dipper@utastro.UUCP (Debbie Byrd) (03/09/85)
We haven't yet discovered another solar system. More -- after this. March 9 Planets for Distant Stars Recently you may have heard that "solar systems" or "planets" have been found orbiting nearby stars. But so far the only undisputed planets are those belonging to the sun in our own solar system -- Mercury, Venus, Earth, Mars and so on. Still, the word "planet" has been used -- for example, in connection with a companion of the star Van Biesbroeck 8, located 21 light-years away. It was announced that VB-8 has a "planet" -- an object not massive enough to have its own internal nuclear fusion reactions -- the internal power source that enables stars like our sun to shine. But most astronomers disagree that the companion to VB-8 should be called a planet -- because stars can have another source of power -- energy liberated by shrinking in their own gravitational fields. Such low-mass stars radiate blast-furnace-like heat and light from their surfaces. They're known as brown dwarfs. The newly-seen object -- called VB-8B -- is a true "brown dwarf" star, not a planet. Planets are fundamentally "cold" objects. Their brightness comes from reflected starlight. VB-8B shines by virtue of its glowing hot surface. It's an interesting object -- only about half as massive as the next-smallest star so far known -- but still dozens of times more massive than the largest planet known, Jupiter. Nature probably doesn't distinguish sharply between stars and planets, though WE have separate words for them. The galaxy may contain objects that range in size from great stars to grains of dust. VB-8B is a brown dwarf star -- holding its feeble candle out among the greater and brighter stars that dominate our sky. Script by Deborah Byrd and Harlan Smith. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin
petersen@ucbvax.ARPA (David A. Petersen) (04/03/85)
I hear a lot about how great the space telescope is going to be. I want to know if it is going to be able to see planets of other stars. If so, how big and how far away? Mostly I am interested in stars within 20-30 light-years of sol. What kind of detail would be resolvable? Can spectroscopy be done to determine the atmosphere and composition?