IC 1613 (object 1613 in the Index Catalogues (IC), also known as Caldwell 51) is an irregular

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 so ...

, visible in the

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

Cetus Cetus () is a constellation, sometimes called 'the whale' in English. The Cetus was a sea monster in Greek mythology which both Perseus and Heracles needed to slay. Cetus is in the region of the sky that contains other water-related constellat ...

near the star

26 Ceti 6 (six) is the natural number following 5 and preceding 7. It is a composite number and the smallest perfect number. In mathematics Six is the smallest positive integer which is neither a square number nor a prime number; it is the second smal ...

. It was discovered in 1906 by

Max Wolf Maximilian Franz Joseph Cornelius Wolf (21 June 1863 – 3 October 1932) was a German astronomer and a pioneer in the field of astrophotography. He was the chairman of astronomy at the University of Heidelberg and director of the Heidelberg-K ...

, and is approaching

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 sur ...

at 234 km/s. IC 1613 is a member of the Local Group. It has played an important role in the calibration of the

Cepheid variable A Cepheid variable () is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude. A strong direct relationship between a Cepheid vari ...

period-luminosity relation In astronomy, a period-luminosity relation is a relationship linking the luminosity of pulsating variable stars with their pulsation period. The best-known relation is the direct proportionality law holding for Classical Cepheid variables, sometim ...

for estimating distances. Other than the

Magellanic Clouds The Magellanic Clouds (''Magellanic system'' or ''Nubeculae Magellani'') are two irregular dwarf galaxies in the southern celestial hemisphere. Orbiting the Milky Way galaxy, these satellite galaxies are members of the Local Group. Because bo ...

, it is one of the few Local Group dwarf irregular galaxy where

RR Lyrae-type variable RR Lyrae variables are periodic variable stars, commonly found in globular clusters. They are used as standard candles to measure (extra) galactic distances, assisting with the cosmic distance ladder. This class is named after the prototype and ...

s have been observed; this factor, along with an unusually low abundance of

interstellar dust Cosmic dust, also called extraterrestrial dust, star dust or space dust, is dust which exists in outer space, or has fallen on Earth. Most cosmic dust particles measure between a few molecules and 0.1 mm (100 micrometers). Larger particles are c ...

both within IC 1613 and along the line of sight enable especially accurate distance estimates. In 1999, Cole et al. used the

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 vers ...

to find that the dominant

population Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction usi ...

of this galaxy has an age of ~7 Gyr. Using its

Hess diagram A Hess diagram plots the relative density of occurrence of stars at differing color–magnitude positions of the Hertzsprung–Russell diagram for a given galaxy or resolved stellar population. The diagram is named after R. Hess who originated ...

, they found that its evolutionary history may be similar to that of the

Pegasus Dwarf Irregular Galaxy The Pegasus Dwarf Irregular Galaxy (also known as Peg DIG or the Pegasus Dwarf) is a dwarf irregular galaxy in the direction of the constellation Pegasus. It was discovered by A. G. Wilson in the 1950s. The Pegasus Dwarf is a companion of the A ...

. Both galaxies are classified as Ir V in the DDO system. Also in 1999, Antonello et al. found five cepheids of

Population II During 1944, Walter Baade categorized groups of stars within the Milky Way into stellar populations. In the abstract of the article by Baade, he recognizes that Jan Oort originally conceived this type of classification in 1926: Baade noticed ...

in IC 1613, giving self-evident support for the existence of a very old stellar population component of IC 1613. In 1999, King, Modjaz, & Li discovered the first

nova A nova (plural novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star (hence the name "nova", which is Latin for "new") that slowly fades over weeks or months. Causes of the dramat ...

ever detected in IC 1613. Caldwell 51 (50290991758)

IC 1613 contains a WO star known as DR1, which might be the only Wolf–Rayet star in the galaxy, although a candidate WC+O binary, SPIRITS14bqe, has been found. The galaxy also contains a Luminous Blue Variable candidate, and a rich population of OB-type stars and OB associations. There are many faint galaxies close to IC 1613, catalogued as members of the group NOGG H 57.

References

External links

* * {{DEFAULTSORT:IC 1613 Dwarf irregular galaxies Local Group Cetus (constellation)

1613 Events January–June * January 11 – Workers in a sandpit in the Dauphiné region of France discover the skeleton of what is alleged to be a 30-foot tall man (the remains, it is supposed, of the giant Teutobochus, a legendar ...

00668 03844 051b Astronomical objects discovered in 1906 Astronomical events in the near future