Posted on by Tammy Plotner

Mathematics Explain Dynamics of Superfluid

A 2001 photo from the space shuttle shows a phenomenon called von Karman vortices in clouds downwind from Rashiri Island in the northern Sea of Japan. The vortices are similar to those that form in superfluids. Credit: NASA

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At nearly the coldest temperature possible – mercury (with the aid of liquid helium) – forms a state called superconductivity. At the extreme, electrons flow unencumbered through what is known as a superfluid. But the hows and whys of superfluid behavior defied explanation. Until now…

When taken to within a few degrees of absolute zero on the Kelvin scale (minus 273 Celsius or minus 460 Fahrenheit), liquid helium-4 turns into the remarkable superfluid state. It swirls, it curls, and it’s lack of body has been baffling scientists for nearly a century. Now a team led by a University of Washington physicist, using the most powerful supercomputer available for open science, has cooked up a theoretical picture which explains the real-time behavior of superfluid. Just who is the responsible party here? Try subatomic particles called fermions.

Femions are a much a part of the natural equation as electrons, protons and neutrons… just as superfluids are part of neutron stars. Rotating between one and 1,000 times a second, neutron stars – or pulsars – superfluid surface acts much differently than its counterpart here on Earth. As the speed increases, it forms a series of small vortices which group in a triangular pattern… which in turn forms a braid within the superfluid structure. “When you reach the correct speed, you’ll create one vortex in the middle,” Bulgac said. “And as you increase the speed, you will increase the number of vortices. But it always occurs in steps.”

Can science recreate it? Yes. Laboratory models utilizing a vacuum chamber and a laser beam to create a high-intensity electrical field have managed to chill a small sample, perhaps 1 million atoms, to temperatures near absolute zero. Then a “laser spoon” is employed to stir the superfluid fast enough to create vortices.

“In trying to understand the odd behavior, scientists have attempted to devise descriptive equations, such as ones they might use to describe the swirling action in a cup of coffee as it is stirred.” Bulgac said. “But to describe the action in a superfluid made of fermions, a nearly limitless number of equations is needed. Each describes what happens if just one variable – such as velocity, temperature or density – is changed. Because the variables are linked, if one changes others will change as well.”

One of the major challenges in formulating a mathematical hypothesis is the amount of computing power it would take to work through a problem with a number of variable changes that reached 1 trillion or more. So how did they do it? The team used the JaguarPF computer at Oak Ridge National Laboratory in Tennessee, one of the largest supercomputers in the world, for the equivalent of 70 million hours, which would require almost 8,000 years on a single-core personal computer (JaguarPF has nearly a quarter-million cores). Just try to cool that!

“This tells you the complexity of these calculations and how difficult this is,” Bulgac said. To make matters even more complex, the faster the superfluid is stirred causes it to lose its properties – but not as fast as hypothesized. “The work means that researchers can ‘to some extent’ study the properties of a neutron star using computer simulations.” Bulgac said. .”It also opens new directions of research in cold-atom physics.”

And more homework on our part.

Original Story Source: University of Washington.

Posted on by Nancy Atkinson

New VLT Survey Telescope Opens Wide Eyes to the Universe

The first released VST image shows the spectacular star-forming region Messier 17, also known as the Omega Nebula or the Swan Nebula. Credit: ESO/INAF-VST/OmegaCAM. Acknowledgement: OmegaCen/Astro-WISE/Kapteyn Institute.

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There’s a new telescope at the Paranal Observatory in Chile and what big eyes it has! The VLT Survey Telescope (VST) is a wide-field survey telescope with a field of view twice as broad as the full Moon, enabling new, spectacular views of the cosmos. It is the largest telescope in the world designed to exclusively survey the sky in visible light. Over the next few years the VST and its camera OmegaCAM will make several very detailed surveys of the southern sky.

The first image released from these new eyes on the Universe is a spectacular view star-forming region Messier 17, also known as the Omega Nebula or the Swan Nebula, shown above. The VST field of view is so large that the entire nebula, including its fainter outer parts, is captured — and retains its superb sharpness across the entire image.

This new image may be the best portrait of the globular star cluster Omega Centauri ever made. Omega Centauri, in the constellation of Centaurus (The Centaur), is the largest globular cluster in the sky, but the very wide field of view of VST and its powerful camera OmegaCAM can encompass even the faint outer regions of this spectacular object. Credit: ESO/INAF-VST/OmegaCAM. Acknowledgement: A. Grado/INAF-Capodimonte Observatory

The second image is the globular star cluster Omega Centauri. This is the largest globular cluster in the sky, but the very wide field of view of VST and OmegaCAM allows even the faint outer regions to be seen clearly. This view includes about 300,000 stars.

Here’s a look at the new telescope:

The VLT Survey Telescope (VST) is the latest telescope to be added to ESO’s Paranal Observatory in the Atacama Desert of northern Chile. Credit: ESO/G. Lombardi

Below is a timelapse sequences of the VST enclosure at night:

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For more info and images see this ESO webpage.

Posted on by Nancy Atkinson

Guest Post: Newly Born: the Science of Astronomy

Astronomical equipment from the ages, on display at the Adler Planetarium. Image: Nancy Atkinson

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Editor’s Note: Astronomy journalist Govert Schilling has written a book that looks at the 100 most important discoveries since the invention of the telescope 400 years ago, called “Atlas of Astronomical Discoveries.” In Schilling’s distinct style, he takes the reader on an adventure through both space and time. Schilling has written this guest post for Universe Today:

Astronomy is a newborn science.

Yes, I know astronomers like to say it’s the oldest science in the world. In a sense, our distant ancestors who wondered about the lights and motions in the night sky were the first practitioners.

But look at it this way: until four centuries ago, we all had the same opportunities in the field. Or lack thereof. Two eyes and a brain – that has been the main instrumentation in astronomy for thousands of years. Not much, really.

Little wonder then that astronomy was in a pretty primitive state at the start of the seventeenth century. Granted, scientists had come to realize that the Sun occupied the center of the solar system, rather than the Earth. They had seen the occasional comet and Stella Nova, and they knew about the slow change in the orientation of the Earth’s axis.

But no one knew the distances to the planets, let alone to the stars. No one had the slightest clue about the true nature of the Sun or the Moon. Meteors were a mystery; planetary satellites and rings were unheard of, and to many, the Milky Way was just that – a cosmic river of milky clouds.

The Milky Way as seen near the Very Large Telescope in the Atacama Desert. Credit: ESO/Y. Beletsky

More importantly, no one realized that the Universe is in a constant state of flux, albeit at an extremely slow pace. That stars were once born and will eventually die. That the planets in our solar system are built from the ashes of an earlier generation of stars. That the Universe hasn’t always been there.

Most of the astronomical knowledge that we take for granted these days, was completely unknown four centuries ago. That’s why I say astronomy is a newborn science.

And the telescope was its midwife.

A replica of Galileo's telescope.

The invention of the telescope, probably around 1600 in the Netherlands, ushered in a whole new scientific era. It paved the way for hundreds of revolutionary discoveries and revealing insights. It brought astronomy to where it is now.

On the occasion of the International Year of Astronomy (2009), I decided to devote a book to the hundred most important astronomical discoveries since the invention of the telescope. Recently translated into English as Atlas of Astronomical Discoveries (Springer, 2011), it is a lavishly illustrated and beautifully designed history tour of the grandest science of all, chockfull with surprising details and personal anecdotes.

What I realized when writing the book was that the young science of astronomy went through a number of very distinct stages, just like a human being goes through childhood, puberty and adolescence before reaching full maturity.

In the seventeenth century, astronomers were like children in a newly opened candy store. Wherever they aimed their rather primitive telescopes, they beheld new discoveries, but this embarrassment of riches was also an undirected endeavour.

During the eighteenth century, the search became more systematic, with diligent observers surveying the skies and taking stock of everything that the telescope brought into view. This was no longer a first reconnaissance, but a real exploratory phase.

Then came the nineteenth century, with the advent of photography and spectroscopy, and the discovery of mysterious cosmic denizens like spiral nebulae, white dwarfs, and interstellar matter. Nature was trying to tell us something profound, and astronomy stood on the threshold of major theoretical breakthroughs that would explain this surprising variety of phenomena.

Finally, the twentieth century saw the emergence of an interconnected, all-encompassing view of cosmic evolution. We discovered the energy source of stars, the true nature of galaxies, the expansion of the Universe, and the humble position of our home planet, both in space and in time. Moreover, we finally understood that the atoms in our bodies were forged in the nuclear ovens of distant suns. That we are truly one with the Universe.

So has astronomy grown into a mature science? With the current generation of giant telescopes, the full exploration of the electromagnetic spectrum, and the advent of space science and computer technology, it’s tempting to answer this question with a resounding ‘yes’. Then again, ninety-six percent of the cosmos consists of mysterious dark matter and dark energy; we have no clue about the origin of our Universe, and no one knows whether or not life – let alone intelligence – is rare or abundant.

Personally, I feel that astronomy is still in its early years. And that’s exactly why it fires the imagination of so many people. The questions that astronomers try to answer are the same questions that a ten-year old would ask. The answers may be difficult, but the questions are simple, because the science is young. What’s it made of? How did it all start? Are we alone?

Certainly, I’d love to see a 2411 edition of Atlas of Astronomical Discoveries, highlighting the hundred most important discoveries and breakthroughs that astronomers made in the 21st, 22nd, 23rd and 24th century. But I’m afraid I wouldn’t understand most of the issues that would be described.

Frankly, I’m glad to live during the youth of my favorite science. After all, I’ve always been fond of the curiosity, energy, creativity and the sheer sense of wonder of children.

Please, astronomy, don’t grow up too soon.

Govert Schilling is an internationally acclaimed astronomy writer in the Netherlands. He is a contributing editor of Sky & Telescope, and his articles have appeared in Science, New Scientist and BBC Sky at Night Magazine. He wrote over fifty books on a wide variety of astronomical topics, some of which have been translated into English, including “Evolving Cosmos; Flash! The Hunt for the Biggest Explosions in the Universe,” TThe Hunt for Planet X,” and “Atlas of Astronomical Discoveries.” In 2007, the International Astronomical Union named asteroid (10986) Govert after him.

Posted on by VirtualAstro

Supernova Discovered in M51 The Whirlpool Galaxy

M51 Hubble Remix

A new supernova (exploding star) has been discovered in the famous Whirlpool Galaxy, M51.

M51, The Whirlpool galaxy is a galaxy found in the constellation of Canes Venatici, very near the star Alkaid in the handle of the saucepan asterism of the big dipper. Easily found with binoculars or a small telescope.

The discovery was made on June 2nd by French astronomers and the supernova is reported to be around magnitude 14. More information (In French) can be found here or translated version here.

Image by BBC Sky at Night Presenter Pete Lawrence

The supernova will be quite tricky to spot visually and you may need a good sized dobsonian or similar telescope to spot it, but it will be a easy target for those interested in astro imaging.

The whirlpool galaxy was the first galaxy discovered with a spiral structure and is one of the most recognisable and famous objects in the sky.

Posted on by Tammy Plotner

Old Star Clusters Shed New Light on Starbirth

NGC 3603 - Credit: NASA, ESA, R. O'Connell (University of Virginia), F. Paresce (National Institute for Astrophysics, Bologna, Italy), E. Young (Universities Space Research Association/Ames Research Center), the WFC3 Science Oversight Committee, and the Hubble Heritage Team (STScI/AURA)

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Hovering about the galactic plane and locked in the embrace of a spiral galaxy’s arms, open star clusters usually contain up to a few hundred members and generally span around thirty light years across. Most are young, up to a few tens of millions of years old – with a few rare exceptions as old as a few billion years. We understand that over time the members of a galactic cluster slowly drift apart to form loose associations. But what we don’t understand is exactly how their stars formed.

“The net effect of this is that their stars eventually become redistributed throughout the Galaxy,” said Nathan Leigh, a PhD student at McMaster University and lead author for a study being presented this week at the CASCA 2011 meeting in Ontario, Canada. “This is how we think most of the stars in the Milky Way came to be found in their currently observed locations.”

One of the reasons we’re not able to probe deeply into the construction and evolution of galactic clusters is because they are typically hidden by a dense veil of gas and dust. Beautiful to look at… But nearly impossible to cut through in visible light. This means we can’t directly observe the process of starbirth. To help understand this process, astronomers have combined their observations of star clusters so old they date back to the beginning of the Universe itself . And, thanks to modern computing, they are also able to generate state-of-the-art simulations for stellar evolution.

“Unfortunately, most star clusters take so long to dissolve that we cannot actually see it happening. But we now understand how this process occurs, and we can look for its signatures by examining the current appearances of clusters,” said Nathan Leigh. “We have gone about this by matching up the clusters we make with our simulations to the ones we actually observe. This tells us about the conditions at the time of their formation.”

These simulations have given Leigh and collaborators the stimulus they needed to re-trace the histories of real star clusters, giving us new clues about formation. To complete their studies, they relied upon highly sophisticated observations recently taken with the Hubble Space Telescope.

“Remarkably, we are finding that all star clusters more or less share a common history, extending all the way back to their births,” said Leigh. “This came as a big surprise to us since it suggests that the problem could be much simpler than we originally thought. Our understanding of not only how stars form, but also the history of our Galaxy, just took a much bigger step forward than we were expecting.”

Source: Canadian Astronomical Society.

Posted on by Tammy Plotner

MOST… Cutting To The Heart Of A Wolf-Rayet Star

M1-67 is the youngest wind-nebula around a Wolf-Rayet star, called WR124, in our Galaxy. Credit: ESO

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In 1867, astronomers using the 40 cm Foucault telescope at the Paris Observatory, discovered three stars in the constellation Cygnus (now designated HD191765, HD192103 and HD192641), that displayed broad emission bands on an otherwise continuous spectrum. The astronomers’ names were Charles Wolf and Georges Rayet, and thus this category of stars became named Wolf–Rayet (WR) stars. Now using the Canadian MOST microsatellite, a team of researchers from the Universite de Montreal and the Centre de Recherche en Astrophysique du Quebec have made a stunning observation. They probed into the depth of the atmospheric eclipses in the Wolf-Rayet star, CV Serpentis, and observed a never before seen change of mass-loss rate.

Thanks to the service of MOST – Canada’s first space telescope and its high precision photometry – the team has observed significant changes in the depth of the atmospheric eclipses in the 30-day binary WR+O system. The equipment is aboard a suitcase-sized microsatellite (65 x 65 x 30 cm) which was launched in 2003 from a former ICBM in northern Russia. It is on a low-Earth polar orbit and has long outlived its original estimated life expectancy, offering Canadian astronomers almost eight years (and still counting) of ultra-high quality space-based data. Now this data gives us a huge insight into the heart of Wolf-Rayet stars.

Intrinsically luminous, WR stars can be massive or mid-sized, but the most interesting stage is arguably the last 10% in the lifetime of the star, when hydrogen fuel is used up and the star survives by much hotter He-burning. Towards the end of this phase, the copious supply of carbon atoms head for the stellar surface and are ejected in the form of stellar winds. WR stars in this stage are known as WC stars… and their production of carbon dust is one of the greatest mysteries of the Cosmos. These amorphous dust grains range in size from a few to millions of atoms and astronomers hypothesize their formation may requires high pressure and less than high temperatures.

“One key case is undoubtedly the sporadic dust-producing WC star in CV Ser. MOST was recently used to monitor CV Ser twice (2009 and 2010), revealing remarkable changes in the depths of the atmospheric eclipse that occurs every time the hot companion’s light is absorbed as it passes through the inner dense WC wind.” says the researchers. “The remarkable, unprecedented 70% change in the WC mass-loss rate might be connected to dust formation.”

And all thanks to the MOST tiny little satellite imaginable…

Original Story Source: AstroNews and excerpt from Wikipedia.

Posted on by Tammy Plotner

Coming To A Theatre Near You… Extreme Neutron Stars!

Artist's Conception of a Neutron Star Courtesy of NASA

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They came into existence violently… Born at the death of a massive star. They are composed almost entirely of neutrons, barren of electrical charge and with a slightly larger mass than protons. They are quantum degenerates with an average density typically more than one billion tons per teaspoonful – a state which can never be created here on Earth. And they are absolutely perfect for study of how matter and exotic particles behave under extreme conditions. We welcome the extreme neutron star…

In 1934 Walter Baade and Fritz Zwicky proposed the existence of the neutron star, only a year after the discovery of the neutron by Sir James Chadwick. But it took another 30 years before the first neutron star was actually observed. Up until now, neutron stars have had their mass accurately measured to about 1.4 times that of Sol. Now a group of astronomers using the Green Bank Radio Telescope found a neutron star that has a mass of nearly twice that of the Sun. How can they make estimates so precise? Because the extreme neutron star in question is actually a pulsar – PSR J1614-2230. With heartbeat-like precision, PSR J1614-2230 sends out a radio signal each time it spins on its axis at 317 times per second.

According to the team; “What makes this discovery so remarkable is that the existence of a very massive neutron star allows astrophysicists to rule out a wide variety of theoretical models that claim that the neutron star could be composed of exotic subatomic particles such as hyperons or condensates of kaons.”

The presence of this extreme star poses new questions about its origin… and its nearby white dwarf companion. Did it become so extreme from pulling material from its binary neighbor – or did it simply become that way through natural causes? According to Professor Lorne Nelson (Bishop’s University) and his colleagues at MIT, Oxford, and UCSB, the neutron star was likely spun up to become a fast-rotating (millisecond) pulsar as a result of the neutron star having cannibalized its stellar companion many millions of years ago, leaving behind a dead core composed mostly of carbon and oxygen. According to Nelson, “Although it is common to find a high fraction of stars in binary systems, it is rare for them to be close enough so that one star can strip off mass from its companion star. But when this happens, it is spectacular.”

Through the use of theoretical models, the team hopes to gain insight as to how binary systems evolve over the entire lifetime of the Universe. With today’s extreme super-computing powers, Nelson and his team members were able to calculate the evolution of more than 40,000 plausible starting cases for the binary and determine which ones were relevant. As they describe at this week’s CASCA meeting in Ontario, Canada, they found many instances where the neutron star could evolve higher in mass at the expense of its companion, but as Nelson says, “It isn’t easy for Nature to make such high-mass neutron stars, and this probably explains why they are so rare.”

Original story source at Physorg.com.

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Posted on by Tammy Plotner

Globular Clusters Are Real Oddballs

M80 Image Credit: NASA, The Hubble Heritage Team, STScI, AURA

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Hanging onto the outskirts of our Milky Way galaxy like cockle burs on a shaggy dog’s coat, globular clusters contain over hundreds of thousands of stars. Estimated to be up to ten billion years old, these spherical stellar seed pods are gravitationally bound together and tend to be more dense towards their cores. We’ve long known all the stars contained within a globular cluster to be about the same age and the individual members most likely formed at the same time as the parent galaxy – but what we weren’t expecting was change.

“We thought we understood these clusters very well”, says Dr. Alison Sills, Associate Professor of Physics & Astronomy. She is presenting new findings at this week’s CASCA 2011 meeting in Ontario, Canada. “We taught our students that all the stars in these clusters were formed at the same time, from one giant cloud of gas. And since that time, the individual stars may have evolved and died, but no new stars were born in the cluster.”

In 1953, astronomer Allan Sandage was performing photometry of the stars in the globular cluster M3 when he made an incredible discovery – blue stragglers. No, it’s not a down-his-luck musician waiting for a coin in his instrument case… but a main sequence star more luminous and more blue than stars at the main sequence turn-off point for the cluster. They shouldn’t belong where they are, but with masses two to three times that of the rest of the main sequence cluster stars, blue stragglers seem to be exceptions to the rule. Maybe they are a product of interaction… grappling together… pulling material from one another… and eventually merging.

Image of NGC 6397 taken by the Hubble Space Telescope, with evidence of a number of blue stragglers.

“Astronomers expect that the stars get too close to each other because of the complicated dance that stars perform in these dense clusters, where thousands of stars are packed into a relatively small space, and each star is moving through this cluster under the influence of the gravity of all the other stars. Somewhat like a traffic system with no stop lights, there are a lot of close encounters and collisions,” explains Sills.

By taking a closer look at globular clusters, the Hubble Space Telescope has given us evidence for two generations of star formation. The first is our accepted rule, but the second generation isn’t like anything else found in our Galaxy. Instead of being created from an earlier generation of expended stars, the second generation in globular clusters appears to have formed from material sloughed off by the first generation of stars. An enigma? You bet.

“Studying the normal stars in clusters was instrumental in allowing astronomers to figure out how stars lived and died”, says Dr. Sills, “but now we can look even further back, to when they were born, by using the oddballs. It pays off to pay attention to the unusual individuals in any population. You never know what they’ll be able to tell you.”

At the CASCA conference, Dr. Sills is presenting her work – a link between these two unusual forms of globular clusters. Blue stragglers and the second generation of stars would appear to have identical properties, including where they are concentrated in the cluster, and that both are.. well.. a little more “blue” than we would expect. She is investigating how the close encounters and collisions could affect the formation of this strange second generation and link the two phenomena we see in these complicated systems.

Real oddballs…

Original story soucre at Physorg.com.

Posted on by Tammy Plotner

Dead Galaxy? Don’t Think So.

University of Michigan astronomers examined old galaxies and were surprised to discover that they are still making new stars. The results provide insights into how galaxies evolve with time.

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There was a time when most astronomers concluded that elliptical galaxies were a lot like their globular clusters – full of similarly evolved and aged stars. But not anymore. Thanks to the resolving power of the Hubble Space Telescope, a team of researchers from the University of Michigan were able to peer into the heart of Messier 105 and pick out several young stars and clusters. Apparently, “The reports of my death have been greatly exaggerated…”

U-M research fellow Alyson Ford and astronomy professor Joel Bregman are scheduled to present their findings May 31 at a meeting of the Canadian Astronomical Society in London, Ontario. Using the Wide Field Camera 3 on the Hubble Space Telescope, they saw individual young stars and star clusters in four galaxies that are about 40 million light-years away. One light-year is about 5.9 trillion miles.

“Scientists thought these were dead galaxies that had finished making stars a long time ago,” Ford said. “But we’ve shown that they are still alive and are forming stars at a fairly low level.”

We’re all aware of differing galaxy structures, from grand design spirals to disturbed irregulars. However, perhaps one of the most common is the elliptical. Ranging in flat form to nearly spherical, these smooth customers can contain anywhere from hundreds of millions to over one trillion stars – and most of them are believed to be the offspring of galaxy collision. Most elliptical galaxies are composed of older, low-mass stars, with a sparse interstellar medium and minimal star formation activity. Making up somewhere between 10 to 15% of known galaxy population, they are surrounded by globular clusters and usually make their home at the center of galaxy clusters. But what elliptical galaxies aren’t known for is star formation.

“Astronomers previously studied star formation by looking at all of the light from an elliptical galaxy at once, because we usually can’t see individual stars. Our trick is to make sensitive ultraviolet images with the Hubble Space Telescope, which allows us to see individual stars.” said Ford. “”We were confused by some of the colors of objects in our images until we realized that they must be star clusters, so most of the star formation happens in associations.”

The eureka moment came when the team turned the Hubble towards a galaxy most of us have observed on a personal level – M105. Located 38 million light years away in the constellation of Leo and part of the M96 Galaxy Group, this rather ordinary looking elliptical galaxy is one of the brightest to observe. Although there wasn’t any reason to believe star formation was in progress, Ford and Bregman saw a few bright, very blue stars, resembling a single star 10 to 20 times the mass of the Sun. In addition, they also observed objects that aren’t blue enough to be single stars, but instead are clusters of many stars. When accounting for these clusters, stars are forming in Messier 105 at an average rate of one Sun every 10,000 years, Ford and Bregman concluded. “This is not just a burst of star formation but a continuous process,” Ford said.

New stars from a dead galaxy? Maybe it’s a zombie. And it’s not the first time the Hubble has looked its way, either. Investigations of the central region of M105 have revealed that this galaxy contains a massive central object of about 50 million solar masses – a supermassive black hole. Of course, this new evidence creates more questions than it answers and high among the ranks is the origin of the gas that forms the stars.

“We’re at the beginning of a new line of research, which is very exciting, but at times confusing,” Bregman said. “We hope to follow up this discovery with new observations that will really give us insight into the process of star formation in these ‘dead’ galaxies.”

Dead… But maybe not so dead, after all.

Original story source Physorg.com.

Posted on by Jon Voisey

Exoplanet Kepler-7b Unexpectedly Reflective

Artist concept of Kepler in space. Credit: NASA/JPL

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Early on in the hunt for extra solar planets, the main method for discovering planets was the radial velocity method in which astronomers would search for the tug of planets on their parent stars. With the launch of NASA’s Kepler mission, the transit method is moving into the spotlight, the radial velocity technique provided an early bias in the detection of planets since it worked most easily at finding massive planets in tight orbits. Such planets are referred to as hot Jupiters. Currently, more than 30 of this class of exoplanet have had the properties of their emission explored, allowing astronomers to build a picture of the atmospheres of such planets. However, one of the new hot Jupiters discovered by the Kepler mission doesn’t fit the picture.

The consensus on these planets is that they are expected to be rather dark. Infrared observations from Spitzer have shown that these planets emit far more heat than they absorb directly in the infrared forcing astronomers to conclude that visible light and other wavelengths are absorbed and reemitted in the infrared, producing the excess heat and giving rise to equilibrium temperatures over 1,000 K. Since the visible light is so readily absorbed, the planets would be rather dull when compared to their namesake, Jupiter.

The reflectivity of an object is known as its albedo. It is measured as a percentage where 0 would be no reflected light, and 1 would be perfect reflection. Charcoal has an albedo of 0.04 while fresh snow has an albedo of 0.9. The theoretical models of hot Jupiters place the albedo at or below 0.3, which is similar to Earth’s. Jupiter’s albedo is 0.5 due to clouds of ammonia and water ice in the upper atmosphere. So far, astronomers have placed upper limits on their albedo. Eight of them confirm this prediction, but three of them seem to be more reflective.

In 2002, it was reported that the albedo for υAnd b was as high as 0.42. This year, astronomers have placed constraints on two more systems. For HD189733 b, astronomers found that this planet actually reflected more light than it absorbed. For Kepler-7b, an albedo of 0.38 has been reported.

Revisiting this for the latter case, a new paper, slated for publication in an upcoming issue of the Astrophysical Journal, a team of astronomers led by Brice-Olivier Demory of the Massachusetts Institute of Technology confirms that Kepler-7b has an albedo that breaks the expected limit of 0.3 set by theoretical models. However, the new research does not find it to be as high as the earlier study. Instead, they revise the albedo from 0.38 to 0.32.

To explain this additional flux, the team proposes two models. They suggest that Kepler-7b may be similar to Jupiter in that it may contain high altitude clouds of some sort. Due to the proximity to its parent star, it would not be ice crystals and thus, would not reach as high of an albedo as Jupiter, but preventing the incoming light from reaching lower layers where it could be more effectively trapped would help to increase the overall albedo.

Another solution is that the planet may be lacking the molecules most responsible for absorption such as sodium, potassium, titanium monoxide and vanadium monoxide. Given the temperature of the planet, it is unlikely that the molecular components would be present in the first place since they would be broken apart from the heat. This would mean that the planet would have to have 10 to 100 times less sodium and potassium than the Sun, whose chemical composition is the basis for models since our star’s composition is generally representative of stars around which planets have been discovered and presumably, the cloud from which it formed and would also form into planets.

Presently there is no way for astronomers to determine which possibility is correct. Since astronomers are slowly becoming able to retrieve spectra of extrasolar planets, it may be possible in the future for them to test chemical compositions. Failing that, astronomers will need to examine the albedo of more exoplanets and determine just how common such reflective hot Jupiters are. If the number remains low, the plausibility of metal deficient planets remains high. However, if the numbers start creeping up, it will prompt a revision to models of such planets and their atmospheres with greater emphasis on clouds and atmospheric haze.