Montage of our solar system

Two astronomers have photographed evidence indicating possible solar system around Beta Pictoris, star 50 light years from Earth.

Employing special optical and computer techniques, Dr. Bradford A. Smith of the University of Arizona and Dr. Richard J. Terrile of NASA's Jet Propulsion Laboratory (JPL) photographed vast swarm of solid particles, called circumstellar disk, surrounding the nearby star. The disk is the first of its kind to be seen clearly in astronomical photographs.

There is some evidence to suggest that planets could have formed around the star. The brightness of the star seen through its disk indicates that the innermost particles of the disk may have been swept away.

The formation of planets would produce such an effect. But the astronomers say they have not been able to determine if there are actually planets around the star.

The circumstellar disk is believed to be made up of countless particles ranging in size from tiny grains less than thousandth of an inch (l0 microns) in diameter to the nuclei of comets few miles across. The most likely composition includes ices, silicates and carbonaceous (organic) compounds, the same materials from which the earth and the other planets of the solar system are believed to have formed.

Questions to be answered are whether Beta Pictoris has existed long enough for planets to have formed and whether large planetary bodies will necessarily form, even when the required materials are present.

Appearing nearly edge-on as seen from the earth, the flattened disk extends outward to more than 40 billion miles (60 billion kilometers). This is more than 400 times the distance of the Earth from the Sun.

The disk extends well beyond the regions close to the star where planets tend to occur. For this reason, much of the material seen in the pictures is, at present, too distant from Beta Pictoris to be directly involved in planet formation. But, it may include some material that was left over from the formation process and then ejected by planetary gravitational forces into space around the star.

Because the disk is so flat, it is believed to be very young, perhaps no more than few hundred million years old. (Our Solar System is 4.5 billion years old.) An older disk, disturbed by planets that might be orbiting Beta Pictoris, would not be as flat and much of the leftover debris would be ejected into interstellar space.

To the unaided eye, Beta Pictoris, which is twice as massive as the Sun and at least l0 times as luminous, appears as faint (fourth magnitude) star in Pictor, an obscure constellation in the southern skies. To those living throughout much of the Earth's northern Hemisphere, Beta Pictoris remains permanently below the horizon; for Americans, it can only be seen clearly from the extreme southern parts of the country.

Smith and Terrile's attention was drawn to Beta Pictoris by reports earlier this year by the IRAS (Infrared Astronomical Satellite) science team which stated that this star, and three others similar to it, showed abnormal amounts of infrared radiation, implying the existence of solid material orbiting around the stars.

To make the observation, the astronomers used l00-inch (2.5 meter) telescope at the Las Campanas Observatory near La Serena, Chile, operated by the Carnegie Institution of Washington, D.C. CCD (Charge-Coupled Device) electronic camera and coronagraph were attached to the telescope. The coronagraph is an optical device developed for detecting very faint objects close to brighter ones. The images were computer-processed at the University of Arizona and JPL.

Computer processing revealed what could not be seen in the unprocessed image -- two faint streaks of light extending radially outward to great distances from the star.

The work was jointly funded by the University of Arizona and NASA's Office of Space Sciences and Applications.

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