Space Odyssey: UH astronomer captures image of planet in process of forming - Ka Leo O Hawaii: NEWS

Space Odyssey: UH astronomer captures image of planet in process of forming

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Posted: Sunday, November 6, 2011 4:14 pm

University of Hawai‘i at Mānoa astronomer Adam Kraus has taken the first direct image of a planet in the process of forming around its star. Kraus and Michael Ireland of Macquarie University and the Australian Astronomical Observatory worked together to find the planet, which may help to answer questions about early planet formation.

"Astronomers have found hundreds of planets over the past 15 years, but almost all of them orbit older stars. ... Until now, we've had no direct evidence for answering even very basic questions," wrote Kraus in an email interview.

This discovery began with a simple study of over 100 forming planets in what are called star-forming regions of the universe, which was narrowed to a particular dozen clustered together. Further investigations led to the discovery of a forming Jupiter-like planet.

The forming planet is named LkCa 15 b. It is the youngest ever found, and formed 50,000 to 100,000 years ago. The scientists have been able to measure the planet, as well as the dust cloud surrounding it.

Kraus presented the discovery on Oct. 19 at a conference at the NASA Goddard Space Flight Center.

Kraus and Ireland used a 10-meter Keck telescope and two techniques to spot the orb.

"Mauna Kea is one of the best sites in the world for building telescopes, and it's been tremendously important for astronomy over the past several decades. One immediate benefit is that the mountain's summit is very high, which places the telescopes above much of the Earth's atmosphere. The atmosphere tends to blur out the light that reaches our telescope, plus it can block some kinds of light entirely, so this is a big advantage.

"The altitude also means that the summit is usually higher than the clouds. This advantage gives telescopes on Mauna Kea better resolution than almost any other site on the planet. In order to find a better site, you have to go to Antarctica," said Kraus.

Because Earth's atmosphere "smears out the light" in the universe, Kraus and Ireland first used a strategy called adaptive optics.

"This technique uses a separate camera to measure how the atmosphere distorts light from a star. The light from our telescope is then reflected off a mirror that is constantly changing its shape in order to cancel those distortions," explained Kraus.

The other technique Kraus and Ireland used is called aperture-mask interferometry. This helps cast out light that is disrupting normal observation.

"This technique actually starts by throwing away most of the light. We use a mask to only allow through a little of the light that's landing in the telescope, through a carefully chosen set of small holes. Instead of a single big mirror, the telescope then is more like an array of small telescopes. We can manipulate the light from each of these small ‘telescopes' to cancel most of the remaining distortions introduced by the atmosphere.

"The key here is that by removing as much distortion of the light as possible, we can identify faint planets close to their bright parent stars (so close that previous techniques couldn't reach them)," said Kraus.

Observations of the planet's formation will help answer questions on how stars and planets are born. This has been a goal in astronomy for a long time.

Questions like where and when planets form can now be studied, and these observations can lead to information about the universe. Astronomers will focus on questions like how many years a nascent planet takes to assemble, if the process occurs directly after the star forms, and if it's possible to know the age of a star and its planets.

"Different theories of planet formation make very different predictions," concluded Kraus. "It might be dangerous to try distinguishing between these theories based on just one planet, but hopefully we can do it with a few more."

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