Pictures offer rare glimpse of planets
A little more of the universe has been pried out of the shadows.
Two groups of astronomers have taken the first pictures of what they say – and other astronomers agree – are most likely planets going around other stars.
The achievement, the result of years of effort on improved observational techniques and better data analysis, presages more such discoveries, the experts said, and will open the door to discoveries of what planets are and how they came to be formed.
“It's the tip of the iceberg,” said Christian Marois of the Herzberg Institute of Astrophysics in Victoria, British Columbia. “Now that we know they are there, there is going to be an explosion.”
Marois is the leader of a team that recorded three planets circling a star known as HR 8799 that is 130 light-years away in the constellation Pegasus. The other team, led by Paul Kalas of the University of California Berkeley, found a planet orbiting the star Fomalhaut, only 25 light-years from Earth, in the constellation Piscis Austrinus.
In an interview by e-mail, Kalas said that when he confirmed his discovery in May, “I nearly had a heart attack.”
In scratchy telescope pictures released yesterday in Science Express, the online version of the journal Science, the planets appear as fuzzy dots that move slightly around their star from exposure to exposure. Astronomers who have seen the new images agreed that these looked like the real thing.
“I think (17th-century German astronomer Johannes) Kepler himself would recognize these as planets orbiting a star following his laws of orbital motion,” Mark Marley of the Ames Research Center in Mountain View wrote in an e-mail message elaborating on HR 8799.
More than 300 extrasolar planets have been found circling distant stars, making their discovery the hottest and fastest growing field in astronomy. But the observations have been made mostly indirectly, by dips in starlight as planets cross in front of their home star or by wobbles they induce going by it.
Astronomers being astronomers, they want to see these worlds, but a few recent claims of direct observations have been clouded by debates about whether the bodies were really planets or failed stars.
“Every extrasolar planet detected so far has been a wobble on a graph,” said Bruce Macintosh, an astrophysicist from Lawrence Livermore National Laboratory and a member of Marois' team. “These are the first pictures of an entire system.”
The new planetary systems are anchored by young bright stars more massive than our own sun and swaddled in large disks of dust, the raw material of worlds.
The three planets orbiting HR 8799 are roughly 10, nine and six times the mass of Jupiter, and orbit their star in periods of 450, 180 and 100 years respectively, all counterclockwise.
The Fomalhaut planet is about three times as massive as Jupiter, according to Kalas' calculations, and is on the inner edge of a huge band of dust, taking 872 years to complete a revolution of its star.
Both systems appear to be scaled-up versions of our own solar system, with giant planets in the outer reaches, leaving plenty of room for smaller planets to lurk undetected in the warmer inner regions. Dust rings lie even farther out, like the Kuiper belt of icy debris extending beyond the orbit of Neptune.
“This is a window into what our own solar system might have looked like when it was 60 million years old,” Marois said.
The new images are the fruits of a long campaign by astronomers to see more and more of the unseeable. In particular, it is a triumph for the emerging technology of adaptive optics in which telescope mirrors are jiggled and warped slightly many times a second to compensate for the atmospheric turbulence that blurs star images.
The problem in seeing other planets is picking them out of the glare of their parent stars, which are millions of times brighter, at least in visible light. As a result, planet hunters usually look for infrared, or heat radiation, which is emitted copiously by planets still shedding heat from the process of formation.
For their observations, Marois and his colleagues used the 8-meter-in-diameter Gemini North and the 10-meter Keck telescopes on Mauna Kea in Hawaii, both of which had been fitted with adaptive optics. Then, they processed the images with a special computer program.
By Dennis Overbye NEW YORK TIMES NEWS SERVICE
November 14, 2008
