NGC 2997 is a face-on

unbarred spiral galaxy An unbarred spiral galaxyAstronomy Pictures(accessed 18 April 2010) is a type of spiral galaxy without a central bar, or one that is not a barred spiral galaxy. It is designated with an SA in the galaxy morphological classification scheme. Ba ...

about 40 million

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s away in the faint southern

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Antlia Antlia (; from Ancient Greek ''ἀντλία'') is a constellation in the Southern Celestial Hemisphere. Its name means " pump" in Latin and Greek; it represents an air pump. Originally Antlia Pneumatica, the constellation was established by N ...

. It was discovered March 4, 1793 by German-born astronomer William Herschel.

J. L. E. Dreyer John Louis Emil Dreyer (13 February 1852 – 14 September 1926) was a Danish astronomer who spent most of his career working in Ireland. He spent the last decade of his life in Oxford, England. Life Dreyer was born in Copenhagen. His fathe ...

described it as, "a remarkable object, very faint, very large, very gradually then very suddenly bright middle and 4 arcsec nucleus. This is the brightest galaxy of the NGC 2997 group of galaxies, and was featured on the cover of the first edition of ''Galactic Dynamics'' by

James Binney James Jeffrey Binney, FRS, FInstP (born 12 April 1950) is a British astrophysicist. He is a professor of physics at the University of Oxford and former head of the Sub-Department of Theoretical Physics as well as an Emeritus Fellow of Merto ...

and

Scott Tremaine Scott Duncan Tremaine (born 1950) is a Canadian-born astrophysicist. He is a fellow of the Royal Society of London, the Royal Society of Canada and the National Academy of Sciences. Tremaine is widely regarded as one of the world's leading as ...

. This is a

grand-design galaxy A grand design spiral galaxy is a type of spiral galaxy with prominent and well-defined spiral arms, as opposed to multi-arm and flocculent spirals which have subtler structural features. The spiral arms of a grand design galaxy extend clearly ar ...

with a symmetrical, two-armed form. The morphological classification of NGC 2997 is SAB(rs)c, indicating a weakly- barred spiral galaxy (SAB) with an incomplete ring around the bar (rs) and loosely-wound spiral arms (c). It is inclined at an angle of 40° to the line of sight from the Earth, with the

major axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the lo ...

aligned along a position angle of 110°. The arms host a series of dusty knots that are

star-forming region Star formation is the process by which dense regions within molecular clouds in The "medium" is present further soon.-->interstellar space

s being generated through gas compression from density waves. At the core, the arms converge to form a circumnuclear ring with symmetrically-placed hot spots containing

super star clusters A super star cluster (SSC) is a very massive young open cluster that is thought to be the precursor of a globular cluster. These clusters called "super" because they are relatively more luminous and contain more mass than other young star clusters. ...

. A pair of

supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...

events have been detected in the proximity of this galaxy. CCD images taken October 24, 2003 revealed supernova SN 2003jg, positioned east and north of the galactic nucleus. This was determined to be a Type Ib/c supernova. Supernova SN 2008eh was reported on July 21, 2008, reaching magnitude 15.0. It was positioned east and north of the galactic core.

References

External links

* *
NGC 2997 in Antlia
* {{DEFAULTSORT:NGC 2997 Unbarred spiral galaxies Antlia 2997 027978 434- G 35

See also

References

External links