A team of astronomers has captured a photo of an extrasolar planet in the making.
Left: composite image of the young planetary system LkCa 15. Right: zoomed in composite image of LBT and Magellan observations, with LkCa 15b, c, and d marked. Image credit: Stephanie Sallum et al.
The exoplanet in question is LkCa 15b. It was discovered in 2011 by astronomers Adam Kraus and Michael Ireland using the Keck II telescope.
LkCa 15b resides in a young, three-planet system called LkCa 15, approximately 450 light-years away in the constellation Taurus.
The system also contains two other planets, LkCa 15c and LkCa 15d, and a special kind of protoplanetary disk with a gap.
According to astronomers, such protoplanetary disks form around young stars using the debris left over from the star’s formation.
It is suspected that planets then form inside the disk, sweeping up dust and debris as the material falls onto the planets instead of staying in the disk or falling onto the star. A gap is then cleared in which planets can reside.
“Our new observations support that view. We are just now being able to image objects that are close to and much fainter than a nearby star,” said team member Stephanie Sallum, a Ph.D. student in astronomy at the University of Arizona and lead author of a paper in the journal Nature.
“That’s because of astronomers at the University of Arizona (UA) who have developed the instruments and techniques that make that difficult observation possible.”
Sallum and co-authors observed LkCa 15b and two other planets in the system using the 8.4-m Large Binocular Telescope on Mount Graham in Arizona and the UA’s Magellan Telescope in Chile.
“We report adaptive optics observations of LkCa 15 that probe within the disk clearing. With accurate source positions over multiple epochs spanning 2009-2015, we infer the presence of multiple companions on Keplerian orbits,” the astronomers wrote in the Nature paper.
“We directly detect Hα emission from the innermost companion, LkCa 15b, evincing hot (about 10,000 K) gas falling deep into the potential well of an accreting protoplanet.”
“This is the first time that we’ve imaged a planet that we can say is still forming,” Sallum said.
“Results like this have only been made possible with the application of a lot of very advanced new technology to the business of imaging the stars. And it’s really great to see them yielding such impressive results,” added co-author Prof. Peter Tuthill of the University of Sydney.
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Stephanie Sallum et al. 2015. Accreting protoplanets in the LkCa 15 transition disk. Nature 527, 342-344; doi: 10.1038/nature15761
