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UY Scuti

Coordinates: Sky map 18h 27m 36.53s, −12° 27′ 58.9″
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UY Scuti
File:UY Scuti, Hubble Telescope, 27 Feb 2015.jpeg
Close-up image of UY Scuti as taken from the Hubble Space Telescope. This photo was taken in 2015.
Observation data
Epoch J2000      Equinox J2000
Constellation Scutum
Right ascension 18h 27m 36.5334s[1]
Declination −12° 27′ 58.866″[1]
Apparent magnitude (V) 8.9[2] - 11.20[3]
Characteristics
Spectral type M4Ia[4]
U−B color index 3.29[4]
B−V color index 3.00[3]
Variable type SRC[5]
Astrometry
Proper motion (μ) RA: 1.3[6] mas/yr
Dec.: −1.6[6] mas/yr
Distance9,500 ly
(2,900[7] pc)
Absolute magnitude (MV)−6.2[8]
Details
Mass7–10[4] M☉
Radius1,708 ± 192[4] R☉
Luminosity340,000[4] L☉
Surface gravity (log g)−0.5[4] cgs
Temperature3,365±134[4] K
Other designations
UY Sct, BD-12 5055, IRC -10422, RAFGL 2162, HV 3805
Database references
SIMBADdata

UY Scuti is a red supergiant and pulsating variable star in the constellation Scutum. It is a current and leading candidate for being the largest known star by radius and is also one of the most luminous of its kind. It has an estimated radius of 1,708 solar radii (1.188×109 kilometres; 7.94 astronomical units); thus a volume nearly 5 billion times that of the Sun. It is approximately 2.9 kiloparsecs (9,500 light-years) from Earth. If placed at the center of the Solar System, its photosphere would at least engulf the orbit of Jupiter.

Nomenclature and history

File:UY Scuti zoomed in, Rutherford Observatory, 07 September 2014.jpeg
Dense starfield around the red supergiant star UY Scuti (brightest star in the image) as seen from the Rutherfurd Observatory in the Columbia University in New York, United States. The picture was captured in 2011.

UY Scuti was first cataloged in 1860 by German astronomers at the Bonn Observatory during the first sky survey of stars for the Bonner Durchmusterung Stellar Catalogue.[9] It was named BD -12 5055, the 5,055th star between 12°S and 13°S counting from 0h right ascension.

On the next detection of the star in the second survey it was found to have changed slightly in brightness, suggesting that it was a new variable star. In accordance with the international standard of designation of variable stars, it was called UY Scuti, the 38th variable star of the constellation Scutum (see variable star designation).[10]

UY Scuti is located a few degrees north of the A-type star Gamma Scuti and northeast of the Eagle Nebula. Although the star is very luminous it is, at its brightest, only 9th magnitude as viewed from Earth, due to its distance and location in the Zone of Avoidance within the Cygnus rift.[11]

Characteristics

An illustration of the approximate size of UY Scuti compared to the Sun

The star is classified as a semiregular variable with an approximate pulsation period of 740 days.[5][12] [13] It has the total bolometric power of 340,000 L☉.

Relative sizes of the planets in the Solar System and several stars, including UY Scuti:
1. Mercury < Mars < Venus < Earth
2. Earth < Neptune < Uranus < Saturn < Jupiter
3. Jupiter < Proxima Centauri < Sun < Sirius
4. Sirius < Pollux < Arcturus < Aldebaran
5. Aldebaran < Rigel < Antares < Betelgeuse
6. Betelgeuse < NML Cygni < VV Cephei A < VY Canis Majoris < UY Scuti.

In the summer of 2012, astronomers from the Very Large Telescope in the Atacama Desert in Chile measured the parameters of three red supergiants near the Galactic Center region:[4] UY Scuti, AH Scorpii, and KW Sagittarii. They determined that all three stars are over 1,000 times bigger than the Sun, making them some of the largest stars known. The stars' sizes were defined using the Rosseland Radius, the location at which the optical depth is 2/3.[14]

UY Scuti was found to be the largest of the three stars measured, at 1,708 ± 192 R☉. This makes the star's radius the largest of any star and approximately 1.9 times the size of Betelgeuse and more than 2.5 times larger than Antares at maximum.

A hypothetical object travelling at the speed of light would take about eight hours to travel around UY Scuti at maximum, whereas it would take 14.5 seconds to circle the Sun.[15]

Mass

UY Scuti's mass is also uncertain, primarily because it has no visible companion star by which its mass can be measured through gravitational interference. Stellar evolutionary models conclude that the initial mass of a star (the mass of a star when it is formed) reaching the red supergiant stage like UY Scuti would have been around 25 M☉ (possibly up to 40 M☉ for a non-rotating star), and has probably lost more than half of that.[4]

Supernova

Based on current models of stellar evolution, UY Scuti has begun to fuse helium and continues to fuse hydrogen in a shell around the core. The location of UY Scuti deep within the Milky Way disc suggests that it is a metal-rich star.[16]

After fusing heavy elements, its core will begin to produce iron, disrupting the balance of gravity and radiation in its core and resulting in a core collapse supernova. It is expected that stars like UY Scuti should evolve back to hotter temperatures to become a yellow hypergiant, luminous blue variable, or a Wolf–Rayet star, creating a strong stellar wind that will eject its outer layers and expose the core, before exploding as a type IIb, IIn, or type Ib/Ic supernova.[17]

See also

References

  1. ^ a b Hog, E.; Kuzmin, A.; Bastian, U.; Fabricius, C.; Kuimov, K.; Lindegren, L.; Makarov, V. V.; Roeser, S. (1998). "The TYCHO Reference Catalogue". Astronomy and Astrophysics. 335: L65. Bibcode:1998A&A...335L..65H.
  2. ^ Röser, S.; Bastian, U.; Kuzmin, A. (1994). "PPM Star Catalogue: The 90000 Stars Supplement". Astronomy and Astrophysics. 105. Bibcode:1994A&AS..105..301R.
  3. ^ a b Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
  4. ^ a b c d e f g h i Arroyo-Torres, B.; Wittkowski, M.; Marcaide, J. M.; Hauschildt, P. H. (2013). "The atmospheric structure and fundamental parameters of the red supergiants AH Scorpii, UY Scuti, and KW Sagittarii". Astronomy & Astrophysics. 554: A76. arXiv:1305.6179. Bibcode:2013A&A...554A..76A. doi:10.1051/0004-6361/201220920.
  5. ^ a b Kholopov, P. N.; Samus, N. N.; Kazarovets, E. V.; Perova, N. B. (1985). "The 67th Name-List of Variable Stars". Information Bulletin on Variable Stars. 2681: 1. Bibcode:1985IBVS.2681....1K.
  6. ^ a b Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H. doi:10.1888/0333750888/2862.
  7. ^ Sylvester, R. J.; Skinner, C. J.; Barlow, M. J. (1998). "Silicate and hydrocarbon emission from Galactic M supergiants". Monthly Notices of the Royal Astronomical Society. 301 (4): 1083–1094. Bibcode:1998MNRAS.301.1083S. doi:10.1046/j.1365-8711.1998.02078.x.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  8. ^ Lee, T. A. (1970). "Photometry of high-luminosity M-type stars". Astrophysical Journal. 162: 217. Bibcode:1970ApJ...162..217L. doi:10.1086/150648.
  9. ^ "UY Scuti - Universe Guide". Universe Guide. Retrieved 15 January 2016.
  10. ^ Prager, R. (1927). "Katalog und Ephemeriden veraenderlicher Sterne fuer 1927". Kleine Veroeffentlichungen der Universitaetssternwarte zu Berlin Babelsberg. 1: 1.i. Bibcode:1927KVeBB...1....1P.
  11. ^ "UY Sct (UY Scuti)". kusastro. Retrieved 15 January 2016.
  12. ^ Whiting, Wendy A. (1978). "Observations of Three Variable Stars in Scutum". The Journal of the American Association of Variable Star Observers. 7: 71. Bibcode:1978JAVSO...7...71W.
  13. ^ Jura, M.; Kleinmann, S. G. (1990). "Mass-losing M supergiants in the solar neighborhood". The Astrophysical Journal Supplement Series. 73: 769. Bibcode:1990ApJS...73..769J. doi:10.1086/191488.
  14. ^ Wehrse, R.; Scholz, M.; Baschek, B. (June 1991). "The parameters R and Teff in stellar models and observations". Astronomy and Astrophysics. 246 (2): 374–382. Bibcode:1991A&A...246..374B.
  15. ^ "Solar System Exploration: Planets: Sun: Facts & Figures". NASA. Archived from the original on January 2, 2008. Retrieved 15 January 2016. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  16. ^ Meynet, Georges (2008). Israelian, Garik (ed.). The metal-rich universe. Cambridge: Cambridge University Press. ISBN 9780521879989. Retrieved 15 January 2016.
  17. ^ Groh, Jose H.; Meynet, Georges; Georgy, Cyril; Ekström, Sylvia (2013). "Fundamental properties of core-collapse supernova and GRB progenitors: Predicting the look of massive stars before death". Astronomy & Astrophysics. 558: A131. arXiv:1308.4681. Bibcode:2013A&A...558A.131G. doi:10.1051/0004-6361/201321906.
Preceded by Largest known star
2014– [citation needed]

1,708 R☉

Succeeded by
TBA

Template:The 10 largest stars by radius

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