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New exoplanet too big for its star – how did it get there?
Eric Hopton for redOrbit.com – Your Universe Online
A great combination of observations by an amateur Ozzie astronomer and the world’s largest telescope in Chile have confirmed the existence of a strange “puffed up” planet.
The new exoplanet appears to be just too big for its star and it’s got the astronomers frantically scratching their heads.
This odd body is orbiting very close to a small, cool star 500 light years away and is challenging our ideas about how planets form.
Where did it come from?
“We have found a small star, with a giant planet the size of Jupiter, orbiting very closely. It must have formed further out and migrated in, but our theories can’t explain how this happened,” said researcher George Zhou from the Research School of Astrophysics and Astronomy (RSAA).
Astronomers have found more than 1,800 extrasolar planets (exoplanets) in the last twenty years. But this one is different.
Its host star is HATS-6, an M-dwarf, one of the most numerous types of stars in galaxy. M-dwarf stars may be common, but we know little about them. They are cool and dim. HATS-6 emits only one twentieth of the light of our sun, and this lack of light makes M-dwarf stars hard to study.
Observations by small robotic telescopes, including those at the ANU Siding Spring Observatory, revealed a dip in the HATS-6’s brightness as the planet passed in front of the star.
That’s a great Tan
The ANU called in help from one of the world’s largest telescopes, the Magellan Telescope in Chile, and amateur astronomer, T. G. Tan, who operates from his backyard in Perth.
“T. G. Tan has been really helpful on our projects. He was able to catch the transit of the planet from Perth, after it had set over our horizon,” said Zhou.
Subsequent observations confirmed the planet had an orbit of just one-tenth that of Mercury. It orbits HATS-6 every 3.3 days.
“The planet has a similar mass to Saturn, but its radius is similar to Jupiter, so it’s quite a puffed up planet. Because its host star is so cool, it’s not heating the planet up so much. It’s very different from the planets we have observed so far. The atmosphere of this planet will be an interesting target for future study,” added Zhou.
The results of the study are published in The Astronomical Journal.
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Source: http://www.redorbit.com/news/space/1113383230/new-exoplanet-too-big-for-its-star-%e2%80%93-how-did-it-get-there-050315/
