Discovery of oldest planet suggests we are not alone
Date: Saturday, July 12 2003
Topic: Science & Technology
Canadian and U.S. astronomers have discovered a primeval planet that is almost as old as the universe itself, a discovery that suggests there are far more planets out there than scientists ever imagined.
The 13-billion-year-old planet is more than twice as old as Earth and other known planets. It is so ancient, scientists have taken to calling it the "Methuselah" planet.
The discovery indicates planets have been forming much longer than previously believed, and in parts of the universe where scientists never expected to find them.
"It probably means that planets are really quite ubiquitous," said Harvey Richer, a professor at the University of British Columbia and a member of the team that details the find in the journal Science released today.
"They are much more common than we could have expected and that argues very well for life elsewhere in the universe."
In recent years, researchers have found more than 100 extra-solar planets outside the solar system. None of them are believed to be more than five or six billion years old.
Alan Boss, a leading planetary scientist at Carnegie Institution, called the discovery "a stunning revelation." Not only is it the oldest and most distant planet ever found, but it is the only one known to orbit two stars.
"This is a whole new paradigm that we are getting into," Dr. Richer said.
The planet is 2 1/2 the mass of Jupiter and about 5,600 light years away.
He and his co-authors are the toast of the astronomical world this week. Dr. Richer will give a special lecture on the discovery at the American Museum of National History today. He and lead scientist Steinn Sigurdsson of Pennsylvania State University held a press conference at NASA headquarters in Washington yesterday, complete with animation of what the planet might look like and the wild ride it has had through time.
When it was born it probably orbited its youthful sun at approximately the same distance Jupiter is from our sun. It has survived blistering ultraviolet radiation, supernova explosions and shockwaves.
The planet was formed out of primeval gases swirling around a star when the universe was just a billion years old. The scientists believe the next 10 billion years were fairly uneventful. Then, the planet and its parent star were captured by the gravity of another star system. In the ensuing tussle, the planet and its star got jostled around and the planet ended up orbiting around two stars.
One of the stars is observed as a pulsar by radio telescopes, but the other had not been seen until now. The research team used data from NASA's Hubble Space Telescope to precisely measure the second star, and this let them nail down the properties of the planet as well.
While the planet is too far away to be seen, the scientists say there is no question it exists, based on their observations of the stars. The scientists infer the planet is there by observing the wobble in the signals from the stars, caused by the gravitational tugs between the planet and its two stars.
"There is no doubt it is there; the signal is so strong," Dr. Richer said in a telephone interview.
The gaseous planet, located in a globular cluster called M4, is so far from its stars there is little chance it harbours life. "It's gonna be bloody cold out there," Dr. Richer said.
But because its first 10 billion years were spent around a sun-like star, the astronomers speculate that it might have had an Earth-like moon or neighbour. A place, said Dr. Boss, "where life could have arisen and died out long ago, long before we came along to the galactic party."
Dr. Boss said the discovery of the ancient planet has "immense astrobiological implications."
The discovery challenged a widely held view among astrophysicists that planets could not have originated so early because the universe had yet to generate enough of the heavy elements needed to make them.
The sun and its planetary system are about 4.6 billion years old, products of what astronomers call the third generation of stars. By that time, the gas and dust of interstellar space was richer in heavy elements. In less than a decade, astronomers have discovered planets around more than 100 sun-like stars in the Milky Way, Earth's home galaxy.
Source: CanWest News Service, with files from The New York Times