Planets may assemble around stars more quickly than anyone thought possibleDecember 23rd, 2009 - 3:15 pm ICT by ANI
Washington, December 23 (ANI): An international team of astronomers has said that two brown dwarf-sized objects orbiting a giant old star show that planets may assemble around stars more quickly and efficiently than anyone thought possible.
The researchers were from the Torun Center for Astronomy, Poland and the Center for Exoplanets and Habitable Worlds, Penn State, US.
“We have found two brown dwarf-sized masses around an ordinary star, which is very rare,” said Alex Wolszczan, Evan Pugh professor of astronomy and astrophysics, Penn State and lead scientist on the project.
The star, BD +20 2457, is a K2 giant - an old bloated star nearing the end of its life.
Seeing a pair of brown dwarfs around a K-type giant is a first for astronomers and offers a unique window into how they can be produced.
Brown dwarfs are dim, elusive objects that straddle the dividing line between planets and stars.
They are too massive to be planets, but not massive enough to generate the fusion-powered energy of a star.
These stellar cousins represent a kind of “missing link” between planets and stars, but little is known about how they are made.
“If we find one brown dwarf, we are not sure where it came from. It could be either from the process of planet formation or it could be a direct product of star formation,” Wolszczan explained.
Seeing two of them around a parent star means they must have originally formed from the enormous supply of raw materials that surrounded the star when it was young.
Astronomers call this thick, solar system-sized pancake of gas and dust the “circumstellar disk.”
“If that is the case, then if we add up the minimum masses of these two objects, we know the disk had to be extremely massive,” said Wolszczan.
Several million years ago, BD +20 2457 was on the “main sequence,” the stage in stellar evolution where the star produced light by burning its hydrogen fuel, much like our sun does now.
Except this star, three times the mass of the sun, was much hotter and more luminous.
“The intense radiation of this star would have heated up and evaporated anything that was still forming around it,” Wolszczan said.
“The fact that these dwarfs are still here means that they had to accumulate a lot of material very quickly and be fully formed by the time the star’s switched on,” he added. (ANI)
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Tags: alex wolszczan, astronomers, astronomy and astrophysics, brown dwarfs, dividing line, elusive objects, enormous supply, exoplanets, habitable worlds, hydrogen fuel, main sequence, missing link, old star, ordinary star, parent star, planet formation, planets and stars, star formation, star show, stellar evolution