Triangulum Galaxy
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The Triangulum Galaxy |
|
| Observation data: J2000 epoch | |
|---|---|
| Constellation: | Triangulum |
| Right ascension: | 01h 33m 50.9s[1] |
| Declination: | +30° 39′ 36″[1] |
| Redshift: | -179 ± 3 km/s[1] |
| Distance: | 2.92 ± 0.13 Mly (895 ± 40 kpc)[2][3][4][5] |
| Type: | SA(s)cd[1] |
| Apparent dimensions (V): | 70′.8 × 41′.7[1] |
| Apparent magnitude (V): | 6.3[1] |
| Notable features: | NGC 604 |
| Other designations | |
| Messier 33,[1] NGC 598,[1] UGC 1117,[1] PGC 5818[1] | |
| See also: Galaxy, List of galaxies | |
The Triangulum Galaxy (also known as Messier 33 or NGC 598) is a spiral galaxy about 3.14 million light-years away in the constellation Triangulum. The Triangulum Galaxy is small relative to its larger neighbors, the Milky Way Galaxy and the Andromeda Galaxy, but is about average compared to most spiral galaxies in the universe. It is the smallest of the three largest galaxies (all of them spiral galaxies) in the Local group of galaxies and may be a gravitationally bound companion of Andromeda. The Pisces Dwarf (LGS 3), one of the small Local Group member galaxies, is possibly a satellite of Triangulum.
The Triangulum Galaxy can be seen with the naked eye under exceptionally good conditions; it is one of the most distant objects that can be seen without aid.[6] However, amateur astronomers may confuse the object with the nearby NGC 752, an open cluster that is brighter than the Triangulum Galaxy.
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 is computed which gives the velocity that Triangulum is moving towards Andromeda.[7]
The Triangulum has a H II nucleus.[8]
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[edit] General information
The Triangulum Galaxy was probably discovered by Giovanni Batista Hodierna before 1654, who may have grouped it together with open cluster NGC 752. It was independently discovered by Charles Messier in 1764, who catalogued it as M33 on August 25. M33 was also catalogued independently by William Herschel on September 11, 1784 number H V.17. It was among the first "spiral nebulae" identified as such by Lord Rosse.
Herschel also cataloged 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, which eventually obtained NGC number 604. As seen from Earth NGC 604 is located northeast of the galaxy's central core, and is one of the largest H II regions known with a diameter of nearly 1500 light-years and a spectrum similar to the Orion Nebula. Herschel also noted 3 other smaller H II regions (NGC 588, 592 and 595).
[edit] Distance
At least two techniques have been used to measure distances to M 33. Using the Cepheid variable method, an estimate of 2.77 ± 0.13 Mly (850 ± 40 kpc) was achieved in 2004.[2][3]
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, the 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 3.1 ± 0.2 Mly (940 ± 70 kpc).[4]
Averaged together, all these distance measurements give a combined distance estimate of 2.92 ± 0.13 Mly (895 ± 40 kpc).[5]
[edit] References in fiction
- See Galaxies in fiction.
[edit] See also
[edit] References
- ^ a b c d e f g h i j NASA/IPAC Extragalactic Database. Results for NGC 598. Retrieved on December 1, 2006.
- ^ a b I. D. Karachentsev, V. E. Karachentseva, W. K. Hutchmeier, D. I. Makarov (2004). "A Catalog of Neighboring Galaxies". Astronomical Journal 127: 2031-2068.
- ^ a b Karachentsev, I. D.; Kashibadze, O. G. (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics 49 (1): 3-18.
- ^ a b Bonanos, A. Z.; Stanek, K. Z.; Kudritzki, R. P.; Macri, L.; Sasselov, D. D.; Kaluzny, J.; Bersier, D.; Bresolin, F.; Matheson, T.; Mochejska, B. J.; Przybilla, N.; Szentgyorgyi, A. H.; Tonry, J.; Torres, G. (2006). "The First DIRECT Distance to a Detached Eclipsing Binary in M33". Astrophysics and Space Science Online First.
- ^ a b average(850 ± 40, 940 ± 70) = ((850 + 940) / 2) ± ((402 + 702)0.5 / 2) = 895 ± 40
- ^ S. J. O'Meara (1998). The Messier Objects. Cambridge: Cambridge University Press. ISBN 0-521-53332-6.
- ^ Brunthaler, Andreas; Reid, Mark J.; Falcke, Heino; Greenhill, Lincoln J.; Henkel, Christian (2005). "The Geometric Distance and Proper Motion of the Triangulum Galaxy (M33)". Science 307 (5714): 1440-1443.
- ^ Ho, Luis C.; Alexei V. Filippenko & Wallace L. W. Sargent (October 1997), "A Search for "Dwarf" Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies", Astrophysical Journal Supplement 112: 315-390
