NGC 613 is a

barred spiral galaxy A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars. Bars are found in about two thirds of all spiral galaxies, and generally affect both the motions of stars and interstellar gas within spiral galaxi ...

located 67 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 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 ...

. This galaxy was discovered in 1798 by German-English astronomer

William Herschel Frederick William Herschel (; german: Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline H ...

, then re-discovered and catalogued 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 ...

. It was first photographed in 1912, which revealed the spiral form of the nebula. During the twentieth century,

radio telescope A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency ...

observations showed that a linear feature in the nucleus was a relatively strong source of radio emission. NGC 613 is inclined by an angle of 37° to the

line of sight The line of sight, also known as visual axis or sightline (also sight line), is an imaginary line between a viewer/observer/spectator's eye(s) and a subject of interest, or their relative direction. The subject may be any definable object taken ...

from the

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

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 125°. The morphological classification of NGC 613 is SBbc(rs), indicating that it is a spiral galaxy with a bar across the nucleus (SB), a weak inner ring structure circling the bar (rs), and moderate to loosely wound spiral arms (bc). The bar is relatively broad but irregular in profile with a position angle that varies from 115–124° and dust lanes located along the leading edges. Star formation is occurring at the ends of the bar and extending along the well-defined spiral arms. The central bulge is readily apparent, with a radius of 14″. The classification of the nucleus is of type HII, indicating a match to the spectrum of an

H II region An H II region or HII region is a region of interstellar atomic hydrogen that is ionized. It is typically in a molecular cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundreds ...

. Near the core, the stars have a

velocity dispersion In astronomy, the velocity dispersion (''σ'') is the statistical dispersion of velocity, velocities about the Arithmetic mean, mean velocity for a group of astronomical objects, such as an open cluster, globular cluster, galaxy, galaxy cluster, or ...

of 136 ± 20 km/s. The nucleus is a source of radio emission with the form of an inner ring with a radius of about and a linear feature that is perhaps perpendicular to it. The latter consists of three discrete blobs spanning approximately . Observations suggest the presence of a

supermassive black hole A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions of times the mass of the Sun (). Black holes are a class of astronomical obj ...

at the core with a mass in the range times the

mass of the Sun The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

. On September 20, 2016, Argentinian amateur astronomer Victor Buso captured supernova SN 2016gkg in NGC 613, just as it was starting to erupt. This was a type IIb

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 ...

, a supernova that initially shows a hydrogen envelope like a

type II 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 this ...

, but later loses the hydrogen lines in its spectrum to appear like a

type Ib supernova Type Ib and Type Ic supernovae are categories of supernovae that are caused by the stellar core collapse of massive stars. These stars have shed or been stripped of their outer envelope of hydrogen, and, when compared to the spectrum ...

. It showed the double peak that is common to many type IIb supernovae, rising to around

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

15.5 shortly after discovery and then again about 20 days later. The progenitor star has been identified in

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...

images from before its collapse, and it is likely to have been a

yellow supergiant A yellow supergiant (YSG) is a star, generally of spectral type F or G, having a supergiant luminosity class (e.g. Ia or Ib). They are stars that have evolved away from the main sequence, expanding and becoming more luminous. Yellow supergiants ...

References

Gallery

Sculpted_in_Sculptor.jpg, First discovered in 1798 by German-English astronomer William Hershel, NGC 613 is a galaxy which lies in the southern constellation of Sculptor 67 million light-years away. .

External links

Supernova SN 2016gkg in NGC 613
from The Virtual Telescope Project {{DEFAULTSORT:NGC 613 Sculptor (constellation) Barred spiral galaxies 0613 005849