Formation of Rocky Planets
Worlds, with potential for life, might be more common place than previously thought. Astronomers have come to this conclusion after discovering that terrestrial planets might form around several of the nearby sun-like stars in our galaxy. Using NASA’s Spitzer Space Telescope, the University of Arizona Tucson, astronomer Michael Meyer and his colleagues worked to determine if planetary systems like ours are common or rare in our Milky Way galaxy.
At least 20%, with possibly as many as 60% of stars similar to the sun, are candidates for forming rocky planets, with six sets of stars were surveyed by astronomers using Spitzer. The stars were grouped depending on their age with masses comparable to our sun. The sun is about 4.6 billion years old. “We wanted to study the evolution of the gas and dust around stars similar to the sun and compare the results with what we think the solar system looked like at earlier stages during its evolution,” Meyer said.
During the study, the Spitzer telescope detected dust - - the rubble left over from collisions as planets form - - at a range of infrared wavelengths. The hottest dust is detected at the shortest wavelength, which is between 3.6 microns and 8 microns. Cool dust is detected at the longest wavelength, between 70 microns and 160 microns. Warm dust can be traced at 24 - micron wavelengths.
Because dust closer to the star is hotter than dust farther from the star, the “warm” dust likely traces material orbiting the star at distances comparable to the distance between Earth and Jupiter. “We found that about 10 to 20 % of the stars in each of the four youngest age groups shows 24 - micron emission due to dust,” Meyer said. “But we don’t see warm dust around stars older than 300 million years. The frequency just drops off.”
Data suggests that Earth formed over 10 to 50 million years from collisions between smaller bodies. Other observations suggest that whatever led to the Earth’s formation could be occurring around many stars, between three million and 300 million years old. Kenyon and Ben Bromley of the University of Utah, Salt Lake City, are developing planet formation models that predict that warm dust would be detected at 24 - micron wavelengths as small rocky bodies collide and merge. “Our work suggests that the warm dust is a natural outcome of rocky planet formation. We predict a higher frequency of dust emissions for the younger stars, just as Spitzer observes,” said Kenyon. The next critical test of the assertion that terrestrial planets like Earth could be common around stars like the sun will come next year with the launch of NASA’s Kepler mission.
This entry was posted on Friday, February 22nd, 2008 at 11:47 pm and is filed under Space Agency News. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
