October 20, 2011
Forming Planet Captured By Astronomer
A University of Hawaii astronomer is credited with capturing the first direct image of a planet in the process of being formed around its star, reports the Associated Press (AP).
Astronomer Adam Kraus, from UH at Manoa, made the discovery using the twin 10-meter Keck telescopes on Mauna Kea. He also used mirrors to cancel out starlight to view the phenomenon, a technique called aperture mask interferometry. It is usually impossible to capture such planetary births because the parent star´s light is too bright and outshines them.
The planet, named LkCa 15 b, looks like a hot “protoplanet” surrounded by a shroud of cooler dust and gas, which is falling into the still-forming planet. Images revealed that the planet sits inside a wide gap between the young parent star and an outer disk of dust.
Kraus said the planet is being formed around a young, 2-million-year-old star about 450 light years from Earth. The planet, based on scientific models of how planets form, is estimated to have started taking shape between 50,000 and 100,000 years ago. When it is done forming, it will be a gas giant, similar to Jupiter.
LkCa 15 b is now the youngest planet ever observed. The previous youngest planet observed was about 5 times older than this one, said Kraus, who made the discovery with the help of his Australian colleague, Ireland .
“We´re catching this object at the perfect time. We see this young star, it has a disc around it that planets are probably forming out of and we see something right in the middle of a gap in the disc,” Kraus told AP's Audrey McAvoy in a telephone interview.
Kraus presented his discovery Wednesday at NASA´s Goddard Space Flight Center in Maryland. He and Ireland´s research paper on the discovery will be published in an upcoming issue of The Astrophysical Journal.
The discovery of LkCa 15 b started out as a survey of 150 young stars in star-forming regions. They narrowed that search down to a more concentrated study of about a dozen stars.
“LkCa 15 was only our second target, and we immediately knew we were seeing something new,” Kraus said in a press release. “We could see a faint point source near the star, so thinking it might be a Jupiter-like planet we went back a year later to get more data.”
With further investigation at varying wavelengths, the astronomers were fascinated that the phenomenon was more complex than a single companion object.
“We realized we had uncovered a super Jupiter-sized gas planet, but that we could also measure the dust and gas surrounding it. We had found a planet at its very beginning,” said an excited Kraus.
Kraus and Ireland plan to continue their observations of LkCa 15 b and other nearby stars in their efforts to construct a clearer image of how planets form.
Observing planets in the forming stages of life can help scientists answer questions like whether planets form early in the life of a star or later, and whether they form relatively close to stars or farther away.
Planets have been known to change orbits after forming, so it is difficult to answer such questions by studying older planets.
“These very basic questions of when and where are best answered when you can actually see the planet forming, as the process is happening right now,” said Kraus.
Image Caption: Artist´s conception of the area near the planet LkCa 15 b. Click on picture for larger view. Credit: Karen L. Teramura, UH IfA.
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