Discovered in 1955 this nebula was thought to be a supernova remnant until the 1980's. However subsequent observations revealed that a lower than expected radial velocity of the 'debris cloud' and lack of a neutron star could not support the hypothesis for a supernova remnant. This is a large faint planetary nebula about 790 light years distant in the direction of the constellation Gemini. The Medusa Nebula, also known as Abell 21, represents a final stage in the evolution of low mass stars such as the sun, as they transform themselves from red giants to hot white dwarf stars. The Medusa Nebula is estimated to be over 4 light-years across. The Medusa's transforming hot central star is the small blue star on the left at the top of the the crescent shaped figure.
Sunday, December 16, 2007
APOD 2.5
Discovered in 1955 this nebula was thought to be a supernova remnant until the 1980's. However subsequent observations revealed that a lower than expected radial velocity of the 'debris cloud' and lack of a neutron star could not support the hypothesis for a supernova remnant. This is a large faint planetary nebula about 790 light years distant in the direction of the constellation Gemini. The Medusa Nebula, also known as Abell 21, represents a final stage in the evolution of low mass stars such as the sun, as they transform themselves from red giants to hot white dwarf stars. The Medusa Nebula is estimated to be over 4 light-years across. The Medusa's transforming hot central star is the small blue star on the left at the top of the the crescent shaped figure.
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