NGC 1309, a spiral galaxy in Eridanus

 
NGC 1309, a spiral galaxy in Eridanus

Image Credit: NASA, ESA, The Hubble Heritage Team, (STScI/AURA) and A. Riess (STScI)

NGC 1309 is a spiral galaxy of about 75,000 light-years across, located approximately 120 million light-years away in the constellation Eridanus, and is one of over 200 members of the Eridanus Group of galaxies. It is running away from us at 2136 kilometers per second.

Bright blue areas of star formation pepper the moderately wound spiral arms, while dark dust lanes follow the spiral structure into a yellowish central nucleus of older-population stars. The image is complemented by myriad far-off background galaxies.

NGC 1309 was home to a Type Ia supernova, SN 2002fk, whose light reached Earth in September 2002.

A supernova occurs when a star explodes in the final phase of its life when it used up almost all of its main fuel. A Type Ia supernova is a result from the violent explosion of a white dwarf star. This white dwarf was accreting matter from its companion in a binary star system. When the white dwarf collected enough mass and was no longer able to support itself, the star detonated. The exploding star can become billions of times as bright as the Sun before gradually fading from view. At its maximum brightness, it may outshine an entire galaxy for several weeks.

This category of supernovae produces consistent peak luminosity. The stability of this luminosity allows astronomers to use these supernovae as standard candles, to calibrate distance measures in the Universe. By comparing nearby Type Ia supernovae to more distant ones, they can determine not only that the Universe is expanding, but that this expansion is accelerating.

This composite image is taken by the Hubble Space Telescope during August and September 2005.

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