Posted on by Jon Voisey

Two More Kepler Planets Confirmed

Artst concept of the Kepler telescope in orbit. Credit: NASA

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Hot on the heels of confirming one Kepler planet, the Hobby-Eberly Telescope announces the confirmation of another planet. Another observatory, the Nordic Optical Telescope, confirms its first Kepler planet as well, this one as part of a binary system and providing new insights that may force astronomers to revisit and revise estimations on properties of other extrasolar planets.

The first reported of these planets was the announcement from the Nordic Optical Telescope of the confirmation of Kepler 14b. The team estimates the planet to be eight times the mass of Jupiter. It orbits its parent star in a short 7 days, putting this object into the class of hot Jupiters. As noted above, the star is in a binary system with the second star taking some 2,800 years to complete one orbit.

In the announcement the team analyzed the data taking into consideration an effect that has been left out of previous studies of extrasolar planets. The team found that the glare from the nearby star in the binary orbit spilled over onto the image of the star around which the planet orbited. This extra light would dilute the eclipse caused by the planet and subsequently, changed the estimations of the planets properties. The team reported that not correcting for this light pollution, “leads to an underestimate of the radius and mass of the planet by 10% and 60%, respectively.” While this consideration would only apply for planets orbiting stars that were in binary systems, or line of sight double stars, the Kepler 14 system did not appear to be a binary system without high resolution imaging from the Palomar Observatory. This begs the question of whether or not any of the other 500+ known extrasolar planets are in similar systems that have not yet been resolved and whether their parameters may need revision.

The next planet, reported at the end of July, has been dubbed Kepler 17b. Again, this planet falls into the category of Hot Jupiters, although this one is only two and a half time times the mass of Jupiter. It orbits a star very similar the Sun in mass and radius, although expected to be somewhat younger. The observations of the star outside of planetary transits revealed a good deal of activity with temporary dips that did not persist on a regular basis like the signal from the planet. Such variance is likely due to stellar activity and Sunspots and allowed the team to reveal more information about the planet.

Because the planet could also eclipse starspots, it created a stroboscopic effect and the team confirmed the planet orbits in the same direction as the star spins. This is notable since several planets are known to have retrograde orbits.

Posted on by Jon Voisey

Do Planets Rob Their Stars of Metals?

Artist's impression of the Solar Nebula. Image credit: NASA

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It has been known for several years that stars hosting planets are generally more rich in elements heavier than hydrogen and helium, known in astronomy as “metals”. These heavy elements help to form the cores of the forming planets and accelerate the formation process. However, a new study has helped to suggest that the opposite may also be true: Planets may make their host stars less metal rich than they should otherwise be.

The new research is led by Ivan Ramirez at the Carnegie Institution for Science. In it, the team analyzed the unusual exo-planetary system 16Cygni. The star system itself is a triple star system composed of two stars similar to the sun (A and B) as well as a red dwarf (C). The solar A star and the red dwarf form a tight binary system with the sun-like B star in a wider orbit of nearly 900 AU. 16CygniB was discovered to be host to a Jovian planet in 1996 making it one of the first systems known to contain an extrasolar planet.

The study analyzed the spectra of the two solar type stars and found that the one around which the planet orbits was notably lower in metals than the one in the binary orbit with the red dwarf. Because both stars should have formed from the same molecular cloud astronomers assume their initial compositions should be identical. Since both are similar masses, they should also have evolved similarly in their main-sequence life which should rule out divergence in their chemical fingerprints.

Similar properties have been noted in a 2009 paper by astronomers at the university of Porto in Portugal. In that study, the team compared our own Sun to other stars of similar composition and age. They discovered that the Sun had an odd feature: It was notably depleted in elements known as refractory metals when compared to volatile elements with low melting and boiling temperatures. The team suggested that those missing elements may have been stolen by forming planets. The newer study makes the same proposition.

Both teams note that the effect is not conclusive. They consider that 16CygA may have been polluted by heavy elements, possibly by the accretion of a planet or similar material. However, they note that if this was the case, they should also expect to see an additional amount of lithium. Yet the lithium abundance for the two stars match. The 2009 paper considers similar cases. They consider that the solar nebula may have been seeded by a nearby supernova that would enhance the abundances, but the enhanced elements do not seem to match the expected productions for any type of supernova. Still, with such a small number of systems for which this effect has been discovered, such cases of special pleading are still within the realm of statistical possibility. Future work will undoubtedly search for similar effects in other planetary systems. If confirmed, such elemental oddities could be considered as a sign of planetary formation.

Posted on by Jon Voisey

Applying the Titius-Bode Rule to Exoplanet Systems

55 Cancri. Image credit: NASA/JPL

One of the key methods employed in the practice of the sciences is the search for patterns. Their discovery often hints at something important to which we should pay attention if we want to understand a principle. This can be from simple things like the cycles of the sky throughout the year that trace out our motion in the solar system to the patterns of spectral lines that allow astronomers to measure the universe. Back on our solar system scale, one such apparent pattern that stood steadfast until 1846, was the Titius-Bode rule. This rule noted that the distance of the planets from the sun seemed to follow a pattern described by the equation a = 0.4 + 0.3 × 2n where n was the planet number in order of distance from the Sun. This pattern held very well for the first 7 planets, so long as one included the asteroid Ceres, or the asteroid belt itself, as planet #5. Yet the discovery of Neptune and Pluto discredited this pattern as a mere coincidence, mathematical happenstance and numerology, as the Titius-Bode rule severely underpredicted their distances.

Some still wonder if there wasn’t something more to the rule and orbital resonances didn’t have some sort of subtle effect that was being overlooked and made the rule more of a law, at least for innermost planets. With the rapid discovery of planets around other stars, astronomers are once again looking to see if there might just be some sort of truth to this pattern.

One of the most well populated and well studied exo-planetary systems is 55 Cancri. In 2008, a paper was published in the Mexican Journal of Astronomy and Astrophysics attempting to apply the Titius-Bode rule to this system. In that study, the classical rule could not fit, but, from the five planets known at the time, the researchers were able to fit a similar exponential function to the system. With their fit, they found that, much like our own solar system, there was a “missing planet” for what should be the 5th from the parent star. The fit predicted it should lie at a distance of roughly two AU. However, since the paper was published, the orbital characteristics of the system have been revised significantly, throwing off the predictions of the 2008 study.

However, another paper was recently written, updating the fit for the 55 Cnc system. This time, to make the fit work well, the author was forced to assume the possibility of four undiscovered planets. If they were to exist, one of them should exist at a distance of 1.5 AU which, for that system may place it in the habitable zone.

But what of other planetary systems? Presently, there have been few other systems that are sufficiently explored to begin to explore such potential relations. One paper, released in 2010, noted that, at that time, only 15 systems were known with three or more planets. While some appeared, superficially, to have some sort of patterning, the authors declined to speculate on whether or not there was any deeper meaning since, with so little data, a line would be quite easy to fit.

So for now, it’s another game of patience as astronomers continue probing more systems and discovering more planets. If, at some point, a planet were discovered that was predicted by a Titius-Bode relation, it would support the underlying principle that something was sorting the planets in a regular manner. But then again, that’s what they said when Ceres and Neptune were discovered.

Posted on by Jon Voisey

Zooming in on Proto-Planetary Disks

On the road to planetary formation, the first step is an accretion disk around a proto-star. Such disks, known as proplyds, are frequently detected in star forming regions like the Orion nebula providing an understanding of the early life of planetary systems. The telltale hint that they exist is the warm infrared glow of the forming (or perhaps nearly formed) star heating the gas and dust, but although many have been detected this way, few have been observed with resolution that makes out any details on the disk itself. A new study aims to help add to the understanding of these systems with spatially resolved observations of two proplyds, including one already known to be host to a multiple planet system.

The two new systems under study are HD 107146 and HR 8799. The latter of these two systems is notable for having four known planets which have been directly imaged previously. HD 107146 is relatively close to our solar system, being only 28.5 pc away. This young star is similar to the Sun in mass and composition and is estimated to be somewhere between 80 and 200 million years young. Previous studies have examined this system’s disk and revealed that it is composed of nearly as much dust as there is gas, which means that much of the gas has likely been either accreted or stripped. Although not directly detected, the earlier studies have also suggested that the system may be hiding young planets. The evidence for this comes from possible banding in the disk. This is interpreted as similar to the rings and gaps in Saturn’s system, caused by shepherding moons, except in this case, the moon’s role would be fulfilled by planets creating resonances.

The new research, led by Meredith Hughes from the University of California, Berkeley, confirmed the presence of the disk around the star and found its brightness peaked at a distance of about 100 AU from the parent star (more than twice the average orbital distance of Pluto). Overall, their observations match models with a “broad ring extending from 50 to 170 AU”.

When looking at HR 8799’s disk, the team was given four nights, but due to poor weather, only one night’s worth of data from the Submillimeter Array atop Mauna Kea. The reduced amount of data left high uncertainties in the subsequent analysis. While the team attempted to search for banding that could induced by planets, the team was unable to find any. A study published earlier this year by a team at the University of Exeter also examined the HR 8799 disk and reported a slightly brighter clump on one side. The new study finds a similar clump but cautions that, due to the still poor observations of this system, the result may be suspect. A similar case happened when astronomers studied Vega’s dust disk and reported finding clumpy structure when it was, in reality, it was nothing but statistical noise.

These results, as well as the previous ones from the Exeter team and observations from Spitzer have suggested that the dust ring extends out to as far as 250 AU, and as far inwards as 80, but it is likely the inner radius is closer to 150 AU. If the inner radius is the correct value, this places it at roughly the limit that it could be shaped by the outermost planet HR 8799b which lies at just under 70 AU.

Posted on by Jon Voisey

Another Kepler Planet Confirmed

Artist's concept of Kepler in action. NASA/Kepler mission/Wendy Stenzel.

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The Kepler mission, launched in 2009, is looking to greatly improve our understanding of planets. Since beginning operation, the planet hunting spacecraft has made tentative identifications of over 1,200 planets, having spotted them as they transited their parent stars. However, these planets need confirmation from a more robust method, specifically the spectroscopically detected wobbles, before they’re added to the official list of extrasolar planets.

Thus far, confirmations have been slow to come; only 16 of the planets have been detected using other methods. But recently, astronomers using the Hobby-Eberly Telescope (HET), operated by the University of Texas, Austin have confirmed another.

The planet, Kepler-15b, is the first confirmed by this unique telescope. As opposed to most observatories, the mirror at the HET does not track the stars. Instead, the mirror remains stationary and the detecting instruments are moved along the focal plane to track the object in question. While this doesn’t allow for the object to track the entire night, it does let astronomers get continuous observation of the target for up to 2 hours. This unusual configuration was estimated to reduce the construction costs by as much as 80%.

From the Kepler observations, the tentative planet was expected to have an orbital period of just under 5 days and would transit the parent star for 3.5 hours, dimming the star’s light by about 1.2%. Using this information, the expectation was that the planet should have a radius of 1.4 times that of Jupiter, putting it in the class of “hot-Jupiters”.

The observations by the HET were taken from March until November of 2010. The team used the telescope’s spectrometer to search for the signs of variation between 2 and 100 days. When analyzed for periodicity, the team independently confirmed a strong signal with a period of 4.94 days.

Using the new spectroscopic data, the team estimates the new planet has a mass of 0.66 Jupiter masses, and reduces the estimated radius to 0.96 times that of Jupiter, giving a mean density of ~.9 grams per cubic centimeter. The parent star contains high amounts of heavy elements and is tied with Kepler-6 for the most metal rich parent star of the Kepler findings. If the planet, being formed from the same interstellar cloud, has similar metallicity, then it could be expected that the presence of these additional heavy elements could help to shrink the planet.

The team also reports that they have observed other purported Kepler planets and intends to include the findings in an upcoming publication. Additionally, the HET is scheduled for a major upgrade starting later this year. This will include upgrades to the tracking assembly, as well as the fiber optics used in the spectroscope. Currently, this instrument is only capable of performing confirmations for Jovian massed planets, but once upgrades are complete, the team expects to be able to use the system to search for lower mass candidates in the mass range of Neptune and those in the “Super-Earth” category.

Posted on by Jon Voisey

More Images of HR 8799

HR 8799 system
One of the discovery images of the system obtained at the Keck II telescope using adaptive optics system and the NIRC2 Near-Infrared Imager. Image shows all four confirmed planets indicated as b, c, d and e in the labeled image. Planet "b" is a ~5 Jupiter-mass planet orbiting at about ~68 AU, while planets c, d, and e are ~7 Jupiter-mass companions orbiting the star at about 38, 24 and 14.5 AU. Credit: NRC-HIA, C. Marois & Keck Observatory

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Late last year, astronomers using the Keck II telescope released the first direct image of a planetary system including four planets. These planets orbited the star HR 8799 and were taken in the J and L bandpasses which are in the near-infrared portion of the spectrum. Since then the team has collected new data using the same telescope, extending the spectral range into the mid-infrared portion of the spectra.

The new images are important to astronomers because this provides a more complete understanding of the distribution of radiation that the planets are emitting. This can be compared to models of planetary formation, allowing these young planets to act as a test bed. Previous comparison to models have suggested that these planets have cool, dusty atmospheres without the presence of methane or other common absorbing molecules.

The team hopes that the new observations will help distinguish between the various models that explain this deficiency of methane. Unfortunately, getting good observations in this portion of the spectra is challenging. In particular, at the Keck telescope, the design of the telescope itself makes observations especially challenging due to portions of the instrument themselves emitting in the infrared, masking the faint signals from the planet.

To bring out the planets, the team developed a new technique to help clean the images of the unwanted noise. They estimate that their new technique is nine times more efficient than previously used techniques. To do this, they moved the telescope slightly between images, allowing the patterns of interference to change between exposures, thereby making them more apparent and easier to remove.

When the results were analyzed and compared to models, the team found that they were in good agreement with predictions of planetary evolution for planets c and d. However, for planet b, the models predicted a planet with a radius that would be too small to account for the observed luminosity. The observations could be brought into agreement with the models by increasing the metallicity of the model.

With additional future observations, the team hopes to constrain these models and further investigate the atmospheres of these planets.

NOTE: I Emailed the authors of the paper to ask permission to reproduce the new image here, but have not gotten a reply. The one used above is the K and L band images from last year. To see the new ones, feel free to go to the paper directly.

Posted on by Jon Voisey

New Planet Discovered In Trinary Star System

A planet 6 times the mass of Earth orbits around the star Gliese 667 C, which belongs to a triple system. Credit: ESO

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Until recently, astronomers were highly skeptical of whether or not planets should be possible in multiple star systems. It was expected that the constantly varying gravitational force would eventually tug the planet out of orbit. But despite doubts, astronomers have found several planets in just such star systems. Recently, astronomers announced another, this time in the trinary star HD 132563.

The detection of the new planet came as part of a larger study on the trinary star system spanning 10 years. The two main stars that comprise the system are both similar to the Sun in mass, although somewhat less prevalent in metals, and orbit each other at a distance of around 400 AU. The main star, HD 132563A is also itself, a binary. This fact was not previously recognized and also reported by the team, led by Silvano Desidera from the Astronomical Observatory in Padova, Italy.

The newly discovered planet orbits the secondary star in the system, HD 132563B. As with the binary component of the main star, the new planet was discovered spectroscopically. The planet is at least 1.3 times the mass of Jupiter, with an average distance from its parent star of 2.6 AU, and an moderately high eccentricity of 0.22.

The team also attempted to image the planet directly using adaptive optics from the Italian Telescopio Nazionale Galileo. While there was a hint in the glare of the star that may have been the planet in question, the team could not rule out that the detection was not an instrumental effect.

With the discovery of this new planet, the total number of discovered planets in multiple star systems lies at eight. while this is rather small numbers from which to draw firm conclusions, it appears that planets can be commonly found orbiting the more remote members of trinary star systems for good periods of time. On the shorter end, the stellar system is anticipated to be 1-3 billion years in aged, based on the amount of stellar activity and amount of lithium present in the star’s atmosphere (which decreases with time). However, fitting of the mass and luminosity onto isochrones suggest the stars may be as much as 5 billion years in age. In either situation, the planetary system is dynamically stable.

Also based on these eight systems, the team also suggests that planets existing around such far removed members of a multiple star system may be as common as planets around wide binaries, or even single stars.

Posted on by Nancy Atkinson

One Million Observations Now in the Books for Hubble Telescope

Artist's impression of the transiting exoplanet HAT-P-7b. Credit: NASA/ESA

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After 21 years in orbit, the Hubble Space Telescope has reached an historic milestone: the venerable HST has made its millionth observation. The telescope was used to search for the chemical signature of water in the atmosphere of planet HAT-P-7b, a gas giant larger than Jupiter which orbits the star HAT-P-7, about 1,000 light-years away from Earth. The observation was led by Dr. Drake Deming, planetary scientist and astronomer from the University of Maryland and the Goddard Space Flight Center.

With this announcement, however, there is no stunning image or unprecedented view of an exoplanet. The millionth observation will show up as squiggly lines on a graph, since the observation was done with Hubble’s spectrograph.

Spectroscopy is the technique of splitting light into its component colors, and the gases present in a planet’s atmosphere leave a fingerprint in the form of the distinctive color patterns that different gases absorb. Analyzing this data can give precise measurements of which elements are present in the exoplanet’s atmosphere.

“We are looking for the spectral signature of water vapor. This is an extremely precise observation and it will take months of analysis before we have an answer,” said Deming. “Hubble has demonstrated that it is ideally suited for characterizing the atmospheres of exoplanets and we are excited to see what this latest targeted world will reveal.”

“With a million observations and many thousands of scientific papers to its name, Hubble is one of the most productive scientific instruments ever built,” said Alvaro Gimenez, head of science and robotic exploration for the European Space Agency. “As well as changing our view of the Universe with its stunning imagery, Hubble has revolutionized whole areas of science.”

Hubble’s on-orbit history began when it was launched on the space shuttle Discovery on April 24, 1990. The HST has collected over 50 terabytes of data, enough to fill more than 10,000 DVDs. While the the data collected in the one millionth observation is now proprietary for the scientists, within a year, it will be released to the public. The huge and varied library of data Hubble has produced is made freely available to scientists and the public through an online archive at his link:

http://hla.stsci.edu/

Hubble made the millionth observation using its Wide Field Camera 3, a visible- and infrared-light imager with an on-board spectrometer. It was installed by astronauts during the Hubble Servicing Mission 4 in May 2009.

More Hubble info and images can be found at the HubbleSite, and ESA’s Hubble website.

Posted on by Jon Voisey

Rocky, Low-Mass Planet Discovered by Microlensing

A low-mass, rocky planet orbits a distant sun
A low-mass, rocky planet orbits a distant sun

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In planet hunting today, there seems to be one burning question that nearly every new article published touches on: Where did these planets come from?

As astronomers discovered the first extrasolar planets, it quickly became obvious that the formation theories that we’d built on our own solar system were only part of the story. They didn’t predict the vast number of hot Jupiters astronomers found nearly everywhere. Astronomers went back to the drawing board to put more details into the theory, breaking formation down into quick, single collapses and more gradual accretion of gas disks, and worrying about the effects of migration. It’s likely all these effects take place to some extent, but ferreting out just how much is now the big challenge for astronomers. Hampering their efforts is the biased sample from the gravitational-wobble technique which preferentially discovered high mass, tightly orbiting planets. The addition of Kepler to planet hunter’s arsenal has removed some of this bias, readily finding planets to far lower masses, but still prefers planets in short orbits where they are more likely to transit. However, the addition of another technique, gravitational microlensing, promises to find planets down to 10 Earth masses, much further out from their parent stars. Using this technique, a team of astronomers has just announced the detection of a rocky planet just in this range.

According to the Extrasolar Planet Encyclopaedia, astronomers have discovered 13 planets using gravitational microlensing. The newly announced one, MOA-2009-BLG-266Lb, is estimated to be just over 10 times the mass of Earth and orbits at a distance of 3.2 AUs around a parent star with roughly half the mass of the Sun. The new finding is important because it is one of the first planets in this mass range that lies beyond the “snow line”, the distance during formation of a planetary system beyond which ice can form from water, ammonia, and methane. This presence of icy grains is expected to assist in the formation of planets since it creates additional, solid material to form the planetary core. Just beyond the snow line, astronomers would expect that planets would form the most quickly since, as you move further, beyond this line, the density drops. Models have predicted that planets forming here should quickly reach a mass of 10 Earth masses by accumulating most of the solid material in the vicinity. The forming planet then, can slowly accrete gaseous envelopes. If it accumulates this material quickly enough, the gaseous atmosphere may become too massive and collapse, beginning a rapid gas accretion phase forming a gas giant.

The timing of these three phases, as well as their distance dependency, makes testable predictions that can be contrasted with the observations as astronomers discover more planets in this vicinity. In particular, it has suggested that we should see few gas giants around low mass stars because the gas disk is expected to dissipate before the atmosphere collapse leading to the rapid accretion phase. This expectation has been generally supported by the findings of the 500+ confirmed extrasolar planets, as well as the 1,200+ candidates from Kepler, lending credence to this core collapse + slow accretion model. Additionally, Kepler has also reported a large population of relatively low mass planets, interior to the snow line. This too supports the hypothesis since the greater difficulty in forming cores without the presence of ice would hamper the formation of large planets. However, other predictions, such as not expecting massive planets in tight orbits, is still largely contradictory to the hypothesis and greater testing with additional discoveries will be needed.

Assisting with this, several new observing programs will be coming on line in the near future. The Optical Gravitational Lensing Experiment IV (OGLE-IV) has just entered operation and a new program at Wise Observatory in Tel Aviv will begin operation following up on microlensing events next year. Also expected in the near future is the Korean Microlensing Network (KMT-Net) which will operate telescopes in South Africa, Chile, and Australia using 1.6 meter telescopes covering 4 square degrees of the galactic bulge.

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.