Interstellar dust bunnies in Taurus: Baby steps toward new planets?

University of Hawaiʻi
Posted: Jan 9, 2006

Astronomers at the University of Hawaii today presented new evidence at the national meeting of the American Astronomical Society in Washington, DC, for the first steps in the formation of new planets from tiny dust particles in orbit around young stars like the Sun.

Using sensitive radio cameras on two telescopes, the 15-m James Clerk Maxwell Telescope (JCMT) and 10-m Caltech Submillimeter Observatory (CSO), at Mauna Kea Observatories in Hawaii, graduate student Sean Andrews and Dr. Jonathan Williams of the Institute for Astronomy examined the swirling disks of gas and dust that surround young stars in the Taurus region of the sky to determine how the dust changes as disks evolve. They found that the disks rapidly disappear and concluded that stars have only a few million years to get started on making planets, a far shorter time than conventional theories require.

"We expected that disks would not disappear so quickly at radio wavelengths," said Andrews, "but this was not the case in general. The dust is either being dispersed, dumped onto the star, or growing into large clumps that are difficult to detect." On a scale in which a typical star's 10-billion-year lifetime is compressed to the average human lifespan, the disks would disappear within the first week.

Previous work at shorter, infrared wavelengths had shown that the innermost regions of disks disappear rapidly, but it was thought that the outer parts, where the planets in our solar system reside and which are most visible at longer, radio wavelengths, would last substantially longer.

The work, which is published in The Astrophysical Journal and funded by the National Science Foundation (NSF) and NASA, also showed that the dust around the stars emits more efficiently at longer wavelengths as the disks evolve.

"This suggests that the dust particles are sticking together, much as dust bunnies form under a bed," said Williams. He added, "This is the first, albeit tiny, step toward forming new solar systems."

The observations were made at a range of frequencies from 350 GHz to 860 GHz, in three relatively transparent windows in the sky, which allow the total mass of the planet-forming region in the disks to be measured.

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