Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

December 4, 1995

GL 229B: An Elusive Brown Dwarf?
Credit: 60-inch Telescope, Palomar Observatory, T. Nakajima (Caltech), S. Durrance (JHU)

Explanation: What type of matter makes up most of the universe? This question is arguably the most perplexing astronomical mystery of our time. A leading candidate is a type of dim, low mass star called a "brown dwarf" star. Our universe could contain more brown dwarfs than any other type of star - but they are so dim they have so far escaped detection. The dramatic photograph above, taken in October 1994, sheds new light on this "dark matter" problem. The seemingly inconspicuous companion to the right of the overexposed image of a normal star is thought to be an elusive brown dwarf. Now that the existence of brown dwarfs has been demonstrated, a key remaining question is their abundance.

Tomorrow's picture: The Swirling Centre of NGC 4261

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
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&: Michigan Tech. U.