VOA常速英语2008年-Star's Dust Shows Signs of Possible Planet Form

Astronomers 1 have captured an image that suggests evidence of a planet in the early stages of formation.  From VOA's New York Bureau, Mona Ghuneim reports on this discovery that has opened a new window onto our endless search for understanding of that final frontier.

Scientists are one step closer to understanding how new planets evolve.  A recent image of gas and dust circling a star in the constellation 2 Auriga shows material that may be forming into a planet. 

A group of astrophysicists, led by Ben Oppenheimer at the American Museum of Natural History in New York, has detected a gap in the disk surrounding a well-studied star called AB Aurigae. 

According to the scientists, it appears that an object between five and 37 times the mass of the planet Jupiter is forming around this star.  AB Aurigae is one to 3 million years of age and around 470 light years away, considered in astronomy to be both young and nearby in relation to the Earth.   

While Oppenheimer cannot confirm yet that this is a planet in the making, he says this discovery is in line with scientific theory on planet formation. 

"The structure that we've imaged here seems to indicate or at least is very similar to theories of what happens to dust in these disks when a planet actually is forming," he said.  "The planet will perturb 3 the distribution of this dust and make it accumulate in certain areas which we seem to be seeing and also for the disk to have deficits 4 in certain areas which we also observed."

Whatever it is, says Oppenheimer, it is an intriguing 5 observation and can shed more light on the field of exoplanetary science, the study of planets orbiting stars other than the sun.

Oppenheimer says he and his group used a coronagraph developed by the museum to basically filter out the extreme light of the star in order to view the stellar disk.  The device was attached to a US Air Force telescope on the island of Maui in the state of Hawaii.

Sasha Hinkley is a Columbia University graduate student in astrophysics and one of the scientists on Oppenheimer's team.  He says that the result is a big step in an attempt to directly photograph existing and forming planets, but that there is still a lot of work to be done.  He is urging caution about calling the discovery a planet as this is an early observation of a solar system. 

"We do need to be careful.  This is an extremely challenging task, because we're really at the forefront of detecting something extremely faint around a star," he explained.  "We're talking about something that's roughly 100,000 times fainter than the star so we're really at the threshold of what is possible for human beings to do."

Julian Christou is an astrophysicist and program officer at the National Science Foundation, a government agency that partially 6 funded this project.

Christou says that up until the past ten years, there was no evidence to suggest that we were not the only solar system.  But in that time, scientists developed an indirect technique, called spectroscopy, which showed proof of other planets.  These 150 or so planets that have been discovered, he says, have not been seen, but rather detected by the effect of their motion around other stars. 

Christou says this new discovery by the team made up of museum, university, independent and government scientists could help answer some big questions.

"Here for the first time we actually see what happens in an early solar system, how our solar system may have looked, by analogy, three billion/four billion years ago, how did the planets surrounding our sun form, and of course one of those planets is the Earth," he said.  "So how did the Earth form? Where did it come out of?"

The scientists say more aggressive study and advanced technology will follow.  Oppenheimer admits that the ultimate goal of this sort of research is to find an object like Earth and then look for signs of biological activity on it.