Binary System

Excerpts from an article posted on the usenets:
UF Astronomers Part of Team to Spot Possible Two-Star Solar System
April 20, 1998, Writer: Steve Orlando, sfo@ufl.edu

In a discovery they say could shed new light on the genesis of our solar system, astronomers with the University of Florida and Harvard University have found a star surrounded by a disk of dust that may be forming planets. "It's very exciting. We don't see planets directly in this system, but there is indirect evidence of a planet," said Charles Telesco, the astronomy professor leading the four-member UF team. He said a wake-like void that appears in the disk is typical of what would be left by a moving celestial body. ...

Known as HR 4796A, the star is about 220 light years from Earth and about 47 billion miles from its companion star, HR 4796B. It is in the constellation Centaurus, visible primarily from the Southern hemisphere. Astronomers estimate HR 4796A could represent what Earth's solar system looked like in its infancy, Telesco said. The sun is about 5 billion years old, and the earth is about 4.5 billion years old. The HR 4976 pair, by comparison, is estimated to be about 10 million years old, which Telesco said puts the dust disk precisely in the proper planet-building time frame. "What we may be looking at is a solar system like our solar system but at a much earlier stage," Telesco said.

If the entire dust disk has formed planets or is forming them, the solar system would be considerably larger than our own. Measuring from Pluto, the planet farthest from the sun, our system is about 80 astronomical units across. The HR 4976 disk is more than three times that size - some 250 astronomical units. An astronomical unit is the distance from the earth to the sun - about 93 million miles. However, Telesco said, planets may be forming only near the inside edge of the disk, an area roughly the size of our solar system. ...