NGC 4631
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NGC 4631 (also known as the Whale Galaxy or Caldwell 32) is a barred spiral galaxy in the constellation Canes Venatici about 30 million light years away from Earth. It was discovered on 20 March 1787 by German-British astronomer William Herschel.<ref name="selig">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> This galaxy's slightly distorted wedge shape gives it the appearance of a herring or a whale, hence its nickname.<ref name="simbad">Template:Cite simbad</ref> Because this nearby galaxy is seen edge-on from Earth, professional astronomers observe this galaxy to better understand the gas and stars located outside the plane of the galaxy.
Starburst and superwindEdit
NGC 4631 contains a central starburst, which is a region of intense star formation. The strong star formation is evident in the emission from ionized hydrogen<ref name="randetal1992">Template:Cite journal</ref> and interstellar dust heated by the stars formed in the starburst.<ref name="bendoetal2006">Template:Cite journal</ref> The most massive stars that form in star formation regions only burn hydrogen gas through fusion for a short period of time, after which they explode as supernovae. So many supernovae have exploded in the center of NGC 4631 that they are blowing gas out of the plane of the galaxy. This superwind can be seen in X-rays<ref name="wangetal1994">Template:Cite journal</ref> and in spectral line emission.<ref name="randetal1992" /> The gas from this superwind has produced a giant, diffuse corona of hot, X-ray emitting gas around the whole galaxy.<ref name="wangetal1">Template:Cite journal</ref>
Although no supernovae have been observed in NGC 4631 yet, a luminous red nova, designated ATTemplate:Nbsp2021biy, was discovered on 29 January 2021 (type LRN, mag. 18.1).<ref>Transient Name Server entry for AT 2021biy. Retrieved 10 November 2023.</ref>
Nearby galaxies and galaxy groupEdit
NGC 4631 has a nearby companion dwarf elliptical galaxy, NGC 4627. NGC 4627 and NGC 4631 together were listed in the Atlas of Peculiar Galaxies as an example of a "double galaxy" or a galaxy pair.<ref name="arp1966">Template:Cite journal</ref>
NGC 4631 and NGC 4627 are part of the NGC 4631 Group, a group of galaxies that also includes the interacting galaxies NGC 4656 and NGC 4657.<ref name="nbg">Template:Cite book</ref><ref name="fouqueetal1992">Template:Cite journal</ref><ref name="garcia1993">Template:Cite journal</ref><ref name="giuricinetal2002">Template:Cite journal</ref> However, exact group identification is problematic because this galaxy and others lie in a part of the sky that is relatively crowded. Estimates of the number of galaxies in this group range from 5<ref name="nbg" /> to 27,<ref name="giuricinetal2002" /> and all studies identify very different member galaxies for this group.
See alsoEdit
- NGC 891, a similar edge-on spiral galaxy
- NGC 4565, a similar edge-on spiral galaxy
- NGC 5907, a similar edge-on spiral galaxy
- List of NGC objects (4001–5000)
ReferencesEdit
External linksEdit
- APOD (2004-01-23) – The Whale Galaxy
- APOD (2010-05-17) – The Whale Galaxy (a better image)
- Template:WikiSky
- Template:CelestialRefEx
- SEDS – NGC 4631
Template:Sky Template:Catalogs Template:Caldwell catalogue Template:Ngc50 Template:Canes Venatici Template:Authority control