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Andromeda Galaxy
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{{Use dmy dates|date=April 2019}}{{short description|spiral galaxy within the Local Group}}







factoids
| type = SA(s)b1.5e=1212}}{{solar mass}}� and MA = 1.5 +0.5−0.4 × {{e|12}}{{solar mass}}� at a 68% level"JOURNAL
, Jorge, Peñarrubia
, Yin-Zhe, Ma
, Matthew G., Walker
, Alan W., McConnachie
, A dynamical model of the local cosmic expansion
, Monthly Notices of the Royal Astronomical Society
, 433
, 3
, 29 July 2014
, 2204–2222
, 2014MNRAS.443.2204P
, 10.1093/mnras/stu879, 1405.0306, ,
but compare "[we estimate] the virial mass and radius of the galaxy to be 0.8±0.1×{{e|12}}{{solar mass}}"JOURNAL
, Prajwal R., Kafle
, Sanjib, Sharma
, Geraint F., Lewis
, 3
, Aaron S. G., Robotham
, Simon P., Driver
, The Need for Speed: Escape velocity and dynamical mass measurements of the Andromeda Galaxy
, Monthly Notices of the Royal Astronomical Society
, 475
, 3
, 1 February 2018
, 4043–4054
, 2018MNRAS.475.4043K
, 0035-8711
, 10.1093/mnras/sty082, 1801.03949,
| size = ~220 kly (diameter)| stars = ~1 trillion (1012)| age = 5 to 9 billion yearsNEWS, Moskvitch, Katia, 25 November 2010, Andromeda 'born in a collision',weblink BBC News, 25 November 2010,weblink" title="web.archive.org/web/20101126042510weblink">weblink 26 November 2010, live, 0044.3}}+419}}light-year>Mly (778 ± 33 parsec){{efn>name=avg dist}}| z = z = −0.001001 (minus sign indicates blueshift)| h_radial_v = −301 ± 1 km/s| appmag_v = 3.44| size_v = 3.167° × 1°Andromeda (constellation)>Andromedaname=blue mag}}Messier object>M31, New General Catalogue 224, Uppsala General Catalogue>UGC 454, Principal Galaxies Catalogue 2557, Second Cambridge Catalogue of Radio Sources>2C 56 (Core), CGCG 535-17, MCG +07-02-016, IRAS 00400+4059, 2MASX J00424433+4116074, GC 116, h 50, Bode 3, Flamsteed 58, Hevelius 32, Ha 3.3, IRC +40013}}The Andromeda Galaxy (IPA: {{IPAc-en|æ|n|ˈ|d|r|ɒ|m|ᵻ|d|ə}}), also known as Messier 31, M31, or NGC 224 and originally the Andromeda Nebula (see below), is a spiral galaxy approximately 780 kiloparsecs (2.5 million light-years) from Earth, and the nearest major galaxy to the Milky Way. The galaxy's name stems from the area of the Earth's sky in which it appears, the constellation of Andromeda.The virial mass of the Andromeda Galaxy is of the same order of magnitude as that of the Milky Way, at a trillion solar masses ({{val|e=12}}{{solar mass}}). The mass of either galaxy is difficult to estimate with any accuracy, but it was long thought that the Andromeda Galaxy is more massive than the Milky Way by a margin of some 25% to 50%. This has been called into question by a 2018 study which cited a lower estimate on the mass of the Andromeda Galaxy,JOURNAL
, Prajwal R., Kafle
, Sanjib, Sharma
, Geraint F., Lewis
, 3
, Aaron S. G., Robotham
, Simon P., Driver
, The Need for Speed: Escape velocity and dynamical mass measurements of the Andromeda Galaxy
, Monthly Notices of the Royal Astronomical Society
, 475
, 3
, 1 February 2018
, 4043–4054
, 2018MNRAS.475.4043K
, 0035-8711
, 10.1093/mnras/sty082, 1801.03949,
combined with preliminary reports on a 2019 study estimating a higher mass of the Milky Way."Milky Way tips the scales at 1.5 trillion solar masses" (11 March 2019). AstronomyNow.com. Retrieved 13 July 2019.Mahon, Chris (20 May 2018). "New Research Says the Milky Way Is Far Bigger Than We Thought Possible." OuterPlaces.com. Retrieved 13 July 2019. The Andromeda Galaxy has a diameter of about 220,000 light-years, making it the largest member of the Local Group at least in terms of extension, if not mass.The number of stars contained in the Andromeda Galaxy is estimated at one trillion ({{val|1|e=12}}), or roughly twice the number estimated for the Milky Way.JOURNAL
, Jorge, Peñarrubia
, Yin-Zhe, Ma
, Matthew G., Walker
, Alan W., McConnachie
, A dynamical model of the local cosmic expansion
, Monthly Notices of the Royal Astronomical Society
, 433
, 3
, 29 July 2014
, 2204–2222
, 2014MNRAS.443.2204P
, 10.1093/mnras/stu879, 1405.0306,
The Milky Way and Andromeda galaxies are expected to collide in around 4.5 billion years, merging to form a giant elliptical galaxy or a large lenticular galaxy.JOURNAL
, Junko
, Ueda
, Daisuke, Iono
, Min S., Yun
, 3
, Alison F., Crocker
, Desika, Narayanan
, Shinya, Komugi
, Daniel, Espada
, Bunyo, Hatsukade
, Hiroyuki, Kaneko
, Yuichi, Matsuda
, Yoichi, Tamura
, David J., Wilner
, Ryohei, Kawabe
, Hsi-An, Pan
, Cold molecular gas in merger remnants. I. Formation of molecular gas disks
, The Astrophysical Journal Supplement Series
, 214
, 1
, 1
, 2014ApJS..214....1U
, 10.1088/0067-0049/214/1/1
, 1407.6873, 2014
,
With an apparent magnitude of 3.4, the Andromeda Galaxy is among the brightest of the Messier objects making it visible to the naked eye from Earth on moonless nights,WEB,weblink M 31, M 32 & M 110, 15 October 2016, even when viewed from areas with moderate light pollution.

Observation history

File:Pic iroberts1.jpg|thumb|left|Great Andromeda Nebula by Isaac RobertsIsaac RobertsAround the year 964, the Persian astronomer Abd al-Rahman al-Sufi was the first to describe the Andromeda Galaxy. He referred to it in his Book of Fixed Stars as a "nebulous smear".JOURNAL
, Hafez
, Ihsan
, 2010
, Abd al-Rahman al-Sufi and his book of the fixed stars: a journey of re-discovery.
,weblink
, Ph.D. Thesis, James Cook University.
,
,
, 23 June 2016, 2010PhDT.......295H
,
Star charts of that period labeled it as the Little Cloud. In 1612, the German astronomer Simon Marius gave an early description of the Andromeda Galaxy based on telescopic observations. Pierre Louis Maupertuis conjectured in 1745 that the blurry spot was an island universe.Kant, Immanuel, Universal Natural History and Theory of the Heavens (1755) In 1764, Charles Messier cataloged Andromeda as object M31 and incorrectly credited Marius as the discoverer despite it being visible to the naked eye. In 1785, the astronomer William Herschel noted a faint reddish hue in the core region of Andromeda. He believed Andromeda to be the nearest of all the "great nebulae", and based on the color and magnitude of the nebula, he incorrectly guessed that it was no more than 2,000 times the distance of Sirius, or roughly 18,000 light years. In 1850, William Parsons, 3rd Earl of Rosse made the first drawing of Andromeda's spiral structure.In 1864, William Huggins noted that the spectrum of Andromeda differed from that of a gaseous nebula. The spectra of Andromeda displays a (wikt:continuum|continuum) of frequencies, superimposed with dark absorption lines that help identify the chemical composition of an object. Andromeda's spectrum is very similar to the spectra of individual stars, and from this, it was deduced that Andromeda has a stellar nature. In 1885, a supernova (known as S Andromedae) was seen in Andromeda, the first and so far only one observed in that galaxy. At the time Andromeda was considered to be a nearby object, so the cause was thought to be a much less luminous and unrelated event called a nova, and was named accordingly; "Nova 1885".In 1887, Isaac Roberts took the first photographs of Andromeda, which was still commonly thought to be a nebula within our galaxy. Roberts mistook Andromeda and similar spiral nebulae as solar systems being formed.{{citation needed |date=April 2012}} In 1912, Vesto Slipher used spectroscopy to measure the radial velocity of Andromeda with respect to our Solar System—the largest velocity yet measured, at {{convert|300|km/s|abbr=off}}.

Island universe

(File: Andromeda constellation map.svg|thumb|right|Location of the Andromeda Galaxy (M31) in the Andromeda constellation.)In 1917, Heber Curtis observed a nova within Andromeda. Searching the photographic record, 11 more novae were discovered. Curtis noticed that these novae were, on average, 10 magnitudes fainter than those that occurred elsewhere in the sky. As a result, he was able to come up with a distance estimate of {{convert|500000|ly}}. He became a proponent of the so-called "island universes" hypothesis, which held that spiral nebulae were actually independent galaxies.File:Над VLT – две галактики, видимые простым глазом.jpg|thumb|left| Andromeda Galaxy above the Very Large Telescope.NEWS, Two naked-eye galaxies above the VLT,weblink 22 October 2013, ESO Picture of the Week, The Triangulum GalaxyTriangulum GalaxyIn 1920, the Great Debate between Harlow Shapley and Curtis took place concerning the nature of the Milky Way, spiral nebulae, and the dimensions of the Universe. To support his claim of the Great Andromeda Nebula being, in fact, an external galaxy, Curtis also noted the appearance of dark lanes within Andromeda which resembled the dust clouds in our own galaxy, as well as historical observations of Andromeda Galaxy's significant Doppler shift. In 1922 Ernst Öpik presented a method to estimate the distance of Andromeda using the measured velocities of its stars. His result placed the Andromeda Nebula far outside our galaxy at a distance of about {{convert|450000|pc|abbr=off}}. Edwin Hubble settled the debate in 1925 when he identified extragalactic Cepheid variable stars for the first time on astronomical photos of Andromeda. These were made using the {{convert|2.5|m|adj=on}} Hooker telescope, and they enabled the distance of Great Andromeda Nebula to be determined. His measurement demonstrated conclusively that this feature was not a cluster of stars and gas within our own galaxy, but an entirely separate galaxy located a significant distance from the Milky Way.In 1943, Walter Baade was the first person to resolve stars in the central region of the Andromeda Galaxy. Baade identified two distinct populations of stars based on their metallicity, naming the young, high-velocity stars in the disk Type I and the older, red stars in the bulge Type II. This nomenclature was subsequently adopted for stars within the Milky Way, and elsewhere. (The existence of two distinct populations had been noted earlier by Jan Oort.) Baade also discovered that there were two types of Cepheid variables, which resulted in a doubling of the distance estimate to Andromeda, as well as the remainder of the Universe.In 1950, radio emission from the Andromeda Galaxy was detected by Hanbury Brown and Cyril Hazard at Jodrell Bank Observatory. The first radio maps of the galaxy were made in the 1950s by John Baldwin and collaborators at the Cambridge Radio Astronomy Group. The core of the Andromeda Galaxy is called 2C 56 in the 2C radio astronomy catalog. In 2009, the first planet may have been discovered in the Andromeda Galaxy. This was detected using a technique called microlensing, which is caused by the deflection of light by a massive object.

General

The estimated distance of the Andromeda Galaxy from our own was doubled in 1953 when it was discovered that there is another, dimmer type of Cepheid. In the 1990s, measurements of both standard red giants as well as red clump stars from the Hipparcos satellite measurements were used to calibrate the Cepheid distances.

Formation and history

File:WISE- Andromeda.jpg|thumb|left|The Andromeda Galaxy as seen by NASA's Wide-field Infrared Survey ExplorerWide-field Infrared Survey ExplorerThe Andromeda Galaxy was formed roughly 10 billion years ago from the collision and subsequent merger of smaller protogalaxies.DAVIDGE > FIRST1 = TIMOTHY (TIM) J. FIRST2 = ALAN W. FIRST3 = MARK A., 3 first4 = Jürgen first5 = David first6 = Scott C. first7 = Geraint F. first8 = Robert Michael, 2012, The Recent Stellar Archeology of M31 – The Nearest Red Disk Galaxy, The Astrophysical Journal, 751, 1, 2012ApJ...751...74D, 10.1088/0004-637X/751/1/74, 1203.6081, 74, This violent collision formed most of the galaxy's (metal-rich) galactic halo and extended disk. During this epoch, its rate of star formation would have been very high, to the point of becoming a luminous infrared galaxy for roughly 100 million years. Andromeda and the Triangulum Galaxy had a very close passage 2–4 billion years ago. This event produced high rates of star formation across the Andromeda Galaxy's disk—even some globular clusters—and disturbed M33's outer disk.Over the past 2 billion years, star formation throughout Andromeda's disk is thought to have decreased to the point of near-inactivity. There have been interactions with satellite galaxies like M32, M110, or others that have already been absorbed by Andromeda Galaxy. These interactions have formed structures like Andromeda's Giant Stellar Stream. A galactic merger roughly 100 million years ago is believed to be responsible for a counter-rotating disk of gas found in the center of Andromeda as well as the presence there of a relatively young (100 million years old) stellar population.

Distance estimate

At least four distinct techniques have been used to estimate distances from Earth to the Andromeda Galaxy. In 2003, using the infrared surface brightness fluctuations (I-SBF) and adjusting for the new period-luminosity value and a metallicity correction of −0.2 mag dex−1 in (O/H), an estimate of {{convert|2.57|+/-|0.06|e6ly|lk=on|abbr=off}} was derived. A 2004 Cepheid variable method estimated the distance to be 2.51 ± 0.13 million light-years (770 ± 40 kpc). In 2005, an eclipsing binary star was discovered in the Andromeda Galaxy. The binary{{efn|name=M31VJ}} is two hot blue stars of types O and B. By studying the eclipses of the stars, astronomers were able to measure their sizes. Knowing the sizes and temperatures of the stars, they were able to measure their absolute magnitude. When the visual and absolute magnitudes are known, the distance to the star can be calculated. The stars lie at a distance of {{convert|2.52|+/-|0.14|e6ly|abbr=on}} and the whole Andromeda Galaxy at about {{convert|2.5|e6ly|abbr=on}}. This new value is in excellent agreement with the previous, independent Cepheid-based distance value. The TRGB method was also used in 2005 giving a distance of {{convert|2.56|+/-|0.08|e6ly|abbr=on}}. Averaged together, these distance estimates give a value of {{convert|2.54|+/-|0.11|e6ly|abbr=on}}.{{efn|name=avg dist}} And, from this, the diameter of Andromeda at the widest point is estimated to be {{convert|220|+/-|3|kly|abbr=on}}.{{original research inline|inline|date=October 2016}} Applying trigonometry (angular diameter), this is equivalent to an apparent 4.96° angle in the sky.

Mass estimates

File:Andromeda galaxy.jpg|thumb|left|The Andromeda Galaxy pictured in ultraviolet light by GALEXGALEX(File:Milky Way and Andromeda in space, to scale.jpg|thumb|right|Illustration showing both the size of each galaxy and the distance between the two galaxies, to scale.)(File: Hubble Finds Giant Halo Around the Andromeda Galaxy.jpg|thumb|right|Giant halo around Andromeda Galaxy.WEB, Hubble Finds Giant Halo Around the Andromeda Galaxy,weblink 14 June 2015, )Until 2018, mass estimates for the Andromeda Galaxy's halo (including dark matter) gave a value of approximately {{Solar mass|1.5{{e|12}}|link=y}} (or 1.5 trillion solar masses) compared to {{Solar mass|8{{e|11}}}} for the Milky Way. This contradicted earlier measurements, that seemed to indicate that Andromeda Galaxy and the Milky Way are almost equal in mass. In 2018, the equality of mass was re-established by radio results as approximately {{Solar mass|8{{e|11}}}}JOURNAL
, Kafle, Prajwal R.
, Sharma, Sanjib
, Lewis, Geraint F.
, 3
, Robotham, Aaron S. G.
, Driver, Simon P.
, The need for speed: escape velocity and dynamical mass measurements of the Andromeda galaxy
, Monthly Notices of the Royal Astronomical Society (MNRAS)
, 2018
, 475
, 3
, 4043–4054
, 2018MNRAS.475.4043K
, 10.1093/mnras/sty082, 1801.03949,
JOURNAL, 1801.03949, 10.1093/mnras/sty082, The need for speed: Escape velocity and dynamical mass measurements of the Andromeda galaxy, Monthly Notices of the Royal Astronomical Society, 475, 3, 4043–4054, 2018, Kafle, Prajwal R., Sharma, Sanjib, Lewis, Geraint F., Robotham, Aaron S G., Driver, Simon P., 2018MNRAS.475.4043K, WEB,weblink Milky Way ties with neighbour in galactic arms race, 15 February 2018, WEB,weblink The Andromeda Galaxy Is Not Bigger Than the Milky Way After All, Samantha Mathewson 2018-02-20T19:05:26Z, Science, Astronomy, Space.com, In 2006, Andromeda Galaxy's spheroid was determined to have a higher stellar density than that of the Milky Way and its galactic stellar disk was estimated at about twice the diameter of that of the Milky Way. The total stellar mass of Andromeda Galaxy is estimated to be between {{Solar mass|8{{e|11}}}} and {{Solar mass|1.1{{e|12}}}}.,JOURNAL
, Barmby, Pauline
, Ashby, Matthew L. N.
, Bianchi, Luciana
, 3
, Engelbracht, Charles W.
, Gehrz, Robert D.
, Gordon, Karl D.
, Hinz, Joannah L.
, Huchra, John P.
, Humphreys, Roberta M.
, Pahre, Michael A.
, Pérez-González, Pablo G.
, Polomski, Elisha F.
, Rieke, George H.
, Thilker, David A.
, Willner, Steven P.
, Woodward, Charles E.
, Dusty Waves on a Starry Sea: The Mid-Infrared View of M31
, The Astrophysical Journal
, 2006
, 650
, 1
, L45–L49
, 2006ApJ...650L..45B
, 10.1086/508626, astro-ph/0608593, JOURNAL
, Barmby, Pauline
, Ashby, Matthew L. N.
, Bianchi, Luciana
, 3
, Engelbracht, Charles W.
, Gehrz, Robert D.
, Gordon, Karl D.
, Hinz, Joannah L.
, Huchra, John P.
, Humphreys, Roberta M.
, Pahre, Michael A.
, Pérez-González, Pablo G.
, Polomski, Elisha F.
, Rieke, George H.
, Thilker, David A.
, Willner, Steven P.
, Woodward, Charles E.
, Erratum: Dusty Waves on a Starry Sea: The Mid-Infrared View of M31
, The Astrophysical Journal
, 2007
, 655
, 1
, L61
, 2007ApJ...655L..61B
, 10.1086/511682, (i.e., around twice as massive as that of the Milky Way) and {{Solar mass|1.5{{e|12}}}}, with around 30% of that mass in the central bulge, 56% in the disk, and the remaining 14% in the halo.JOURNAL
, Tamm, Antti
, Tempel, Elmo
, Tenjes, Peeter
, 3
, Tihhonova, Olga
, Tuvikene, Taavi
, Stellar mass map and dark matter distribution in M 31
, Astronomy & Astrophysics
, 2012
, 546
, 2012A&A...546A...4T
, 10.1051/0004-6361/201220065, 1208.5712
, A4, The radio results (similar mass to Milky Way galaxy) should be taken as likeliest as of 2018, although clearly this matter is still under active investigation by a number of research groups worldwide.
As of 2019 current calculations based on escape velocity and dynamical mass measurements puts the Andromeda Galaxy at {{Solar mass|0.8{{e|12}}}} url=https://arxiv.org/abs/1801.03949, which is only half of the Milky Way's new mass calculations done in 2019, at {{Solar mass|1.5{{e|12}}}} url=https://scitechdaily.com/hubble-gaia-reveal-weight-of-the-milky-way-1-5-trillion-solar-masses/.In addition to stars, Andromeda Galaxy's interstellar medium contains at least around {{Solar mass|7.2{{e|9}}}}JOURNAL
, Braun, Robert
, Thilker, David A.
, Walterbos, René A. M.
, Corbelli, Edvige
, A Wide-Field High-Resolution H I Mosaic of Messier 31. I. Opaque Atomic Gas and Star Formation Rate Density
, The Astrophysical Journal
, 2009
, 695
, 2
, 937–953
, 2009ApJ...695..937B
, 10.1088/0004-637X/695/2/937, 0901.4154, in the form of neutral hydrogen, at least {{Solar mass|3.4{{e|8}}}} as molecular hydrogen (within its innermost 10 kiloparsecs), and {{Solar mass|5.4{{e|7}}}} of dust.JOURNAL
, Draine, Bruce T.
, Aniano, Gonzalo
, Krause, Oliver
, 3
, Groves, Brent
, Sandstrom, Karin
, Braun, Robert
, Leroy, Adam
, Klaas, Ulrich
, Linz, Hendrik
, Rix, Hans-Walter
, Schinnerer, Eva
, Schmiedeke, Anika
, Walter, Fabian
, Andromeda's Dust
, The Astrophysical Journal
, 2014
, 780
, 2
, 2014ApJ...780..172D
, 10.1088/0004-637X/780/2/172, 1306.2304
, 172,
Andromeda Galaxy is surrounded by a massive halo of hot gas that is estimated to contain half the mass of the stars in the galaxy. The nearly invisible halo stretches about a million light-years from its host galaxy, halfway to our Milky Way galaxy. Simulations of galaxies indicate the halo formed at the same time as the Andromeda Galaxy. The halo is enriched in elements heavier than hydrogen and helium, formed from supernovae and its properties are those expected for a galaxy that lies in the "green valley" of the Galaxy color–magnitude diagram (see below). Supernovae erupt in Andromeda Galaxy's star-filled disk and eject these heavier elements into space. Over Andromeda Galaxy's lifetime, nearly half of the heavy elements made by its stars have been ejected far beyond the galaxy's 200,000-light-year-diameter stellar disk.WEB, HubbleSite - NewsCenter - Hubble Finds Giant Halo Around the Andromeda Galaxy (05/07/2015) - The Full Story,weblink hubblesite.org, 7 May 2015, HUBBLE FINDS MASSIVE HALO AROUND THE ANDROMEDA GALAXY >URL = HTTPS://NEWS.ND.EDU/NEWS/HUBBLE-FINDS-HALO-AROUND-THE-ANDROMEDA-GALAXY/ DATE = 7 MAY 2015 LAST=GEBHARD, EVIDENCE FOR A MASSIVE, EXTENDED CIRCUMGALACTIC MEDIUM AROUND THE ANDROMEDA GALAXY >JOURNAL = THE ASTROPHYSICAL JOURNAL DATE = 25 APRIL 2014 LAST = LEHNER LAST2 = HOWK LAST3 = WAKKER BIBCODE=2015APJ...804...79L ISSUE = 2 ACCESSDATE = 7 MAY 2015, 7 May 2015,

Luminosity estimates

Compared to the Milky Way, the Andromeda Galaxy appears to have predominantly older stars with ages >7{{e|9}} years.{{clarify|date=January 2016}} The estimated luminosity of Andromeda Galaxy, {{Solar luminosity|~2.6{{e|10}}|link=y}}, is about 25% higher than that of our own galaxy. However, the galaxy has a high inclination as seen from Earth and its interstellar dust absorbs an unknown amount of light, so it is difficult to estimate its actual brightness and other authors have given other values for the luminosity of the Andromeda Galaxy (some authors even propose it is the second-brightest galaxy within a radius of 10 mega-parsecs of the Milky Way, after the Sombrero Galaxy,JOURNAL
, Karachentsev, Igor D.
, Karachentseva, Valentina E.
, Huchtmeier, Walter K.
, Makarov, Dmitry I.
, A Catalog of Neighboring Galaxies
, The Astronomical Journal
, 2003
, 127
, 4
, 2031–2068
, 2004AJ....127.2031K
, 10.1086/382905, with an absolute magnitude of around -22.21{{efn|name=bright m31}} or closeJOURNAL
, McCall, Marshall L.
, A Council of Giants
, Monthly Notices of the Royal Astronomical Society
, 2014
, 440
, 1
, 405–426
, 2014MNRAS.440..405M
, 10.1093/mnras/stu199, 1403.3667, ).
An estimation done with the help of Spitzer Space Telescope published in 2010 suggests an absolute magnitude (in the blue) of −20.89 (that with a color index of +0.63 translates to an absolute visual magnitude of −21.52,{{efn|name=blue mag}} compared to −20.9 for the Milky Way), and a total luminosity in that wavelength of {{Solar luminosity|3.64{{e|10}}}}.JOURNAL
, Tempel, Elmo
, Tamm, Antti
, Tenjes, Peeter
, Dust-corrected surface photometry of M 31 from Spitzer far-infrared observations
, Astronomy and Astrophysics
, 2010
, 509
, wA91
, 2010A&A...509A..91T
, 10.1051/0004-6361/200912186, 0912.0124
, A91,
The rate of star formation in the Milky Way is much higher, with Andromeda Galaxy producing only about one solar mass per year compared to 3–5 solar masses for the Milky Way. The rate of novae in the Milky Way is also double that of Andromeda Galaxy. This suggests that the latter once experienced a great star formation phase, but is now in a relative state of quiescence, whereas the Milky Way is experiencing more active star formation. Should this continue, the luminosity of the Milky Way may eventually overtake that of Andromeda Galaxy.According to recent studies, the Andromeda Galaxy lies in what in the galaxy color–magnitude diagram is known as the "green valley", a region populated by galaxies like the Milky Way in transition from the "blue cloud" (galaxies actively forming new stars) to the "red sequence" (galaxies that lack star formation). Star formation activity in green valley galaxies is slowing as they run out of star-forming gas in the interstellar medium. In simulated galaxies with similar properties to Andromeda Galaxy, star formation is expected to extinguish within about five billion years from the now, even accounting for the expected, short-term increase in the rate of star formation due to the collision between Andromeda Galaxy and the Milky Way.JOURNAL, 10.1088/0004-637X/736/2/84, The Mid-life Crisis of the Milky Way and M31, 2011 first=Simon J. first2=Darren J. first3=Gregory B., The Astrophysical Journal, 736, 2, 2011ApJ...736...84M, 1105.2564, 84,

Structure

File:Infraredandromeda.jpg|thumb|The Andromeda Galaxy seen in infrared by the Spitzer Space Telescope, one of NASA's four Great Space Observatories.]]File:Andromeda galaxy Ssc2005-20a1.jpg|thumb|Image of the Andromeda Galaxy taken by Spitzer in infrared, 24 micrometres (Credit:NASA/JPL–Caltech/Karl D. Gordon, University of ArizonaUniversity of ArizonaFile: A Swift Tour of M31.OGG|thumb|A Swift Tour of Andromeda Galaxy.]]File: The Galaxy Next Door.jpg|thumb|A Galaxy Evolution Explorer image of the Andromeda Galaxy. The bands of blue-white making up the galaxy's striking rings are neighborhoods that harbor hot, young, massive stars. Dark blue-grey lanes of cooler dust show up starkly against these bright rings, tracing the regions where star formation is currently taking place in dense cloudy cocoons. When observed in visible light, Andromeda Galaxy's rings look more like spiral arms. The ultraviolet view shows that these arms more closely resemble the ring-like structure previously observed in infrared wavelengths with NASA's Spitzer Space TelescopeSpitzer Space TelescopeBased on its appearance in visible light, the Andromeda Galaxy is classified as an SA(s)b galaxy in the de Vaucouleurs–Sandage extended classification system of spiral galaxies. However, data from the 2MASS survey showed that Andromeda is actually a barred spiral galaxy, like the Milky Way, with Andromeda's bar oriented along its long axis.In 2005, astronomers used the Keck telescopes to show that the tenuous sprinkle of stars extending outward from the galaxy is actually part of the main disk itself. This means that the spiral disk of stars in the Andromeda Galaxy is three times larger in diameter than previously estimated. This constitutes evidence that there is a vast, extended stellar disk that makes the galaxy more than {{convert|220000|ly|pc|lk=on|abbr=off}} in diameter. Previously, estimates of the Andromeda Galaxy's size ranged from {{convert|70000|to|120000|ly|pc}} across.The galaxy is inclined an estimated 77° relative to Earth (where an angle of 90° would be viewed directly from the side). Analysis of the cross-sectional shape of the galaxy appears to demonstrate a pronounced, S-shaped warp, rather than just a flat disk. A possible cause of such a warp could be gravitational interaction with the satellite galaxies near the Andromeda Galaxy. The Galaxy M33 could be responsible for some warp in Andromeda's arms, though more precise distances and radial velocities are required.Spectroscopic studies have provided detailed measurements of the rotational velocity of the Andromeda Galaxy as a function of radial distance from the core. The rotational velocity has a maximum value of {{convert|225|km/s}} at {{convert|1300|ly|lk=on|abbr=off}} from the core, and it has its minimum possibly as low as {{convert|50|km/s}} at {{convert|7000|ly}} from the core. Further out, rotational velocity rises out to a radius of {{convert|33000|ly}}, where it reaches a peak of {{convert|250|km/s}}. The velocities slowly decline beyond that distance, dropping to around {{convert|200|km/s}} at {{convert|80000|ly}}. These velocity measurements imply a concentrated mass of about {{Solar mass|6{{e|9}}|link=y}} in the nucleus. The total mass of the galaxy increases linearly out to {{convert|45000|ly}}, then more slowly beyond that radius.The spiral arms of the Andromeda Galaxy are outlined by a series of HII regions, first studied in great detail by Walter Baade and described by him as resembling "beads on a string". His studies show two spiral arms that appear to be tightly wound, although they are more widely spaced than in our galaxy. His descriptions of the spiral structure, as each arm crosses the major axis of the Andromeda Galaxy, are as followsJOURNAL
, van den Bergh, Sidney
, The Stellar Populations of M31
, Publications of the Astronomical Society of the Pacific
, 1991
, 103
, 1053–1068
, 10.1086/132925
, 1991PASP..103.1053V, §pp1062BOOK
, Hodge, Paul W.
, Paul W. Hodge
, Galaxies and Cosmology
, 1966
, McGraw Hill
,weblink §pp92:{| class="wikitable"|+ Baade's spiral arms of M31
! Arms (N=cross M31's major axis at north, S=cross M31's major axis at south)! Distance from center (arcminutes) (N*/S*)! Distance from center (kpc) (N*/S*)! NotesN1/S1 3.4/1.7 0.7/0.4 Dust arms with no Stellar kinematics#OB associations of H II region>HII regions.N2/S28.0/10.01.7/2.1 Dust arms with some OB associations.N3/S325/305.3/6.3 As per N2/S2, but with some HII regions too.N4/S450/4711/9.9 Large numbers of OB associations, HII regions, and little dust.N5/S570/6615/14 As per N4/S4 but much fainter.N6/S691/9519/20 Loose OB associations. No dust visible.N7/S7110/11623/24 As per N6/S6 but fainter and inconspicuous.Since the Andromeda Galaxy is seen close to edge-on, it is difficult to study its spiral structure. Rectified images of the galaxy seem to show a fairly normal spiral galaxy, exhibiting two continuous trailing arms that are separated from each other by a minimum of about {{convert|13000|ly|lk=on|abbr=off}} and that can be followed outward from a distance of roughly {{convert|1600|ly}} from the core. Alternative spiral structures have been proposed such as a single spiral armJOURNAL
, Simien, François
, Pellet, André
, Monnet, Guy
, 3
, Athanassoula, Évangélie
, Maucherat, André J.
, Courtès, Georges
, The spiral structure of M31 – A morphological approach
, Astronomy and Astrophysics
, 1978
, 67
, 1
, 73–79
, 1978A&A....67...73S, or a flocculentJOURNAL
, Cold dust in M31 as mapped by ISO
, Haas, Martin
, The Interstellar Medium in M31 and M33. Proceedings 232. WE-Heraeus Seminar
, 2000
, 69–72
, 2000immm.proc...69H, pattern of long, filamentary, and thick spiral arms.JOURNAL
, Walterbos, René A. M.
, Kennicutt, Robert C. Jr.
, An optical study of stars and dust in the Andromeda galaxy
, Astronomy and Astrophysics
, 1988
, 198
, 61–86
, 1988A&A...198...61W,
The most likely cause of the distortions of the spiral pattern is thought to be interaction with galaxy satellites M32 and M110. This can be seen by the displacement of the neutral hydrogen clouds from the stars.In 1998, images from the European Space Agency's Infrared Space Observatory demonstrated that the overall form of the Andromeda Galaxy may be transitioning into a ring galaxy. The gas and dust within the galaxy is generally formed into several overlapping rings, with a particularly prominent ring formed at a radius of {{convert|32000|ly}} (10 kiloparsecs) from the core, nicknamed by some astronomers the ring of fire.BOOK
, Morrison, Heather
, Caldwell, Nelson
, Harding, Paul
, 3
, Kriessler, Jeff
, Rose, James A.
, Schiavon, Ricardo
, Young Star Clusters in M 31
, Galaxies in the Local Volume, Astrophysics and Space Science Proceedings
, 5
, 2008
, 227–230
, 2008ASSP....5..227M
, 10.1007/978-1-4020-6933-8_50, 0708.3856, Astrophysics and Space Science Proceedings
, 978-1-4020-6932-1
, This ring is hidden from visible light images of the galaxy because it is composed primarily of cold dust, and most of the star formation that is taking place in the Andromeda Galaxy is concentrated there.JOURNAL
, Pagani, Laurent
, Lequeux, James
, Cesarsky, Diego
, 3
, Donas, José
, Milliard, Bruno
, Loinard, Laurent
, Sauvage, Marc
, Mid-infrared and far-ultraviolet observations of the star-forming ring of M 31
, Astronomy & Astrophysics
, 1999
, 351
, 447–458
, 1999A&A...351..447P, astro-ph/9909347,
Later studies with the help of the Spitzer Space Telescope showed how Andromeda Galaxy's spiral structure in the infrared appears to be composed of two spiral arms that emerge from a central bar and continue beyond the large ring mentioned above. Those arms, however, are not continuous and have a segmented structure.JOURNAL
, Gordon, Karl D.
, Bailin, J.
, Engelbracht, Charles W.
, 3
, Rieke, George H.
, Misselt, K. A.
, Latter, W. B.
, Young, E. T.
, Ashby, Matthew L. N.
, Barmby, Pauline
, Gibson, B. K.
, Hines, D. C.
, Hinz, Joannah L.
, Krause, O.
, Levine, D. A.
, Marleau, F. R.
, Noriega-Crespo, A.
, Stolovy, S.
, Thilker, David A.
, Werner, M. W.
, Spitzer MIPS Infrared Imaging of M31: Further Evidence for a Spiral-Ring Composite Structure
, The Astrophysical Journal
, 2006
, 638
, L87–L92
, 2006ApJ...638L..87G
, 10.1086/501046, astro-ph/0601314
, 2,
Close examination of the inner region of the Andromeda Galaxy with the same telescope also showed a smaller dust ring that is believed to have been caused by the interaction with M32 more than 200  million years ago. Simulations show that the smaller galaxy passed through the disk of the Andromeda Galaxy along the latter's polar axis. This collision stripped more than half the mass from the smaller M32 and created the ring structures in Andromeda.It is the co-existence of the long-known large ring-like feature in the gas of Messier 31, together with this newly discovered inner ring-like structure, offset from the barycenter, that suggested a nearly head-on collision with the satellite M32, a milder version of the Cartwheel encounter.JOURNAL
, Block, David L.
, Bournaud, Frédéric
, Combes, Françoise
, 3
, Groess, Robert
, Barmby, Pauline
, Ashby, Matthew L. N.
, Fazio, Giovanni G.
, Pahre, Michael A.
, Willner, Steven P.
, An almost head-on collision as the origin of the two off-centre rings in the Andromeda galaxy
, Nature
, 2006
, 443
, 832–834
, 2006Natur.443..832B
, 10.1038/nature05184, astro-ph/0610543
, 1, 17051212,
Studies of the extended halo of the Andromeda Galaxy show that it is roughly comparable to that of the Milky Way, with stars in the halo being generally "metal-poor", and increasingly so with greater distance. This evidence indicates that the two galaxies have followed similar evolutionary paths. They are likely to have accreted and assimilated about 100–200 low-mass galaxies during the past 12 billion years. The stars in the extended halos of the Andromeda Galaxy and the Milky Way may extend nearly one third the distance separating the two galaxies.

Nucleus

File:Double Nucleus of the Andromeda Galaxy (M31).tif|thumb|left|Hubble image of the Andromeda Galaxy core showing possible double structure. NASA/ESA photo.]]M31 is known to harbor a dense and compact star cluster at its very center. In a large telescope it creates a visual impression of a star embedded in the more diffuse surrounding bulge. In 1991, the Hubble Space Telescope was used to image Andromeda Galaxy's inner nucleus. The nucleus consists of two concentrations separated by {{convert|1.5|pc|lk=on}}. The brighter concentration, designated as P1, is offset from the center of the galaxy. The dimmer concentration, P2, falls at the true center of the galaxy and contains a black hole measured at 3–5 × 107 {{Solar mass|link=y}} in 1993, and at 1.1–2.3 × 108 {{Solar mass}} in 2005. The velocity dispersion of material around it is measured to be ≈ 160 km/s.File:M31 Core in X-rays.jpg|thumb|Chandra X-ray telescope image of the center of Andromeda Galaxy. A number of X-ray sources, likely X-ray binary stars, within the galaxy's central region appear as yellowish dots. The blue source at the center is at the position of the supermassive black holesupermassive black holeIt has been proposed that the observed double nucleus could be explained if P1 is the projection of a disk of stars in an eccentric orbit around the central black hole. The eccentricity is such that stars linger at the orbital apocenter, creating a concentration of stars. P2 also contains a compact disk of hot, spectral-class A stars. The A stars are not evident in redder filters, but in blue and ultraviolet light they dominate the nucleus, causing P2 to appear more prominent than P1.While at the initial time of its discovery it was hypothesized that the brighter portion of the double nucleus is the remnant of a small galaxy "cannibalized" by Andromeda Galaxy, this is no longer considered a viable explanation, largely because such a nucleus would have an exceedingly short lifetime due to tidal disruption by the central black hole. While this could be partially resolved if P1 had its own black hole to stabilize it, the distribution of stars in P1 does not suggest that there is a black hole at its center.

Discrete sources

(File:PIA20061 - Andromeda in High-Energy X-rays, Figure 1.jpg|thumb|center|400px|The Andromeda Galaxy in high-energy X-ray and ultraviolet light (released 5 January 2016).)File: Andromeda active core.jpg|thumb|Artist's concept of the Andromeda Galaxy's core, showing a view across a disk of young, blue stars encircling a supermassive black hole. NASA/ESA photo.]]Apparently, by late 1968, no X-rays had been detected from the Andromeda Galaxy. A balloon flight on 20 October 1970, set an upper limit for detectable hard X-rays from the Andromeda Galaxy. The Swift BAT all-sky survey successfully detected hard X-rays coming from a region centered 6 arcseconds away from the galaxy center. The emission above 25 keV was later found to be originating from a single source named 3XMM J004232.1+411314, and identified as a binary system where a compact object (a neutron star or a black hole) accretes matter from a star.Multiple X-ray sources have since been detected in the Andromeda Galaxy, using observations from the European Space Agency's (ESA) XMM-Newton orbiting observatory. Robin Barnard et al. hypothesized that these are candidate black holes or neutron stars, which are heating the incoming gas to millions of kelvins and emitting X-rays. Neutron stars and black holes can be distinguished mainly by measuring their masses. An observation campaign of NuSTAR space mission identified 40 objects of this kind in the galaxy.WEB, Andromeda Galaxy Scanned with High-Energy X-ray Vision,weblink 22 September 2018, In 2012, a microquasar, a radio burst emanating from a smaller black hole was detected in the Andromeda Galaxy. The progenitor black hole is located near the galactic center and has about 10 begin{smallmatrix}M_odotend{smallmatrix}. It was discovered through data collected by the European Space Agency's XMM-Newton probe and was subsequently observed by NASA's Swift Gamma-Ray Burst Mission and Chandra X-Ray Observatory, the Very Large Array, and the Very Long Baseline Array. The microquasar was the first observed within the Andromeda Galaxy and the first outside of the Milky Way Galaxy.NEWS, Microquasar in Andromeda Galaxy Amazes Astronomers,weblink Sci-News.com, 14 December 2012, Sergio, Prostak,

Globular clusters

There are approximately 460 globular clusters associated with the Andromeda Galaxy. The most massive of these clusters, identified as Mayall II, nicknamed Globular One, has a greater luminosity than any other known globular cluster in the Local Group of galaxies. It contains several million stars, and is about twice as luminous as Omega Centauri, the brightest known globular cluster in the Milky Way. Globular One (or G1) has several stellar populations and a structure too massive for an ordinary globular. As a result, some consider G1 to be the remnant core of a dwarf galaxy that was consumed by Andromeda in the distant past. The globular with the greatest apparent brightness is G76 which is located in the south-west arm's eastern half.Another massive globular cluster, named 037-B327 and discovered in 2006 as is heavily reddened by the Andromeda Galaxy's interstellar dust, was thought to be more massive than G1 and the largest cluster of the Local Group;JOURNAL, 2006, A 'super' star cluster grown old: the most massive star cluster in the Local Group, Monthly Notices of the Royal Astronomical Society, 1443–1450, 368, 2006MNRAS.368.1443Mfirst1=Junfirst2=Richardfirst3=Yanbin
, 3
first4=Xufirst5=Jianshengfirst6=Zhaojifirst7=Zhen-Yufirst8=Jianghua, 10.1111/j.1365-2966.2006.10231.x, 3, astro-ph/0602608, however, other studies have shown it is actually similar in properties to G1.COHEN>FIRST=JUDITH G., 2006, The Not So Extraordinary Globular Cluster 037-B327 in M31, The Astrophysical Journal, L21–L23, 653, 1, 2006ApJ...653L..21C, 10.1086/510384url =weblink (File:Star cluster in the Andromeda galaxy.jpg|thumb|Star clusters in the Andromeda Galaxy.WEB, Star cluster in the Andromeda galaxy,weblink 7 September 2015, )Unlike the globular clusters of the Milky Way, which show a relatively low age dispersion, Andromeda Galaxy's globular clusters have a much larger range of ages: from systems as old as the galaxy itself to much younger systems, with ages between a few hundred million years to five billion years.JOURNAL, 2004, Globular Cluster and Galaxy Formation: M31, the Milky Way, and Implications for Globular Cluster Systems of Spiral Galaxies, Astrophysical Journal, 158–166, 614, 1, 2004ApJ...614..158Bfirst1=Davidfirst2=Yongfirst3=Kenneth C.
, 3
first4=John E.first5=Michael S.first6=Jossfirst7=Brad K.first8=Michael A.first9=Hyun-chulfirst10=Beatrizfirst11=John P.first12=Jean P.first13=Duncan A., 10.1086/423334, astro-ph/0406564, In 2005, astronomers discovered a completely new type of star cluster in the Andromeda Galaxy. The new-found clusters contain hundreds of thousands of stars, a similar number of stars that can be found in globular clusters. What distinguishes them from the globular clusters is that they are much larger—several hundred light-years across—and hundreds of times less dense. The distances between the stars are, therefore, much greater within the newly discovered extended clusters.

Satellites

(File:M31 09-01-2011.jpg|Messier 32 is to the left of the center, Messier 110 is to the bottom-right of the center.|thumb|right|250px)Like the Milky Way, the Andromeda Galaxy has satellite galaxies, consisting of 14 known dwarf galaxies. The best known and most readily observed satellite galaxies are M32 and M110. Based on current evidence, it appears that M32 underwent a close encounter with the Andromeda Galaxy in the past. M32 may once have been a larger galaxy that had its stellar disk removed by M31, and underwent a sharp increase of star formation in the core region, which lasted until the relatively recent past.M110 also appears to be interacting with the Andromeda Galaxy, and astronomers have found in the halo of the latter a stream of metal-rich stars that appear to have been stripped from these satellite galaxies. M110 does contain a dusty lane, which may indicate recent or ongoing star formation. M32 have young population as well.JOURNAL
, Rudenko, Pavlo
, Intermediate age clusters in the field containing M31 and M32 stars
, The Astronomical Journal
, 138
, 6, 1985–1989, 2009
, 10.1088/0004-6256/138/6/1985
, Worthey, Guy
, Mateo, Mario
, 2009AJ....138.1985R
, In 2006, it was discovered that nine of the satellite galaxies lie in a plane that intersects the core of the Andromeda Galaxy; they are not randomly arranged as would be expected from independent interactions. This may indicate a common tidal origin for the satellites.

PA-99-N2 event and possible exoplanet in galaxy

PA-99-N2 was a microlensing event detected in the Andromeda Galaxy in 1999. One of the explanations for this is the gravitational lensing of a red giant with a mass between 0.02 and 3.6 masses of the Sun, which suggested that the star is likely a planet. This possible exoplanet would have mass of 6.34 times that of Jupiters mass. If finally confirmed, it would be the first ever found extragalactic planet. But, anomalies in the event were later found.weblink

Collision with the Milky Way

The Andromeda Galaxy is approaching the Milky Way at about {{convert|110|km/s|abbr=off}}. It has been measured approaching relative to the Sun at around {{convert|300|km/s|abbr=on}} as the Sun orbits around the center of the galaxy at a speed of approximately {{convert|225|km/s|abbr=on}}. This makes the Andromeda Galaxy one of about 100 observable blueshifted galaxies.WEB,weblink Apart from Andromeda, are any other galaxies moving towards us? - Space Facts – Astronomy, the Solar System & Outer Space - All About Space Magazine, 3 April 2016, Andromeda Galaxy's tangential or sideways velocity with respect to the Milky Way is relatively much smaller than the approaching velocity and therefore it is expected to collide directly with the Milky Way in about 4 billion years. A likely outcome of the collision is that the galaxies will merge to form a giant elliptical galaxy or perhaps even a large disc galaxy. Such events are frequent among the galaxies in galaxy groups. The fate of the Earth and the Solar System in the event of a collision is currently unknown. Before the galaxies merge, there is a small chance that the Solar System could be ejected from the Milky Way or join the Andromeda Galaxy.

Amateur observing

The Andromeda Galaxy is bright enough to be seen with the naked eye, even with some light pollution.WEB,weblink How to See the Farthest Thing You Can See - Sky & Telescope, 9 September 2015, Andromeda is best seen during autumn nights in the Northern Hemisphere, when from mid-latitudes the galaxy reaches zenith (its highest point at midnight) so can be seen almost all night. From the Southern Hemisphere, it is most visible at the same months, that is in spring, and away from our equator does not reach a high altitude over the northern horizon, making it difficult to observe. Binoculars can reveal some larger structures and its two brightest satellite galaxies, M32 and M110.WEB,weblink Watch Andromeda Blossom in Binoculars - Sky & Telescope, 16 September 2015, An amateur telescope can reveal Andromeda's disk, some of its brightest globular clusters, dark dust lanes and the large star cloud NGC 206.WEB,weblink Observing M31, the Andromeda Galaxy, WEB,weblink Globular Clusters in the Andromeda Galaxy,

See also

Notes

{{notes| notes ={{efn| name = avg dist| 1 = average(787 ± 18, 770 ± 40, 772 ± 44, 783 ± 25) = ((787 + 770 + 772 + 783) / 4) ± (182 + 402 + 442 + 252)0.5 / 2 = 778 ± 33.}}{{efn| name = M31VJCelestial coordinate system>celestial coordinates Right Ascension {{RA>0037.99}}, Declination {{DEC>+4123.6}}.}}{{efn| name = blue mag| 1 = Blue absolute magnitude of −20.89 – Color index of 0.63 = −21.52}}{{efn| name = bright m31| 1 = Blue absolute magnitude of −21.58 (see reference) – Color index of 0.63 = absolute visual magnitude of −22.21}}}}{{clear}}

References

{{Reflist| 30em| refs =WEB, Results for Messier 31,weblink NASA/IPAC Extragalactic DatabaseNASA/Infrared Processing and Analysis Center>IPAC, 28 February 2019, COWEN > FIRST1 = RON, 2012, Andromeda on collision course with the Milky Way,weblinkNature (journal)>Nature, 6 October 2014, 10.1038/nature.2012.10765, KARACHENTSEV > FIRST1 = IGOR D. FIRST2 = OLGA G., 2006, Masses of the Local Group and of the M81 group estimated from distortions in the local velocity fieldAstrophysics (journal)>Astrophysics, 49, 1, 3–18, 2006Ap.....49....3K, 10.1007/s10511-006-0002-6, MAGAZINE, Young, Kelly, 6 June 2006, The Andromeda Galaxy hosts a trillion stars,weblink New Scientist, 6 October 2014, KARACHENTSEV > FIRST1 = IGOR D. FIRST2 = VALENTINA E. FIRST3 = WALTER K. FIRST4 = DMITRY I., 2004, A Catalog of Neighboring Galaxies, Astronomical Journal, 127, 4, 2031–2068, 2004AJ....127.2031K, 10.1086/382905, JOURNAL, Ribas, Ignasi, Jordi, Carme, Vilardell, Francesc
, 3, Fitzpatrick, Edward L., Hilditch, Ron W., Guinan, Edward F., 2005, First Determination of the Distance and Fundamental Properties of an Eclipsing Binary in the Andromeda Galaxy, Astrophysical Journal Letters, 635, 1, L37–L40, 2005ApJ...635L..37R, astro-ph/0511045, 10.1086/499161
, JOURNAL, McConnachie, Alan W., Irwin, Michael J., Ferguson, Annette M. N.
, 3, Ibata, Rodrigo A., Lewis, Geraint F., Tanvir, Nial R., 2005, Distances and metallicities for 17 Local Group galaxies, Monthly Notices of the Royal Astronomical Society, 356, 4, 979–997, 2005MNRAS.356..979M, astro-ph/0410489, 10.1111/j.1365-2966.2004.08514.x
, JENSEN > FIRST1 = JOSEPH B. FIRST2 = JOHN L. FIRST3 = BRIAN J.
, 3
first4 = Rodger I. first5 = Michael C. first6 = Marcia J. first7 = Edward A. first8 = John P., 2003, Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations, Astrophysical Journal, 583, 2, 712–726, astro-ph/0210129, 2003ApJ...583..712J, 10.1086/345430, WEB, M 31,weblink 30 September 2018, JOURNAL, 2007, The GALEX Ultraviolet Atlas of Nearby Galaxies, Astrophysical Journal, 173, 2, 185–255, astro-ph/0606440, 2007ApJS..173..185G, 10.1086/516636 first1 = Armando first2 = Samuel first3 = Barry F.
, 3
first4 = Mark first5 = Young H. first6 = Alessandro first7 = Ted K.first8=David A.first9=Luciana, Rey, Soo‐Chang, Rich, Robert Michael, Barlow, Tom A., Conrow, Tim, Forster, Karl, Friedman, Peter G., Martin, D. Christopher, Morrissey, Patrick, Neff, Susan G., Schiminovich, David, Small, Todd, Donas, Jose, Heckman, Timothy M., Lee, Young‐Wook, Milliard, Bruno, Szalay, Alex S., Yi, Sukyoung, WEB, NASA's Hubble Shows Milky Way is Destined for Head-On Collision, NASA, 31 May 2012,weblink 12 July 2012,weblink" title="web.archive.org/web/20140604191905weblink">weblink 4 June 2014, WEB
, Frommert
, Hartmut
, Kronberg
, Christine
, 22 August 2007
, Messier Object Data, sorted by Apparent Visual Magnitude
,weblink
, SEDS
, 27 August 2007
,weblink" title="web.archive.org/web/20070712184703weblink">weblink
, 12 July 2007
, dead
, BOOK, Kepple, George Robert, Sanner, Glen W., 1998, The Night Sky Observer's Guide, Vol. 1, 18, Willmann-Bell, 978-0-943396-58-3, BOOK, Davidson, Norman, 1985, Astronomy and the imagination: a new approach to man's experience of the stars, 203, Routledge Kegan & Paul, 978-0-7102-0371-7, JOURNAL, Herschel, William, William Herschel, 1785, On the Construction of the Heavens, Philosophical Transactions of the Royal Society of London, 75, 213–266, 10.1098/rstl.1785.0012, JOURNAL, Huggins, William, William Huggins, 1864, On the Spectra of Some of the Nebulae, Philosophical Transactions of the Royal Society of London, 154, 437–444, 10.1098/rstl.1864.0013, 1864RSPT..154..437H, JOURNAL, Backhouse, Thomas W., 1888, Nebula in Andromeda and Nova, 1885, Monthly Notices of the Royal Astronomical Society, 48, 3, 108–110, 1888MNRAS..48..108B, 10.1093/mnras/48.3.108, JOURNAL, Slipher, Vesto M., Vesto Slipher, 1913, The Radial Velocity of the Andromeda Nebula, Lowell Observatory Bulletin, 1, 56–57, 1913LowOB...2...56S, JOURNAL, Curtis, Heber Doust, Heber Doust Curtis, 1988, Novae in Spiral Nebulae and the Island Universe Theory, Publications of the Astronomical Society of the Pacific, 100, 6, 1988PASP..100....6C, 10.1086/132128, JOURNAL, Öpik, Ernst, Ernst Öpik, 1922, An estimate of the distance of the Andromeda Nebula, Astrophysical Journal, 55, 406–410, 1922ApJ....55..406O, 10.1086/142680, JOURNAL, Hubble, Edwin P., Edwin Hubble, 1929, A spiral nebula as a stellar system, Messier 31, Astrophysical Journal, 69, 103–158, 1929ApJ....69..103H, 10.1086/143167, JOURNAL, Baade, Walter, Walter Baade, 1944, The Resolution of Messier 32, NGC 205, and the Central Region of the Andromeda Nebula, Astrophysical Journal, 100, 137, 1944ApJ...100..137B, 10.1086/144650, BOOK, Gribbin, John R., 2001, The Birth of Time: How Astronomers Measure the Age of the Universe, 151, Yale University Press, 978-0-300-08914-1, JOURNAL, Brown, Robert Hanbury, Hazard, Cyril, 1950, Radio-frequency Radiation from the Great Nebula in Andromeda (M.31)Nature (journal)>Nature, 166, 901–902, 1950Natur.166..901B, 10.1038/166901a0, 4230, JOURNAL, Brown, Robert Hanbury, Hazard, Cyril, 1951, Radio emission from the Andromeda nebula, MNRAS, 111, 4, 357–367, 1951MNRAS.111..357B, 10.1093/mnras/111.4.357, JOURNAL, van der Kruit, Piet C., Allen, Ronald J., 1976, The Radio Continuum Morphology of Spiral Galaxies, Annual Review of Astronomy and Astrophysics, 14, 1, 417–445, 10.1146/annurev.aa.14.090176.002221, 1976ARA&A..14..417V, JOURNAL, Ingrosso, Gabriele, Calchi Novati, Sebastiano, De Paolis, Francesco
, 3, Jetzer, Philippe, Nucita, Achille A., Zakharov, Alexander F., 2009, Pixel-lensing as a way to detect extrasolar planets in M31, Monthly Notices of the Royal Astronomical Society, 399, 1, 219–228, 0906.1050, 10.1111/j.1365-2966.2009.15184.x, 2009MNRAS.399..219I
, JOURNAL, Holland, Stephen, 1998, The Distance to the M31 Globular Cluster System, Astronomical Journal, 115, 5, 1916–1920, 1998AJ....115.1916H, 10.1086/300348, astro-ph/9802088, JOURNAL, Stanek, Krzysztof Z., Garnavich, Peter M., 1998, Distance to M31 With the HST and Hipparcos Red Clump Stars, Astrophysical Journal Letters, 503, 2, 131–141, astro-ph/9802121, 10.1086/311539, 1998ApJ...503L.131S, JOURNAL, Kalirai, Jasonjot Singh, Gilbert, Karoline M., Guhathakurta, Puragra
, 3, Majewski, Steven R., Ostheimer, James C., Rich, Robert Michael, Cooper, Michael C., Reitzel, David B., Patterson, Richard J., 2006, The Metal-Poor Halo of the Andromeda Spiral Galaxy (M31), Astrophysical Journal, 648, 1, 389–404, astro-ph/0605170, 2006ApJ...648..389K, 10.1086/505697
, VAN DEN BERGH >FIRST1=SIDNEY, 1999, The local group of galaxies, Astronomy and Astrophysics Review, 9, 3–4, 273–318, 1999A&ARv...9..273V, 10.1007/s001590050019, JOURNAL, Liller, William, Mayer, Ben, 1987, The Rate of Nova Production in the Galaxy, Publications of the Astronomical Society of the Pacific, 99, 606–609, 1987PASP...99..606L, 10.1086/132021, BEATON > FIRST = RACHAEL L. FIRST2 = STEVEN R. FIRST3 = PURAGRA
, 3
first4 = Michael F. first5 = Roc M. first6 = John first7 = Richard J. first8=Évangélie first9 = Martin, 2006, Unveiling the Boxy Bulge and Bar of the Andromeda Spiral Galaxy, Astrophysical Journal Letters, 658, 2, L91, 2007ApJ...658L..91B, 10.1086/514333, astro-ph/0605239, JOURNAL, Chapman, Scott C., Ibata, Rodrigo A., Lewis, Geraint F.
, 3, Ferguson, Annette M. N., Irwin, Michael J., McConnachie, Alan W., Tanvir, Nial R., 2006, A kinematically selected, metal-poor spheroid in the outskirts of M31, Astrophysical Journal, 653, 1, 255–266, astro-ph/0602604, 10.1086/508599, 2006ApJ...653..255C
, Also see the press release,CALTECH>CALTECH MEDIA RELATIONS, 27 February 2006, Andromeda's Stellar Halo Shows Galaxy's Origin to Be Similar to That of Milky Way,weblink 24 May 2006,weblink" title="web.archive.org/web/20060509072644weblink">weblink 9 May 2006, dead, dmy-all, PRESS RELEASE
, UC Santa Cruz
, 9 January 2001
, Astronomers Find Evidence of an Extreme Warp in the Stellar Disk of the Andromeda Galaxy
,weblink
, 24 May 2006
,weblink" title="web.archive.org/web/20060519081929weblink">weblink
, 19 May 2006
, dead
, JOURNAL, Rubin, Vera C., Ford, W. Kent Jr., 1970, Rotation of the Andromeda Nebula from a Spectroscopic Survey of Emission, Astrophysical Journal, 159, 379, 1970ApJ...159..379R, 10.1086/150317, JOURNAL, Arp, Halton, Halton Arp, 1964, Spiral Structure in M31, Astrophysical Journal, 139, 1045, 1964ApJ...139.1045A, 10.1086/147844, BRAUN > FIRST = ROBERT, 1991, The distribution and kinematics of neutral gas, HI region in M31, Astrophysical Journal, 372, 54–66, 1991ApJ...372...54B, 10.1086/169954, HI region, PRESS RELEASE, European Space Agency, 14 October 1998, ISO unveils the hidden rings of Andromeda,weblink 24 May 2006, DAVID A. >LAST=AGUILARLAST2=PULLIAM, 18 October 2006, Busted! Astronomers Nab Culprit in Galactic Hit-and-Run, Harvard-Smithsonian Center for Astrophysics,weblink 6 October 2014,weblink" title="web.archive.org/web/20141008143627weblink">weblink 8 October 2014, live, JOURNAL, Bullock, James S., Johnston, Kathryn V., 2005, Tracing Galaxy Formation with Stellar Halos I: Methods, Astrophysical Journal, 635, 2, 931–949, astro-ph/0506467, 2005ApJ...635..931B, 10.1086/497422, JOURNAL, Lauer, Tod R., Faber, Sandra M., Groth, Edward J.
, 3, Shaya, Edward J., Campbell, Bel, Code, Arthur, Currie, Douglas G., Baum, William A., Ewald, Shawn P.
first10=J. Jefffirst11=Jon A.first12=Jeromefirst13=Robert M.first14=C. Rogerfirst15=Earl J. Jr., 1993, Planetary camera observations of the double nucleus of M31, Astronomical Journal, 106, 4, 1436–1447, 1710–1712, 1993AJ....106.1436L, 10.1086/116737,weblink JOURNAL, Bender, Ralf, Kormendy, John, Bower, Gary
, 3, Green, Richard, Thomas, Jens, Danks, Anthony C., Gull, Theodore, Hutchings, J. B., Joseph, C. L., 2005, HST STIS Spectroscopy of the Triple Nucleus of M31: Two Nested Disks in Keplerian Rotation around a Supermassive Black Hole, Astrophysical Journal, 631, 1, 280–300, 2005ApJ...631..280B, astro-ph/0509839, 10.1086/432434, Kaiser, M. E., Lauer, Tod R., Nelson, Charles H., Richstone, Douglas, Weistrop, Donna, Woodgate, Bruce
, JOURNAL, Gebhardt, Karl, Bender, Ralf, Bower, Gary
, 3, Dressler, Alan, Faber, S. M., Filippenko, Alexei V., Green, Richard, Grillmair, Carl, Ho, Luis C., June 2000, A Relationship between Nuclear Black Hole Mass and Galaxy Velocity Dispersion, The Astrophysical Journal, 539, 1, L13–L16,weblink 10 March 2010, astro-ph/0006289, 2000ApJ...539L..13G, 10.1086/312840, Kormendy, John, Lauer, Tod R., Magorrian, John, Pinkney, Jason, Richstone, Douglas, Tremaine, Scott
, TREMAINE > FIRST = SCOTT, 1995, An Eccentric-Disk Model for the Nucleus of M31, Astronomical Journal, 110, 628–633, astro-ph/9502065, 1995AJ....110..628T, 10.1086/117548, PRESS RELEASE, 20 July 1993, Hubble Space Telescope Finds a Double Nucleus in the Andromeda Galaxy,weblink Hubble News Desk, 26 May 2006, NEWS
, Schewe, Phillip F.
, Stein, Ben
, 26 July 1993
, The Andromeda Galaxy has a Double Nucleus
, Physics News Update
, American Institute of Physics
,weblink
, 10 July 2009
, dead
,weblink" title="web.archive.org/web/20090815062838weblink">weblink
, 15 August 2009
, FUJIMOTO > FIRST1 = MITSUAKI FIRST2 = SATIO FIRST3 = TAKAKO, 1969, Correlation between the Densities of X-Ray Sources and Interstellar Gas, Astrophysics and Space Science, 4, 1, 64–83, 1969Ap&SS...4...64F, 10.1007/BF00651263, PETERSON > FIRST = LAURENCE E., 1973, Hard Cosmic X-Ray Sourceseditor2=Giacconi, Riccardo, X- and Gamma-Ray Astronomy, Proceedings of IAU Symposium no. 55 held in Madrid, Spain, 11–13 May 1972, X- and Gamma-Ray Astronomy, 55, 51–73, International Astronomical Union, 1973IAUS...55...51P, MARELLI > FIRST=MARTINO FIRST2=ANDREA FIRST3=ANDREA
, 3
first4=David first5=Luca first6=Lara first7=Adamantia first8=Ruben first9=Andrea first10=Gianluca first11=Frank first12=Daniele, 2017, Discovery of periodic dips in the brightest hard X-ray source of M31 with EXTraS, The Astrophysical Journal Letters, 851, 2, L27, 2017ApJ...851L..27M, 10.3847/2041-8213/aa9b2e, 1711.05540, BARNARD > FIRST = ROBIN FIRST2 = ULRICH C. FIRST3 = JULIAN P., 2005, Timing the bright X-ray population of the core of M31 with XMM-Newton, astro-ph/0508284, JOURNAL
, Barmby, Pauline
, Huchra, John P., 2001, M31 Globular Clusters in the Hubble Space Telescope Archive. I. Cluster Detection and Completeness, Astronomical Journal, 122, 5, 2458–2468, 10.1086/323457, 2001AJ....122.2458B, astro-ph/0107401
, PRESS RELEASE, Hubble news desk STSci-1996-11, 24 April 1996, Hubble Spies Globular Cluster in Neighboring Galaxy,weblink 26 May 2006,weblink" title="web.archive.org/web/20060701083419weblink">weblink 1 July 2006, live, JOURNAL, Meylan, Georges, Sarajedini, Ata, Jablonka, Pascale
, 3, Djorgovski, S. George, Bridges, Terry, Rich, Robert Michael, 2001, G1 in M31 â€“ Giant Globular Cluster or Core of a Dwarf Elliptical Galaxy?, Astronomical Journal, 122, 2, 830–841, 10.1086/321166, 2001AJ....122..830M, astro-ph/0105013
, JOURNAL, Huxor, Avon P., Tanvir, Nial R., Irwin, Michael J.
, 3, Ibata, Rodrigo A., Collett, James L., Ferguson, Annette M. N., Bridges, Terry, Lewis, Geraint F., 2005, A new population of extended, luminous, star clusters in the halo of M31, Monthly Notices of the Royal Astronomical Society, 360, 3, 993–1006, astro-ph/0412223, 2005MNRAS.360.1007H, 10.1111/j.1365-2966.2005.09086.x
, JOURNAL, Bekki, Kenji, Couch, Warrick J., Drinkwater, Michael J.
, 3, Gregg, Michael D., 2001, A New Formation Model for M32: A Threshed Early-type Spiral?, Astrophysical Journal Letters, 557, 1, L39–L42, 2001ApJ...557L..39B, astro-ph/0107117, 10.1086/323075
, JOURNAL, Ibata, Rodrigo A., Irwin, Michael J., Lewis, Geraint F.
, 3, Ferguson, Annette M. N., Tanvir, Nial R., 2001, A giant stream of metal-rich stars in the halo of the galaxy M31
Nature (journal)>Nature, 412, 6842, 49–52, 10.1038/35083506, 11452300, astro-ph/0107090, 2001Natur.412...49I, JOURNAL, Young, Lisa M., 2000, Properties of the Molecular Clouds in NGC 205, Astronomical Journal, 120, 5, 2460–2470, 10.1086/316806, 2000AJ....120.2460Y, astro-ph/0007169, JOURNAL
, Koch
, Andreas
, Grebel
, Eva K.
, March 2006, The Anisotropic Distribution of M31 Satellite Galaxies: A Polar Great Plane of Early-type Companions
, Astronomical Journal
, 131
, 3
, 1405–1415
, astro-ph/0509258
, 2006AJ....131.1405K
, 10.1086/499534,
JOURNAL, Cox, Thomas J., Loeb, Abraham, 2008, The collision between the Milky Way and Andromeda, Monthly Notices of the Royal Astronomical Society, 386, 1, 461–474, 2008MNRAS.386..461C, 10.1111/j.1365-2966.2008.13048.x, 0705.1170, WEB, Cain, Fraser, 2007, When Our Galaxy Smashes Into Andromeda, What Happens to the Sun?, Universe Today,weblink 16 May 2007,weblink" title="web.archive.org/web/20070517021426weblink">weblink 17 May 2007, live, }}

External links

{{Commons}}

, Than
, Ker
, 23 January 2006
, Strange Setup: Andromeda's Satellite Galaxies All Lined Up
, Space.com
,weblink
,
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