University of Arizona grad student discovers the UA's first exoplanet

2013-12-07T00:00:00Z University of Arizona grad student discovers the UA's first exoplanetBy Tom Beal Arizona Daily Star Arizona Daily Star

A graduate student at the UA’s Steward Observatory has discovered a planet that orbits its host star at a distance that defies accepted notions of planetary formation.

In April of this year, Vanessa Bailey, a doctoral candidate with the University of Arizona Department of Astronomy, discovered a hot, giant gas ball about the diameter of Jupiter and 11 times its mass.

It is 20 times farther from its host star than Neptune is from our sun.

Its location was so unexpected that the first time she found it in her data, “We all said that can’t be a planet.”

Bailey consulted previous imaging of that same star and found a Hubble Space Telescope record of it. It had not been recognized as a planet at the time.

Bailey was observing on the 6.5-meter Clay Magellan Telescope in Chile that had just been outfitted with an adaptive optics system to counter the blurring effect of Earth’s atmosphere. It provided images as clear as those taken from space.

Laird Close, principal investigator for the adaptive optics system, nicknamed Mag-AO, said Bailey was given time on the telescope as a reward for her help in commissioning one of the two cameras employed in the system.

“Normally you discover nothing on a commissioning run, but she wanted to observe this one star that she thought had a planet around it,” Close said.

The star was nowhere near to where Bailey thought it would be. She had selected the star because it had a disk of dust around it with gaps that might indicate the presence of a planet.

Instead she found a planet far from the dust disk in an orbit that will probably take it 10,000 Earth years to circle its host. It was a fairly new planet, 13 million years old, and still radiating heat from its formation.

That made it easily visible to Clio, the infrared camera she was helping to commission.

“Nobody has ever found any planet orbiting this distantly from a sunlike star,” Bailey said.

She said her planet, named HD 106906, is one of “a growing population of these weird oddball objects” that are challenging accepted notions of how planets form from debris disks of dust and gas surrounding new stars.

This planet is too far away to fit that model, said Bailey.

Bailey said she was able to convince the team, using Hubble evidence, that the planet was worth a second look and was given another turn at the telescope on the last night of its commissioning operations.

“That is why I came to Arizona for grad school,” she said. “We have some of the world’s very best facilities and they let grad students play around with them.”

Contact reporter Tom Beal at tbeal@azstarnet.com or 573-4158.

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