Messier 81

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Messier 81
Messier 81 HST.jpg
The HST's view of M81, with its open star clusters, globular star clusters, and regions of fluorescent gas.
Observation data (J2000 epoch)
Constellation Ursa Major [1]
Right ascension 09h 55m 33.2s [2]
Declination +69° 3′ 55″ [2]
Redshift −0.000113
Heliocentric radial velocity −34
Galactocentric velocity73
Apparent magnitude  (V)6.94 [3] [4]
Characteristics
Type SA(s)ab, [2] LINER [2]
Size29.44 kiloparsecs (96,000 light-years)
(diameter; 25.0 mag/arcsec2 B-band isophote) [2] [5]
Apparent size  (V)26.9 × 14.1 moa [2]
Other designations
NGC 3031, UGC 5318, MCG+12-10-010, PGC  28630, Bode's Galaxy [3]

Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a grand design spiral galaxy about 12 million light-years away in the constellation Ursa Major. It has a D25 isophotal diameter of 29.44 kiloparsecs (96,000 light-years ). [2] [5] Because of its relative proximity to the Milky Way galaxy, large size, and active galactic nucleus (which harbors a 70 million M☉ [6] supermassive black hole), Messier 81 has been studied extensively by professional astronomers. The galaxy's large size and relatively high brightness also makes it a popular target for amateur astronomers. [7] In late February 2022, astronomers reported that M81 may be the source of FRB 20200120E, a repeating fast radio burst. [8] [9]

Contents

Discovery

Messier 81 was first discovered by Johann Elert Bode on 31 December 1774. [10] Thus, it is sometimes referred to as "Bode's Galaxy". In 1779, Pierre Méchain and Charles Messier reidentified Bode's object, hence listed it in the Messier Catalogue. [10]

Visibility

The galaxy is to be found approximately 10° northwest of Alpha Ursae Majoris (Dubhe) along with several other galaxies in the Messier 81 Group. [7] [11] Its apparent magnitude due to its distance means it requires a good night sky and only rises very briefly and extremely low at its southernmost limit from Earth's surface, about the 20th parallel south.

Messier 81 and Messier 82 are considered ideal for viewing using binoculars and small telescopes. [7] [11] 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 with a very dark sky. [7] [12] Telescopes with apertures of 8 inches (20 cm) or larger are needed to distinguish structures in the galaxy. [11]

An infrared image of Messier 81 taken by the Spitzer Space Telescope. The blue colors represent stellar emission observed at 3.6 mm. The green colors represent 8 mm emission originating primarily from polycyclic aromatic hydrocarbons in the interstellar medium. The red colors represent 24 mm emission originating from heated dust in the interstellar medium. Messier81 highres.jpg
An infrared image of Messier 81 taken by the Spitzer Space Telescope. The blue colors represent stellar emission observed at 3.6 μm. The green colors represent 8 μm emission originating primarily from polycyclic aromatic hydrocarbons in the interstellar medium. The red colors represent 24 μm emission originating from heated dust in the interstellar medium.

The galaxy is best observed during April. [15]

Interstellar dust

Most of the emission at infrared wavelengths originates from interstellar dust. [14] [16] This interstellar dust is found primarily within the galaxy's spiral arms, and it has been shown to be associated with star formation regions. [14] [16] The general explanation is that the hot, short-lived blue stars that are found within star formation regions are very effective at heating the dust and thus enhancing the infrared dust emission from these regions.

Globular clusters

It is estimated M81 has 210 ± 30 globular clusters. [17] In late February 2022, astronomers reported that M81 may be the source of FRB 20200120E, a repeating fast radio burst. [8] [9]

Supernovae

M81 (left) and M82 (right). M82 is one of two galaxies strongly influenced gravitationally by M81. The other, NGC 3077, is located off the top edge of this image. AnttlersM81M82.jpg
M81 (left) and M82 (right). M82 is one of two galaxies strongly influenced gravitationally by M81. The other, NGC 3077, is located off the top edge of this image.
M81 with satellite galaxy Holmberg IX in the top center-right corner M81.jpg
M81 with satellite galaxy Holmberg IX in the top center-right corner

Only one supernova has been detected in Messier 81. [18] The supernova, named SN 1993J, was discovered on 28 March 1993 by F. García in Spain. [19] At the time, it was the second brightest supernova observed in the 20th century, [20] peaking at an apparent magnitude of 10.7. The spectral characteristics of the supernova changed over time. Initially, it looked more like a type II supernova (a supernova formed by the explosion of a supergiant star) with strong hydrogen spectral line emission, but later the hydrogen lines faded and strong helium spectral lines appeared, making the supernova look more like a type Ib. [20] [21]

Moreover, the variations in SN 1993J's luminosity over time were not like the variations observed in other type II supernovae, [22] [23] but did resemble the variations observed in type Ib supernovae. [24] Hence, the supernova has been classified as a type IIb, a transitory class between type II and type Ib. [21] The scientific results from this supernova suggested that type Ib and Ic supernovae were formed through the explosions of giant stars through processes similar to those taking place in type II supernovae. [21] [25] Despite the uncertainties in modeling the unusual supernova, it was also used to estimate a very approximate distance of 8.5 ± 1.3 Mly (2.6 ± 0.4 Mpc) to Messier 81. [20] As a local galaxy, the Central Bureau for Astronomical Telegrams (CBAT) tracks novae in M81 along with M31 and M33. [26]

Environment

Messier 81 is the largest galaxy in the M81 Group, a group of 34 in the constellation Ursa Major. [27] At approximately 11.7 Mly (3.6 Mpc) from the Earth, it makes this group and the Local Group, containing the Milky Way, [27] relative neighbors in the Virgo Supercluster.

Gravitational interactions of M81 with M82 and NGC 3077 [28] have stripped hydrogen gas away from all three galaxies, forming gaseous filamentary structures in the group. [28] Moreover, these interactions have allowed interstellar gas to fall into the centers of M82 and NGC 3077, leading to vigorous star formation or starburst activity there. [28]

Distance

The distance to Messier 81 has been measured by Freedman et al [29] to be 3.63 ± 0.34 Megaparsecs (11.8 ± 1.1 million light years) by using the Hubble Space Telescope to identify classical Cepheid variables and measure their periods using the period-luminosity relation discovered by Henrietta Swan Leavitt.

See also

Related Research Articles

<span class="mw-page-title-main">M81 Group</span> Galaxy group in Ursa Major and Camelopardalis

The M81 Group is a galaxy group in the constellations Ursa Major and Camelopardalis that includes the galaxies Messier 81 and Messier 82, as well as several other galaxies with high apparent brightnesses. The approximate center of the group is located at a distance of 3.6 Mpc, making it one of the nearest groups to the Local Group. The group is estimated to have a total mass of ×1012M☉. The M81 Group, the Local Group, and other nearby groups all lie within the Virgo Supercluster.

<span class="mw-page-title-main">Triangulum Galaxy</span> Spiral galaxy in the constellation Triangulum

The Triangulum Galaxy is a spiral galaxy 2.73 million light-years (ly) from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC (New General Catalogue) 598. With the D25 isophotal diameter of 18.74 kiloparsecs (61,100 light-years), the Triangulum Galaxy is the third-largest member of the Local Group of galaxies, behind the Andromeda Galaxy and the Milky Way.

<span class="mw-page-title-main">Messier 82</span> Starburst galaxy in the constellation Ursa Major

Messier 82 (also known as NGC 3034, Cigar Galaxy or M82) is a starburst galaxy approximately 12 million light-years away in the constellation Ursa Major. It is the second-largest member of the M81 Group, with the D25 isophotal diameter of 12.52 kiloparsecs (40,800 light-years). It is about five times more luminous than the Milky Way and its central region is about one hundred times more luminous. The starburst activity is thought to have been triggered by interaction with neighboring galaxy M81. As one of the closest starburst galaxies to Earth, M82 is the prototypical example of this galaxy type. SN 2014J, a type Ia supernova, was discovered in the galaxy on 21 January 2014. In 2014, in studying M82, scientists discovered the brightest pulsar yet known, designated M82 X-2.

<span class="mw-page-title-main">Pinwheel Galaxy</span> Galaxy in the constellation Ursa Major

The Pinwheel Galaxy is a face-on spiral galaxy 21 million light-years from Earth in the constellation Ursa Major. It was discovered by Pierre Méchain in 1781 and was communicated that year to Charles Messier, who verified its position for inclusion in the Messier Catalogue as one of its final entries.

<span class="mw-page-title-main">Messier 61</span> Galaxy in the constellation Virgo

Messier 61 is an intermediate barred spiral galaxy in the Virgo Cluster of galaxies. It was first discovered by Barnaba Oriani on May 5, 1779, six days before Charles Messier discovered the same galaxy. Messier had observed it on the same night as Oriani but had mistaken it for a comet. Its distance has been estimated to be 45.61 million light years from the Milky Way Galaxy. It is a member of the M61 Group of galaxies, which is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Supercluster.

<span class="mw-page-title-main">Centaurus A</span> Radio galaxy in the constellation Centaurus

Centaurus A is a galaxy in the constellation of Centaurus. It was discovered in 1826 by Scottish astronomer James Dunlop from his home in Parramatta, in New South Wales, Australia. There is considerable debate in the literature regarding the galaxy's fundamental properties such as its Hubble type and distance. NGC 5128 is one of the closest radio galaxies to Earth, so its active galactic nucleus has been extensively studied by professional astronomers. The galaxy is also the fifth-brightest in the sky, making it an ideal amateur astronomy target. It is only visible from the southern hemisphere and low northern latitudes.

<span class="mw-page-title-main">Whirlpool Galaxy</span> Galaxy in the constellation Canes Venatici

The Whirlpool Galaxy, also known as Messier 51a (M51a) or NGC 5194, is an interacting grand-design spiral galaxy with a Seyfert 2 active galactic nucleus. It lies in the constellation Canes Venatici, and was the first galaxy to be classified as a spiral galaxy. It is 7.22 megaparsecs away and 23.58 kiloparsecs (76,900 ly) in diameter.

<span class="mw-page-title-main">Messier 59</span> Elliptical galaxy in the constellation Virgo

Messier 59 or M59, also known as NGC 4621, is an elliptical galaxy in the equatorial constellation of Virgo. It is a member of the Virgo Cluster, with the nearest fellow member 8′ away and around 5 magnitudes fainter. The nearest cluster member of comparable brightness is the lenticular galaxy NGC 4638, which is around 17′ away. It and the angularly nearby elliptical galaxy Messier 60 were both discovered by Johann Gottfried Koehler in April 1779 when observing comet seeming close by. Charles Messier listed both in the Messier Catalogue about three days after Koehler's discovery.

<span class="mw-page-title-main">Messier 74</span> Face-on spiral galaxy in the constellation Pisces

Messier 74 is a large spiral galaxy in the equatorial constellation Pisces. It is about 32 million light-years away from Earth. The galaxy contains two clearly defined spiral arms and is therefore used as an archetypal example of a grand design spiral galaxy. The galaxy's low surface brightness makes it the most difficult Messier object for amateur astronomers to observe. Its relatively large angular size and the galaxy's face-on orientation make it an ideal object for professional astronomers who want to study spiral arm structure and spiral density waves. It is estimated that M74 hosts about 100 billion stars.

<span class="mw-page-title-main">Messier 108</span> Galaxy in the constellation Ursa Major

Messier 108 is a barred spiral galaxy about 28 million light-years away from Earth in the northern constellation Ursa Major. It was discovered by Pierre Méchain in 1781 or 1782. From the Earth, this galaxy is seen almost edge-on.

<span class="mw-page-title-main">NGC 6946</span> Galaxy in the constellations Cepheus & Cygnus

NGC 6946, sometimes referred to as the Fireworks Galaxy, is a face-on intermediate spiral galaxy with a small bright nucleus, whose location in the sky straddles the boundary between the northern constellations of Cepheus and Cygnus. Its distance from Earth is about 25.2 million light-years or 7.72 megaparsecs, similar to the distance of M101 in the constellation Ursa Major. Both were once considered to be part of the Local Group, but are now known to be among the dozen bright spiral galaxies near the Milky Way but beyond the confines of the Local Group. NGC 6946 lies within the Virgo Supercluster.

<span class="mw-page-title-main">NGC 4725</span> Galaxy in the constellation Coma Berenices

NGC 4725 is an intermediate barred spiral galaxy with a prominent ring structure, located in the northern constellation of Coma Berenices near the north galactic pole. It was discovered by German-born astronomer William Herschel on April 6, 1785. The galaxy lies at a distance of approximately 40 megalight-years from the Milky Way. NGC 4725 is the brightest member of the Coma I Group of the Coma-Sculptor Cloud, although it is relatively isolated from the other members of this group. This galaxy is strongly disturbed and is interacting with neighboring spiral galaxy NGC 4747, with its spiral arms showing indications of warping. The pair have an angular separation of 24′, which corresponds to a projected linear separation of 370 kly. A tidal plume extends from NGC 4747 toward NGC 4725.

<span class="mw-page-title-main">SN 1994D</span> Type Ia supernova

SN 1994D was a Type Ia supernova event in the outskirts of galaxy NGC 4526. It was offset by 9.0″ west and 7.8″ south of the galaxy center and positioned near a prominent dust lane. It was caused by the explosion of a white dwarf star composed of carbon and oxygen. This event was discovered on March 7, 1994 by R. R. Treffers and associates using the automated 30-inch telescope at Leuschner Observatory. It reached peak visual brightness two weeks later on March 22. Modelling of the light curve indicates the explosion would have been visible around March 3-4. A possible detection of helium in the spectrum was made by W. P. S. Meikle and associates in 1996. A mass of 0.014 to 0.03 M☉ in helium would be needed to produce this feature.

<span class="mw-page-title-main">NGC 1309</span> Spiral galaxy in the constellation Eridanus

NGC 1309 is a spiral galaxy located approximately 120 million light-years away, appearing in the constellation Eridanus. It is about 75,000 light-years across, and is about 3/4s the width of the Milky Way. Its shape is classified as SA(s)bc, meaning that it has moderately wound spiral arms and no ring. Bright blue areas of star formation can be seen in the spiral arms, while the yellowish central nucleus contains older-population stars. NGC 1309 is one of over 200 members of the Eridanus Group of galaxies.

<span class="mw-page-title-main">NGC 4605</span> Galaxy in the constellation Ursa Major

NGC 4605 is a dwarf barred spiral galaxy in the constellation Ursa Major, located at a distance of 18.1 ± 0.3 megalight-years from the Milky Way. Physically it is similar in size and in B-band absolute magnitude to the Large Magellanic Cloud. It is a member of the M81 Galaxy Group, along with Messier 81 and Messier 101.

<span class="mw-page-title-main">SN 1993J</span> Supernova in the spiral galaxy Messier 81

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 type II supernova observed in the twentieth century behind SN 1987A, peaking at a visible apparent magnitude of 10.7 on March 30, with a second peak of 10.86 on April 18.

SN 1990U was a type Ic supernova event in the nucleus of the galaxy NGC 7479. It was discovered July 27, 1990 by the Berkeley Automated Supernova Search after reaching magnitude 16±0.5. Initially this was classified as a Type Ib supernova, but the weakness of the neutral helium absorption lines led to a reclassification.

<span class="mw-page-title-main">SN 2014J</span> Supernova in Messier 82

SN 2014J was a type-Ia supernova in Messier 82 discovered in mid-January 2014. It was the closest type-Ia supernova discovered for 42 years, and no subsequent supernova has been closer as of 2023. The supernova was discovered by chance during an undergraduate teaching session at the University of London Observatory. It peaked on 31 January 2014, reaching an apparent magnitude of 10.5. SN 2014J was the subject of an intense observing campaign by professional astronomers and was bright enough to be seen by amateur astronomers.

<span class="mw-page-title-main">NGC 7469</span> Galaxy located in the constellation Pegasus

NGC 7469 is an intermediate spiral galaxy in the constellation of Pegasus. NGC 7469 is located about 200 million light-years away from Earth, which means, given its apparent dimensions, that NGC 7469 is approximately 90,000 light-years across. It was discovered by William Herschel on November 12, 1784.

References

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  15. ↑ https://science.nasa.gov/mission/hubble/science/explore-the-night-sky/hubble-messier-catalog/messier-81/
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  17. ↑ Chandar, Rupali; Whitmore, Bradley; Lee, Myung Gyoon (10 August 2004). "The Globular Cluster Systems of Five Nearby Spiral Galaxies: New Insights from Hubble Space TelescopeImaging". The Astrophysical Journal. 611 (1): 220–244. arXiv: astro-ph/0407460 . Bibcode:2004ApJ...611..220C. doi: 10.1086/421934 . ISSN   0004-637X.
  18. ↑ "NASA/IPAC Extragalactic Database". Results for extended name search on NGC 3031. Retrieved 27 February 2007.
  19. ↑ Ripero, J.; Garcia, F.; Rodriguez, D.; Pujol, P.; Filippenko, A. V.; Treffers, R. R.; Paik, Y.; Davis, M.; Schlegel, D.; Hartwick, F. D. A.; Balam, D. D.; Zurek, D.; Robb, R. M.; Garnavich, P.; Hong, B. A. (1993). "Supernova 1993J in NGC 3031". IAU Circular . 5731: 1. Bibcode:1993IAUC.5731....1R.
  20. 1 2 3 Schmidt, B.P.; Kirshner, R.P.; Eastman, R.G.; Grashuis, R.; Dell'Antonio, I.; Caldwell, N.; Foltz, C.; Huchra, John P.; Milone, Alejandra A. E. (1993). "The unusual supernova SN1993J in the galaxy M81". Nature . 364 (6438): 600–602. Bibcode:1993Natur.364..600S. doi:10.1038/364600a0. S2CID   4304547.
  21. 1 2 3 Filippenko, A. V.; Matheson, T.; Ho, L. C. (1993). "The "Type IIb" Supernova 1993J in M81: A Close Relative of Type Ib Supernovae". Astrophysical Journal Letters . 415: L103–L106. Bibcode:1993ApJ...415L.103F. doi: 10.1086/187043 .
  22. ↑ Benson, P. J.; Herbst, W.; Salzer, J. J.; Vinton, G.; Hanson, G. J.; Ratcliff, S. J.; Winkler, P. F.; Elmegreen, D. M.; Chromey, F.; Strom, C.; Balonek, T. J.; Elmegreen, B. G. (1994). "Light curves of SN 1993J from the Keck Northeast Astronomy Consortium". Astronomical Journal . 107: 1453–1460. Bibcode:1994AJ....107.1453B. doi: 10.1086/116958 .
  23. ↑ Wheeler, J. C.; Barker, E.; Benjamin, R.; Boisseau, J.; Clocchiatti, A.; De Vaucouleurs, G.; Gaffney, N.; Harkness, R. P.; Khokhlov, A. M.; Lester, D. F.; Smith, B. J.; Smith, V. V.; Tomkin, J. (1993). "Early Observations of SN 1993J in M81 at McDonald Observatory". Astrophysical Journal . 417: L71–L74. Bibcode:1993ApJ...417L..71W. doi:10.1086/187097.
  24. ↑ Richmond, M. W.; Treffers, R. R.; Filippenko, A. V.; Palik, Y.; Leibundgut, B.; Schulman, E.; Cox, C. V. (1994). "UBVRI photometry of SN 1993J in M81: The first 120 days". Astronomical Journal . 107: 1022–1040. Bibcode:1994AJ....107.1022R. doi: 10.1086/116915 .
  25. ↑ Filippenko, A. V.; Matheson, T.; Barth, A. J. (1994). "The peculiar type II supernova 1993J in M81: Transition to the nebular phase". Astronomical Journal . 108: 2220–2225. Bibcode:1994AJ....108.2220F. doi:10.1086/117234.
  26. ↑ Bishop, David. "Extragalactic Novae". supernovae.net (International Supernovae Network). Archived from the original on 8 April 2010. Retrieved 11 September 2010.
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  29. ↑ Freedman, Wendy (1994). "The Hubble Space Telescope Extragalactic Distance Scale Project. I. The Discovery of Cepheids and a New Distance to M81". The Astrophysical Journal. 427 (June): 628–655. Bibcode:1994ApJ...427..628F. doi:10.1086/174172 – via Astrophysics Data System.
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