jun 302014


June 30, 2014

NGC 2775, a spiral galaxy in Cancer

Caldwell 48

Image Credit & Copyright: Robert Gendler

NGC 2775 (also known as Caldwell 48) is a spiral galaxy of about 75 thousand light-years across, located some 55,5 million light-years away from the Earth in the constellation of Cancer (the Crab), while it is receding from us at approximately 1,350 kilometers per second.

Discovered by the German-British astronomer William Herschel in 1783, it is the most prominent member in the NGC 2775 Group, a small galaxy group which is part of the Virgo Supercluster, along with our own Local Group.

This galaxy has large, perfectly smooth central bulge. The spiral pattern starts very abruptly outside of this region in an extremely complex multi-armed spiral structure laced with obscuring dark dust lanes. Several HII regions can be detected on the tightly wound spiral arms, implying recent star formation.

SN1993z is the only supernova known to have occurred in NGC 2775 and was a Type Ia with a peak magnitude of 13.9.

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 image is based on observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA) and the Canadian Astronomy Data Centre (CADC/NRC/CSA). Processing by Robert Gendler.

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