Triangle galaxy（Messier 33;NGC 598）, is located in the north skyTriangular seatOne insidespiral galaxy, DistanceearthAbout 3 millionLight year[1-2], there are manyVariable star, onLocal galaxy groupIs the third largest galaxyAndromeda galaxyandGalaxyIt is slightly smaller and may be constrained by the gravity of Andromeda galaxy, but it is still a large spiral galaxy in the universe.
In a good observation environment, the Triangle galaxy can be seen directly with the naked eye.Triangle galaxy is slightly tilted relative to the sky plane, so itsSwivel arm、Gas cloud, brightlyfixed starCan be presented well in front of us.
Triangle galaxy is named after its constellationTriangular seatThis is the constellation where it was found.
On some amateur astronomical references and some public websites, the Triangle Galaxy is sometimes informally called“Pinwheel galaxy ”[4]。However, inSIMBADThe astronomical data in theM101, and it is also marked as M101 in some astronomical databases and other public websites.[5]
position
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Triangle galaxy
M33 position nearAndromeda galaxyThe stargazers in these two galaxies can both see a very spectacularspiral galaxy[6]。 Seen from the Earth, this extremely clear M33 mosaic image, which is pieced together from 27 photos, beautifully presents the blue star clusters and pink stars on the loose spiral arms of the galaxyStar formationZone.Of which cavernousNGC 604Is the brightest star forming region on the vortex arm stretching from the center of the galaxy to the upper right.
Computer simulation of M31 from M33 and M33 from M31[6]
Like M31,M33 has manyVariable starLet this neighboring spiral galaxy become a measurementCosmic distanceA cosmic ruler of scale.
structure
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Swivel arm
Triangle galaxy has two main spiral arms, but they are not tightly intertwined. They are scattered into about 10 pieces not far awayStar Association、Ionized hydrogen region、SupergiantGather them.The composition distribution of dust and neutral hydrogen gas is very disordered, which is similar toDensity wave theoryThere are some differences.
Triangle galaxy[7]
The largest and brightest star forming regionNGC 604It contains a piece full ofO star(temperature up to 50000 Kelvin) andWolf LaYeXingThese special stars emit strong ultraviolet rays, marking the strong star formation activity of NGC 604.
Of the giant hydrogen ion region nearest to the nuclear regionHeavy elementThe abundance is 1.4 times that of the Sun and Orion Nebula, and less than one fifth of that near the Sun in the outer layer of the galaxy.
The galaxy's star association has been carefully studied andCatalogue143 of them are listed in.There are also some very bright stars outside the star association (and it is generally believed that massive stars are almost impossible to form in isolation), which indicates that there is still much to be improved on the theory of star formation.
The star clusters of the Triangle Galaxy also have their own characteristics: the color of the star clusters is very different from that of M31, and most of them appear relatively young, similar toMagellan CloudBlue inGlobular cluster。Further observation shows that most of them areOpen cluster。Astronomers speculate that the lack of true globular clusters is related to the smaller mass of M33.[7-8]
Stellar nucleus
In 1983, the orbiting EinsteinX-ray ObservatoryOne is detected in M33 nuclear areaX-ray source, similar toActive galactic nucleusCoupled X-ray source, but its energy is far less than that of typical X-ray sourcea quasarActive galactic nuclei.However, its energy is 10 times that of M31 and more than 10000 times that of the Milky Way.[8]
Scientists found thatAndromeda galaxyAnd Triangle galaxy“Hydrogen bridge”The total length reaches 782000 light years.be locatedAndromeda Galaxy The mysterious chain like matter between the Triangle galaxy and theNeutral hydrogenAtomic clumps, which exist around galaxies“Galactic halo”However, some of the clusters are unusual and seem to be a bridge between two galaxies."Galaxy halo" isspiral galaxyA layer of spherically distributed sparse material shrouded in the periphery, including manyfixed starAnd gas, etc.[9]
Development history
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M33: Triangular galaxy[11]
The Triangle Galaxy may have been discovered by Giovanni Batista Hodierna before 1654Open clusterNGC 752Listed in the same group.1764messier He was found alone again and was listed as M33 on August 25.On September 11, 1784, William Herschel added him to the catalog alone, numbered H V.17.He is also the first batch confirmed by the Earl of Ross III (Lord Ross)“Spiral nebula".
Herschel also put the brightest and largestIonized hydrogen region(including free hydrogen, diffusiveEmission nebula）It is listed separately as H III.150, and now it is also listed asNGC 604。 NGC 604, the largest known ionized hydrogen region with a diameter of about 1500, is located at the northernmost end of the core of the Triangle Galaxy from EarthLight year, with andOrion nebula Similar spectra.Herschel also marked three smaller areas of free hydrogen（NGC 588、NGC 592andNGC 595）。
distance
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At least two techniques have been used to measureM33Distance.Used in 2004Cepheid variableThe measured distance is 277 ± 130000 light years (850 ± 40kpc）。
In 2006, a group of astronomers announced that they had discoveredEclipsing binary。After studying this pair of eclipsing binaries, the size of the pair of eclipsing binaries was measured.After knowing the size and temperature, we can calculateAbsolute magnitude。When absolute magnitude sumApparent magnitudeOnce you know everything, you can calculate the distance.The distance thus calculated is 3.1 ± 200000 light years (940 ± 70Kilosecond gap）。
The distance obtained by averaging these two values is 292 ± 130000 light years (895 ± 40 thousand seconds).
Record
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Triangle galaxy "is about 3 million light years away from the earth, with an apparent magnitude of 5.7, (Guinness World Record for the farthest object visible to the naked eye)。[10]
