[meteorite-list] Dustiest Star Could Harbor a Young Earth

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed Jul 20 16:43:19 2005
Message-ID: <200507202042.j6KKgIr16938_at_zagami.jpl.nasa.gov>

Gemini Observatory
Hilo, Hawaii

Media Contact:
Peter Michaud
Gemini Observatory, Hilo HI
(808) 974-2510 (Office)

Science Contact:
Inseok Song
Gemini Observatory, Hilo HI
(808) 974-2609 (Office)

For Embargoed Release at 1:00pm (ET)/7:00am (HST) on July 20, 2005

Dustiest Star Could Harbor a Young Earth

A relatively young star located about 300 light-years away is greatly
improving our understanding of the formation of Earth-like planets.

The star, going by the unassuming name of BD +20 307, is shrouded by the
dustiest environment ever seen so close to a Sun-like star well after its
formation. The warm dust is believed to be from recent collisions of rocky
bodies at distances from the star comparable to that of the Earth from the
Sun. The results were based on observations done at the Gemini and W.M.
Keck Observatories, and were published in the July 21 issue of the British
science journal Nature.

This finding supports the idea that comparable collisions of rocky bodies
occurred early in our solar system's formation about 4.5 billion years
ago. Additionally, this work could lead to more discoveries of this sort
which would indicate that the rocky planets and moons of our inner solar
system are not as rare as some astronomers suspect.

"We were lucky. This set of observations is like finding the proverbial
needle in the haystack," said Inseok Song, the Gemini Observatory
astronomer who led the U.S.-based research team. "The dust we detected is
exactly what we would expect from collisions of rocky asteroids or even
planet-sized objects, and to find this dust so close to a star like our
Sun bumps the significance way up. However, I can't help but think that
astronomers will now find more average stars where collisions like these
have occurred."

For years, astronomers have patiently studied hundreds of thousands of
stars in the hopes of finding one with an infrared dust signature (the
characteristics of the starlight absorbed, heated up and reemitted by the
dust) as strong as this one at Earth-to-Sun distances from the star. "The
amount of warm dust near BD+20 307 is so unprecedented I wouldn't be
surprised if it was the result of a massive collision between planet-size
objects, for example, a collision like the one which many scientists
believe formed Earth's moon," said Benjamin Zuckerman, UCLA professor of
physics and astronomy, member of NASA's Astrobiology Institute, and a
co-author on the paper. The research team also included Eric Becklin of
UCLA and Alycia Weinberger formerly at UCLA and now at the Carnegie
Institution.

BD +20 307 is slightly more massive than our Sun and lies in the
constellation Aries. The large dust disk that surrounds the star has been
known since astronomers detected an excess of infrared radiation with the
Infrared Astronomical Satellite (IRAS) in 1983. The Gemini and Keck
observations provide a strong correlation between the observed emissions
and dust particles of the size and temperatures expected by the collision
of two or more rocky bodies close to a star.

Because the star is estimated to be about 300 million years old, any large
planets that might orbit BD +20 307 must have already formed. However, the
dynamics of rocky remnants from the planetary formantion process might be
dictated by the planets in the system, as Jupiter did in our early solar
system. The collisions responsible for the observed dust must have been
between bodies at least as large as the largest asteroids present today in
our solar system (about 300 kilometers across). "Whatever massive
collision ocurred, it managed to totally pulverize a lot of rock," said
team member Alycia Weinberger.

Given the properties of this dust, the team estimates that the collisions
could not have occurred more than about 1,000 years ago. A longer history
would give the fine dust (about the size of cigarette smoke particles)
enough time to be dragged into the central star.

The dusty environment around BD +20 307 is thought to be quite similar,
but much more tenuous than what remains from the formation of our solar
system. "What is so amazing is that the amount of dust around this star is
approximately one million time greater than the dust around the Sun," said
UCLA team member Eric Becklin. In our solar system the remaining dust
scatters sunlight to create an extremely faint glow called the zodiacal
light (see image above). It can be seen under ideal conditions with the
naked eye for a few hours after evening or before morning twilight.

The team's observations were obtained using Michelle, a mid-infrared
spectrograph/imager built by the UK Astronomy Technology Centre, on the
Frederick C. Gillette Gemini North Telescope, and the Long Wavelength
Spectrograph (LWS) at the W.M. Keck Observatory on Keck I.

For a wide assortment of astronomical images and other publication quality
images of the Gemini telescopes see the Gemini Observatory Image Gallery,
     http://www.gemini.edu/images

[NOTE: Images supporting this release are available at
http://www.gemini.edu/index.php?option=content&task=view&id=138&Itemid=0&limit=1&limitstart=1
]
Received on Wed 20 Jul 2005 04:42:17 PM PDT


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