Printer Friendly

Radio telescope images second dust disk.

For nearly a decade, Beta Pictoris has reigned as the only mature, main-sequence star with an encircling disk of dust - perhaps much like the disk from which our solar system evolved 4.6 billion years ago - that astronomers have clearly imaged. Now, astronomers have used a French radio telescope to map the dust encircling nearby Fomalhaut, the second star proved conclusively to have such a disk.

Fomalhaut, Beta Pictoris, and our own sun are main-sequence stars because they fuse hydrogen into helium to generate energy. The presence of dust around such middle-aged stars may signify that the process of solar-system formation has proceeded at least to the point where comets and asteroids have come into existence, explains planetary astronomer Alan Stern of the Southwest Research Institute in San Antonio, Texas.

Stern and colleagues David A. Weintraub and Michel C. Festou announced their observations of Fomalhaut in a March 30 circular of the International Astronomical Union. The disk appears to extend at least 500 astronomical units (AU) across - 500 times the average distance between the Earth and the sun - although Stern expects this number to grow with more extensive observations. In comparison, the Beta Pictoris disk reaches 2,300 AU across and is significantly more massive. Fomalhaut, however, lies 21 light-years closer to Earth than Beta Pictoris does, which may prove advantageous in upcoming efforts to map the star's disk in more detail, says Stern.

The new observation also marks the first time astronomers have imaged a disk around a mature, main-sequence star using the radio energy given off by dust particles. The dust in Fomalhaut's disk soaks up energy from the star and then emits a wan thermal signal at a wavelength of 1.3 millimeters, whereas the star itself is almost undetectable in this region of the spectrum. Consequently, the radio trace of the dust stands out comparatively brightly.

In contrast, astronomers had to use special instruments to mask Beta Pictoris' face in order to detect the scant amount of visible light scattered off dust particles in that star's disk (SN:6/20/92, p.413). "You've got a more effective tool [for mapping dust disks] if you can see the stuff in its own thermal emissions," comments Weintraub, an astronomer at Vanderbilt University in Nashville.

Astronomer Dana E. Backman of Franklin and Marshall College in Lancaster, Pa., explains that the new radio survey of Fomalhaut has confirmed in a concrete manner observations made a decade ago with the Infrared Astronomical Satellite (IRAS). Then, astronomers discovered tantalizing evidence that dusty rings may encircle a number of nearby stars, but IRAS proved inadequate for mapping them in detail.

"You now have substantially better information about the second well-studied example of what I think is a ubiquitous phenomenon," says Backman, whose studies of nearby stars have convinced him that many, if not most, main-sequence stars have disks. "This study of Fomalhaut is just one more step [toward] showing that."
COPYRIGHT 1993 Science Service, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1993, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:French radio telescope maps dust surrounding Fomalhaut star
Author:Pendick, Daniel
Publication:Science News
Article Type:Brief Article
Date:Apr 10, 1993
Previous Article:Neandertals take a big step back in time.
Next Article:Inspecting teleported quantum information.

Related Articles
A massive star lights its surroundings.
Watching a young star eat.
Bullies of the universe: massive stars rob their smaller neighbors.
Big gun: Pistol shines in the infrared.
Dust disks hint at baby solar system.
Dust glow hints at wave of early star birth.
Dusty disks may reveal hidden worlds; on the trail of extrasolar planets.
Spying a planet in star's dusty veil.
Disks of dust: planet-stuff surrounds other sunlike stars.
Recipe for a heavyweight: making a massive star.

Terms of use | Copyright © 2017 Farlex, Inc. | Feedback | For webmasters