Screenshot of a new exoplanet app for iPhone and iPad.
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Just in time for the announcement yesterday of the multi-planet solar system discovery, and an upcoming exoplanet announcement by the Kepler team comes a new version of a free exoplanet app for iPhone and iPad. We got a note from Hanno Rein, who developed “Exoplanet,” and who just finished his PhD in astrophysics at the University of Cambridge. “It lists all discovered extrasolar planets with a lot of background information, many visualizations and animations,” he said. Other highlights include an easy search and filter for the database, real telescope images of the host star, visualizations of the orbits and the habitable zone, interactive 3D size comparison to our own solar system and much more.
With all the exoplanet news lately, “Exoplanet” is updated daily and push notifications are sent out whenever a new planet is discovered (although they can be turned off if you don’t want to get notifications). Pretty much everything known about any exoplanet is included, such as physical parameters, along with various visualizations and background information, which make this exciting subject accessible for a wider audience.
New for version 3.9 are direct links to planets and planetary systems, links to other planets of the same multi-planetary system have been added, and you can now link from any e-mail or website directly to this application by using a URL form of the exoplanet, for example, ://Fomalhaut
Rein developed this app while a student, and wanted to keep it free (knowing how hard it is to be a poor student!) so there are ads on the app. But a non-ad version is available for only $.99 USD.
I don’t have an iPhone or iPad (yet!) but Fraser does, and he said the Exoplanet app is very cool!
Artists impression shows the planetary system around the Sun-like star HD 10180. Credit: ESO/L. Calçada
There is another Sun-like star out there with an intriguing family of planets orbiting about and it could be the closest parallel to our own solar system that astronomers have found yet. European astronomers discovered a planetary system containing at least five planets, orbiting the star HD 10180, with evidence that two other planets may be present. If confirmed, one of those would have the lowest mass ever found.
“We have found what is most likely the system with the most planets yet discovered,” says Christophe Lovis, who led the team. “This remarkable discovery also highlights the fact that we are now entering a new era in exoplanet research: the study of complex planetary systems and not just of individual planets. Studies of planetary motions in the new system reveal complex gravitational interactions between the planets and give us insights into the long-term evolution of the system.”
To make this system even more intriguing, the team also found evidence that the distances of the planets from their star follow a regular pattern, as also seen in our Solar System. “This could be a signature of the formation process of these planetary systems,” said team member Michel Mayor.
HD 10180, is located 127 light years away in the southern constellation of Hydrus. The five confirmed planets are large, about the size of Neptune — between 13 and 25 Earth masses —with orbital periods ranging from between six and 600 days. The planets’ distances from the star ranges from 0.06 and 1.4 times the Earth–Sun distance.
A close-up of the sky around the star HD 10180. Credit: ESO and Digitized Sky Survey 2. Acknowledgment: Davide De Martin
“We also have good reasons to believe that two other planets are present,” said Lovis. One would be a Saturn-like planet (with a minimum mass of 65 Earth masses) orbiting in 2200 days. The other would be the least massive exoplanet ever discovered, with a mass of about 1.4 times that of the Earth. It is very close to its host star, at just 2 percent of the Earth–Sun distance. One “year” on this planet would last only 1.18 Earth-days.
“This object causes a wobble of its star of only about 3 km/hour— slower than walking speed — and this motion is very hard to measure,” says team member Damien Ségransan. If confirmed, this object would be another example of a hot rocky planet, similar to Corot-7b.
The team used the planet-finding HARPS spectrograph, attached to ESO’s 3.6-metre telescope at La Silla, Chile, and made observations of HD 10180 for six years.
The newly discovered system of planets around HD 10180 is unique in several respects. First of all, with at least five Neptune-like planets lying within a distance equivalent to the orbit of Mars, this system is more populated than our Solar System in its inner region, and has many more massive planets there. Furthermore, the system probably has no Jupiter-like gas giant. In addition, all the planets seem to have almost circular orbits.
With this new announcement, the total number of exoplanets found is 472.
This plot of data from NASA's Spitzer Space Telescope tells astronomers that a dusty planetary smashup probably occurred around a pair of tight twin, or binary, stars. Image credit: NASA/JPL-Caltech/Harvard-Smithsonian CfA
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Astronomers studying double star systems where the two stars are extremely close have found a pattern of destruction. While there probably isn’t a Star Wars-like Death Star roaming the Universe, tight binary systems might provide the equivalent of Darth Vader’s favorite weapon. “This is real-life science fiction,” said Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics. “Our data tell us that planets in these systems might not be so lucky — collisions could be common. It’s theoretically possible that habitable planets could exist around these types of stars, so if there happened to be any life there, it could be doomed.”
Using the Spitzer Space Telescope, Drake and his team spotted a surprisingly large amount of dust around three mature, close-orbiting star pairs, that might be the aftermath of tremendous planetary collisions.
Drake is the principal investigator of the research, published in the Aug.19 issue of the Astrophysical Journal Letters.
The particular class of binary stars in the study are extremely close together. Named RS Canum Venaticorums, or RS CVns for short, they are separated by only about 3.2-million kilometers (two-million miles ), or two percent of the distance between Earth and our sun. The binaries orbit around each other every few days, with one face on each star perpetually locked and pointed toward the other.
These stars are familiarly like our own Sun – about the same size and probably about a billion to a few billion years old — roughly the age of our sun when life first evolved on Earth. But these stars spin much faster, and, as a result, have powerful magnetic fields, and giant, dark spots. The magnetic activity drives strong stellar winds — gale-force versions of the solar wind — that slow the stars down, pulling the twirling duos closer over time.
This is not a good scenario for planetary survival.
As the stars cozy up to each other, their gravitational influences change, and this could cause disturbances to planetary bodies orbiting around both stars. Comets and any planets that may exist in the systems would start jostling about and banging into each other, sometimes in powerful collisions. This includes planets that could theoretically be circling in the double stars’ habitable zone, a region where temperatures would allow liquid water to exist. Though no habitable planets have been discovered around any stars beyond our sun at this point in time, tight double-star systems are known to host planets; for example, one system not in the study, called HW Vir, has two gas-giant planets.
“These kinds of systems paint a picture of the late stages in the lives of planetary systems,” said Marc Kuchner, a co-author from NASA Goddard Space Flight Center. “And it’s a future that’s messy and violent.”
The temperatures around these systems measured by Spitzer are about the same as molten lava. The astronomers says that dust normally would have dissipated and blown away from the stars by this mature stage in their lives. They conclude that something — most likely planetary collisions — must therefore be kicking up the fresh dust. In addition, because dusty disks have now been found around four, older binary systems, the scientists know that the observations are not a fluke. Something chaotic is very likely going on.
If any life forms did exist in these star systems, and they could look up at the sky, they would have quite a view. Marco Matranga, lead author of the paper, also from Harvard-Smithsonian said, “The skies there would have two huge suns, like the ones above the planet Tatooine in ‘Star Wars.'”
The research was published in the Aug.19 issue of the Astrophysical Journal Letters.
Next time you hear someone complaining that it’s too hot outside, you can make them feel better by pointing out that at least their planet isn’t so hot it is vaporizing into space. Unless of course you happen to be speaking to someone from the gaseous extrasolar planet HD 209458b.
New observations from the Hubble Cosmic Origins Spectrograph (COS) confirm suspicions from 2003 that the planet HD 209458b is behaving like a Jupiter-sized comet, losing its atmosphere in a huge plume due to the powerful solar wind of its too-close star.
HD 209458b is a “hot Jupiter”: a gas giant that orbits extremely close to its star. It whips around its star in 3.5 days, making even speedy little Mercury with its 88 day orbit around the sun look like a slacker.
Astronomers have managed to learn a lot about HD 209458b because it is a transiting planet. That means that its orbit is aligned just right, so from our point of view it blocks some of the light from its star. When that happens, it gives hints at the planet’s size, and gives a much better constraint on the mass. HD 209458b is a little more than two thirds the mass of Jupiter, but heat from its star has puffed it up to two and a half times Jupiter’s diameter.
In the case of HD 209458b, during transits some of the star’s light passes through the planet’s escaping, 2,000-degree-Fahrenheit atmosphere, allowing scientists to tell what it is made of and how fast it is being lost to space.
“We found gas escaping at high velocities, with a large amount of this gas flowing toward us at 22,000 miles per hour,” said astronomer Jeffrey Linsky of the University of Colorado in Boulder, leader of the COS study. “This large gas flow is likely gas swept up by the stellar wind to form the comet-like tail trailing the planet.”
The escaping planetary gases absorbed starlight at wavelengths characteristic of heavier elements like carbon and silicon, suggesting that the star’s intense heat is driving circulation deep in HD 209458b’s atmosphere, dredging up material that would otherwise remain far beneath lighter elements like hydrogen.
Even though its atmosphere is constantly streaming away into space, HD 209458b won’t be disappearing anytime soon. At the measured rate of loss, the planet would last about a trillion years, far longer than the lifetime of its host star.
So, be thankful that even on hot summer days, your planet is in no danger of being vaporized by its star. And if you do happen to be speaking to someone from HD 209458b, you can reassure them that their planet will still be there when they return home. Well, most of it, anyway.
Artists impression of the 'hot Jupiter' HD209458b, which has incredible storms. Credit: ESO.
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Likely, future interstellar flights will not include the exoplanet HD209458b as a featured get-away destination. Not only is this extrasolar planet a scorchingly hot world where the poisonous carbon monoxide atmosphere is being evaporated, but new observations show this gas giant also has superstorms with winds of 5,000 to 10,000 km per hour. “It’s definitely not a place for the faint-hearted,” said Ignas Snellen, from Leiden University in the Netherlands who led a team of astronomers using the Very Large Telescope (VLT) to observe HD209458b, one of the most-studied planets orbiting around other stars. But Snellen told Universe Today that being able to detect this superstorm is extremely exciting and bodes well for finding possible life on other, more Earth-like planets.
“Astronomers have tried to do this for more than a decade,” Snellen said in an email, “basically since the first exoplanets were discovered. We now learn a lot about this gas-giant’s atmosphere, like what kind of gases are there, how hot is it, about its circulation. But we really would like to do this for Earth-like planets. This will be interesting, because using the same techniques we could find out whether there could be life on these planets.”
HD209458b (unofficially called Osiris) is an exoplanet with about 60% the mass of Jupiter orbiting a sun-like star located 150 light-years from Earth towards the constellation of Pegasus.
It orbits at a distance of only one twentieth of the Earth’s orbit around the Sun, and is heated intensely by its parent star, a yellow dwarf with 1.1 solar masses, and a surface temperature of 6000 K. The planet has a surface temperature of about 1000 degrees Celsius on the hot side. But as the planet always has the same side to its star, one side is very hot, while the other is much cooler.
Just as big temperature differences on Earth cause high winds, the same processes cause high winds on HD209458b. But even Earth’s hurricanes are nothing compared to this exoplanet’s superstorms.
Using the powerful CRIRES spectrograph on the VLT the team from Leiden University’s Institute for Space Research (SRON), and MIT in the United States were able to detect and analyze faint fingerprints which showed the high winds. They observed the planet for about five hours, as it passed in front of its star. “CRIRES is the only instrument in the world that can deliver spectra that are sharp enough to determine the position of the carbon monoxide lines at a precision of 1 part in 100,000,” said team member Remco de Kok. “This high precision allows us to measure the velocity of the carbon monoxide gas for the first time using the Doppler effect.”
The astronomers were also able to directly measured the velocity of the exoplanet as it orbits its home star, a first for exoplanet study. “The planet moves with 140 km/sec, and the star moves at 84 meters/second,” said Snellen, “so more than a thousand times slower. Both star and planet orbit the common center of gravity of the system. Having both velocities, using Newton’s laws of gravity we can simply solve for the masses of the two objects.”
The reason this planet is so well studied is that it is the brightest known transiting system in the sky. “The planet moves, as seen from the Earth, in front of its star once per three-and-a-half days,” said Snellen. “This takes about 3 hours. During these three hours, a tiny little bit of starlight filters through the atmosphere of the planet, leaving an imprint of the molecular absorption lines which we have now measured.”
Also for the first time, the astronomers measured how much carbon is present in the atmosphere of this planet. “It seems that H209458b is actually as carbon-rich as Jupiter and Saturn. This could indicate that it was formed in the same way,” said Snellen.
Snellen hopes that by refining these techniques, astronomers may one day be able to study the atmospheres of Earth-like planets, and determine whether life also exists elsewhere in the Universe.
“However, this will be about one hundred times more difficult than what we do now,” he said. “In particular oxygen and ozone are very interesting. On Earth we only have oxygen in the atmosphere because it is constantly produced by living organism, with photosynthesis of plants. If there would be some kind of global disaster and all the life on Earth would go extinct, including plant life and that in the oceans, all the oxygen in the earth atmosphere would quickly disappear. Hence finding oxygen in the atmosphere of an earth-like planet would be extremely exciting! Something to dream about for the future!”
Family portrait of the first 15 CoRoT planets. Credit: Patrice Amoyel (CNES)
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The CoRoT (Convection, Rotation and Transits) spacecraft has been busy, and using this exoplanet-finding-machine astronomers recently found six new extrasolar planets, which contain an odd assortment of new worlds. They include shrunken-Saturns to bloated hot Jupiters, as well a rare brown dwarf with 60 times the mass of Jupiter. “Each of these planets is interesting in its own right, but what is really fascinating is how diverse they are,” said co-investigator Dr Suzanne Aigrain from Oxford University’s Department of Physics. “Planets are intrinsically complex objects, and we have much to learn about them yet.”
CoRoT is dedicated to looking for planets orbiting other stars, and finds them when they transit, or pass in front of their stars. CoRot now has found 15 of the total 461 exoplanets.
Once CoRoT detects a transit, additional observations are made from the ground, using a number of telescopes all over the world. Although astronomers cannot see the planets directly, they use the space- and ground-based data to measure the sizes, masses, and orbits of these new planets precisely. This is why, among all known exoplanets, those with transits yield the most complete information about planet formation and evolution.
‘Every discovery of an extrasolar planetary system is a new piece in the puzzle of how these systems do form and evolve. The more systems we uncover, the better we can hope to understand the processes at play,’ said Magali Deleuil, researcher at the Laboratoire d’Astrophysique de Marseille (LAM) and head of the CoRoT exoplanet program.
The six new planets are:
CoRoT-8b: the smallest in this batch: At about 70% of the size and mass of Saturn, CoRoT-8b is moderately small among the previously known transiting exoplanets. Its internal structure should be similar to that of ice giants, like Uranus and Neptune, in the Solar System. It is the smallest planet discovered by the CoRoT team so far after CoRoT-7b, the first transiting Super-Earth.
CoRoT-10b: the eccentric giant: The orbit of CoRoT-10b is so elongated that the planet passes both very close to and very far away from its star. The amount of radiation it receives from the star varies tenfold in intensity, and scientists estimate that its surface temperature may increase from 250 to 600°C, all in the space of 13 Earth-days (the length of the year on CoRoT-10b).
CoRoT-11b: the planet whose star does the twist: CoRoT-11, the host star of CoRoT-11b, rotates around its axis in 40 hours. For comparison, the Sun’s rotation period is 26 days. It is particularly difficult to confirm planets around rapidly rotating stars, so this detection is a significant achievement for the CoRoT team.
CoRoT-12b, 13b and 14b: a trio of giants: These three planets all orbit close to their host star but have very different properties. Although CoRoT-13b is smaller than Jupiter, it is twice as dense. This suggests the presence of a massive rocky core inside the planet. With a radius 50% large than Jupiter’s (or 16 times larger than the Earth’s), CoRoT-12b belongs to the family of `bloated hot Jupiters’, whose anomalously large sizes are due to the intense stellar radiation they receive. On the other hand, CoRoT-14b, which is even closer to its parent star, has a size similar to Jupiter’s. It is also massive, 7.5 times the mass of Jupiter, which may explain why it is less puffed up. Such very massive and very hot planets are rare, CoRoT-14b is only the second one discovered so far.
CoRoT-15b: the brown dwarf: CoRoT-15b’s mass is about 60 times that of Jupiter. This makes it incredibly dense, about 40 times more so than Jupiter. For that reason, it is classified as a brown dwarf, intermediate in nature between planets and stars. Brown dwarfs are much rarer than planets, which makes this discovery all the more exciting.
For the first time, astronomers have been able to directly follow the motion of an exoplanet as it moves to the other side of its host star. Credit: ESO/A.-M. Lagrange
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For the first time, astronomers have been able to directly follow the motion of an exoplanet as it moves from one side of its host star to the other. The planet has the smallest orbit so far of all directly imaged exoplanets, lying almost as close to its parent star as Saturn is to the Sun. The star, beta Pictoris is only 12 million years old, and so this exoplanet confirms that gas giant planets can form very rapidly—in only a few million years—within such circumstellar disks, and experts say that this discovery validates the theory that these unique, gaseous disk structures can be used as a sort of “fingerprint” to characterize their embedded planets.
Beta Pictoris is 75% more massive than our Sun, and is located about 60 light-years away towards the constellation of Pictor (the Painter). This is one of the best-known examples of a star surrounded by a dusty debris disc. Earlier observations showed a warp of the disc, a secondary inclined disc and comets falling onto the star.
“Those were indirect, but tell-tale signs that strongly suggested the presence of a massive planet, and our new observations now definitively prove this,” said team leader Anne-Marie Lagrange. “Because the star is so young, our results prove that giant planets can form in discs in time-spans as short as a few million years.”
This exoplanet, dubbed Beta Pictoris b, was thought to have been spotted first in 2003, and then was first imaged back in 2008. But the astronomer couldn’t rule out definitively that the possible planet wasn’t just a foreground or background object. These new observations confirm that, indeed, the object is a gas giant planet orbiting the star.
Other recent observations have shown that discs around young stars disperse within a few million years, and that giant planet formation must occur faster than previously thought. This artist’s impression shows how the planet inside the disc of Beta Pictoris may look. Credit: ESO/L. Calçada
Only about ten exoplanets have been imaged, Beta Pictoris b, has the smallest orbit known so far. It is located at a distance between 8 and 15 times the Earth-Sun separation — or 8-15 Astronomical Units — which is about the distance of Saturn from the Sun.
“The short period of the planet will allow us to record the full orbit within maybe 15-20 years, and further studies of Beta Pictoris b will provide invaluable insights into the physics and chemistry of a young giant planet’s atmosphere,” said student researcher Mickael Bonnefoy.
The planet has a mass about nine times that of Jupiter, and the right mass and location to explain the observed warp in the inner parts of the disc. This discovery therefore bears some similarity to the prediction of the existence of Neptune by astronomers Adams and Le Verrier in the 19th century, based on observations of the orbit of Uranus.
The team used the NAOS-CONICA instrument mounted on one of the 8.2-metre Unit Telescopes of ESO’s Very Large Telescope (VLT).
These most recent observations, taken during autumn 2009, revealed the object on the other side of the disc from where it was seen in 2008, and after a period of hiding either behind or in front of the star (in which case it is hidden in the glare of the star). This confirmed that the source indeed was an exoplanet and that it was orbiting its host star. It also provided insights into the size of its orbit around the star.
“Together with the planets found around the young, massive stars Fomalhaut and HR8799, the existence of Beta Pictoris b suggests that super-Jupiters could be frequent byproducts of planet formation around more massive stars,” said team member Gael Chauvin.
“The recent direct images of exoplanets — many made by the VLT— illustrate the diversity of planetary systems,” said Lagrange. “Among those, Beta Pictoris b is the most promising case of a planet that could have formed in the same way as the giant planets in our Solar System.”
Epsilon Andromedae. Illustration Credit: NASA, ESA, and A. Feild (STScI) Science Credit: NASA, ESA, and B. McArthur, University of Texas at Austin, McDonald Observatory.
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Astronomers are finding that not only are there a wide range of different extrasolar planets, but there are different types of planetary systems, as well. “We’re not in Kansas anymore as far as solar systems go,” said Barbara McDonald from the University of Texas’ McDonald Observatory, at the American Astronomical Society meeting in Miami, Florida today. “The exciting thing is, we found another multi-planet system that is not at all like our own.”
A close look at the Upsilon Andromedae system with the Hubble Space Telescope, the Hobby-Eberly Telescope and other ground-based telescopes shows a whacky system where planets are out of tilt and have highly inclined orbits. The astronomers also found another planet, and also another star – this is likely a binary star system.
Even with Pluto’s inclined orbit, our solar system looks like an ocean of calm compared to Upsilon Andromedae. Comparison of solar systems. Credit: HubbleSite
McDonald said these surprising findings will impact theories of how multi-planet systems evolve, and it shows that some violent events can happen to disrupt planets’ orbits after a planetary system forms.
“The findings mean that future studies of exoplanetary systems will be more complicated,” she said. “Astronomers can no longer assume all planets orbit their parent star in a single plane.” says Barbara McArthur of The University of Texas at Austin’s McDonald Observatory.
Similar to our Sun in its properties, Upsilon Andromedae lies about 44 light-years away. It’s a little younger, more massive, and brighter than the Sun. For just over a decade, astronomers have known that three Jupiter-type planets orbit the yellow-white star Upsilon Andromedae.
But after over a thousand combined observations, McDonald and her team uncovered hints that a fourth planet, e, orbits the star much farther out. They were also able to determine the exact masses of two of the three previously known planets, Upsilon Andromedae c and d. Much more startling, though, is that not all planets orbit this star in the same plane. The orbits of planets c and d are inclined by 30 degrees with respect to each other. This research marks the first time that the “mutual inclination” of two planets orbiting another star has been measured.
“Most probably Upsilon Andromedae had the same formation process as our own solar system, although there could have been differences in the late formation that seeded this divergent evolution,” McArthur said. “The premise of planetary evolution so far has been that planetary systems form in the disk and remain relatively co-planar, like our own system, but now we have measured a significant angle between these planets that indicates this isn’t always the case.”
Until now the conventional wisdom has been that a big cloud of gas collapses down to form a star, and planets are a natural byproduct of leftover material that forms a disk. In our solar system, there’s a fossil of that creation event because all of the eight major planets orbit in nearly the same plane. The outermost dwarf planets like Pluto are in inclined orbits, but these have been modified by Neptune’s gravity and are not embedded deep inside the Sun’s gravitational field.
So what knocked the Upsilon Andromedae system around?
“Possibilities include interactions occurring from the inward migration of planets, the ejection of other planets from the system through planet-planet scattering, or disruption from the parent star’s binary companion star, Upsilon Andromedae B,” McArthur said.
Or, the companion star – a red dwarf less massive and much dimmer than the Sun — could be the culprit. is.
“We don’t have any idea what its orbit is,” said team member Fritz Benedict. “It could be very eccentric. Maybe it comes in very close every once in a while. It may take 10,000 years.” Such a close pass by the secondary star could gravitationally perturb the orbits of the planets.”
The two different types of data combined in this research were astrometry from the Hubble Space Telescope and radial velocity from ground-based telescopes.
Astrometry is the measurement of the positions and motions of celestial bodies. McArthur’s group used one of the Fine Guidance Sensors (FGSs) on the Hubble telescope for the task. The FGSs are so precise that they can measure the width of a quarter in Denver from the vantage point of Miami. It was this precision that was used to trace the star’s motion on the sky caused by its surrounding — and unseen — planets.
Radial velocity makes measurements of the star’s motion on the sky toward and away from Earth. These measurements were made over a period of 14 years using ground-based telescopes, including two at McDonald Observatory and others at Lick, Haute-Provence, and Whipple Observatories. The radial velocity provides a long baseline of foundation observations, which enabled the shorter duration, but more precise and complete, Hubble observations to better define the orbital motions.
The fact that the team determined the orbital inclinations of planets c and d allowed them to calculate the exact masses of the two planets. The new information told us that our view as to which planet is heavier has to be changed. Previous minimum masses for the planets given by radial velocity studies put the minimum mass for planet c at 2 Jupiters and for planet d at 4 Jupiters. The new, exact masses, found by astrometry are 14 Jupiters for planet c and 10 Jupiters for planet d.
“The Hubble data show that radial velocity isn’t the whole story,” Benedict said. “The fact that the planets actually flipped in mass was really cute.”
The fourth planet is so far out, that its signal does not reveal the curvature of its orbit.
The 14 years of radial velocity information compiled by the team uncovered hints that a fourth, long-period planet may orbit beyond the three now known. There are only hints about that planet because it’s so far out that the signal it creates does not yet reveal the curvature of an orbit. Another missing piece of the puzzle is the inclination of the innermost planet, b, which would require precision astrometry 1,000 times greater than Hubble’s, a goal attainable by a future space mission optimized for interferometry.
Artist's concept of the exoplanet WASP-12b -- a hot Jupiter being devoured by its parent star. Artwork Credit: NASA, ESA, and G. Bacon (STScI)
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We all like a hot meal, but this is really bizarre. Back in February, Jean wrote an article about WASP-12b, the hottest known planet in the Milky Way that is being ripped to shreds by its parent star. Shu-lin Li of the Department of Astronomy at the Peking University, Beijing, predicted that the star’s gravity would distort the planet’s surface and make the interior of the planet so hot that the atmosphere would expand out and co-mingle with the star. Shu-lin calculated the planet would one day be completely consumed. Now the Hubble Space Telescope has confirmed this prediction, and astronomers estimate the planet may only have another 10 million years left before it is completely devoured.
Using the Cosmic Origins Spectrograph (COS), and its sensitive ultraviolet instruments, astronomers saw that the star and the planet’s atmosphere share elements, passing them back and forth. “We see a huge cloud of material around the planet, which is escaping and will be captured by the star. We have identified chemical elements never before seen on planets outside our own solar system,” says team leader Carole Haswell of The Open University in Great Britain.
This effect of matter exchange between two stellar objects is commonly seen in close binary star systems, but this is the first time it has been seen so clearly for a planet.
The planet, called WASP-12b, is so close to its sunlike star that it completes an orbit in 1.1 days, and is heated to nearly 1,540 C (2,800 F) and stretched into a football shape by enormous tidal forces. The atmosphere has ballooned to nearly three times Jupiter’s radius and is spilling material onto the star. The planet is 40 percent more massive than Jupiter.
WASP-12 is a yellow dwarf star located approximately 600 light-years away in the winter constellation Auriga.
Haswell and her science team’s results were published in the May 10, 2010 issue of The Astrophysical Journal Letters.
A gallery of six exoplanets that have retrograde orbits (artist concepts). ESO/A. C. Cameron
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Not all exoplanets are created equal, and new discoveries about the orbits of newly found extra solar planets could challenge the current theories of planet formation. The discoveries also suggest that systems with exoplanets of the type known as hot Jupiters are unlikely to contain Earth-like planets. “This is a real bomb we are dropping into the field of exoplanets,” said Amaury Triaud, a PhD student at the Geneva Observatory who led an observational campaign from several observatories.
Six exoplanets out of twenty-seven were found to be orbiting in the opposite direction to the rotation of their host star — the exact reverse of what is seen in our own Solar System. The team announced the discovery of nine new planets orbiting other stars, and combined their results with earlier observations. Besides the surprising abundance of retrograde orbits, the astronomers also found that more than half of all the so-called “hot Jupiters” in their survey have orbits that are misaligned with the rotation axis of their parent stars.
Hot Jupiters are planets orbiting other stars that have masses similar to or greater than Jupiter, but which orbit their parent stars much more closely.
Planets are thought to form in the disc of gas and dust encircling a young star, and since this proto-planetary disc rotates in the same direction as the star itself, it was expected that planets that form from the disc would all orbit in more or less the same plane, and that they would move along their orbits in the same direction as the star’s rotation.
“The new results really challenge the conventional wisdom that planets should always orbit in the same direction as their stars spin,” said Andrew Cameron of the University of St Andrews, who presented the new results at the RAS National Astronomy Meeting (NAM2010) in Glasgow, Scotland this week. Artist’s impression of an exoplanet in a retrograde orbit. Credit: ESO
At this writing, 454 planets have been found orbiting other stars, and in the 15 years since the first hot Jupiters were discovered, astronomers have been puzzled by their origin. The cores of giant planets are thought to form from a mix of rock and ice particles found only in the cold outer reaches of planetary systems. Hot Jupiters must therefore form far from their star and subsequently migrate inwards to orbits much closer to the parent star. Many astronomers believed this was due to gravitational interactions with the disc of dust from which they formed. This scenario takes place over a few million years and results in an orbit aligned with the rotation axis of the parent star. It would also allow Earth-like rocky planets to form subsequently, but unfortunately it cannot account for the new observations.
To account for the new retrograde exoplanets an alternative migration theory suggests that the proximity of hot Jupiters to their stars is not due to interactions with the dust disc at all, but to a slower evolution process involving a gravitational tug-of-war with more distant planetary or stellar companions over hundreds of millions of years. After these disturbances have bounced a giant exoplanet into a tilted and elongated orbit it would suffer tidal friction, losing energy every time it swung close to the star. It would eventually become parked in a near circular, but randomly tilted, orbit close to the star. “A dramatic side-effect of this process is that it would wipe out any other smaller Earth-like planet in these systems,” says Didier Queloz of Geneva Observatory.
The observatories for this survey included the Wide Angle Search for Planets (WASP), the HARPS spectrograph on the 3.6-metre ESO telescope at the La Silla observatory in Chile, and the Swiss Euler telescope, also at La Silla. Data from other telescopes to confirm the discoveries.
