Messier 108 (also known as NGC 3556, nicknamed the Surfboard Galaxy) 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 galaxies ...

about 28 million

light-years 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 101 ...

away from Earth in the northern constellation

Ursa Major Ursa Major (; also known as the Great Bear) is a constellation in the northern sky, whose associated mythology likely dates back into prehistory. Its Latin name means "greater (or larger) bear," referring to and contrasting it with nearby Ursa ...

. It was discovered by

Pierre Méchain Pierre François André Méchain (; 16 August 1744 – 20 September 1804) was a French astronomer and surveyor who, with Charles Messier, was a major contributor to the early study of deep-sky objects and comets. Life Pierre Méchain was bo ...

in 1781 or 1782. From the Earth, this galaxy is seen almost edge-on. This galaxy is an isolated member of the

Ursa Major Cluster The Ursa Major Cluster (Ursa Major I Cluster, UMa I ClG) is a spiral-rich galaxy cluster of the Virgo Supercluster. Some of its largest members are NGC 3631, NGC 3953, M109 on North ( M109 Group) and NGC 3726, NGC 3938, NGC 4051 on South. Th ...

of galaxies in the

local supercluster The Virgo Supercluster (Virgo SC) or the Local Supercluster (LSC or LS) is a mass concentration of galaxies containing the Virgo Cluster and Local Group, which itself contains the Milky Way and Andromeda galaxies, as well as others. At least ...

. It has a morphological classification of type SBbc in the de Vaucouleurs system, which means it is a barred spiral galaxy with somewhat loosely wound arms. The maximum angular size of the galaxy in the optical band is 11

′ The prime symbol , double prime symbol , triple prime symbol , and quadruple prime symbol are used to designate units and for other purposes in mathematics, science, linguistics and music. Although the characters differ little in appearance fr ...

.1 × 4′.6, and it is inclined 75° to the line of sight. This galaxy has an estimated mass of 125 billion

solar mass 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 o ...

es () and bears about 290 ± 80

globular cluster A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of memb ...

s. Examination of the distribution of neutral hydrogen in this galaxy shows discrete shells of expanding gas extending for several kiloparsecs, known as H1 supershells. These may be driven by currents of

dark matter Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not ab ...

, dust and gas contributing to large star formation, having caused supernovae explosions. Alternatively they may result from an infall from the

intergalactic medium Intergalactic may refer to: * "Intergalactic" (song), a song by the Beastie Boys * ''Intergalactic'' (TV series), a 2021 UK science fiction TV series * Intergalactic space * Intergalactic travel, travel between galaxies in science fiction and ...

or arise from radio jets. Observations with the

Chandra X-ray Observatory The Chandra X-ray Observatory (CXO), previously known as the Advanced X-ray Astrophysics Facility (AXAF), is a Flagship-class space telescope launched aboard the during STS-93 by NASA on July 23, 1999. Chandra is sensitive to X-ray sources ...

have identified 83

X-ray X-rays (or rarely, ''X-radiation'') are a form of high-energy electromagnetic radiation. In many languages, it is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it in 1895 and named it ' ...

sources, including a source at the nucleus. The brightest of these is consistent with an intermediate-mass black hole accreting matter. The galaxy is also emitting a diffuse soft X-ray radiation within 2.6

arcminutes A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The nau ...

of the optical galaxy. The spectrum of the source at the core is consistent with an

active galactic nucleus An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much-higher-than-normal luminosity over at least some portion of the electromagnetic spectrum with characteristics indicating that the luminosity is not pro ...

, but an examination with the

Spitzer Space Telescope The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope launched in 2003. Operations ended on 30 January 2020. Spitzer was the third space telescope dedicated to infrared astronomy, f ...

showed no indication of activity. The

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 has an estimated mass of 24 million solar masses (). In January 1969, 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 ...

designated as SN 1969B was discovered in Messier 108. It reached a

brightness Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target. The perception is not linear to luminance, ...

of 13.9 mag. SPIRITS 16tn, another supernova in Messier 108, was discovered by the Spitzer Space Telescope in August 2016. The supernova was only visible in

infrared light Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...

, because it was heavily obscured by

dust Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in ...

. Its

extinction Extinction is the termination of a kind of organism or of a group of kinds ( taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed ...

was estimated to be 8–9 mag, making it one of the most heavily obscured supernovae ever observed. M108map

Notes

References

External links

SEDS: Spiral Galaxy M108
* {{Ngc40 Barred spiral galaxies Ursa Major (constellation) 108 Messier 108 06225 34030 Astronomical objects discovered in 1781 Discoveries by Pierre Méchain Ursa Major Cluster

See also

Notes

References

External links