SETI bioastro: FW: Planet-Forming Disks Might Put the Brakes on Stars

From: LARRY KLAES (ljk4_at_msn.com)
Date: Tue Jul 25 2006 - 09:47:31 PDT

  • Next message: LARRY KLAES: "SETI bioastro: FW: Cornell Chronicle: Connecting sound and meaning in words"

    >From: "NASA Jet Propulsion Laboratory" <info_at_jpl.nasa.gov>
    >Reply-To: <info_at_jpl.nasa.gov>
    >Subject: Planet-Forming Disks Might Put the Brakes on Stars
    >Date: Mon, 24 Jul 2006 10:10:30 -0700
    >
    >MEDIA RELATIONS OFFICE
    >JET PROPULSION LABORATORY
    >CALIFORNIA INSTITUTE OF TECHNOLOGY
    >NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
    >PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011
    >http://www.jpl.nasa.gov
    >
    >Whitney Clavin (818) 354-4673
    >Jet Propulsion Laboratory, Pasadena, Calif.
    >
    >News Release: 2006-094 July 24, 2006
    >
    >Planet-Forming Disks Might Put the Brakes on Stars
    >
    >Astronomers using NASA's Spitzer Space Telescope have found evidence that
    >dusty
    >disks of planet-forming material tug on and slow down the young, whirling
    >stars they
    >surround.
    >
    >Young stars are full of energy, spinning around like tops in half a day or
    >less. They would
    >spin even faster, but something puts on the brakes. While scientists had
    >theorized that
    >planet-forming disks might be at least part of the answer, demonstrating
    >this had been
    >hard to do until now.
    >
    >"We knew that something must be keeping the stars' speed in check," said
    >Dr. Luisa
    >Rebull of NASA's Spitzer Science Center, Pasadena, Calif. "Disks were the
    >most logical
    >answer, but we had to wait for Spitzer to see the disks."
    >
    >Rebull, who has been working on the problem for nearly a decade, is lead
    >author of a new
    >paper in the July 20 issue of the Astrophysical Journal. The findings are
    >part of a quest to
    >understand the complex relationship between young stars and their
    >burgeoning planetary
    >systems.
    >
    >Stars begin life as collapsing balls of gas that spin faster and faster as
    >they shrink, like
    >twirling ice skaters pulling in their arms. As the stars whip around,
    >excess gas and dust
    >flatten into surrounding pancake-like disks. The dust and gas in the disks
    >are believed to
    >eventually clump together to form planets.
    >
    >Developing stars spin so fast that, left unchecked, they would never fully
    >contract and
    >become stars. Prior to the new study, astronomers had theorized that disks
    >might be
    >slowing the super speedy stars by yanking on their magnetic fields. When a
    >star's fields
    >pass through a disk, they are thought to get bogged down like a spoon in
    >molasses. This
    >locks a star's rotation to the slower-turning disk, so the shrinking star
    >can't spin faster.
    >
    >To prove this principle, Rebull and her team turned to Spitzer for help.
    >Launched in
    >August of 2003, the infrared observatory is an expert at finding the
    >swirling disks around
    >stars, because dust in the disks is heated by starlight and glows at
    >infrared wavelengths.
    >
    >The team used Spitzer to observe nearly 500 young stars in the Orion
    >nebula. They
    >divided the stars into slow spinners and fast spinners, and determined that
    >the slow
    >spinners are five times more likely to have disks than the fast ones.
    >
    >"We can now say that disks play some kind of role in slowing down stars in
    >at least one
    >region, but there could be a host of other factors operating in tandem. And
    >stars might
    >behave differently in different environments," Rebull said.
    >
    >Other factors that contribute to a star's winding down over longer periods
    >of time include
    >stellar winds and possibly full-grown planets.
    >
    >If planet-forming disks slow down stars, does that mean stars with planets
    >spin more
    >slowly than stars without planets? Not necessarily, according to Rebull,
    >who said slowly
    >spinning stars might simply take more time than other stars to clear their
    >disks and
    >develop planets. Such late-blooming stars would, in effect, give their
    >disks more time to
    >put on the brakes and slow them down.
    >
    >Ultimately, the question of how a star's rotation rate is related to its
    >ability to support
    >planets will fall to planet hunters. So far, all known planets in the
    >universe circle stars
    >that turn around lazily. Our sun is considered a slowpoke, currently
    >plodding along at a
    >rate of one revolution every 28 days. And, due to limits in technology,
    >planet hunters
    >have not been able to find any extrasolar planets around zippy stars.
    >
    >"We'll have to use different tools for detecting planets around rapidly
    >spinning stars, such
    >as next-generation ground and space telescopes," said Dr. Steve Strom, an
    >astronomer at
    >the National Optical Astronomy Observatory, Tucson, Ariz.
    >
    >Other members of Rebull's team include Drs. John Stauffer of the Spitzer
    >Science Center;
    >S. Thomas Megeath at the University of Toledo, Ohio; and Joseph Hora and
    >Lee
    >Hartmann of the Harvard-Smithsonian Center for Astrophysics, Cambridge,
    >Mass.
    >Hartmann is also affiliated with the University of Michigan, Ann Arbor.
    >
    >NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer
    >Space
    >Telescope mission for NASA's Science Mission Directorate, Washington.
    >Science
    >operations are conducted at the Spitzer Science Center at the California
    >Institute of
    >Technology. Caltech manages JPL for NASA.
    >
    >For an animation depicting how disks slow stars and more information about
    >Spitzer,
    >visit www.spitzer.caltech.edu/spitzer .
    >
    >-end-
    >
    >
    >
    >
    >To remove yourself from all mailings from NASA Jet Propulsion Labratory,
    >please go to http://www.kintera.org/TR.asp?ID=M718344795955433631724165


  • Next message: LARRY KLAES: "SETI bioastro: FW: Cornell Chronicle: Connecting sound and meaning in words"

    This archive was generated by hypermail 2.1.6 : Tue Jul 25 2006 - 09:51:27 PDT