Posted on by Shannon Hall

New Technique Could Measure Exoplanet Atmospheric Pressure, an Indicator of Habitability

Artistic representations of the only known planets around other stars (exoplanets) with any possibility to support life as we know it. The authors of this study wanted to know how people react to the discovery of alien life and potentially habitable planets. Credit: Planetary Habitability Laboratory, University of Puerto Rico, Arecibo.

Measuring the atmospheric pressure of a distant exoplanet may seem like a daunting task but astronomers at the University of Washington have now developed a new technique to do just that.

When exoplanet discoveries first started rolling in, astronomers laid emphasis in finding planets within the habitable zone — the band around a star where water neither freezes nor boils. But characterizing the environment and habitability of an exoplanet doesn’t depend on the planet’s surface temperature alone.

Atmospheric pressure is just as important in gauging whether or not the surface of an exoplanet may likely hold liquid water. Anyone familiar with camping at high-altitude should have a good understanding of how pressure affects water’s boiling point.

The method developed by Amit Misra, a PhD candidate, involves isolating “dimers” — bonded pairs of molecules that tend to form at high pressures and densities in a planet’s atmosphere — not to be confused with “monomers,” which are simply free-floating molecules. While there are many types of dimers, the research team focused exclusively on oxygen molecules, which are temporarily bound to each other through hydrogen bonding.

We may indirectly detect dimers in an exoplanet’s atmosphere when the exoplanet transits in front of its host star. As the star’s light passes through a thin layer of the planet’s atmosphere the dimers absorb certain wavelengths of it. Once the starlight reaches Earth it’s imprinted with the chemical fingerprints of the dimers.

Dimers absorb light in a distinctive pattern, which typically has four peaks due to the rotational motion of the molecules. But the amount of absorption may change depending on the atmospheric pressure and density. This difference is much more pronounced in dimers than in monomers, allowing astronomers to gain additional information about the atmospheric pressure based on the ratio of these two signatures.

While water dimers were detected in the Earth’s atmosphere as early as last year, powerful telescopes soon to come online may enable astronomers to use this method in observing distant exoplanets. The team analyzed the likelihood of using the James Webb Space Telescope to make such a detection and found it challenging but possible.

Detecting dimers in an exoplanet’s atmosphere would not only help us evaluate the atmospheric pressure, and therefore the state of water on the surface, but other biosignature markers as well. Oxygen is directly tied to photosynthesis, and will most likely not be abundant in an exoplanet’s atmosphere unless it is regularly produced by algae or other plants.

“So if we find a good target planet, and you could detect these dimer molecules — which might be possible within the next 10 to 15 years — that would not only tell you something about pressure, but actually tell you that there’s life on that planet,” said Misra in a press release.

The paper has been published in the February issue of Astrobiology and is available for download here.

Posted on by David Dickinson

Nearby Brown Dwarf Captured in a Direct Image

A direct image of a brown dwarf companion (arrowed) taken at the Keck Observatory. (Credit: Crepp et al. 2014 APJ).

A recent find announced by astronomers may go a long ways towards understanding a crucial “missing link” between planets and stars.

The team, led by Friemann Assistant Professor of Physics at the University of Notre Dame’s Justin R. Crepp, recently released an image of a brown dwarf companion to a star 98 light years or 30 parsecs distant. This discovery marks the first time that a T-dwarf orbiting a Sun-like star with known radial velocity acceleration measurement has been directly imaged.

Located in the constellation Eridanus, the object weighs in at about 52 Jupiter masses, and orbits a 0.95 Sol mass star 51 Astronomical Units (AUs) distant once every 320-1900 years. Note that this wide discrepancy stems from the fact that even though we’ve been following the object for some 17 years since 1996, we’ve yet to ascertain whether we’ve caught it near apastron or periastron yet: we just haven’t been watching it long enough.

The T-dwarf, known as HD 19467 B, may become a benchmark in the study of sub-stellar mass objects that span the often murky bridge between true stars shining via nuclear fusion and ordinary high mass planets.

Brown dwarfs are classified as spectral classes M, L, T, and Y and are generally quoted as having a mass of between 13 to 80 Jupiters. Brown dwarfs utilize a portion of the proton-proton chain fusion reaction to create energy, known as deuterium burning. Low mass red dwarf stars have a mass range of 80 to 628 Jupiters or 0.75% to 60% the mass of our Sun. The Sun has just over 1,000 times Jupiter’s mass.

Researchers used data from the TaRgeting bENchmark-objects with Doppler Spectroscopy (TRENDS) high-contrast imaging survey, and backed it up with more precise measurements courtesy of the Keck observatory’s High-Resolution Echelle Spectrometer or HIRES instrument.

An artist's conception of a T-type brown dwarf. (Credit: Tyrogthekreeper under a Wikimedia Commons Attribution-Share Alike 3.0 Unported license).
An artist’s conception of a T-type brown dwarf. (Credit: Tyrogthekreeper under a Wikimedia Commons Attribution-Share Alike 3.0 Unported license).

TRENDS uses adaptive optics, which relies on precise flexing the telescope mirror several thousands of times a second to compensate for the blurring effects of the atmosphere. Brown dwarfs shine mainly in the infrared, and objects such as HD 19467 B are hard to discern due to their close proximity to their host star. In this particular instance, for example, HD 19467 B was over 10,000 times fainter than its primary star, and located only a little over an arc second away.

“This object is old and cold and will ultimately garner much attention as one of the most well-studied and scrutinized brown dwarfs detected to date,” Crepp said in a recent Keck observatory press release. “With continued follow-up observations, we can use it as a laboratory to test theoretical atmospheric models. Eventually we want to directly image and acquire the spectrum of Earth-like planets. Then, from the spectrum, we should be able to tell what the planet is made of, what its mass is, radius, age, etc… basically all of its relevant properties.

Discovery of an Earth-sized exoplanet orbiting in a star’s habitable zone is currently the “holy grail” of exoplanet science. Direct observation also allows us to pin down those key factors, as well as obtain a spectrum of an exoplanet, where detection techniques such as radial velocity analysis only allow us to peg an upper mass limit on the unseen companion object.

This also means that several exoplanet candidates in the current tally of 1074 known worlds beyond our solar system also push into the lower end of the mass limit for substellar objects, and may in fact be low mass brown dwarfs as well.

Another key player in the discovery was the Near-Infrared Camera (second generation) or NIRC2. This camera works in concert with the adaptive optics system on the Keck II telescope to achieve images in the near infrared with a better resolution than Hubble at optical wavelengths, perfect for brown dwarf hunting. NIRC2 is most well known for its analysis of stellar regions near the supermassive black hole at the core of our galaxy, and has obtained some outstanding images of objects in our solar system as well.

The hexagonal primary mirror of the Keck II telescope. (Credit: SiOwl. A Wikimedia Commons image under a Creative Commons Attribution 3.0 Unported liscense).
The hexagonal primary mirror of the Keck II telescope. (Credit: SiOwl. A Wikimedia Commons image under a Creative Commons Attribution 3.0 Unported license).

What is the significance of the find? Free floating “rogue” brown dwarfs have been directly imaged before, such as the pair named WISE J104915.57-531906 which are 6.5 light years distant and were spotted last year. A lone 6.5 Jupiter mass exoplanet PSO J318.5-22 was also found last year by the PanSTARRS survey searching for brown dwarfs.

“This is the first directly imaged T-dwarf (very cold brown dwarf) for which we have dynamical information independent of its brightness and spectrum,” team lead researcher Justin Crepp told Universe Today.

Analysis of brown dwarfs is significant to exoplanet science as well.

“They serve as an essential link between our understanding of stars and planets,” Mr. Crepp said. “The colder, the better.”

And just as there has been a controversy over the past decade concerning “planethood” at the low end of the mass scale, we could easily see the debate applied to the higher end range, as objects are discovered that blur the line… perhaps, by the 23rd century, we’ll finally have a Star Trek-esque classifications scheme in place so that we can make statements such as “Captain, we’ve entered orbit around an M-class planet…”

Something that’s always been fascinating in terms of red and brown dwarf stars is also the possibility that a solitary brown dwarf closer to our solar system than Alpha Centauri could have thus far escaped detection. And no, Nibiru conspiracy theorists need not apply. Mr. Crepp notes that while possible, such an object is unlikely to have escaped detection by infrared surveys such as WISE. But what a discovery that’d be!

 

 

Posted on by Shannon Hall

Nearby Brown Dwarf System May Harbor Closest Exoplanet to Earth

WISE J104915.57-531906 as seen in NASA’s All-WISE survey (centered) and resolved to show its binary nature by the Gemini Observatory (inset). (Credit: NASA/JPL/Gemini Observatory/AURA/NSF).

In 2012 astronomers announced the discovery of an Earth-like planet circling our nearest neighbor, Alpha Centauri B, a mere 4.3 light-years away. But with such a discovery comes heated debate. A second group of astronomers was unable to confirm the exoplanet’s presence, keeping the argument unresolved to date.

But not to worry. One need only look 2.3 light-years further to see tantalizing — although yet unconfirmed — evidence of an exoplanet circling a pair of brown dwarfs: objects that aren’t massive enough to kick-off nuclear fusion in their cores. There just may be an exoplanet in the third closest system to our Sun.

Astronomers only discovered the system last year when the brown dwarfs were spotted in data from NASA’s Wide-field Infrared Explorer (WISE). Check out a past Universe Today article on the discovery here. They escaped detection for so long because they are located in the galactic plane, an area densely populated by stars, which are far brighter than the brown dwarfs.

Henri Boffin at the European Southern Observatory led a team of astronomers on a mission to learn more about these newly found dim neighbors.  The group used ESO’s Very Large Telescope (VLT) at Paranal in Chile to perform astrometry, a technique used to measure the position of the objects precisely. This crucial data would allow them to make a better estimate of the distance to the objects as well as their orbital period.

Boffin’s team was first able to constrain their masses, finding that one brown dwarf weighs in at 30 times the mass of Jupiter and the other weighs in at 50 times the mass of Jupiter. These light-weight objects orbit each other slowly, taking about 20 years.

But their orbits didn’t map out perfectly — there were slight disturbances, suggesting that something was tugging on these two brown dwarfs. The likely culprit? An exoplanet — at three times the weight of Jupiter — orbiting one or even both of the objects.

“The fact that we potentially found a planetary-mass companion around such a very nearby and binary system was a surprise,” Boffin told Universe Today.

The next step will be to monitor the system closely in order to verify the existence of a planetary-mass companion. With a full year’s worth of data it will be relatively straightforward to remove the signal caused by the exoplanet.

So far only eight exoplanets have been discovered around brown dwarfs. If confirmed, this planet will be the first to be discovered using astrometry.

“Once the companion is confirmed, this will be an ideal target to image using the upcoming SPHERE instrument on the VLT,” Boffin said. This instrument will allow astronomers to directly image planets close to their host star — a difficult technique worth the challenge as it reveals a wealth of information about the planet.

Once confirmed, this planet will stand as the closest exoplanet to the Sun, until the debate regarding Alpha Centauri Bb is resolved.

The paper has been accepted for publication as an Astronomy & Astrophysics Letter and is available for download here. For more information on Alpha Centauri Bb please read a paper available here and published in the Astrophysical Journal.

Posted on by Nancy Atkinson

Three New Exoplanets Found In a Star Cluster

This artist's impression shows one of the three newly discovered planets in the star cluster Messier 67. In this cluster the stars are all about the same age and composition as the Sun. ESO/L. Calcada.

So far, just a handful of planets have been found orbiting stars in star clusters – and actually, astronomers weren’t too surprised about that. Star clusters can be pretty harsh places with hordes of stars huddling close together, with strong radiation and harsh stellar winds stripping planet-forming materials from the region.

But it turns out that perhaps astronomers are beginning to think differently about star clusters as being a homey place for exoplanets.

Scientists using several different telescopes, including the HARPS planet hunter in Chile have now discovered three planets orbiting stars in the cluster Messier 67.

“These new results show that planets in open star clusters are about as common as they are around isolated stars — but they are not easy to detect,” said Luca Pasquini from ESO, who is a co-author of a new paper about these planets. “The new results are in contrast to earlier work that failed to find cluster planets, but agrees with some other more recent observations. We are continuing to observe this cluster to find how stars with and without planets differ in mass and chemical makeup.”

This wide-field image of the sky around the old open star cluster Messier 67 was created from images forming part of the Digitized Sky Survey 2. The cluster appears as a rich grouping of stars at the centre of the picture. Messier 67 contains stars that are all about the same age, and have the same chemical composition, as the Sun. Credit: ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin.
This wide-field image of the sky around the old open star cluster Messier 67 was created from images forming part of the Digitized Sky Survey 2. The cluster appears as a rich grouping of stars at the centre of the picture. Messier 67 contains stars that are all about the same age, and have the same chemical composition, as the Sun. Credit: ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin.

The astronomers are pretty excited about one of these planets in particular, as it orbits a star that is a rare solar twin — a star that is almost identical to our Sun in all respects. This is the first “solar twin” in a cluster that has been found to have a planet.

“In the Messier 67 star cluster the stars are all about the same age and composition as the Sun,” said Anna Brucalassi from the Max Planck Institute for Extraterrestrial Physics in Garching, Germany and lead author of the new paper on these planets. “This makes it a perfect laboratory to study how many planets form in such a crowded environment, and whether they form mostly around more massive or less massive stars.”

This cluster lies about 2,500 light-years away in the constellation of Cancer and contains about 500 stars. Many of the cluster stars are fainter than those normally targeted for exoplanet searches and trying to detect the weak signal from possible planets pushed HARPS to the limit, the team said.

They carefully monitored 88 selected stars in Messier 67 over a period of six years to look for the tiny telltale “wobbling” motions of the stars that reveal the presence of orbiting planets.

Three planets were discovered, two orbiting stars similar to the Sun and one orbiting a more massive and evolved red giant star. Two of the three planets are “hot Jupiters” — planets comparable to Jupiter in size, but much closer to their parent stars and therefore not in the habitable zone where liquid water could exist.

The first two planets both have about one third the mass of Jupiter and orbit their host stars in seven and five days respectively. The third planet takes 122 days to orbit its host and is more massive than Jupiter.

Star clusters come in two main types: open and globular. Open clusters are groups of stars that have formed together from a single cloud of gas and dust in the recent past, and are mainly found in the spiral arms of a galaxy like the Milky Way. Globular clusters are much bigger spherical collections of much older stars that orbit around the center of a galaxy. Despite careful searches, no planets have been found in a globular cluster and less than six in open clusters.

Another study last year from a team using the Kepler telescope found two planets in a dense open star cluster and the team stated that how planets can form in the hostile environments of dense star clusters is “not well understood, either observationally or theoretically.”

Exoplanets have been found in some amazing environments, and astronomers will continue to hunt for planets in these clusters of stars to try and learn more about how and why — and how many — exoplanets exist in star clusters.

ESOcast 62: Three planets found in star cluster from ESO Observatory on Vimeo.

Read the team’s paper.

Source: ESO

Posted on by Nancy Atkinson

The Most Common Exoplanets Might be “Mini-Neptunes”

Chart of Kepler planet candidates as of January 2014. Image Credit: NASA Ames

If the dataset from the Kepler mission is any indication, the most common type of exoplanets in our galaxy aren’t Earth-sized rocky worlds or hot Jupiters. In fact, the most common type of exoplanet isn’t one that we see in our own neighborhood at all.

“Perhaps the most remarkable discovery by Kepler is the amount of planets between the size of Earth to four times the size of Earth,” said Geoff Marcy, professor of astronomy at University of California, speaking at the American Astronomical Society meeting this week in Washington D.C. “This is a size range that dominates the planet inventory from Kepler and it a size range not represented in our own Solar System. We don’t know for sure what these planets are made of and we don’t know how they form.”

These “mini-Neptunes” as Marcy called them, represent a huge sample in the Kepler data; about 75% of the planets found by Kepler vary in size between the Earth and Neptune, and for four years since the Kepler data have been rolling in, scientists have been trying to understand these planets.

“There’s been an enormous amount of measurements and quantitative work by the NASA Ames Kepler team,” Marcy said.

While masses and planet densities emerged from the work, astronomers still aren’t certain how they form or if they are made of rock, water or gas.

Mini Neptunian planets range in size from about 1.5 to 4 times the size of Earth and have a rocky core and puffy gaseous shell of varying thickness. Credit: Geoff Marcy
Mini Neptunian planets range in size from about 1.5 to 4 times the size of Earth and have a rocky core and puffy gaseous shell of varying thickness.
Credit: Geoff Marcy

The team focused on about 42 of these planets. Two planets highlighted by Marcy in his presentation are thought to be rocky, and are named Kepler-99b and Kepler-406b. Both are forty percent larger in size than Earth and have a density similar to lead. The planets orbit their host stars in less than five and three days respectively, making these worlds too hot for life as we know it.

The team used Doppler measurements of the planets’ host stars to measure the reflex wobble of the host star, caused by the gravitational tug on the star exerted by the orbiting planet. The measured wobble reveals the mass of the planet: the higher the mass of the planet, the greater the gravitational tug on the star and hence the greater the wobble.

They also the measured transit timing variations (TTV) to determine how much neighboring planets can tug on one another causing one planet to accelerate and another planet to decelerate along its orbit.

These measurements allow for computing mass and densities of the planets, as well as figuring out the possible chemical composition of these worlds. The majority of the measurements suggest that the mini-Neptunes have a rocky core but some may have a gaseous outer shell of hydrogen or helium. Some might just be rocky with no outer envelope at all.

“What we think is happening is that some of these planets may have water on top of a rocky core,” Marcy said. “Larger planets might have the same rocky core with added gas. That’s how you get planets measuring from 1 to 4 earth radii. The planets with lower densities imply increasing amounts of gas on top of a rocky core.”

Illustration of the Kepler spacecraft (NASA/Kepler mission/Wendy Stenzel)
Illustration of the Kepler spacecraft (NASA/Kepler mission/Wendy Stenzel)

“Kepler’s primary objective is to determine the prevalence of planets of varying sizes and orbits. Of particular interest to the search for life is the prevalence of Earth-sized planets in the habitable zone,” said Natalie Batalha, Kepler mission scientist at NASA’s Ames Research Center. “But the question in the back of our minds is: are all planets the size of Earth rocky? Might some be scaled-down versions of icy Neptunes or steamy water worlds? What fraction are recognizable as kin of our rocky, terrestrial globe?”

The team said that the mass measurements produced by Doppler and TTV will help to answer these questions. The results hint that a large fraction of planets smaller than 1.5 times the radius of Earth may be comprised of the silicates, iron, nickel and magnesium that are found in the terrestrial planets here in the Solar System.

Armed with this type of information, scientists will be able to turn the fraction of stars harboring Earth-sizes planets into the fraction of stars harboring bona-fide rocky planets. And that’s a step closer to finding a habitable environment beyond the Solar System.

Marcy added later in the discussion that there’s one type of telescope that would most helpful: a Terrestrial Planet Finder type mission that would measure the temperature, size, and the orbital parameters of planets as small as our Earth in the habitable zones of distant solar systems. Alas, TPF was canceled.

Read more about the study of mini-Neptunes here.

Posted on by Jason Major

Super-sensitive Camera Captures a Direct Image of an Exoplanet

The Gemini Planet Imager’s first light image of Beta Pictoris b (Processing by Christian Marois, NRC Canada)

The world’s newest and most powerful exoplanet imaging instrument, the recently-installed Gemini Planet Imager (GPI) on the 8-meter Gemini South telescope, has captured its first-light infrared image of an exoplanet: Beta Pictoris b, which orbits the star Beta Pictoris, the second-brightest star in the southern constellation Pictor. The planet is pretty obvious in the image above as a bright clump of pixels just to the lower right of the star in the middle (which is physically covered by a small opaque disk to block glare.) But that cluster of pixels is really a distant planet 63 light-years away and several times more massive — as well as 60% larger — than Jupiter!

And this is only the beginning.

GPI installed on the Gemini South 8m telescope. GPI is the boxed suite mounted under the platform. (Gemini Observatory)
GPI installed on the Gemini South 8m telescope. GPI is the boxed suite mounted beneath the platform. (Gemini Observatory)

While many exoplanets have been discovered and confirmed over the past couple of decades using various techniques, very few have actually been directly imaged. It’s extremely difficult to resolve the faint glow of a planet’s reflected light from within the brilliant glare of its star — but GPI was designed to do just that.

“Most planets that we know about to date are only known because of indirect methods that tell us a planet is there, a bit about its orbit and mass, but not much else,” said Bruce Macintosh of the Lawrence Livermore National Laboratory, who led the team that built the instrument. “With GPI we directly image planets around stars – it’s a bit like being able to dissect the system and really dive into the planet’s atmospheric makeup and characteristics.”

And GPI doesn’t just image distant Jupiter-sized exoplanets; it images them quickly.

“Even these early first-light images are almost a factor of ten better than the previous generation of instruments,” said Macintosh. ” In one minute, we were seeing planets that used to take us an hour to detect.”

Despite its large size, Beta Pictoris b is a very young planet — estimated to be less than 10 million years old (the star itself is only about 12 million.) Its presence is a testament to the ability of large planets to form rapidly and soon around newly-formed stars.

Read more: Exoplanet Confirms Gas Giants Can Form Quickly

“Seeing a planet close to a star after just one minute, was a thrill, and we saw this on only the first week after the instrument was put on the telescope!” added Fredrik Rantakyro a Gemini staff scientist working on the instrument. “Imagine what it will be able to do once we tweak and completely tune its performance.”

Another of GPI’s first-light images captured light scattered by a ring of dust that surrounds the young star HR4796A , about 237 light-years away:

GPI first-light images of HR4796A. (Processing by Marshall Perrin, Space Telescope Science Institute.)
GPI first-light images of HR4796A. (Processing by Marshall Perrin, Space Telescope Science Institute.)

The left image shows shows normal light, including both the dust ring and the residual light from the central star scattered by turbulence in Earth’s atmosphere. The right image shows only polarized light. Leftover starlight is unpolarized and hence removed. The light from the back edge of the disk (to the right of the star) is strongly polarized as it reflects towards Earth, and thus it appears brighter than the forward-facing edge.

It’s thought that the reflective ring could be from a belt of asteroids or comets orbiting HR4796A, and possibly shaped (or “shepherded,” like the rings of Saturn) by as-yet unseen planets. GPI’s advanced capabilities allowed for the full circumference of the ring to be imaged.

The GPI integration team celebrates after obtaining first light images (Gemini Observatory)
The GPI integration team celebrating after obtaining first light images (Gemini Observatory)

GPI’s success in imaging previously-known systems like Beta Pictoris and HR4796A can only indicate many more exciting exoplanet discoveries to come.

“The entire exoplanet community is excited for GPI to usher in a whole new era of planet finding,” says physicist and exoplanet expert Sara Seager of the Massachusetts Institute of Technology. “Each exoplanet detection technique has its heyday. First it was the radial velocity technique (ground-based planet searches that started the whole field). Second it was the transit technique (namely Kepler). Now, it is the ‘direct imaging’ planet-finding technique’s turn to make waves.”

This year the GPI team will begin a large-scale survey, looking at 600 young stars to see what giant planets may be orbiting them.

“Some day, there will be an instrument that will look a lot like GPI, on a telescope in space. And the images and spectra that will come out of that instrument will show a little blue dot that is another Earth.”

– Bruce Macintosh, GPI team leader

The observations above were conducted last November during an “extremely trouble-free debut.” The Gemini South telescope is located near the summit of Cerro Pachon in central Chile, at an altitude of 2,722 meters.

Source: Gemini Observatory press release

Posted on by Nancy Atkinson

Hubble Finds ‘Clear Signal’ of Water in 5 Exoplanet Atmospheres

To determine what’s in the atmosphere of an exoplanet, astronomers watch the planet pass in front of its host star and look at which wavelengths of light are transmitted and which are partially absorbed. Credit: NASA's Goddard Space Flight Center

For the first time, astronomers have found conclusive evidence of water in the hazy atmospheres of planets orbiting other stars. Using the Hubble Space Telescope, two teams of scientists found faint but clear signatures of water in the atmospheres of five exoplanets. All five are so-called ‘hot Jupiters,’ massive worlds that orbit close to their host stars.

“To actually detect the atmosphere of an exoplanet is extraordinarily difficult. But we were able to pull out a very clear signal, and it is water,” said Drake Deming from the University of Maryland, who led a study characterizing the atmospheres of two of the five planets.

“We’re very confident that we see a water signature for multiple planets,” said Avi Mandell, a planetary scientist at NASA’s Goddard Space Flight Center, and lead author of another paper on the remaining three exoplanets. “This work really opens the door for comparing how much water is present in atmospheres on different kinds of exoplanets, for example hotter versus cooler ones.”

The five planets are all well-studied, and would not be friendly places for life as we know it — with blazing temperatures and unusual conditions. WASP-17b is an unusual planet in a retrograde orbit, and sodium had already been detected in its atmosphere.

HD209458b is much-studied windy world, with raging storms, and organic molecules and water had already been detected on this planet in previous studies.

The atmosphere of WASP-12b already has been found to hold vast amounts of carbon as well as water. WASP-19b orbits a nearby star, and has one of the shortest orbital periods of any known planetary body, about 0.7888399 days or approximately 18.932 hours. XO-1b has the distinction of being discovered by amateur astronomers

The astronomers involved in the new studies say the strengths of the water signatures in each world varied, with WASP-17b and HD209458b having the strongest signals.

Currently, studying exoplanet atmospheres can be done when the planets are passing in front of their stars. Researchers can identify the gases in a planet’s atmosphere by determining which wavelengths of the star’s light are transmitted and which are partially absorbed. Deming’s team employed a new technique with longer exposure times, which increased the sensitivity of their measurements.

In both studies, scientists used Hubble’s Wide Field Camera 3 to explore the details of absorption of light through the planets’ atmospheres. The observations were made in a range of infrared wavelengths where a pattern that signifies the presence of water would appear if water were present. The teams compared the shapes and intensities of the absorption profiles, and the consistency of the signatures gave them confidence they saw water.

“These studies, combined with other Hubble observations, are showing us that there are a surprisingly large number of systems for which the signal of water is either attenuated or completely absent,” said Heather Knutson of the California Institute of Technology, a co-author on Deming’s paper. “This suggests that cloudy or hazy atmospheres may in fact be rather common for hot Jupiters.”

Read the teams paper: Deming et al, Mandell et al.

Sources: HubbleSite, University of Maryland.

Posted on by Fraser Cain

Weekly Space Hangout – November 8, 2013

Host: Fraser Cain
Guests: Thad Szabo, Scott Lewis, Ian O’Neill, Alan Boyle, Nancy Atkinson, David Dickinson, Jason Major, Matthew Francis, Nicole Gugliucci

LINKS:
(Check out the comments for some more excellent discussion!)
Alan Boyle on Virgin Galactic
Nancy Atkinson on the hybrid solar eclipse
Jason Major on baby supermassive black holes
Ian O’Neill on quasars (BLACK HOLES DON’T SUCK)
Alan Boyle on Chelyabinsk
Security cam of Chelyabinsk
Matthew Francis on LUX
Nancy Atkinson on the sun (not literally)
Scott Lewis on Frontier Fields
Matthew Francis on Earth-density exoplanet
David Dickinson on GOCE
Kepler Orrery
Fireball FAQs