Planet caught in process of forming
University of Hawaiʻi astronomer Adam Kraus and an Australian colleague have captured the first direct image of a planet in the process of forming around its star.
Kraus presented the discovery Oct. 19 at a meeting at NASA’s Goddard Space Flight Center after acceptance of a research paper by the Astrophysical Journal describing the young gas giant being built out of dust and gas.
What astronomers are calling LkCa 15 b appears to be a Jupiter-sized gas protoplanet surrounded by a swath of cooler dust and gas that is falling into the still forming planet located inside a wide gap between the young parent star and an outer disk of dust.
“LkCa 15 b is the youngest planet ever found, about five times younger than the previous record holder,” said Kraus. “For the first time, we’ve been able to directly measure the planet itself as well as the dusty matter around it.”
Kraus, an Institute for Astronomy postdoctoral researcher, and Michael Ireland, of Macquarie University and the Australian Astronomical Observatory, combined the power of the 10-meter Keck telescopes with a bit of optical sleight of hand.
The astronomers combined the power of Keck’s adaptive optics with a technique called aperture mask interferometry. Adaptive optics uses a deformable mirror to rapidly correct for atmospheric distortions of starlight. Interferometry uses a small mask with several holes to manipulate the light waves collected by a large telescope.
“It’s like we have an array of small mirrors,” explained Kraus. The technique allows the astronomers to cancel out the bright light of stars, and then resolve disks of dust around stars and see gaps in the dusty layers where protoplanets may be hiding.
Interferometry has been around since the 1800s, but only in recent years coupled with adaptive optics to view nearby young stars. “We’ve been trying to push the technique to its limits using the biggest telescopes in the world, especially Keck” on Mauna Kea, said Ireland.
After surveying 150 young dusty stars in star-forming regions, the astronomers concentrated on a dozen stars. “LkCa 15 was only our second target, and we immediately knew we were seeing something new,” said Kraus.
Investigation of a faint point source near the star at varying wavelengths revealed a super Jupiter-sized gas planet and allowed the researchers to measure the dust and gas surrounding it.
“We’d found a planet at its very beginning,” said Kraus, who plans to continue observating LkCa 15 and other nearby young stars with Ireland to construct a clearer picture of how planets and solar systems form.