Anne’s Picture of the Day: Spiral Galaxy NGC 1288

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Januari 1, 2013

NGC 1288, a huge spiral galaxy in Fornax

Image Credit: ESO

NGC 1288 is a huge barred spiral galaxy of about 200,000 light-years across, located some 300 million light-years away in the southern constellation of Fornax, while it is speeding away from us at approximately 4538 kilometers per second. It’s appearance is thought to be quite similar to our Milky Way galaxy.

This spiral galaxy, seen almost face-on, shows multiple spiral arms, and as the arms move outward, they repeatedly fork. The arms are made up of dense clusters of stars and gas. A small bar of stars and gas runs across the center of the galaxy.

NGC 1288 is most probably surrounded by a large dark matter halo. The appearance and number of spiral arms are directly related to the amount of dark matter in the galaxy’s halo.

A Type Ia supernova called SN 2006dr, visible just left of the center of NGC 1288, was first spotted on the night of 17 July 2006 by amateur astronomer Berto Monard. ESO’s Very Large Telescope took images of the supernova, that expelled material with speeds up to 10,000 kilometers per second, when it was at its peak brightness, shining as bright as the entire galaxy itself.

A Type Ia supernova is a result from the violent explosion of a white dwarf star (a compact star that has ceased fusion in its core). The white dwarf increases its mass beyond a critical limit (the Chandrasekhar limit) by gobbling up matter from a companion star. A runaway nuclear explosion then makes the star suddenly as bright as a whole galaxy, before gradually fading from view.

This category of supernovae produces consistent peak luminosity. The stability of this luminosity allows these supernovae to be used as standard candles to measure the distance to their host galaxies, because the visual magnitude of the supernovae depends primarily on the distance.

This colour-composite image of NGC 1288, with supernova SN 2006dr was taken with ESO’s Very Large Telescope through several filters. The data were acquired by ESO’s Paranal Science team. The final image was made by Henri Boffin (ESO). Many distant galaxies are also seen in this image.

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