NGC 7793 is a

flocculent spiral galaxy A flocculent spiral galaxy is a type of spiral galaxy. Unlike the well-defined spiral architecture of a grand design spiral galaxy, flocculent (meaning "flaky") galaxies are patchy, with discontinuous spiral arms. Self-propagating star formation ...

in the 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 ...

Sculptor Sculpture is the branch of the visual arts that operates in three dimensions. Sculpture is the three-dimensional art work which is physically presented in the dimensions of height, width and depth. It is one of the plastic arts. Durable sc ...

. It was discovered in 1826 by Scottish astronomer

James Dunlop James Dunlop FRSE (31 October 1793 – 22 September 1848) was a Scottish astronomer, noted for his work in Australia. He was employed by Sir Thomas Brisbane to work as astronomer's assistant at his private observatory, once located at Paramat ...

. The galaxy is located at a distance of 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 and is receding with a heliocentric

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...

of . NGC 7793 is one of the five brightest galaxies within the

Sculptor Group The Sculptor Group is a loose group of galaxies visible near the south galactic pole. The group is one of the closest groups of galaxies to the Local Group; the distance to the center of the group from the Milky Way is approximately . The Sculp ...

. The morphological class of NGC 7793 is SA(s)d, indicating it is

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 ...

(SA) with no inner ring structure (s) and the

arms Arms or ARMS may refer to: *Arm or arms, the upper limbs of the body Arm, Arms, or ARMS may also refer to: People * Ida A. T. Arms (1856–1931), American missionary-educator, temperance leader Coat of arms or weapons *Armaments or weapons **Fi ...

are loosely wound and disorganized (d). It is flocculent in appearance with a very small bulge and a star cluster at the nucleus. The

galactic disk A galactic disc (or galactic disk) is a component of disc galaxies, such as spiral galaxies and lenticular galaxies. Galactic discs consist of a stellar component (composed of most of the galaxy's stars) and a gaseous component (mostly composed ...

is inclined at an angle of 53.7° to the line of sight from the Earth. The visible profile is elliptical in form with an

angular size The angular diameter, angular size, apparent diameter, or apparent size is an angular distance describing how large a sphere or circle appears from a given point of view. In the vision sciences, it is called the visual angle, and in optics, it is ...

of and a major axis aligned along a

position angle In astronomy, position angle (usually abbreviated PA) is the convention for measuring angles on the sky. The International Astronomical Union defines it as the angle measured relative to the north celestial pole (NCP), turning positive into the d ...

of 99.3°. There are two nearby

dwarf galaxy A dwarf galaxy is a small galaxy composed of about 1000 up to several billion stars, as compared to the Milky Way's 200–400 billion stars. The Large Magellanic Cloud, which closely orbits the Milky Way and contains over 30 billion stars, is ...

companions. On March 25, 2008, a

type II-P supernova A Type II supernova (plural: ''supernovae'' or ''supernovas'') results from the rapid collapse and violent explosion of a massive star. A star must have at least 8 times, but no more than 40 to 50 times, the mass of the Sun () to undergo th ...

designated SN 2008bk was discovered in NGC 7793. At

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

12.5, it became the 2nd brightest supernova of 2008. The progenitor of this supernova was a

red supergiant Red supergiants (RSGs) are stars with a supergiant luminosity class ( Yerkes class I) of spectral type K or M. They are the largest stars in the universe in terms of volume, although they are not the most massive or luminous. Betelgeuse and Anta ...

, observed only 547 days prior to the explosion. Jets from a black hole named ''P13'' power a large nebula designated ''S26'' in the outer spiral of this galaxy. Recently, the mass of P13 was determined to be less than 15 solar masses, and its companion star is estimated to be around 20 solar masses. The two orbit each other in 64 days. Based on this estimate, P13 is stripping material away from a nearby star about ten times faster than was previously believed to be physically possible. If correct, this observation would show flaws in theories that a black hole's mass and rate of consumption are a fixed relationship.

Gallery

Phot-14b-09-fullres 2.JPG, Visual and infrared image of NGC 7793

References

External links

SST: NGC 7793
__NOTOC__ {{DEFAULTSORT:NGC 7793 Unbarred spiral galaxies Sculptor Group Sculptor (constellation) 7793 73049 Astronomical objects discovered in 1826

Gallery

See also

References

External links