NGC 7013 is a relatively nearby

spiral In mathematics, a spiral is a curve which emanates from a point, moving farther away as it revolves around the point. Helices Two major definitions of "spiral" in the American Heritage Dictionary are:lenticular galaxy A lenticular galaxy (denoted S0) is a type of galaxy intermediate between an elliptical (denoted E) and a spiral galaxy in galaxy morphological classification schemes. It contains a large-scale disc but does not have large-scale spiral arms. L ...

estimated to be around 37 to 41.4 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 from Earth in the

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 ...

of Cygnus. NGC 7013 was discovered by 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 ...

on July 17, 1784 and was also observed by his son, astronomer

John Herschel Sir John Frederick William Herschel, 1st Baronet (; 7 March 1792 – 11 May 1871) was an English polymath active as a mathematician, astronomer, chemist, inventor, experimental photographer who invented the blueprint and did botanical wor ...

on September 15, 1828.

Physical characteristics

NGC 7013 is tilted 90° to the Earth's line of sight, allowing its structure to be seen. However, NGC 7013 is classified as either as a

spiral galaxy Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work ''The Realm of the Nebulae''lenticular galaxy A lenticular galaxy (denoted S0) is a type of galaxy intermediate between an elliptical (denoted E) and a spiral galaxy in galaxy morphological classification schemes. It contains a large-scale disc but does not have large-scale spiral arms. L ...

. NGC 7013 is also considered part of a class of galactic nuclei that is defined by their spectral line emissions, called

low-ionization nuclear emission-line region A low-ionization nuclear emission-line region (LINER) is a type of galactic nucleus that is defined by its spectral line emission. The spectra typically include line emission from weakly ionized or neutral atoms, such as O, O+, N+, and S+. ...

galaxies or LINERs. The galaxy appears to have two rings in its structure. The inner ring appears to completely disconnect from the central bulge while the stars in the outer ring appear to have very little spiral pattern. Optical images of NGC 7013 show that it has a small bulge with a bright inner ring and a faint disk both crossed by dust lanes. A longer exposure of the galaxy made by the Palomar Observatory-National Geographic Sky Survey shows an extended disk around the bulge and the inner ring. The disk shows little structure except for a faint, thin spiral-like feature running through the galaxy.

HI distribution

The neutral atomic hydrogen distribution in NGC 7013 is mostly located in the two rings. In between the two rings there is a very low concentration of interstellar medium. The low level of neutral atomic hydrogen in the disk of NGC 7013 and the reddish color of the galaxy suggests that the gas content of the galactic disc has fallen below the threshold at which star formation is likely to take place. The small bulge-to-disk ratio and the slow rotation velocity show that NGC 7013 is a low-mass, low-density galaxy unlike the more luminous, typical

lenticular galaxies A lenticular galaxy (denoted S0) is a type of galaxy intermediate between an elliptical (denoted E) and a spiral galaxy in galaxy morphological classification schemes. It contains a large-scale disc but does not have large-scale spiral arms. L ...

. The galaxy may thus be a former late-type spiral galaxy which have exhausted most of its interstellar gas, either by star formation or by internal sweeping.

Gallery

File:NGC 7013 2MASS.jpg,

2MASS The Two Micron All-Sky Survey, or 2MASS, was an astronomical survey of the whole sky in infrared light. It took place between 1997 and 2001, in two different locations: at the U.S. Fred Lawrence Whipple Observatory on Mount Hopkins, Arizona, and ...

image of NGC 7013

References

External links

Simbad

{{Cygnus (constellation) Unbarred spiral galaxies LINER galaxies Cygnus (constellation) 7013 11670 66003 Lenticular galaxies Astronomical objects discovered in 1784

Physical characteristics

HI distribution

Gallery

See also

References

External links