will use transit spectroscopy to characterise the atmospheres of exoplanets and determine their habitability.
SPIRou was designed, funded and constructed thanks to a worldwide consortium of institutes, namely, IRAP (CNRS/UPS), Services communs de l’Observatoire Midi-Pyrénées (CNRS/UPS/IRD/CNES/MétéoFrance), Observatoire de Haute-Provence, Institut de planétologie et d’astrophysique de Grenoble (CNRS/Université Grenoble Alpes), Laboratoire d’astrophysique de Marseille (CNRS/CNES/AIx-Marseille Université), Institut d’Astrophysique de Paris (CNRS/Sorbonne Université) in France; the NRC’s Herzberg Astronomy and Astrophysics Research Centre, Centre for Optics, Photonics and Lasers at Université Laval, Observatoire du Mont-Mégantic and Université de Montréal in Canada; Academia Sinica Institute of Astronomy and Astrophysics in Taiwan; Observatoire de Genève in Switzerland; Laboratório Nacional de Astrofísica in Brazil; Centro de Astrofísica da Universidade do Porto in Portugal and of course the Canada-France-Hawaii Telescope.
Research Associate, Optical Engineering Research Laboratory
Tél: 418-656-2131, poste 404646
CNRS Research Director
Université de Toulouse, IRAP
NSERC Industrial Research Chair
Director, Optical Engineering Research Laboratory
Professor, Université Laval
SPIRou on the iREx website | 0.871984 | 3.68439 |
Massive star cluster in our backyard - astronomically speaking!
A team of European astronomers, including several from the UK, have uncovered a super star cluster in our own Galaxy, the Milky Way. This particular cluster, known as Westerlund 1, is a unique natural laboratory for the study of extreme stellar physics, helping astronomers to find out how the most massive stars in our Galaxy live and die.
Super star clusters are groups of hundreds of thousands of very young stars packed into an unbelievably small volume. Until now, super star clusters were known to exist very far away, mostly in pairs or groups of interacting galaxies.
Image: A composite image of the super star cluster "Westerlund 1" from 2.2-m MPG/ESO Wide-Field Imager (WFI) observations. The image covers a 5 x 5 arcmin sky region and is based on observations made in the V-band (550 nm, 2 min exposure time, associated to the blue channel), R-band (650nm, 1 min, green channel) and I-band (784nm, 18 sec, red channel). Only the central CCD of WFI was used, as the entire cluster fits comfortably inside it. The foreground stars appear blue, while the hot massive members of the cluster look orange, and the cool massive ones come out red.
Westerland 1 was discovered in 1961 but because it is hidden behind a large cloud of dust and gas its true nature had not been revealed until now. Using the European Southern Observatory's telescopes at the La Silla Observatory in Chile the team were able to penetrate beyond the dust and gas to the extent that they could distinguish individual stars within the super star cluster. Westerlund 1 is a thousand times closer than any other super star cluster known so far. It is close enough that astronomers may now probe its structure in some detail.
Westerlund 1 contains hundreds of very massive stars, some shining with a brilliance of almost one million suns and some two thousand times larger than the Sun (as large as the orbit of Saturn). Indeed if the Sun were located at the heart of this remarkable cluster, our sky would be full of hundreds of stars as bright as the full Moon.
From their observations, astronomers conclude that this extreme cluster most probably contains no less than 100,000 times the mass of the Sun, and all of its stars are contained in a region less than 6 light years across. Westerlund 1 appears to be the most massive compact young cluster yet identified in the Milky Way.
All the stars so far analysed in Westerlund 1 weigh at least 30-40 times more than the Sun. because stars have such a rather short life span - astronomically speaking Westerlund 1 must be very young. Astronomers determine an age lying between 3.5 and 5 million years. So Westerlund is a "newborn" cluster within our galaxy.
The large number of very massive stars implies that Westerlund 1 must contain a huge number of stars. Simon Clark, from University College London, one of the astronomers involved in this study explains, "In our Galaxy there are more than 100 solar like stars for every star weighing 10 times as much as the Sun. The fact that we see hundreds of massive stars in Westerlund 1 means that it probably contains close to a half a million stars, but most of them are not bright enough to peer through the obscuring cloud of dust and gas." This is 10 times more any other known Milky Way cluster.
A further surprise awaiting Clark and his colleagues was that these stars are packed into an amazingly small volume of space, less than 6 light years across.
"With so many stars in such a small volume, some of them collide", says Clark. This could lead to the formation of an intermediate black hole more massive than 100 solar masses. It may well be that such a monster has already formed at the core of Westerlund 1."
The cluster contains so many massive stars that in a time span of less than 40 million years, it will be the site of more than 1,500 supernovae - resulting in a giant firework display!
Further studies using high resolution cameras on the European Southern Observatory's Very Large Telescope will reveal more about this super star cluster. Westerlund 1 will certainly provide new opportunities in the long standing quest for more and finer detail about how stars, especially massive ones, do form. | 0.862858 | 3.728269 |
Gibbous ♊ Gemini
Moon phase on 9 February 2052 Friday is Waxing Gibbous, 9 days young Moon is in Gemini.Share this page: twitter facebook linkedin
Previous main lunar phase is the First Quarter before 1 day on 7 February 2052 at 17:35.
Moon rises in the afternoon and sets after midnight to early morning. It is visible to the southeast in early evening and it is up for most of the night.
Moon is passing about ∠13° of ♊ Gemini tropical zodiac sector.
Lunar disc appears visually 0.7% wider than solar disc. Moon and Sun apparent angular diameters are ∠1959" and ∠1945".
Next Full Moon is the Snow Moon of February 2052 after 5 days on 14 February 2052 at 18:21.
There is medium ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at very acute angle, so their combined tidal force is moderate.
The Moon is 9 days young. Earth's natural satellite is moving from the first to the middle part of current synodic month. This is lunation 644 of Meeus index or 1597 from Brown series.
Length of current 644 lunation is 29 days, 13 hours and 6 minutes. It is 2 hours and 15 minutes longer than next lunation 645 length.
Length of current synodic month is 22 minutes longer than the mean length of synodic month, but it is still 6 hours and 41 minutes shorter, compared to 21st century longest.
This lunation true anomaly is ∠285.5°. At the beginning of next synodic month true anomaly will be ∠314.8°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
2 days after point of perigee on 6 February 2052 at 18:01 in ♈ Aries. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 11 days, until it get to the point of next apogee on 21 February 2052 at 10:01 in ♏ Scorpio.
Moon is 365 871 km (227 342 mi) away from Earth on this date. Moon moves farther next 11 days until apogee, when Earth-Moon distance will reach 404 402 km (251 284 mi).
4 days after its descending node on 5 February 2052 at 10:04 in ♈ Aries, the Moon is following the southern part of its orbit for the next 9 days, until it will cross the ecliptic from South to North in ascending node on 18 February 2052 at 16:11 in ♎ Libra.
17 days after beginning of current draconic month in ♎ Libra, the Moon is moving from the second to the final part of it.
12 days after previous South standstill on 28 January 2052 at 05:17 in ♐ Sagittarius, when Moon has reached southern declination of ∠-18.646°. Next day the lunar orbit moves northward to face North declination of ∠18.554° in the next northern standstill on 10 February 2052 at 09:08 in ♊ Gemini.
After 5 days on 14 February 2052 at 18:21 in ♌ Leo, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.848363 | 3.247202 |
As the winter milky way begins to set in the west, the spring time constellations bring views into the deeper universe, much more distant than the local open clusters and nebulosity of winter skies. Last night was particularly clear and offered an opportunity to visit Leo and Virgo to see some of the brighter galactic neighbors and also something much more distant. Here are some of the images taken with the 0.7m telescope, including shots of the most distant objects we have imaged to date. To view these images well, you might elect to reduce your room lighting and adjust your monitor to see fainter shades. All the images are monochrome luminance shots. No color this time.
What follows is a two-image focus on Messier 87, a large elliptical galaxy in Virgo. This one has been in the news quite a bit for the recent work done with the Event Horizon Telescope to image the region immediately surrounding M-87’s central supermassive black hole. This black hole also is the cause for a large apparent superluminal jet (relativistic jet) of material being ejected from the galaxy at very high speeds. The first image is a wide field view. There are many other galaxies in the image, all part of the Virgo Cluster of galaxies. The second image is a close-up of M-87 showing the relativistic jet radiating out to the lower right of the galaxy’s core.
Would you enjoy an annotated edition of the M-87 Region? Here it is! As many galaxies as could be ID’ed have been labeled.
3C_273 (star like object left-most of the central triangle of objects): one of the brighter nearby quasars in Virgo, this object holds the record for most distant object yet seen by the 0.7m telescope. It resides some 2.4 billion light years! As it is so luminous, it is not a difficult object to image, even with small telescopes, but is it fun to note that we are seeing such ancient light from the immediate surroundings of a black hole 2.4 billion light-years away!Can’t find it? Here it is again with markers: | 0.84433 | 3.28722 |
H-a mapped as red,OIII mapped as both blue and green. RGB stars added. Astrodon ROAG guided. Astrodon E-Series RGB and 6 nm H-a, OIII filters.
M76 is a planetary nebula about 3900 light years distant and about 4.5 light years across. The central bright bar is 1.5 x 3/4 arcminutes. it is a beautiful example of a toroidal (donut-shaped) planetary nebula. We are looking at a cross section of the donut, so the term "bipolar" is often used. In fact, it is thought that the famous Ring Nebula, M57, is similarly a bipolar object, but viewed in a different orientation relative to the sky. Scientists have done calculations to show that the core of the Ring is too bright for it to be a shperical shape. The problem with deducing the shape of planetary nebula, as discussed in Cosmic Butterflies by Sun Kwok is that they appear different in different light, such as H-a or OIII. Furthermore, they have very complex structures brought out by CCDs with very long exposures. They often have complicated outer halos that may have occurred in a different event with different geometry. For example, you can see evidence of a fainter outer halo in my image. Kowk indicates that the major axes of the bright and faint structures are off by 90 degrees! Complicated, indeed, but accessible to astrophotographers with telescopes of modest aperture and sensitive CCD cameras. | 0.806483 | 3.395012 |
From Cambridge, it will be visible between 20:55 and 04:36. It will become accessible around 20:55, when it rises to an altitude of 21° above your south-eastern horizon. It will reach its highest point in the sky at 00:47, 45° above your southern horizon. It will become inaccessible around 04:36 when it sinks below 21° above your south-western horizon.
136199 Eris opposite the Sun
This optimal positioning occurs when 136199 Eris is almost directly opposite the Sun in the sky. Since the Sun reaches its greatest distance below the horizon at midnight, the point opposite to it is highest in the sky at the same time.
At around the same time that 136199 Eris passes opposition, it also makes its closest approach to the Earth – termed its perigee – making it appear at its brightest and largest.
This happens because when 136199 Eris lies opposite the Sun in the sky, the solar system is lined up so that 136199 Eris, the Earth and the Sun form a straight line with the Earth in the middle, on the same side of the Sun as 136199 Eris.
In practice, however, 136199 Eris orbits much further out in the solar system than the Earth – at an average distance from the Sun of 67.83 times that of the Earth, and so its angular size does not vary much as it cycles between opposition and solar conjunction.
On this occasion, 136199 Eris will lie at a distance of 95.12 AU, and reach a peak brightness of magnitude 18.7. Even at its closest approach to the Earth, however, 136199 Eris is so distant from the Earth that it is not possible to distinguish it as more than a star-like point of light.
136199 Eris in coming weeks
Over the weeks following its opposition, 136199 Eris will reach its highest point in the sky four minutes earlier each night, gradually receding from the pre-dawn morning sky while remaining visible in the evening sky for a few months.
The position of 136199 Eris at the moment it passes opposition will be:
|Object||Right Ascension||Declination||Constellation||Magnitude||Angular Size|
The coordinates above are given in J2000.0.
|The sky on 17 October 2018|
8 days old
All times shown in EDT.
The circumstances of this event were computed using the DE405 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.
|17 Oct 2018||– 136199 Eris at opposition|
|13 Apr 2019||– 136199 Eris at solar conjunction|
|17 Oct 2019||– 136199 Eris at opposition|
|13 Apr 2020||– 136199 Eris at solar conjunction| | 0.820787 | 3.709719 |
The other day, I was reading a post by Ethan Siegel on his excellent blog, Starts With a Bang, about whether it makes sense to consider the universe to be a giant brain. (The short answer is no, but read his post for the details.) Something he mentioned in the post caught my attention.
But these individual large groups will accelerate away from one another thanks to dark energy, and so will never have the opportunity to encounter one another or communicate with one another for very long. For example, if we were to send out signals today, from our location, at the speed of light, we’d only be able to reach 3% of the galaxies in our observable Universe today; the rest are already forever beyond our reach.
My first reaction when reading this was, really? 3%. That seems awfully small.
What Siegel is talking about is an effect that is due to the expansion of the universe. Just to be clear, “expansion of the universe” doesn’t mean that galaxies are expanding into space from some central point, but that space itself is expanding everywhere in the universe proportionally. In other words, space is growing, causing distant galaxies to become more distant, and with space growing in the intervening space, the more distant a galaxy is from us, the faster it is moving away from us.
This means that as we get further and further away, the movement of those galaxies relative to us, gets closer and closer to the speed of light. Beyond a certain distance, galaxies are moving away from us faster than the speed of light. (This doesn’t violate relativity because those galaxies, relative to their local frame, aren’t moving anywhere near the speed of light.) That means they are outside of our light cone, outside of our ability to have any causal influence on them, outside of what’s called our Hubble sphere (sometimes called the Hubble volume). Note that we may still see galaxies outside of our Hubble volume if they were once within the Hubble sphere.
How big is the Hubble sphere? We can calculate its radius by dividing the speed of light by the Hubble constant: H0. H0 is the rate by which space is expanding. It is usually measured to be around 70 kilometers per second per mega-parsec, or about 21 kilometers per second per million light years. In other words, for every million light years a galaxy is from us, on average, the space between that galaxy and us will be increasing by 21 km/s (kilometers per second). So, a galaxy 100 million light years away is moving away from us at 2100 km/s (21 X 100), and a galaxy 200 million light years away will be receding at 4200 km/s (21 X 200), plus or minus any motion the galaxies might have relative to their local environment. The speed of light is about 300,000 km/s. If we take 300,000 and divide by 21, we get a bit over 14000. That would be 14000 million, or a Hubble sphere radius of around 14 billion light years.
(If you’re like me, you’ll immediately notice the similarity between the radius of the Hubble sphere and the age of the universe. When I first noticed this a few years ago, it seemed like too much of a coincidence, but I haven’t been able to find any relationship described in the literature. It appears to be a coincidence, although admittedly a freaky suspicious one.)
Okay, so the Hubble sphere is 14 billion light years in radius. According to popular science news articles, the farthest galaxies we can see are about 13.2 billion light years away, and the cosmic microwave background is 13.8 billion light years away, so everything we can see is safely within the Hubble sphere, right?
Wrong. Astronomy news articles almost universally report cosmological distances using light travel time, the amount of time that the light with which we’re seeing an object took to travel from the object to us. For relatively nearby galaxy, say 20-30 million light years away, that’s fine. In those cases, the light travel time is close enough to the co-moving or “proper” distance, the distance between us and the remote galaxy “right now”, that it doesn’t make a real difference. But when we look at objects that are billions of light years away, there starts to be an increasingly significant difference between the proper distance and the light travel time.
Those farthest viewable galaxies that are 13.2 billion light years away in light travel time are over 30 billion light years away in proper distance. The cosmic microwave background, the most distant thing we can see, is 46 billion light years away. So, in “proper” distances, the radius of the observable universe is 46 billion light years.
Crucially, the Hubble sphere radius calculated above is also in proper distance units. (The radius in light travel time would be around 9 billion light years per Ned Wright’s handy Cosmological Calculator.)
We can use the radius of each sphere to calculate their volumes. The volume of the Hubble sphere is about 11.5 trillion cubic light years. The volume of the observable universe is about 408 trillion cubic light years. 11.5 divided by 408 is .00282, or around 3%. Siegel knew exactly what he was talking about. (Not that I had any doubt about it.)
In other words, 97% of the observable universe is already forever out of our reach. (At least unless someone invents a faster than light drive.)
It’s worth noting that, as the universe continues expanding, all galactic clusters will become isolated from each other. In our case, in 100-150 billion years, the local group of galaxies will become isolated from the rest of the universe. (By then, the local group will have collapsed into a single elliptical galaxy. ) We’ll still be able to see the rest of the universe, but it will increasingly, over the span of trillions of years, become more red shifted, and bizarrely, more time dilated, until it is no longer detectable. By that time, there will only be red dwarfs and white dwarfs generating light, so the universe will already be a pretty strange place, at least by our current standards.
If our distant descendants manage to colonize galaxies in other galactic clusters, they will eventually become cut off from one another. If any information of the surrounding universe survives into those distant ages, it may eventually come to be regarded as mythology, something unverifiable by those civilizations living trillions of years from now. | 0.838765 | 3.794704 |
December 16, 2016 – In 1900, astronomer Joseph Lunt made a discovery. Peering through a telescope at Cape Town Observatory, the British–South African scientist spotted this beautiful sight in the southern constellation of Grus (The Crane): a barred spiral galaxy now named IC 5201.
Over a century later, the galaxy is still of interest to astronomers. For this image, the NASA/ESA Hubble Space Telescope used its Advanced Camera for Surveys (ACS) to produce a beautiful and intricate image of the galaxy. Hubble’s ACS can resolve individual stars within other galaxies, making it an invaluable tool to explore how various populations of stars sprang to life, evolved, and died throughout the cosmos.
IC 5201 sits over 40 million light-years away from us. As with two thirds of all the spirals we see in the Universe — including the Milky Way — the galaxy has a bar of stars slicing through its center. | 0.84437 | 3.072451 |
In less than 10 years, specifically on April 13, 2029, the date estimated by NASA for an asteroid 1,115 feet wide may pass very close to Earth, but without impact. This space body, named as Apophis in honor of an Egyptian God of Death, will approach 19,000 miles from our planet, a very close distance that represents a special moment for astronomers.
Even NASA described this as "an incredible opportunity for science". This was stated by Marina Brozovi, a scientist working at the Jet Propulsion Laboratory (JPL) of the US space agency. Apophis was discovered in 2004 by a team from the National Observatory of Kitt Peak (Arizona, USA). The Space Agency created a video in which it shows the path that the asteroid will make when it passes through the Earth.
In fact, during the 2019 Planetary Defense Conference held in Maryland, the observation plans and scientific opportunities of a celestial event began to be discussed for which there is still a decade to go. In addition, the possibility of sending a mission to the asteroid was raised.
According to NASA, such a large object passing close to Earth is a relatively rare phenomenon. At first glance, Apophis will be visualized as a bright point of light.
As the asteroid passes over the Atlantic Ocean, its trajectory changes briefly from red to gray, that is the moment of closest approach. After reaching its closest point, the asteroid will move towards the daytime sky and will no longer be visible. - NASA
"By observing Apophis during its flyby in 2029, we will gain important scientific knowledge that could one day be used for planetary defense," added Paul Chodas, director of the Center for Near-Earth Studies.
Apophis is one of the approximately 2,000 potentially dangerous asteroids known today. However, the possibility of it coming dangerously close " is a threat that could happen, although it is very unlikely, " reassured NPR network Paul Chodas, director of the Center for Near-Earth Objective Studies at NASA. | 0.816443 | 3.063066 |
YearWikipedia open wikipedia design.
This article does not have any sources. (December 2011)
One year is about 365 days long (except in a leap year). It is the time it takes the Earth to go completely around (orbit) the sun once. A year is actually 365.2422 days long, but a calendar has 365 days, except in a leap year.
There are several ways used to measure the length of a year.
- a solar year is based on the seasons. The Gregorian calendar is based on the solar year. The solar year is 365 days long.
- a tropical year is a solar year as measured between two vernal equinoxes, sometimes called the first day of spring.
- a lunar year is based on the moon and is usually 12 lunar months (29 days, 12 hours, 44 minutes each) or 354 days long.
- a sidereal year measures the time between when a selected fixed star is highest in the night sky.
- an anomalistic year is the difference between the times when the Earth gets closest to the sun.
- an eclipse year is the time between node passages. This is when the sun moves through a part of the sky where it is possible for the sun, Earth and moon to be in a line. It is also when eclipses can happen.
- There was no year numbered "year zero" in a normal system of counting, because it would mean there is a year earlier than the first year, which was the year AD one in the Anno Domini system, also called 1 CE in the Common Era, used with our Gregorian calendar. However, some astronomers call the year 1 BC (or BCE) "year 0" to make it easier for them to count leap years before that year.
- Ma (for megaannum) — a unit of time equal to one million years. The suffix "Ma" is often used in scientific disciplines such as geology, paleontology, and astronomy to signify very long time periods into the past or future. The simpler term "MYA" for "million years ago" is generally preferred on this wiki as being intuitively more simple for non-technical readers.
|Months of the Year| | 0.83116 | 3.01714 |
ERIDANUS — It’s time for Thailand to take its place among the stars – by name. And you can dictate what they will be, whether it’s after Thailand’s rivers, pretty words about sparkling, or descriptive, glorious words about the skies.
All Thai citizens can vote on a Thai name for the WASP-50 star and its orbiting exoplanet WASP-50 b from now until October 31. The naming effort is part of the “NameExoWorlds” project by the International Astronomical Union, the only internationally-recognized body that can officially assign names to celestial bodies.
All countries will be able to name an exoplanet and the star it orbits. The planetary system assigned to Thailand is the WASP-50 star, a yellow-white star in the Eridanus constellation, and the WASP-50 b planet, a gas giant almost one and a half times the mass of Jupiter.
Thailand’s Astronomical Research Institute of Thailand (NARIT) has narrowed down the naming options from more than 1,500 submissions sent in by Thais since June to three pairs of names for the star and its orbiting exoplanet. The first is “Chao Phraya” and “Mae Ping,” after the major rivers in Thailand.
“The Chao Phraya is the major river of Thailand created from many smaller tributaries such as Ping, Wang, Yom, and Nan Rivers,” the NARIT Facebook page wrote. “If we find more exoplanets in the future, we can name it after other rivers as well.”
The second option is a delicate description of astronomical bodies: “Prakaikaeo” and “Prakaidao,” which roughly mean “shining like glass” and “shining like a star.”
“Prakaikaeo is the shining light that spreads all around, like a star, and Prakai dao is like the shimmering reflection from the star that hits the exoplanet and lets us see them as they orbit,” NARIT wrote.
Finally, the third option is “Fahluang” and “Fahrin.”
“‘Fah’ both mean sky, and ‘luang’ means something that is great. So ‘Fahluang means something that is great and glorious in the sky, so it is an appropriate name for a star,” NARIT wrote. “‘Fahrin’ means precipitation flowing from the skies.”
Facebook user Jetsiri Sotechin said she voted for Fahluang-Fahrin because “it makes me think of King Rama IX, who is my great universe, and Fahrin makes me think of his rainmaking project that he gave to us citizens.”
To vote, fill out this form before October 31. A valid Thai passport ID is required, and only one vote per citizen will be counted. Ten lucky voters will also win souvenirs from the astronomical society.
Travelling there from Earth at light speed would take 606 years to get there. Planning to take a car? Be prepared to strap in for 7 billion years.
This naming project is held in honor of the organization’s 100th year. A similar campaign was held back in 2015, where Thailand named a star Chalawan and two orbiting planets Taphao Thong and Taphao Kaew, after Thai folklore “Krai Thong” of a crocodile king who captured a Phichit woman to make her his wife, and the other after her sister. | 0.831876 | 3.120714 |
A huge radio telescope in Chile has captured some dazzling views of a baby star lighting up an interstellar cloud about 1,400 light-years from Earth.
The ALMA radio telescope, a joint project between North America, Europe and Asia, recorded the star birth images. They show the nascent star unleashing material at hundreds of kilometers per second, which then slams into carbon monoxide molecules, causing them to glow. The glowing object spawned by the newborn star is what scientists call a Herbig-Haro object. European Southern Observatory officials used the new views to create a video tour of new star birth images.
"This system is similar to most isolated low mass stars during their formation and birth," Diego Mardones, a co-author of the study detailing the stellar findings said in a statement. "But it is also unusual because the outflow impacts the cloud directly on one side of the young star and escapes out of the cloud on the other. This makes it an excellent system for studying the impact of the stellar winds on the parent cloud from which the young star is formed." [See ALMA's photos of the baby star and Herbig-Haro object]
The new image of Herbig-Haro 46/47 (HH 46/47) produced by the ALMA telescope, its name is short for Atacama Large Millimeter/submillimeter Array, reveals two jets of material streaming away from the newborn star, one of which was never detected before.
One jet appears on the left side of the photo in pink and purple streaming partially toward Earth, while the orange and green jet on the right-hand-side show a jet pointed away from Earth.
ALMA's sensitive instrumentation took five hours to get these results. Earlier photos taken with other telescopes did not catch the second (orange and green) jet stream because dust surrounding the star obscured their views.
Astronomers observing the object with ALMA were also able to measure how quickly the glowing material is speeding through the cosmos, ESO officials said. The ejecta is moving at a much higher clip than previously measured, meaning that the outflowing gas has more energy and momentum than expected.
"ALMA's exquisite sensitivity allows the detection of previously unseen features in this source, like this very fast outflow," Héctor Arce, the lead author of the study appearing in the Astrophysical Journal, said in a statement. "It also seems to be a textbook example of a simple model where the molecular outflow is generated by a wide-angle wind from the young star."
The $1.3 billion ALMA radio telescope is an array of 66 of individual radio telescopes that create one of the most powerful telescopes ever built. Each dish is up to 40 feet wide (12 meters) and can weigh 115 tons. The combined effort of the telescopes allows scientists to see celestial sights invisible in optical light because they are masked by gas and dust. | 0.870084 | 3.675165 |
As President Trump continues to push America’s space exploration program forward with a plan to have astronauts return to the Moon by 2024, NASA is attempting to do its part. The space agency wants to send astronauts to the Moon’s South Pole — a mysterious region that has never been explored by man.
On Monday, the government space agency said the South Pole, which is abundant with ice and perhaps other resources as well, is a target ripe for exploration.
“We know the South Pole region contains ice and may be rich in other resources based on our observations from orbit, but, otherwise, it’s a completely unexplored world,” Steven Clarke, deputy associate administrator in NASA’s Science Mission Directorate, said in a statement. “The South Pole is far from the Apollo landing sites clustered around the equator, so it will offer us a new challenge and a new environment to explore as we build our capabilities to travel farther into space.”
AMERICANS WILL RETURN TO MOON BY 2024 — WITH OR WITHOUT NASA, PENCE SAYS
In August 2018, researchers found frozen surface water on the Moon’s polar regions, which could be broken down and eventually used for rocket fuel or oxygen to breathe. The scientists added surface ice could mean there is ice elsewhere in the solar system.
Though humans have never walked on the South Pole of the Moon, it is “the most thoroughly investigated region on the Moon” — at least, robotically.
The elliptical, polar orbit of NASA’s Lunar Reconnaissance Orbiter (LRO) is closest to the Moon during its pass over the South Pole region and has collected incredibly precise information about the region during its orbits over the past decade.
“We’ve mapped every square meter, even areas of permanent shadow,” Noah Petro, an LRO project scientist based at NASA’s Goddard Space Flight Center, added in the statement.
WATER MAY BE ALL OVER THE MOON, GIVING NEW HOPE FOR SUSTAINED LIFE
The water on the lunar surface is solid, due to the frigid temperatures in space, the lack of an atmosphere and the low angle at which sunlight hits the Moon’s surface in the polar regions. At times, the temperatures in the polar regions can reach -414 degrees Fahrenheit, which NASA described as “some of the lowest temperatures in the solar system.”
While the presence of water on the Moon is nothing new, (it was first discovered on the Moon in 2009 by three spacecraft, according to Space.com), the presence of ice on the polar regions could make lunar colonies a possibility. It would let astronauts harvest the water without having to bring it from Earth.
The presence of water on the Moon’s surface has also led some researchers to theorize its surface could have supported life billions of years ago.
“That record of water collection is a record that can help us understand how water and other volatiles have been moving around the solar system, so we’re very interested in getting to these locations and sampling the material there,” John W. Keller, a lunar scientist at NASA’s Goddard Space Flight Center, said in the statement.
CLICK HERE FOR THE FOX NEWS APP | 0.815038 | 3.046584 |
It’s the first in nearly 10 years, and there are only two more transits in the next couple of decades.
The planet Mercury will appear to pass across the face of the Sun on Monday, May 9, 2016. This event, known as a transit, will be visible in a small telescope with a proper solar filter from much of North and South America, Africa, and western Europe. It’s a great opportunity to see the mechanics of the solar system in action and to spot the elusive inner planet as it passes across the blazing solar disk.
A Rare Celestial Event
Transits of Mercury are relatively rare. They occur just 13 to 14 times each century. The last transit of Mercury occurred on Nov. 8, 2006. The next two happen on Nov. 11, 2019 and Nov. 13, 2032. Venus, the only other planet to appear to transit the Sun as seen from Earth, does so far less frequently, only twice per century on average. The last two transits of Venus were on June 8, 2004 and June 5, 2012. The next pair occur more than a hundred years from now in 2117 and 2125. So if you want to see a transit of an inner planet in your lifetime, it’s going to have to be a transit of Mercury.
The May 9, 2016 transit of Mercury occurs over a 7.5 hour period from 11:12 Universal Time (UT) to 18:42 Universal Time. This handy online calculator converts Universal Time, which is essentially Greenwich Mean Time, to your own time zone. The exact timing depends very slightly on your location and can vary by a minute or two.
The transit begins as the leading edge of Mercury’s tiny disk just contacts the face of the Sun. Just 3 minutes and 12 seconds later, near 11:15 UT, the full disk of the planet becomes visible against the Sun. The point of greatest transit, when Mercury lies closest to the center of the Sun’s disk, occurs at 14:57 Universal Time. The leading edge of the planet moves off the Sun’s disk at 18:39 UT, then the trailing edge exits the disk, and the transit ends, at 18:42 UT. At greatest transit, the center of Mercury’s disk will be 318.5” from the center of the Sun’s disk. The diagram above from Fred Espenak at EclipseWise.com shows the path of the planet, the timing, and the celestial coordinates of the Sun and Mercury at greatest transit.
The timing of this transit of Mercury favors observers in eastern North America, most of South America, and western Europe. The full transit will be visible in these regions. In western North America, Chile, and Hawaii and much of the Pacific, the transit will be in progress as the Sun rises. In central Europe, western Asia, India, and Africa, the transit will be in progress as the Sun sets.
This transit is not visible from Australia or New Zealand.
How to Observe the Transit of Mercury
The disk of the Mercury is just 12” across, too small to see with your unaided eyes and a pair of eclipse glasses. The planet will have an apparent area just 3% that of Venus during its transits, for example, so it will be hard to distinguish Mercury from a small sunspot. You will need a telescope at a magnification of at least 50x to see or image the transit. And, of course, you will need a good solar filter to keep the brilliant light of the Sun to a safe level. At no time during the transit of Mercury is it safe to look towards the Sun or attempt to image the Sun without a proper solar filter.
Which solar filter works best for observing a transit? Both main types of solar filter– broadband or “white-light” solar filters and narrowband or “hydrogen-alpha” solar filters work just fine for visual observation and imaging.
If you find yourself without a solar filter, you can project the image from your telescope with your lowest-power eyepiece onto a sheet of white paper a couple of feet away. This projection method, which is recommended only for scopes with aperture 80mm or less, isn’t as effective as direct observation with a solar filter, but it should be sufficient to show Mercury’s disk during the transit. Take great care when using this method to ensure no one looks through the unfiltered telescope.
Timing the Transit of Mercury
Most backyard astronomers enjoy the transit of Mercury simply for pleasure. But keen observers can make a contribution to science by attempting to measure the precise timing of the transit from their location. ALPO (The Association of Lunar and Planetary Observers) has a program to study the transit. You can learn more at this link.
Whether your interests lie in observing and enjoyment or precise measurement and science, plan to have a look at the May 9, 2016 transit of Mercury. It’s the first in nearly 10 years, and there are only two more transits in the next couple of decades. So gear up and get ready to see the solar system in action.
Source: Cosmic Pursuits | 0.835662 | 3.719573 |
Rather than looking down, the future of archaeology may one day look up to the stars.
The coined term of “space archaeologist” has been applied to archaeologists who use detailed satellite imagery to identify and examine archaeological sites here on earth.
Space archaeologists such as Sarah Parcak have been pioneers in their field, advancing our knowledge of past civilisations and developing community outreach projects like the Global Explorer initiative to identify and protect a dwindling cultural heritage at threat from looting and treasure hunters.
But instead of excavating our terrestrial past, space archaeologists could find themselves one day filtering through the layers of our orbit, the surface of the moon, and the strata of mars for relics of the early innovators that dawned a new era in our species exploration of space.
The near-Earth space environment is cluttered with man-made orbital debris and naturally occurring meteoroid particles. As of 2020, there are around 1,886 satellites currently orbiting the earth, with more than 23,000 orbital debris larger than 10 cm.
The estimated population of debris particles between 1 and 10 cm in diameter is approximately 500,000. The number of particles larger than 1 mm exceeds 100 million. As of January 1, 2020, the amount of material orbiting the Earth exceeded 8,000 metric tons.
NASA’s Orbital Debris Program Office contains downloadable data that allows you to monitor models of the orbital debris (MMOD) and the ongoing problem of debris growth that is a present danger for space exploration today.
One major source of debris was caused by the US and Soviet Union in the 1960’s and 1970’s where both super-powers were testing anti-satellite weapons in orbit. Accidental events have also contributed to the problem with incidents like the 2007 Russian Briz-M booster exploding in orbit.
Another cause of space debris can be attributed to the satellites we place in orbit for communications, weather station monitoring, GPS, and scientific study. When a satellite comes to the end of its operational life, it is normally put onto a trajectory that brings it into the earth’s atmosphere and burns up on re-entry. Satellites in a high orbit will be directed into space into a “graveyard orbit” around 200 miles further out and abandoned. Then there are the nonfunctional satellites that have lost communication with ground control, these have a degrading orbit encircling the earth and pose a risk of further collision creating more debris.
At the end of space stations operating life, like low orbit satellites they are directed into the Earth’s atmosphere and burnt up on re-entry to an area called the spacecraft cemetery, also known as the South Pacific Ocean Uninhabited Area. This area is roughly centred on the “Point Nemo” oceanic pole of inaccessibility – the location furthest from any land – which lies about 2,400 kilometres (1,500 mi) between Easter Island, Pitcairn Island, and Antarctica.
Apart from the International Space Station, there are two redundant stations still in orbit, the Genesis I and II, launched by Bigelow Aerospace in 2006 and 2007, an experimental space habitat to test the long-term viability of inflatable structures in space. The orbital life was originally estimated to be 12 years, but to date, the stations remain in a slowly decaying orbit.
As a species, we have left over 187,400 kilograms (413,100 lb) of material on the Moon, from spacecraft, rovers, containers of urine, flags, footprints, and countless personal items. The vacuum of space perfectly preserves these in situ, ensuring their continued survival for millions of years without any form of degradation that normally occurs with archaeology on Earth.
The first foreign object placed on the lunar service was Luna 2, launched on the 12th September 1959 by the Soviet Union with a further 23 Luna missions leaving spacecraft that either landed, crashed, or were intentionally crashed.
The USA would start exploratory missions from 1962 starting with Ranger 4, followed by another 4 ranger spacecraft. There would be a further 14 spacecraft left on the moon until the Apollo 11 would finally bring mankind to a new frontier. Post-Apollo 11, the USA would send a further 26 vehicles to the moon ranging from Apollo mission modules, rovers, satellites, probes, and LRV’s.
Some items noted from the Apollo missions include the Apollo lunar surface experiments packages, retroreflectors, the United States flags, the commemorative plaques attached to the ladders of the six Apollo Lunar Modules, the silver astronaut pin left by Alan Bean in honor of Clifton C. Williams, the Bible left by David Scott, the Fallen Astronaut statuette and memorial plaque placed by the crew of Apollo 15, the Apollo 11 goodwill messages disc and the golf balls Alan Shepard hit during an Apollo 14 moonwalk.
The Lunar surface is an intact museum and heritage site that provides a unique setting for our early period of space travel from the Soviet Union, the USA, China, Japan, India, and Israel.
The most notable are the Apollo 11 and Apollo 17 landing sites which the USA has proposed a bill to protect, listing them as off-limits, and including close proximity limits for ground-travel and no-fly zones to avoid spraying rocket exhaust or dust onto aging but historic equipment.
When the Italian Astronomer Giovanni Schiaparelli described seeing canali on the surface of Mars in 1877, many in the English-speaking world began to believe that the canals were artificially created by some ancient civilisation.
Mars was further embellished in the public imagination when in 1976, NASA’s Viking 1 orbiter photographed a geological feature in the Cydonia region that many believed to resemble a humanoid face. Finding a civilisation on Mars would have changed the face of our understanding of the Universe, but atlas, these dreams will have to assigned to a H. G. Wells novel.
Unlike the moon, Mars has an atmosphere and weather system that can cause vast dust storms made from oxidized iron that can last for months at a time blocking out light and envelope optical equipment and solar panels making equipment useless or non-operational for some duration.
The first spacecraft deployed on Mars was the Mars 2 launched by the Soviet Union in 1971, followed by the Mars 3 and Mars 6 missions. The USA launched its first mission, the Viking 1 lander in 1976 followed by several more probes and rovers. Even the United Kingdom safely managed to send a probe to Mars, the Beagle 2 in 2003 but subsequently lost contact when its solar panels failed to deploy.
The missions that followed focused on lander and rover deployment. The Spirit Rover operated for 2210 sols, the Opportunity Rover 5111 sols and the brave Curiosity Rover, launched in 2012 is still in operation today. The last mission to Mars was the InSight lander, sent to the red planet to measure seismic activity and provide accurate 3D models of the planet’s interior and internal heat flow. To date, there are 17 spacecraft on Mars, two remain operational with the remainder either crashed, lost contact, or damaged by atmospheric stresses and friction.
Space offers us a new frontier for the future, one that has preserved a time capsule of each stage in our technological development. As we explore the outer reaches, our descendants may find themselves recovering those first explorers that have paved the way – from the Voyager, Pioneer and New Horizons probes, to the junk we’ve left behind as a civilisation in our ever-expanding pursuit in exploring the cosmos. | 0.824332 | 3.29432 |
Asteroids, planets and rare meteor showers, oh my! June skies alight with stellar happenings.
Jane Houston Jones: What's Up for June. A planetary trio at sunset plus asteroids you can see. Hello and welcome. I'm Jane Houston Jones at NASA's Jet Propulsion Laboratory in Pasadena, California. The month begins with a gorgeous trio of planets: Mercury, Venus and Jupiter, low on the west-northwest horizon on June 1 and 2. As the month progresses, Jupiter slips into the sunset while Mercury and Venus rise higher in the sky.
Jones: Asteroid 1998 QE2, which safely passed by the Earth on May 31, is visible in the night skies through small and medium telescopes this month. Amateur astronomers looking towards the constellations Libra and Ophiucus the first week of June can watch it move about the diameter of a full moon in an hour and a half.
Jones: On June 11 we might witness the return of a rare meteor showed called the Gamma Delphinids radiating from the tiny dolphin-shaped constellation Delphinus. The best part of the sky to watch is usually an area about 30 degrees away from the radiant point of the shower.
Jones: The first four asteroids ever discovered: Ceres, Vesta, Pallas and Juno are all visible this month and are all about magnitude 8 or 9, requiring binoculars or telescopes.
These four are Main Belt asteroids. That means they orbit only in the area between Mars and Jupiter so they pose no threat to Earth. Ceres and Vesta can be found near the stars of the constellation Gemini. Pallas is only visible from the Southern Hemisphere before dawn this month. Juno can be found among the star of Aquarius, as can asteroid Bamberga. Asteroid 324 Bamberga is the 15th-largest asteroid as measured by its diameter, but it was one of the last large asteroids to be discovered nearly a hundred years after the first 4 were discovered in the early 1800's. Wrap up the month with a trip out of town. By month-end the moon will not rise until midnight, and you'll have a great view of the Milky Way rising in the East, spanning the sky from horizon to horizon.
You can read about asteroid news and features at j p l dot nasa dot gov slash asteroidwatch. And you can learn about all of NASA's missions at w w w dot nasa dot gov. That's all for this month. I'm Jane Houston Jones.
NASA Jet Propulsion Laboratory, California Institute of Technology | 0.841103 | 3.267992 |
There's not much air on Mars – atmospheric pressure is less than a hundredth of what we breathe on Earth – but what little it has is clueless planetary scientists.
Oxygen, which represents about 0.13 percent of the Martian atmosphere, is the latest mystery.
In a newspaper published this month in the Journal of Geophysical Research: Planets, scientists working with data collected in a curious NASA vehicle reported that oxygen levels unexpectedly varied depending on the seasons of Mars, at least in the neighborhood, which curiosity
This stems from the fact that earlier this year, after a rover reading, there was a large explosion of methane, another gas emitted on Earth by living things, which disappeared almost immediately.
"It's confusing, but exciting," said Sushil K. Atreya, professor of climate and space science at the University of Michigan, working on Atmospheric Curiosity Measurements. "That keeps us on our feet." Mars is certainly not boring. "
The Mars year lasts 687 days, so scientists studying oxygen variations were able to investigate behavior for nearly three Martian years until December 2017.
Oxygen Level " It rises relatively higher in spring, "Melissa said G. Trainer, research fellow at NASA's Goddard Space Flight Center in Greenbelt, MD, and lead author of the new document, "and then sinks below what we would expect later this year." “
Carbon dioxide is a major component of Martian air, and scientists have for decades understood its tides. At the poles in winter it falls out of the air and freezes on ice and then returns to the atmosphere in the spring.
High in the Martian atmosphere, ultraviolet light breaks down carbon dioxide into carbon monoxide and oxygen. atoms and then closer to earth, interactions with water release oxygen atoms into molecular pairs. Because oxygen molecules should be fairly stable and persist for about ten years, scientists expected that the number of oxygen molecules would remain almost constant
Atmospheric curiosity measurements showed exactly that pattern of nitrogen and argon, the other two trace gases in the Mars atmosphere. But for oxygen, spring concentrations were increased by a third.
"It was a very unexpected outcome, an unexpected phenomenon ," Dr. Trainer. “We don't know much about the oxygen cycle on Mars. This becomes obvious. “
The cycle was not the same every year, and scientists could not find a clear explanation – such as temperature, dust dust storms or ultraviolet radiation – which changed. from year to year.
On Earth, most of the oxygen is generated by photosynthesis of plants. But meanwhile, for scientists from Mars, it is far on the list of explanations.
"You must exclude all other processes before you go there," Atreya.
More likely sources are chemicals such as hydrogen peroxide and perchlorates known to be on Martian impurities. "It is quite clear that you need flow from the surface," Dr. Atreya. “Nothing in the atmosphere will create this kind of ascent.”
But as these chemicals can release and absorb enough oxygen to explain seasonal increase and decrease, it is difficult to detect, especially since there are only 19 oxygen measurements over five and a half years.
An interesting possibility is that the mystery of oxygen could be associated with another trace gas, methane, which also acts strangely in the Martian atmosphere.
"It is not entirely clear whether there is a correlation or not," Dr. Trainer.
Since 2003 several scientists have reported large methane explosions based on measurements from terrestrial telescopes, orbiting a spacecraft and a rover of curiosity. Other times, methane was largely absent.
The presence of methane was a surprise to scientists because the known gas generation processes are either biological – methane producing microbes – or geothermal, which would be a promising environment for life on today's Mars.
Now scientists want to know not only about how methane is formed on Mars, but how quickly it disappears. In June, the curiosity experienced a particularly strong explosion of methane – 21 ppm by volume. However, when the experiment was repeated a few days later later it came out empty – less than 1 part per billion.
The European Space Agency's Mars Express spacecraft crossed Gale Crater, instead of a rover. , only about five hours after the curiosity measured the dose – and found nothing. (The same tool confirmed a methane explosion in 2013 that observed curiosity.)
"I would say this point measured by curiosity seems very short and local," said scientist Marco Giuranna. at the Italian National Institute of Astrophysics, in charge of Mars Express.
Even between the explosions, methane on Mars is a secret. Curiosity measured the low but persistent presence of methane, approximately 410 particles per trillion, which increases and decreases over time. But the newer European circular, the ExoMars Trace Gas Orbiter, which has the ability to measure as little methane as 50 particles per trillion, has to see methane ever since it started measuring in April last year. The orbiter looks at an area a few kilometers above the ground and curiosity makes measurements on the surface. However, scientists thought that methane near the ground would be mixed in a higher atmosphere in a few weeks.
"The scientific logic puzzle is that these two lines of evidence simply cannot be reconciled," Oleg Korablev of the Space Research Institute. in Russia wrote an e-mail . dr Korablev is also the chief researcher of one of the two Trace Gas Orbiter instruments that measure methane.
Håkan Svedhem, researcher at the Trace Gas Orbiter, said: “We do not know any mechanism that can completely destroy methane in such a short time. time. It is truly a secret unless curiosity sits directly over a single local resource on the planet, and even if it does, that resource must be small. "
Scientists working on these three missions plan to close Gale Crater observations on December 15, and again in late December, Giuranna.
Four missions towards Mars are planned to begin next year. Three of them – built by NASA, China and jointly by the European Union and Russia – will try to place new levels on the planet's surface. The fourth spacecraft of the United Arab Emirates enters orbit.
However, none of them will have methane or oxygen meters. | 0.874377 | 3.912274 |
The STEREO mission to study the Sun also has observed some unusual comet-like features exhibited by the planet Mercury, with a coma of tenuous gas surrounding the planet and a very long tail extending away from the sun. These types of features had been seen before from telescopes on Earth, but the STEREO observations are helping scientists to understand the nature of the emissions coming from Mercury, which might be different from what was previously thought.
Another note of interest: the tail in the STEREO data was actually discovered by a fellow blogger, Ian Musgrave, who writes Astroblog. He is a medical researcher in Australia who has a strong interest in astronomy. Viewing the on-line data base of STEREO images and movies, Dr. Musgrave recognized the tail and sent news of it to a team of astronomers from Boston University to compare it with their observations.
The STEREO mission has two satellites placed in the same orbit around the Sun that the Earth has, but at locations ahead and behind it. This configuration offers multi-directional views of the electrons and ions that make up the escaping solar wind. On occasion, the planet Mercury appears in the field of view of one or both satellites. In addition to its appearance as a bright disk of reflected sunlight, a ‘tail’ of emission can be seen in some of the images.
From Earth-based telescopes, astronomers have seen how the Sun’s radiation pressure pushes sodium atoms from Mercury’s surface away from the planet – and away from the Sun – creating a tail that extends many hundreds of times the physical size of Mercury.
Much closer to Mercury, several smaller tails composed of other gases, both neutral and ionized, have been found by NASA’s MESSENGER satellite as it flew by Mercury in its long approach to entering into a stable orbit there.
“We have observed this extended sodium tail to great distances using our telescope at the McDonald Observatory in Texas,” Boston University graduate student Carl Schmidt explained, “and now the tail can also be seen from satellites near Earth.”
“What makes the STEREO detections so interesting is that the brightness levels seem to be too strong to be from sodium,” said Boston University graduate student Carl Schmidt, lead author on a paper that was presented at European Planetary Science Congress in Rome this week.
Now, the Boston University scientists are working with the STEREO scientists to try and sort everything out.
The current focus of the team is to sort out all of the possibilities for the gases that make up the tail. Dr. Christopher Davis from the Rutherford Appleton Laboratory in Chilton, England, a member of the STEREO team is working closely with the Boston University group on refining the brightness calibration methods, and determining the precise wavelengths of light that would get through the cameras’ filters.
“The combination of our ground-based data with the new STEREO data is an exciting way to learn as much as possible about the sources and fates of gases escaping from Mercury,” said Michael Mendillo, Professor of Astronomy at Boston University and director of the Imaging Science Lab where the work is being done.
“This is precisely the type of research that makes for a terrific Ph.D. dissertation,” Mendillo added.
Read the team’s paper: “Observations of Mercury’s Escaping Sodium Atmosphere by the STEREO Spacecraft” | 0.909284 | 3.834208 |
A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses (M☉)) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, from 5,000 K and lower. The appearance of the red giant is from yellow-orange to red, including the spectral types K and M, but also class S stars and most carbon stars.
The most common red giants are stars nearing the end of the so-called red-giant-branch (RGB) but are still fusing hydrogen into helium in a shell surrounding a degenerate helium core. Other red giants are: the red clump stars in the cool half of the horizontal branch, fusing helium into carbon in their cores via the triple-alpha process; and the asymptotic-giant-branch (AGB) stars with a helium burning shell outside a degenerate carbon–oxygen core, and sometimes with a hydrogen burning shell just beyond that.
Red giants are stars that have exhausted the supply of hydrogen in their cores and switched to thermonuclear fusion of hydrogen in a shell surrounding the core. They have radii tens to hundreds of times larger than that of the Sun. However, their outer envelope is lower in temperature, giving them a reddish-orange hue. Despite the lower energy density of their envelope, red giants are many times more luminous than the Sun because of their great size. Red-giant-branch stars have luminosities about a hundred to several hundred times that of the Sun (L☉), spectral types of K or M, have surface temperatures of 3,000–4,000 K, and radii about 20–100 times the Sun (R☉). Stars on the horizontal branch are hotter, whereas asymptotic-giant-branch stars are around ten times more luminous, but both these types are less common than those of the red-giant branch.
Among the asymptotic-giant-branch stars belong the carbon stars of type C-N and late C-R, produced when carbon and other elements, are convected to the surface in what is called a dredge-up. The first dredge-up occurs during hydrogen shell burning on the red-giant branch, but does not produce dominant carbon at the surface. The second, and sometimes third, dredge up occurs during helium shell burning on the asymptotic-giant branch and convects carbon to the surface in sufficiently massive stars.
The stellar limb of a red giant is not sharply-defined, contrary to their depiction in many illustrations. Rather, due to the very low mass density of the envelope, such stars lack a well-defined photosphere, and the body of the star gradually transitions into a 'corona'. The coolest red giants have complex spectra, with molecular lines, masers, and sometimes emission.
Another noteworthy feature of red giants is that, unlike Sun-like stars whose photospheres have a large number of small convection cells (solar granules), red-giant photospheres, as well as those of red supergiants, have just a few large cells, whose feature cause the variations of brightness so common on both types of stars.
Red giants are evolved from main-sequence stars with masses in the range from about 0.3M☉ to around 8M☉. When a star initially forms from a collapsing molecular cloud in the interstellar medium, it contains primarily hydrogen and helium, with trace amounts of "metals" (in stellar structure, this simply refers to any element that is not hydrogen or helium i.e. atomic number greater than 2). These elements are all uniformly mixed throughout the star. The star reaches the main sequence when the core reaches a temperature high enough to begin fusing hydrogen (a few million kelvin) and establishes hydrostatic equilibrium. Over its main sequence life, the star slowly converts the hydrogen in the core into helium; its main-sequence life ends when nearly all the hydrogen in the core has been fused. For the Sun, the main-sequence lifetime is approximately 10 billion years. More-massive stars burn disproportionately faster and so have a shorter lifetime than less massive stars.
When the star exhausts the hydrogen fuel in its core, nuclear reactions can no longer continue and so the core begins to contract due to its own gravity. This brings additional hydrogen into a zone where the temperature and pressure are adequate to cause fusion to resume in a shell around the core. The higher temperatures lead to increasing reaction rates, enough to increase the star's luminosity by a factor of 1,000–10,000. The outer layers of the star then expand greatly, thus beginning the red-giant phase of the star's life. As the star expands, the energy produced in the burning shell of the star is spread over a much larger surface area, resulting in a lower surface temperature and a shift in the star's visible light output towards the red – hence it becomes a red giant. In actuality, though the color usually is orange. At this time, the star is said to be ascending the red-giant branch of the Hertzsprung–Russell (H–R) diagram. The outer layers carry the energy evolved from fusion to the surface by way of convection. This causes material exposed to nuclear "burning" in the star's interior (but not its core) to be brought to the star's surface for the first time in its history, an event called the first dredge-up.
The evolutionary path the star takes as it moves along the red-giant branch, that ends finally with the complete collapse of the core, depends on the mass of the star. For the Sun and stars of less than about 2 M☉ the core will become dense enough that electron degeneracy pressure will prevent it from collapsing further. Once the core is degenerate, it will continue to heat until it reaches a temperature of roughly 108 K, hot enough to begin fusing helium to carbon via the triple-alpha process. Once the degenerate core reaches this temperature, the entire core will begin helium fusion nearly simultaneously in a so-called helium flash. In more-massive stars, the collapsing core will reach 108 K before it is dense enough to be degenerate, so helium fusion will begin much more smoothly, and produce no helium flash. Once the star is fusing helium in its core, it contracts and is no longer considered a red giant. The core helium fusing phase of a star's life is called the horizontal branch in metal-poor stars, so named because these stars lie on a nearly horizontal line in the H–R diagram of many star clusters. Metal-rich helium-fusing stars instead lie on the so-called red clump in the H–R diagram.
In stars massive enough to ignite helium fusion, an analogous process occurs when the central helium is exhausted and the star collapses once again, causing helium in an outer shell to begin fusing. At the same time hydrogen may begin fusion in a shell just outside the burning helium shell. This puts the star onto the asymptotic giant branch, a second red-giant phase. The helium fusion results in the build up of a carbon–oxygen core. A star below about 8 M☉ will never start fusion in its degenerate carbon–oxygen core. Instead, at the end of the asymptotic-giant-branch phase the star will eject its outer layers, forming a planetary nebula with the core of the star exposed, ultimately becoming a white dwarf. The ejection of the outer mass and the creation of a planetary nebula finally ends the red-giant phase of the star's evolution. The red-giant phase typically lasts only around a billion years in total for a solar mass star, almost all of which is spent on the red-giant branch. The horizontal-branch and asymptotic-giant-branch phases proceed tens of times faster.
If the star has about 0.2 to 0.5 M☉, it is massive enough to become a red giant but does not have enough mass to initiate the fusion of helium. These "intermediate" stars cool somewhat and increase their luminosity but never achieve the tip of the red-giant branch and helium core flash. When the ascent of the red-giant branch ends they puff off their outer layers much like a post-asymptotic-giant-branch star and then become a white dwarf.
Stars that do not become red giants
Very low mass stars are fully convective and continue to fuse hydrogen into helium for trillions of years until only a small fraction of the entire star is hydrogen. Luminosity and temperature steadily increase during this time, just as for more-massive main-sequence stars, but the length of time involved means that the temperature eventually increases by about 50% and the luminosity by around 10 times. Eventually the level of helium increases to the point where the star ceases to be fully convective and the remaining hydrogen locked in the core is consumed in only a few billion more years. Depending on mass, the temperature and luminosity continue to increase for a time during hydrogen shell burning, the star can become hotter than the Sun and tens of times more luminous than when it formed although still not as luminous as the Sun. After some billions more years, they start to become less luminous and cooler even though hydrogen shell burning continues. These become cool helium white dwarfs.
Very-high-mass stars develop into supergiants that follow an evolutionary track that takes them back and forth horizontally over the HR diagram, at the right end constituting red supergiants. These usually end their life as type II supernova. The most massive stars can become Wolf–Rayet stars without becoming giants or supergiants at all.
Prospects for habitability
Although traditionally it has been suggested the evolution of a star into a red giant will render its planetary system, if present, uninhabitable, some research suggests that, during the evolution of a 1 M☉ star along the red giant branch, it could harbor a habitable zone for several times 109 years at 2 AU out to around 108 years at 9 AU out, giving perhaps enough time for life to develop on a suitable world. After the red giant stage, there would for such a star be a habitable zone between 7 and 22 AU for an additional 109 years.
Enlargement of planets
As of June 2014, 50 giant planets have been discovered around giant stars. However these giant planets are more massive than the giant planets found around solar-type stars. This could be because giant stars are more massive than the Sun (less massive stars will still be on the main sequence and will not have become giants yet) and more massive stars are expected to have more massive planets. However the masses of the planets that have been found around giant stars do not correlate with the masses of the stars therefore the planets could be growing in mass during the stars' red giant phase. The growth in planet mass could be partly due to accretion from stellar wind although a much larger effect would be Roche lobe overflow causing mass-transfer from the star to the planet when the giant expands out to the orbital distance of the planet.
Well known examples
Prominent bright red giants in the night sky include Aldebaran (Alpha Tauri), Arcturus (Alpha Bootis), and Gamma Crucis (Gacrux), whereas the even larger Antares (Alpha Scorpii) and Betelgeuse (Alpha Orionis) are red supergiants.
- Mira (ο Ceti), a red M-type asymptotic-giant-branch giant.
- Albireo (β Cygni), a K-type giant.
- 4 Cassiopeiae (4 Cas), an M-type giant.
The Sun as a red giant
In about 5 to 6 billion years, the Sun will have depleted the hydrogen fuel in its core and will begin to expand. At its largest, its surface (photosphere) will approximately reach the current orbit of the Earth. It will then lose its atmosphere completely; its outer layers forming a planetary nebula and the core a white dwarf. The evolution of the Sun into and through the red-giant phase has been extensively modelled, but it remains unclear whether the Earth will be engulfed by the Sun or will continue in orbit. The uncertainty arises in part because as the Sun burns hydrogen, it loses mass causing the Earth (and all planets) to orbit farther away. There are also significant uncertainties in calculating the orbits of the planets over the next 5 – 6.5 billion years, so the fate of the Earth is not well understood. At its brightest, the red-giant Sun will be several thousand times more luminous than today but its surface will be at about half the temperature. In its red giant phase, the Sun will be so bright that any water on Earth will boil away into space, leaving our planet unable to support life.
- Zeilik, Michael A.; Gregory, Stephan A. (1998). Introductory Astronomy & Astrophysics (4th ed.). Saunders College Publishing. pp. 321–322.
- Boothroyd, A. I.; Sackmann, I. ‐J. (1999). "The CNO Isotopes: Deep Circulation in Red Giants and First and Second Dredge‐up". The Astrophysical Journal 510: 232.
- Measurements of the frequency of starspots on red giant stars
- orange sphere of the sun
- Schwarzschild, Martin (1975). "On the scale of photospheric convection in red giants and supergiants.". Astrophysical Journal 195: 137–144.
- "Seeing into the Heart of Mira A and its Partner". www.eso.org. European Southern Observatory. Retrieved 2 December 2014.
- The End of the Main Sequence, Gregory Laughlin, Peter Bodenheimer, and Fred C. Adams, The Astrophysical Journal, 482 (June 10, 1997), pp. 420–432.
- Bibcode: 1994A&AS..105...29F
- Harvard University search for orange-yellow clumps
- Sackmann, I. -J.; Boothroyd, A. I.; Kraemer, K. E. (1993). "Our Sun. III. Present and Future". The Astrophysical Journal 418: 457.
- Reiners, A. & Basri, G. On the magnetic topology of partially and fully convective stars Astronomy and Astrophysics vol 496 no.3 pp787–790, March year=2009
- Brainerd, Jerome James (2005-02-16). "Main-Sequence Stars". Stars. The Astrophysics Spectator. Retrieved 2006-12-29.
- Richmond, Michael. "Late stages of evolution for low-mass stars". Retrieved 2006-12-29.
- Laughlin, G.; Bodenheimer, P.; Adams, F. C. (1997). "The End of the Main Sequence". The Astrophysical Journal 482: 420.
- Crowther, P. A. (2007). "Physical Properties of Wolf-Rayet Stars". Annual Review of Astronomy and Astrophysics 45 (1): 177–219.
- Georges Meynet; Cyril Georgy; Raphael Hirschi; Andre Maeder; Phil Massey; Norbert Przybilla; -Fernanda Nieva. "Red Supergiants, Luminous Blue Variables and Wolf-Rayet stars: The single massive star perspective". Societe Royale des Sciences de Liege, Bulletin, vol. , p. (Proceedings of the th Liege Astrophysical Colloquium, held in Li\'ege 12–16 July 2010, edited by G. Rauw, M. De Becker, Y. Naz\'e, J.-M. Vreux, P. Williams). v1 80 (39): 266–278.
- Lopez, Bruno; Schneider, Jean; Danchi, William C. (2005). "Can Life Develop in the Expanded Habitable Zones around Red Giant Stars?". The Astrophysical Journal 627 (2): 974–985.
- The properties of planets around giant stars, M. I. Jones, J. S. Jenkins, P. Bluhm, P. Rojo, C. H. F. Melo, (Submitted on 3 Jun 2014) | 0.920988 | 4.052794 |
The largest all-sky survey of celestial objects ever made by humans was released this month, using data from The European Space Agency (ESA)'s Gaia satellite.
The survey captures more than a billion stars, and will become part of the most detailed 3D map ever made of our Milky Way galaxy.
“Gaia has pinned down the precise position on the sky and the brightness of 1142 million stars,” ESA reports. The star catalogue also documents details of the distances and motions across the sky for over two million stars.
“Gaia is at the forefront of astrometry, charting the sky at precisions that have never been achieved before,” said Alvaro Giménez, ESA’s Director of Science. “[This] gives us a first impression of the extraordinary data that await us and that will revolutionise our understanding of how stars are distributed and move across our Galaxy.”
Artist's impression of Gaia mapping the stars of the Milky Way [ESA]
Gaia started its scientific work in July of 2014. This is the first big data release from the project, representing data gathered during the first 14 months, through September 2015.
From the New York Times:
Most of the Milky Way’s stars reside in the so-called Galactic Plane, shown here as a bright horizontal strip about 100,000 light-years across and about 1,000 light-years deep. (...) As extensive as these measurements are, Gaia will catalog just 1 percent of the stars found in the Milky Way by the time its mission ends.
You can follow GAIA's mission on Facebook.
In a new interview with the Journal of the American Medical Association above, Anthony Fauci, National Institute of Allergy and Infectious Diseases (NAID), said he expects the US will have 100 million doses of a COVID-19 vaccine before the end of the year. “Then, by the beginning of 2021, we hope to have a couple […]
Just for kicks, Paul Rule, 66, participated in a study launched by the Cambridge Natural History Society that enlisted citizen scientists and nature-lovers to help deepen knowledge of the flora and fauna in Cambridge, England. Rule recorded nearly 600 different animal species in his “ordinary” city garden, including an elephant moth like the one seen […]
Astronaut David Scott re-created, in 1971 during the Apollo 15 mission, Galileo’s “falling bodies” experiment by dropping a hammer and feather on the moon at the same time. Simply, both fell at the same rate because there was no air resistance. screengrab via Wonders of Physics/YouTube (Digg)
The world is holding its collective breath. As states begin cautiously reopening, no one is sure exactly what to expect. But one thing is clear: most Americans are worried about their bank accounts. By the end of March, the average American household was spending 40 percent less on their credit cards than they were one […]
Over 25 years, eBay has carved out its space as the commerce hub of choice online. With 182 million users worldwide, that works out to about 35 percent of all US mobile users who shop those eBay storefronts. But did you know there are usually around 1.3 billion — with a B — active for-sale […]
Software apps are a dime a dozen. Well, if you’re going by their actual monetary cost, maybe not really. But considering how useless some poorly conceived, poorly executed apps are at doing the job you actually downloaded them to accomplish, it isn’t a stretch to think that many apps aren’t even worth a free download. […] | 0.853006 | 3.001367 |
This is an awesome book on Black Holes. And about one of the greatest intellectual wars in the recent times. Though the core theme of the book is the information paradox pertaining to the Black Hole physics, the book covers the fundamentals of some of the fundamental sciences (esp. Quantum Mechanics, QCD, String Theory) that lead to a better understanding of what happens in and around black holes. There a good deal of explanation around what ‘Information’ is. I had heard Leonard Susskind on a few popular science documentaries. Not everyone can explain things well. But Susskind can. The book also led me to some interesting (and disturbing) stuff that we were never taught. Like, energy may not be conserved in general relativity!!!! We’ll, it is not that simple, but then, no one really understands 🙂
There have been some very recent developments around the Black Holes. So better read this book before the information becomes obsolete!
- When you look at the moon, you are looking a little more than a second into the past.
- When you look at the sun, you are looking a little more than 8 minutes into the past.
- When you look at the pole star, you are looking about 430 years into the past.
- The list goes on. There are stars, galaxies, galaxy clusters which could be your window to the past ranging from a few years to billions of years!
You could actually go on into the past until about a few hundred million years after the Big Bang (I wouldn’t get into the technicalities of why we can’t see beyond). We don’t even know if some of these exist as of today when we are looking at them.
With naked eyes you can only see up to a certain limit. Telescopes can push you into the realms ranging from a few seconds to a few billion years into the past. I always wanted to push beyond what I could see with naked eyes. I started with a pair of astronomical binoculars. Little did I know that just a small magnification can help you improve the visibility into the past drastically.
I wanted to push this further. And luckily I got this opportunity a few weeks ago. I came across a large enough telescope and a very knowledgeable and generous guide, Kiran. When you look through a telescope, you don’t get to see the planets, stars and galaxies like those glossy high resolution images. You need to use your imagination to understand what you see.
When I first saw Saturn with its rings clearly demarcated, I somehow felt a personal connect. There was a feeling of possessiveness. After all I was not looking at an image. I was directly looking through the air. The galaxies looked like sugar sprinkled on paper. A few galaxy clusters again looked like salt sprinkled on paper. And when I paid a little more attention, I could make out that they were concentrated towards the center. I thought, could there be a black hole at the center? To my delight, Kiran confirmed that there is a black hole at the center indeed! It was like attaining nirvana! Can you imagine? I was staring at a black hole. Wow!
And it was not over yet. It turned out to be a lucky night for stargazing. The lazy city of Mysore provided an amazing backdrop for an exciting starry night. I saw a white dwarf! Yes, a dying star!! It had exhausted its fuel and had blown into a giant white shell, with a black dot, which was the core.
I stopped for a moment to think that I am looking at something which happened millions of years ago. When humans still hadn’t evolved. Probably when dinosaurs walked the Earth. Or maybe beyond that. I wanted to push back further. But alas! You can’t get into the billions. You probably need to get over the Earth’s atmosphere to look back to that scale. That is what the Hubble has been doing.
But I was more than satisfied with what I saw. I saw the child inside me waking up. I would never forget that night.
Some day, I wish to push the limits and get closer to the big bang by looking through one of the giant telescope arrays.
The reason I am compelled to write this post is that I’ve just got a payment reminder for the domain. I must write something, else I’ll not feel good while releasing the payment. Thanks to Ankit, I haven’t yet paid anything for hosting.
I didn’t know what to write about. So I will just mention a few pointers on faster than light travel which I have come across recently. We all know that Einstein’s relativity puts a limit on the maximum speed through which anything can travel; and the limit is the speed of light, which is constant.
I read an interesting interpretation somewhere. One can’t ‘encounter’ something which travels faster than light. To understand what it means, imagine that two of us stand 1 feet apart. And suddenly, the space between us rips apart at speeds faster than the speed of light. So we may be moving away from each other at faster than light speeds, but we wouldn’t ‘encounter’ it. We would never be able to see each other until the space keeps expanding at those rates. But hold on! If such a thing does happen and suddenly someone disappears from our sight, wouldn’t that itself prove that faster than light travel is possible? By not ‘encountering’ each other, wouldn’t we actually ‘encounter’ faster than light travel?
Wow! I just did a thought experiment like Einstein! And also found a paradox. Not bad. And that too triggered by a $10 domain renewal bill. Innovation can’t be this cheap. Something must be wrong. Find out 🙂
No matter how hard I think, I can’t even come close to visualizing space time. And I am sure not even Einstein could , though he was the one who came up with the counter-intuitive and bold concept of time dilation. While the maths is absolutely spot-on and it has lived up almost a century now, describing the world at an macro scale scale (yes, the quantum world has got a different set of maths), I am sure it would take us ages to be able to engulf it (but if Darwin was correct, we would ultimately “evolve” to be able to visualize it, provided we survive long enough).
Anyways, to cut it down, I somewhere read that the diameter of the observable universe is about 97 billion light years, i.e. it is about 48.5 billion light years radially. How can that be? If nothing can travel faster than light, and the age of the universe is about 13.7 billion years (that is when the big bang happened) how could there be anything visible beyond 13.7 billion light years? This question (and a 100s of others) pop-up every now and then to me. I am lazy enough to sit on them for quite some time until it starts disturbing me. And this one did! And it took just about 10 minutes to get the answer (or rather explanation). So the idea is that the space itself can expand. I knew space could bend, but now I know it can expand as well. Well, even if the space expanded at the speed of light, the radius of the universe should have been about 27.4 billion light years. But that is not the case. The answer to this is that space did not respect Albert Einstein and it decided to expand faster than the speed of light! Wow, isn’t that really cool? With this, even if someone says that the universe is a billion billion quadrillion light years in the diameter, you can’t question that, could you? I noticed that there is already the notion of *observable* universe. There are things beyond that, which we can’t see.
Could the mysterious and illusive dark matter, which is yet to be understood throw some light on it? To me space itself is nothingness (though it can be filled with something), and how could nothingness expand? What if the dark matter (or something else) is such that it makes light travel ridiculously slow when it passes through it? Wouldn’t it make all our distance observations overestimated? Well I know, there are enough reasons for this not being true, else someone would have brought it up for sure. But the point is that it looks to me, that in the last century or so we have created a complicated aura around all this. It has to be simpler. It really has to be. Otherwise it is not true.
Cosmology has always attracted and eluded me since childhood. I just wish that during my lifetime, we witness a spectacular theory or discovery which takes us a step ahead. Wouldn’t it be cool if we discover the mysterious dark matter? Or the fact that things can travel faster than light? Or something more beautiful than E=Mc2
And then, there’s quantum mechanics. I wouldn’t talk about it in this post at all. Einstein wouldn’t have liked it 🙂 | 0.820039 | 3.137823 |
The total eclipse of the sun of May 29, resulted in a striking confirmation of the new theory of the universal attractive power of gravitation developed by Albert Einstein, and thus reinforced the conviction that the defining of this theory is one of the most important steps ever taken in the domain of natural science. In response to a request by the editor, I will attempt to contribute something to its general appreciation in the following lines.
For centuries Newton’s doctrine of the attraction of gravitation has been the most prominent example of a theory of natural science. Through the simplicity of its basic idea, an attraction between two bodies proportionate to their mass and also proportionate to the square of the distance; through the completeness with which it explained so many of the peculiarities in the movement of the bodies making up the solar system; and, finally, through its universal validity, even in the case of the far-distant planetary systems, it compelled the admiration of all.
But, while the skill of the mathematicians was devoted to making more exact calculations of the consequences to which it led, no real progress was made in the science of gravitation. It is true that the inquiry was transferred to the field of physics, following Cavendish’s success in demonstrating the common attraction between bodies with which laboratory work can be done, but it always was evident that natural philosophy had no grip on the universal power of attraction. While in electric effects an influence exercised by the matter placed between bodies was speedily observed—the starting-point of a new and fertile doctrine of electricity—in the case of gravitation not a trace of an influence exercised by intermediate matter could ever be discovered. It was, and remained, inaccessible and unchangeable, without any connection, apparently, with other phenomena of natural philosophy.
Einstein has put an end to this isolation; it is now well established that gravitation affects not only matter, but also light.
Thus strengthened in the faith that his theory already has inspired, we may assume with him that there is not a single physical or chemical phenomenon—which does not feel, although very probably in an unnoticeable degree, the influence of gravitation, and that, on the other side, the attraction exercised by a body is limited in the first place by the quantity of matter it contains and also, to some degree, by motion and by the physical and chemical condition in which it moves.
It is comprehensible that a person could not have arrived at such a far-reaching change of view by continuing to follow the old beaten paths, but only by introducing some sort of new idea. Indeed, Einstein arrived at his theory through a train of thought of great originality. Let me try to restate it in concise terms. | 0.830956 | 3.633638 |
In his symphonic suite The Planets, Gustav Holst titled the 5th movement “Saturn, the Bringer of Old Age”. In human terms, a few thousand years would be pretty old, but secular scientists claim the planet is much older—about 4.5 billion years. Cassini, the spacecraft that has been orbiting Saturn since 2004, is making that age hard to believe. Independent lines of evidence argue for a much younger age.
Cassini-Huygens1 is the most advanced outer-planet spacecraft ever launched. In the 14 years I worked on the mission, I had opportunity to hear firsthand the struggles the world’s leading planetary scientists were having trying to keep Saturn old. I heard the predictions before launch, and I monitored the realities as torrents of data came in from Saturn, its moons and rings. Here is a short list of phenomena that put strong upper limits on the age of the Saturn system.
Enceladus. As reported in the June 2009 issue of this magazine, Enceladus emerged in 2005 as a serious challenge to old-age claims. This little moon, about the diameter of Arizona, was erupting water ice, dust and gas out of its south pole in powerful geysers. In March 2011, the problem got more and more difficult for long-agers: the heat emitted from Enceladus was measured at 15.8 gigawatts—ten times higher than earlier estimates.2 Papers in 2007 and 2008 admitted there is no known combination of factors that can keep this activity going for billions of years.3 The eruptions on Enceladus are indeed fountains of youth.
Main Rings. Saturn’s rings are not the placid, smooth raceways they appear to be. They are dynamic! The rings are constantly being bombarded by the solar wind, sunlight pressure, gas drag, internal collisions and micrometeorites. Scientists have even heard ‘ring tones’ in radio frequencies coming from meteorite impacts,4 and the visible ‘spokes’ may be their signatures. Yet the ice is remarkably clean compared to the predicted contamination from billions of years of micrometeorite pollution.5 And scientists recently found the trail of a billion-ton comet that must have hit the rings in the 1980s.6 How rare was that?
Scientists have struggled to keep the rings old by suggesting that the ice gets recycled somehow, or that the rings are more massive than they appear (this only prolongs the life of the B ring, the densest one).7 Most ring scientists, however, are resigned to the fact that the rings look young.5,7 To maintain their faith in billions of years, some propose that the rings formed long after Saturn by some lucky accident.8 Such an ad hoc explanation would require highly implausible conditions.
Faint Rings. In addition to the visible rings, Saturn has 1) a tenuous F ring continually plowed by Prometheus, one of the shepherd moons, 2) some fragile arcs in the G ring,9 3) a newly-discovered Phoebe ring orbiting Saturn backwards10 and 4) the tenuous E ring, created by the 10% of particles that escape Enceladus.11 On approach to Saturn, an ‘explosion’ in the E ring was detected (probably from Enceladus),12 dissipating as much mass as all the ring’s micron-sized particles combined in just four months.13 How often does this occur? If not rare, it represents a dynamic, destructive process. None of these delicate rings seem likely to persist for even a tiny fraction of the lifetime of the main rings—and the main rings already look young.
Saturn. Saturn has incredibly strong lightning storms, aurorae, a phenomenal vortex at its south pole that could almost swallow Earth,14 and a bizarre hexagon-shaped pattern of clouds at the north pole.15 Saturn’s magnetic field, furthermore, defies evolutionary dynamo theories by aligning nearly perfectly with its spin axis. The magnetosphere was even found to be loaded with charged particles from the Enceladus geysers, which in turn affects the field’s rotation.16 It’s remarkable that such a tiny moon has produced a measurable affect on a planet with 5 million times more mass—talk about the tail wagging the dog!
Iapetus. The Texas-sized moon Iapetus is as black as charcoal on its leading hemisphere, and as white as snow on the trailing side. This difference in brightness (albedo), noted by discoverer Jean-Dominique Cassini in 1672, left Voyager scientists still mystified in 1981. The mystery was finally solved by the Cassini mission, but what a solution! Close-encounter photos taken in September 2007 showed that the dark material almost certainly came from outside the moon; but even more astonishing, there’s a runaway migration of bright carbon dioxide ice due to heat absorbed by the dark material around it. This irreversible process causes the carbon dioxide ‘dry ice’ to sublimate and ‘hop’ to the trailing side and from pole to pole.17 About 12% of the migrating ice is lost to space each 29.5-year Saturnian orbit.18 Even if Iapetus started with a layer five kilometres (three miles) thick, it would be gone in just a third of the assumed 4.5 billion-year age of the solar system.
Another puzzle on Iapetus is a mountain range circling most of the equator that rises, at some points, 19 km (12 miles) above the surrounding plains. Trying to explain that in evolutionary terms requires an improbably rapid spin-down of Iapetus,19 or maybe a ring that collapsed. Rhea, a similar-size moon, shows scars on its equator that might be from ring collapse,20 but nothing as massive as the mountains on Iapetus.
Titan atmosphere. Like Earth, Saturn’s moon Titan has a largely nitrogen atmosphere, but unlike Earth, it has a large component of methane (what we call ‘natural gas’ on Earth). This methane provides Titan with a ‘space blanket’ that keeps the nitrogen in a gaseous form. But the methane in Titan’s atmosphere is irreversibly lost to space and to the surface. Since Voyager, atmospheric scientists have known that the solar wind is eroding the methane, converting it to hazes and other compounds that cannot change back to methane. When that erosion depletes the methane to a critical level, the entire nitrogen atmosphere should freeze out and collapse onto the surface catastrophically. Clearly, this has not happened. Atmospheric scientists have given Titan’s methane an upper age limit of 10 million years.21
Titan surface. The solar wind ionizes atmospheric methane, causing it to recombine into other hydrocarbons, primarily ethane (C2 H6). The ethane, which is liquid at Titan temperatures, should have rained down and accumulated over 4.5 billion years into a global ocean several kilometres thick, according to calculations made in the 1980s.22 The Huygens probe, however, landed in January 2005 with a thud on a moist lakebed. The historic landing provided ‘ground truth’ that the old-age predictions were wrong.
The project orbiter and lander found Titan girdled with dunes of dirty ice particles, riddled with river channels, but only scarred with half a dozen craters—astonishing for a large moon. Lakes were found in the north and south polar regions, but the largest one in the south was recently caught evaporating quickly, now that Saturn is moving from equinox to solstice.23 Cloudbursts of methane witnessed last year show weather cycles that have not left evidence of billions of years of hydrocarbon deposits.
These and other evidences put strong upper limits on the age of the Saturn system. Many of them top out at 100 million years, 10 million years, or less. That does not mean that Saturn is that old—it could be much younger, including the biblical timescale of thousands of years. To illustrate the problem for evolutionists, sometimes at presentations I have an assistant help me stretch out a 45-foot rope in front of the audience. If the rope represents the 4.5 billion year age of the solar system 100 million years is just one foot on that rope. What happened to the other 44 feet on the timeline? Did it even exist?
Bible-believers cannot prove from this evidence that Saturn fits within a Genesis timeframe, but consider: falsifying the 4.5 billion year age has the effect of simultaneously falsifying Darwinian evolution and the ‘geological timescale’. And with that comes a whole new set of questions—questions best addressed by the position of intelligent design, and best answered by the Word of the Creator Himself.
References and notes
- This spacecraft is made up of the NASA-designed Cassini orbiter, and the Huygens probe, by the European Space Agency. Return to text.
- JPL (Jet Propulsion Laboratory News Release), 3 March 2011, saturn.jpl.nasa.gov/news/newsreleases/newsrelease20110307; Creation-Evolution Headlines (CEH), 7 March 2011, creationsafaris.com/crev201103.htm#20110307b. Return to text.
- Icarus 187(2):569–570, 2007; www.space.com/5528-frigid-future-ocean-saturn-moon.html, 19 June 2008; CEH, creationsafaris.com/crev200806.htm#20080619a. Return to text.
- NASA Space Telescope discovers largest ring around Saturn, saturn.jpl.nasa.gov/, 6 October 2009. Return to text.
- JPL 12 December 2007, saturn.jpl.nasa.gov/news/newsreleases/newsrelease20071212, CEH, creationsafaris.com/crev200712.htm#20071213a, 13 December 2007. Return to text.
- JPL image caption 31 March 2011, photojournal.jpl.nasa.gov/catalog/PIA12820. Return to text.
- Cuzzi et al., An evolving view of Saturn’s dynamic rings, Science 327(5972):1470–1475, 2010; CEH, creationsafaris.com/crev201003.htm#20100319a, 19 March 2010. Return to text.
- JPL, saturn.jpl.nasa.gov/news/newsreleases/newsrelease20101212, 12 December 2010. Return to text.
- JPL, saturn.jpl.nasa.gov/news/newsreleases/newsrelease20080905, 5 September 2008. Return to text.
- JPL, saturn.jpl.nasa.gov/news/newsreleases/newsrelease20091006/, 6 October 2009; CEH, creationsafaris.com/crev200910.htm#20091007a, 7 October 2009. Return to text.
- JPL news, www.jpl.nasa.gov/news/features.cfm?feature=1597, 7 February 2008. Return to text.
- JPL, saturn.jpl.nasa.gov/news/cassinifeatures/feature20060629, 29 June 2006; CEH, creationsafaris.com/crev200607.htm#20060711a. Return to text.
- Science Daily, www.sciencedaily.com/releases/2004/12/041219140119.htm, 31 December 2004; CEH, creationsafaris.com/crev200407.htm#solsys122, 2 July 2004. Return to text.
- www.space.com/5183-saturn-storm-hurricane-features.html, 27 March 2008. Return to text.
- JPL, saturn.jpl.nasa.gov/news/newsreleases/newsrelease20091209, 9 December 2009. Return to text.
- JPL, saturn.jpl.nasa.gov/news/newsreleases/20081215enceladusactivity, 15 December 2008. Return to text.
- Southwest Research Institute News, www.swri.org/9what/releases/2009/Iapetus.htm 10 December 2009; CEH, creationsafaris.com/crev200912.htm#20091214a, 14 December 2009. Return to text.
- Palmer, E.E. and Brown, R.H., The stability and transport of carbon dioxide on Iapetus, Icarus 195(1):434–446, 2008; CEH, 5 May 2008, creationsafaris.com/crev200805.htm#20080505a. Return to text.
- Kerr, R.A., Planetary science: how Saturn’s icy moons get a (geologic) life, Science 311(5757):29, 2006; CEH, creationsafaris.com/crev200602.htm#20060206a, 6 February 2006; CEH, creationsafaris.com/crev200603.htm#20060301a, 1 March 2006. Return to text.
- Paul Schenk’s blog entry for 25 February 2010, stereomoons.blogspot.com/2010/02/rheas-blue-streaks-rings-and-other.html; JPL, saturn.jpl.nasa.gov/news/newsreleases/newsrelease20101007 7 October 2010; CEH, creationsafaris.com/crev201010.htm#20101020b 20 October 2010. Return to text.
- Space Science Institute press release, Feb 2009, ciclops.org/view/5471/cassini_finds_hydrocarbon_rains_may_fill_titan_lakes; personal communication with Dr. Sushil Atreya, 2001; Atreya’s paper: Titan’s Methane Cycle, Planetary and Space Science 54:1177–1187, 2006. See also Passage to a Ringed World (NASA SP-533, 1997, p. 33); CEH, creationsafaris.com/crev200902.htm#20090202a, 2 February 2009. Return to text.
- The New Solar System, 4th ed., Cambridge Press, 1999, p. 282. Return to text.
- Turtle et al., Shoreline retreat at Titan’s Ontario Lacus and Arrakis Planitia from Cassini Imaging Science Subsystem Observations, Icarus, S0019-1035(11)00054-6, 2011; CEH, creationsafaris.com/crev201102.htm#20110219a 19 February 2011. Return to text. | 0.890189 | 3.557221 |
Apr 08, 2013
External electric flux influences Earth’s climate
According to a recent press release, ten years of data analysis has revealed that cloud height changes over time in response to an electric field generated by “global thunderstorms”. Although Earth’s electric field is brought into the discussion, and the electric charge on small water droplets is mentioned, researchers admit to mysterious forces at play.
It is commonly believed that weather on Earth is driven by the Sun’s thermal influence on the atmosphere. As we rotate beneath our primary, gases and dust absorb solar radiation at varying rates and in varying degrees.
When any particular region heats up, the air expands and loses density, creating a relative low pressure area. Cooler air, being denser, will naturally flow into the bottom of the warm, low pressure region, causing an upwardly rotating convection cell to form. Most weather systems on Earth are thought to be based on that simple kinetic explanation: winds blow when the cooler, denser air flows into the warmer, buoyant air.
However, ions attract water in the atmosphere instead of through the commonly described process of neutral dust motes building up raindrops due to condensation. The dust hanging in the air becomes charged, making it more attractive to water vapor.
Electricity from the Sun speeds along massive Birkeland currents forming a circuit connecting the Sun with our planet. Since Earth is immersed in the Sun’s circuit, it has a vertical clear-air electric field of 50 – 200 volts per meter.
Water molecules in the atmosphere are tiny electric dipoles and are attracted to other water molecules, so they clump together and align within Earth’s “fair weather field.” The resulting polarized water droplets are subject to a levitating electric field between the ionosphere and the ground. The cloud height naturally changes in response to variations in the atmospheric electric field. Global thunderstorms are not the cause of that field, they are an effect: clouds short-circuit the atmospheric insulator over a height of many kilometers. The vertical winds in thunderstorms are principally electrically driven.
It was in September of 2006 that a major premise of Electric Universe theory was confirmed: Earth weather is electrically connected to the ionosphere. Since electricity always flows in a circuit, if the ionosphere connects to Earth’s magnetosphere then it connects to the circuits of the Solar System, as well.
The ionosphere is connected to the Sun by twisting filaments of electric current, so the lower levels of the atmosphere must also experience the Sun’s influence because of the additional circuit node that connects them with the ionosphere. Could these electric circuits linking the atmosphere with the Sun have anything to do with Earth’s climate in either the short or long term?
This leads to the more general idea that all weather may be influenced by the electrical connection between Earth and solar plasma. The larger view has only recently been considered, so experiments designed to verify the effect that charged particles have on Earth’s weather are now being conducted. It appears that they are having some success.
Electric Universe physicist Wal Thornhill wrote in 2004:
“If conventional theory fails to explain electrical storms it cannot be used to discount the results of ionization experiments. Instead, conventional theory suffers doubts about its basic plausibility. Weather experts have a limited view of the electrical nature of the Earth and its environment. The ‘enormous power input’ is freely available from the galaxy. That galactic electrical power drives the weather systems on all of the planets and even the Sun.” | 0.842854 | 3.494028 |
The following is an update from the SuperWASP Vairable Stars research team. Enjoy!
Welcome to the Spring 2020 update! In this blog, we will be sharing some updates and discoveries from the SuperWASP Variable Stars project.
What are we aiming to do?
We are trying to discover the weirdest variable stars!
Stars are the building blocks of the Universe, and finding out more about them is a cornerstone of astrophysics. Variable stars (stars which change in brightness) are incredibly important to learning more about the Universe, because their periodic changes allow us to probe the underlying physics of the stars themselves.
We have asked citizen scientists to classify variable stars based on their photometric light curves (the amount of light over time), which helps us to determine what type of variable star we’re observing. Classifying these stars serves two purposes: firstly to create large catalogues of stars of a similar type which allows us to determine characteristics of the population; and secondly, to identify rare objects displaying unusual behaviour, which can offer unique insights into stellar structure and evolution.
We have 1.6 million variable stars detected by the SuperWASP telescope to classify, and we need your help! By getting involved, we can build up a better idea of what types of stars are in the night sky.
What have we discovered so far?
We’ve done some initial analysis on the first 300,000 classifications to get a breakdown of how many of each type of star is in our dataset.
So far it looks like there’s a lot of junk light curves in the dataset, which we expected. The programme written to detect periods in variable stars often picks up exactly a day or a lunar month, which it mistakes for a real period. Importantly though, you’ve classified a huge number of real and exciting light curves!
We’re especially excited to do some digging into what the “unknown” light curves are… are there new discoveries hidden in there? Once we’ve completed the next batch of classifications, we’ll do some more to see whether the breakdown of types of stars changes.
An exciting discovery…
In late 2018, while building this Zooniverse project, we came across an unusual star. This Northern hemisphere object, TYC-3251-903-1, is a relatively bright object (V=11.3) which has previously not been identified as a binary system. Although the light curve is characteristic of an eclipsing contact binary star, the period is ~42 days, notably longer than the characteristic contact binary period of less than 1 day.
Spurred on by this discovery, we identified a further 16 candidate near-contact red giant eclipsing binaries through searches of archival data. We were excited to find that citizen scientists had also discovered 10 more candidates through this project!
Of the 10 candidate binaries discovered by citizen scientists, we were happy to be able to take spectroscopic observations for 8 whilst in South Africa, and we have confirmed that at least 2 are, in fact, binaries! Thank you citizen scientists!
Why is this discovery important?
The majority of contact or near-contact binaries consist of small (K/M dwarf) stars in close orbits with periods of less than 1 day. But for stars in a binary in a contact binary to have such long periods requires both the stars to be giant. This is a previously unknown configuration…
Interestingly, a newly identified type of stellar explosion, known as a red nova, is thought to be caused by the merger of a giant binary system, just like the ones we’ve discovered.
Red novae are characterised by a red colour, a slow expansion rate, and a lower luminosity than supernovae. Very little is known about red novae, and only one has been observed pre-nova, V1309 Sco, and that was only discovered through archival data. A famous example of a possible red nova is the 2002 outburst in V838 Mon. Astronomers believe that this was likely to have been a red nova caused by a binary star merger, forming the largest known star for a short period of time after the explosion.
So, by studying these near-contact red giant eclipsing binaries, we have an unrivalled opportunity to identify and understand binary star mergers before the merger event itself, and advance our understanding of red novae.
What changes have we made?
Since the SuperWASP Variable Stars Zooniverse project started, we’ve made a few changes to make the project more enjoyable. We’ve reduced the number of classifications needed to retire a target, and we’ve also reduced the number of classifications of “junk” light curves needed to retire it. This means you should see more interesting, real, light curves.
We’ve also started a Twitter account, where we’ll be sharing updates about the project, the weird and wacky light curves you find, and getting involved in citizen science and astronomy communities. You can follow us here: www.twitter.com/SuperWASP_stars
We still have thousands of stars to classify, so we need your help!
Once we have more classifications, we will be beginning to turn the results into a publicly available, searchable website, a bit like the ASAS-SN Catalogue of Variable Stars (https://asas-sn.osu.edu/variables). Work on this is likely to begin towards the end of 2020, but we’ll keep you updated.
We’re also working on a paper on the near-contact red giant binary stars, which will include some of the discoveries by citizen scientists. Expect that towards the end of 2020, too.
Otherwise, watch this space for more discoveries and updates!
We would like to thank the thousands of citizen scientists who have put time into this Zooniverse project. If you ever have any questions or suggestions, please get in touch.
Heidi & the SuperWASP Variable Stars team. | 0.882026 | 3.692778 |
The OSIRIS-REx mission is driven by five major science objectives. One of these objectives is to “Understand the interaction between asteroid thermal properties and orbital dynamics by measuring the Yarkovsky effect on a potentially hazardous asteroid [Bennu] and constrain the asteroid properties that contribute to this effect.” Read on to find out what this means and how we will get it done.
What is the DEWG?
In order to effectively manage a science team containing over 80 people, I have divided them up into twelve different working groups. Each group is assigned a subset of our mission science requirements. Based upon these assignments, the working groups develop their section of the Science Implementation Plan – our guidebook for how to achieve OSIRIS-REx mission success. The working group responsible for characterizing the orbital variation of Bennu over the course of Solar System history is the Dynamical Evolution Working Group, or DEWG for short.
The DEWG is tasked with reconstructing the orbital history of Bennu from the main-asteroid belt to near-Earth space and on into the future. One of the DEWG’s main objectives is to constrain the short-term dynamical evolution of Bennu. Most importantly, they constrain the timeline for Bennu-Earth close approaches in the past and future. They are using this information to understand the impact hazard that Bennu represents and define measurement by the spacecraft that will further refine the probability of impact.
How Do We Know Where Bennu Is?
The first step in reconstructing Bennu’s history and predicting her future is to accurately determine her present orbit. The science of determining a celestial object’s orbit based on telescopic observations is called astrometry. Bennu has an orbital period that results in a close pass with the Earth every six years. It is only during these close approaches that Bennu becomes bright enough to be observed with ground-based telescopes or with the Planetary Radar System. Bennu was discovered on September 11, 1999 by the Lincoln Near-Earth Asteroid Research (LINEAR) survey. She reappeared in the sky in 2005 and again in 2011. Between September 11, 1999 and January 20, 2012, 561 telescopic and 29 radar astrometric measurements were made by a number of professional and amateur astronomers from around the world. As a result, the orbit solution that we have established for Bennu is now the most precise in the asteroid catalog. For example, the uncertainly on her semi-major axis (the longest dimension of her orbital ellipse) is 6 meters out of 168,505,699.049 kilometers. This is equivalent to measuring the distance from New York to Los Angeles with accuracy smaller than 1/64th of an inch!
Where Will Bennu Be in the Future?
Once we have determined her current orbital state, the next step is to predict where Bennu will be in the future and where she has been in the past. This seems like a simple task – just use Kepler’s three laws of planetary motion, run the calculations backward and forward in time, and you are done – right? Wrong! When calculating the orbital trajectory of Bennu we need to include not only the gravitational effect of the Sun, but also that of the eight planets, the Moon, Pluto, and any asteroids that might perturb her orbit. For the asteroids, we first included the four largest asteroids (1 Ceres, which is officially a dwarf planet, 2 Pallas, 4 Vesta, and 10 Hygeia). We then computed and included the orbits for the next 12 largest main-belt asteroids. Finally, we added nine more asteroids, which we selected according to an analysis of which ones could most significantly influence the orbit of Bennu.
A Planet’s Shape Can Also Affect Bennu’s Orbit
It is not just the mass of the planets that affect Bennu’s orbit – but also their shape. When Bennu is near the Earth we have to model the gravitational perturbation due to the Earth’s oblateness (i. e. the Earth has a round shape that is flattened at the poles). We found that unless the effect was included, whenever Bennu is closer than 0.3 AU, there is a modest but discernible error on the orbit determination and propagation.
Don’t Forget Albert!
Einstein showed that Kepler’s laws, as generalized in Newton’s Law of Universal Gravitation is only true as long as the strength of the gravitational field is weak. As it turns out, we have to include the effects of Einstein’s General Relativity to predict Bennu’s orbit with the same accuracy as our astrometric measurements. We used a full relativistic force model including the contribution of the Sun, the planets, and the Moon. The relativistic effects of the Sun are very important. In addition, we found that the Earth’s relativistic terms are responsible for a significant variation because of short-range effects during Bennu’s close approaches to the Earth in 1999 and 2005.
Surely Sunlight Can’t Push an Asteroid Around
Finally, we have to include the Yarkovsky effect to fit an orbit for Bennu. This slight non-gravitational acceleration arises because of the way Bennu absorbs and re-emits the energy from the Sun. Bennu receives the majority of solar energy at noon, local asteroid time. She hangs on to this energy as a result of a property called the thermal inertia of her surface. The energy is then re-radiated back into space as heat sometime during Bennu’s afternoon. The radiation of thermal energy either accelerates or decelerates the asteroid, changing her orbital path.
So, Where is my Asteroid?
As a result of all this hard work, we now know where Bennu has been and where she is headed between 1654 and 2135. In 2135 Bennu will pass 300,000 km (186,000 miles) over the surface of the Earth and be closer than the Moon. We don’t know enough about Bennu to accurately predict what will happen to her orbit as a result of this encounter. Beyond 2135, our calculations are statistical in nature. We do know that Bennu has a high probability (~1 in 3,000 chance) of impacting the Earth soon after this, sometime in the 2175 – 2196 time frame.
The work on Bennu’s trajectory is lead by Steve Chesley – a member of my Science Team with prime responsibility for calculating Bennu’s orbit. Steve is a member of the JPL Near-Earth Object Program Office – whose job it is to keep an eye on all of the space rocks that may be hazardous to the Earth. The DEWG is leading many other exciting studies of Bennu’s past and future. Stay tuned for more information! | 0.893308 | 3.851854 |
Astronomers have named interstellar asteroid ’Oumuamua and found it to be rich in organic molecules.
Astronomers are now certain that the mysterious object detected hurtling past our sun last month is indeed from another solar system. They have named it 1I/2017 U1(’Oumuamua) and believe it could be one of 10,000 others lurking undetected in our cosmic neighbourhood.
The certainty of its extraterrestrial origin comes from an analysis that shows its orbit is almost impossible to achieve from within our solar system.
Its name comes from a Hawaiian term for messenger or scout. Indeed, it is the first space rock to have been identified as forming around another star. Since asteroids coalesce during the process of planet formation, this object can tell us something about the formation of planets around its unknown parent star.
The latest analyses with ground-based telescopes show that ’Oumuamua is quite similar to some comets and asteroids in our own solar system. This is important because it suggests that planetary compositions like ours could be typical across the galaxy.
It is thought to be an extremely dark object, absorbing 96% of the light that falls on its surface, and it is red. This colour is the hallmark of organic (carbon-based) molecules. Organic molecules are the building blocks of the biological molecules that allow life to function.
It is widely thought that the delivery of organic molecules to the early Earth by the collision of comets and asteroids made life here possible. ’Oumuamua shows that the same could be possible in other solar systems.
Its characteristics have been published by two independent groups of astronomers. The first group, led by Karen Meech, University of Hawaii, also found that ’Oumuamua was extremely elongated and roughly 400 metres long. Using the European Southern Observatory’s Very Large Telescope(VLT) they also found that it rotated once every 7.3 hours.
The other group of astronomers, led by David Jewitt, University of California Los Angeles, estimated how many other interstellar visitors like it there might be in our solar system.
Surprisingly, they calculate that another 10,000 could be closer to the Sun than the eighth planet, Neptune, which lies 30 times further from the Sun than the Earth. Yet these are currently undetected.
Each of these interstellar interlopers would be just passing through. They are travelling too fast to be captured by the gravity of the Sun. Yet it still takes them about a decade to cross our solar system and disappear back into interstellar space.
If this estimate is correct, then roughly 1,000 enter and another 1,000 leave every year – which means that roughly three arrive and three leave every day.
Using robotic telescopes such as Pan-STARRS, the one that detected ’Oumuamua, to look for asteroids is a priority for astronomers as they concentrate on discovering potentially hazardous objects that could impact Earth.
Imminent upgrades to these survey telescopes and improvements in data processing techniques mean that astronomers will soon be able to detect smaller and fainter objects. They expect a number of these to be interstellar interlopers like ’Oumuamua. | 0.904135 | 3.914611 |
Located in the constellation of Hercules, about 230 million light-years away, NGC 6052 is a pair of colliding galaxies. They were first discovered in 1784 by William Herschel and were originally classified as a single irregular galaxy because of their odd shape.
However, we now know that NGC 6052 actually consists of two galaxies that are in the process of colliding. This particular image of NGC 6052 was taken using the Wide Field Camera 3 on the NASA/ESA Hubble Space Telescope.
A long time ago, gravity drew the two galaxies together into the chaotic state we now observe. Stars from within both of the original galaxies now follow new trajectories caused by the new gravitational effects.
However, actual collisions between stars themselves are very rare as stars are very small relative to the distances between them (most of a galaxy is empty space). Eventually, the galaxies will fully merge to form a single, stable galaxy.
Our own galaxy, the Milky Way, will undergo a similar collision in the future with our nearest galactic neighbor, the Andromeda galaxy. However, this is not expected to happen for around 4 billion years.
This object was previously observed by Hubble with its old Wide Field and Planetary Camera 2 (WFPC2). That image was released in 2015.
Provided by: Rob Garner, NASA’s Goddard Space Flight Center [Note: Materials may be edited for content and length.]
Like this article? Subscribe to our weekly email for more! | 0.863707 | 3.186812 |
Pluto has long been viewed as a distant, cold and mostly dead world, but the first spacecraft to pass by it last year revealed many surprises about this distant dwarf planet.
Data from the New Horizons flyby finished downloading to Earth in October, and while it will take many years for scientists to complete their inventory and model the results, early studies offer intriguing hints of its complex chemistry, perhaps even some form of pre-biological processes below Pluto’s surface. Complex layers of organic haze; water ice mountains from some unknown geologic process; possible organics on the surface; and a liquid water ocean underneath — all of these features point to a world with much more vibrancy than scientists have long presumed.
“The connection with astrobiology is immediate — it’s right there in front of your face. You see organic materials, water and energy,” said Michael Summers, a planetary scientist on the New Horizons team who specializes in the structure and evolution of planetary atmospheres.
In first looking at the images of Pluto, Summers was reminded of a world he has studied for decades while working at George Mason University. Titan, an icy orange colored moon of Saturn, is the only moon in the Solar System with a substantial atmosphere and a liquid (methane) hydrological cycle. It has hydrocarbon chemistry, including ethane and methane lakes that have compounds that may be precursors to the chemistry required for life.
Unlike Titan, Pluto’s atmosphere is thin and sparse, with haze reaching out at least 200 kilometers (125 miles) above the surface, at least ten times higher than scientists expected. But above 30 km (19 miles) Pluto displays a similar paradox to Titan with condensation happening in a region that’s too warm in temperature for haze particles to occur.
NASA’s Cassini spacecraft saw the same oddity in the highest reaches of Titan’s atmosphere (the ionosphere) at about 500 to 600 kilometers above the surface (roughly 310 or 370 miles). Through modeling, scientists determined that the condensation is partially the result of Titan’s photochemistry, whereby ultraviolet sunlight breaks down methane, triggering the formation of hydrocarbons.
“This haze formation is initiated in the ionosphere, where there are electrically charged particles (electrons and ions),” Summers said. “The electrons attach to the hydrocarbons and make them stick together. They become very stable, and as they fall through the atmosphere they grow by other particles sticking to them. The bigger they are, the faster they fall. On Titan, as you go down in the atmosphere the haze particles get more numerous and much larger than on Pluto.”
In retrospect, Summers said it shouldn’t have been too much of a surprise that Pluto likely has the same process. Like Titan, it has a nitrogen atmosphere with methane as a minor component. The main difference, however, is Pluto’s atmosphere is just 10 millibars at the surface, compared to Titan’s 1.5 bar. (A bar is a metric unit of pressure, with 1 bar equal to 10,000 pascal units, or slightly less than the average atmospheric pressure on Earth at sea level.) The atmospheric pressure difference of the two bodies also affects the shape of the haze particles as Titan’s particles taking much longer to fall to the surface and ultimately become spherical, while Pluto’s haze particles fall more rapidly and grow into fractals.
With the possible production of hydrocarbons and nitriles (another organic molecule) on Pluto, even more interesting pre- chemistry for life could take place, Summers said. “You can start building complex pre-biotic molecules,” he said. An example is hydrogen cyanide, possibly a key molecule leading to prebiotic chemistry.
What’s also abundant on Titan are tholins, complex organic compounds created when the Sun’s ultraviolet light strikes the haze particles. It’s rare on Earth, but common on Titan and may have contributed to its orange color. There is also a reddish hue on parts of Pluto’s surface, which could be from a layer of tholins, Summers said.
His quick calculation estimates these tholins could be 10 to 30 meters thick, providing more organic material per square meter than a forest on Earth. This material may also change its chemical composition as cosmic rays (high-energy radiation particles) strike the surface.
Intriguingly, reddish material was also spotted near Pluto’s ice volcanoes, or calderas. It’s possible that the dwarf planet could have a subsurface ocean similar to that suspected on Titan, Saturn’s Enceladus and Jupiter’s Europa. These moons, however, have a tidal source of energy within, created by orbiting their huge central planets and interacting gravitationally with other moons. Pluto is bereft of such heating, but it’s possible that radioactivity in its interior could be keeping the inside liquid, Summers said.
“These are the things you need for life: organics, raw material and energy,” Summers said.
While it’s a stretch right now to say Pluto is hospitable for life, Summers said he is looking forward to doing more modeling. “I’ve been studying Pluto all my life, and never expected to talk about these things being there.”
Originally published on Seeker. | 0.90766 | 4.062785 |
FIFTH BRIEF: Flawed Hypothesis of Hubble’s Law
The definition of velocity
as a differential and its relationship to the Doppler Effect is the key to a mathematical fallacy that led to Hubble’s Law and the incorrect premise of the Big Bang Theory.
Edwin Hubble discovered galaxies he didn’t know what they were, so he performed a “spectrum analysis.” He found a galaxy’s spectral lines indicated a hydrogen light source, which is reasonable since hydrogen is the most abundant light
source in the Universe. However, there was a bit of a problem. The spectral lines were shifted a little toward the red end of the visible spectrum. That is, the wavelengths were ever so slightly elongated. This
wavelength elongation of course is known as the “red shift” of light emitted from distant celestial bodies.
of this wavelength elongation (red-shift) was assumed to be the Doppler Effect (or Doppler Shift). In short, this is the phenomenon that light wavelengths will elongate relative to an observer, if the light source is moving away from the observer. Hubble called this assumed outward motion the “recession velocity”
of the galaxy. Further observations of more galaxies showed the red shift is the norm in all directions, so the Universe appears to be expanding (blowing up like a big balloon).
it’s not an unreasonable assumption that the elongation of light wavelength (red shift) is the Doppler Effect that in turn is caused by recession velocity. However, it was the next two discoveries by Hubble that should have indicated a flaw in
First, Hubble found that this wavelength elongation (Doppler Effect) is directly proportional to distance.
That is, the farther away a galaxy, the greater the Doppler Effect.
Unfortunately, Hubble (along with the entire scientific community) failed to realize this doesn’t make sense.
The Doppler Effect is proportional to speed, but is not proportional to distance.
Secondly, after further study of more galaxies, Hubble found that the ratio of a galaxy’s recession velocity to its distance appears to be a constant. Mathematically it looks like this: v = HoD (Hubble’s
Law). Where v is the recession velocity of a galaxy, Ho is the Hubble Constant and D is the distance to the galaxy.
Only problem is Hubble’s Law doesn’t make sense either. You cannot derive velocity (or acceleration) by multiplying a constant by a static distance. A static distance and a constant are scalars, and velocity is
a vector. Velocity is a ratio of two differentials (a change in length with respect to a change in time). Any physicist should know that there is no mathematical relationship between a moving object’s static distance (at an instant of time) and its velocity. This is a prime example of a violation of Scientific Method with an “invented equation”
that is forced to fit an erroneous empirical definition.
So how can this be? How can the recession velocity of a galaxy be proportional to the galaxy’s distance? How
can the Doppler Effect vary with respect to distance?
The answer is obvious. The cause of the red shift is not the Doppler Effect. The red shift is caused by the variance or skew of the nonlinear space continuum.
So here again, over 60 years ago Einstein got it right (and the scientific community still doesn’t get it). | 0.816033 | 4.144974 |
Evidence for Dust Grain Growth in Young Circumstellar Disks
arXiv:astro-ph/0104445v1 27 Apr 2001
Henry B. Throop1 , John Bally, Larry W. Esposito, Mark J. McCaughrean Submitted to Science: 16 January 2001 Revised: 19 April 2001
Hundreds of circumstellar disks in the Orion nebula are being rapidly destroyed by the intense ultraviolet radiation produced by nearby bright stars. These young, million-year-old disks may not survive long enough to form planetary systems. Nevertheless, the first stage of planet formation – the growth of dust grains into larger particles – may have begun in these systems. Observational evidence for these large particles in Orion’s disks is presented. A model of grain evolution in externally irradiated protoplanetary disks is developed and predicts rapid particle size evolution and sharp outer disk boundaries. We discuss implications for the formation rates of planetary systems. The growth of dust grains orbiting young stars represents the first stage of planet formation. However, stars born in massive star-forming regions such as the Orion nebula are heated by intense ultraviolet (UV) radiation from nearby O and B stars, and the gas and dust in their disks can be lost in less than 105 years. Planet formation in such environments may therefore be inhibited if it requires substantially longer than this time. But, if growth to large particles can occur before removal of the gas and small particles, planets may nevertheless form from these disks. In this paper, visual and near-infrared wavelength images obtained with the Hubble Space Telescope (HST) are used to show that particles in Orion’s largest disk have grown to radii larger than 5 µm. Furthermore, the absence of millimeter-wavelength emission may provide evidence that grains have grown to sizes larger than a few millimeters. We develop a grain evolution model incorporating the effects of photo-ablation that demonstrate that the timescale for grain growth can be shorter than the photoevaporation time. It is thought that the majority of stars in the Galaxy form in photo-evaporating regions like the Orion nebula; if this is true, then giant planets and Kuiper belts of icy bodies around stars are probably rare unless they are formed very rapidly. Solar system-sized circumstellar disks in the Orion nebula were first inferred from radio observations of dense ionized regions surrounding young low-mass stars. HST subsequently yielded images of extended circumstellar material surrounding over half of the observed 300 young low-mass stars in core of the Orion nebula [6, 7]. Most of these ‘proplyds’ consist of comet-shaped ionized envelopes pointing directly away from the brightest stars in the Nebula [8, 9]. 1 Campus Box 392 / LASP, University of Colorado, Boulder, CO 80309-0392. Present address: Southwest Research Institute, 1050 Walnut St. Ste. 426, Boulder, CO 80302. [email protected]
Proplyds are believed to contain evaporating circumstellar disks and over 40 disks have been resolved on HST images. More than 25 are found inside ionized envelopes while 15 are seen purely in silhouette against the background light of the nebula. Assuming disk masses ∼ 0.01 − 0.05M⊙ (1M⊙ = 1 solar mass) , external radiation erodes disks in the central 1 pc of the Orion nebula on 104 to 105 yr timescales [3,10]. Soft UV photons (91 nm < λ < 200 nm) from nearby massive stars heat the disk surface layers to about 1000 K. Gas heated above the local escape velocity is lost from the disk at loss rates of M˙ ≈ 10−7 to 10−6 M⊙ yr−1 [2, 10] and forms the cometary ‘proplyds’ surrounding many of Orion’s young stars. Dust grains will be entrained in the escaping neutral outflow where the gas drag forces on them exceed the force of gravity; the small ionized outflow component has negligible effect on grain loss. Entrained dust has been observed just inside the ionization fronts in several proplyds, but not considered in previous modeling. The properties of the grains in Orion’s circumstellar disks can be probed by the wavelength-dependence of the attenuation of the background nebular light that filters through the translucent disk edges. Standard interstellar2 grains with radii of 0.1-0.2 µm scatter shorter wavelength visible light more efficiently than longer wavelengths. Therefore, disks containing predominantly small interstellar grains become more transparent with increasing wavelength. On the other hand, the opacity of disks containing predominantly large grains (larger than several times the wavelength) will be independent of the wavelength. While small grains ‘redden’ transmitted light, large grains do not alter its color, rendering the translucent portion of the disk ‘grey.’ The largest circumstellar disk in the Orion nebula, 114-426, is seen in silhouette against background nebular light. This nearly edge-on disk (the central star is occulted by the disk) has a radius of ∼ 550 astronomical units (AU) and a resolved translucent outer edge roughly 200 by 200 AU in size at its northeast ansa (Fig. 1). Grain properties in this region can be probed by the attenuation of the bright background 1870 nm Paschen α and 656 nm Hα lines. Because both these lines originate from recombinations of ionized hydrogen, the brightness ratio between these two lines is relatively constant over the extent of 114-426. We used the Planetary Camera of HST’s WFPC2 instrument to obtain a set of four dithered 400 second Hα exposures of 114-426 on January 11, 1999, resulting in reduced images with an angular resolution of 0.07”, or 30 AU. We also used HST’s NICMOS1 camera to obtain a 640 second Paschen α exposure on 26 February 1998 at resolution of 0.16”. In order to compare these images at identical resolutions, we convolved the Hα image with a synthetic Paschen α point-spread function (PSF), and the Paschen α image with an Hα PSF. 2 The term ‘interstellar’ refers to the population of small, primordial dust grains in the Orion nebula that have not been processed in a circumstellar disk.
Linear slices through the disk midplane at 656 nm and 1870 nm show that the opacity profiles of the translucent western edge of 114-426 are indistinguishable (Fig. 2). Thus, background light is not ‘reddened’; dust at the disk edge is ‘grey’ to a level of ∼ 5% between 656 nm and 1870 nm. The mean extinction of the translucent ansa of the 114-426 disk at these wavelengths can be compared to the reddening produced by observations of interstellar grains along several typical lines-of-sight (Fig. 3). The 114-426 disk’s translucent edge is achromatic and can not be fit by any standard interstellar extinction law. The standard interstellar extinction curve indicates that the opacity should be 5-10 times lower at 1870 nm than at 656 nm. This result depends only weakly on composition, grain shape, or the presence of fractal aggregates [14, 15]. The observed grey opacity indicates that extinction is dominated by particles larger than 5 µm in radius, 25-50 times larger than typical interstellar grains. In contrast to the NE ansa, the disk’s polar halo region decreases in size with wavelength, indicating a suspended population of small particles above the disk poles. Although previous observations of 114-426 indicated a decrease in disk size by 20% from 656 nm to 1870 nm, that result may have reflected poor signal/noise ratio in the earlier 1870 nm observations . The lack of millimeter-wavelength emission places additional constraints on grain sizes. We observed six Orion nebula disks, including 114-426, with the Owens Valley Radio Observatory (OVRO) millimeter wavelength interferometer at λ = 1.3 mm continuum. None were detected, implying mass limits of Mdisk < 0.020M⊙ under the assumption of an interstellar emissivity of 2 × 10−2 cm2 g−1 . However, in re-visiting our analysis of these data, we note the possibility that grains have grown larger than a few millimeters and thus the standard emissivity may underestimate the mass. The models described below predict that particles grow to larger than 1 mm throughout the disk in less than 105 yrs, causing an emissivity of 2 × 10−3 cm2 g−1 and implying disk masses as large as 0.2 M⊙ . We have developed a numerical model to explore grain behavior within photo-evaporating disks. Our model includes (i) grain growth due to mutual collisions and accumulation of ice mantles, (ii) coupling and loss of small grains entrained in UV photo-evaporation induced outflow, [3, 10] and (iii) photosputtering of ices. The grain density is assumed to remain constant as grains collide and stick within turbulent eddies produced by heat escaping from the disk midplane. Vertical and azimuthal symmetry is assumed and the abundance and size distribution of ice, silicate, and gas are tracked separately at each time-step. Our disk has an initial mass of 0.1 M⊙ , with a grain size distribution identical to interstellar dust. The model starts when the ionizing source turns on, and stops when the disk thermal optical depth has dropped below unity and can no longer sustain convection, typically in a little over 105 yr. After convection stops, grain growth is dominated by processes such as settling and gravitational interactions. These processes are not considered here. The
model does not simulate 114-426 in its current, non-photo-evaporating state3 ; rather, it simulates the 114-426 disk as it would appear placed near the Orion nebula core at a distance 0.1 pc. Grains grow most rapidly in the center of the model disk (Fig. 4a) where the highest densities and temperatures are found and photo-evaporation does not operate. The growth rate decreases with distance from the central star; grain sizes reach r = 1 m at 10 AU and r = 1 mm at 500 AU in 105 yr. In the outer disk, small (< 1 mm) grains are entrained in the photo-evaporative flow from the disk surface and lost from the system, decreasing the optical depth (Fig. 4b). After 105 yr, few particles remain in the disk outward of 40 AU. At the transition between these ‘grain growth’ and ‘grain loss’ regimes, an edge populated by large, cm-sized particles is left behind. After the silicate population has stabilized, photo-sputtering continues to reduce ice particle sizes and remove gas, and nearly all ice and gas are removed by 106 yr. Only silicates that grow large enough (r > 1 mm) to resist photo-evaporative entrainment are retained. Ices do not survive and only rocky planets, planetary cores, or asteroids can form. In the standard planetary formation model, giant planets such as Jupiter form by accreting hydrogen and helium rich gas from the disk onto a large rocky core. In Orion-like environments, there may not be time to grow the requisite cores before loss of the gas since Jupiter’s formation would require 106 − 107 yr. If giant planets form in Orion-like systems, they must do so before disk photo-evaporation. One viable mechanism for rapid formation of giant planets is gravitational collapse, which has been postulated to occur in disks with Mdisk > 0.13M⊙ on 103 year time-scales around solar-mass stars. Icy Kuiper belt objects and comets are believed to have formation time-scales of 108 − 109 yr. Thus, these objects are also difficult to form in Orion-like environments. The architectures of any new planetary systems that might form in Orion are likely to be different from that of our Solar system. The evidence for large particles in 114-426 complements several previous studies of particles in young disks. The reflected-light near-infrared spectrum of the disk orbiting HR4796A provides evidence for particles with radii larger than 2-3 µm. Several disks in NGC2024 and Taurus reveal relatively flat sub-millimeter spectra that may indicate large grains. However, near-IR observations of the disk in HH30 show normal dust opacities and no evidence for grain growth and sub-mm observations of the HL Tau disk are inconclusive. Grain growth in disks appears to depend strongly on their environment. The majority of young stars in the Milky Way galaxy appear to have formed in large, dense clusters like the Orion nebula, rather than in smaller, dark clouds 3 114-426 is thought to show no photo-evaporation because it is outside the Orion core’s Str¨ omgren sphere and thus receives no soft UV flux; we note the possibility that it may not be photo-evaporating today because all gas has already been lost in previous photo-evaporative episodes, and it is a pure dust disk.
such as Taurus-Auriga. Within large clusters, the majority of stars form near massive stars where their disks can be rapidly destroyed. Thus, planet formation models must be revised to consider the destructive effects of these environments. We present evidence for large gains in one Orion disk. This creates the possibility that planetary system with architectures different from our own Solar system may nonetheless form in such hazardous environments.
References S. V. W. Beckwith, T. Henning, Y. Nakagawa, In V. Mannings, A. P. Boss, S. S. Russell, editors, Protostars and Planets IV . U. Ariz. Pr. (2000). C. J. Henney and C. R. O’Dell, Astron. J. 118, 2350 (1999). H. Stoerzer and D. Hollenbach, Astrophys. J. 495, 853 (1998). F. M. Walter, J. M. Alcala, R. Neuhauser, M. Sterzik, S. J. Wolk, In V. Mannings, A. P. Boss, S. S. Russell, editors, Protostars and Planets IV . U. Ariz. Pr. (2000). E. Churchwell, M. Felli, D. O. S. Wood, M. Massi, Astrophys. J. 321, 516 (1987). C. R. O’Dell, Z. Wen, X. Hu, Astrophys. J. 410, 696 (1993). M. J. McCaughrean and C. R. O’Dell, Astron. J. 111, 1977 (1996). M. J. McCaughrean et al., Astrophys. J. 492, L157 (1998). J. Bally, C. R. O’Dell, M. J. McCaughrean, Astron. J. 119, 2919 (2000). D. Johnstone, D. Hollenbach, J. Bally, Astrophys. J. 499, 758 (1998). H. B. Throop, Light scattering and evolution of protoplanetary disks and planetary rings, PhD thesis University of Colorado (2000). S.-H. Kim, P. G. Martin, P. D. Hendry, Astrophys. J. 422, 164 (1994). M. J. McCaughrean, K. R. Stapelfeldt, L. M. Close, In V. Mannings, A. P. Boss, S. S. Russell, editors, Protostars and Planets IV . U. Ariz. Pr. (2000). K. Lumme, J. Rahola, J. W. Hovenier, Icarus 126, 455 (1997). M. I. Mishchenko, L. D. Travis, D. W. Mackowski, J. Quant. Spec. Rad. Trans. 55, 535 (1996). J. Bally, L. Testi, A. Sargent, J. Carlstrom, Astron. J. 116, 854 (1998). L. G. Mundy, L. W. Looney, E. A. Lada, Astrophys. J. 452, L137 (1995). 5
H. Mizuno, W. J. Markiewicz, H. J. Voelk, Astron. & Astrophys. 195, 183 (1988). M. S. Westley, R. A. Baragiola, R. E. Johnson, G. A. Baratta, Nature 373, 405 (1995). B. Dubrulle, G. Morfill, M. Sterzik, Icarus 114, 237 (1995). J. B. Pollack et al., Icarus 124, 62 (1996). A. P. Boss, Science 276, 1836 (1997). P. Farinella, D. R. Davis, S. A. Stern, In V. Mannings, A. P. Boss, S. S. Russell, editors, Protostars and Planets IV . U. Ariz. Pr. (2000). G. Schneider et al., Astrophys. J. Lett. 513, 127 (1999). A. E. Visser, J. S. Richer, C. J. Chandler, R. Padman, Month. Not. Royal Astron. Soc. 301, 585 (1998). V. Mannings and J. P. Emerson, Month. Not. Royal Astron. Soc. 267, 361 (1994). A. M. Watson, K. R. Stapelfeldt, J. E. Krist, C. J. Burrows, Astrophys. J. 1, 1 (2001). J. A. Cardelli, G. C. Clayton, J. S. Mathis, Astrophys. J. 345, 245 (1989). H. Stoerzer and D. Hollenbach, Astrophys. J. 515, 669 (1999). H. W. Yorke, P. Bodenheimer, G. Laughlin, Astrophys. J. 411, 274 (1993). Acknowledgments: This research was funded by the Cassini project, the NASA Astrobiology Institute, NASA grants NAG5-8108 and GO-06603.01-95A, DLR grant number 50–OR–0004 and European Commission Research Training Network RTN1–1999–00436. We thank C. Campbell, N. Turner, and two anonymous reviewers for their comments.
Figure 1: Images of the 114-426 disk in Orion at 656 nm (left) and 1870 nm (right) obtained with HST. The images have been rotated and scaled to the same spatial scale, and are shown at full resolution before convolving as described in the text. The maximum and minimum background intensities have been normalized to unity and zero respectively. Both images were processed and calibrated through the standard HST data pipeline. Figure 2: One-dimensional intensity slices along the major axis of the 114426 circumstellar disk. Both images have been convolved with their complementary PSF’s to produce images at matched angular resolutions. The disk’s SW ansa is consistent with a sharp disk edge. In contrast, the disk’s translucent NE ansa is spatially extended over at least 4 resolution elements. The indistinguishable profiles at the two wavelengths indicates that transmission through the translucent portion of the disk is achromatic, and the disk is dominated by particles larger than 5µm. Figure 3: The wavelength dependence of the light transmitted through the translucent portion of the 114-426 disk, compared to the range of standard observed interstellar reddening laws. The 656 and 1870 nm data points for the NE ansa of 114-426 is marked. All data have been normalized to the V photometric band. The points for 114-426 show that the extinction is grey and can not be represented by any interstellar extinction law. The error bar on the 1870 nm point shows 3 σ errors, dominated by spatial variations in the background light at both wavelengths, and flat-field artifacts in the 1870 nm image. A indicates the extinction in magnitudes at wavelength λ. The color ratio Rv is defined as Av /(Av − AB ). Other single letters indicate the standard photometric bands. The stellar data were taken from . Figure 4: A model for grain growth in a photo-evaporating circumstellar disk exposed to a UV radiation field typical of the Orion Nebula. The initial grain size distribution is that of interstellar dust. a) The evolution of the particle size with time at several radial distances. Solid lines correspond to radial distances Ri = exp(2.31 + 0.43ni ) AU. The outermost several bins do not grow significantly and their lines appear superimposed on each other. Particles grow quickly at the inner edge due to high collision velocities, high gas densities, and slow loss processes. Growth is terminated when infrared optical depth drops below unity, inhibiting convection. b) The evolution of the radial profile of the disks opacity as viewed from the disk axis. Grains at the outer edge are removed by the photo-ablation flow while grains in the inner disk grow rapidly. These two processes create a disk populated by large particles. Time-steps for the solid lines correspond to times ti = exp(5.1 + 0.24ni ) yr. The input parameters used here are representative of photo-evaporative conditions 0.1 pc from the Orion nebula core. [10, 29] The following disk parameters are assumed: The surface density declines with disk radius as Σ ∼ R−3.5 , the vertical height scales as z = R/10, the sputtering rate is given by (dr/dt)s = 1 µm yr−1 , and the sticking efficiency is ǫ = 0.1. The outflow column density is n0 = 3 × 1022 cm−2 , higher than the 7
3 × 1021 cm−2 of to account for deeper UV penetration due to the large grains in the disk. The viscosity parameter is α = 10−2 , the outflow temperature at it base is To = 1000K, the central star mass is Ms = 1M⊙ , the disk inner and outer radii are Rin = 10 AU and Rout = 500 AU, and the grain density is ρ = 1 g cm−3 .
Aλ / A V
BD+56 524 HD 48099 Herschel 36 Orion 114−426
L KH J
1/ λ ( µm ) −1 | 0.898773 | 3.955033 |
the problem with lorentz transformation is that during calculations the frames of reference are changed arbitrarily to fit the presumtions. if you stick to one reference frame from the beginning till the end, then there will be no time dilation. the space-time interval comes directly from the lorentz transformation, and if i remember correctly, big part of the relativity conclusions by einstein was based on the lorentz transformation. you see where it is heading to?!
the errors in logic are clearly visible from the graphical representation of the lorentz transformation.. or to be precise — from several assumptions represented in the graphical form, plus the arbitrary transformation itself. watch the video below first, then read my detailed explanation of every mistake in the logic there.
just a note: the presenter in the video is not stupid, he talks by the book, but that’s the problem which i have encountered in so many academic discussions — some truths are considered not questionable, because some supposedly even smarter people have worked it out. nobody is perfect, so you should always question even the most established mathematical formulas. if not, then an error in logic can carry on into entire fields of mathematics and physics, wasting lives of generations of scientists trying to solve some issues, unsolvable with the formulas with errors in them. i wish i had more persistence decades ago, to insist on the clear errors in the theory of relativity, but back then i had no idea of the mistakes in the lorentz transformation, so i wasn’t absolutely sure i had my conclusions right.
watch the video presentation and i will explain the mistakes..
so, lets discuss it..
in the beginning of the explanation the curve of different ticking clocks is arbitrarily bent — they should have been on the same level on the time scale. even worse — he sais time ticks slow to travelers, while in fact by this arbitrary graph the travelers had passed more time on the time scale, aging faster than the stationary observer — total contradiction. or, it would make “sense” only if the reference frames are arbitrarily taken, without a fixed reference point, resulting in a mathematical nonsense.
next. in the video, for the zero time of the moving object, the previously horizontal line of space axis is arbitrarily tilted to connect the 45 degree lines of light. big mistake. the connecting lines of light are very much of different length, which means they are not reaching the moving object at the same time. the horizontal plain of space axis should have been left unchanged, if the reference frame was stationary. the “sloped x-axis”, even if permitted to manipulate from the reference point of the moving object, is sloped in a wrong direction. the entire presentation is a total mess of arbitrary assumptions — it perfectly shows all the mistakes in the lorentz transformation initial inputs, and in the frames of reference.
the line of the moving object can never tilt beyond 45 degrees, which is correct, because it would mean exceeding the speed of light, but the connecting lines which are longer will show redshift while the shorter lines will show blueshift, if the space is expanding and contracting respectively. in the example though the light simply arrives at different times, not in zero time as presumed in video, by unknown to me logic.
i’m not done with the lorentz transformation yet — hold onto your chair. in the end of the video he grids up the traveler’s reference frame (with all the errors of logic in it) and squares up everything. why?! by the same logic he could as well square up the reference frame of the traveler, without any transformation.
you see.. in the formulas without graphical visualization it is easy to misunderstand the connection of lines of time as a reference only, but in fact the lines represent physically passing time — the length of the connecting lines must be taken into account. only the vertical and horizontal axes must be taken as reference lines, without arbitrarily applying the same property of reference to the passing time. and again the issue with arbitrary reference frames — in case of space-time one cannot mess around with the frame of reference, because it would mean jumping space without time. if you want to change the frame of reference during your calculations, you must account for the passing of time during that change of space, which will nullify the whole point of lorentz transformation, because the time dilation will disappear.
the very idea of applying lorentz transformation for time dilation is absurd, it’s just an abstract mathematics full of logical errors not corresponding to reality. the time dilation don’t take into account the complex movement of celestial objects in aether. read the article to get a clarification about aether — it is there and proven, just not in all the textbooks yet..
.. the displacement of galaxies related to each other is already with the speed of millions of kilometres per hour, so if an object takes a hike from earth it may in fact be slowing down, relatively speaking, instead of speeding up, or even more realistically, as earth also orbits sun, and solar system has its orbit in galaxy, then a “stationary” observer will be wobbling around. but that’s not the real point. the real point is that the relativity principle is not preserved during lorentz transformation. all those calculations and graphs are based on the presumtion — on a thought experiment with a flaw in it — that time moves slower on a moving object close to speed of light. the mistake in lorentz transformation is visible not only from its graphics, but from the very presumption that a speed of an object slows time. i have written about it before — if you perform the same calculations after flipping the stationary and moving reference frames, then the slowing of time will be result for another object, not to the same as before. both results, directly opposite, cannot be correct at the same time.
here’s an article with the detailed description of the error in the theory of relativity..
it’s time for the mathematical community to wake up and scrap lorentz transformation for time dilation, with whatever consequences it may bring to the understanding of reality.
show me the lorentz transformation with correct input of data and with a single reference frame for the duration of the entire calculation. then perform the same for each reference frame separately, without mixing them arbitrarily.. and come to the same answer with each separate calculation. it is impossible. if you can do it, i will take my words back and will post an article that i was wrong. | 0.920862 | 3.638397 |
ALIEN life in our solar system is one step closer to being discovered as NASA scientists discovered “warm” oceans on a moon of Saturn.
NASA’s Cassini spacecraft has revealed evidence of heat close to the surface of the moon Enceladus.
Warmth has been detected near cracks across the planet’s frozen surface known as “tiger stripes”.
The discovery means relatively warm oceans of liquid water are believed to exist below the surface.
It comes as NASA offered an up-close look at the Trappist-1 exoplanets – believed to be key in the hunt for life.
“What is the warm underground ocean really like and could life have evolved there?”
Scientists estimate the oceans could be a couple of miles deep into the crust of the moon – much closer than previously thought.
NASA boffins now believe the warm underground oceans could have developed life in the deep darkness.
The project scientists are now calling on the space agency to launch more missions to analyse the ocean world.
Saturn’s moons are beleived to be one of the most likely places life could have developed in our solar system – along with Venus and Mars.
More odd things near Saturn
Cassini Project scientist Linda Spilker said: “Finding temperatures near these three inactive fractures that are unexpectedly higher than those outside them adds to the intrigue of Enceladus.
“What is the warm underground ocean really like and could life have evolved there?
“These questions remain to be answered by future missions to this ocean world.”
Cassini’s new mission will end next month when it carries out its closest fly-by to Saturn.
The probe will plunge through the atmosphere of Saturn – transmitting as much data as possible before it loses signal.
It has been analysing the giant ringed planet since 2004 and has beamed back countless invaluable images and data packets. | 0.806061 | 3.016056 |
What’s In the Sky This Month? March 2020
Our Nearest Neighbors
Only Neptune appears too close to the Sun and is therefore invisible this month. Uranus is quickly following in its wake, but may still be glimpsed with binoculars in the darkening sky. Meanwhile, look to the west to see Venus. It reaches its greatest eastern elongation on the 24th and looks like a half Moon through a telescope. On the opposite end of the night, Mars, Jupiter and Saturn are all visible in the predawn sky. Faint Mars passes very close to Jupiter on the 20th and then close to Saturn on the 31st. Lastly, Mercury can be glimpsed just before the dawn and reaches greatest western elongation on the 24th, the same day as Venus. As for the Moon, it turns full on the 9th and is then new on the 24th.
M44, the Beehive Cluster:
|Distance:||610 Light Years|
|Apparent Diameter||70’ 00”|
Messier 44, or the Beehive Cluster, has been known since ancient times and can be glimpsed with the naked eye from clear, dark skies. It appears as a faint and tiny misty patch about midway between Pollux in Gemini and Regulus in Leo. If you have no luck, try scanning the area with binoculars. Regular 10x50’s will pick out the cluster quite nicely, even from suburban skies.
Despite the cluster’s large apparent diameter, you can still observe it telescopically, but you’ll need your lowest magnification eyepiece. Even at 30x, the cluster appears to crowd the field of view. The majority of stars are young, appear blue-white and are grouped in pairs or small groups, but here and there are several older, orange stars.
Pre-Dawn Planetary Encounters
Look out for the waning crescent Moon on the 18th as it forms a nice grouping with Mars, Jupiter and Saturn in the predawn sky. It then appears close to Mercury on the 21st.
Cancer’s other open cluster is smaller and fainter than the Beehive, but still visible with binoculars. Telescopically, it appears diamond-shaped with a single bright star on its edge.
A wide, easy binocular double, Rho Cancri actually comprises two coppery stars, 53 and 55 Cancri.
A pretty telescopic double requiring low magnification, with gold and blue stars reminiscent of Albireo.
Greatest Elongation: The point at which Mercury and Venus appear furthest east or west from the Sun in the sky. At greatest western elongation, the planet is best seen in the predawn sky. Conversely, at greatest eastern elongation, the planet is seen in the evening sky.
Free Printable Celestial Calendar
Star charts created with SkyGuide for iOS. | 0.880532 | 3.501337 |
Laniakea: Newly identified galactic supercluster is home to the Milky Way
Astronomers using the National Science Foundation's Green Bank Telescope (GBT)—among other telescopes—have determined that our own Milky Way galaxy is part of a newly identified ginormous supercluster of galaxies, which they have dubbed "Laniakea," which means "immense heaven" in Hawaiian.
This discovery clarifies the boundaries of our galactic neighborhood and establishes previously unrecognized linkages among various galaxy clusters in the local Universe.
"We have finally established the contours that define the supercluster of galaxies we can call home," said lead researcher R. Brent Tully, an astronomer at the University of Hawaii at Manoa. "This is not unlike finding out for the first time that your hometown is actually part of much larger country that borders other nations."
The paper explaining this work is the cover story of the September 4 issue of the journal Nature.
Superclusters are among the largest structures in the known Universe. They are made up of groups, like our own Local Group, that contain dozens of galaxies, and massive clusters that contain hundreds of galaxies, all interconnected in a web of filaments. Though these structures are interconnected, they have poorly defined boundaries.
To better refine cosmic mapmaking, the researchers are proposing a new way to evaluate these large-scale galaxy structures by examining their impact on the motions of galaxies. A galaxy between structures will be caught in a gravitational tug-of-war in which the balance of the gravitational forces from the surrounding large-scale structures determines the galaxy's motion.
By using the GBT and other radio telescopes to map the velocities of galaxies throughout our local Universe, the team was able to define the region of space where each supercluster dominates. "Green Bank Telescope observations have played a significant role in the research leading to this new understanding of the limits and relationships among a number of superclusters," said Tully.
The Milky Way resides in the outskirts of one such supercluster, whose extent has for the first time been carefully mapped using these new techniques. This so-called Laniakea Supercluster is 500 million light-years in diameter and contains the mass of one hundred million billion Suns spread across 100,000 galaxies.
This study also clarifies the role of the Great Attractor, a gravitational focal point in intergalactic space that influences the motion of our Local Group of galaxies and other galaxy clusters.
Within the boundaries of the Laniakea Supercluster, galaxy motions are directed inward, in the same way that water streams follow descending paths toward a valley. The Great Attractor region is a large flat bottom gravitational valley with a sphere of attraction that extends across the Laniakea Supercluster.
The name Laniakea was suggested by Nawa'a Napoleon, an associate professor of Hawaiian Language and chair of the Department of Languages, Linguistics, and Literature at Kapiolani Community College, a part of the University of Hawaii system. The name honors Polynesian navigators who used knowledge of the heavens to voyage across the immensity of the Pacific Ocean. | 0.846749 | 3.800901 |
John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
The best shower of the year is known for its intense, colorful "fireballs."
City dwellers have so much fun drained out of astronomical spectacles, with light pollution covering the celestial dome like gauze. But tonight's long-awaited Perseid shower might be different, as the annual bombardment is known for its super-charged meteors that paint even hazy urban skies with plasma streaks.
The impressive visual artillery of the Perseids relates to their source, Comet Swift-Tuttle, whose orbit is close enough to the earth that dust from its tail gets pulled into the atmosphere. The space detritus is thick and spiked with relatively large pieces, so that when it whizzes down at 132,000 mph it creates fireballs—intense, colorful meteors that can leave lingering trails of smoke and ionized air. During some years, watchers in darker rural areas can expect to see several of these ramped-up meteors and a flurry of smaller ones, adding up to 100 or more sightings each hour.
This year isn't the best for catching the Perseids at their prime, as an almost-full moon will be lighting the heavens. Astronomers are predicting peak rates of 30 to 40 visible meteors per hour, and in brighter city environments you can expect to see one-tenth that number. But if you were to pick one meteor shower that's worth being all crusty-eyed for the next day, it's the Perseids. Science has proven it: A NASA study recently deemed it the "best" meteor shower due to its stunning volley of fireballs. (Suck it, Geminids!)
Start looking upward around 10:30 p.m., local time. Rates should increase through the night and peak around 3 to 4 a.m. If the weather cooperates, the shower should be visible over a huge part of the planet, as shown in this NASA map:
To break those zones down into numbers, "best visibility" equates to 30 to 40 an hour in a dark environment, "low rates" is less than 10 an hour, and "very low rates" is less than five an hour. To increase your chances of spotting these flaming fliers, check out our guide to watching meteors in the big city. And if you want to hang with the big boys during the show, NASA will be holding a live-chat tonight beginning at 11 p.m. EDT. | 0.851835 | 3.468406 |
The smallest, coolest exoplanet known to host water is roughly the size of Neptune. Until now, astronomers had found water only on distant worlds that are about the size of Jupiter. The newfound water source — known as HAT-P-11b — is just a bit more than four times the diameter of Earth.
And this distant planet’s temperature? It’s a very mild 605° Celsius (plus or minus 50°), or 1,121° Fahrenheit (plus or minus 90°). That’s hot enough not only to vaporize water but also to melt lead. So this would hardly be an inviting vacation destination.
Jonathan Fraine is an astronomer at the University of Maryland in College Park. He and his colleagues discovered the distant planet’s water after a year and a half of observations with the Hubble, Spitzer and Kepler space telescopes. The researchers shared their news Sept. 25 in the journal Nature.
Gases such as water vapor leave their mark in a planet’s atmosphere. They absorb particular colors (or wavelengths) of light. When HAT-P-11b comes between Earth and its star, the planet’s atmosphere filters out some of the starlight. The astronomers noticed the disappearance of some of that star’s infrared light each time the planet passed between it and Earth. The planet’s host star is an orange dwarf. It resides about 122 light-years away in the constellation Cygnus.
The new analysis showed the planet has a relatively clear atmosphere, rich in hydrogen. All of that hydrogen is consistent with theories of planet formation. They hold that giant planets made from gas initially formed around a rocky or icy core. That core would quickly have attracted an atmosphere by pulling hydrogen out of the gaseous disk encircling an infant star.
The new data “reveal the crystal-clear signature of water-vapour,” says Eliza M.R. Kempton. She’s an astronomer at Grinnell College in Iowa. “From the strength of the absorption,” she says, it appears “the planet’s atmosphere has a composition not dissimilar to those of the giant planets of our solar system.” It consists mostly of hydrogen, with trace amounts of heavier elements, she writes in a report published in the same issue of Nature. Those heavier elements include oxygen in the form of water vapor.
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.
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.
element (in chemistry)Each of more than one hundred substances for which the smallest unit of each is a single atom. Examples include hydrogen, oxygen, carbon, lithium and uranium.
exoplanet A planet that orbits a star outside the solar system.
extraterrestrial Anything of or from regions beyond Earth.
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.
infrared light A type of electromagnetic radiation invisible to the human eye. The name incorporates a Latin term and means “below red.” Infrared light has wavelengths longer than those visible to humans. Other invisible wavelengths include X rays, radio waves and microwaves. It tends to record a hit signature of an object or environment.
Jupiter (in astronomy) The solar system’s largest planet, it has the shortest day length (10 hours). A gas giant, its low density indicates that this planet is composed of light elements, such as hydrogen and helium. This planet also releases more heat than it receives from the sun as gravity compresses its mass (and slowly shrinks the planet).
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.
planet A celestial object that orbits a star, is big enough for gravity to have squashed it into a roundish ball and it must have cleared other objects out of the way in its orbital neighborhood. To accomplish the third feat, it must be big enough to pull neighboring objects into the planet itself or to sling-shot them around the planet and off into outer space. Based on that definition, the International Astronomical Union has ruled that our solar system now consists of eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune (and not Pluto).
Neptune The furthest planet from the sun in our solar system. It is the fourth largest planet in the solar system.
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.
telescope Usually a light-collecting instrument that makes distant objects appear nearer through the use of lenses or a combination of curved mirrors and lenses. Some, however, use a network of antennas to collect radio emissions (energy from a different portion of the electromagnetic spectrum).
water vapor Water in its gaseous state, capable of being suspended in the air.
wavelength The distance between one peak and the next in a series of waves, or the distance between one trough and the next. Visible light — which, like all electromagnetic radiation, travels in waves — includes wavelengths between about 380 nanometers (violet) and about 740 nanometers (red). Radiation with wavelengths shorter than visible light includes gamma rays, X-rays and ultraviolet light. Longer-wavelength radiation includes infrared light, microwaves and radio waves. | 0.916572 | 3.88204 |
Origin of super-Earths and sub-Neptunes: Understanding the radius valley as a by-product of planet formation under the core-powered mass-loss mechanism
A video explaining how the radius valley can be understood as a by-product of planet formation under the core-powered mass-loss mechanism. Credits: Emilie Eshbaugh (UCLA undergraduate student) and Hilke Schlichting.
The video above by Emilie Eshbaugh (UCLA) gives a great explanation and introduction to this project. If you prefer a textual summary and would like further details, please read below or refer Ginzburg et al. 2018 and Gupta & Schlichting (2019, 2020).
Till 1995, we only knew about the eight planets in our Solar system. Since, we have discovered thousands of planets in our galaxy orbiting other stars, i.e. exoplanets
(4031 as of Aug 1 2019; see NASA Exoplanet Archive). These discoveries have revolutionized the field
of exoplanetary science and offer new insights into the formation and evolution of planets.
One of the key findings from recent observations has been that the abundant planets in our galactic neighborhood, to-date, are 1 to 4 Earth radii in size, i.e. larger than Earth and smaller than Neptune.
Intriguingly, further observations have revealed that there is a lack of planets of sizes 1.5 - 2.0 Earth radii, i.e. a radius 'valley', in
the size distribution of such small, short-period (<100 days) exoplanets. Moreover, a transition in planet density has been noted around
~1.6 Earth radii, with smaller planets having higher bulk densities, consistent with rocky Earth-like compositions while
larger planets having lower bulk densities, suggesting that these planets are engulfed in H/He atmospheres.
It has thus been suggested that this valley likely marks a transition regime between smaller rocky planets, i.e.
'super-Earths' to larger planets with significant atmospheres, i.e. 'sub-Neptunes'.
Radius valley in the distribution of small, close-in planets separating populations of super-Earths and sub-Neptunes.
Plot based on data from Fulton et al. 2017.
Typically, atmospheric erosion due to high-energy radiation from the host stars, i.e. photoevaporation, is suggested as an explanation to these observations.
Recently, however, Ginzburg et al. 2018 and my advisor and I (Gupta & Schlichting 2019, 2020) have demonstrated that atmospheric loss due to a planet's own cooling luminosity, i.e. core-powered mass-loss,
can also explain the observed radius valley, even without photoevaporation.
Furthermore, we have demonstrated that planetary evolution under this mechanism can explain a multitude of trends observed in the planet size distribution
with orbital period, insolation flux and stellar mass, metallicity, age (Gupta & Schlichting, 2020).
Schematic demonstrating how the core-powered mass-loss mechanism results in super-Earths and sub-Neptunes and thus the radius valley. See Gupta & Schlichting, 2019 for details.
It is likely that the observed planet distribution was not just sculpted by core-powered mass-loss and photoevaporation, but by a multitude of processes over their lifetime such as giant impacts or different planet formation pathways (icy planets, formation in gas depleted disks or after dispersal of gas disks). Nevertheless,
our work shows that the valley in the size distribution of exoplanets is an inevitable by-product of the planetary formation process, i.e. through the core-powered mass-loss mechanism.
To know more, please refer:
⚬ A. Gupta & H.E. Schlichting, 2020. MNRAS. Accepted. [ADS] [arXiv]
⚬ A. Gupta & H.E. Schlichting, 2019. MNRAS 487, 24-33. [ADS] [arXiv]
Rings around small, non-spherical planetary bodies
Artistic rendition of the triaxial shaped dwarf planet Haumea with its surrounding ring.
Image credit: Wikipedia user 'Tomruen'.
For years, we have known of the rings around the giant planets of our Solar System.
Rings are also expected to exist around extrasolar planets but have not been detected so far.
However, what was not expected was the existence of rings around much smaller, non-spherical bodies of our Solar System.
This changed in 2014 with the discovery of rings around a small body named Chariklo, followed by another discovery in 2017, of rings around the dwarf planet, Haumea.
These discoveries suggest that the ring systems are much more common in our Solar System than previously thought,
and their existence has challenged our understanding of their evolution and formation.
In collaboration with my former group
from IIT Kanpur (Prof. Ishan Sharma, Dr. Sharvari Nadkarni-Ghosh, Shri B. Bharath and others), I have been trying to understand the dynamics
of rings around non-spherical bodies through N-body simulations.
To know more, please refer:
⚬ A. Gupta, S. Nadkarni-Ghosh & I. Sharma, 2018. Icarus 299, 97-116. [ADS][arXiv] | 0.890994 | 3.867596 |
Yesterday was an important anniversary at NASA. Celebrations were in order to mark a successful year of the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft orbiting the Red Planet fulfilling its mission of understanding the upper and lower atmospheres of Mars. Scientists want to know how Martian atmospheric gases that escape into space change the climate of the planet. The ultimate question is whether or not the pattern of atmospheric evolution can trace back to an ancient history where life could once have been supported there.
MAVEN inserted itself into a Mars orbit in September, 2014 and had a dangerous encounter with Comet Siding Spring within its first month in action. Over the past twelve months, MAVEN has carried out and recorded atmospheric observations for ten of those months.
It has detected a pattern of particles at both poles that create a “Mohawk” effect as they escape the atmosphere in plumes. Mars also has a metallic particle layer high in the atmosphere which lights up when affected by solar storms. These particles are leftovers from space rubbish left behind by comets and meteorites. The gringa thinks Mars would be the perfect place for some rock-n-roll concerts.
The violent atmosphere of Mars is punctuated by solar and space radiation, magnetically and electrically charged solar flares and Coronal Mass Ejections that strip the upper atmosphere of Mars of electrically and magnetically charged ions. The data collected on MAVEN can be analyzed to hopefully answer the question if this is the reason for atmospheric loss on the Red Planet and if so, scientists will then attempt to establish a time frame for the continued erosion of the Martian atmosphere.
NASA is very proud of the teamwork that has produced such a successful Martian mission as the MAVEN project. Engineers designed and built a sturdy spaceship that remains in excellent working order despite the extreme conditions it functions within. Although mission completion date is only months away, it is expected that the mission will be extended. The rich amount of data for a hungry science community is too valuable to give up as long as MAVEN is still operational. NASA will be giving the green light for this little workhorse to stay on the job at least one more year.
Source & Photo Credit: http://www.nasa.gov | 0.866025 | 3.06244 |
Understanding how stars form from molecular gas
The star formation rate in galaxies varies greatly both across different galaxy types and over galactic time scales. MPA astronomers have been trying to gain insight into how the interstellar medium may change in different galaxies by studying molecular gas in a wide variety of galaxies, ranging from gas-poor, massive ellipticals to strongly star-forming irregulars, and in environments ranging from inner bulges to outer disks. They find that the gas depletion time depends both on the strength of the local gravitational forces and the star formation activity inside the galaxy.
Molecular clouds are clouds in galaxies consisting predominantly of molecular hydrogen. They are stellar nurseries where the gas reaches high enough densities to form new stars and planetary systems. Molecular clouds are highly complex structures. Figure 1 shows a Hubble Space Telescope image of the Eagle Nebula, a nearby molecular cloud with a highly filamentary and irregular structure.
In the neighbourhood of our Sun, molecular clouds make up only 1 % of the total volume of the interstellar medium and form stars at modest rates of a few solar masses per year. In the early Universe, however, there is mounting evidence that galaxies contain much more molecular gas and therefore they can form stars at rates up to a thousand times higher than in our Milky Way. The densities and pressures in the interstellar media of these early galaxies are also orders of magnitude higher than in the solar neighbourhood, and it is unlikely that molecular clouds in these systems are the same as the very well-studied Eagle nebula.
In recent work, the MPA group studied variations in the relation between the local density of molecular gas and newly formed stars. They used this as a diagnostic of changing conditions within the interstellar medium. According to standard theory, molecular clouds exist in a balance between gravitational forces, which work to collapse the cloud, and pressure forces (primarily from the gas), which work to keep the cloud from collapsing. When these forces fall out of balance, such as can happen in a supernova shock wave, the cloud begins to collapse and fragment into smaller and smaller pieces. The smallest of these fragments begin contracting and become proto-stars.
Gravitational forces vary significantly from one galaxy to the next, as well as in different regions of the same galaxy. At the centre of a giant elliptical galaxy, gravity is much higher than in the outskirts of a small dwarf irregular. Likewise, the incidence of supernova explosions can differ drastically between different galaxies and between different locations within the same galaxy. Variations in the ratio of the density of molecular gas to young stars (commonly referred to as the depletion time of the molecular gas) may thus be expected as a consequence of these changing conditions.
The main result (see Figure 2) from the MPA group's analysis is that the rate at which molecular gas forms new stars is set BOTH by gravity (as measured by the local surface density of stars in the galaxy) and by the local star formation activity level in the galaxy, which in turn will determine the incidence of supernova-driven shock waves in the interstellar medium. Molecular gas depletion times are shortest in regions where gravity is strong and where the star formation activity is high, particularly in galaxy bulges with gas and ongoing star formation.
Reaching this conclusion required very careful analysis of a variety of data sets at different wavelengths. In particular, star formation rates derived from the combination of infrared images that trace young stars embedded inside dusty clouds and far-ultraviolet images that trace stars that have migrated outside these clouds, are crucial for pinpointing these relations as accurately as possible. In future, new state-of-the-art interferometric radio telescopes, in particular the Atacama Large Millimeter/submillimeter Array (ALMA), will allow us to understand the detailed structure of molecular clouds in regions of high gravity in much more detail.
Guinevere Kauffmann and Mei-Ling Huang | 0.907267 | 4.166253 |
Neutron Stars on the Brink of Collapse
Neutron stars are the densest objects in the Universe; however, their exact characteristics remain unknown. Using recent observations and simulations, an international team of scientists including researchers at the Max Planck Institute for Astrophysics (MPA) has managed to narrow down the size of these stars. Thus the scientists were able to exclude a number of theoretical descriptions for the neutron star matter.
When a very massive star dies, its core collapses in a fraction of a second. In the following supernova explosion, the star’s outer layer gets expelled, leaving behind an ultra-compact neutron star. For the first time, the LIGO and Virgo Observatories have recently been able to observe the merger of two neutron stars by detecting the gravitational waves emitted and to measure the mass of the merging stars. Together, the neutron stars had a mass of 2.74 solar masses. Based on these observational data, the international team of scientists from Germany, Greece, and Japan managed to narrow down the size of neutron stars with the aid of computer simulations. The calculations suggest that the neutron star radius must be at least 10.7 km.
In neutron star collisions, two neutron stars orbit around each other, eventually merging to form a star with approximately twice the mass of the individual stars. In this cosmic event, gravitational waves – oscillations of spacetime – whose signal characteristics are related to the mass of the stars, are emitted. This event resembles what happens when a stone is thrown into water and waves form on the water’s surface. The heavier the stone, the higher the waves.
The scientists calculated different merger scenarios for the recently measured masses to determine the radius of the neutron stars. In so doing, they relied on different models and equations of state describing the exact structure of neutron stars. Then, the team of scientists checked whether the calculated merger scenarios are consistent with the observations. The conclusion: All models that lead to the immediate collapse of the merger remnant can be ruled out because a collapse leads to the formation of a black hole, which in turn means that relatively little light is emitted during the collision. However, different telescopes have observed a bright light source at the location of the stars’ collision, which provides clear evidence against the hypothesis of collapse directly after the neutron-star collision.
The results thereby rule out a number of theories for neutron star matter, namely all model descriptions that predict a neutron star radius smaller than 10.7 kilometers. However, the internal structure of neutron stars is still not entirely understood. The radii and structure of neutron stars are of particular interest not only to astrophysicists, but also to nuclear and particle physicists because the inner structure of these stars reflects the properties of high-density nuclear matter found in every atomic nucleus.
While neutron stars have a slightly larger mass than our Sun, their diameter is only a few 10 km. These stars thus contain a large mass in a very small volume, which leads to extreme conditions in their interior. Researchers have been exploring these internal conditions for several decades already and are particularly interested in better narrowing down the radius of these stars as their size depends on the unknown properties of ultra-dense matter.
The new measurements and new calculations help theoreticians to better understand the properties of high-density matter in our Universe. The recently published study represents a significant scientific progress as it has ruled out some theoretical models. But there is still a large variety of other models with neutron star radii greater than 10.7 km.
However, the scientists have been able to demonstrate that further observations of neutron star mergers will continue to improve these measurements. The LIGO and Virgo Observatories have just begun taking measurements, and the sensitivity of the instruments will continue to increase over the next few years and provide even better observational data. | 0.888182 | 4.062098 |
Two nearly identical spacecraft, destined to capture the first-ever 3-D views of the sun, are scheduled for launch on Aug. 31 aboard a Delta II rocket from Cape Canaveral Air Force Station, Fla., at 3:12 p.m. or 4:20 p.m. EDT. The window extends through Sept. 4 with two launch opportunities daily.
Built and operated for NASA by The Johns Hopkins University Applied Physics Laboratory (APL), in Laurel, Md., the two-year STEREO (Solar TErrestrial RElations Observatory) mission will explore the origin, evolution and interplanetary consequences of coronal mass ejections. These powerful solar eruptions are a major source of the magnetic disruptions on Earth and a key component of space weather, which can greatly affect satellite operations, communications, power systems, and the lives of astronauts in space.
"Building and testing two spacecraft simultaneously has been a technical and scheduling challenge, but an effort at which we've been successful," says Ed Reynolds, APL STEREO project manager. "The entire STEREO team is so proud and excited to launch the twin observatories and be part of the first mission to capture coronal mass ejections in 3-D."
To capture the sun in 3-D, the twin observatories will fly as mirror images of each other. One of the observatories will be placed ahead of Earth in its orbit around the sun and the other behind. Just as the slight offset between your eyes provides you with depth perception, this placement will allow the STEREO observatories to obtain 3-D images and particle measurements of the sun.
Placing STEREO into Orbit
STEREO mission designers determined that the most efficient and cost-effective way to get the observatories into space was to launch them aboard a single rocket and use lunar swingbys to place them into their respective orbits. This is the first time lunar swingbys have been used to manipulate orbits of more than one spacecraft. Mission designers will use the moon's gravity to redirect the observatories to their appropriate orbits — something the launch vehicle alone can't do.
After launch the observatories will initially fly in an elliptical orbit that extends from Earth just beyond the moon. Approximately two months later, mission operations personnel at APL will synchronize spacecraft orbits and direct one observatory to its position trailing Earth. Approximately three months after launch, the second observatory will be redirected to its position ahead of Earth.
Each STEREO observatory will carry two instruments and two instrument suites, providing more than a dozen instruments per observatory. APL designed and built the spacecraft platform housing the instruments. When combined with data from observatories on the ground or in space, STEREO's data will allow scientists to track the buildup and liftoff of magnetic energy from the sun and the trajectory of Earth-bound coronal mass ejections in 3-D.
STEREO's instruments were built by numerous organizations worldwide with a principal investigator, or PI, leading each instrument team. The instruments and PIs are as follows: Sun-Earth Connection Coronal and Heliospheric Investigation (SECCHI) — Russell Howard, Naval Research Laboratory; In situ Measurements of PArticles and CME Transients (IMPACT) — Janet Luhmann, University of California, Berkeley; PLAsma and SupraThermal Ion Composition (PLASTIC) — Antoinette Galvin, University of New Hampshire; and STEREO/WAVES (S/WAVES) — Jean-Louis Bougeret, Paris Observatory, Meudon.
STEREO is the third mission in NASA's Solar Terrestrial Probes Program. STEREO is sponsored by NASA's Science Mission Directorate, Washington, D.C. NASA Goddard's Solar Terrestrial Probes Program Office, in Greenbelt, Md., manages the mission, instruments and science center. APL designed and built the STEREO spacecraft and will operate the twin observatories for NASA during the mission.
For more information about STEREO or to download additional images, visit http://stereo.jhuapl.edu. | 0.854059 | 3.254387 |
We are here.
Circling one star among hundreds of billions, in one galaxy among a hundred billion more, in a Universe that is vast and expanding ever faster – perhaps toward infinity. In the granular details of daily life, it’s easy to forget that we live in a place of astonishing grandeur and mystery.
The Breakthrough Initiatives are a program of scientific and technological exploration, probing the big questions of life in the Universe: Are we alone? Are there habitable worlds in our galactic neighborhood? Can we make the great leap to the stars? And can we think and act together – as one world in the cosmos?
Where is everybody?
So wondered the great physicist Enrico Fermi. The Universe is ancient and immense. Life, he reasoned, has had plenty of time to get started – and get smart. But we see no evidence of anything alive or intelligent in space. In the last five years, we have discovered that planets in the habitable zone of stars are common. Based on the numbers discovered so far, there are estimated to be billions more in our galaxy alone. Yet we are still in the dark about life. Are we really alone? Or are there others out there?
It’s one of the biggest questions. And only science can answer it.
Breakthrough Listen is a $100 million program of astronomical observations in search of evidence of intelligent life beyond Earth. It is by far the most comprehensive, intensive and sensitive search ever undertaken for artificial radio and optical signals. A complete survey of the 1,000,000 nearest stars, the plane and center of our galaxy, and the 100 nearest galaxies. All data will be open to the public.
Breakthrough Message is a $1 million competition to design a message representing Earth, life and humanity that could potentially be understood by another civilization. The aim is to encourage humanity to think together as one world, and to spark public debate about the ethics of sending messages beyond Earth.
Where can life flourish?
In August 2016, a potentially habitable Earth-like planet was discovered orbiting Proxima Centauri – the Sun’s nearest neighbor. Based on the most recent astronomical data, it is likely that there are other such planets in our cosmic neighborhood. With technology now or soon available, it will be possible not only to find them, but to analyze whether they have atmospheres – and whether those atmospheres contain oxygen and other potential signatures of primitive life.
Breakthrough Watch is multi-million dollar astronomical progam to develop Earth- and space-based technologies that can find Earth-like planets in our cosmic neighborhood – and try to establish whether they host life.
Can we reach the stars?
Life in the Universe does not only mean extraterrestrials. It also means us. No other beings have yet visited us – but neither have we stepped out to the galactic stage. Are we destined to belong to Earth for as long as we survive? Or can we reach the stars?
If we can, the natural first step is our nearest star system, Alpha Centauri – four light years away.
Breakthrough Starshot is a $100 million research and engineering program aiming to demonstrate proof of concept for a new technology, enabling ultra-light unmanned space flight at 20% of the speed of light; and to lay the foundations for a flyby mission to Alpha Centauri within a generation.
The Breakthrough Initiatives were founded in 2015 by Yuri and Julia Milner to explore the Universe, seek scientific evidence of life beyond Earth, and encourage public debate from a planetary perspective. | 0.810156 | 3.573436 |
On August 23, 2017, astronomers have unveiled a photo which is the most detailed ever image of a star other than our Sun. The image of the red “supergiant” Antares has been constructed using the European Southern Observatory’s (ESO) Very Large Telescope Interferometer (VLTI) on Cerro Paranal (a mountain in the Atacama Desert of northern Chile).
The Very Large Telescope Interferometer (VLTI) consists in the coherent combination of the four VLT Unit Telescopes (8.2 meters in diameter) or the four moveable 1.8m Auxiliary Telescopes. It is used to resolve small objects. The VLTI provides milli-arcsec angular resolution at low and intermediate (R=12000) spectral resolution at near-infrared wavelengths.
Due to its characteristics, the VLTI has become a very attractive means for scientific research on various objects like young pre-main sequence stars and their protoplanetary disks, post-main-sequence mass-losing stars, binary objects, and their orbits, solar system asteroids, and extragalactic objects such as active galactic nuclei.
Located around 620 light-years from the Sun, Antares, also known as Alpha Scorpii is the fifteenth-brightest star in the night sky; the brightest star in the constellation of Scorpius, and is often referred to as “the heart of the scorpion”.
It is a red “supergiant”. Its exact size remains uncertain, but, probably with a radius that is approximately 1 billion 228 million kilometers (883 times that of the Sun), it is one of largest stars in the Universe, and if placed in the center of the Solar System, its outer surface would lie between the orbits of Mars and Jupiter.
It is dwarfed by even larger red supergiants, such as VY Canis Majoris and UY Scuti, though.
Antares’ mass is calculated to be around 12 times that of the Sun.
Antares is also nearing the end of its life. Once there is no more fuel left to burn, the star will collapse and explode into a supernova, possibly in the next ten thousand years. After the explosion, the Antares supernova could be as bright as the full moon and be visible in the daytime for a few months.
Antares’ location in the Earth’s sky
Antares on Wikipedia
Antares: astronomers capture best ever image of a star’s surface and atmosphere on The Guardian
“See the Best-Ever Imagery of a Star Beyond the Sun” on Space.com
Very Large Telescope on Wikipedia
The Very Large Telescope Interferometer on the European Southern Observatory website | 0.887378 | 3.776338 |
At the core of our explorations is the quest to know if life exists beyond Earth. The Planetary Society is a leader in the search for life on other worlds, whether intelligent or microbial. Our active projects: SETI Optical Telescope - Looking for laser signals beamed across the vastness of space. SETI Radio Searches - Huge radio dishes sift through nature's random noise for beacons from other civilizations.
In 2006, The Planetary Society unveiled the first All-Sky Optical SETI (OSETI) telescope. Funded by The Planetary Society and operated by a Harvard University team, it's completely dedicated to capturing that one pulse of light that might be a communication.
One faint signal from light-years away could prove we're not alone in this universe. The Planetary Society is committed to finding that signal -- tirelessly surveying the skies with our Southern SETI project and our Optical SETI Telescope. You can be a part of these projects and help us keep the search going.
SETI@home scientists will have to wait for several weeks for the full analysis of the data collected during the reobservations. But even while the observations are going on at Arecibo, they will already have a good idea if they have found something significant.
For three successive days SETI@home will have use of the giant Arecibo radio telescope to revisit the most promising candidate signals detected since the project was launched in 1999. SETI@home Chief Scientist Dan Werthimer and his team put together a list of the "best" 200 locations in the sky where promising candidates have previously been detected.
For the first time during the reobservations, Werthimer and his crew will have use of another recorder. This is Arecibo's "radar" recorder, built for those occasions when the giant dish is used as a radar, bouncing electromagnetic signals off planets, moons, and asteroids.
In the next few days, SETI@home Chief Scientist Dan Werthimer, along with team members Eric Korpela and Paul Demorest, will head down to Arecibo in Puerto Rico. There, at the site of the largest radio telescope in the world, they will begin a new chapter in the short history of the project: the reobservation of SETI@home's most promising candidate signals.
If we were to listen to radio transmissions from space, we should be able to hear the dying gasps of black holes. As it turns out, we are listening, or at least the SETI@home receiver is. Perched above the giant Arecibo dish, it is systematically surveying a large portion of the sky, listening to the signals coming from space. | 0.878913 | 3.484266 |
Astronomers were lost for words when they spotted vast glowing blobs of matter many times the size of a galaxy in their snapshots of the early universe.
And so it was that these rare, ethereal objects, first seen in the 1990s, came to be known as Lyman-alpha blobs, their place instantly secured among the most mysterious phenomena in the heavens.
Early studies of the blobs revealed them to be gigantic clouds of hydrogen gas that contained clusters of fledgling galaxies, but scientists could not explain why the blobs glowed so brightly.
In new research, astronomers turnedthe European Southern Observatory‘s Very Large Telescope in Paranal, Chile, to face the enormous Lab-1, in the hope of finding an answer.
The blob is one of the largest known, around 300,000 light years across, or several times wider than the Milky Way, and so distant that its light has taken 11.5bn years to reach the Earth.
All Labs glow with light that is emitted when electrons lose energy inside hydrogen atoms, a process that produces a luminous signature known as the Lyman alpha line.
Although the light is released as ultraviolet radiation, the expansion of the universe stretches the waves so much that by the time it has crossed the cosmos to reach Earth, the light appears green.
A team led by Matthew Hayes, a cosmologist at the University of Toulouse, found that light from the giant blob was polarised, meaning the electric and magnetic fields that make up the lightwaves were aligned in a particular direction.
“We wanted to know what was powering these systems and this helps us to understand that. If the light is polarised, it has to come from within the galaxies themselves,” Hayes said. The study appears in the journal, Nature.
One earlier school of thought held that the glow came from gas in the cloud as it was pulled by extreme gravitational forces into the heart of the blob. But this would produce unpolarised light, Hayes told the Guardian.
The young galaxies inside Labs are birthplaces for stars and some galaxies have supermassive black holes at their centres. Both of these are likely to contribute to heating up the gas cloud and causing it to glow, Hayes said. The light becomes polarised as it is scattered through the gas cloud over distances of up to 150,000 light years.
“This helps us to build a more accurate picture of how the universe formed,” he said. | 0.852817 | 3.860875 |
Comets are icy planetesimals formed in the outer solar system. The nucleus, typically a few kilometers in diameter, is essentially composed of water ice mixed with carbon oxides, methane, ammonia, and of dust particles. When the comet approaches the Sun, the ices sublimate, forming a gaseous and dusty coma. Solar radiation and wind blow this material to form the spectacular cometary tails. Because comets are thought to be preserved remnants of the early stages of the solar system, they are considered as belonging to its most pristine bodies. Understanding their origin, evolution and composition is therefore a clue to the history of our planetary system. Moreover comets contain complex organic molecules, and may have played a key role in the transfer of water and organics from the interstellar medium to the early Earth, then contributing to the origin of life.
Our research group uses the TRAPPIST telescope for a photometric and astrometric survey of Southern comets. For relatively bright comets we measure once a week the gaseous production rates and the spatial distribution of several species among which OH, NH,CN, C2, as well as ions like CO+. The dust production rates are determined, also for fainter comets. Such regular measurements are rare because of the lack of observing time on larger telescopes. Yet they are very valuable as they show how the gas production rate of each species evolves with respect to the distance to the Sun. Those observations allow to determine the composition of the comets and the chemical class to which they belong (rich or poor in carbon for instance), possibly revealing the origin of those classes. Indeed with dozens of comets observed each year, this program provides a good statistical sample after a few years. Thanks to the way the telescope is operated, follow up of split comets and of special outburst events is possible right after an alert is given and can bring important information on the nature of comets. Light curves from those data are useful to assess the gas and dust activity of a given comet in order, for instance, to prepare more detailed observations with larger telescopes.
To make such observations possible, the telescope is equipped with large (5x5cm) high quality cometary narrow band filters. Those filters are on loan from David Schleicher of the Lowell Observatory (Flagstaff, USA) and were built by the NASA for the observing campaign of the famous comet Hale-Bopp (Farnham et al. 2000). Those filters isolate small spectral regions where given cometary species are mostly emitting (emission bands), as well as nearby continuum regions (dust reflected solar spectrum). In addition to providing the productions rates of the different species through a proper photometric calibration, image analysis can reveal coma features (jets, fans, tails), that can lead to the detection of active regions and measure the rotation period of the nucleus.
Contact(s) : [email protected] | 0.909233 | 4.133444 |
XMM-Newton, the ESA’s premiere space-based X-ray observatory, will celebrate 10 years of spectacular X-ray imaging of our Universe today. On the 10th of December 1999 at 14:32 GMT, XMM-Newton was launched by the European Space Agency, and tasked with the mission of observing some of the most interesting objects in the Universe with its X-ray eyes. Many objects such as black holes and neutron stars have been studied using the telescope, because these energetic objects emit light in the X-ray spectrum.
To date, over 2000 published articles have utilized information from the XMM-Newton telescope. X-rays, a very energetic form of photons, are created in extreme celestial events, such as the disks that surround black holes and the intense magnetic fields surrounding stars. By studying the X-rays emitted by a variety of celestial objects, astronomers have been able to get detailed information about the workings of the Universe.
XMM-Newton has also been crucial to the study of galaxy clusters and supermassive black holes, and has helped to create the largest catalog of cosmic X-ray sources, with over a quarter of a million entries. It has even been enlisted in the hunt for dark matter, as one theory of the substance suggests that a decayed dark matter particle would potentially emit X-rays. Exotic objects far away aren’t the only target for the observatory, though; it’s helped astronomers detect the outer edges of the atmosphere of Mars and icy comets at the outer limits of our Solar System.
Here are just a few of the stories on Universe Today that feature observations by XMM-Newton:
- Pulsar Blasts Through a Ring of Gas
- Doughnut Around a Black Hole
- XMM-Newton Zeroes in on Zombie Star
- XMM-Newton Discovers Strange-Shaped Supernova Remnant
To celebrate the first decade of XMM-Newton’s observations, the ESA will hold a celebration in Madrid, Spain on December 10th. Here’s a link to XMM-Newton’s image gallery, and here’s one to a list of publications utilizing the telescope’s images. | 0.898757 | 3.761667 |
Ever since the theory of the Big Bang came to the fore, astronomers have known that the universe had a beginning, and thus, a birth date. But figuring out just how many candles to put on the universe's birthday cake has proven tricky.
In recent years, thanks to the worldwide efforts of astronomers using the Hubble Space Telescope and other instruments, the age of the universe has been narrowed down to 13–14 billion years. This week, an independent study led by Harvey Richer (University of British Columbia), confirmed that result and put a strong lower bound of 12–13 billion years on the age.
Richer's team looked to white dwarfs to reach their age estimate. They peered deep into the globular cluster M4 in Scorpius with the Hubble Space Telescope to identify the dimmest, coolest, and therefore oldest white dwarfs. These 30th-magnitude objects were among the first stars to form in the cosmos.
When a Sun-type star reaches the end of its lifetime and sheds most of its outer gasses as a planetary nebula, the remaining core — a white dwarf — slowly cools for billions of years to come. The rate of white dwarf cooling is well understood. Cooler than a certain temperature, no additional white dwarfs were found. Richer used the temperature cutoff point of the dying stellar embers to determine their ages.
"What we have done is look at [white dwarfs] in the most ancient star clusters that we could find, and we [identified] the coolest and dimmest of these to derive an age," says Richer.
From measurements of 600 dwarfs, Richer finds that the oldest are between 12.7±0.7 billion years old. Current theories of galaxy and star formation suggest that about one billion years passed between the Big Bang and the birth of the stars now seen as these white dwarfs — yielding a total cosmic age of nearly 14 billion years.
The most definitive age determination study to date is often thought to be the Hubble Space Telescope Key Project to measure the Hubble Constant. Wendy Freedman (Carnegie Institution of Washington) led the project, which measured the rate of the universe's expansion to be 72 kilometers per second per megaparsec. From that finding (and taking into account the accelerating rate of the expansion due to the recently discovered dark energy), Freedman's team derived an age of the universe of around 14 billion years.
"The fact that [the ages] are in the same ballpark is an interesting result," says Freedman.
Richer's work will be published in an upcoming issue of Astrophysical Journal Letters. | 0.875697 | 4.091501 |
The Antarctic observatory known as IceCube has ruled out the existence of a fourth type of neutrino particle — and one-time dark matter contender — known as the light sterile neutrino.
Neutrinos are among the smallest subatomic particles, less than a millionth the mass of an electron. They’re among the most antisocial too, interacting only rarely with other particles. Every second, 100 trillion neutrinos pass through your body without bothering you a bit.
In fact, with characteristics like these, neutrinos actually qualify as elusive dark matter, the invisible stuff that suffuses the universe and governs its fate. But they don’t account for much of it. We know of three neutrino types (muon, tau, and electron), and they’re all too light and speedy to account for more than a pittance of the universe’s missing mass.
For years now, though, physicists have had reasons to suspect that a fourth, heavier type of neutrino might exist, perhaps even in sufficient quantity to explain all the universe’s missing mass. This fourth neutrino, often called a sterile neutrino, would be markedly different than its brethren: it would eschew the weak nuclear force, the fundamental force of nature by which the other three types exert occasional influence on ordinary matter. Instead, it would opt for solely gravitational interactions.
Some experiments had caught hints of a “light” sterile neutrino, about three times the mass of the other neutrino types combined. Neutrino detectors, nuclear power reactors, and radioactive sources had all produced anomalies that theorists said a light sterile neutrino could explain. But bona fide detections remained out of reach.
“Like Elvis, people see hints of the sterile neutrino everywhere,” IceCube principal investigator Francis Halzen (University of Wisconsin) said in a press release. “There was this collection of hints, and theorists were convinced it exists.”
Astrophysics diverged from physics, though. The Planck satellite’s observations of the cosmic microwave background (the Big Bang’s afterglow) were consistent with only three types of neutrinos. If a fourth neutrino existed, scientists would have to rethink their analysis of the earliest light in the universe.
Now, a recent study in Physical Review Letters has left the light sterile neutrino out in the cold.
Light Sterile Neutrino Bites the Dust
The IceCube Neutrino Observatory consists of 5,160 light sensors deep within a cubic kilometer of ice in Antarctica. Out of the billions and billions of neutrinos that pass through Earth every second, rare interactions with ordinary matter generate occasional flashes of light. Over a year’s worth of looking, IceCube scientists caught hundreds of thousands of flashes — that is, hundreds of thousands of neutrinos that had passed through space and the bulk of Earth, only to be caught in Antarctic ice.
Neutrinos are changeable creatures, constantly morphing from one type to another. A muon neutrino, for example, can change without warning into a tau neutrino or an electron neutrino. All of these might rarely interact with ordinary matter to generate light that IceCube can see. But a muon neutrino might morph instead into a sterile neutrino, which won’t interact with the ice atoms. The presence of sterile neutrinos would therefore show up not as a signal but as an absence of neutrinos at a particular energy. Rather than flashing light at IceCube, sterile neutrinos would pass quietly through Earth and back into space.
IceCube saw no sign of this absence — neutrinos produced the expected signals over an energy range that spanned 320 billion electron volts to 20 trillion electron volts. As a result, Halzen and colleagues have effectively ruled out the existence of a light sterile neutrino, which in turn removes one of the (many) contenders for dark matter.
Watch the IceCube team explain the results:
Not the End of the Story
Lest you think sterile neutrinos are out of the running — they’re not. The recent IceCube study was looking specifically for light sterile neutrinos, but heavy sterile neutrinos (those with masses of more than 10 eV) are still a possibility. Planck, too, leaves open the possibility of heavy sterile neutrinos. A strange X-ray signal seen in observations of galaxy clusters might yet be explained by a heavy sterile neutrino with a mass of 7,000 electron volts.
The IceCube results do, however, put to death hopes raised by many physics experiments that had seen hints of a light sterile neutrino with a mass around 1 eV. Those hints can now be ruled out as statistical anomalies.
That said, physicists are still working on closing loopholes. “While the IceCube search puts strong limits on light sterile neutrinos, combined analysis of many experimental data are indicating small remaining allowed regions,” says David Schmitz (University of Chicago). Schmitz, who wrote an accompanying reaction piece online in Physics, is planning follow-up analysis to detect not just neutrino disappearances but appearances as well.
Read S&T Contributing Editor Govert Schilling's award-winning article on the IceCube observatory in the January 2014 issue of Sky & Telescope. | 0.863156 | 4.187027 |
Comet ISON is upstaged! Four comets are currently on display for binoculars or small telescopes in the east before the beginning of dawn (for Northern Hemisphere observers). One is Comet ISON, still underperforming at only about 8th magnitude. It starts this week about midway between Mars and Spica and speeds toward Spica daily, to pass it on November 17th and 18th.
But ISON is being outdone! Comet 2013 R1 (Lovejoy) "is a humdinger — almost as bright now as Comet ISON was forecast to be," writes S&T's Tony Flanders. "And it's very high in the sky... big, bright, and beautiful in 10×30 binoculars."
The other two comets, Encke and C/2012 X1 (LINEAR), are fainter. See Tony's article The Other Great Morning Comet, with finder charts for Lovejoy and ISON. Further details and charts for all four are at comets.skyhound.com.
And don't delay. Encke is getting very low, and moonlight returns to the just-before-dawn sky after about November 15th.
Friday, November 8
Saturday, November 9
Sunday, November 10
Monday, November 11
Tuesday, November 12
Wednesday, November 13
Thursday, November 14
Friday, November 15
Saturday, November 16
Want to become a better astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.
This is an outdoor nature hobby. For an easy-to-use constellation guide covering the whole evening sky, use the big monthly map in the center of each issue of Sky & Telescope, the essential guide to astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).
Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts). The standards are the little Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger and deeper Sky Atlas 2000.0 (stars to magnitude 8.5); and once you know your way around, the even larger Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts with a telescope.
You'll also want a good deep-sky guidebook, such as Sue French's Deep-Sky Wonders collection (which includes its own charts), Sky Atlas 2000.0 Companion by Strong and Sinnott, the bigger Night Sky Observer's Guide by Kepple and Sanner, or the beloved if dated Burnham's Celestial Handbook.
Can a computerized telescope replace charts? Not for beginners, I don't think, and not on mounts and tripods that are less than top-quality mechanically (able to point with better than 0.2° repeatability, which means heavy and expensive). As Terence Dickinson and Alan Dyer say in their invaluable Backyard Astronomer's Guide, "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand."
This Week's Planet Roundup
Mercury, rapidly brightening from magnitude +1.0 to –0.5 this week, has leaped up from the sunrise glare to shine low in the east-southeast in early dawn. By November 13th it's having its best morning apparition of 2013. Don't confuse it with Spica, 10° or 12° to Mercury's upper right all week as shown here, or brighter Arcturus, 30° to Mercury's upper left.
Venus (magnitude –4.7) is the bright "Evening Star" in the southwest during dusk, shining nearly as high and bright as it will become this apparition. It now sets a good hour after dark. In a telescope, Venus has waned to its thick-crescent phase and has enlarged to be about 28 arcseconds tall.
Mars (magnitude 1.4, in Leo) rises around 1 or 2 a.m. It's moving eastward against the background stars, pulling farther away to the lower left from Regulus. By dawn, Mars and Regulus are high in the southeast.
Mars is still a telescopic disappointment, only 5 arcseconds in diameter. It reaches its next opposition in April 2014.
Jupiter (magnitude –2.4, in Gemini) rises in the east-northeast around 9 p.m. with Pollux and Castor to its left. It blazes highest in the south well before dawn. In a telescope Jupiter has grown to 42 arcseconds wide as it heads toward its January 5th opposition.
Saturn is hidden behind the glare of the Sun.
Uranus (magnitude 5.7, in Pisces) and Neptune (magnitude 7.9, in Aquarius) are high in the southeast and south, respectively, in early evening. Finder charts for Uranus and Neptune. See also the October Sky & Telescope, page 50.
All descriptions that relate to your horizon — including the words up, down, right, and left — are written for the world's mid-northern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America.
Eastern Standard Time (EST) is Universal Time (known as UT, UTC, or GMT) minus 5 hours.
Like This Week's Sky at a Glance? Watch our SkyWeek TV short, also playing on PBS.
To be sure to get the current Sky at a Glance, bookmark this URL:
If pictures fail to load, refresh the page. If they still fail to load, change the 1 at the end of the URL to any other character and try again. | 0.887018 | 3.355811 |
In 2017, observatories around the world observed a high-energy collision between a pair of dense objects, each slightly more massive than the Sun but only the size of a city. A similar collision closer to home could have been responsible for producing some of the heaviest elements in our own solar system—and scientists think they know when it happened.
Scientists now think that these binary neutron star mergers are an important source of elements heavier than iron in the universe. These elements are rare, but they’re also some of the most important elements to us humans. Using measurements of what’s left of these elements in ancient meteorites, a pair of researchers worked backward to locate the neutron star merger that produced some of them.
“We discovered this binary star merger two years ago, and it was close to the Milky Way—much closer than we anticipated,” Imre Bartos, the study’s first author and assistant professor at the University of Florida, told Gizmodo. “We asked whether something even closer... could have a significant impact in what the solar system looks like today.”
Elements heavier than iron form in part thanks to the “r-process,” where some high-energy event causes seed atomic nuclei to quickly suck up a lot of neutrons. Once the event slows down, some of these neutrons radioactively decay into protons. Stellar explosions called supernovae and neutron star mergers have both been implicated as potential sources of the r-process elements.
First, the researchers set out to see whether neutron star mergers or supernovae produced the elements they were interested in, mainly curium and plutonium. Supernovae, in which stars explode, happen relatively frequently, while neutron stars only merge perhaps a few times every million years in our galaxy, according to the paper published in Nature. That means that, if you look back in time, abundances of these elements should spike if they were produced by neutron stars, or stay relatively constant if they were produced by supernovae.
Plutonium and curium are radioactive, and decay into more stable elements. When the earliest meteorites formed, they captured some of these elements, which then decayed into more stable elements. The relative abundances of the decay products in these meteorites allow scientists to backtrack and determine the approximate age when the initial elements formed.
When Bartos and Columbia University professor Szalbocs Marka performed calculations on previously collected data from these meteorites, they found that the abundances of these elements spiked approximately 80 million years before the solar system formed, when it was just a cloud of gas and dust. The inferred that a single event, probably a neutron star merger a thousand light-years away, produced the lion’s share of the curium and perhaps a third of the plutonium in the solar system. This amounts to only a fraction of a percent of the total amount of r-process elements in the solar system, but “there have been many neutron star mergers in the history of the Milky Way,” Bartos said.
It’s cool research. “[These elements] are a tiny fraction of 1 per cent of the universe, but they’re highly useful to us in many ways,” David Helfand, an astronomer and professor at Columbia University, told Gizmodo. “Just knowing where they came from helps us feel a little bit more at home in the universe.”
It’s important to note that these results are based on modelling of indirect measurements, and our knowledge of neutron star collisions and the r-process comes from just one experimental observation. Though unlikely, perhaps another kind of even more chaotic high-energy event produced these elements. Bartos told Gizmodo that the next step is to measure more elements with unknown abundances, create better simulations, and of course, to observe more neutron star collisions. Fortunately, the LIGO and Virgo gravitational wave observatories have both been upgraded and have already started detecting signals from colliding black holes and perhaps even some neutron stars.
Bartos was excited about how these results combine so many different fields, from geoscience to astrophysics to chemistry. “By connecting this field in this particular work, we hope we’re starting a bigger effort to use this information in unison.”
Featured image: Illustration: ESA | 0.837352 | 4.053412 |
Night Sky Adventures™ interpretive astronomy tours begin with a short orientation of the telescope, instructions regarding the telescope and description of how and why it works and how to use it.
Then we “travel” to our own solar system, viewing the planets visible that night and moon if it is up. Depending on the time of year, the rings of Saturn, Jupiter’s great red spot and moons are all plainly visible. The polar ice caps, surface color variations and dust storms of Mars, the crescent phases, and beautiful cloud tops of Venus and the green disk of Uranus all show their beauty through the eyepiece. The space walk feel of the surface of the Moon at over 300 power is simply breathtaking.
Next comes shining brilliance of stars and star systems. Viewing stars against a jet black sky is like diamonds on velvet, and star clusters with points of light too numerous to count fill the eyepiece like fireworks. Nebulae with glowing blue, green and purple tendrils seem like delicate fiery giants in space (they are). Supernova remnants, the death shells of exploded stars, expand silently across the galaxy. All of these sights give you a feel for the true scale and beauty of the universe.
Then, we leave our own galaxy for the reaches of deepest interstellar space. Hundreds of millions of light years away (yes you can see that far), galaxies become visible as spinning wheels across the universe or great globes of light containing billions and billions of stars crossed by dark lanes of dust, gas and debris from dying stars.
From time to time we will leave the telescope to see the nearby stars with short laser pointer presentations of the constellations and their legends.
Questions are encouraged and guests are welcome to bring their own binoculars and to share their experiences.
All of this with professional presentation and interpretation in easy to understand terms.
Full Moon is not the best time to view. Click Here and see why. | 0.908461 | 3.009403 |
Throughout this series we have explored the risks that come with living in space, the psychological challenges that our future colonists will be forced to face, and the physical threats that bar our passage to the stars. But we have not discussed arguably one of the most important aspects of orbital life: our future homes. What will these massive constructions look like? How will they function? This week in Living In Space, we take a look at a variety of proposed Space Colonies and answer the question “How do we get to there from here?”
Gerard O’Neill is often looked to as one of the greatest pioneers in the world of orbital settlement. His books and lectures made what many considered a sci-fi pipedream seem realistic and attainable. His book – The High Frontier – is seen by many as one of the best, most readable books on the subject, even decades after its publication. His life’s work led to the formation of the L5 Society, as well as inspired works by the National Space Society (NSS) and several other major space groups. He was also one of the first people to popularize designs for space colonies backed by scientific research.
O’Neill envisioned three designs for his space colonies, which he referred to as the “Island Three” throughout his writings: the Stanford Torus, the Bernal Sphere, and the O’Neill Cylinder. Each of these structures is fairly different and has a variety of mechanical and technological hurdles standing in the way of their construction, outside of the obvious prohibitive costs associated with constructing a city in the stars.
The Stanford Torus was considered by O’Neill to be the most basic of his three main designs. Based on the idea of a ring-shaped rotating space station originally put forward by Werner Von Braun, the Torus was designed in 1975 by O’Neill to be a small, feasible settlement in space as part of a summer research project that would go on to become the basis of a paper on space colonization. The design consists of a doughnut shaped habitat about a mile (1.6 km) across, with a large mirror suspended above. The mirror reflects sunlight through a series of secondary mirrors arranged in such a way as to block harmful rays from the sun, while still providing power and light to the station.
The paper stated that the station could hold around 10,000 people eventually, housed in the center of the ring. The outer layers of the ring were to be used for shielding, and the inner for agriculture. The ring would have to spin once a minute to produce Earth gravity, would generate power via solar arrays and have a small non-spinning portion designed for zero gravity work. Inside the station, O’Neill envisioned colonists living a leisurely life, with ample space and every amenity on Earth, but with all the benefits and splendor afforded to them by the cosmos. These relatively scalable Torus structures were designed to be suitable for anything from a small Earth-orbit rest stop to self-contained cities at Sun-Earth Lagrangian point L5.
Some effort was even put forward to describe how this structure would be built mechanically. Construction and fabrication would be very much like Earth construction, utilizing standard methods of building. The fabrication of raw materials would require special forges designed for space and imported ores from the lunar surface (an idea later found to be prohibitively expensive as a first step and replaced with the concept of asteroid mining).
Bernal Sphere (Island Two)
Originally designed by British scientist John Desmond Bernal, the first Bernal sphere was a vast 10 miles wide, filled with air, and housing over 20,000 people. O’Neill redesigned the station for a project at Stanford, scaling down to only 500m rotating at 1.9RPM to produce near-Earth gravity. The Bernal Sphere was put forward as a concept for ”next generation” space stations designed for comfort, over more utilitarian stations such as the International Space Station (ISS) or the Torus.
Similar in many ways to the Torus, Island Two would rotate to produce gravity, collect sunlight via a series of mirrors and contain a series of farm sections producing food for the population. The spherical design of Island Two meant that the need for a special zero-gravity compartment was not needed; the center of the station would be a zero-gee zone and could be utilized for specialty fabrication or recreation. The habitat was designed with several rings at both ends of the sphere to be used for farming, and a long docking tube running through the entire structure capped with microwave communication arrays and solar collectors.
Much of the research and study that went into the Torus design was also applicable to the Bernal Sphere. Its construction would require a similar building approach, its shielding methods and internal construction would also be similar. The L5 Society hoped that such a structure would take only 2 years to build, based on their (clearly) massively optimistic timeline of space industry development.
Island Two was later presented by the L5 Society as the model of their hopes and dreams – the idea of a massive verdant valley in Space, teaming with life and housing thousands would, they hoped, capture the imagination of the world.
O’Neill Cylinders (Island Three)
Island Three was proposed as a sort of end-game design for space habitation. Published by O’Neill in 1974 in Physics Today, the cylinders were essentially the ideas of the previous designs writ large. 5 miles (8 km) in diameter and 20 miles (32 km) long, two cylinders would hold upwards of 40,000 people each comfortably, with great spaces devoted to parks and greenery. In contrast to the earlier designs, these would be veritable cities built in space; citizens would be workers from all walks of space industry and their families. The cylinders would not merely be a place for workers to stay during their contracts, but a true home, full of recreational facilities, businesses, and industry.
The size of these habitats provides several quirks – for one, they would require a relatively slow rotation to maintain near-Earth gravity (only about 40 per hour). This would be slow enough to avoid causing motion sickness in almost everyone living aboard – although citizens would be able to detect spin by turning their heads quickly, or by watching the arcs of items dropped or thrown. The size of the colony would also provide a great deal of radiation shielding via its atmosphere and thick glass walls – indeed, the internal size of the colony would be so great that it would produce its own weather systems.
The issue of sunlight is solved with the now-familiar application of giant mirrors, which could turn to simulate day and night, with large bays of solar collectors powering the station.
The one major issue with the design was that the stations would need to be constantly pointed toward the sun for habitation to be possible. Conventionally, attitude adjustment is made with rockets or other chemical methods, but the mass required for constant stationkeeping adjustments would be impractical. O’Neill and his students designed a complex system of counter-rotations involving a second cylinder that would keep both cylinders pointed in the right direction without the use of rockets.
The O’Neill designs inspired thousands. The L5 Society and by proxy many other space groups grew from the research he and his students conducted, and a whole movement dedicated to seeing human colonization of space arose. It was one of the first times that the concept had been pushed so hard, not only amongst scientists and space agencies, but toward the general public as well. The research was extensive and the science and work behind the concepts was sound, but importantly the PR and public outreach was equally extensive. The original summer study paper discussed everything from population distribution to deep space research. It is a fascinating read that provides a wide range of sensible, feasible ideas as well as justifications for the construction of a large scale habitat.
The stations are not without their flaws. The designs do not allow for natural sunlight, requiring a great set up of prisms and mirrors to reflect sunlight into the structure. Many of the designs are overly complex in their layout and there are several areas which the advancement of our understanding of space could lead to a great deal of improvement.
Safety concerns are one of the foremost problems plaguing these structures. Failure of the rotational mechanisms could very quickly lead to a catastrophic failure of the habitat itself. The reliance on rotation to produce gravity would require a great deal of maintenance and the counter-rotation design of the O’Neill cylinder seems vulnerable to all manner of issues. Furthermore, several unknowns discussed in this article series hinder these designs – radiation, micro impacts, and asteroids are still unexplored areas aside from a scant few experiments outside of Earth’s atmosphere, to say nothing of the issue inherent in maintaining the atmospheres and large scale farming that each design requires.
While the actual construction of these frontier towns may be a relatively simple affair in the grand scheme of things, the material requirements and large scale infrastructure required by any of these projects is immense, and our current space-industry level is nowhere near the scale required for such an undertaking. O’Neill first suggested moon bases and rail-guns to transport materials to building sites; this idea was later supplanted with the asteroid mining concept utilized by most experts in the subject to date. The fact remains that regardless of where the materials come from, we have a long road ahead of us to achieve O’Neill’s vision and that of the generation he inspired.
Next time on Living In Space, we take a look at where Space Colonization is now, what designs have come since the 70s and ask, is humanity ready to leave its cradle?
Although, technically the idea was floated by many scientists before Von Braun. Notably the Soviet scientist Konstantin Tsiolkovsky suggested rotation to produce gravity in the early 1900s. Slovenian scientist Herman Potocnik even constructed a working model of the design.
For an extended discussion on the fabrication process – http://www.nss.org/settlement/nasa/75SummerStudy/Chapt4.html#Fab
Although a later study would show that the mirrors would not work quite as intended and would have to be reworked.
In classic O’Neill style, Gerard suggested that this effect could produce interesting recreation and sport potential in addition to the recreation and sports suggested for the zero-gravity center of the cylinder (Zero Gravity Ballet, for one)
Detailed in The High Frontier | 0.863205 | 3.163196 |
Apart from ancient detrital zircons no dated materials from the Earth’s crust come anywhere near the age when our home world formed, which incidentally was derived by indirect means. Hutton’s famous saying towards the close of the 18th century, ‘The result, therefore, of our present enquiry is, that we find no vestige of a beginning, – no prospect of an end’ seems irrefutable. Hardly surprising, you might think, considering the frantic pace of events that have reworked the geological record for four billion years and convincing evidence that not long after accretion the Moon-forming collision may have melted most of the early mantle. But there is a way of peering beyond even that definitive catastrophe. The metal tungsten, as anyone from the steel town of Rotherham will tell you, alloys very nicely with iron and makes it harder, stronger and more temperature resistant. Most of the Earth’s original complement of tungsten probably ended up in the core; it is a siderophile element. But traces can be detected in virtually any rock and, of course, in W-rich ore bodies. Its interest to modern-day geochemists lies in its naturally occurring isotopes, particularly 182W, a proportion of which forms by decay of a radioactive isotope of hafnium (182Hf). Or rather it did, for 182Hf has a half-life of about 9 million years. Only a vanishingly small amount from a nearby supernova that may have triggered formation of the solar system remains undecayed.
A sign of the former presence of 182Hf in the early Earth comes from higher amounts of its daughter isotope 182W in some Archaean rocks (3.96 Ga) than in younger rocks. That excess is probably from undecayed 182Hf in asteroidal masses that bombarded the Earth between 4.1 and 3.8 Ga. Now it turns out that some much younger flood basalts from the Ontong Java Plateau on the floor of the West Pacific Ocean (~120 Ma) and Baffin Island in northern Canada (~60 Ma) also contain anomalously high 182W/184W ratios (Rizo, H. et al. 2016. Preservation of Earth-forming events in the tungsten isotopic composition of modern flood basalts. Science, v. 352, p. 809-812; see also: Dahl, T.W. 2016. Identifying remnants of early Earth. Science, v. 352, p. 768-769). A different explanation is required for these occurrences. The flood basalts must have melted from chemically anomalous mantle, which originally contained undecayed 182Hf. The researchers have worked out that this heterogeneity stems from a silicate-rich planetesimal that had formed in the first 50 Ma of the solar system’s history, and was accreted to the Earth before the Moon-forming event – lunar rocks formed after 182Hf became extinct. That catastrophe and the succeeding 4.51 Ga of mantle convection failed to mix the ancient anomaly with the rest of the Earth. | 0.814318 | 3.691403 |
Juno is a NASA’s space probe orbiting Jupiter. Launched from Cape Canaveral Air Force Station on August 5, 2011, Juno entered a polar orbit of Jupiter on July 5, 2016. It is powered by solar arrays, the three largest solar array wings ever deployed on a planetary probe play a role in stabilizing the spacecraft as well as generating power.
The spacecraft traveled 2.8 billion kilometers to reach Jupiter and is designed to orbit Jupiter 37 times throughout its mission. This was originally planned to take 20 months. Juno is currently investigating Jupiter’s composition, gravity field, magnetic field, polar magnetosphere, core, the amount of water present within the deep atmosphere, mass distribution, and its deep winds.
The spacecraft’s name comes from the Roman goddess Juno, Jupiter’s wife. In the mythology, Jupiter drew a veil of clouds around himself to hide his mischief, and Juno was able to peer through the clouds and reveal Jupiter’s true nature. It is precisely the story that spacecraft Juno is telling now.
NASA’s Juno Caught Storms on Jupiter in New Stunning Images
Jupiter’s clouds are composed mostly of ammonia and hydrogen sulfide. And Juno captured on its approach in February this year a sparkling image of the real Jupiter: its stormy southern side. So far, Juno found a lot about Jupiter, like the fact that it has a very diffuse core, mixed into the mantle.
Jupiter is a gas giant with a mass two-and-a-half times of all the other planets in the Solar System combined. This is how it got the name of the Roman god of the sky and thunder, and the king of the gods in Ancient Roman religion and mythology. Also, a “Jupiter mass” is often used as a unit to describe masses of other objects, particularly extrasolar planets and brown dwarfs.
The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence and storms along their interacting boundaries. Like the other giant planets, Jupiter lacks a well-defined solid surface. This Jupiter’s marriage with Juno will end by July 30, 2021. | 0.854926 | 3.085248 |
Image credit: NASA/JPL
Out of the dark and dusty cosmos comes an unusual valentine ? a stellar nursery resembling a shimmering pink rosebud. This cluster of newborn stars, called a reflection nebula, was captured by state-of-the-art infrared detectors onboard NASA’s new Spitzer Space Telescope, formerly known as the Space Infrared Telescope Facility.
“The picture is more than just pretty,” said Dr. Thomas Megeath, principal investigator for the latest observations and an astronomer at the Harvard Smithsonian Center for Astrophysics, Cambridge, Mass. “It helps us understand how stars form in the crowded environments of stellar nurseries.”
Located 3,330 light-years away in the constellation Cepheus and spanning 10 light-years across, the rosebud-shaped nebula, numbered NGC 7129, is home to some 130 young stars. Our own Sun is believed to have grown up in a similar family setting.
Previous images of NGC 7129 taken by visible telescopes show a smattering of hazy stars spotted against a luminescent cloud. Spitzer, by sensing the infrared radiation or heat of the cluster, produces a much more detailed snapshot. Highlighted in false colors are the hot dust particles and gases, respectively, which form a nest around the stars. The pink rosebud contains adolescent stars that blew away blankets of hot dust, while the green stem holds newborn stars whose jets torched surrounding gases.
Outside of the primary nebula, younger proto-stars can also be seen for the first time. “We can now see a few stars beyond the nebula that were previously hidden in the dark cloud,” said Megeath.
In addition, the findings go beyond what can be seen in the image. By analyzing the amount and type of infrared light emitted by nearly every star in the cluster, scientists were able to determine which ones support the swirling rings of debris, called circumstellar discs, which eventually coalesce to form planets. Roughly half of the stars observed were found to harbor discs.
These observations will ultimately help astronomers determine how stellar nurseries shape the development of planetary systems similar to our own.
Launched on August 25, 2003, from Cape Canaveral Air Force Station, Florida, the Spitzer Space Telescope is the fourth of NASA?s Great Observatories, a program that also includes the Compton Gamma Ray Observatory, Chandra X-ray Observatory and Hubble Space Telescope.
JPL manages the Spitzer Space Telescope mission for NASA’s Office of Space Science, Washington, D.C. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. JPL is a division of Caltech.
Additional information about the Spitzer Space Telescope is available at http://www.spitzer.caltech.edu.
Original Source: NASA/JPL News Release | 0.889149 | 3.878697 |
One day, my Grade Nine science class got way more interesting.
Suddenly, volcanoes weren’t just something in textbooks. Though I was in neighbouring British Columbia when Mt. St. Helens erupted, there was still a layer of ash on our cars and everything else. For a teenager with a burgeoning interest in science, it was awesome.
Continue reading “40 Years Ago, Mount St. Helens Blew its Top Off”
In between the Indonesian islands of Java and Sumatra lies the Sunda Strait. And in the Sunda Strait lies the much smaller island of Anak Krakatau, one of Earth’s active volcanoes. It’s erupted more than 50 times in the past 2,000 years, and now it’s doing it again.
Continue reading “Anak Krakatau Erupted a Few Days Ago. Here’s What it Looked Like From Space”
200 million years ago, a mass extinction event wiped out about 76% of all species on Earth—both terrestrial and marine. That event was called the end-Triassic extinction, or the Jurassic-Triassic (J-T) extinction event. At that time, the world experienced many of the same things as Earth is facing now, including a warming climate and the acidification of the oceans.
A new paper shows that pulses of volcanic eruptions were responsible, and that those pulses released the same amount of CO2 as humans are releasing today.
Continue reading “During Mass Extinction Events, Volcanoes Were Releasing About the Same Amount of CO2 as We Are Today”
Despite the similarities our world has with Venus, there is still much don’t know about Earth’s “Sister planet” and how it came to be. Thanks to its super-dense and hazy atmosphere, there are still unresolved questions about the planet’s geological history. For example, despite the fact that Venus’ surface is dominated by volcanic features, scientists have remained uncertain whether or not the planet is still volcanically active today.
While the planet is known to have been volcanically active as recent as 2.5 million years ago, no concrete evidence has been found that there are still volcanic eruptions on Venus’ surface. However, new research led by the USRA’s Lunar and Planetary Institute (LPI) has shown that Venus may still have active volcanoes, making it the only other planet in the Solar System (other than Earth) that is still volcanically active today.
Continue reading “The Surprising Possibility That There are Still Active Volcanoes on Venus”
A surtseyan eruption is a volcanic eruption in shallow water. It’s named after the island Surtsey, off the coast of iceland. In 2015, a surtseyan eruption in the Tongan Archipelago created the island Hunga Tonga-Hunga Ha‘apai. Despite the odds, that island is still there almost five years later.
Continue reading “A Brand New Island in the Pacific has Survived 5 Years” | 0.840445 | 3.319512 |
Discovery of a new mechanism to destroy dust grains in strong radiation fields
We report a new mechanism of dust destruction based on centrifugal force within extremely fast-rotating grains spun-up by radiative torques, which can successfully explain unusual properties of dust grains observed in the local environment of supernovae and massive stars.
Massive stars, supernovae, and kilonovae are among the most luminous radiation sources in the universe. Observations usually show near- to mid-infrared (NIR--MIR, wavelength between 1-5 micron) emission excess from ionized regions around massive stars. Early phase observations in optical to NIR wavelengths of type 1a supernovae also reveal unusual properties of dust extinction and dust polarization. The popular explanation for such NIR-MIR excess and unusual dust properties is the predominance of small grains (size tens of nanometers) relative to large grains (size of hundreds of nanometers) in the local environment of these strong radiation sources. The question of why small grains might be predominant remains mysterious. In this paper, we reported a new mechanism of dust destruction based on centrifugal force within extremely fast-rotating grains spun-up by radiative torques, which can successfully explain this puzzle.
Why do we care about cosmic dust?
Dust is ubiquitous in the Universe, and it is usually said that “From dust we came, and to dust we shall return.” Dust is the building blocks of stars and planets. Dust can drive the mass loss in stellar winds at the end of star’s life. Dust is also the home where water ice and complex organic molecules, including biogenic molecules, are formed. Dust grains absorb starlight in optical and ultraviolet wavelengths and re-emit radiation at long, infrared wavelengths. The infrared emission from dust is a powerful tool for astronomers to study the Universe.
Therefore, lots of research have been done to understand evolution and physical properties (e.g., size and shape) of dust. Previous studies establish that the mass of interstellar dust is dominated by large grains having a radius of hundreds of nanometers. Yet, many early-phase observations toward type Ia supernovae reveal the predominance of nanometer-sized grains (with radius of tens of nanometers) over large grains. We also see similar properties in ionized-regions around massive stars and in star-forming regions of nearby and high-redshift galaxies. This anomaly cannot be explained by current understanding of dust formation and destruction including thermal sublimation by intense radiation, sputtering in the hot gas, and grain shattering in shocks.
What is our discovery?
In a new paper published in Nature Astronomy, we discovered that, exposed to an intense radiation field such as from a supernova, massive star, or a kilonova, dust grains in the local environment can be spun-up to extremely fast rotation, above one billion rounds per second. As a result, the centrifugal force within the rapidly rotating grain can exceed the maximum tensile strength of grain material, which disrupts a dust grain into a number of nanometer-sized grains. We term this mechanism Radiative Torque Disruption (RATD). Comparing to other destruction mechanisms, we find that RATD is the fastest mechanism to destroy dust grains in intense radiation fields such as near massive stars, supernovae, and kilonovae.
Why is this discovery important?
The discovery changes the current understanding of cosmic dust evolution.
In the current paradigm, an intense radiation field heats dust grains to high temperatures and evaporate them into the gas phase, the so-called thermal sublimation mechanism. Our discovery shows that the strong radiation field can also spin-up grains to extremely fast rotation, such that the resulting centrifugal stress can disrupt them into tiny fragments. The new mechanism requires much lower radiation intensity and is thus more efficient than thermal sublimation.
The discovery resolves several longstanding puzzles revealed by observations.
The production of nanometer-sized grains by disruption of large grains via the RATD mechanism on a short time-scale of less than a few weeks can successfully explain the unusual dust properties observed toward many type Ia supernovae. The reproduction of nanoparticles can also clarify the mysterious origin of near-to-mid-infrared emission excess observed in ionized regions around massive stars. The discovered mechanism can explain a steep far-UV rise in the in extinction curves towards starburst and high-redshift galaxies, and the decrease of the escape fraction of Lyman α photons from H II regions surrounding young massive star clusters. This work opens a new avenue to study the internal structure, composition, and grain size distribution of dust grains via observations.
The full article is accessible via this link: https://www.nature.com/articles/s41550-019-0763-6
Lastly, forty years ago, in 1979, Edward Purcell, the Nobel laureate in Physics, concluded that interstellar grains of compact structures would not be disrupted by centrifugal force as a result of grain suprathermal rotation. Our study yet shows that even compact grains can be disrupted by centrifugal force when they are located near an intense radiation field, which is quite common in the Universe.
This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education (2017R1D1A1B03035359). | 0.800337 | 4.22959 |
Hey, stargazers! Or planetgazers in this case? Anywho, Neptune is next up this year on the list of planets at opposition, meaning Earth is in the process of passing between it and the Sun; therefore, tonight Neptune will be in a prime position to be viewed as clearly and closely than at any other time of the year. Currently, the Blue Planet is hanging out in the constellation of Aquarius, where it will rise on the south-eastern horizon.
Fun Fact: Neptune wasn’t always called Neptune. Before that, it was known as LeVerrier (after the French astronomer credited for its discovery), Janus, and Oceanus.
When not at opposition, Neptune orbits much further out in the solar system than Earth – thirty times farther away from the Sun, actually. It takes Neptune approximately 164 Earth years to complete its orbit around the Sun. Much like the other outer planets, Neptune has a ring system, although the rings are very faint. They are primarily composed of ice particles and carbon-based grains of dust.
Neptune has two active storms called the Great Dark Spot, roughly the size of Earth, and the Small Dark Spot, which is around the same size as Earth’s Moon. In its upper atmosphere, these regions brew with powerful high-speed solar winds that have been clocked at up to 832 miles/1,340 kilometers per second. In 1989, there was one particular sticky storm found in the Great Dark Spot that hung on for five years. Talk about a serious Stage-5 clinger.
The planet has fourteen known moons, the largest being Triton, which is a frozen world and one of the frostiest in our solar system as it perpetually generates particles of nitrogen ice and dust from the dark depths of its soul, er, surface. It is believed that Triton was buzzing around minding its own business when it got caught by the immense gravitational pull of Neptune, and whelp, the rest is history. Raise your hand if you can relate to this scenario.
You can find Triton on our Moons of the Solar System necklace!
Over the upcoming weeks following its opposition, Neptune will reach its highest point in the sky four minutes earlier each night. It will be in the same ideal viewing position around-ish this time over the next handful of years on September 11, 2020, September 14, 2021 and September 16, 2022, if you are wondering (because of course you are).
Have a sweet spot for (or pic of) Neptune? Feel free to share your thoughts in the comments! | 0.846147 | 3.492664 |
From Cambridge, it will be visible in the morning sky, becoming accessible around 18:07, when it rises to an altitude of 7° above your eastern horizon. It will then reach its highest point in the sky at 00:05, 57° above your southern horizon. It will be lost to dawn twilight around 05:59, 8° above your western horizon.
Mars opposite the Sun
This optimal positioning occurs when Mars is almost directly opposite the Sun in the sky. Since the Sun reaches its greatest distance below the horizon at midnight, the point opposite to it is highest in the sky at the same time.
At around the same time that Mars passes opposition, it also makes its closest approach to the Earth – termed its perigee – making it appear at its brightest and largest.
This happens because when Mars lies opposite the Sun in the sky, the solar system is lined up so that Mars, the Earth and the Sun form a straight line with the Earth in the middle, on the same side of the Sun as Mars.
The time of Mars's perigee is an especially good time to observe it, since it neighbors the Earth in the solar system and has the greatest variation of all of the planets in its distance from the Earth. This in turn leads to a large variation in its apparent size and brightness.
When it passes opposition, Mars glides past the Earth rather quickly, and so only appears large and bright in the sky for a few weeks. A graph of the angular size of Mars at this opposition is available here, and a graph of its brightness is available here.
On this occasion, Mars will lie at a distance of 0.67 AU, and its disk will measure 13.9 arcsec in diameter, shining at magnitude -1.2. Even at its closest approach to the Earth, however, it is not possible to distinguish it as more than a star-like point of light without the aid of a telescope.
Mars in coming weeks
Over the weeks following its opposition, Mars will reach its highest point in the sky four minutes earlier each night, gradually receding from the pre-dawn morning sky while remaining visible in the evening sky for a few months.
The position of Mars at the moment it passes opposition will be:
|Object||Right Ascension||Declination||Constellation||Magnitude||Angular Size|
The coordinates above are given in J2000.0.
|The sky on 03 March 2012|
11 days old
All times shown in EST.
The circumstances of this event were computed using the DE405 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.
|03 Mar 2012||– Mars at opposition|
|05 Mar 2012||– Mars at perigee|
|24 Jan 2013||– Mars at perihelion|
|17 Apr 2013||– Mars at solar conjunction| | 0.878111 | 3.74914 |
The physics of decay and origin of carbon 14 for the radiocarbon dating 1: We can indirectly date glacial sediments by looking at the organic materials above and below glacial sediments. Radiocarbon dating provides the age of organic remains that overly glacial sediments. It was one of the earliest techniques to be developed, during the s.
Can We Fix It? Carbon fluxes on glacier surfaces
Radiocarbon dating works because an isotope of carbon, 14 C, is constantly formed in the atmosphere by interaction of carbon isotopes with solar radiation and free neutrons. Living organisms absorb carbon for example, we breathe it in. This carbon is therefore present in their bodies and bones. In the figure right, the production of radio-active carbon is demonstrated.
Here, 7 protons and 7 neutrons N plus one neutron form an isotope of carbon, with 8 neutrons and 6 protons. These 14 C atoms are rapidly oxidised into carbon dioxide 12 CO 2 , and are then absorbed by living organisms and oceans. In Antarctica, where organic remains are rare, this usually means dating microscopic marine organisms in glaciomarine muds that overly glacial tills and sediments on the continental shelf.
Radiocarbon dating marine organisms has added complications in Antarctica, because around the Antarctic continent old deep ocean currents up well. Rates of radiocarbon production vary through time, in a quasi-periodic manner.sturpunfide.tk
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It is therefore necessary to distinguish between radiocarbon years 14 C and calendar years. These two ages can be reconciled using calibration against a chronology of calendar years. Tree ring data has been widely used to calibrate the timescales, as tree rings provide an annual calendar year, and the wood can be radiocarbon dated to provide a calibration. This is crucial data for numerical ice sheet models. As well as using cosmogenic nuclide dating to work out the past extent of ice sheets and the rate at which they shrank back, we can use it to work out ice-sheet thicknesses and rates of thinning[5, 6].
Sampling and dating boulders in a transect down a mountain will rapidly establish how thick your ice sheet was and how quickly it thinned during deglaciation. Many mountains have trimlines on them, and are smoothed and eroded below the trimline, and more weathered with more evidence of periglaciation above the trimline. Trimlines can therefore also be used to reconstruct past ice sheet thickness. However, this can be difficult, as thermal boundaries within the ice sheet may mean that it is more erosive lower down than higher up, and that cold, non-erosive ice on the tops of mountains may leave in tact older landscapes.
Cosmogenic nuclide dating can also be used in this context to understand past ice-sheet thicknesses and changes in subglacial thermal regime. Sampling strategy is the most important factor in generating a reliable exposure age. Several factors can affect cosmogenic nuclide dating: Geologists must ensure that they choose an appropriate rock. Granite and sandstone boulders are frequently used in cosmogenic nuclide dating, as they have large amounts of quartz, which yields Beryllium, a cosmogenic nuclide ideal for dating glacial fluctuations over Quaternary timescales.
For a rock to be suitable for cosmogenic nuclide dating, quartz must occur in the rock in sufficient quantities and in the sufficient size fraction. A general rule of thumb is that you should be able to see the quartz crystals with the naked eye. Bethan Davies sampling a boulder for cosmogenic nuclide dating in Greenland. Rock samples may be collected with a hammer and chisel or with a rock saw. This can take a very long time! Frost heave in periglacial environments can repeatedly bury and exhume boulders, resulting in a complex exposure age.
One of the largest errors in cosmogenic nuclide dating comes from a poor sampling strategy. Because cosmic rays only penetrate the upper few centimetres of a rock, movement of a boulder downslope can result in large errors in the age calculated. Before sampling a rock, geologists must take detailed and careful measurements of the landsurface, and satisfy themselves that the rock is in a stable position, has not rolled, slipped downslope, been repeatedly buried and exhumed during periglacial rock cycling within the active layer frequently a problem with small boulders , and has not been covered with large amounts of soil, snow or vegetation.
Scratches striations on a sandstone boulder show that it has undergone subglacial transport and erosion. They want to sample a rock that they are sure has undergone subglacial transport. They will therefore sample boulders that are subrounded, faceted, bear striations, or show other signs of subglacial transport.
Bethan Davies cosmogenic nuclide sampling a sandstone boulder on a moraine. Cosmogenic nuclide production rates vary according to latitude and elevation. These factors must be measured by the scientist, and are accounted for in the calculation of the exposure age. Topographic shielding, for example by a nearby large mountain, also affects the production rate of cosmogenic nuclides. This is because the cosmic rays, which bombard Earth at a more or less equal rate from all sectors of the sky, will be reduced if the view of the sky is shielded — for example, by a large mountain that the rays cannot penetrate.
Scientists must therefore carefully measure the horizon line all for degrees all around their boulder.
Solifluction lobes on the Ulu Peninsula. Solifluction is common in periglacial environments, and can result in rolling, burial and movement of boulders on slopes. As mentioned above, sampling strategy is the most import factor in generating a reliable cosmogenic nuclide age.
Dating Glacial Sediments
Post-depositional processes, such as rolling, burial, exhumation or cover with vegetation can result in interruption of the accumulation of cosmogenic nuclides and a younger than expected age. Alternatively, if the boulder has not undergone sufficient erosion to remove previously accumulated cosmogenic nuclides, it will have an older than expected age. This is called inheritance. This can be a particular problem in Antarctica, where cold-based ice may repeatedly cover a boulder, preventing the accumulation of cosmogenic nuclides, without eroding or even moving the rock.
Rocks can therefore be left in a stable position or moved slightly, without having suffiicient erosion to remove cosmogenic nuclides from a previous exposure. This can result in a complex exposure history. This is typically characterised by spread of exposure ages across a single landform. Dating just one boulder from a moraine may therefore be an unreliable method to rely on.
Scientists may also screen for complex exposure by using two different isotopes, such as aluminium and beryllium 26 Al and 10 Be. The Production Rate of cosmogenic nuclides varies spatially, but is generally assumed to have remained constant at a particular location. Published production rates are available for different parts of the Earth. Glacial geologists target elements that only occur in minerals in rocks, such as quartz, through cosmic-ray bombardment, such as aluminium and beryllium 26 Al and 10 Be.
Beryillium is used most widely, as it has the best determined production rate and can be measured at low concentrations. Chlorine 36 Cl can also be used to date the exposure age of basalt lavas. Bethan Davies using HF to dissolve rocks for cosmogenic nuclide dating. Note the personal protection equipment!
The first stage in the calculation of a cosmogenic nuclide exposure age is to extract the quartz from a rock. This is quite an involved process and means using some quite dangerous chemicals, such as HF Hydrogen Flouride. HF is an acid with a pH of about 3, but the small molecule is easily absorbed by your skin.
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Once absorbed, it reacts vigorously with the calcium in your bones, forming Calcium Flouride which may then be deposited in your arteries. All in all, not a substance you want to get on your skin!
Scientists must therefore take strong precautions before using this chemical. The first stage is to crush the rock or rock fragments in a jaw crusher. The crusher must be perfectly clean to avoid contamination. The crushed rock is then sieved to the right size. Magnetic seperation removes particles with lots of iron such as micas , leaving you if you sampled granite, for example with a g sample of sand, comprising mostly feldspar and quartz.
About Bethan Davies
Feldspar is removed by placing the sample in Hexafloursilicic acid or HF on a shaking table for around 2 weeks. The acids are changed daily. The more durable quartz is left behind. A series of chemical precipitations leaves you with Beryllium Oxide BeO , a white powder. It is mixed with Niobium NB and pressed into a copper cathode. Once the ratio of cosmogenic to naturally occuring isotopes has been calculated, the production rate is used to calculate an exposure age. | 0.801251 | 3.026023 |
Crescent ♍ Virgo
Moon phase on 20 July 2023 Thursday is Waxing Crescent, 2 days young Moon is in Leo.Share this page: twitter facebook linkedin
Previous main lunar phase is the New Moon before 2 days on 17 July 2023 at 18:32.
Moon rises in the morning and sets in the evening. It is visible toward the southwest in early evening.
Lunar disc appears visually 6.6% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1768" and ∠1888".
Next Full Moon is the Sturgeon Moon of August 2023 after 12 days on 1 August 2023 at 18:31.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 2 days young. Earth's natural satellite is moving from the beginning to the first part of current synodic month. This is lunation 291 of Meeus index or 1244 from Brown series.
Length of current 291 lunation is 29 days, 15 hours and 6 minutes. It is 56 minutes shorter than next lunation 292 length.
Length of current synodic month is 2 hours and 22 minutes longer than the mean length of synodic month, but it is still 4 hours and 41 minutes shorter, compared to 21st century longest.
This New Moon true anomaly is ∠155.7°. At beginning of next synodic month true anomaly will be ∠179.2°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
Moon is reaching point of apogee on this date at 06:56, this is 15 days after last perigee on 4 July 2023 at 22:28 in ♑ Capricorn. Lunar orbit is starting to get closer, while the Moon is moving inward the Earth for 12 days ahead, until it will get to the point of next perigee on 2 August 2023 at 05:52 in ♒ Aquarius.
This apogee Moon is 406 291 km (252 458 mi) away from Earth. It is 883 km farther than the mean apogee distance, but it is still 418 km closer than the farthest apogee of 21st century.
9 days after its ascending node on 11 July 2023 at 01:23 in ♉ Taurus, the Moon is following the northern part of its orbit for the next 5 days, until it will cross the ecliptic from North to South in descending node on 25 July 2023 at 15:05 in ♎ Libra.
9 days after beginning of current draconic month in ♉ Taurus, the Moon is moving from the beginning to the first part of it.
4 days after previous North standstill on 16 July 2023 at 02:40 in ♋ Cancer, when Moon has reached northern declination of ∠27.849°. Next 9 days the lunar orbit moves southward to face South declination of ∠-27.924° in the next southern standstill on 30 July 2023 at 11:13 in ♑ Capricorn.
After 12 days on 1 August 2023 at 18:31 in ♒ Aquarius, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.83659 | 3.186822 |
While conducting a Dark Energy Survey (DES) beyond Neptune, a team of scientists, led by a grad student at the University of Pennsylvania, have identified 139 new TNOs (trans-Neptunian objects). TNOs are any "minor planets" (asteroids, dwarf planets, and other similar objects) that orbit the Sun beyond Jupiter.
Astronomers have spotted hundreds of tiny worlds lurking in the deep, dark outer reaches of the solar system, beyond the orbit of Neptune.
These minor planets, known as trans-Neptunian objects (TNOs), “are relics of major dynamical events among and beyond the giant planets,” according to a study published this week in The Astrophysical Journal Supplement Series.
Some 139 new TNOs, out of 316 detections total, are reported in the study, which was led by Pedro Bernardinelli, a graduate student in physics and astronomy at the University of Pennsylvania. That’s a big haul considering that the current catalog of TNOs contains only about 3,000 objects, and was possible thanks to the Dark Energy Survey (DES) at the Victor M. Blanco Telescope in Chile.
The team has only analyzed 4 of the 6 years of collected data. When finished, they suspect they will add around another 200 TNOs to their tally.
Read the rest of the piece on Vice. | 0.881087 | 3.131945 |
It has been a great run for the planet Venus. Going back to late November this dazzling world has dominated our western evening sky. It is a special planet: Earth's sister, coming nearest to us, very much alike in size, and perpetually covered by thick clouds that make it an excellent reflector of light. The dazzling, silvery white planet shines brighter for us than any other planet in the night sky. During late March and April, Venus soared high into the sky. For observers of north-temperate latitudes this was the highest evening appearance of its eight-year cycle. More on that later.
Also in early April, Venus glided through the southern fringe of the Pleiades star cluster, and toward the end of the month telescopes and steadily held binoculars showed it to be a narrowing crescent as Venus approached the Earth. It grew longer and more concave and as the resultant illuminated area continued to grow progressively larger, its brilliance grew even greater, reaching a pinnacle near the end of the month.
On May 4, Venus reached its greatest declination north (its greatest angular distance north of the celestial equator) in its eight-year cycle, and its greatest (27.82 degrees) until the year 2239. But ever since, Venus has been in a sort of "celestial freefall."
Related: Examining the phases of Venus
Venus not only has been growing wider and slimmer (and subsequently a bit dimmer), but it's now plunging sunward at more than a degree per day as it whirls toward us in space. By month's end it will be, to say the least, very challenging to see: only 2 degrees above the west-northwest horizon just 20 minutes after sunset.
But while Venus rapidly falls, another planet is coming into view and is rapidly ascending in the evening twilight sky: Mercury.
A rendezvous on Thursday night
This smallest and fastest-moving planet (only 1.4 times wider than our moon) orbits the sun just a little over four times per year (4.15 time to be precise), but from our moving viewpoint on Earth it appears to go around only 3.15 times. On average, each year it makes about 3.5 swings into the morning sky and as many into the evening. But each apparition into either the morning or evening sky is markedly different thanks to its very eccentric orbit and the various viewing angles from which we can see it.
On May 4, Mercury was at superior conjunction and passed directly behind the disk of the sun from Earth's perspective, moving from west to east (or from right to left), after which it entered the evening sky. We now can see it, shining almost as brightly as Sirius, the brightest star in Earth's night sky, shining directly below Venus.
And come Thursday (May 21), the two planets will come closest together, like two ships passing in the night (or in this case, twilight). About 45 minutes after sunset, look low near the west-northwest horizon. Glaring Venus will of course, stand out against the twilight sky. Mercury will be 1.1 degrees below and slightly to the left. Although shining very bright in its own right, Mercury glows with only 4% the radiance of Venus. Binoculars will make sighting Mercury easy, although you should also be able to pick it out with your naked eye.
After Thursday night, the two planets will continue to go on their separate ways; Mercury continuing its steep climb upward, while Venus continues to rapidly fall downward. But one more event is still to occur. On Sunday (May 24), once again, concentrate low near the west-northwest horizon about 45 minutes after sunset. Venus will be there, albeit lower than it was just a few days ago. Mercury has now shifted 5.5 degrees to Venus's upper left. And 6.5 degrees to the upper left of Mercury you'll sight a slender waxing crescent moon.
For sport, try sighting the moon on Saturday (May 23). It will be thinner and much lower, sitting to the lower left of Venus.
Ironically, as Venus bids a fond adieu to evening viewers at month's end, Mercury will be at its best, still shining bright at zero magnitude and setting nearly two hours after sundown, minutes from the end of evening twilight.
Same time and place (almost) every eight years
There is a highly noticeable rhythm in the motion of Venus: after eight years it returns to the same place in the sky on the same date. This was known and of great interest to ancient peoples such as the Mayans.
This happens because Venus goes around the sun an integral number of times — 13 — in eight years. The sidereal year of Venus — the amount of time it takes to complete one orbit around the sun — is 225 days (more precisely 224.7) and there are almost exactly 13 of these Venus-years in eight Earth years. The planet's synodic period, or the time it takes Venus to return to the same position in Earth's sky, is 584 days, and there are five of these in eight years. So, the behavior of Venus in 2012 repeats in 2020, 2013 repeats in 2021, and so on.
But actually I should insert a slight revision here. After eight years it returns almost to the same place in the sky on the same date. In actuality, it arrives almost to the same place two or three days shy of eight years. And when I say "almost to the same place," I'm talking about a relatively small difference measuring a little more than a few tenths of a degree.
But such slight discrepancies are significant enough to deny us a view of an exceedingly rare celestial sight that occurred both in 2004 (on June 8) and 2012 (on June 5): A transit of Venus. Indeed, durings its last two eight-year cycles, Venus actually crossed in front of the sun and appeared in silhouette as a black dot about 3% the diameter of the sun's disk.
Such transits occur in pairs, each separated by eight years. But after the second transit, there comes a wait of over a century before the next takes place. The next time Venus crosses the sun will be on Dec. 11, 2117, though that will not be visible anywhere in the Western Hemisphere. But on Dec. 8, 2125, North America will be in an excellent position to watch as Venus again crosses the sun.
As for what happens this year, on June 3, at 1:36 p.m. EDT (1536 GMT), Venus will pass just 13.25 arc minutes or 0.22 degrees north of the sun's uppermost edge. Close ... but no cigar (or transit).
Rest of 2020: A morning wanderer
As for the rest of this year, Venus climbs less steeply out into morning twilight visibility, perhaps as early as June 6 (only 15 minutes before sunrise; use binoculars), though much better placed for making a sighting only a week later.
For the rest of the year it pulls away from us, passing about a degree north of the bright orange star Aldebaran during the second week of July, and soaring well up into the eastern predawn sky in August and September, though not quite so high as it did in March and April. Thereafter, it will spend the rest of the year sinking toward its passage behind the sun in March 2021.
Editor's note: If you have an amazing night sky photo you'd like to share for a possible story or image gallery, you can send images and comments to [email protected].
- When, where and how to see the planets in the 2020 night sky
- Rare sight: Crescent Venus, Mercury spotted in daytime sky (photos)
- Venus and Mercury sparkle over Rome (photo)
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers' Almanac and other publications. Follow us on Twitter @Spacedotcom and on Facebook. | 0.823025 | 3.844933 |
Christmas will come early for Australia’s budding astronomers, with not one but two space spectacles scheduled for Friday night.
The Christmas Comet – which is named for the time of year it appears – is expected to emerge from 9pm AEDT as a green and fuzzy comet in the east, close to the constellation known as Orion, or the Saucepan, ANU astronomer Dr Brad Tucker said.
“The green colour is coming from the gas that is coming off the comet,” he told AAP.
“There is a bunch of ice on it and methane – it’s essentially like a dirty snowball and so when it goes around the sun it melts … and is a steamy, stinky green glow.”
This will be rare chance for Australians will have to catch a glimpse of the comet, which appears only once every five years.
The Christmas Comet and the Geminid meteor shower are due to light up the night sky within just hours of one another.
Hours later shooting stars are set to flash across the sky as Earth passes through the tail of the 3200 Phaethon asteroid.
They’ll look impressive from the ground but the falling stars are actually just small rocks that have broken off from the asteroid before burning up in the Earth’s atmosphere.
“They’re about the size of a grain of sand, or even a small pebble and they’re travelling tens of thousands of kilometres an hour,” Dr Tucker said.
While observers will need a pair of binoculars or a telescope to catch the Christmas Comet, the meteor shower will be visible from anywhere in Australia, even major cities, so long as it’s a clear night.
“It’s very accessible, you don’t need anything special, you just need the night sky,” Dr Tucker said. | 0.835758 | 3.047344 |
Methane Debate Splits Mars Community
This image shows concentrations of methane discovered on Mars. Credit: NASA
Observations over the last decade suggest that methane clouds form briefly over Mars during the summer months. The discovery has left many scientists scratching their heads, since it doesn’t fit into models of the martian atmosphere.
"The reports are extraordinary," says Kevin Zahnle of NASA Ames Research Center. "They require methane to have a life time of days or weeks in the martian atmosphere, which disagrees with the known behavior of methane by at least a factor of 1000."
Zahnle and his colleagues have expressed some serious doubts about the existence of methane on Mars in a paper that appeared last December in the journal Icarus.
"What we say is that the evidence is not nearly strong enough for us to suspend our trust in the known chemical behavior of methane," he says.
But the observers are not backing down.
"We stand by our results," says Michael Mumma of NASA’s Goddard Space Flight Center, who leads one of the groups that made the methane observations. "True, the measurement is difficult, but it is not impossible."
Mumma thinks the paper by Zahnle and his coauthors has been "a disservice," so he plans to write a rebuttal. "The community needs to understand the weakness of this argument," he says.
Methane as life signature
There are new questions about the methane detected in the atmosphere of Mars. Image credit: NASA
For over 40 years, astronomers have found various hints of methane on Mars. These reports have always generated a lot of excitement because they seem to provide some clue to the habitability of our planetary neighbor.
"Methane invokes visions of life on Mars," explains Sushil Atreya of the University of Michigan. This is because much of the methane on our planet comes from living (or once-living) things.
But solid evidence of martian methane with infrared spectroscopy only surfaced eight years ago. In 2003, Mumma and his group saw signatures of methane in spectra taken with the NASA Infrared Telescope Facility in Hawaii. The methane was localized into clouds, or "plumes," over certain regions of the Martian surface, with the maximum density of methane reaching about 60 parts per billion.
In 2004, two other reports came out claiming to have seen methane. Data from the ESA’s Mars Express, which began orbiting Mars in January 2004, showed signs of methane plumes, but not in the same places as Mumma’s team. Another ground-based observation with the Canada–France–Hawaii Telescope detected methane, but it didn’t have enough spatial resolution to see plumes.
Mumma’s group performed their own follow-up observations in 2006, when the orbit of Mars again allowed methane to be detected from the ground. But in the three-year interim, all signs of the methane had disappeared, as reported in a 2009 Science paper. The implication is that the methane is a seasonal occurrence, perhaps only coinciding with summers on the red planet.
Mumma and his colleagues have estimated that the largest plumes on Mars would require a source that releases methane at rates comparable to the world’s largest hydrocarbon seep, which is in California. Although thoughts turned to little methane-belching martians, geochemical processes could potentially produce these levels of methane on Mars. The jury is still out as to which of the various candidates is the most likely source.
An illustration showing the ESA’s Mars Express mission, launched in June 2003, in orbit around the planet. Credit: ESA
The harder nut to crack may be the rapid disappearance of methane on Mars. Models of the martian atmosphere estimate that a methane molecule should survive on average about 300 years before being destroyed by photochemical processes.
However, analysis of the plume data suggests that methane is being removed from the atmosphere on the order of months, if not weeks.
Zahnle and his colleagues have looked into how hard it would be to include a methane "sink" big enough to swallow up the observed methane plumes over such a short time. They conclude that any chemical process that devours methane would completely mess up the planet’s chemical budget, in particular the allowance of oxygen.
"Methane oxidation would exhaust Mars of its atmospheric oxygen in less than 10,000 years," Zahnle says.
These concerns have found sympathetic ears in the planetary atmosphere community.
"Though the details of Zahnle et al’s theoretical arguments are debatable, their basic idea of the implausibility of large abundance and short lifetime of methane is fairly sound," Atreya says.
Mumma is aware that his observations do not mesh with the established picture of Mars. "But a measurement is a measurement," he says.
NASA’s Mars Science Laboratory Curiosity rover is shown in this artist illustration with its 2-meter-long robotic arm examining a martian rock. Curiosity is planned for launch in the fall of 2011. Credit: NASA
It’s certainly possible that Mumma and others have found a "monkey wrench" that will require revising the current models of Mars, but Zahnle and others aren’t convinced this is the case due to the difficulty in observing methane on Mars.
According to their arguments, the spacecraft measurements suffer from poor spectral resolution that makes it difficult to detect the absorption lines that identify methane in a spectrum. The ground-based observations, on the other hand, have sufficient resolution, but they must contend with the Earth’s atmosphere, which is full of its own absorption lines.
To explain this last point further, imagine looking for a pink flower with rose-tinted glasses: the light that you want to see is absorbed before it gets to you. The signatures of martian methane typically lie in the infrared regions of the spectrum where our own atmosphere is highly absorbing.
There are a few tricks that ground-based astronomers can use. For one, they can look at Mars when the planet is moving towards us or away from us. This causes a Doppler shift in the martian light that can make the methane lines a little easier to identify.
Still, observers must build models to try and subtract away the "foreground contamination" coming from our atmosphere. This involves a careful accounting of all the molecules that may be absorbing incoming light.
"The methane that [Mumma and others] see is not a raw measurement, but is rather a measurement filtered through a sophisticated but imperfect model of Earth’s atmosphere," Zahnle says.
He and his coauthors contend that these models may be incorrectly accounting for the effect of carbon-13 methane. Most methane in our atmosphere is made with carbon-12, but a small amount contains the heavier isotope carbon-13.
This schematic illustration shows major components of the microwave-oven-size instrument, which was installed into the mission’s rover, Curiosity, in January 2011. Credit: NASA
The absorption lines for terrestrial carbon-13 methane just happen to lie right where Mumma’s team claims to have detected the signature of martian methane. Zahnle’s group doesn’t think this is a coincidence. They argue that the carbon-13 methane is providing a false signal of martian methane.
Mumma disagrees. He says if they were underestimating carbon-13 methane, then this false signal should show up in all of their processed data, but it doesn’t.
"You need a very sophisticated model to extract the terrestrial signal," Mumma says " "We think our multilayer models are the most advanced in the world for this region of the spectrum."
Moreover, he says that the purported methane signal changes as they look at different regions on Mars. This kind of spatial variation wouldn’t be expected if the signal were due to absorption in our own atmosphere.
Mark Allen of the Jet Propulsion Laboratory has followed the debate and thinks Mumma has effectively rebutted the doubts about his group’s spectroscopic analysis.
Allen’s own point of view is that the methane plumes that were visible in 2003 rapidly spread out to such an extent that the gas was no longer dense enough to be detected.
"So methane doesn’t disappear, à la having to have an unusually short chemical lifetime," Allen says.
Atreya has a different take on the issue. He finds the claims of spatial and seasonal variations in the methane concentration to be "quite dubious." He believes that a relatively small quantity of methane has been observed, but the present data seem consistent with it being essentially uniformly distributed over the planet.
This artist rendering shows the ExoMars/Trace Gas Orbiter mission, which is a joint mission being developed by the European Space Agency (ESA) and NASA/JPL. Credit: ESA
"In the absence of rapid temporal and spatial variability, there would be no need to invoke exotic destruction or release mechanisms," Atreya says.
Most of the community is being cautious and not taking sides in the debate, according to Atreya. They are hoping upcoming missions will decide who was right after all.
The answer might come from NASA’s Mars Science Laboratory rover, called Curiosity. It is scheduled to land on Mars in August 2012, carrying with it the Sample Analysis at Mars (SAM) suite, which will measure a multitude of trace constituents and isotopes from gas and solid samples., Two of the SAM instruments, the tunable laser spectrometer and the quadrupole mass spectrometer, could potentially detect a whiff of methane – at the 1 part per billion level or lower – in the air around the rover landing site at Gale Crater.
A more comprehensive test is planned in 2016 with the ExoMars Trace Gas Orbiter (TGO), which will be part of the joint ESA/NASA dual mission ExoMars Program. The TGO will scan the atmosphere for exotic trace gases, such as methane.
Allen says that many people assume that the only motivation for TGO is to confirm the presence of methane, but it will perform other important science as well.
Zahnle questions whether all this effort to look for methane on Mars will be worth it in the end, "but given how the story has unfolded, it must be done."
This story has been translated into Spanish. | 0.878768 | 3.821758 |
The Aromatic World
An Interview with Pascale Ehrenfreund
After years of investigation, scientists still struggle to understand how life began on our planet. While there are many hypotheses for life’s origin, there is still no compelling evidence that suggests one scenario is more likely than any other.
In fact, when looking at chemical systems, there isn’t even a solid definition of what separates “life” from “non-life.” But many scientists do agree that life anywhere in the universe will share three essential qualities. First, life has to be able to claim an identity separate from the outside world. For early life on Earth, this likely took the form of a container, maybe a membrane sac or bag that contained chemicals.
|Many of the ingredients for life formed in outer space. The Earth formed from star dust, and later meteorites and comets delivered even more materials to our planet. But scientists are still unsure which molecules played the most important roles in life’s origin.
Image Credit: European Space Agency
Second, life eats (metabolizes). This bag of chemicals must take in energy and nutrients of some type in order to sustain itself. For humans, that can be a hamburger and fries, but for something like bacteria living at a hydrothermal vent, lunch can be hydrogen sulfide.
Finally, in order for life to go on, it must have children. Life must somehow pass on its genetic information down through time. If not, then a bag of chemicals would be a “one-off,” an anomaly in the chemical brew that lived once and then died and left no trace of its existence.
Pascale Ehrenfreund, a professor of astrophysics at the University of Leiden in the Netherlands, investigates the night skies for signs of life. Rather than a SETI-like search for radio signals, however, the signs she looks for are chemical. There are 143 kinds of molecules in the interstellar medium, and some of them may be important for life’s origin –- not just in our own solar system but also for the entire universe.
In a paper soon to be published in the journal Astrobiology, Ehrenfreund and her colleagues suggest that polycyclic aromatic hydrocarbons (PAHs), organic molecules found throughout space, may have played a fundamental role in the origin of life.
These molecules of carbon and hydrogen are called "polycyclic" because of their multiple loops of carbon atoms, and "aromatic" because of the strong chemical bonds between the carbon atoms. PAHs can be found on Earth anytime carbon-based materials are burned incompletely –- from the sooty exhaust of trucks to the black gunk that clogs barbecue grills.
In this interview with Astrobiology Magazine’s Leslie Mullen, Ehrenfreund explains how PAHs could have possibly provided the three qualities that were needed for life to arise.
|Pascale Ehrenfreund of the University of Leiden. Click image for larger view.
Photo Credit: Leslie Mullen
Astrobiology Magazine (AM): In your work, you look for chemicals in space and in meteorites, and what you find indicates the raw ingredients early life had to work with.
Pascale Ehrenfreund (PE): When you look at modern biochemistry, the three main needs of cellular systems are nucleic acids, proteins, and membranes. Some of the building blocks of these can be found in space.
Most of the prebiotic material is found in carbonaceous meteorites, but there are indications of some complex molecules in the gas phase in the interstellar medium. For instance, there are indications of simple sugars like glycoaldehyde, and also the amino acid glycine. But I’m not sure this has anything to do with the origin of life.
The interstellar medium provides the raw material for star and planet formation. There is a lot of chemistry going on in the solar nebula. The formation of the solar system was a dynamic process — material was rearranged, destroyed, disassociated, and newly formed. There are open questions about the degree of turbulence –- how much the material mixed into outer layers and then came back. In comets, we find crystalline silicates that can only have come from very close to the forming star. Yet comets form in the outer part of the solar system, so there must have been a diffusion of material -– a mixing from the inside to the outside.
AM: That was a result from the Stardust mission, wasn’t it? They discovered the comet dust had materials which could only have formed in hot regions, close to the sun.
PE: This is something we knew before Stardust — we’d previously found such indications in interplanetary dust particles. But I’m sure Stardust will improve our knowledge of that.
|Interstellar dust particle
Credit: UWSTL, NASA
In general, when you look at pre-biotic compounds like amino acids, nucleobases, and simple sugars, they have problems withstanding heat and radiation. So if this material has been formed somewhere in the gas phase, like in the interstellar medium, it would have always have to be protected from high temperature and radiation while it was incorporated into a forming solar system. It’s likely that most of the material would have been exposed to some kind of energetic processing.
When you look into meteorites, where you have solid-state chemistry involving liquid water, you find more than 80 different amino acids. You also find purines, pyrimidines, simple sugars, and nucleobases in meteorites. You do not find lipids, but you do find compounds that can form the most primitive containers -– for instance, alkane carboxylic acids, which are components of membranes. So meteorites are a kind of crystal ball for complex organic chemistry.
We don’t know if this material really was important for the origin of life. But since we know that it is extraterrestrial and it arrived intact on the early Earth, we have a sample of material that could have been important to further processing and for the build up of complexity.
But perhaps we shouldn’t give the modern biotic chemistry molecules too much credit for having been the ultimate material to form life. The temperature and radiation conditions on the early Earth improved considerably after a few hundred million years, but at the beginning it was too hostile for amino acids to assemble into proteins. You probably needed a different type of material that was much more stable.
AM: And you suggest in your new paper that polycyclic aromatic hydrocarbons –- PAHs –- could have been a stable material important for life’s origin.
|Polycyclic Aromatic Hydrocarbons.
PE: Yes. We find complex aromatic carbon rings in the interstellar medium, in comets, and in meteorites. This macromolecular material is very stable to any kind of degradation, including radiation. It may be modified, but it won’t be totally destroyed. Even if it is broken apart, the fragments are still available for future chemistry. Whereas for something like amino acids, when they are blown apart by UV photons, nothing is left.
The carbonaceous meteorites contain about 3 percent carbon, maximum. Of this 3 percent, 80 percent are incorporated into aromatic networks. So the aromatic material is abundant, it has been delivered effectively, and it is very stable — it is stable to heat, it is partly insoluble, and it is rather resistant to radiation. So now we are starting to think that under the very hostile conditions on the early Earth, such material could have been more important than we originally thought.
AM: What can PAHs lead to? Are there only specific chemical pathways, or can it be the basis for a lot of different molecules?
|The Murchison meteorite fell to Earth on September 28, 1969, near Murchison, Australia. This carbonaceous meteorite contains minerals, water, and complex organic molecules such as amino acids.
PAHs also can be photosensitizers, because they can do a charge transfer between plus and minus. So they can be used as a metabolic compound to transform energy. My co-authors Steen Rasmussen and Liaohai Chen from Los Alamos and Argonne National Laboratories are using compounds similar to polycyclic aromatic hydrocarbons as metabolic units for the Los Alamos Protocell Assembly project. The PACE project of the European community is also using PAHs in this way.
Nicholas Platts at the Carnegie Institution of Washington has proposed that by stacking PAHs, they can form something similar to a nucleic acid. Pier Luigi Luisi at RomaTre University has tried to stack PAH in the origin of life context.
So in our paper, we suggest the aromatic material can be used as a container, as a metabolic unit, and as a genetic information carrier. We think that aromatic material can be used for all three requirements for life.
What we tried to stress in our paper is that you have to meet all the requirements at once. You can’t have one compound to assemble material, and then add something else later on to do another function. They have to be combined from the beginning — life needs to have an identity, it needs energy, and it needs to be able to reproduce and evolve. That’s why PAHs are potentially so powerful, because with these aromatic compounds you can fulfill all three functions at the same time.
AM: Are PAHs currently used within any modern living systems?
|Red regions in the spiral arms represent infrared emissions from dustier parts of the galaxy where new stars are forming. Click for larger view. Credit: NASA/JPL-Caltech/S. Willner (Harvard-Smithsonian Center for Astrophysics)|
PE: Only in the form of nucleobases, which are ring structures with heteroatoms and side groups. But there are a lot of aromatic molecules — not directly PAHs — that have functions in life, particularly in metabolic processes.
AM: We’re not sure what the environment of the early Earth was like –- whether it was cold or hot. Would that make any difference?
PE: For PAHs it wouldn’t make much difference. PAHs would withstand temperature and radiation flux much better than sugars, amino acids, or other typical components of biochemistry. If you had high temperatures on the early Earth, sugars could not be formed or sustained. Amino acids are also vulnerable to heat, and so are some of the nucleobases. Nucleobases are a sort of PAH, but the nitrogen within the ring would make them more unstable than PAHs. They are certainly all much more fragile to radiation than aromatic material, as our co-author Jim Cleaves has been investigating.
The polycyclic aromatic hydrocarbons are the most abundant, free organic molecules in space. And space is certainly less comfortable than the Earth, since there is no protective atmosphere. That shows you that they can survive much better than any other material.
AM: This idea makes so much sense, because it seems more likely that life would get started from the most common, robust material at hand, rather than from extremely fragile materials that need protection or special conditions.
|Some of the ingredients for life are produced in the diamond-bright star fields of space.
PE: I think so too. Amino acids can form pretty easily -– they are everywhere — and because they are very easily formed I’m sure that later on they played an important role. But I think it would be more logical that they played a role in living systems at a time that was convenient for them. I personally do not think that kind of material was the starting material for life.
AM: Since PAHs are so robust, do you think they could be the basis for life on any planet? That a planet wouldn’t need to have Earth-like conditions in order to develop life?
PE: Yes, it is very likely. It is much more likely than having some fragile compounds that are less abundant. Also, life must start simple. And nucleosides are not simple. We still have a great deal of difficulty building them in the lab even after 50 years of prebiotic chemistry experiments! So I think we have to go to something very primitive at the beginning, and which works under a lot of different conditions. | 0.861017 | 3.817261 |
On average, only one comet per year can be seen soaring across the sky with the naked eye. If you're very lucky, you might have seen one for yourself, and this picture will look very familiar. But as much as it looks like a comet, this object baffled astronomers when it turned out to be a simple asteroid!
Asteroids are lumps of rock left over from the formation of our Solar System 4.6 billion years ago. From Earth, they look like tiny points of light moving around in the night sky. Many of them, like this one, are located between Mars and Jupiter, in a region called the Asteroid Belt. Comets, on the other hand, are mainly found in the outer edges of our Solar System.
Occasionally, a comet will wander closer towards the Sun. When this happens, it provides a fantastic show for us! Comets are made of rock, dust and ice. If they stray too close to the Sun, the heat evaporates some of the ice. This creates a fantastic “tail” that can be seen as the comet travels across the night sky.
We can see a comet-like tail in this picture. But asteroids aren't made of ice, so how did this one get its tail?
Well, the asteroid is spinning very quickly, causing its weak gravity to struggle to hold the rocky surface together, so it has started flying apart! The six comet-like tails streaming behind the asteroid are actually made of scattered dust and rock!
So far, maybe 100 to 1000 tonnes of the asteroid's material has been lost. That’s about four times the weight of the Statue of Liberty! | 0.818949 | 3.159836 |
Water in the Solar System
Oceans of Liquid Water are Unique to Planet Water
The earth appears to be unique in our solar system in that it contains an enormous amount
of water (70% of its surface), and that water has existed in a form not too different
from its present state for billions of years.
What makes the earth different from the other planets?
There are two parts to this question:
- How did the earth acquire such a large amount of water in the first place?
- Once acquired, how was it retained?
The first question has to do with how the earth was formed and the second involves the
evolution of the earth and its atmosphere. The most recent theories of planet formation describe the process of planet formation as
having two steps.
First, gravitational collapse takes place forming small asteroid like bodies some as large
as 1/500 of the mass of the earth. The planetesimals begin to collide and form the larger
bodies of the planets. The rain of bodies on the surface of the earth generates large
amounts of heat, enough to cause the heavier elements, such as iron to migrate to the centre.
A second factor has to do with the fact that when a meteor hits anything, some of it sticks
and some is scattered back into space by the impact. The lower the density of the material,
the more likely it is to escape. In the early stages, the earth collects heavier stuff more
easily, leaving lighter stuff such as silicon and water still in orbit about the sun.
As the earth gets bigger, however, it more effectively traps the lighter material during
the latter stages of planet formation.
The formation of the earth probably took a few hundred million years to be completed.
That is to be compared with the time of about 3.5 billion years since the earth has
developed a solid crust. About the time the earth was formed, the sun became large enough
that the fusion reactions in the sun ignited.
This didn't happen smoothly, but likely in sputtering way for a while.
Each flaring up of the sun sent streams of particles sweeping out.
If the earth had an atmosphere at this time, it would have been blown off leaving the earth
as a rock with neither air nor water on its surface. In fact, after the sun stabilized,
the earth went through a process of releasing gases from its interior in a process called
Over a relatively short time, something like a 100 million years, enough material had been
released to form the oceans and to give the earth an atmosphere.
There was no free oxygen in the atmosphere at this time, but it was a collection of gases,
largely ammonia, methane and carbon dioxide, held to the earth by gravitational attraction.
Fortunately, early in its history, the temperature of the earth dropped below 212 degrees
Fahrenheit, and the water condensed into the oceans we know today.
In fact, the mass of water present in the oceans, now about 10(24) grams, is about the same
as the mass of water that was contained in the crust when the degassing process started.
We can estimate the rate at which water is being lost today by estimating the rate at which
water molecules in the atmosphere are dissociated into its constituent hydrogen and oxygen.
The hydrogen is light enough that it easily moves off into space.
The net effect of hydrogen loss decreases the amount of water vapor in the atmosphere. A good estimate is that 5x10(11) grams are lost this way each year.
his amounts to a volume of a cube about 100 yards on a side.
The total water lost to space since the beginning of the earth thus amounts to about
2x10(21) grams, about 0.2 percent of the water in the oceans.
This means that most of the water you see on the earth was the very same stuff that degassed
from the crust when the earth was only a few hundred million years old.
Fortunately, the water lost to space is replaced by the same geologic processes that formed
the oceans originally.
At the present time, about 70%of the surface of the earth is covered with water.
The present coastlines are where they are because some of the water is locked up in the
polar ice caps.
In terms of volume, the water on earth is distributed in the following way:
oceans => 1.35 x10(17) cubic meters (97.3%)
polar ice and glaciers => 29x10(15) cubic meters (2.1%)
underground aquifers (fresh) => 8.4x10(15) cubic meters (0.6 %)
lakes and rivers => 0.2x10(15) cubic meters (0.01%)
atmosphere (water vapor) => 0.013x10(15) cubic meters (0.001%)
biosphere => 0.0006x10(15) cubic meters (0.00004%)
If the water locked up in polar ice were to completely melt, the oceans would rise
about 73 metres above its present level.
Why is the water still here on the earth?
This is more difficult to answer. It has to do with the changing nature of the atmosphere
due to evolution of life, specifically algae. The algae produced free oxygen by
photosynthesis which destroyed ammonia and methane, so called greenhouse gases,
just as the sun's luminosity was increasing by about twenty five percent.
If that hadn't happened the oceans would have boiled away long ago.
In fact, we are the beneficiaries of an incredible balancing act which allowed just enough
heat to escape from the earth to keep the oceans from boiling, but not so much as to cause
the earth to freeze solid.
Water on Other Planets or Moons in the Solar System?
Water in its various forms pervades the solar system, from traces of water vapour on the
Sun itself to water ice in the likely composition of Pluto and the Kuiper Belt objects
beyond it. However, large amounts of liquid water are not clearly seen elsewhere in the solar system
at the surface.
But in recent years, NASA spacecraft have found evidence that liquid water may
persist below the dry surface of Mars and the icy surfaces of three large moons circling
Water on Mars?
In the 1970s, three Mars orbiters sent back images that revealed landscape shapes apparently
formed by flowing water in the distant past. NASA's Mariner 9, Viking 1 and Viking 2
spacecraft showed us Martian channels carved as if by rivers and out-wash plains scoured
as if by floods.
Geologists estimate that very heavy flows, equal to thousands of Mississippi Rivers,
would have been necessary to shape some of the surface features on Mars.
Yet Mars' atmosphere is too thin and cold for water to remain liquid at the surface.
Instead of melting, warmed water ice on Mars turns directly into vapor, the way
carbon-dioxide "dry" ice does on Earth. To account for the signs of copious water flows in the past, scientists at first suggested
that long ago Mars had a thicker atmosphere than it does now. allowing for liquid water on
Other scientists suggested that it was liquid carbon dioxide rather than water that
have formed these features. A debris flow dominated by carbon dioxide would flow faster and farther than a water-based
flow. Also, carbon dioxide is more volatile than water at lower temperatures, and the cold
temperatures found on Mars would mean that less carbon dioxide- based magma would be
required to produce the observed erosion than magma containing mainly water.
There is now very clear evidence of erosion in many places on Mars including large floods
and small river systems. There must have been some sort of fluid on the surface. Liquid water
is the obvious fluid but other possibilities exist.
Recent Mars data suggests that large lakes or even oceans were once present on Mars.
The images of layered terrain taken by Mars Global Surveyor and the mineralology results
from MER Opportunity clearly suggest lakes of oceans. These data suggest wet episodes that
occurred only briefly and very long ago; the age of the erosion channels is estimated at
about nearly 4 billion years.
Images from Mars Express released in early 2005 show what appears to be a frozen sea that was
liquid very recently (maybe 5 million years ago). This still needs to be confirmed.
Perhaps early in its history, Mars was much more like Earth.
As with Earth almost all of its carbon dioxide was used up to form carbonate rocks. But lacking
the Earth's plate tectonics, Mars is unable to recycle any of this carbon dioxide back into its
atmosphere and so cannot sustain a significant greenhouse effect. The surface of Mars is therefore
much colder than the Earth would be at that distance from the Sun. Mars has a very thin atmosphere
composed mostly of the tiny amount of remaining carbon dioxide (95.3%) plus nitrogen (2.7%),
argon (1.6%) and traces of oxygen (0.15%) and water (0.03%). The average pressure on the surface
of Mars is only about 7 millibars (less than 1% of Earth's), but it varies greatly with altitude
from almost 9 millibars in the deepest basins to about 1 millibar at the top of Olympus Mons.
But it is thick enough to support very strong winds and vast dust storms that on occasion engulf
the entire planet for months. Mars' thin atmosphere produces a greenhouse effect but it is only
enough to raise the surface temperature by 5 degrees (K); much less than what we see on Venus and
Further evidence of water on Mars
Early telescopic observations revealed that Mars has permanent ice caps at both poles; they're
visible even with a small telescope. We now know that they're composed of water ice and solid
carbon dioxide ("dry ice"). The ice caps exhibit a layered structure with alternating layers of
ice with varying concentrations of dark dust. In the northern summer the carbon dioxide completely
sublimes, leaving a residual layer of water ice.
ESA's Mars Express has shown that a similar layer of water ice exists below the southern cap as well.
The mechanism responsible for the layering is unknown but may be due to climatic changes related to
long-term changes in the inclination of Mars' equator to the plane of its orbit. There may also be
water ice hidden below the surface at lower latitudes. The seasonal changes in the extent of the
polar caps change the global atmospheric pressure by about 25% (as measured at the Viking lander sites).
Plenty of frozen water may persists in permafrost layers underground, near the surface
at the poles, and also buried at lower latitudes. If some underground areas are warm, they might
even hold liquid water in the pores between grains of rock.
The discovery of signs of liquid water near the surface of Mars in the past and perhaps underground
suggests that Mars has the precursors for life: carbon, certain minerals, liquid water and energy.
The question remains, however, as to whether the presence of all of those ingredients - most
importantly water, under similar conditions would lead to life on Mars or any other planet. The question
whether life existed on Mars or is perhaps still there remains to be answered.
Water on Europa?
Liquid water may also be present on Europa, one of Jupiter's four major moons.
Europa is covered by a thick layer of ice. But the gravity of giant Jupiter exerts tidal
tugging that warms Europa's insides, possibly enough to keep a layer of water melted
under its frozen surface.
Water clues appeared in pictures taken by NASA's Galileo spacecraft in 1996 as it orbited
Jupiter. The pictures supported earlier theories about a hidden Europan ocean.
On some parts of Europa's surface, for example, blocks of ice appear to have broken apart
and rearranged themselves as if by floating, like Arctic ice floes, on a fluid underlayer.
Europa's fractured surface shows signs of liquid water, ice or slush.
Galileo's magnetometer instrument has sent home the strongest indication that a layer of
saltwater remains melted under Europa's crust today. As Europa moves through different
parts of Jupiter's strong magnetic field, its own weaker magnetic field changes direction,
indicating that the moon has a layer of electrically conducting material.
Since ice would not conduct electricity well enough, saltwater is the best candidate.
Similar magnetic evidence from Galileo indicates that two of Jupiter's other large moons,
Ganymede and Callisto, may have liquid saltwater layers, too.
The Moon and Comets
Earth's own Moon divulged no trace of water to NASA astronauts who explored six landing
sites more than 25 years ago. But all those sites were far from the poles.
In the 1990s, the Clementine and Lunar Prospector robotic spacecraft each found indications
that the Moon may hold supplies of water ice in permanently shaded areas near its poles.
Like the water ice on Mars, those supplies could become useful for future exploration.
Water is not only a vital resource in itself, but it can also be split into oxygen and
hydrogen for breathing and for rocket fuel for return trips or journeys beyond the Moon.
Comets may possibly be a water supply to the planets. Comets are largely ice, and they
have been colliding into the Earth, the Moon and the rest of the solar system for billions
>> Next See Water in the Universe >> | 0.903813 | 3.670922 |
Gibbous ♌ Leo
Moon phase on 25 December 2075 Wednesday is Waning Gibbous, 17 days old Moon is in Leo.Share this page: twitter facebook linkedin
Previous main lunar phase is the Full Moon before 3 days on 22 December 2075 at 08:48.
Moon rises in the evening and sets in the morning. It is visible to the southwest and it is high in the sky after midnight.
Moon is passing about ∠8° of ♌ Leo tropical zodiac sector.
Lunar disc appears visually 9.7% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1770" and ∠1951".
Next Full Moon is the Wolf Moon of January 2076 after 26 days on 21 January 2076 at 04:39.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 17 days old. Earth's natural satellite is moving from the middle to the last part of current synodic month. This is lunation 939 of Meeus index or 1892 from Brown series.
Length of current 939 lunation is 29 days, 11 hours and 11 minutes. This is the year's shortest synodic month of 2075. It is 24 minutes longer than next lunation 940 length.
Length of current synodic month is 1 hour and 33 minutes shorter than the mean length of synodic month, but it is still 4 hours and 36 minutes longer, compared to 21st century shortest.
This lunation true anomaly is ∠337.3°. At the beginning of next synodic month true anomaly will be ∠354°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
1 day after point of apogee on 24 December 2075 at 19:52 in ♋ Cancer. The lunar orbit is getting closer, while the Moon is moving inward the Earth. It will keep this direction for the next 12 days, until it get to the point of next perigee on 6 January 2076 at 18:38 in ♑ Capricorn.
Moon is 404 977 km (251 641 mi) away from Earth on this date. Moon moves closer next 12 days until perigee, when Earth-Moon distance will reach 356 990 km (221 823 mi).
2 days after its ascending node on 22 December 2075 at 18:35 in ♊ Gemini, the Moon is following the northern part of its orbit for the next 11 days, until it will cross the ecliptic from North to South in descending node on 5 January 2076 at 17:45 in ♐ Sagittarius.
2 days after beginning of current draconic month in ♊ Gemini, the Moon is moving from the beginning to the first part of it.
2 days after previous North standstill on 23 December 2075 at 08:11 in ♋ Cancer, when Moon has reached northern declination of ∠23.513°. Next 11 days the lunar orbit moves southward to face South declination of ∠-23.509° in the next southern standstill on 6 January 2076 at 04:17 in ♑ Capricorn.
After 11 days on 6 January 2076 at 10:14 in ♑ Capricorn, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.16987 |
Animation of Rosetta’s trajectory over the last two months of its mission at Comet 67P/Churyumov–Gerasimenko.
The animation begins in early August, when the spacecraft started flying elliptical orbits that brought it progressively closer to the comet at its closest approach.
On 24 September 2016, Rosetta will leave its current close, flyover orbits and transfer into the start of a 16 x 23 km orbit that will be used to prepare and line up for the final descent.
On the evening of 29 September (20:50 GMT) Rosetta will manoeuvre onto a collision course with the comet, beginning the descent from an altitude of 19 km. The spacecraft will fall freely, without further manoeuvres, collecting scientific data during the descent.
The trajectory shown here was created from real data provided over the last month, but may not necessarily follow the exact comet distance because of natural deviations from the comet’s gravity and outgassing. | 0.819127 | 3.024339 |
How to View Comet ISON
June 30, 2013
This article is the part of a series on comets contributed by Tammy Plotner. Tammy is a professional astronomy author, President Emeritus of Warren Rupp Observatory and retired Astronomical League Executive Secretary. She was the first woman astronomer to achieve Comet Hunter’s Gold Status.
What could be more fun for sky watchers everywhere than an amazing comet? For seasoned amateur astronomers and new stargazers alike, the thought of a naked eye comet sends the imagination soaring.
Right now is a great time to observe these solar system visitors, with three large comets heading our way this year. Undoubtedly, the most exciting is C/2012 S1 ISON, which is already being granted potential “Comet of the Century” status.
At the beginning of 2013, Comet ISON isn’t an easy target. Visible to both hemispheres and located in the constellation Gemini, this tiny ball of frozen gas and rock is extremely dim, only visible with a very large telescope. In the months ahead, ISON will brighten slowly within the boundaries of Gemini as the constellation moves from east to west across the night sky.
Although it is traveling fast, ISON doesn’t appear to change position. Why? Picture yourself driving on a long, flat road with the Sun behind you. Imagine ISON is another car, driving toward you. You can see the sunlight glint weakly on its windshield. While it is distant, it doesn’t seem to move. If it weren’t for that glint, you wouldn’t even know it was there. ISON is approaching from a distance as far away as Jupiter, so it appears to stay still.
As summer begins in the Northern Hemisphere, the constellation Gemini is hidden in the daylight, as is ISON—but don’t give up hope yet. Just like the car ahead in the distance, ISON is getting closer. By August, the skies will have changed again and the “Twins” will have returned to the ecliptic plane just before sunrise. By this time, Comet ISON will have brightened enough to be seen with the Cometron 114AZ telescope.
In September, ISON will finally move into the constellation of Cancer and become visible with an average backyard telescope, like the Cometron FirstScope. It may even have a slight tail or a bright nucleus! This is a critical period for astronomers; they’ll be watching ISON closely to better predict its future behavior.
Comet ISON will be pairing up visually with the planet Venus and begin moving toward the constellation Leo in October. It will appear to move greater distances with each observation, and brighten each day.
The race is on. Like the approaching car, ISON will appear to move faster even though its speed remains constant. Things will really heat up for our icy friend as it approaches the Sun: ISON will begin to sublimate, shedding layers of gas and dust—the perfect ingredients for a brilliant tail! As this material begins to flow, you’ll see the tail pointed away from the rising Sun.
By November, Comet C/2012 S1 ISON will have flown into the morning constellation Leo. While it’s not quite bright enough to be seen with the unaided eye, it should be readily visible with the Cometron 7x50 binoculars. You’ll find ISON accompanied by the nearby planets Jupiter, Mars and Venus.
Like the distant car, ISON will appear to speed up by mid-November. By this time, it isn’t just a wink on the horizon—it’s clearly a car, the sunlight is shining brightly on its windshield. Our solar system visitor will hover in the constellation Virgo. If predictions hold true, Comet ISON should be easy to spot with the naked eye from a dark sky location, just before dawn. However, the best is still yet to come because this “sungrazer” is about to blaze!
By November 25, C/2012 S1 Comet ISON could reach magnitude -0.2, a breathtaking spectacle in the morning skies. The closer it gets, the more the tail will grow and the faster it will gain magnitude. While astronomers can only predict what may happen, it is possible that Comet ISON will jump as much as nine magnitudes in a period of three days. On November 28, it might even reach an historic magnitude -0.9, making it as luminous as the Moon!
As our little “cosmic car” grazes past the Sun, it will become dimmer as it disappears in the virtual rearview mirror. Comet ISON will begin to drop rapidly in brightness as its fuel becomes exhausted. However, we’ll still be able to watch as it recedes. By Christmas, it should still be well within reach of the Cometron 10x70 binoculars and remain very visible through the end of the year.
Will Comet C/2012 S1 ISON become the “Comet of the Century”? No one knows for sure. Every comet is has its own special properties and unpredictable behavior. When it comes to comets, the best man to ask is Sungrazer Project Coordinator, Karl Battams:
“While there are still unknowns regarding this comet, there's plenty of evidence making us cautiously excited about it, and there's no reason for amateur astronomers to not share that sense of excitement! It's a little like buying a lottery ticket: you realize there's a chance you won't win, but it doesn't prevent the excitement right before the draw is made. The difference here, though, is that we genuinely have a great chance of not only winning the Comet Lottery, but winning big!”
Anyone want in on the lottery pool?
Celestron Comet Expert | 0.872357 | 3.719356 |
Before Pluto was discovered, there were 8 planets in the Solar System; and Mercury was the smallest. And then in 1930, the discovery of Pluto brought that number up to 9. For most of the 20th century, scientists weren’t sure which was bigger, Pluto or Mercury. But accurate measurements helped scientists conclude that Pluto was the smaller planet. And then in 2006, astronomers voted to remove Pluto as a planet, and so we’ve got back to 8 planets. And once again, Mercury is the smallest planet in the Solar System. But let’s compare the dwarf planet Pluto and Mercury.
In terms of size, scientists now know that Mercury is significantly larger than Pluto. The diameter of Mercury is 4,879.4 km across, while Pluto’s diameter is 2,360 km across. So Mercury is about twice as large Pluto. And just for comparison, Pluto is only 18% the diameter of Earth, while Mercury is 38% the diameter of Earth.
When it comes to density, though, Mercury and Pluto are very different. Mercury is comprised of rock and metal, while Pluto is ice and rock. The density of Mercury is 5.427 g/cm3, while the density of Pluto is about 2 g/cm3. And since Pluto is smaller and less dense than Mercury, it has a much lower force of gravity. While you would feel 38% the force of Earth gravity standing on the surface of Mercury, you would experience only 5.9% of Earth gravity on Pluto. It would be extremely difficult to walk around the surface of Pluto without flying up in the air with every step.
Mercury is the closest planet to the Sun, orbiting at an average distance of only 57.9 million km, while Pluto orbit at an average distance of 5.9 billion km. Mercury completes an orbit in just 88 days, while Pluto takes 248 years to go around the Sun just once.
Mercury has no rings or moons, while Pluto has at least 3 moons (Charon, Nix and Hydra) and might even have faint ice rings; these could be generated by meteorite impacts on the surface of Pluto kicking up material into orbit around it.
There’s one big difference between the two worlds, though. It’s possible to see Mercury with the unaided eye. If you head out before sunrise, or after sunset and look to the horizon, you can see Mercury with your own eyeballs. Pluto, on the other hand, requires a very powerful telescope; and even then it’ll only look like a faint dot.
Another difference is the fact that Mercury has been visited by spacecraft from Earth. This has given us close up images of the surface of the planet. Pluto has never been seen up close. That’s going to change soon, though, when NASA’s New Horizons spacecraft arrives at Pluto in 2015 and takes the first close up images of the dwarf planet.
We have written many stories about Mercury here on Universe Today. Here’s an article about a the discovery that Mercury’s core is liquid. And how Mercury is actually less like the Moon than previously believed. | 0.867112 | 3.491128 |
About 4 months back, in December 2019, the interstellar comet identified as 2I/Borisov produced its closest approach to our sun. Soon after its preliminary discovery by Crimean amateur astronomer Gennady Borisov in August 2019, astronomers raced to observe the object—only the next identified visitor from a further star because the asteroidlike ‘Oumuamua in 2017—before it drifted out of see. But aside from merely viewing 2I/Borisov, they were hoping for a little something else: that the heat of our sun would crack the comet apart, releasing content from its innards that was scarcely, if at all, altered after forming billions of several years back in an alien star method.
In late March those people hopes were fulfilled. Observations from two teams of astronomers applying the Hubble Area Telescope have confirmed that a massive chunk of particles up to a hundred meters in sizing has damaged off from the comet’s stable icy core, identified as the nucleus, which is alone up to five hundred meters throughout. This fragment was relocating away from the comet at about .5 meter per next and was found a lot more than one hundred eighty kilometers from its nucleus. “A smaller fragment of the primary nucleus has arrive off,” claims David Jewitt of the College of California, Los Angeles, who prospects a person of the teams. “Something arrived out.” Later photographs from Hubble revealed the fragment has because disintegrated—but the comet could perfectly continue to cast off particles.
Ever because 2I/Borisov, frequently referred to as Comet Borisov, was found out, astronomers have been eagerly finding out its mirrored light, applying a process referred to as spectroscopy to uncover its composition and look at it to a lot more familiar homegrown objects in our solar method. They have detected traces of drinking water, cyanide, oxygen, and a lot more. All those results could be but a prelude, though, to the treasure trove of knowledge from observations of Borisov as it breaks apart. “Cracking it open is even a lot more interesting, simply because what we’re actually intrigued in is what this thing’s produced of,” claims Dennis Bodewits of Auburn College, who is part of the other Hubble group. “If you crack [it] open, you get content which is hardly ever been heated just before, the making blocks of a further solar method.”
Borisov produced its closest approach to the sun on December 8, 2019, reaching about twice the Earth-sun distance. Even though the origin of the item is not identified, this function may have been the to start with time it has at any time been appreciably heated by a star, a process that will cause ices to boil off comets as gases, lending them their exclusive tail. It was not until early March, on the other hand, that Borisov showed any signals of responding to this heating when it enable out many outbursts of content.
These outbursts may have enhanced the comet’s rotation speed, resulting in the subsequent fragmentation that has now been observed. “If the nucleus spins alone up simply because of these outgassing torques, it can spin so speedy that it basically flies apart,” Jewitt claims. “We can work out the gravitational escape speed for this nucleus, and we can guess the density to be like other comets. The check of that will arrive in the future—if we at any time get to see the nucleus without dust all around it.”
As to why it took the comet until now to fragment, Michele Bannister of the College of Canterbury in New Zealand claims she was a “little stunned,” looking at the closest approach to the sun was 4 months back. She notes, on the other hand, that Borisov’s high speed, as when compared with the sun, may have played a part, swooping the item previous our star considerably speedier than indigenous comets and hence subjecting it to less overall heating. “You do have to shift your expectations a bit relative to the solar method stuff,” Bannister claims.
Hubble alone will be capable to notify us a excellent offer about this function and any subsequent exercise from Borisov. However astronomers have lamented the unfortunate timing of this hardly ever just before found breakup taking place now, when most of the world’s major observatories are shuttered simply because of the coronavirus pandemic. “The comet is now only obvious in the southern hemisphere. And all major facilities in the Southern Hemisphere—from Chile to Australia to South Africa—are closed,” claims Quanzhi Ye of the College of Maryland.
Bannister notes she and her colleagues would commonly now be measuring the composition of the interior in earnest with instruments these types of as the Quite Significant Telescope in Chile—observations that, for now, are simply not possible. “Hubble is a wonderful matter, but it has a bunch of unique instruments that are specialised to really unique needs,” she claims. “I’m not confident that [Borisov’s] going to be dazzling plenty of in some of the pieces of the spectrum [for which] we have the out there instrumentation on Hubble. What we can measure about the composition will be significantly confined.”
While Borisov will continue being obvious to Hubble for up to a further year, ground telescopes will only have a few of months just before it gets too faint to research. No matter if the pandemic’s grip on the world will have loosened by then is unclear, but for the time remaining, the grand finale of a person of our solar system’s most remarkable events is airing without a entire home. | 0.900579 | 3.939193 |
Albert Einstein ; 14 March 1879 – 18 April 1955) was a German theoretical physicist who developed the theory of general relativity, effecting a revolution in physics. For this achievement, Einstein is often regarded as the father of modern physics. While best known for his mass–energy equivalence formula E = mc (which has been dubbed "the world's most famous equation"), he received the 1921 Nobel Prize in Physics "for his services to theoretical physics, and especially for his discovery of the law of the photoelectric effect". The latter was pivotal in establishing quantum theory within physics.
Near the beginning of his career, Einstein thought that Newtonian mechanics was no longer enough to reconcile the laws of classical mechanics with the laws of the electromagnetic field. This led to the development of his special theory of relativity. He realized, however, that the principle of relativity could also be extended to gravitational fields, and with his subsequent theory of gravitation in 1916, he published a paper on the general theory of relativity. He continued to deal with problems of statistical mechanics and quantum theory, which led to his explanations of particle theory and the motion of molecules. He also investigated the thermal properties of light which laid the foundation of the photon theory of light. In 1917, Einstein applied the general theory of relativity to model the structure of the universe as a whole.
He was visiting the United States when Adolf Hitler came to power in 1933, and did not go back to Germany, where he had been a professor at the Berlin Academy of Sciences. He settled in the U.S., becoming a citizen in 1940. On the eve of World War II, he helped alert President Franklin D. Roosevelt that Germany might be developing an atomic weapon, and recommended that the U.S. begin similar research; this eventually led to what would become the Manhattan Project. Einstein was in support of defending the Allied forces, but largely denounced using the new discovery of nuclear fission as a weapon. Later, together with Bertrand Russell, Einstein signed the Russell–Einstein Manifesto, which highlighted the danger of nuclear weapons. Einstein was affiliated with the Institute for Advanced Study in Princeton, New Jersey, until his death in 1955.
Einstein published more than 300 scientific papers along with over 150 non-scientific works. His great intelligence and originality have made the word "Einstein" synonymous with genius.
Early life and education
Einstein at the age of three in 1882
Albert Einstein in 1893 (age 14)
Einstein's matriculation certificate at the age of 17, showing his final grades from the Aargau Kantonsschule (on a scale of 1-6).
Albert Einstein was born in Ulm, in the Kingdom of Württemberg in the German Empire on 14 March 1879. His father was Hermann Einstein, a salesman and engineer. His mother was Pauline Einstein (née Koch). In 1880, the family moved to Munich, where his father and his uncle founded Elektrotechnische Fabrik J. Einstein & Cie, a company that manufactured electrical equipment based on direct current.
The Einsteins were non-observant Jews. Albert attended a Catholic elementary school from the age of five for three years. Later, at the age of eight, Einstein was transferred to the Luitpold Gymnasium where he received advanced primary and secondary school education until he left Germany seven years later. Although it has been thought that Einstein had early speech difficulties, this is disputed by the Albert Einstein Archives, and he excelled at the first school that he attended.
His father once showed him a pocket compass; Einstein realized that there must be something causing the needle to move, despite the apparent "empty space". As he grew, Einstein built models and mechanical devices for fun and began to show a talent for mathematics. When Einstein was ten years old Max Talmud (later changed to Max Talmey), a poor Jewish medical student from Poland, was introduced to the Einstein family by his brother, and during weekly visits over the next five years he gave the boy popular books on science, mathematical texts and philosophical writings. These included Immanuel Kant's Critique of Pure Reason and Euclid's Elements (which Einstein called the "holy little geometry book").
In 1894, his father's company failed: direct current (DC) lost the War of Currents to alternating current (AC). In search of business, the Einstein family moved to Italy, first to Milan and then, a few months later, to Pavia. When the family moved to Pavia, Einstein stayed in Munich to finish his studies at the Luitpold Gymnasium. His father intended for him to pursue electrical engineering, but Einstein clashed with authorities and resented the school's regimen and teaching method. He later wrote that the spirit of learning and creative thought were lost in strict rote learning. At the end of December 1894 he travelled to Italy to join his family in Pavia, convincing the school to let him go by using a doctor's note. It was during his time in Italy that he wrote a short essay with the title "On the Investigation of the State of the Ether in a Magnetic Field."
In late summer 1895, at the age of sixteen, Einstein sat the entrance examinations for the Swiss Federal Polytechnic in Zurich (later the Eidgenössische Polytechnische Schule). He failed to reach the required standard in several subjects, but obtained exceptional grades in physics and mathematics. On the advice of the Principal of the Polytechnic, he attended the Aargau Cantonal School in Aarau, Switzerland, in 1895-96 to complete his secondary schooling. While lodging with the family of Professor Jost Winteler, he fell in love with Winteler's daughter, Marie. (His sister Maja later married the Wintelers' son, Paul.) In January 1896, with his father's approval, he renounced his citizenship in the German Kingdom of Württemberg to avoid military service. In September 1896 he passed the Swiss Matura with mostly good grades (gaining maximum grade 6 in physics and mathematical subjects, on a scale 1-6), and though still only seventeen he enrolled in the four year mathematics and physics teaching diploma program at the Zurich Polytechnic. Marie Winteler moved to Olsberg, Switzerland for a teaching post.
Einstein's future wife, Mileva Marić, also enrolled at the Polytechnic that same year, the only woman among the six students in the mathematics and physics section of the teaching diploma course. Over the next few years, Einstein and Marić's friendship developed into romance, and they read books together on extra-curricular physics in which Einstein was taking an increasing interest. In 1900 Einstein was awarded the Zurich Polytechnic teaching diploma, but Marić failed the examination with a poor grade in the mathematics component, theory of functions. There have been claims that Marić collaborated with Einstein on his celebrated 1905 papers, but historians of physics who have studied the issue find no evidence that she made any substantive contributions.
Marriages and children
Main article: Einstein family
In early 1902, Einstein and Mileva Marić (Милева Марић) had a daughter they named Lieserl in their correspondence, who was born in Novi Sad where Marić's parents lived. Her full name is not known, and her fate is uncertain after 1903.
Einstein and Marić married in January 1903. In May 1904, the couple's first son, Hans Albert Einstein, was born in Bern, Switzerland. Their second son, Eduard, was born in Zurich in July 1910. In 1914, Einstein moved to Berlin, while his wife remained in Zurich with their sons. Marić and Einstein divorced on 14 February 1919, having lived apart for five years.
Einstein married Elsa Löwenthal (née Einstein) on 2 June 1919, after having had a relationship with her since 1912. She was his first cousin maternally and his second cousin paternally. In 1933, they emigrated permanently to the United States. In 1935, Elsa Einstein was diagnosed with heart and kidney problems and died in December 1936.
After graduating, Einstein spent almost two frustrating years searching for a teaching post, but a former classmate's father helped him secure a job in Bern, at the Federal Office for Intellectual Property, the patent office, as an assistant examiner. He evaluated patent applications for electromagnetic devices. In 1903, Einstein's position at the Swiss Patent Office became permanent, although he was passed over for promotion until he "fully mastered machine technology".
Much of his work at the patent office related to questions about transmission of electric signals and electrical-mechanical synchronization of time, two technical problems that show up conspicuously in the thought experiments that eventually led Einstein to his radical conclusions about the nature of light and the fundamental connection between space and time.
With a few friends he met in Bern, Einstein started a small discussion group, self-mockingly named "The Olympia Academy", which met regularly to discuss science and philosophy. Their readings included the works of Henri Poincaré, Ernst Mach, and David Hume, which influenced his scientific and philosophical outlook.
Einstein's official 1921 portrait after receiving the Nobel Prize in Physics.
During 1901, the paper "Folgerungen aus den Kapillarität Erscheinungen" ("Conclusions from the Capillarity Phenomena") was published in the prestigious Annalen der Physik. On 30 April 1905, Einstein completed his thesis, with Alfred Kleiner, Professor of Experimental Physics, serving as pro-forma advisor. Einstein was awarded a PhD by the University of Zurich. His dissertation was entitled "A New Determination of Molecular Dimensions". That same year, which has been called Einstein's annus mirabilis (miracle year), he published four groundbreaking papers, on the photoelectric effect, Brownian motion, special relativity, and the equivalence of matter and energy, which were to bring him to the notice of the academic world.
By 1908, he was recognized as a leading scientist, and he was appointed lecturer at the University of Bern. The following year, he quit the patent office and the lectureship to take the position of physics docent at the University of Zurich. He became a full professor at Karl-Ferdinand University in Prague in 1911. In 1914, he returned to Germany after being appointed director of the Kaiser Wilhelm Institute for Physics (1914–1932) and a professor at the Humboldt University of Berlin, with a special clause in his contract that freed him from most teaching obligations. He became a member of the Prussian Academy of Sciences. In 1916, Einstein was appointed president of the German Physical Society (1916–1918).
During 1911, he had calculated that, based on his new theory of general relativity, light from another star would be bent by the Sun's gravity. That prediction was claimed confirmed by observations made by a British expedition led by Sir Arthur Eddington during the solar eclipse of 29 May 1919. International media reports of this made Einstein world famous. On 7 November 1919, the leading British newspaper The Times printed a banner headline that read: "Revolution in Science – New Theory of the Universe – Newtonian Ideas Overthrown". (Much later, questions were raised whether the measurements had been accurate enough to support Einstein's theory).
In 1921, Einstein was awarded the Nobel Prize in Physics for his explanation of the photoelectric effect, as relativity was considered still somewhat controversial. He also received the Copley Medal from the Royal Society in 1925.
Einstein visited New York City for the first time on 2 April 1921, where he received an official welcome by the Mayor, followed by three weeks of lectures and receptions. He went on to deliver several lectures at Columbia University and Princeton University, and in Washington he accompanied representatives of the National Academy of Science on a visit to the White House. On his return to Europe he was the guest of the British statesman and philosopher Viscount Haldane in London, where he met several renowned scientific, intellectual and political figures, and delivered a lecture at Kings College.
In 1922, he traveled throughout Asia and later to Palestine, as part of a six-month excursion and speaking tour. His travels included Singapore, Ceylon, and Japan, where he gave a series of lectures to thousands of Japanese. His first lecture in Tokyo lasted four hours, after which he met the emperor and empress at the Imperial Palace where thousands came to watch. Einstein later gave his impressions of the Japanese in a letter to his sons: "Of all the people I have met, I like the Japanese most, as they are modest, intelligent, considerate, and have a feel for art."
On his return voyage, he also visited Palestine for 12 days in what would become his only visit to that region. "He was greeted with great British pomp, as if he were a head of state rather than a theoretical physicist", writes Isaacson. This included a cannon salute upon his arrival at the residence of the British high commissioner, Sir Herbert Samuel. During one reception given to him, the building was "stormed by throngs who wanted to hear him". In Einstein's talk to the audience, he expressed his happiness over the event:
I consider this the greatest day of my life. Before, I have always found something to regret in the Jewish soul, and that is the forgetfulness of its own people. Today, I have been made happy by the sight of the Jewish people learning to recognize themselves and to make themselves recognized as a force in the world..
Love of music
Einstein developed an appreciation of music at an early age. His mother played the piano reasonably well and wanted her son to learn the violin, not only to instill in him a love of music but also to help him assimilate within German culture. According to conductor Leon Botstein, Einstein is said to have begun playing when he was five, but didn't enjoy trying to learn it at that age.
When he turned thirteen, however, he discovered the violin sonatas of Mozart. "Einstein fell in love" with Mozart's music, notes Botstein, and learned to play music more willingly. According to Einstein, he taught himself to play by "ever practicing systematically," adding that "Love is a better teacher than a sense of duty." At age seventeen, he was heard by a school examiner in Aarau as he played Beethoven's violin sonatas, the examiner stating afterward that his playing was "remarkable and revealing of 'great insight.'" What struck the examiner, writes Botstein, was that Einstein "displayed a deep love of the music, a quality that was and remains in short supply. Music possessed an unusual meaning for this student."
Botstein notes that music assumed a pivotal and permanent role in Einstein's life from that period on. Although the idea of becoming a professional was not on his mind at any time, he did play chamber music with others, and performed for private audiences and friends. Chamber music also became a regular part of his social life while living in Bern, Zurich, and Berlin, where he played with Max Planck and his son, among others. Near the end of his life, while living in Princeton, the young Juilliard Quartet visited him and he joined them playing his violin, although they slowed the tempo to accommodate his lesser abilities. However, notes Botstein, the quartet was "impressed by Einstein's level of coordination and intonation."
Cartoon of Einstein, who has shed his "Pacifism" wings, standing next to a pillar labeled "World Peace." He is rolling up his sleeves and holding a sword labeled "Preparedness" (circa 1933).
In 1933, Einstein decided to emigrate to the United States due to the rise to power of the Nazis under Germany's new chancellor, Adolf Hitler. While visiting American universities in April, 1933, he learned that the new German government had passed a law barring Jews from holding any official positions, including teaching at universities. A month later, the Nazi book burnings occurred, with Einstein's works being among those burnt, and Nazi propaganda minister Joseph Goebbels proclaimed, "Jewish intellectualism is dead." Einstein also learned that his name was on a list of assassination targets, with a "$5,000 bounty on his head." One German magazine included him in a list of enemies of the German regime with the phrase, "not yet hanged".
Einstein was undertaking his third two-month visiting professorship at the California Institute of Technology when Hitler came to power in Germany. On his return to Europe in March 1933 he resided in Belgium for some months, before temporarily moving to England.
He took up a position at the Institute for Advanced Study at Princeton, New Jersey, an affiliation that lasted until his death in 1955. He was one of the four first selected (two of the others being John von Neumann and Kurt Gödel). At the institute, he soon developed a close friendship with Gödel. The two would take long walks together discussing their work. His last assistant was Bruria Kaufman, who later became a renowned physicist. During this period, Einstein tried to develop a unified field theory and to refute the accepted interpretation of quantum physics, both unsuccessfully.
Other scientists also fled to America. Among them were Nobel laureates and professors of theoretical physics. With so many other Jewish scientists now forced by circumstances to live in America, often working side by side, Einstein wrote to a friend, "For me the most beautiful thing is to be in contact with a few fine Jews—a few millennia of a civilized past do mean something after all." In another letter he writes, "In my whole life I have never felt so Jewish as now."
World War II and the Manhattan Project
In 1939, a group of Hungarian scientists that included emigre physicist Leó Szilárd attempted to alert Washington of ongoing Nazi atomic bomb research. The group's warnings were discounted. Einstein and Szilárd, along with other refugees such as Edward Teller and Eugene Wigner, "regarded it as their responsibility to alert Americans to the possibility that German scientists might win the race to build an atomic bomb, and to warn that Hitler would be more than willing to resort to such a weapon." In the summer of 1939, a few months before the beginning of World War II in Europe, Einstein was persuaded to lend his prestige by writing a letter with Szilárd to President Franklin D. Roosevelt to alert him of the possibility. The letter also recommended that the U.S. government pay attention to and become directly involved in uranium research and associated chain reaction research.
The letter is believed to be "arguably the key stimulus for the U.S. adoption of serious investigations into nuclear weapons on the eve of the U.S. entry into World War II". President Roosevelt could not take the risk of allowing Hitler to possess atomic bombs first. As a result of Einstein's letter and his meetings with Roosevelt, the U.S. entered the "race" to develop the bomb, drawing on its "immense material, financial, and scientific resources" to initiate the Manhattan Project. It became the only country to successfully develop an atomic bomb during World War II.
For Einstein, "war was a disease . . . [and] he called for resistance to war." But in 1933, after Hitler assumed full power in Germany, "he renounced pacifism altogether . . . In fact, he urged the Western powers to prepare themselves against another German onslaught." In 1954, a year before his death, Einstein said to his old friend, Linus Pauling, "I made one great mistake in my life — when I signed the letter to President Roosevelt recommending that atom bombs be made; but there was some justification — the danger that the Germans would make them..."
Einstein became an American citizen in 1940. Not long after settling into his career at Princeton, he expressed his appreciation of the "meritocracy" in American culture when compared to Europe. According to Isaacson, he recognized the "right of individuals to say and think what they pleased", without social barriers, and as result, the individual was "encouraged" to be more creative, a trait he valued from his own early education. Einstein writes:
What makes the new arrival devoted to this country is the democratic trait among the people. No one humbles himself before another person or class. . . American youth has the good fortune not to have its outlook troubled by outworn traditions.
As a member of the National Association for the Advancement of Colored People (NAACP) at Princeton who campaigned for the civil rights of African Americans, Einstein corresponded with civil rights activist W. E. B. Du Bois, and in 1946 Einstein called racism America's "worst disease". He later stated, "Race prejudice has unfortunately become an American tradition which is uncritically handed down from one generation to the next. The only remedies are enlightenment and education".
After the death of Israel's first president, Chaim Weizmann, in November 1952, Prime Minister David Ben-Gurion offered Einstein the position of President of Israel, a mostly ceremonial post. The offer was presented by Israel's ambassador in Washington, Abba Eban, who explained that the offer "embodies the deepest respect which the Jewish people can repose in any of its sons". However, Einstein declined, and wrote in his response that he was "deeply moved", and "at once saddened and ashamed" that he could not accept it:
All my life I have dealt with objective matters, hence I lack both the natural aptitude and the experience to deal properly with people and to exercise official function. I am the more distressed over these circumstances because my relationship with the Jewish people became my strongest human tie once I achieved complete clarity about our precarious position among the nations of the world.
The New York World-Telegram announces Einstein's death on 18 April 1955.
On 17 April 1955, Albert Einstein experienced internal bleeding caused by the rupture of an abdominal aortic aneurysm, which had previously been reinforced surgically by Dr. Rudolph Nissen in 1948. He took the draft of a speech he was preparing for a television appearance commemorating the State of Israel's seventh anniversary with him to the hospital, but he did not live long enough to complete it. Einstein refused surgery, saying: "I want to go when I want. It is tasteless to prolong life artificially. I have done my share, it is time to go. I will do it elegantly." He died in Princeton Hospital early the next morning at the age of 76, having continued to work until near the end.
During the autopsy, the pathologist of Princeton Hospital, Thomas Stoltz Harvey, removed Einstein's brain for preservation without the permission of his family, in the hope that the neuroscience of the future would be able to discover what made Einstein so intelligent. Einstein's remains were cremated and his ashes were scattered at an undisclosed location.
In his lecture at Einstein's memorial, nuclear physicist Robert Oppenheimer summarized his impression of him as a person: "He was almost wholly without sophistication and wholly without worldliness . . . There was always with him a wonderful purity at once childlike and profoundly stubborn."
The photoelectric effect. Incoming photons on the left strike a metal plate (bottom), and eject electrons, depicted as flying off to the right.
Throughout his life, Einstein published hundreds of books and articles. In addition to the work he did by himself he also collaborated with other scientists on additional projects including the Bose–Einstein statistics, the Einstein refrigerator and others.
1905 - Annus Mirabilis papers
Main articles: Annus Mirabilis papers, Photoelectric effect, Special theory of relativity, and Mass–energy equivalence
The Annus Mirabilis papers are four articles pertaining to the photoelectric effect (which gave rise to quantum theory), Brownian motion, the special theory of relativity, and E = mc that Albert Einstein published in the Annalen der Physik scientific journal in 1905. These four works contributed substantially to the foundation of modern physics and changed views on space, time, and matter. The four papers are:
Title (translated) Area of focus Received Published Significance
On a Heuristic Viewpoint Concerning the Production and Transformation of Light Photoelectric effect 18 March 9 June Resolved an unsolved puzzle by suggesting that energy is exchanged only in discrete amounts (quanta). This idea was pivotal to the early development of quantum theory.
On the Motion of Small Particles Suspended in a Stationary Liquid, as Required by the Molecular Kinetic Theory of Heat Brownian motion 11 May 18 July Explained empirical evidence for the atomic theory, supporting the application of statistical physics.
On the Electrodynamics of Moving Bodies Special relativity 30 June 26 Sept Reconciled Maxwell's equations for electricity and magnetism with the laws of mechanics by introducing major changes to mechanics close to the speed of light, resulting from analysis based on empirical evidence that the speed of light is independent of the motion of the observer. Discredited the concept of an "luminiferous ether."
Does the Inertia of a Body Depend Upon Its Energy Content? Matter–energy equivalence 27 Sept 21 Nov Equivalence of matter and energy, E = mc (and by implication, the ability of gravity to "bend" light), the existence of "rest energy", and the basis of nuclear energy.
Thermodynamic fluctuations and statistical physics
Main articles: Statistical mechanics, thermal fluctuations, and statistical physics
Albert Einstein's first paper submitted in 1900 to Annalen der Physik was on capillary attraction. It was published in 1901 with the title "Folgerungen aus den Kapillarität Erscheinungen," which translates as "Conclusions from the capillarity phenomena". Two papers he published in 1902–1903 (thermodynamics) attempted to interpret atomic phenomena from a statistical point of view. These papers were the foundation for the 1905 paper on Brownian motion, which showed that Brownian movement can be construed as firm evidence that molecules exist. His research in 1903 and 1904 was mainly concerned with the effect of finite atomic size on diffusion phenomena.
He articulated the principle of relativity. This was understood by Hermann Minkowski to be a generalization of rotational invariance from space to space-time. Other principles postulated by Einstein and later vindicated are the principle of equivalence and the principle of adiabatic invariance of the quantum number.
Theory of relativity and
Main article: History of special relativity
Einstein's "Zur Elektrodynamik bewegter Körper" ("On the Electrodynamics of Moving Bodies") was received on 30 June 1905 and published 26 September of that same year. It reconciles Maxwell's equations for electricity and magnetism with the laws of mechanics, by introducing major changes to mechanics close to the speed of light. This later became known as Einstein's special theory of relativity.
Consequences of this include the time-space frame of a moving body appearing to slow down and contract (in the direction of motion) when measured in the frame of the observer. This paper also argued that the idea of a luminiferous aether – one of the leading theoretical entities in physics at the time – was superfluous.
In his paper on mass–energy equivalence Einstein produced E = mc from his special relativity equations. Einstein's 1905 work on relativity remained controversial for many years, but was accepted by leading physicists, starting with Max Planck.
Photons and energy quanta
Main articles: Photon and Quantum
In a 1905 paper, Einstein postulated that light itself consists of localized particles (quanta). Einstein's light quanta were nearly universally rejected by all physicists, including Max Planck and Niels Bohr. This idea only became universally accepted in 1919, with Robert Millikan's detailed experiments on the photoelectric effect, and with the measurement of Compton scattering.
Einstein concluded that each wave of frequency f is associated with a collection of photons with energy hf each, where h is Planck's constant. He does not say much more, because he is not sure how the particles are related to the wave. But he does suggest that this idea would explain certain experimental results, notably the photoelectric effect.
Quantized atomic vibrations
Main article: Einstein solid
In 1907 Einstein proposed a model of matter where each atom in a lattice structure is an independent harmonic oscillator. In the Einstein model, each atom oscillates independently – a series of equally spaced quantized states for each oscillator. Einstein was aware that getting the frequency of the actual oscillations would be different, but he nevertheless proposed this theory because it was a particularly clear demonstration that quantum mechanics could solve the specific heat problem in classical mechanics. Peter Debye refined this model.
Adiabatic principle and action-angle variables
Main article: Old quantum theory
Throughout the 1910s, quantum mechanics expanded in scope to cover many different systems. After Ernest Rutherford discovered the nucleus and proposed that electrons orbit like planets, Niels Bohr was able to show that the same quantum mechanical postulates introduced by Planck and developed by Einstein would explain the discrete motion of electrons in atoms, and the periodic table of the elements.
Einstein contributed to these developments by linking them with the 1898 arguments Wilhelm Wien had made. Wien had shown that the hypothesis of adiabatic invariance of a thermal equilibrium state allows all the blackbody curves at different temperature to be derived from one another by a simple shifting process. Einstein noted in 1911 that the same adiabatic principle shows that the quantity which is quantized in any mechanical motion must be an adiabatic invariant. Arnold Sommerfeld identified this adiabatic invariant as the action variable of classical mechanics. The law that the action variable is quantized was a basic principle of the quantum theory as it was known between 1900 and 1925.
Einstein at the Solvay Conference in 1911
Main article: Wave–particle duality
Although the patent office promoted Einstein to Technical Examiner Second Class in 1906, he had not given up on academia. In 1908, he became a privatdozent at the University of Bern. In "über die Entwicklung unserer Anschauungen über das Wesen und die Konstitution der Strahlung" ("The Development of Our Views on the Composition and Essence of Radiation"), on the quantization of light, and in an earlier 1909 paper, Einstein showed that Max Planck's energy quanta must have well-defined momenta and act in some respects as independent, point-like particles. This paper introduced the photon concept (although the name photon was introduced later by Gilbert N. Lewis in 1926) and inspired the notion of wave–particle duality in quantum mechanics.
Theory of critical opalescence
Main article: Critical opalescence
Einstein returned to the problem of thermodynamic fluctuations, giving a treatment of the density variations in a fluid at its critical point. Ordinarily the density fluctuations are controlled by the second derivative of the free energy with respect to the density. At the critical point, this derivative is zero, leading to large fluctuations. The effect of density fluctuations is that light of all wavelengths is scattered, making the fluid look milky white. Einstein relates this to Raleigh scattering, which is what happens when the fluctuation size is much smaller than the wavelength, and which explains why the sky is blue. Einstein quantitatively derived critical opalescence from a treatment of density fluctuations, and demonstrated how both the effect and Rayleigh scattering originate from the atomistic constitution of matter.
Main article: Zero-point energy
Einstein's physical intuition led him to note that Planck's oscillator energies had an incorrect zero point. He modified Planck's hypothesis by stating that the lowest energy state of an oscillator is equal to ⁄2hf, to half the energy spacing between levels. This argument, which was made in 1913 in collaboration with Otto Stern, was based on the thermodynamics of a diatomic molecule which can split apart into two free atoms.
General relativity and the Equivalence Principle
Main article: History of general relativity
See also: Principle of equivalence, Theory of relativity, and Einstein field equations
Eddington’s photograph of a solar eclipse.
General relativity (GR) is a theory of gravitation that was developed by Albert Einstein between 1907 and 1915. According to general relativity, the observed gravitational attraction between masses results from the warping of space and time by those masses. General relativity has developed into an essential tool in modern astrophysics. It provides the foundation for the current understanding of black holes, regions of space where gravitational attraction is so strong that not even light can escape.
As Albert Einstein later said, the reason for the development of general relativity was that the preference of inertial motions within special relativity was unsatisfactory, while a theory which from the outset prefers no state of motion (even accelerated ones) should appear more satisfactory. So in 1908 he published an article on acceleration under special relativity. In that article, he argued that free fall is really inertial motion, and that for a freefalling observer the rules of special relativity must apply. This argument is called the Equivalence principle. In the same article, Einstein also predicted the phenomenon of gravitational time dilation. In 1911, Einstein published another article expanding on the 1907 article, in which additional effects such as the deflection of light by massive bodies were predicted.
Hole argument and Entwurf theory
Main article: Hole argument
While developing general relativity, Einstein became confused about the gauge invariance in the theory. He formulated an argument that led him to conclude that a general relativistic field theory is impossible. He gave up looking for fully generally covariant tensor equations, and searched for equations that would be invariant under general linear transformations only.
In June, 1913 the Entwurf ("draft") theory was the result of these investigations. As its name suggests, it was a sketch of a theory, with the equations of motion supplemented by additional gauge fixing conditions. Simultaneously less elegant and more difficult than general relativity, after more than two years of intensive work Einstein abandoned the theory in November, 1915 after realizing that the hole argument was mistaken.
Main article: Cosmology
In 1917, Einstein applied the General theory of relativity to model the structure of the universe as a whole. He wanted the universe to be eternal and unchanging, but this type of universe is not consistent with relativity. To fix this, Einstein modified the general theory by introducing a new notion, the cosmological constant. With a positive cosmological constant, the universe could be an eternal static sphere.
Einstein in his office at the University of Berlin.
Einstein believed a spherical static universe is philosophically preferred, because it would obey Mach's principle. He had shown that general relativity incorporates Mach's principle to a certain extent in frame dragging by gravitomagnetic fields, but he knew that Mach's idea would not work if space goes on forever. In a closed universe, he believed that Mach's principle would hold. Mach's principle has generated much controversy over the years.
Modern quantum theory
Main article: Schrödinger equation
Einstein was displeased with quantum theory and mechanics, despite its acceptance by other physicists, stating "God doesn't play with dice." As Einstein passed away at the age of 76 he still would not accept quantum theory. In 1917, at the height of his work on relativity, Einstein published an article in Physikalische Zeitschrift that proposed the possibility of stimulated emission, the physical process that makes possible the maser and the laser. This article showed that the statistics of absorption and emission of light would only be consistent with Planck's distribution law if the emission of light into a mode with n photons would be enhanced statistically compared to the emission of light into an empty mode. This paper was enormously influential in the later development of quantum mechanics, because it was the first paper to show that the statistics of atomic transitions had simple laws. Einstein discovered Louis de Broglie's work, and supported his ideas, which were received skeptically at first. In another major paper from this era, Einstein gave a wave equation for de Broglie waves, which Einstein suggested was the Hamilton–Jacobi equation of mechanics. This paper would inspire Schrödinger's work of 1926.
Main article: Bose–Einstein condensation
In 1924, Einstein received a description of a statistical model from Indian physicist Satyendra Nath Bose, based on a counting method that assumed that light could be understood as a gas of indistinguishable particles. Einstein noted that Bose's statistics applied to some atoms as well as to the proposed light particles, and submitted his translation of Bose's paper to the Zeitschrift für Physik. Einstein also published his own articles describing the model and its implications, among them the Bose–Einstein condensate phenomenon that some particulates should appear at very low temperatures. It was not until 1995 that the first such condensate was produced experimentally by Eric Allin Cornell and Carl Wieman using ultra-cooling equipment built at the NIST–JILA laboratory at the University of Colorado at Boulder.Bose–Einstein statistics are now used to describe the behaviors of any assembly of bosons. Einstein's sketches for this project may be seen in the Einstein Archive in the library of the Leiden University.
Energy momentum pseudotensor
Main article: Stress-energy-momentum pseudotensor
General relativity includes a dynamical spacetime, so it is difficult to see how to identify the conserved energy and momentum. Noether's theorem allows these quantities to be determined from a Lagrangian with translation invariance, but general covariance makes translation invariance into something of a gauge symmetry. The energy and momentum derived within general relativity by Noether's presecriptions do not make a real tensor for this reason.
Einstein argued that this is true for fundamental reasons, because the gravitational field could be made to vanish by a choice of coordinates. He maintained that the non-covariant energy momentum pseudotensor was in fact the best description of the energy momentum distribution in a gravitational field. This approach has been echoed by Lev Landau and Evgeny Lifshitz, and others, and has become standard.
The use of non-covariant objects like pseudotensors was heavily criticized in 1917 by Erwin Schrödinger and others.
Unified field theory
Main article: Classical unified field theories
Following his research on general relativity, Einstein entered into a series of attempts to generalize his geometric theory of gravitation to include electromagnetism as another aspect of a single entity. In 1950, he described his "unified field theory" in a Scientific American article entitled "On the Generalized Theory of Gravitation". Although he continued to be lauded for his work, Einstein became increasingly isolated in his research, and his efforts were ultimately unsuccessful. In his pursuit of a unification of the fundamental forces, Einstein ignored some mainstream developments in physics, most notably the strong and weak nuclear forces, which were not well understood until many years after his death. Mainstream physics, in turn, largely ignored Einstein's approaches to unification. Einstein's dream of unifying other laws of physics with gravity motivates modern quests for a theory of everything and in particular string theory, where geometrical fields emerge in a unified quantum-mechanical setting.
Main article: Wormhole
Einstein collaborated with others to produce a model of a wormhole. His motivation was to model elementary particles with charge as a solution of gravitational field equations, in line with the program outlined in the paper "Do Gravitational Fields play an Important Role in the Constitution of the Elementary Particles?". These solutions cut and pasted Schwarzschild black holes to make a bridge between two patches.
If one end of a wormhole was positively charged, the other end would be negatively charged. These properties led Einstein to believe that pairs of particles and antiparticles could be described in this way.
Main article: Einstein–Cartan theory
In order to incorporate spinning point particles into general relativity, the affine connection needed to be generalized to include an antisymmetric part, called the torsion. This modification was made by Einstein and Cartan in the 1920s.
Equations of motion
Main article: Einstein–Infeld–Hoffmann equations
The theory of general relativity has a fundamental law – the Einstein equations which describe how space curves, the geodesic equation which describes how particles move may be derived from the Einstein equations.
Since the equations of general relativity are non-linear, a lump of energy made out of pure gravitational fields, like a black hole, would move on a trajectory which is determined by the Einstein equations themselves, not by a new law. So Einstein proposed that the path of a singular solution, like a black hole, would be determined to be a geodesic from general relativity itself.
This was established by Einstein, Infeld, and Hoffmann for pointlike objects without angular momentum, and by Roy Kerr for spinning objects.
Main article: Einstein's unsuccessful investigations
Einstein conducted other investigations that were unsuccessful and abandoned. These pertain to force, superconductivity, gravitational waves, and other research. Please see the main article for details.
Collaboration with other scientists
The 1927 Solvay Conference in Brussels, a gathering of the world's top physicists. Einstein in the center.
In addition to long time collaborators Leopold Infeld, Nathan Rosen, Peter Bergmann and others, Einstein also had some one-shot collaborations with various scientists.
Einstein–de Haas experiment
Main article: Einstein–de Haas effect
Einstein and De Haas demonstrated that magnetization is due to the motion of electrons, nowadays known to be the spin. In order to show this, they reversed the magnetization in an iron bar suspended on a torsion pendulum. They confirmed that this leads the bar to rotate, because the electron's angular momentum changes as the magnetization changes. This experiment needed to be sensitive, because the angular momentum associated with electrons is small, but it definitively established that electron motion of some kind is responsible for magnetization.
Schrödinger gas model
Einstein suggested to Erwin Schrödinger that he might be able to reproduce the statistics of a Bose–Einstein gas by considering a box. Then to each possible quantum motion of a particle in a box associate an independent harmonic oscillator. Quantizing these oscillators, each level will have an integer occupation number, which will be the number of particles in it.
This formulation is a form of second quantization, but it predates modern quantum mechanics. Erwin Schrödinger applied this to derive the thermodynamic properties of a semiclassical ideal gas. Schrödinger urged Einstein to add his name as co-author, although Einstein declined the invitation.
Main article: Einstein refrigerator
In 1926, Einstein and his former student Leó Szilárd co-invented (and in 1930, patented) the Einstein refrigerator. This absorption refrigerator was then revolutionary for having no moving parts and using only heat as an input. On 11 November 1930, U.S. Patent 1,781,541 was awarded to Albert Einstein and Leó Szilárd for the refrigerator. Their invention was not immediately put into commercial production, as the most promising of their patents were quickly bought up by the Swedish company Electrolux to protect its refrigeration technology from competition.
Bohr versus Einstein
Main article: Bohr–Einstein debates
Einstein and Niels Bohr, 1925
The Bohr–Einstein debates were a series of public disputes about quantum mechanics between Albert Einstein and Niels Bohr who were two of its founders. Their debates are remembered because of their importance to the philosophy of science.
Main article: EPR paradox
In 1935, Einstein returned to the question of quantum mechanics. He considered how a measurement on one of two entangled particles would affect the other. He noted, along with his collaborators, that by performing different measurements on the distant particle, either of position or momentum, different properties of the entangled partner could be discovered without disturbing it in any way.
He then used a hypothesis of local realism to conclude that the other particle had these properties already determined. The principle he proposed is that if it is possible to determine what the answer to a position or momentum measurement would be, without in any way disturbing the particle, then the particle actually has values of position or momentum.
This principle distilled the essence of Einstein's objection to quantum mechanics. As a physical principle, it was shown to be incorrect when the Aspect experiment of 1982 confirmed Bell's theorem, which had been promulgated in 1964.
Political and religious views
Main articles: Albert Einstein's political views and Albert Einstein's religious views
Albert Einstein, seen here with his wife Elsa Einstein and Zionist leaders, including future President of Israel Chaim Weizmann, his wife Dr. Vera Weizmann, Menahem Ussishkin, and Ben-Zion Mossinson on arrival in New York City in 1921.
Albert Einstein's political views emerged publicly in the middle of the 20th century due to his fame and reputation for genius. Einstein offered to and was called on to give judgments and opinions on matters often unrelated to theoretical physics or mathematics (see main article).
Einstein's views about religious belief have been collected from interviews and original writings. These views covered Judaism, theological determinism, agnosticism, and humanism. He also wrote much about ethical culture, opting for Spinoza's god over belief in a personal god.
While travelling, Einstein wrote daily to his wife Elsa and adopted stepdaughters Margot and Ilse. The letters were included in the papers bequeathed to The Hebrew University. Margot Einstein permitted the personal letters to be made available to the public, but requested that it not be done until twenty years after her death (she died in 1986). Barbara Wolff, of The Hebrew University's Albert Einstein Archives, told the BBC that there are about 3,500 pages of private correspondence written between 1912 and 1955.
Einstein bequeathed the royalties from use of his image to The Hebrew University of Jerusalem. Corbis, successor to The Roger Richman Agency, licenses the use of his name and associated imagery, as agent for the university.
In popular culture
Main article: Albert Einstein in popular culture
In the period before World War II, Einstein was so well known in America that he would be stopped on the street by people wanting him to explain "that theory". He finally figured out a way to handle the incessant inquiries. He told his inquirers "Pardon me, sorry! Always I am mistaken for Professor Einstein."
Einstein has been the subject of or inspiration for many novels, films, plays, and works of music. He is a favorite model for depictions of mad scientists and absent-minded professors; his expressive face and distinctive hairstyle have been widely copied and exaggerated. Time magazine's Frederic Golden wrote that Einstein was "a cartoonist's dream come true".
Awards and honors
Main article: Einstein's awards and honors
Einstein received numerous awards and honors, including the Nobel Prize in Physics. | 0.824121 | 3.33393 |
Last night, at 0:36 GMT, contact with Philae was lost, as the lander’s non-rechargeable battery drained and it entered hibernation. Considering the very low amount of sunlight available in the location it eventually ended up in at the end of the two jumps it made after first touching down on the surface, the odds of the solar panels producing enough energy to exit this state in the near future are just about zero, despite the fact that the lift and turn operation succeeded, lifting Philae by about four centimeters and rotating it about 35 degrees in order to place the larger solar panel in the one area that does receive at least some sunlight. Still, there is hope for later, as it is believed the lander will be able to withstand the low temperatures it’s currently facing and the power situation will obviously improve as the comet approaches perihelion.
Something that seemed strange to me is the timeline, however, as it was initially stated that the conditions will become too hot for Philae to continue operating in March, yet during yesterday’s Hangout it was said that the power situation should improve enough when the comet will be at less than 1 AU from the Sun, and they mentioned late summer, perhaps August or as late as September. Admittedly, being in the shade and receiving about one and a half hours of sunlight on one side and about 20 minutes on a couple of others per comet “day”, which lasts about 12.4 hours, instead of the planned six to seven hours, does definitely mean that it won’t get nearly as hot, but that’s quite a difference.
Either way, they said the one solar panel that receives some sunlight for about one and a half hours per comet day produced less than one watt and the peak, for the 20 or so minutes when a couple of others come partially out of the shade as well, was three to four watts. That may have increased slightly now that they moved the larger solar panel in the better position, but when they also said Philae requires 5.1 watts to boot up and, at the moment, 50 to 60 to heat the battery to the 0°C required to start charging, it’s clear it’ll be a long time before anything may happen, and even longer before enough power will build up to support other instruments as well and do some more science.
Now we could dwell on what went wrong, starting with the failure of the thruster and harpoons which should have made Philae stay where it first landed, continuing with the fact that some of the operations which should have been performed on the surface of the comet were actually performed some distance above it, as the instruments started gathering information as soon as the lander first touched down, and ending with this particularly unfortunate position Philae eventually stopped in, which prevents it from continuing to operate at the moment. However, an incredible number of things went well, and this is what allowed this insanely daring attempt to be a success, because this is precisely what it was.
More than 20 years since this mission started being planned and ten years after launch, a man-made spacecraft caught up to a comet, entered orbit around it and delivered on its surface a lander which managed to complete its primary mission and transmit the science data obtained before it entered hibernation. This was an unbelievably difficult endeavor and so much could go so wrong that the idea of it succeeding on the first attempt as much as it did was likely difficult to believe for many who had some grasp of what was involved.
So now we move on and see what comes next, as Rosetta will continue orbiting the comet throughout next year, gathering as much information as possible before, according to some recent statements, eventually finding its final resting place on the surface as well. And if, at any point during that time, Philae will wake up as well, things can only get better, and if its current sheltered position will help it survive the period of closest approach to the Sun and the comet’s activity won’t otherwise damage it too badly, there’s even a chance it may somehow hop away from that spot and find one where it’ll receive more sunlight on the way back, allowing for far more observations than initially hoped for.
I’m going to end this by simply saying congratulations to ESA and to everyone else involved, and let’s hope space exploration will continue to offer us as a species reasons to celebrate. Once again, I must point out that, considering how little attention and funding governments seem willing to spare for such efforts, this seems quite unlikely right now, and considering the amount of time that passes between the moment any such endeavor starts being planned and the final, visible triumph, the results of this current attitude will hurt us all for decades to come, but as long as we’ll still have groups of passionate, dedicated and absolutely brilliant people, miracles may still happen. And this obviously applies to any field one may think of. | 0.853866 | 3.080604 |
This ultra-high definition (3840x2160) video shows the sun in the 171 angstrom wavelength of extreme ultraviolet light. It covers a time period of January 2, 2015 to January 28, 2016 at a cadence of one frame every hour, or 24 frames per day. This timelapse is repeated with narration by solar scientist Nicholeen Viall and contains close-ups and annotations. 171 angstrom light highlights material around 600,000 Kelvin and shows features in the upper transition region and quiet corona of the sun. The video is available to download here at 59.94 frames per second, double the rate YouTube currently allows for UHD content. The music is titled "Tides" and is from Killer Tracks.
The sun is always changing and NASA's Solar Dynamics Observatory is always watching. Launched on Feb. 11, 2010, SDO keeps a 24-hour eye on the entire disk of the sun, with a prime view of the graceful dance of solar material coursing through the sun's atmosphere, the corona. SDO's sixth year in orbit was no exception. This video shows that entire sixth year--from Jan. 1, 2015 to Jan. 28, 2016 as one time-lapse sequence. At full quality, this video is ultra-high definition 3840x2160 and 59.94 frames per second. Each frame represents 1 hour.
SDO's Atmospheric Imaging Assembly (AIA) captures a shot of the sun every 12 seconds in 10 different wavelengths. The images shown here are based on a wavelength of 171 angstroms, which is in the extreme ultraviolet range and shows solar material at around 600,000 Kelvin (about 1 million degrees F.) In this wavelength it is easy to see the sun's 25-day rotation.
During the course of the video, the sun subtly increases and decreases in apparent size. This is because the distance between the SDO spacecraft and the sun varies over time. The image is, however, remarkably consistent and stable despite the fact that SDO orbits Earth at 6,876 mph and the Earth orbits the sun at 67,062 miles per hour.
Scientists study these images to better understand the complex electromagnetic system causing the constant movement on the sun, which can ultimately have an effect closer to Earth, too: Flares and another type of solar explosion called coronal mass ejections can sometimes disrupt technology in space. Moreover, studying our closest star is one way of learning about other stars in the galaxy. NASA's Goddard Space Flight Center in Greenbelt, Maryland. built, operates, and manages the SDO spacecraft for NASA's Science Mission Directorate in Washington, D.C.
This image, and the one at the top, is a composite of 23 separate images spanning the period of January 11, 2015 to January 21, 2016. It uses the SDO AIA wavelength of 171 angstroms and reveals the zones on the sun where active regions are most common during this part of the solar cycle. There are wallpapers sized for some phones and tablets available to download here.
Credit: NASA's Goddard Space Flight Center/SDO/S. Wiessinger
This ultra-high definition (3840x2160) video shows the sun in the 171 angstrom wavelength of extreme ultraviolet light. It covers a time period of January 2, 2015 to January 28, 2016 at a cadence of one frame every hour, or 24 frames per day. The video is available to download here at 59.94 frames per second, double the rate YouTube currently allows for UHD content.
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 220.127.116.11.0 | 0.845103 | 3.680719 |
NASA selects Psyche and Lucy as Discovery missions
The Psyche mission, a journey to a metal asteroid, has been selected for flight under NASA’s Discovery Program, a series of lower-cost, highly focused robotic space missions that are exploring the solar system. Psyche includes prominent roles for Department of Earth, Atmospheric and Planetary Sciences (EAPS) professors Maria Zuber (leading the Gravity investigation), Richard Binzel (asteroid composition expert), and Benjamin Weiss (leading the Magnetometer investigation).
The mission principal investigator is former EAPS professor Lindy Elkins-Tanton ’87, SM ’87, PhD ’02, now director of Arizona State University’s School of Earth and Space Exploration (SESE). The mission’s spacecraft is expected to launch in 2023, arriving at the asteroid in 2030, where it will spend 20 months in orbit, mapping it and studying its properties.
“This mission, visiting the asteroid Psyche, will be the first time humans will ever be able to see a planetary core,” says Elkins-Tanton. “Having the Psyche mission selected for NASA’s Discovery Program will help us gain insights into the metal interior of all rocky planets in our solar system, including Earth.”
Psyche, an asteroid orbiting the sun between Mars and Jupiter, is made almost entirely of nickel-iron metal. As such, it offers a unique look into the violent collisions that created Earth and the other terrestrial planets.
The scientific goals of the Psyche mission are to understand the building blocks of planet formation and explore firsthand a wholly new and unexplored type of world. The mission team seeks to determine whether Psyche is a protoplanetary core, how old it is, whether it formed in similar ways to the Earth’s core, and what its surface is like.
"This is an opportunity to explore a new type of world — not one of rock or ice, but of metal," says Elkins-Tanton. "[The asteroid] 16 Psyche is the only known object of its kind in the solar system, and this is the only way humans will ever visit a core. We learn about inner space by visiting outer space."
Every world explored so far by humans (except gas giant planets such as Jupiter or Saturn) has a surface of ice or rock or a mixture of the two, but their cores are thought to be metallic. These cores, however, lie far below rocky mantles and crusts and are considered unreachable in our lifetimes.
Psyche, an asteroid that appears to be the exposed nickel-iron core of a protoplanet, one of the building blocks of the sun’s planetary system, may provide a window into those cores. The asteroid is most likely a survivor of violent space collisions, common when the solar system was forming.
Psyche follows an orbit in the outer part of the main asteroid belt, at an average distance from the sun of about 280 million miles, or three times farther from the sun than Earth. It is roughly the size of Massachusetts (about 130 miles in diameter) and dense (7,000 kilograms per cubic meter).
“Psyche's metallic nature has been tantalising asteroid scientists for decades. It's a dream destination for new discoveries,” says Binzel. The spacecraft's instrument payload will include a magnetometer, multispectral imager, a gamma ray and neutron spectrometer, and a radio-science experiment.
The magnetometer experiment, led by MIT’s Benjamin Weiss and to be built by UCLA, is designed to detect and measure the remnant magnetic field of the asteroid. It’s composed of two identical high-sensitivity magnetic field sensors located at the middle and outer end of the boom.
According to Weiss, “the goal of the magnetometer is to establish whether Psyche once generated a magnetic field, which would confirm that Psyche is the metallic core of a shattered protoplanet and teach us about how small bodies like asteroids and moons generate magnetism.”
The multispectral imager, which will be led by an ASU science team, will provide high-resolution images using filters to discriminate between Psyche's metallic and silicate constituents. It consists of a pair of identical cameras designed to acquire geologic, compositional, and topographic data.
The gamma ray and neutron spectrometer will detect, measure, and map Psyche's elemental composition. The instrument is mounted on a 7-foot (2-meter) boom to distance the sensors from background radiation created by energetic particles interacting with the spacecraft and to provide an unobstructed field of view. The science team for this instrument is based at the Applied Physics Laboratory at Johns Hopkins University.
The Psyche spacecraft will also use an X-band radio telecommunications system, whose team is led by MIT’s Maria Zuber and includes scientists at NASA’s Jet Propulsion Laboratory. This instrument will measure Psyche's gravity field which, when combined with topography derived from onboard imagery, will provide information on the interior structure of the asteroid.
“This is an unprecedented opportunity to map the structure of the metallic core of a planetary body,” says Zuber. “The results will inform understanding of planetary accretion as well as the geodynamical processes that dominated differentiated planetary bodies in the earliest solar system.”
In addition to Elkins-Tanton, ASU SESE scientists on the Psyche mission team include deputy principal investigator and co-investigator Jim Bell, co-investigator Erik Asphaug, and co-investigator David Williams.
NASA’s Jet Propulsion Laboratory managed by Caltech is the managing organisation and will build the spacecraft with industry partner Space Systems Loral (SSL). JPL’s contribution to the Psyche mission team includes over 75 people, led by project manager Henry Stone, project scientist Carol Polanskey, project systems engineer David Oh, and deputy project manager Bob Mase. SSL contribution to the Psyche mission team includes over 50 people led by SEP Chassis deputy program manager Peter Lord and SEP Chassis program manager Steve Scott.
Other co-investigators are David Bercovici (Yale University), Bruce Bills (JPL), Richard Binzel (MIT), William Bottke (Southwest Research Institute), Ralf Jaumann (Deutsches Zentrum fur Luft– und Raumfahrt), Insoo Jun (JPL), David Lawrence (Johns Hopkins University Applied Physics Laboratory), Simon Marchi (Southwest Research Institute), Timothy McCoy (Smithsonian Institution), Ryan Park (JPL), Patrick Peplowski (Johns Hopkins University Applied Physics Laboratory), Thomas Prettyman, (Planetary Science Institute), Carol Raymond (JPL), Chris Russell (UCLA), Benjamin Weiss (MIT), Dan Wenkert (JPL), Mark Wieczorek (Institut de Physique du Globe de Paris), and Maria Zuber (MIT).
NASA also announced its selection of a second Discovery Program class mission that will perform the first reconnaissance of the Trojans, a population of primitive asteroids orbiting in tandem with Jupiter.
Called “Lucy,” the mission will launch in 2021 to study six of these exciting worlds. “This is a unique opportunity,” says Harold F. Levison, Lucy principal investigator from Southwest Research Institute in Boulder, Colorado.
“Because the Trojans are remnants of the primordial material that formed the outer planets, they hold vital clues to deciphering the history of the solar system. Lucy, like the human fossil for which it is named, will revolutionise the understanding of our origins.”
“Understanding the causes of the differences between the Trojans will provide unique and critical knowledge of planetary origins, the source of volatiles and organics on the terrestrial planets, and the evolution of the planetary system as a whole,” says EAPS alumna Catherine Olkin ’88, PhD ’96, a Lucy deputy principal investigator now working at Southwest Research Institute.
Richard Binzel, who is also a member of the Lucy mission team says, of the twin announcements, “It's an amazing day to win on two missions. These distant Trojan asteroids may be hiding amazing clues for the chemistry of planets and life.” | 0.892363 | 3.661341 |
Reviewed by: Charlene Brusso
From Ad Astra Summer 2010
Title: How to Find a Habitable Planet
Author: James Kasting
NSS Amazon link for this book
Princeton University Press
Date: March 2010
Retail Price: $29.95
By the end of 2009, astronomers had compiled a list of more than 400 exoplanets: extrasolar planets orbiting other stars. Those distant planets are most likely too big, too gaseous, and too hot to support life, but the very fact that we can now discover these distant worlds means it’s time to start thinking about just how we might identify habitable planets that may be thousands of light years away.
Humanity has been wondering about life on other planets since around 300 B.C., when Greek philosopher Epicurus argued that Earth could not be unique in supporting life. Before we can go searching for those other life forms, however, it would help to have a list of the qualities that make a planet capable of hosting life, or at least life we might recognize from far, far away. Ever pragmatic, Kastings settles for beginning with the qualities that make a planet Earthlike.
First and most obviously, the planet needs to be rocky, rather than a gas giant. Next on the wish list is the existence of water on the planet’s surface. Biologists generally agree that life on Earth began in water, and surface water is much easier to detect from space than water hidden underground. Surface water also implies a climate range like Earth’s, one that’s fairly stable over millions of years, so primitive life has time to evolve into bigger, better, more complex forms.
Stable environments require the planet to occupy an optimal orbit around a stable main sequence star. Scientists call it the Goldilocks Problem: putting a planet at just the right distance from a star so that it gets just the right amount of solar radiation to help it maintain an energy balance. Too much solar radiation will boil off precious surface water; too little, and the fragile world freezes. Additional complexities arise from interlocking environmental feedback loops that control the abundance of ice, water vapor, methane, and carbon dioxide on the planet’s surface and in its atmosphere.
The size of the planet also matters. If it’s very large, it will become a gas giant, a brown dwarf, or hot Jupiter, like so many of the exoplanets found so far. But if it’s not big enough, a rocky planet will cool quickly as it coalesces – so much that its interior freezes and it becomes geologically dead, without vulcanism, or plate tectonics, or a spinning liquid core to make a magnetic field. The magnetic field is necessary to help protect the planet’s surface from dangerous solar and cosmic radiation.
It’s also helpful to have a few other, bigger planets in the solar system. Their gravitational pull can draw incoming comets and asteroids, reducing likelihood of impacts and Cretaceous-style mass extinctions.
So now that we know what we’re looking for, what’s the best way to find these Earth-like planets? After all, we’re looking for objects so small compared to their stars that it’s unlikely we’ll be able to see them directly. Fortunately, astronomers have developed a handful of clever round-about methods for finding small, hard-to-see objects.
Kasting is a distinguished professor of geosciences at Penn State University and an expert in the evolution of planetary atmospheres. He’s also an excellent writer, capable of breaking down complex topics into clear and accessible pieces. That skill makes this first-of-its-kind book not just unique but probably indispensible for students and armchair planetologists. He makes a few suggestions for how to find these exoplanets.
The most successful trick looks for the effects of a hypothetical planet on the light emitted by its star. Astrometry – the measurement of a star’s movement, in this case with infrared interferometry – can reveal wobbles caused by gravitational interaction between the star and its planets; the more massive the planet, the bigger the star’s wobble. Other methods include “transit spectroscopy,” looking for frequency shifts in the star’s spectral absorption lines caused by its light passing through the atmosphere of the orbiting planet; this works best with larger (and probably less Earth-like) worlds such as “hot Jupiters.”
The most exciting method uses gravitational microlensing – the same technique used by cosmologists to study distant galaxies. Here the lensing star passes in front of the source star and magnifies the source star’s light, so its apparent luminosity briefly brightens and then dims back to normal.
These methods all depend on reliable observations, both ground and space based. When the James Webb Space Telescope becomes operational in 2016, our ability to spot and accurately measure infrared signals will improve our chances of spotting exoplanets.
© 2010 Charlene Brusso
Please use the NSS Amazon Link for all your book and other purchases. It helps NSS and does not cost you a cent! Bookmark this link for ALL your Amazon shopping! | 0.872846 | 3.718099 |
Uncovering the Mystery
Large Hadron Collider, at CERN, in Geneva, Switzerland. We call them ultra-high energy cosmic rays (UHECRs) and they range in energy from above 1018 eV to 1020 eV.
For such small subatomic particles to be accelerated to such extreme energies, the sources have to be highly magnetized and energetic. The main suspects in this cosmic mystery are either Supermassive Black Holes in the centers of galaxies (named Active Galactic Nuclei) or explosive events in stars, which create an extremely fast spinning compact star, the birth of a young pulsar, or emit a large flux of gamma-rays in a short period (named gamma-ray bursts).
The best way to solve this mystery is to observe these particles at the highest energies in large amounts. At the highest energies ultra-high energy cosmic rays point back to their sources as magnetic fields do not affect these charged particles as much as their lower energy counterparts.
There is a great challenge in detecting their miniscule flux on Earth: one of these particles hit a square kilometer (or square mile) area on the ground every century or so! The good news is that the atmosphere transforms one miniscule particle with these extreme energies into hundreds of billions of particles with lower energy. This is Einstein's E=mc2 at work. One highly energetic particle can create many other particle-anti particle pairs through quantum mechanical processes and the energy-mass equivalence. The generated secondary particles excite the nitrogen in our atmosphere, which fluoresces isotropically. The fluorescence signal can be observed at very large distances, tens to hundreds of kilometers away from the track of the particle generated shower.
Pierre Auger Observatory leads this effort covering 3,000 km2 with detectors. The Telescope Array in Utah now reaches 700 km2 and will reach 3,000 km2 in the next few years. These two giant efforts have not yet solve the mystery but have found some hints that the sources are extragalactic and the sky distribution above 50 EeV (= 5 x 1019 eV) shows the signs of anisotropies.
Anisotropies on the sky distribution of UHECRs become apparent at the highest energies as the volume of the universe probed by these observations becomes limited due to the interaction of ultra-high energy cosmic rays and the cosmic microwave background radiation. This interaction is called the GZK effect after the co-discoverers: Greisen, Zatsepin, and Kuzmin.
The next generation of UHECR observatories to address the origin of the highest energy particles is designed to observe orders of magnitude more volume of the atmosphere than can be observed with a 3,000 km2 ground array. The best location to monitor large volumes of atmosphere is from space.
When the excited electrons return to the ground state, they emit ultraviolet (UV) fluorescence light (in a wavelength range of 330-400 nm). Measurements of this fluorescence can indicate the energy and arrival direction of the original cosmic ray.
The Cherenkov light originates from secondary particles traveling faster than the speed of light.
EUSO-SPB is planned for launch from Wanaka, New Zealand, starting on March 25, 2017, through NASA's CSBF (Columbia Scientific Balloon Facility).
Space missions proposed to solve this longstanding mystery that will be informed by the EUSO-SPB flight include:
EUSO-SPB was funded by NASA (award NNX13AH54G at the University of Chicago, PI Institution, award NNX13AH55G at Colorado School of Mines, Deputy PI Institution, Marshall Space Flight Center, award NNX13AH53G at University of Alabama, Huntsville, and award NNX16AG27G at City University of New York) and by the JEM-EUSO international collaboration. | 0.873801 | 4.160593 |
Astronomers have decoded a weird signal coming from a strange, 3-body star system
Last Updated on
A 2016 NASA illustration depicts a different brown dwarf, oribiting further away from its host star.(NASA)
Once or twice a day, a strange object in the Milky Way blinks at us. Now, astronomers think they know why.
The object is called NGTS-7, and to most telescopes it looks like a single star. Researchers at the University of Warwick in England started watching because it seemed to be emitting flares, but on closer examination they noticed that its starlight dims briefly every 16.2 hours. When the astronomers zoomed in, they realized there are actually two similarly sized stars in the system, and that only one of them is dimming briefly in that way — suggesting that there’s something dark circling on or just above the star’s surface. Now, in a paper posted to the preprint journal arXiv, the astronomers offer an explanation: A brown dwarf is orbiting one of the stars, in an orbit so tight that it takes just 16.2 hours to complete.
It’s impressive that the astronomers involved were able to parse the complicated signal from this system, disentangling where the intermixed light from the brown dwarf and the two small, young stars originally came from, said Hugh Osborn, an astronomer at the Laboratoire d’Astrophysique de Marseille in France, who was not involved in the research. [11 Fascinating Facts About Our Milky Way Galaxy]
To pull it off, the researchers applied a similar technique to that used to detect exoplanets: Measuring how the light dipped as the brown dwarf passed between its host star and Earth. This dip represents the signal of a “transit”: a brief, partial eclipse of the star by something too small and dim to see directly, even through a powerful telescope.
“Detecting this system is probably the easy bit,” Osborn told Live Science. “Because the star is so small and the brown dwarf relatively large, the transit signal is actually about 10 times larger than that of [a typical exoplanet that turns up in surveys of the night sky].”
But once you detect the transit signal, you have to make sense of it. That’s tricky because brown dwarf transit signals are strange. For one thing, they tend to glow faintly from internal heat and the heat of nearby stars.
“The typical brown dwarf temperature is somewhere between luke-warm water, which would appear black to our eyes, and a campfire, which would glow faintly red,” Osborn said. “In the case of [this system], the brown dwarf is being heated by the star it orbits, meaning the dayside of the object would be glowing red hot. The night side would be darker, but some of this heat would be sucked around by winds, heating it up.”
Any detection of a brown dwarf is exciting, Osborn said. The objects are several dozens of times larger than Jupiter or the big exoplanets scientists typically detect, but not quite heavy enough to light up with nuclear fusionlike a star. Because of their large size, they should be easy to spot passing in front of stars, Osborn said. But they’re rare: Fewer than 20 have ever been discovered transiting in front of stars like this, and only about 1,000 have been discovered elsewhere in the galaxy. In comparison, astronomers have already found thousands of exoplanets. For that reason, astronomers talk about there being a kind of “brown dwarf desert,” at least in the region of space we can clearly observe.
“The fact that we have so few of them … must be because they are extremely rare, and not because we’ve simply missed them,” Osborn said.
This one is especially weird, even for a brown dwarf, due to its near proximity to its host star, Osborn said.
It appears to have been nudged into its tight orbit by gravity from the other star in the system.
Now it’s perfectly synchronized with its host star, with the two objects spinning and orbiting such that one side of the planet always faces one side of the star, as if they were connected by a string.
It’s interesting, Osborn said, “that the orbit of the brown dwarf appears to have ‘spun up’ the orbit of the star.”
Satellites don’t typically have this effect on their host stars, Osborn added.
The researchers can tell the two objects are synchronized in this way because other shadows on that star’s surface, probably sunspots, appear to be co-rotating on that same 16.2-hour cycle in some observations. (This is more of that trickiness that made this analysis so difficult.)
Over time, the researchers wrote, magnetic forces from the host star will slow the brown dwarf’s orbit, causing the orbit to shrink and the transits to happen even more regularly. Eventually, in the not-too-distant future (at least in stellar terms) the brown dwarf’s orbit should collapse entirely and it will fall into its host star. The resulting fireworks show — picture a warm bowling ball slamming into a giant water balloon of super-hot plasma — should be spectacular to behold for the astronomers who are alive when it happens.
In the meantime, Osborn said, he’d like to see researchers double-check that the two true stars in the system really are locked together in their own, wider orbits. | 0.855837 | 3.65806 |
Say hello to Powehi.
The ground-breaking black hole photo that's blanketed social media this week has an official name thanks to a Hawaiian language professor at the University of Hawaii at Hilo.
Astronomers involved with the project approached Professor Larry Kimura to ask him for help to name the black hole located some 55-million light-years away from Earth in the nearby Virgo galaxy cluster.
"It is awesome that we, as Hawaiians today, are able to connect to an identity from long ago, as chanted in the 2,102 lines of the Kumulipo, and bring forward this precious inheritance for our lives today," Kimura said in a statement.
"To have the privilege of giving a Hawaiian name to the very first scientific confirmation of a black hole is very meaningful to me and my Hawaiian lineage that comes from po," he added. "I hope we are able to continue naming future black holes from Hawaii astronomy according to the Kumulipo."
The name was chosen for its roots in the Kumulipo, an 18th-century Hawaiian chant that describes creation. The word comes from two terms in the chant: Po, which means profound dark source of unending creation, and (wehiwehi), which is one of the ways that po is described in the chant.
Powehi was imaged thanks to more than 200 scientists working together to network a series of ground-based telescopes around the world known as the Event Horizon Telescope.
The photo shows an uneven ring of orange light surrounding a dark circle. The orange halo represents hot gas emissions located near the black hole's event horizon - the point where nothing, not even light, can escape the hole's massive gravity well. Powehi is massive with scientists estimating it to be more than seven BILLION times more massive than our own sun.
Black holes are made up of enormous amounts of matter all crammed together in a small space, warping gravity in its area. A black hole's gravity well is so strong that it draws in everything around it, including light. Albert Einstein's theory of general relativity describes gravity as the result of matter and energy warping space, much like a stretched out sheet will sag under the weight of a bowling ball in the middle. When too much matter and energy is concentrated in one place, space-time can collapse, resulting in a black hole like the one imaged by the EHT team.
Scientists believe black holes are common in the universe with many super-massive black holes located at the heart of every galaxy.
Photo: National Science Foundation | 0.832311 | 3.260434 |
For more than a decade, astronomers across the globe have wrestled with the perplexities of fast radio bursts — intense, unexplained cosmic flashes of energy, light years away, that pop for mere milliseconds.
Despite the hundreds of records of these enigmatic sources, researchers have only pinpointed the precise location of four such bursts.
Now there’s a fifth, detected by a team of international scientists that includes West Virginia University researchers. The finding, which relied on eight telescopes spanning locations from the United Kingdom to China, was published Monday (Jan. 6) in Nature.
There are two primary types of fast radio bursts, explained Kshitij Aggarwal, a physics graduate student at WVU and a co-author of the paper: repeaters, which flash multiple times, and non-repeaters, one-off events. This observation marks only the second time scientists have determined the location of a repeating fast radio burst.
But the localization of this burst is not quite as important as the type of galaxy it was found in, which is similar to our own, said Sarah Burke-Spolaor, assistant professor of physics and astronomy and co-author.
“Identifying the host galaxy for FRBs is critical to tell us about what kind of environments FRBs live in, and thus what might actually be producing FRBs,” Burke-Spolaor said. “This is a question for which scientists are still grasping at straws.”
Burke-Spolaor and her student, Aggarwal, used the Very Large Array observatory in New Mexico to seek pulsations and a persistent radio glow from this burst. Meanwhile, Kevin Bandura, assistant professor of computer science and electrical engineering, and third WVU co-author of the article, worked on the Canadian Hydrogen Intensity Mapping Experiment team that initially detected the repeating fast radio burst.
“What’s very interesting about this particular repeating FRB is that it is in the arm of a Milky Way-like spiral galaxy, and is the closest to Earth thus far localized,” Bandura said. “The unique proximity and repetition of this FRB might allow for observation in other wavelengths and the potential for more detailed study to understand the nature of this type of FRB.”
Using a technique known as Very Long Baseline Interferometry, the team achieved a level of resolution high enough to localize the burst to a region approximately seven light years across – a feat comparable to an individual on Earth being able to distinguish a person on the moon, according to CHIME.
With that level of precision, the researchers could analyze the environment from which the burst emanated through an optical telescope.
What they found has added a new chapter to the mystery surrounding the origins of fast radio bursts.
This particular burst existed in a radically different environment from previous studies, as the first repeating burst was discovered in a tiny “dwarf” galaxy that contained metals and formed stars, Burke-Spolaor said.
“That encouraged a lot of publications saying that repeating FRBs are likely produced by magnetars (neutron stars with powerful magnetic fields),” she said. “While that is still possible, the fact that this FRB breaks the uniqueness of that previous mold means that we have to consider perhaps multiple origins or a broader range of theories to understand what creates FRBs.”
At half-a-billion light years from Earth, the source of this burst, named “FRB 180916,” is seven times closer than the only other repeating burst to have been localized, and more than 10 times closer than any of the few non-repeating bursts scientists have managed to pinpoint. Researchers are hopeful that this latest observation will enable further studies that unravel the possible explanations behind fast radio bursts, according to CHIME.
WVU has remained at the research forefront of fast radio bursts since they were first discovered in 2007 by a team right here at the University that included Duncan Lorimer and Maura McLaughlin, physics professors, and then-student David Narkevic. The trio discovered fast radio bursts from scouring archived data from Australia’s Parkes Radio Telescope.
Title: A repeating fast radio burst source localized to a nearby spiral galaxy
CONTACT: Jake Stump
Director, WVU Research Communications
Call 1-855-WVU-NEWS for the latest West Virginia University news and information from WVUToday.
Follow @WVUToday on Twitter. | 0.839828 | 3.913371 |
Planetary science focuses on many aspects of planetary objects, from their deep interiors to the distant influences of a planet’s gravitational or magnetic field far from the planet’s surface. LASP planetary scientists study data from ground, telescope, and space-based instruments to understand the origins of our solar system and the planets, planetary dust, and electric fields within it.
Scientists at LASP also develop theoretical models of different components of planetary systems, including:
- Geological processes on Mars
- Evolution of Saturn’s ring system
- Interaction of magnetospheric plasma with the volcanic atmospheres of Io and Enceladus
- Escape of atmospheres from Mars, Mercury, and Pluto
- Bizarre chemistry of Titan’s atmosphere
- Charging of dust grains on the surface of the moon | 0.881244 | 3.18206 |
You Asked, Our Astronomers Answered!
Header Image: A beautiful image of The Whirlpool Galaxy taken by an Adler Planetarium Telescope Volunteer. Image Credit: Bill Chiu
Our universe is vast, mysterious, and ever expanding! Astronomers are constantly discovering and uncovering new secrets about space, which we know can lead to lots of questions. What is a black hole? When can you see the ISS? How old is the universe really? Well, you asked and our astronomers answered. Here are answers to some of the most frequently asked questions Adler Planetarium astronomers receive.
Is it more likely humans could inhabit Mars or Venus first?
“Mars and Venus would be very different places to live! Venus has a thick atmosphere that traps a lot of heat, so it is over 800 degrees Fahrenheit on its surface, while Mars has a thin atmosphere and is really cold. If you had to pick a planet to live on besides Earth, Mars is your best bet.” – Astronomer Lucianne
How are black holes formed?
“Black holes come in different sizes. The small ones are from collapsed stars a few dozen times as massive as the Sun. The supermassive blackholes, millions or billions of times larger than the small one, well… we don’t know how they form.” – Astronomer Geza
What’s inside a black hole?
“We don’t really know, because once something goes in, it can’t come out! But our best theory right now, Einstein’s Theory of General Relativity, says that inside a black hole space and time get more and more twisted until at the very center they cease to exist. We don’t think this can be quite right, but we don’t yet have a better description.” – Astronomer Geza
Learn more about black holes and the first-ever up close picture taken of one here.
Why is there currently a debate on the age of the universe?
“Measuring how fast the universe is expanding (the Hubble Constant) leads you to the age of the universe. You just track back to when the universe would have zero size. In detail it turns out it is actually a bit more complicated than that, because the rate of the universe’s expansion changes over time. To model that you need to know what the universe is made of (how much dark matter and dark energy it has, for example). We can do that, however, it seems like the different techniques we use to measure the age of the universe give different results. In particular measurements done on the early universe using the cosmic microwave background give an older universe than measurements of the modern universe. Why are they different? There are two main possibilities. First: either one (or both) of the measurements is slightly off, or second: perhaps there is something missing from our theories.” – Astronomer Mark S.
What are moons?
“Moons are things that orbit around planets, dwarf planets, and minor planets (aka, asteroids) rather than around the Sun. They are also called “natural satellites” for this reason.” – Astronomer Mark H.
Can you see the International Space Station at night shining from reflected sunlight?
“Absolutely! The ISS is big and it has many pieces that are highly reflective, like large solar panels. The ISS is best seen either after sunset or before sunrise, depending on the date, and your location. While it may still be dark here on the ground, up at the altitude of the ISS, it will already be sunny or it is still sunny.” – Astronomer Michelle
Why do stars flicker while planets don’t?
“Stars (other than our Sun) are so far away we see them as points of light. Earth’s atmosphere causes those points of light to flicker. Planets look like small disks in a telescope – the atmosphere’s effect isn’t quite the same. On the Moon, stars won’t flicker!” – Astronomer Grace
Learn how to properly identify planets here.
How do light years work? It seems confusing and how accurate is that measurement?
“A light year is the distance light travels in one “Julian” year. Both the speed of light and the Julian year are exactly defined, so one light year is exactly 9460730472580800 meters. The distance to stars and galaxies is another kettle of fish entirely!” – Astronomer Geza
When will Pluto complete its first full revolution around the Sun since its discovery?
“Pluto was discovered in 1930. It takes Pluto 248 years to orbit the Sun, so it will complete its first full revolution around the Sun since its discovery in the year 2178. In the Star Trek universe, Spock’s father Sarek will enter his teens (in Earth years) that year.” – Astronomer Grace
If Betelgeuse goes supernova, will its name change? And how long post supernova will it take for us to actually see it?
“When a star like Betelguese goes supernova most of its material is blown out into a vast glowing cloud of gas. So Betelguese will become “The nebula formerly known as Betelguese”… But there will also be a tiny remnant, a very hot and fast rotating neutron star. It is still the same star, but because it is so different I’m guessing the IAU will give it a new name. We’ll have to see! Surprisingly, the distance to Betelguese isn’t very well known. It is probably between 600 and 700 light years away from Earth, so we’ll see the explosion 600 to 700 years after it really happens. In fact, it might have exploded already and the light simply hasn’t reached us yet!” – Astronomer Geza
What is your favorite mind-blowing space fact?
“The hydrogen in the water you drink, the “H” in H2O, was created in the Big Bang. The oxygen, O, was created inside massive stars that later exploded.” – Astronomer Michelle
How do we know that so much of the universe if made of dark matter and dark energy?
“Dark matter and dark energy could be called “known unknowns” – we can infer their presence by the way they interact with other things in the Universe.” – Astronomer Grace
We love talking space! If you have more questions, ask us on Instagram and Twitter by using the hashtag #AskAdler. You can learn how telescopes work in our latest Astronomy In 3 Minutes episode or submit a question to one of our astronomers directly on the Ask Adler resources page. | 0.814618 | 3.54749 |
What is CTA?
CTA is a large-scale global project to build a new generation of Cherenkov telescopes dedicated to the study of the Universe in very high-energy gamma-ray. It will be the largest, most sensitive and advanced instrument ever built for gamma-ray astronomy and the first ground-based observatory of its kind open to the world-wide astronomical and particle physics community.
The observatory will be located on two sites, each in a hemisphere. In the north, the location of CTA is at the Observatorio del Roque de los Muchachos, of the Instituto de Astrofísica de Canarias (IAC), on the island of La Palma (Spain). In the southern hemisphere, CTA is located in the Paranal Observatory of the European Southern Observatory (ESO), in the Atacama Desert (Chile).
CTA will host three types of telescopes: Large-Sized Telescopes (LSTs), Medium-Sized Telescopes (MSTs) and Small-Sized Telescopes (SSTs) to cover a wide range of gamma radiation reaching from 20 GeV up to 300 teraelectron volts (TeV). The plan for the northern site includes 4 LST and 15 MST, while the southern site will feature all three telescope types: 4 LST, 25 MST and 70 SST. Overall, CTA will have unprecedented accuracy and will be 10 times more sensitive than existing instruments.
The planning for the construction of the Observatory is managed by the CTAO gGmbH, which is governed by the CTA Council made up of shareholders and associate members from a growing number of countries. The CTAO gGmbH works in close collaboration with the CTA Consortium, which includes more than 1,400 scientists and engineers from 31 countries involved in the scientific and technical development of CTA. An intergovernmental agreement is being prepared for the construction and subsequent operation of the observatory, for which a European Research Infrastructure Consortium (ERIC) is foreseen.
The construction of CTA will have a total cost of more than 200 million euros, of which it is estimated that 90 million will be dedicated to the telescopes that are being installed in La Palma. The CTA-North array, which is expected to come into operation in 2024, will have an estimated investment, both in purchases of goods and services and in hiring personnel, of more than 2 million euros per year.
The actions of the IAC in the CTA project are financed by the project "Los cuatro Large Size Telescopes (LST) del CTA-Norte en el ORM” of reference ESFRI-2017-IAC-12 of the Ministerio de Ciencia, Innovación y Universidades, 85% co-financed with European Regional Development Funds (ERDF) of the Operational Programme for Intelligent Growth 2014-2020, with the co-financing of Fondos de Desarrollo de Canarias (FDCAN), from the Cabildo Insular de la Palma (2016-2018), and funding from the Gobierno de Canarias, through the Agencia Canaria de Investigación Innovación y Sociedad de la Información (ACIISI).
Science with CTA
Ground-based gamma-ray astronomy is a young field with enormous scientific potential. CTA will be sensitive to the highest-energy gamma rays, making it possible to study the physical processes at work in some of the most violent environments in the Universe.
CTA will be a unique data source that will not only allow a deep and precise understanding of the already known objects and mechanisms of the Universe, but will also be able to detect new kinds of gamma-ray emitters and new phenomena, and will bring revolutionary discoveries in fundamental physics.
In our Galaxy, CTA will be able to observe:
- Remnants of supernova explosions (SNR) and new pulsar wind nebulae (PWNe), which will allow us to delve into the origin of cosmic rays.
- New binary systems composed of two stars or formed by a star and a compact object (like neutron star or black hole).
Beyond the Milky Way, CTA will be able to detect:
- The most luminous cosmic explosions, named gamma-ray bursts, in their initial phases.
- Active galactic nuclei (AGNs), some of which are still undetected in the gamma-ray regime.
- Star-forming galaxies, including so-called star-burst galaxies.
- Clusters of galaxies, which are promising targets to detect dark matter, as well as to investigate cosmicray acceleration.
Gamma rays detected with CTA may also provide a direct signature of dark matter, evidence for deviations from Einstein’s theory of special relativity and more definitive answers to the contents of cosmic voids, the empty space that exists between galaxy filaments in the Universe.
CTA will not detect gamma rays directly, as these actually never reach the earth's surface, but "Cherenkov light". Gamma rays interact with the Earth's atmosphere, producing cascades of subatomic particles that travel at higher speeds than light in the air. This rain of very high-energy charged particles generates a blue light cone called Cherenkov radiation. The duration of the light pulse is one billionth of a second and its brightness is too weak to be detected by the human eye. However, CTA will be able to efficiently capture this type of radiation thanks to its large light-collecting mirrors and ultra-sensitive detectors.
LSTs are designed to capture brief, low-energy gamma ray signals (20 GeV - 3 TeV). They are 45 m high and weigh about 100 tonnes. The mirrors are 23 m in diameter, while the cameras will have a field of view of 4.5 degrees. They are able to re-position to a new target in the sky within 20 seconds.
The MSTs cover the middle of the CTA's energy range (80 GeV - 50 TeV). They are 27 m high and 80 tonnes in weight. The mirrors of the MSTs are 12 m in diameter and the field of view of their cameras is 7.5-7.7 degrees.
The SSTs are sensitive to the highest energy gamma rays (1-300 TeV). Their mirrors are about 4 m in diameter and their cameras have a wide field of view of 8-10 degrees. They are 9 m high and weigh between 9 and 19 tonnes. The SSTs will be spread out only in the southern hemisphere.
In total, CTA will use more than 7,000 highly-reflective mirror facets (90 cm to 2 m diameter) to focus light into the telescopes' cameras. The cameras will use high-speed digitalization and triggering technology capable of recording shower images at a rate of one billion frames per second and sensitive enough to resolve single photons.
It will have photomultiplier tubes (PMTs) and silicon photomultipliers (SiPMs) for a total of more than 200,000 ultra-fast pixels responsible for converting the light into an electrical signal that will then be digitized and transmitted. SiPMs can operate during high levels of moonlight, improving the CTA's efficiency in collecting Cherenkov light during moonlight conditions.
CTA is a "Big Data" project. The Observatory is expected to generate approximately 100 petabytes (PB) of data in the first five years of operations.
The project to build the CTA is well-advanced: the prototype of the Medium-Size Telescope and the three proposed designs of the Small-Size Telescope have achieved "first light", and the prototype of the Large-Size Telescope, the LST-1, was inaugurated in October 2018. These prototypes should be tested before being considered for acceptance by the CTA Observatory. | 0.872541 | 3.077979 |
Gravitational Waves from GW190425
Predicted in Albert Einstein’s general theory of relativity, gravitational waves are emitted by accelerating objects. Two stars orbiting one-another in a binary system will lose energy from the emission of gravitational waves, causing the separation between the two stars in the binary to decay over time. Additionally, if the binary is in a non-circular eliptical orbit, known as an eccentric orbit, the orbits will gradually become more circular over time. For two sufficiently close and dense compact objects, such as neutron stars or black holes, this leads to an inspiral where the stars become closer in an increasingly circular orbit.
On the 25th of April 2019, Advanced LIGO/Virgo made the second detection of gravitational waves (GW) originating from a double neutron star (DNS) inspiral. Advanced LIGO/Virgo observes gravitational waves by measuring the stretching and squeezing of space as the waves pass over two perpendicular 4km long tunnels. The gravitational wave, GW190425, is particularly interesting as it originated from an enormous double neutron star system.
The combined mass of GW190425 was inferred to be ; that is 3.4 times the mass of our Sun whilst each star is roughly just ~km across! The total mass of GW190425 is inconsistent with previously observed double neutron stars at a level, indicating that we may have just uncovered a new population.
Coalescing neutron stars in a simulation of GW190425, CoRe collaboration
The closer the stars get, the faster their orbital velocities become as they circle around each other. The orbital period (time taken for one revolution) decreases; reflected in the gravitational waves as an increasing frequency. The crescendo of the gravitational wave frequency is known as a chirp. The chirp ends with a merger between the two neutron stars, forming a supramassive neutron star or a black hole.
The sound of a chirp from two black holes colliding (GW150914 converted into sound waves, headphones recommended), LIGO
3.4 Times the Mass of our Sun?!
The observation of such a massive neutron star binary points us towards one of the most exciting questions in astrophysics: how do stellar binaries form and evolve? Currently, there are two predominant formation scenarios for compact binaries, which not only includes binary neutron star formation but also binary black holes and neutron star-black hole binaries.
In the dynamic formation scenario, two compact objects (neutron stars/black holes) form individually in a dense stellar environment such as a globular cluster, a collection of stars orbiting the core of a galaxy. These two compact objects are later brought together via dynamical interactions to form a binary.
In isolated binary evolution, two stars begin in an orbit where one of the stars begins to grow in size as it burns off the remainder of its hydrogen. The larger star may get too large and too close to the smaller star, causing its outer layer of hydrogen to be gravitationally pulled onto the smaller star, forming a common envelope of hydrogen that surrounds both stars. This mass transfer continues until the hydrogen layer of the larger star has been stripped off, leaving a helium star. Sometime later, this helium star will undergo a supernova explosion, collapsing into a neutron star. Later, the second star will also undergo a supernova and become a neutron star, leaving a binary neutron star.
The implied detection rate from GW190425 is higher than we expect from the dynamical channel, and the total mass is difficult to explain through standard isolated binary evolution. Therefore neither scenario fits well for explaining the origin of GW190425.
Possible Explanation: Unstable Case BB Mass Transfer
Illustration: Carl Knox
Unstable case BB mass transfer is a variation of isolated binary evolution. Following the standard scenario, a binary may consist of a primary neutron star with a high-mass Helium star companion (Panel A). Unstable case BB mass transfer occurs when Helium is pulled off the Heleium star onto the neutron star, forming a common envelope which now engulfs the neutron star and a remaining carbon-oxygen core (Panel C).
Friction caused by the stars orbiting inside the common envelope transfers angular momentum to the surrounding helium, eventually ejecting the envelope leaving a tight binary orbit with an period of less than 1 hour (Panel D).
Sometime later the carbon oxygen core undergoes a supernova explosion (Panel E), collapsing into a second neutron star. During the supernova, the asymmetric distribution of mass in the collapse gives the neutron star a kick. This kick gives the star a boost in a random direction, leading to an elongated orbit with significant eccentricity.
Generally, supernova kicks are thought to disrupt many binaries, providing the star with an orbital velocity greater than its escape velocity. But this is not the case for unstable case BB binaries due to the helium envelope leaving a tightly bound orbit that is more likely to remain bound after a kick.
Unstable case BB mass transfer is a great candidate for explaining the origin of GW190425 for several reasons:
- Simulations from Ivanova et al. in 2003 showed that a heavy He star-NS binary can survive unstable case BB mass transfer, with one of their simulated binaries retaining a helium star after the common envelope.
- For the more massive binaries, there is a higher chance for unstable case BB mass transfer to occur, which leads to a tightly bound orbit allowing these binaries to almost always survive the supernova kick due to their very tight orbit. Where high mass supernova in wider orbits are more likely to be disrupted.
- The short orbital period of less than one hour makes these binaries unlikely to be detected in radio pulsar surveys, due to severe Doppler smearing. As well as a relatively short time to merger of less than 10 million years, which makes them unlikely to be detected before they merge when compared to other long-lived DNS. Perhaps explaining why we would not have observed DNS this heavy before.
Searching for Signs of Eccentricity
In our recent paper, we propose that GW190425 may have formed as an isolated binary via unstable case BB mass transfer. Where the first common envelope left a binary consisting of a neutron star and a helium star with an orbital period of days. The unstable case BB mass transfer may have accreted of mass onto the first born neutron star during the second common envelope. The second supernova ejected of mass leaving a DNS, likely with significant eccentricity as a result of the kick.
The eccentricity, , describes the ellipticity of the orbit where is a circular orbit and the orbit becomes increasingly elongated as .
Two equal masses orbiting a common barycenter with an eccentric orbit .
To test our hypothesis, we measured the eccentricity of GW190425 using the LIGO/Virgo gravitational wave data so that we could compare it to expected eccentricities of simulated unstable case BB binaries.
The main plot from our paper, showing probabilities of very small eccentricities ( scale) from the GW190425 signal and of simulated unstable case BB mass transfer binaries. Shown at a frequency of 10Hz.
It is possible that GW190425 formed through unstable case BB mass transfer. However we were not able to distinguish the small eccentricity of GW190425 as binaries that form through this channel have circularised to by the time they’re detectable by Advanced LIGO/Virgo (a minimum frequency of 20Hz). Though we do find that future detectors which are able to detect gravitational waves at lower frequencies, such as the Cosmic Explorer and the space based LISA mission, will enable us to resolve these eccentricities and allow us to distinguish unstable case BB mass transfer binaries.
In a later post I hope to cover: some technical details of our method from Isobel Romero-Shaw, who led our team in measuring the eccentricity of GW190425; how we simulated eccentricities of unstable case BB mass transfer binaries; and some further prospects in measuring the eccentricity of merging neutron stars.
For more details and citations, see my honours thesis and the paper that our team (Isobel Romero-Shaw, myself, Simon Stevenson, Eric Thrane, Xing-Jiang Zhu) put together; currently awaiting publication. | 0.893449 | 4.100661 |
The Calendar below shows the 9 top Meteor Showers that occur every year. The biggest factors in watching these Meteor Showers are weather and the Brightness of the Moon. We all love the Full Moon but it can really ruin a good Meteor Shower. The best time to see a meteor shower is when the moon is close to a New Moon with a low brightness. The Calendar below is meant to be a quick reference guild to show the phase of the moon on the peak day of each meteor shower. Click on the moon for each shower to get more details on the moon phase for that day.
In ancient times there were a lot of crazy ideas about meteors and meteorite showers. Many people and cultures speculated that the streaks of light in the night sky were moon dust and rocks cast off of the moon as it traveled around the Earth. In modern times, we know that the major meteor shows listed on our calendar are caused by a parent object that is traveling through space casting of dust and tiny rocks. All of the parent objects are comets with only the Quadrantids in January and Geminids in December having Asteroids as parent object. This is what makes these showers so predictable from year to year. The Earth will pass through the debris trail of these objects as we travel around the sun at the same time each year.
But parent objects only account for the major showers. Shooting stars can be seen on any given night of the year and the Earth atmosphere is constantly being bombarded by these kind of meteorites. So where do these come from? Turns out space is filled with tiny bits of rock, metal and dust left over from when the solar system was created. When we see a random shooting star it's one of these tiny objects being burned up in the Earth atmosphere. If the rock is big enough it can survive this impact and hit the surface of the Earth. To date there are around 61,000 meteorites that have been found on Earth.
Our ancient relatives didn't have it completely wrong when they guessed shooting stars might be coming form the Moon. In 1982 an expedition to Antarctica brought back a meteorite that they knew was a little different. It was named "Allan Hills 81005" and ended up in the Smithsonian Institute where a scientist noticed that the meteorite's chemical composition resembled that of Moon rocks that had been brought back by the Apollo Missions to the moon in the 1960s and 70s. This was the first known meteorite that originated from the Moon. A few years later Scientist in Japan discovered they too had a Moon meteorite by using the same method. To date there are under 200 known meteorites on Earth that have been identified as being from the Moon.
Rocks that are floating around in space and eventually end up on Earth are caused by other meteorites, asteroids or comets hitting the Moon. When a rock that is floating in space comes in contact with Earth's atmosphere, the heat from the friction is so high to burn small meteorites giving us therefore the classic shooting star. Some bigger meteorites survive the impact and land on Earth like the Moon Meteorite found in Antarctica. The same thing happens on the Moon but since the Moon has less atmosphere to slow down the space rock and it hits the surface of the moon making a crater. There is also less gravity on the Moon and when the crater is created rocks and Moon dirt can get thrown high out of the Moon gravitational force and end up floating in space. Some get caught in Earth gravitational pull.
Like Lunar Meteorites, Martian meteors start on the planet Mars and are ejected into space when an asteroid or comet hits Mars surface. Mars meteorites are very rare with only around 120 having been identified as of 2013. They are identified as Martian meteors by comparing their chemical composition with data collected from spacecraft that have landed on the Mars surface.
One of the more famous of these Martian meteors is ALH 84001 that was discovered in the Allen Hills of Antarctica in 1984. It is speculated to be one of the oldest pieces of the universe ever found on Earth. It formed over 4 billion years ago. Tests show that it was formed at a time when Mars may have had flowing water. In 1996, scientists from NASA studying ALH 84001 with an electro microscope found structures they claimed could possibly be fossilized bacteria-like lifeforms. | 0.880913 | 3.409004 |
The most distant object ever explored by spacecraft is a reddish, snowman-shape rock 4 billion miles from Earth.
The object, nicknamed Ultima Thule, was photographed by NASA's New Horizons spacecraft during a late-night rendezvous on the first day of 2019. It is the first inhabitant of the Kuiper belt - the ring of rocky relics that surrounds the outer solar system - that scientists have seen up close.
Its odd shape, which scientists term a "contact binary," indicates that it formed as two spherical rocks slowly fused together in the early days of the solar system. This finding lends support to a theory of planet formation that suggests worlds are born from slow accumulation, rather than catastrophic collisions, researchers said.
"This is exactly what we need to move the modeling work on planetary formation forward," said Cathy Olkin, the mission's deputy project scientist. "Ultima is telling us about our evolutionary history."
New Horizons's encounter with Ultima Thule happened so far away that it took six hours for signals traveling at the speed of light to reach Earth. Scientists didn't receive confirmation that the spacecraft survived until Tuesday morning, and the first scientific results didn't start streaming in until that night.
Researchers at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, where New Horizons is operated, were up late, working to transform those bits of data into the first high-resolution image of a Kuiper belt object.
The black-and-white photo was taken from about 30,000 miles away, as New Horizons sped toward its target at 32,000 miles per hour.
"Spectacular," principal investigator Alan Stern said at a Wednesday news conference at which he displayed the early images from the flyby. He described watching his colleagues jump out of their seats and embrace one another upon seeing the compelling, crystal clear image. "That's elation," he said. "And it's just the tip of the iceberg."
Scientists had suspected that Ultima Thule would not be perfectly round since the summer of 2017, when a global network of observers found the rock passing in front of a distant star. But the Kuiper belt object is so distant and so dim that even the most powerful telescopes saw it only as a flicker of light in the sky. Even as New Horizons sped toward its target, in the hours before closest approach, Ultima Thule resembled little more than a blurry bowling pin.
But now "it's a world," Stern said - with shape, character and implications for our understanding of planetary science.
Jeff Moore, New Horizons geology team lead, said Ultima Thule likely formed in the first few million years of the solar system from a swirl of smaller objects. Over time, dust and pebbles clumped together to form the object's two lobes, which eventually combined to form a single body. The lack of evidence for damage at the sight of the collision suggests that the joining was probably gentle, like tapping someone's bumper as you fit into a tight parking space, Moore said. "You don't need to fill out any paperwork."
This would make Ultima Thule a lot like the early planetesimals from which larger worlds - including our own - ultimately formed. But unlike the planets, which have undergone dramatic geologic change, and comets, which are heated and transformed by the sun, the Kuiper belt object has existed in a "deep freeze" since it first formed, 4.6 billion years ago.
"What we think we're looking at is the end product of a process that took place at the very beginning of the formation of the solar system," Moore said. He called New Horizons "a time machine," capable of taking scientists back to the moment of our origins.
Color images from New Horizons reveal that, like other Kuiper belt objects, it has a dark reddish hue. This is something of a mystery, because Ultima Thule is thought to be made mostly of ice. But researchers think radiation in this dark and distant part of the solar system could interact with contaminants in the ice, changing their color. Early observations about its chemical composition are expected to arrive Thursday, and they may help explain the phenomenon more.
And there are many more oddities to be explored, scientists said. Olkin pointed out dramatic variations in brightness that speckle the object. Moore noted that the early images did not show any solid evidence of impact craters; additional images may reveal whether Ultima Thule has been struck in the past or is worn smooth.
It will take as long as 20 months for scientists to download and process all the data collected during their brief encounter with Ultima Thule, scientists said. That includes a brief delay next week, when the sun comes between the Earth and the spacecraft, blocking all transmissions.
And New Horizons' mission isn't over, Stern said. The spacecraft's subsystems are healthy, and it has sufficient fuel to operate for another 15 to 20 years. He and his colleagues plan to apply for NASA approval to extend their mission, either to conduct another Kuiper belt object flyby or explore other aspects of the outer solar system.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.) | 0.855877 | 3.770608 |
A NASA probe's epic encounter with a small body in the far outer solar system is telling us a lot about how planets are born.
On Jan. 1, 2019, the New Horizons spacecraft zoomed within just 2,200 miles (3,540 kilometers) of Arrokoth, a 22-mile-wide (36 kilometers) object in the Kuiper Belt, the ring of frigid bodies beyond Neptune's orbit.
It was the most distant planetary flyby in the history of spaceflight. Arrokoth lies 4.1 billion miles (6.6 billion km) from Earth — about 1 billion miles (1.6 billion km) farther away than Pluto, which New Horizons cruised past in July 2015.
New Horizons found Arrokoth to be a suitably exotic denizen of this far-off realm, as the mission team reported last May in a study in the journal Science detailing the flyby's initial science returns. The probe's observations revealed a remarkably red object composed of two distinct lobes, both of which are surprisingly flattened. Arrokoth thus looks like a space snowman, albeit one that's been beaten and bloodied.
That snowman shape indicates that Arrokoth formed via a merger of two separate objects, and that this coalescence happened very long ago, back when impact speeds in the outer solar system were quite low. (Collisions in the modern Kuiper Belt are too violent to produce an object with lobes as distinct and undamaged as Arrokoth's, New Horizons team members have said.)
So, Arrokoth is a primordial body — a planetary building block, or planetesimal, left over from the solar system's very early days. And each of its two lobes apparently came together in the same swirling, gravitationally collapsing cloud of dust and gas in the Kuiper Belt, far from the newborn sun, the researchers wrote in the May 2019 study.
That initial interpretation has stood the test of time, it turns out.
The mission team published three new Arrokoth papers online today (Feb. 13) in Science, reporting analyses of 10 times more flyby data than was at hand during the writing of last year's study. (It takes a while for New Horizons to beam big datasets home.) The new studies largely confirm and extend the original conclusions about Arrokoth, and they nail down the distant object's origin story.
"Arrokoth has told us how planetesimals form, and therefore made a major advance in our understanding of planet formation," New Horizons Principal Investigator Alan Stern, a co-author of all three new studies, told Space.com. "It is very decisive."
Two formation possibilities
Arrokoth's "cloud collapse" birth was far from a given. There's a prominent competing theory about planetesimal formation called "hierarchical accretion," which posits that the planetary building blocks are built up over time by high-speed collisions of objects from various locales.
Hierarchical accretion is actually the more venerable idea, dating back 70 years or so, Stern said, whereas cloud collapse (also known as "pebble accretion") was devised just at the beginning of this century.
There has been considerable debate between advocates of the two theories over the past two decades. But the three new papers show convincingly how Arrokoth was born, said Stern, who's based at the Southwest Research Institute (SwRI) in Boulder, Colorado.
"With Arrokoth, there are half a dozen lines of evidence that all point to cloud collapse, and you can't explain them with hierarchical accretion," he said.
Perhaps the strongest such evidence is provided by the object's shape. As discussed above, the relatively intact nature of the two lobes implies a very gentle collision, not a high-speed wreck.
In one of the new papers, researchers led by William McKinnon of Washington University in St. Louis performed detailed modeling of that long-ago merger. These simulations indicated that the two lobes likely formed from the same cloud of material, became a co-orbiting binary object and finally came together in a slow and non-destructive fashion. Indeed, the models peg the collision's maximum speed at around 9 mph (15 km/h), and it may have been considerably less than that.
This scenario is further bolstered by the geometric alignment of Arrokoth's two lobes, which strongly suggests that the duo orbited the same center of mass (when they were separate, free-flying objects), the scientists wrote.
Another of the new studies, led by SwRI's John Spencer, digs into the geology and geophysics of Arrokoth, which also point to a cloud-collapse origin. For example, the density of craters on Arrokoth indicates that the object is ancient, with a surface at least 4 billion years old. And, like McKinnon and his team, Spencer et al. found a close alignment of the two lobes, whose poles and equators are geometrically in synch. (They also determined, among other interesting finds, that the lobes aren't quite as flattened as originally believed.)
In the third paper, Will Grundy of Lowell Observatory and Northern Arizona University and his colleagues investigated Arrokoth's composition. They found that the object (which was previously known officially as 2014 MU69, and unofficially as Ultima Thule) is cold and extremely red, with methanol ice and carbon-containing organic materials on its mostly homogeneous surface. These complex organics are probably responsible for the object's red hue, the researchers wrote. (New Horizons didn't spot any water ice, but this material may still be on Arrokoth, lurking out of sight.)
This overall picture is also consistent with a cloud-collapse birth, mission team members said. For instance, the compositional similarity of the two lobes suggests they formed from the same starter material.
Born from a cloud
Stern and his fellow New Horizons team members aren't the only ones who find all this evidence convincing.
"To me, the observations of Arrokoth show that planetesimals form from collapsing clouds of pebbles," Anders Johansen, an astronomy professor at Lund University in Sweden, told Space.com via email.
"The mechanism that gathers the pebbles into such clouds to begin with is called the streaming instability," added Johansen, who was not involved in the three new studies. "It is amazing to see how Arrokoth resembles the planetesimals that we form in computer simulations of the streaming instability. So, I would say that these observations of Arrokoth provide a window to look into how planetesimals formed in the solar system more than 4.5 billion years ago."
This window could let in a great deal of light, according to Stern. He cited as a comparison the vigorous debate about the universe's origins that stretched from the 1940s through the mid-1960s. Some researchers argued for the "steady state" theory, others pushed the "constant creation" model and a third group backed the Big Bang, Stern said.
"They battled it out and battled it out and battled it out; nobody could tell who was right. And then, [Arno] Penzias and [Robert] Wilson stumbled onto the cosmic microwave background [in 1964] and settled it," he said. "Two of the three went into the dustbin, and the Big Bang has been paradigm ever since. This is equivalent in planetary science."
Johansen as well sees extension of the newly announced results beyond just Arrokoth's birth.
"In the 'pebble accretion' theory, the formation of planets happens as the largest planetesimals continue to grow by accreting pebbles," he said. "So, the fact that Arrokoth formed from a pebble cloud could mean that the solid cores of the giant planets — Jupiter, Saturn, Uranus and Neptune — formed from large planetesimals that continued to accrete pebbles. And maybe even the terrestrial planets in the solar system owe their existence to pebble accretion."
There's one notable caveat to such talk of broader applications: Arrokoth must be representative of most if not all planetesimals, and not some one-off weirdo. But this condition is likely to be met. After all, Arrokoth is similar to other Kuiper Belt objects in size, color and reflectivity, Stern said. And the odds are slim that New Horizons would randomly sample an atypical cosmic body.
Still going strong
New Horizons launched in January 2006 to give humanity its first up-close looks at Pluto, which had remained mysterious since its 1930 discovery. The probe aced that primary mission, returning imagery of the dwarf planet that revealed it to be a stunningly complex and diverse world.
The Arrokoth encounter is the centerpiece of New Horizons' current extended mission, which runs through 2021. But the probe may well have another flyby in its future.
New Horizons remains in great shape and has sufficient fuel to conduct another encounter, if the right object is found (and NASA approves another mission extension), Stern said. And, this summer, the mission team will begin a concerted search for potential future flyby targets, using the Subaru telescope in Hawaii and the Magellan and Gemini South telescopes in Chile.
There's no guarantee that this search will be successful, Stern stressed.
"It took us four years to find Arrokoth, so I'm not promising anything," he said. "But if you don't swing the bat, you can't hit the ball."
- One year ago, NASA's New Horizons made the most distant flyby in space history
- Long after historic flybys, NASA's New Horizons is still pioneering science in the Kuiper Belt
- We just flew past a Kuiper Belt object. Here's why we should do it again.
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. | 0.907374 | 3.886174 |
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