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Messier 81

 
Messier 81

 
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Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a spiral galaxy
Spiral galaxy

A spiral galaxy is a galaxy belonging to one of the three main galaxy morphological classification originally described by Edwin Hubble in his 1936 work ?The Realm of the Nebulae? and, as such, forms part of the Hubble sequence....
 about 12 million
1 E22 m

To help compare different orders of magnitude, this page lists distances starting at 10 zettametre .1 E+21 m* 24 Zm ? 2.5 million light years ? Distance to the Andromeda Galaxy...
 light-year
Light-year

A light-year or light year is a Units of measurement of length, equal to just under ten orders_of_magnitude_%28numbers%29#1012 kilometres....
s away in the constellation
Constellation

A constellation is a group of stars that appear to have a physical proximity in the sky. The stars in a constellation are often vastly distant from each other, but they appear close to each other from the perspective of Earth....
 Ursa Major
Ursa Major

Ursa Major is a constellation visible throughout the year in most of the northern hemisphere. Its name means the Great Bear in Latin. It is dominated by the widely recognized asterism known as the Big Dipper or Plough, which is a useful pointer toward north, and which has mythological significance in numerous world cultures....
. M81 is one of the most striking examples of a grand design spiral galaxy
Grand design spiral galaxy

A grand design spiral galaxy is a type of spiral galaxy with prominent and well-defined spiral arms, as opposed to multi-arm and flocculent spirals which have subtler structural features....
, with near perfect arms spiraling into the very center. Because of its proximity to Earth
Earth

Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Wiktionary:Terra.Note that by International Astronomical Union convention, the term "Terra" is used for naming extensive land masses, rather...
, its large size, and its active galactic nucleus
Active galactic nucleus

An active galactic nucleus is a compact region at the centre of a galaxy which has a much higher than normal luminosity over some or all of the electromagnetic spectrum ....
 (which harbors a supermassive black hole
Supermassive black hole

A supermassive black hole is a black hole with a mass of an order of magnitude between 105 and 1010 solar masses. Most, if not all, galaxy, including the Milky Way, are believed to contain supermassive black holes at their centers....
) Messier 81 is a popular galaxy to study in professional astronomy
Astronomy

Astronomy is the science of Astronomical object and Phenomenon that originate outside the Earth's atmosphere . It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the physical cosmology....
 research. The galaxy's large size and relatively low apparent magnitude (lower magnitude implies higher brightness) also make it a popular target for amateur astronomy
Amateur astronomy

Amateur astronomy, a subset of astronomy, is a hobby whose participants enjoy studying and observing celestial objects....
 observations.

Discovery
Messier 81 was first discovered by Johann Elert Bode
Johann Elert Bode

Johann Elert Bode was a Germany astronomer known for his reformulation and popularization of the Titius-Bode law. Bode determined the orbit of Uranus and suggested the planet's name....
 in 1774.






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Encyclopedia


Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a spiral galaxy
Spiral galaxy

A spiral galaxy is a galaxy belonging to one of the three main galaxy morphological classification originally described by Edwin Hubble in his 1936 work ?The Realm of the Nebulae? and, as such, forms part of the Hubble sequence....
 about 12 million
1 E22 m

To help compare different orders of magnitude, this page lists distances starting at 10 zettametre .1 E+21 m* 24 Zm ? 2.5 million light years ? Distance to the Andromeda Galaxy...
 light-year
Light-year

A light-year or light year is a Units of measurement of length, equal to just under ten orders_of_magnitude_%28numbers%29#1012 kilometres....
s away in the constellation
Constellation

A constellation is a group of stars that appear to have a physical proximity in the sky. The stars in a constellation are often vastly distant from each other, but they appear close to each other from the perspective of Earth....
 Ursa Major
Ursa Major

Ursa Major is a constellation visible throughout the year in most of the northern hemisphere. Its name means the Great Bear in Latin. It is dominated by the widely recognized asterism known as the Big Dipper or Plough, which is a useful pointer toward north, and which has mythological significance in numerous world cultures....
. M81 is one of the most striking examples of a grand design spiral galaxy
Grand design spiral galaxy

A grand design spiral galaxy is a type of spiral galaxy with prominent and well-defined spiral arms, as opposed to multi-arm and flocculent spirals which have subtler structural features....
, with near perfect arms spiraling into the very center. Because of its proximity to Earth
Earth

Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Wiktionary:Terra.Note that by International Astronomical Union convention, the term "Terra" is used for naming extensive land masses, rather...
, its large size, and its active galactic nucleus
Active galactic nucleus

An active galactic nucleus is a compact region at the centre of a galaxy which has a much higher than normal luminosity over some or all of the electromagnetic spectrum ....
 (which harbors a supermassive black hole
Supermassive black hole

A supermassive black hole is a black hole with a mass of an order of magnitude between 105 and 1010 solar masses. Most, if not all, galaxy, including the Milky Way, are believed to contain supermassive black holes at their centers....
) Messier 81 is a popular galaxy to study in professional astronomy
Astronomy

Astronomy is the science of Astronomical object and Phenomenon that originate outside the Earth's atmosphere . It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the physical cosmology....
 research. The galaxy's large size and relatively low apparent magnitude (lower magnitude implies higher brightness) also make it a popular target for amateur astronomy
Amateur astronomy

Amateur astronomy, a subset of astronomy, is a hobby whose participants enjoy studying and observing celestial objects....
 observations.

Discovery


Messier 81 was first discovered by Johann Elert Bode
Johann Elert Bode

Johann Elert Bode was a Germany astronomer known for his reformulation and popularization of the Titius-Bode law. Bode determined the orbit of Uranus and suggested the planet's name....
 in 1774. Consequently, the galaxy is sometimes referred to as "Bode's Galaxy". In 1779, Pierre Méchain
Pierre Méchain

Pierre Fran?ois Andr? M?chain was a France astronomer and surveying who, with Charles Messier, was a major contributor to the early study of deep sky objects and comets....
 and Charles Messier
Charles Messier

Charles Messier was a France astronomy most notable for publishing an astronomical catalog consisting of deep sky objects such as nebulae and star clusters that came to be known as the 103 "Messier objects"....
 reidentified Bode's object, which was subsequently listed in the Messier Catalogue.

Dust emission


Most of the emission at infrared
Infrared

Infrared radiation is electromagnetic radiation whose wavelength is longer than that of visible light , but shorter than that of terahertz radiation and microwaves ....
 wavelengths originates from interstellar dust. This interstellar dust is found primarily within the galaxy's spiral arms, and it has been shown to be associated with star formation
Star formation

Star formation is the process by which dense parts of molecular clouds collapse into a ball of Plasma to form a star. As a branch of astronomy star formation includes the study of the interstellar medium and giant molecular clouds as precursors to the star formation process and the study of young stellar objects and planet formation as its i...
 regions. The general explanation is that the hot, short-lived blue star
Blue star

A blue star is a stellar classification.Blue star or bluestar may also refer to:...
s that are found within star formation regions are very effective at heating the dust and hence enhancing the infrared dust emission from these regions.

Supernova


Only one supernova
Supernova

A supernova is a Astronomy#Stellar astronomy explosion. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months....
 has been detected in Messier 81. The supernova, named SN 1993J
SN 1993J

SN 1993J is a supernova observed in the galaxy M81. It was discovered on 28 March 1993 by F. Garcia in Spain. At the time, it was the second brightest supernova observed in the twentieth century....
, was discovered on 28 March 1993 by F. Garcia in Spain. At the time, it was the second brightest supernova observed in the twentieth century. The spectral characteristics of the supernova changed over time. Initially, it looked more like a type II supernova (a supernovae formed by the explosion of a giant star) with strong hydrogen
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
 spectral line
Spectral line

A spectral line is a dark or bright line in an otherwise uniform and continuous optical spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies....
 emission, but later the hydrogen lines faded and strong helium
Helium

Helium is a colorless, odorless, tasteless, non-toxic, inert monatomic chemical element that heads the noble gas group in the periodic table and whose atomic number is 2....
 spectral lines appeared, making the supernova look more like a type Ib. Moreover, the variations in SN 1993J's luminosity over time were not like the variations observed in other type II supernovae but did resemble the variations observed in type Ib supernovae. Hence, the supernova has been classified as a "type IIb", a transitory class between type II and type Ib. The scientific results from this supernova suggested that type Ib and Ic supernovae were actually formed through the explosions of giant stars through processes similar to what takes place in type II supernovae. The supernova was also used to estimate a distance of 8.5 ± 1.3 Mly (2.6 ± 0.4 Mpc
Parsec

The parsec is a units of measurement of astronomical units of length, equal to just under 31 orders_of_magnitude_#1012 kilometres , or about 3.26 light-years....
) to Messier 81.

Nearby galaxies and galaxy group information


Messier 81 is the largest galaxy in the M81 Group
M81 Group

The M81 Group is a group of galaxies in the constellation Ursa Major that contains the well-known galaxies Messier 81 and Messier 82 as well as several other galaxies with high apparent brightnesses....
, a group
Galaxy groups and clusters

Galaxy groups and clusters are the largest gravitationally-bound objects to have arisen thus far in the process of cosmic structure formation....
 of 34 galaxies located in the constellation Ursa Major. The distance from the Earth to the group is approximately 11.7 Mly
Light-year

A light-year or light year is a Units of measurement of length, equal to just under ten orders_of_magnitude_%28numbers%29#1012 kilometres....
 (3.6 Mpc
Parsec

The parsec is a units of measurement of astronomical units of length, equal to just under 31 orders_of_magnitude_#1012 kilometres , or about 3.26 light-years....
), making this one of the closest groups to the Local Group
Local Group

The Local Group is the galaxy groups and clusters of galaxy that includes our galaxy, the Milky Way. The group comprises over 50 galaxies , with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy....
, which contains the Milky Way
Milky Way

The Milky Way, sometimes called simply the Galaxy, is the galaxy in which the Solar System is located. It is a barred spiral galaxy that is part of the Local Group of galaxies....
.

M81 is gravitationally interacting
Interacting galaxy

Interacting galaxies are the result of one galaxy's gravity disturbing another galaxy. An example of minor interaction is a satellite galaxy disturbing the primary galaxy's spiral arms....
 with Messier 82
Messier 82

Messier 82 is the prototype galaxy nearby starburst galaxy about 12 million light-years away in the constellation Ursa Major. The starburst galaxy is five times as bright as the whole Milky Way and one hundred times as bright as our galaxy's center....
 and NGC 3077
NGC 3077

NGC 3077 is a smaller member of the M81 Group. It looks much like an elliptical galaxy. However, it is peculiar for two reasons. First, it shows wispy edges and scattered dust clouds that are probably a result of gravitational interaction with its larger neighbors, similar to the galaxy Messier 82....
. The interactions have stripped some hydrogen
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
 gas away from all three galaxies, leading to the formation of filamentary gas structures in the group. Moreover, the interactions have also caused some interstellar gas
Interstellar medium

In astronomy, the interstellar medium is the gas and cosmic dust that pervade interstellar space: the matter that exists between the stars within a galaxy....
 to fall into the centers of Messier 82 and NGC 3077, which has led to strong starburst activity
Starburst galaxy

A starburst galaxy is a galaxy in the process of an exceptionally high rate of star formation, compared to the usual star formation rate seen in most galaxies....
 (or the formation of many stars) within the centers of these two galaxies.

Amateur astronomy information


Messier 81 is located approximately 10° northwest of Alpha Ursae Majoris
Alpha Ursae Majoris

Alpha Ursae Majoris is the second-brightest star in the constellation of Ursa Major . It also has the traditional name Dubhe.It forms part of the Big Dipper , and is the northern of the pointers, the two stars of Ursa Major which point towards Polaris, the North Star....
 along with several other galaxies in the Messier 81 Group. Messier 81 and Messier 82 can both be viewed easily using binoculars
Binoculars

Binocular telescopes, or binoculars , are two identical or mirror-symmetry optical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes when viewing distant objects....
 and small telescope
Telescope

A telescope is an instrument designed for the observation of remote objects by the collection of electromagnetic radiation. The first known practically functioning telescopes were invented in the Netherlands at the beginning of the 17th century....
s. The two objects are generally not observable to the unaided eye, although highly experienced amateur astronomers may be able to see Messier 81 under exceptional observing conditions. Telescopes with aperture
Aperture

In optics, an aperture is a hole or an opening through which light is admitted. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of ray that come to a focus in the ....
s of 8 inch
Inch

An inch is the name of a Units of measurement of length in a number of different systems, including Imperial units, and United States customary units....
es or larger are needed to distinguish structure in the galaxy.

See also


  • M81 in fiction
    Galaxies in fiction

    Galaxy other than the Milky Way are popular settings for creators of science fiction, particularly those working with broad-scale space opera settings....
     (in the galaxies in fiction
    Galaxies in fiction

    Galaxy other than the Milky Way are popular settings for creators of science fiction, particularly those working with broad-scale space opera settings....
     article)
  • Bode's Galaxy
    Galaxies named after people

    A small number of galaxies or galaxy groups have been named after individual people. In most cases, the named individual was the person who discovered the object, who first brought attention to it, or who first studied it scientifically....


External links