Triangulum Galaxy

Coordinates: Sky map 01h 33m 50.9s, 30° 39′ 36″

Triangulum Galaxy
M33 - Triangulum Galaxy
Triangulum Galaxy – Messier 33
Observation data (J2000 epoch)
Right ascension 01h 33m 50.02s[1]
Declination+30° 39′ 36.7″[1]
Redshift-0.000607 ± 0.000010[1]
Helio radial velocity-179 ± 3 km/s[2]
Galactocentric velocity-44 ± 6 km/s[2]
Distance2.38 to 3.07 Mly (730 to 940 kpc)[3][4]
Apparent magnitude (V)5.72[1]
Mass5 × 1010[5] M
Number of stars40 billion (4×1010)[6]
Size~60,000 ly (diameter)[6]
Apparent size (V)70.8 × 41.7 moa[1]
Other designations
NGC 0598, MCG+05-04-069, UGC 1117, PGC 5818[2]

The Triangulum Galaxy is a spiral galaxy approximately 3 million light-years (ly) from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC 598. The Triangulum Galaxy is the third-largest member of the Local Group of galaxies, behind the Milky Way and the Andromeda Galaxy. It is one of the most distant permanent objects that can be viewed with the naked eye.

The galaxy is the smallest spiral galaxy in the Local Group and it is believed to be a satellite of the Andromeda Galaxy due to their interactions, velocities,[7] and proximity to one another in the night sky. It also has an H II nucleus.[8]


The galaxy gets its name from the constellation Triangulum, where it can be spotted.

The Triangulum Galaxy is sometimes informally referred to as the "Pinwheel Galaxy" by some amateur astronomy references[9] and in some public outreach websites.[10] However, the SIMBAD Astronomical Database, a professional astronomy database that contains formal designations for astronomical objects, indicates that the name Pinwheel Galaxy is used to refer to Messier 101,[11] and several other amateur astronomy resources and other public outreach websites also identify Messier 101 by that name.[12][13]


Under exceptionally good viewing conditions with no light pollution, the Triangulum Galaxy can be seen with the naked eye.[14] It is one of the most distant permanent objects that can be viewed without the aid of a telescope.[15][16] Being a diffuse object, its visibility is strongly affected by just small amounts of light pollution. It ranges from easily visible by direct vision in dark skies to a difficult averted vision object in rural or suburban skies.[14] For this reason, Triangulum is one of the critical sky marks of the Bortle Dark-Sky Scale.[17]

Triangulum Galaxy (Messier 33)
Triangulum Galaxy (Messier 33), taken with amateur equipment.

Observation history

The Triangulum Galaxy was probably discovered by the Italian astronomer Giovanni Battista Hodierna before 1654. In his work De systemate orbis cometici; deque admirandis coeli caracteribus ("About the systematics of the cometary orbit, and about the admirable objects of the sky"), he listed it as a cloud-like nebulosity or obscuration and gave the cryptic description, "near the Triangle hinc inde". This is in reference to the constellation of Triangulum as a pair of triangles. The magnitude of the object matches M33, so it is most likely a reference to the Triangulum galaxy.[18]

The galaxy was independently discovered by Charles Messier on the night of August 25–26, 1764. It was published in his Catalog of Nebulae and Star Clusters (1771) as object number 33; hence the name M33. When William Herschel compiled his extensive catalogue of nebulae, he was careful not to include most of the objects identified by Messier.[19] However, M33 was an exception and he catalogued this object on September 11, 1784, as H V-17.[20]

Herschel also catalogued the Triangulum Galaxy's brightest and largest H II region (diffuse emission nebula containing ionized hydrogen) as H III.150 separately from the galaxy itself; the nebula eventually obtained NGC number 604. As seen from Earth, NGC 604 is located northeast of the galaxy's central core. It is one of the largest H II regions known, with a diameter of nearly 1500 light-years and a spectrum similar to that of the Orion Nebula. Herschel also noted three other smaller H II regions (NGC 588, 592, and 595).

It was among the first "spiral nebulae" identified as such by Lord Rosse in 1850. In 1922–23, John Charles Duncan and Max Wolf discovered variable stars in the nebulae. Edwin Hubble showed in 1926 that 35 of these stars were classical Cepheids, thereby allowing him to estimate their distances. The results were consistent with the concept of spiral nebulae being independent galactic systems of gas and dust, rather than just nebulae in the Milky Way.[21]

Nursery of New Stars - GPN-2000-000972

NGC 604 in the Triangulum Galaxy

The sharpest view ever of the Triangulum Galaxy Messier 33

Composite of about 54 different pointings with Hubble's Advanced Camera for Surveys.[22]


VST snaps a very detailed view of the Triangulum Galaxy
Triangulum Galaxy taken by VLT Survey Telescope.[23]

With a diameter of about 60,000 light-years, the Triangulum galaxy is the third largest member of the Local Group of galaxies, roughly 60% the size of the Milky Way. It may be a gravitationally bound companion of the Andromeda Galaxy. Triangulum may be home to 40 billion stars, compared to 400 billion for the Milky Way, and 1 trillion stars for Andromeda Galaxy.[6]

The disk of Triangulum has an estimated mass of (3–6) × 109 solar masses, while the gas component is about 3.2 × 109 solar masses. Thus the combined mass of all baryonic matter in the galaxy may be 1010 solar masses. The contribution of the dark matter component out to a radius of 55×103 ly (17 kpc) is equivalent to about 5 × 1010 solar masses.[5]


Andromeda constellation map (1)
Triangulum (M33; lower left of center) and Andromeda Galaxy (M31; above center)

Estimates of the distance to the Triangulum galaxy range from 2,380×103 to 3,070×103 ly (730 to 940 kpc) (or 2.38 to 3.07 Mly), with most estimates since the year 2000 lying in the middle portion of this range,[3][4] making it slightly more distant than the Andromeda Galaxy (at 2,540,000 light-years). At least three techniques have been used to measure distances to M 33. Using the Cepheid variable method, an estimate of 2,770×103 ± 130×103 ly (849 ± 40 kpc) was achieved in 2004.[24][25] In the same year, the tip of the red-giant branch (TRGB) method was used to derive a distance estimate of 2,590×103 ± 80×103 ly (794 ± 25 kpc).[26]

In 2006, a group of astronomers announced the discovery of an eclipsing binary star in the Triangulum Galaxy. 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 the absolute magnitude of the stars. When the visual and absolute magnitudes are known, the distance to the star can be measured. The stars lie at the distance of 3,070×103 ± 240×103 ly (941 ± 74 kpc).[3] The average of 102 distance estimates published since 1987 gives a distance modulus of 24.69, or .883 Mpc (2,878,000 light-years).[27]

The Triangulum galaxy is a source of H2O maser emission.[28] In 2005, using observations of two water masers on opposite sides of Triangulum via the VLBA, researchers were, for the first time, able to estimate the angular rotation and proper motion of Triangulum. A velocity of 190 ± 60 km/s relative to the Milky Way was computed, which means Triangulum is moving towards Andromeda Galaxy and suggesting it may be a satellite of the larger galaxy (depending on their relative distances and margins of error).[7] In 2004, evidence was announced of a clumpy stream of hydrogen gas linking the Andromeda Galaxy with Triangulum, suggesting that the two may have tidally interacted in the past. This discovery was confirmed in 2011.[29] A distance of less than 300 kiloparsecs between the two supports this hypothesis.[30]

The Pisces Dwarf (LGS 3), one of the small Local Group member galaxies, is located 2,022×103 ly (620 kpc) from the Sun. It is 20° from the Andromeda Galaxy and 11° from Triangulum. As LGS 3 lies at a distance of 913×103 ly (280 kpc) from both galaxies, it could be a satellite galaxy of either Andromeda or Triangulum. LGS 3 has a core radius of 483 ly (148 pc) and 2.6 × 107 solar masses.[31]


Spitzer m33
Infrared image of M33 taken with the Spitzer Space Telescope
Ultraviolet image of M33 by GALEX observatory

In the French astronomer Gérard de Vaucouleurs' revised Hubble Sandage (VRHS) system of galaxy morphological classification, the Triangulum galaxy is classified as type SA(s)cd. The S prefix indicates that it is a disk-shaped galaxy with prominent arms of gas and dust that spiral out from the nucleus—what is commonly known as a spiral galaxy. The A is assigned when the galactic nucleus lacks a bar-shaped structure, in contrast to SB class barred spiral galaxies. American astronomer Allan Sandage's "(s)" notation is used when the spiral arms emerge directly from the nucleus or central bar, rather than from an inner ring as with an (r)-type galaxy. Finally, the cd suffix represents a stage along the spiral sequence that describes the openness of the arms. A rating of cd indicates relatively loosely wound arms.[32]

This galaxy has an inclination of 54° to the line of sight from the Earth, allowing the structure to be examined without significant obstruction by gas and dust.[33][34] The disk of the Triangulum galaxy appears warped out to a radius of about 8 kpc. There may be a halo surrounding the galaxy, but there is no bulge at the nucleus.[35] This is an isolated galaxy and there are no indications of recent mergers or interactions with other galaxies,[34] and it lacks the dwarf spheroidals or tidal tails associated with the Milky Way.[36]

Triangulum is classified as unbarred, but an analysis of the galaxy shape shows what may be a weak bar-like structure about the galactic nucleus. The radial extent of this structure is about 0.8 kpc.[37] The nucleus of this galaxy is an H II region,[28] and it contains an ultraluminous X-ray source with an emission of 1.2 × 1039 erg s−1, which is the most luminous source of X-rays in the Local Group of galaxies. This source is modulated by 20% over a 106-day cycle.[38] However, the nucleus does not appear to contain a supermassive black hole, as an upper limit of 3,000 solar masses is placed on the mass of a central black hole based upon the velocity of stars in the core region.[39]

The inner part of the galaxy has two luminous spiral arms, along with multiple spurs that connect the inner to the outer spiral features.[33][34] The main arms are designated IN (north) and IS (south).[40]

Star formation

NGC 604, a star-forming region in the Triangulum Galaxy, as imaged by the Hubble Space Telescope.

In the central 4′ region of this galaxy, atomic gas is being efficiently converted to molecular gas, resulting in a strong spectral emission of CO. This effect occurs as giant molecular clouds condense out of the surrounding interstellar medium. A similar process is taking place outside the central 4′, but at a less efficient pace. About 10% of the gas content in this galaxy is in the molecular form.[33][34]

Star formation is taking place at a rate that is strongly correlated with the local gas density, and the rate per unit area is higher than in the neighboring Andromeda Galaxy. (The rate of star formation is about 3.4 Gyr−1 pc−2 in the Triangulum galaxy, compared to 0.74 in Andromeda.[41]) The total integrated rate of star formation in the Triangulum galaxy is about 0.45 ± 0.1 solar masses per year. It is uncertain whether this net rate is currently decreasing or remaining constant.[33][34]

Based on analysis of the chemical composition of this galaxy, it appears to be divided into two distinct components with differing histories. The inner disk within a radius of 30×103 ly (9 kpc) has a typical composition gradient that decreases linearly from the core. Beyond this radius, out to about 82×103 ly (25 kpc), the gradient is much flatter. This suggests a different star formation history between the inner disk and the outer disk and halo, and may be explained by a scenario of "inside-out" galaxy formation.[35] This occurs when gas is accumulated at large radii later in a galaxy's life space, while the gas at the core becomes exhausted. The result is a decrease in the average age of stars with increasing radius from the galaxy core.[42]

Discrete features

Using infrared observations from the Spitzer Space Telescope, a total of 515 discrete candidate sources of 24 μm emission within the Triangulum galaxy have been catalogued as of 2007. The brightest sources lie within the central region of the galaxy and along the spiral arms.

Many of the emission sources are associated with H II regions of star formation.[43] The four brightest HII regions are designated NGC 588, NGC 592, NGC 595, and NGC 604. These regions are associated with molecular clouds containing (1.2–4) × 105 solar masses. The brightest of these regions, NGC 604, may have undergone a discrete outburst of star formation about three million years ago.[44] This nebula is the second most luminous HII region within the Local Group of galaxies, at (4.5 ± 1.5) × 107 times the luminosity of the Sun.[41] Other prominent HII regions in Triangulum include IC 132, IC 133, and IK 53.[40]

The northern main spiral arm contains four large HII regions, while the southern arm has greater concentrations of young, hot stars.[40] The estimated rate of supernova explosions in the Triangulum Galaxy is 0.06 Type Ia and 0.62 Type Ib/Type II per century. This is equivalent to a supernova explosion every 147 years, on average.[45] As of 2008, a total of 100 supernova remnants have been identified in the Triangulum Galaxy,[46] the majority of which lies in the southern half of the spiral galaxy. Similar asymmetries exist for H I and H II regions, plus highly luminous concentrations of massive, O type stars. The center of the distribution of these features is offset about two arc minutes to the southwest.[40] M33 being a local galaxy, the Central Bureau for Astronomical Telegrams (CBAT) tracks novae in it along with M31 and M81.[47]

About 54 globular clusters have been identified in this galaxy, but the actual number may be 122 or more.[36] The confirmed clusters may be several billion years younger than globular clusters in the Milky Way, and cluster formation appears to have increased during the past 100 million years. This increase is correlated with an inflow of gas into the center of the galaxy. The ultraviolet emission of massive stars in this galaxy matches the level of similar stars in the Large Magellanic Cloud.[48]

In 2007, a black hole about 15.7 times the mass of the Sun was detected in this galaxy using data from the Chandra X-ray Observatory. The black hole, named M33 X-7, orbits a companion star which it eclipses every 3.5 days. It is the largest stellar mass black hole known.[49][50]

Relationship with the Andromeda Galaxy

Collision paths of our Milky Way galaxy and the Andromeda galaxy
Triangulum on the collision paths of Milky Way and the Andromeda Galaxy.

As mentioned above, M33 is linked to M31 by several streams of neutral hydrogen[51] and stars,[51] which suggests that a past interaction between these two galaxies took place from 2 to 8 billion years ago,[52][53] and a more violent encounter will occur 2.5 billion years in the future.[51]

However, astrometric data from Gaia now appears to rule out the possibility that the Triangulum Galaxy is in a long-period orbit around the Andromeda Galaxy. Rather, it is on its first infall into the Andromeda Galaxy.[54]

The fate of the Triangulum Galaxy is unclear, but seems to be linked to its larger neighbor the Andromeda Galaxy. Suggested future scenarios for M33 include being torn apart and absorbed by the greater companion, fueling the latter with hydrogen to form new stars; eventually exhausting all of its gas, and thus the ability to form new stars;[55] or participating in the collision between the Milky Way and M31, most likely ending up orbiting the merger product of the latter two galaxies and fusing with it much later. Two other possibilities are a collision with the Milky Way before the Andromeda Galaxy arrives or an ejection out of the Local Group.[56]

See also


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  56. ^ van der Marel, Roeland P.; et al. (July 2012). "The M31 Velocity Vector. III. Future Milky Way-M31-M33 Orbital Evolution, Merging, and Fate of the Sun". The Astrophysical Journal. 753 (1): 9. arXiv:1205.6865. Bibcode:2012ApJ...753....9V. doi:10.1088/0004-637X/753/1/9.

Further reading

External links

Andromeda II

Andromeda II (And II) is a dwarf spheroidal galaxy about 2.22 Mly away in the constellation Andromeda. While part of the Local Group, it is not quite clear if it is a satellite of the Andromeda Galaxy or the Triangulum Galaxy.It was discovered by Sidney Van den Bergh in a survey of photographic plates taken with the Palomar 48-inch (1.2 m) Schmidt telescope in 1970 and 1971, together with Andromeda I, Andromeda III, and the presumable non- or background galaxy Andromeda IV.

Dwingeloo 1

Dwingeloo 1 is a barred spiral galaxy about 10 million light-years away from the Earth, in the constellation Cassiopeia. It lies in the Zone of Avoidance and is heavily obscured by the Milky Way. The size and mass of Dwingeloo 1 are comparable to those of Triangulum Galaxy.

Dwingeloo 1 has two smaller satellite galaxies — Dwingeloo 2 and MB 3 — and is a member of the IC 342/Maffei Group of galaxies.

Galaxies in fiction

Galaxies other than the Milky Way are popular settings for creators of science fiction, particularly those working with broad-scale space opera settings. Among the most common settings are the Andromeda Galaxy, the Magellanic Clouds, and the Triangulum Galaxy, all part of the Local Group close to the Milky Way, and in the cases of Andromeda and Triangulum the Local Group's two largest other galaxies. The difficulties involved in crossing the immense distances between galaxies are often overlooked in this type of science fiction.

IC 342

IC 342 (also known as Caldwell 5) is an intermediate spiral galaxy in the constellation Camelopardalis, located relatively close to the Milky Way. Despite its size and actual brightness, its location in dusty areas near the galactic equator makes it difficult to observe, leading to the nickname "The Hidden Galaxy", though it can readily be detected even with binoculars. The dust makes it difficult to determine its precise distance; modern estimates range from about 7 Mly to about 11 Mly.The galaxy was discovered by William Frederick Denning in 1892. It is one of the brightest in the IC 342/Maffei Group, one of the closest galaxy groups to the Local Group. Edwin Hubble first thought it to be in the Local Group, but it was later determined not to be a member.In 1935, Harlow Shapley found that it was wider than the full moon, and by angular size the third-largest spiral galaxy then known, smaller only than the Andromeda Galaxy (M31) and the Triangulum Galaxy (M33). (Modern estimates are more conservative, giving the apparent size as one-half to two-thirds the diameter of the full moon).It has an H II nucleus.

List of Triangulum's suspected satellite galaxies

The Triangulum subgroup is made up of the Triangulum Galaxy (M33) and its satellites. Although the Triangulum Galaxy does not have any proven satellite galaxies, a number of galaxies are suspected of being in the system.

List of novae in 2018

The following is a list of all novae that are known to have occurred in 2018. A nova is an energetic astronomical event caused by a white dwarf accreting matter from a star it is orbiting (typically a red giant, whose outer layers are more weakly attached than smaller, denser stars) Alternatively, novae can rarely be caused by a pair of stars merging with each other, however such events are vastly less common than novae caused by white dwarves.

In 2018, 15 novae were discovered in the Milky Way, 14 being classical novae, and 1 being a dwarf nova of a previously known variable star, V392 Persei, which was discovered in 1972. An additional 23 novae were discovered in the Andromeda Galaxy, 8 in Messier 81, 1 in the Triangulum Galaxy, and 1 in Messier 83. A single luminous red nova was observed in NGC 45.

List of stars in Triangulum

This is the list of notable stars in the constellation Triangulum, sorted by decreasing brightness.

Local Group

The Local Group is the galaxy group that includes the Milky Way.

It has a total diameter of roughly 3 Mpc (or 10 Mly ≈ 1023 m), and a total mass of the order of 2×1012 solar masses (4×1042 kg).

It consists of two clusters of galaxies in a "dumbbell" shape, the Milky Way and its satellites on one hand, and the Andromeda Galaxy and its satellites on the other. The two clusters are separated by about 0.8 Mpc and move towards one another with a velocity of 123 km/h. The group itself is a part of the larger Virgo Supercluster, which may be a part of the Laniakea Supercluster.

The total number of galaxies in the Local Group is unknown (due to its partial occlusion by the Milky Way) but known to exceed 54, most of them being

dwarf galaxies.

The two largest members, the Andromeda Galaxy and the Milky Way, are both spiral galaxies with masses of about 1012 solar masses each, and each have their own system of satellite galaxies:

The Andromeda Galaxy's satellite system consists of Messier 32 (M32), Messier 110 (M110), NGC 147, NGC 185, Andromeda I (And I), And II, And III, And V, And VI (also known as Pegasus Dwarf Spheroidal Galaxy, or Pegasus DSph), And VII (also known as Cassiopeia Dwarf Galaxy), And VIII, And IX, And X, And XI, And XIX, And XXI and And XXII, plus several additional ultra-faint dwarf spheroidal galaxies.

The Milky Way's satellite galaxies system comprises Sagittarius Dwarf Galaxy, Large Magellanic Cloud, Small Magellanic Cloud, Canis Major Dwarf Galaxy (disputed, considered by some not a galaxy), Ursa Minor Dwarf Galaxy, Draco Dwarf Galaxy, Carina Dwarf Galaxy, Sextans Dwarf Galaxy, Sculptor Dwarf Galaxy, Fornax Dwarf Galaxy, Leo I (a dwarf galaxy), Leo II (a dwarf galaxy), and Ursa Major I Dwarf Galaxy and Ursa Major II Dwarf Galaxy, plus several additional ultra-faint dwarf spheroidal galaxies.The Triangulum Galaxy is the third largest member of the Local Group, at about 5×1010 M☉, and the third spiral galaxy. It may or may not be a companion to the Andromeda Galaxy. Pisces Dwarf Galaxy is equidistant from the Andromeda Galaxy and the Triangulum Galaxy, so it may be a satellite of either.The membership of NGC 3109, with its companions Sextans A and the Antlia Dwarf Galaxy, is uncertain due to extreme distances from the center of the Local Group.

The other members of the group are likely gravitationally secluded from these large subgroups: IC 10, IC 1613, Phoenix Dwarf Galaxy, Leo A, Tucana Dwarf Galaxy, Cetus Dwarf Galaxy, Pegasus Dwarf Irregular Galaxy, Wolf–Lundmark–Melotte, Aquarius Dwarf Galaxy, and Sagittarius Dwarf Irregular Galaxy.


M33, M-33, or M.33 may refer to:

M-33 (Michigan highway), a state highway in Michigan

M33 cluster bomb, a Cold War-era U.S. biological cluster bomb

HMS M33, an M29-class monitor warship of the Royal Navy

M33 helmet, used by the Italian Army in World War II

Macchi M.33, an Italian racing flying boat of 1925

Miles M.33 Monitor, a 1944 twin engined British target tug aircraft

Mike Tempesta (aka M.33), a rock guitarist

Messier 33, or Triangulum Galaxy, a galaxy in the Local Group of galaxies

M33 (gene)

M33, US Army rocket launcher for the Honest John rocket

M33, the postcode district of Sale, a town in Greater Manchester, England

M33 X-7

M33 X-7 is a black hole binary system in the galaxy M33. The system is made up of a stellar-mass black hole and a companion star. M33 X-7 is the largest known stellar black hole with an estimated mass of 15.65 times that of the Sun (M☉).[7] The total mass of the system is estimated to be around 85.7 M☉, which would make it the most massive black hole binary system.

NGC 588

NGC 588 is a diffuse nebula located in the outskirts of the galaxy Messier 33, within the Triangulum constellation. It was discovered October 2 1861 by the German-Danish astronomer Heinrich d'Arrest.

NGC 592

NGC 592 is a H II region type emission nebula located in the Triangulum galaxy (M33) and thus in the constellation of Triangulum. The nebula contains an open cluster of stars and is approximately 2.86 million light-years away from Earth.

NGC 595

NGC 595 is an H II region in the Triangulum Galaxy. It was discovered by Heinrich Ludwig d'Arrest on October 1, 1864.

NGC 604

NGC 604 is an H II region inside the Triangulum Galaxy. It was discovered by William Herschel on September 11, 1784. It is among the largest H II regions in the Local Group of galaxies; at the galaxy's estimated distance of 2.7 million light-years, its longest diameter is roughly 1,520 light years (~460 parsecs), over 40 times the size of the visible portion of the Orion Nebula. It is over 6,300 times more luminous than the Orion Nebula, and if it were at the same distance it would outshine Venus. Its gas is ionized by a cluster of massive stars at its center. with 200 stars of spectral type O and WR, a mass of 105 solar masses, and an age of 3.5 million years; however, unlike the Large Magellanic Cloud's Tarantula Nebula central cluster (R136), NGC 604's one is much less compact and more similar to a large stellar association, being considered the prototypical example of a Scaled OB Association (SOBA)

Pan-Andromeda Archaeological Survey

Pan-Andromeda Archaeological Survey (PAndAS) is a large-scale astronomical survey using the Canada-France-Hawaii Telescope.

The survey is exploring the structure and content of the Andromeda Galaxy (M31) and its neighbour, the Triangulum Galaxy (M33). Clues to the formation of these galaxies may lie within the vast space being studied. PAndAS is searching for this history, hence the term "galactic archaeology".

The project is headed by Dr. Alan McConnachie at the Herzberg Institute of Astrophysics (NRC-HIA), and involves over twenty five investigators from that institute, as well as from universities in Canada, France, the United States, the United Kingdom, Germany, and Australia.

Pisces Dwarf

Pisces Dwarf is an irregular dwarf galaxy that is part of the Local Group. The galaxy, taking its name from the constellation Pisces where it appears, is suspected of being a satellite galaxy of the Triangulum Galaxy (M33). It displays a blueshift, as it is approaching the Milky Way at 287 km/s. It may be transition-type galaxy, somewhere between dwarf spheroidal and dwarf irregular. Alternatively, it may be a rare, but statistically acceptable, version of one of the two types.

Romano's Star

Romano's Star (GR 290) is a luminous blue variable star located in the Messier 33 galaxy in the constellation of Triangulum.

Triangulum (disambiguation)

Triangulum is a northern constellation.

Triangulum may also refer to:

AstronomyTriangulum Minus, an obsolete constellation which is part of Triangulum

Triangulum Australe, a small southern constellation

Triangulum Australe (Chinese astronomy)

Triangulum (Chinese astronomy)

Triangulum Galaxy, a spiral galaxy visible in Triangulum

Triangulum II, a dwarf galaxy companion of the Milky Way GalaxyOtherUSS Triangulum (AK-102), a US Navy cargo ship

The "Triangulum" story arc, an arc found in Shin Megami Tensei: Devil Survivor 2

Triangulum (species), species by the name 'triangulum'

Var 83

VHK 83 (Var 83 in the VHK survey) is a luminous blue variable (LBV) in the constellation Triangulum, in the Triangulum Galaxy. With its bolometric luminosity of at least 2,240,000 times that of the Sun (4,500,000 in some estimates), it was described as "the brightest nonstable star in M33" and is one of the most luminous stars known.

The brightness varies slowly and unpredictably over a 1-2 magnitude visual range and can remain approximately constant for many years. These variations, combined with the high luminosity and temperature of the star, caused it to be grouped with the Hubble-Sandage variables even before the term "Luminous Blue Variable" was more than a simple description. Despite widespread agreement that it is an LBV it has yet to be observed in outburst, although the temperature has been observed to change in tandem with the brightness variations.Temperature estimates for the star range from around 18,000K to well over 30,000K. The hotter temperatures found from fitting the spectral energy distribution (SED) are consistent with the calculated luminosity of an LBV in the quiescent stage, but the spectrum is that of a cooler star.

Triangulum Galaxy
H II regions
Suspected satellite galaxies
See also
Satellite galaxies
Catalogued stars

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