Quintuplet cluster

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Quintuplet Cluster
Uncovering the secrets of the Quintuplet Cluster.jpg
Infrared image of the Quintuplet Cluster
Credit: ESA/Hubble & NASA
Observation data (J2000. epoch)
Right ascension 17h 46m 13.9s [1]
Declination −28° 49′ 48″ [1]
Distance 26 kly (8 kpc [2] )
Apparent dimensions (V)50" (2 pc) [3]
Physical characteristics
Mass10,000 [3]   M☉
Estimated age4.8 million years [4]
Dense cluster of massive young stars near the Galactic Center. Optically obscured.
Other designations IRAS 17430-2848, G000.16-00.06
Associations
Constellation Sagittarius
See also: Open cluster, List of open clusters

The Quintuplet cluster is a dense cluster of massive young stars about 100 light years from the Galactic Center (GC). Its name comes from the fact it has five prominent infrared sources residing in it. Along with the Arches Cluster it is one of two in the immediate GC region. Due to heavy extinction by dust in the vicinity, it is invisible to optical observation and must be studied in the X-ray, radio, and infrared bands.

Contents

The Quintuplet is less compact than the nearby Arches Cluster, with fewer of the most massive and luminous stars, but it does have the distinction of hosting two of the extremely rare luminous blue variables, the Pistol Star and the less well-known qF 362 (aka V4650 Sgr), and a third just a few parsecs away. [2] It also contains a number of red supergiants, all suggesting a slightly more evolved cluster around 4 million years old. [5]

Discovery and naming

The trapezium of four bright red stars just below centre, plus one to the left, are the original Quintuplet (HST/NICMOS image) Quintuplet cluster.jpg
The trapezium of four bright red stars just below centre, plus one to the left, are the original Quintuplet (HST/NICMOS image)

The Quintuplet was originally identified in 1983 as a pair of infra-red sources in a 2.5 micron survey of the galactic centre. [6] These two sources were numbered 3 and 4, and later referred to with the acronym GCS for Galactic Centre Source. GCS-3 was later resolved into four sources, labelled I-IV, that together with GCS-4 formed a compact quintuplet of unusually bright small objects. They were assumed to be young hot luminous stars surrounded by dust shells and therefore extremely reddened. [7]

In 1990, a total of 15 sources in the Quintuplet region was studied in more detail at several wavelengths, later referred to by Q or GMM (after the authors Glass, Moneti, and Moorwood) numbers. The original five stars were identified as numbers Q1, Q2, Q3, Q4, and Q9, with additional sources Q5 and Q6 identified as part of the same cluster. They were still considered to be protostars reddened by surrounding dust. [8]

In 1994, several stars were identified as having broad helium emission lines in their spectra, and some showed narrow hydrogen emission lines. This was completely unexpected for protostars, instead suggesting the objects were much more evolved stars. [9] Shortly afterwards two emission line stars were classified as Wolf Rayet stars, and a third as a Luminous Blue Variable that was thought to be one of the most luminous stars in the galaxy. A small number of red supergiants were also identified, narrowing the likely age of the cluster. [10]

In 1999, a study of nearly 600 stars in the cluster showed that the Quintuplet contained more Wolf–Rayet stars than any known cluster, as well as a second Luminous Blue Variable. The numbers from this survey are referred to as qF, or sometimes as FMM after all three authors (but not QMM). [3] A 2008 study of the cluster used LHO numbers for the members and clarified the status of the unusual reddened Wolf–Rayet stars as WC stars surrounded by dust presumed to be formed from colliding winds between the WR component and a less evolved OB companion. [11] [12]

The cluster was also catalogued as a first magnitude "stellar" source at 4.2 microns in the Air Force Geophysics Lab survey and given the number 2004 (AFGL 2004). [13] [14]

Properties

Mid-IR image of the centre of the galaxy, with the Quintuplet stars as the brightest source to the left of the centre (and 2nd inset) Ssc2006-02b.jpg
Mid-IR image of the centre of the galaxy, with the Quintuplet stars as the brightest source to the left of the centre (and 2nd inset)
Image of the Quintuplet cluster's brightest stars; V4998 Sagittarii, The Pistol star, and qF362 Quintuplet cluster region (1002.3379).jpg
Image of the Quintuplet cluster's brightest stars; V4998 Sagittarii, The Pistol star, and qF362

The Quintuplet is seen (in the infra-red) 12 arc-minutes NW of Sagittarius A* (Sgr A*). The cluster stars and associated objects such as the Pistol Nebula have large radial velocities only likely to be from orbiting close to the galactic centre, so the cluster is thought to be physically associated with the galactic centre. [3] The galactic centre is considered to be about 8 kpc away, so the projected distance of the Quintuplet on the sky is 30 pc from Sagittarius A*. [15]

The age of the quintuplet can be estimated from the likely ages of its member stars. Mapping the stars of the cluster to evolutionary isochrones gives ages around 4 million years. [4] [3] However stars such as the two (or three) LBVs are expected to explode as supernovae within three million years, an obvious problem. It has been suggested that the age may be as low as 3.3–3.6 million years or that star formation was staggered over a million years or more [5] Another proposal is that the remaining highly massive stars were formed or rejuvenated by binary interactions. [4]

The masses of stars clusters can be measured by integrating the stellar mass function. Although only the most massive cluster members can be detected, the mass function can be estimated to lower levels and the cluster mass is calculated to be around 10,000 M☉. [3]

Members

The Quintuplet contains a number of massive and somewhat evolved stars, including 21 Wolf–Rayet stars, 2 luminous blue variables (three including the nearby runaway V4998 Sagittarii), and a number of red supergiants. There is also associated nebulosity ionised by the hot stars, most notably the Pistol Nebula between the Pistol Star and the core of the Quintuplet. [16]

Prominent stars (in K band infra-red)
GCS [6] Q/GMM [8] LHO [16] qF/FMM [3] Other namesSpectral type [16] Magnitude (KS) [16] Luminosity (L☉)Temperature (K)
3-IV175243 WR 102da WC9?d7.9~150,000 [17] ~45,000 [17]
3-II242231 WR 102dc WC9d + OB6.7~150,000 [17] ~45,000 [17]
4319211 WR 102ha WC8/9d + OB7.2~200,000 [17] ~50,000 [17]
3-I484251 WR 102dd WC9d7.8~150,000 [17] ~45,000 [17]
5115270N V4646 Sgr M2 I8.6 (var?)24,000 [5] 3,600 [5] [ failed verification ]
679250WC9d9.3~150,000 [17] ~45,000 [17]
77192M6 I7.647,000 [5] 3,274 [5]
867240 WR 102hb WN9h [5] 9.62,600,000 [18] 25,100 [18]
3-III9102258 WR 102db WC9?d9.2~200,000 [17] ~45,000 [17]
1071241 WR 102ea WN9h [5] 8.82,500,000 [18] 25,100 [18]
1147235N WR 102f WC810.4~200,000 [17] ~60,000 [17]
1277278O6–8 I eq?9.6~1,200,000 [5] ~35,000 [5]
13100257O6–8 I fe9.4~1,400,000 [5] ~35,000 [5]
14146307AO6–8 I f?8.7~2,500,000 [5] ~35,000 [5]
15110270S WR 102df O6–8 I f (Of/WN?)10.61,600,000 [18] 25,100 [18]
134 Pistol Star LBV 7.3 [2] 3,300,000 [19] [20] 11,800 [21]
362 V4650 Sgr LBV 7.1 [2] 1,800,000 [21] 11,300 [21]
99256 WR 102i WN9h [18] 10.51,500,000 [18] 31,600 [18]
158320 WR 102d WN9h [18] 10.51,200,000 [18] 35,100 [18]
V4998 Sgr LBV 7.5 [2] 1,600,000–4,000,000 [22] 12,000

Related Research Articles

<span class="mw-page-title-main">Pistol Star</span> Hypergiant star in Sagittarius

The Pistol Star is an extremely luminous blue hypergiant star, one of the most luminous and massive known in the Milky Way. It is one of many massive young stars in the Quintuplet cluster in the Galactic Center region. The star owes its name to the shape of the Pistol Nebula, which it illuminates. It is located approximately 25,000 light-years from Earth in the direction of Sagittarius. The star has a large mass comparable to V4998 Sagittarii and a luminosity 3.3 million times that of the Sun (L☉). It would be visible to the naked eye as a 4th-magnitude star if it were not for the interstellar dust near the Center of the Milky Way that absorbs almost all of its visible light.

<span class="mw-page-title-main">LBV 1806−20</span> Likely binary star in the constellation Sagittarius

LBV 1806−20 is a candidate luminous blue variable (LBV) and likely binary star located around 28,000 light-years (8,700 pc) from the Sun, towards the center of the Milky Way. It has an estimated mass of around 36 solar masses and an estimated variable luminosity of around two million times that of the Sun. It is highly luminous but is invisible from the Solar System at visual wavelengths because less than one billionth of its visible light reaches us.

<span class="mw-page-title-main">Arches Cluster</span>

The Arches Cluster is the densest known star cluster in the Milky Way, about 100 light-years from its center in the constellation Sagittarius, 25,000 light-years from Earth. Its discovery was reported by Nagata et al. in 1995, and independently by Cotera et al. in 1996. Due to extremely heavy optical extinction by dust in this region, the cluster is obscured in the visual bands, and is observed in the X-ray, infrared and radio bands. It contains approximately 135 young, very hot stars that are many times larger and more massive than the Sun, plus many thousands of less massive stars.

<span class="mw-page-title-main">Westerlund 1</span> Super star cluster in the Milky Way Galaxy

Westerlund 1 is a compact young super star cluster about 3.8 kpc away from Earth. It is thought to be the most massive young star cluster in the Milky Way, and was discovered by Bengt Westerlund in 1961 but remained largely unstudied for many years due to high interstellar absorption in its direction. In the future, it will probably evolve into a globular cluster.

<span class="mw-page-title-main">WR 102ka</span> Star in the constellation Sagittarius

WR 102ka, also known as the Peony star, is a slash star that is one of several candidates for the most luminous-known star in the Milky Way.

<span class="mw-page-title-main">Hypergiant</span> Rare star with tremendous luminosity and high rates of mass loss by stellar winds

A hypergiant (luminosity class 0 or Ia+) is a very rare type of star that has an extremely high luminosity, mass, size and mass loss because of its extreme stellar winds. The term hypergiant is defined as luminosity class 0 (zero) in the MKK system. However, this is rarely seen in literature or in published spectral classifications, except for specific well-defined groups such as the yellow hypergiants, RSG (red supergiants), or blue B(e) supergiants with emission spectra. More commonly, hypergiants are classed as Ia-0 or Ia+, but red supergiants are rarely assigned these spectral classifications. Astronomers are interested in these stars because they relate to understanding stellar evolution, especially star formation, stability, and their expected demise as supernovae.

<span class="mw-page-title-main">Cygnus OB2</span> Cluster of massive and luminous stars

Cygnus OB2 is an OB association that is home to some of the most massive and most luminous stars known, including suspected Luminous blue variable Cyg OB2 #12. It also includes one of the largest known stars, NML Cygni. The region is embedded within a wider one of star formation known as Cygnus X, which is one of the most luminous objects in the sky at radio wavelengths. The region is approximately 1,570 parsecs from Earth in the constellation of Cygnus.

<span class="mw-page-title-main">WR 102ea</span> Star in the constellation Sagittarius

WR 102ea is a Wolf–Rayet star in the Sagittarius constellation. It is the third most luminous star in the Quintuplet cluster after WR 102hb. With a luminosity of 2,500,000 times solar, it is also one of the most luminous stars known. Despite the high luminosity it can only be observed at infra-red wavelengths due to the dimming effect of intervening dust on visual light.

<span class="mw-page-title-main">WR 25</span> Binary star system in the constellation Carina

WR 25 is a binary star system in the turbulent star-forming region the Carina Nebula, about 6,800 light-years from Earth. It contains a Wolf-Rayet star and a hot luminous companion and is a member of the Trumpler 16 cluster. The name comes from the Catalogue of Galactic Wolf–Rayet Stars.

<span class="mw-page-title-main">WR 102c</span>

WR 102c is a Wolf–Rayet star located in the constellation Sagittarius towards the galactic centre. It is only a few parsecs from the Quintuplet Cluster, within the Sickle Nebula.

<span class="mw-page-title-main">V4998 Sagittarii</span> Luminous blue variable star in the constellation Sagittarius

V4998 Sagittarii is a luminous blue variable star (LBV) in the constellation of Sagittarius. Located some 25,000 light-years away, the star is positioned about 7 pc away from a starburst cluster known as the Quintuplet cluster. It has an ejection nebula measuring over 0.8 pc in diameter, formed 5000-10,000 years ago through large eruptions. The star has a large mass comparable to the Pistol Star and a luminosity of around 4 million times the Sun (L☉). This places the star as one of the most massive and luminous stars known.

<span class="mw-page-title-main">WR 102</span> Star in the constellation Sagittarius

WR 102 is a Wolf–Rayet star in the constellation Sagittarius, an extremely rare star on the WO oxygen sequence. It is a luminous and very hot star, highly evolved and close to exploding as a supernova.

<span class="mw-page-title-main">V4650 Sagittarii</span> Luminous blue variable star in the constellation Sagittarius

V4650 Sagittarii (qF362) is a luminous blue variable star (LBV) in the constellation of Sagittarius. Located some 25,000 light years away, the star is positioned on the edge of a starburst cluster known as the Quintuplet cluster.

<span class="mw-page-title-main">WR 31a</span> Wolf Rayet star in the constellation Carina

WR 31a, commonly referred to as Hen 3-519, is a Wolf–Rayet (WR) star in the southern constellation of Carina that is surrounded by an expanding Wolf–Rayet nebula. It is not a classical old stripped-envelope WR star, but a young massive star which still has some hydrogen left in its atmosphere.

WR 2 is a Wolf-Rayet star located around 8,000 light years away from Earth in the constellation of Cassiopeia, in the stellar association Cassiopeia OB1. It is smaller than the Sun, but due to a temperature over 140,000 K it is 282,000 times as luminous as the Sun. With a radius of 89% that of the Sun, it is the smallest known WN star in the Milky Way.

<span class="mw-page-title-main">HM 1</span> Open cluster in the constellation Scorpius

HM 1, also known as Havlen-Moffat 1, is an open cluster located in the constellation of Scorpius, close to the galactic plane. It was first observed by R. J. Havlen and A. F. J. Moffat in 1976. HM 1 is thought to be 9,500 to 12,700 light-years away from the Earth, beyond the Carina–Sagittarius Arm. It is heavily reddened by interstellar extinction, so although it comprises mostly blue-colored stars, it appears brighter for longer-wavelength passbands. It is projected against the H II region known as RCW 121, and appears to be the source of ionization for the nearby regions RCW 122 and RCW 123.

References

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  9. ↑ Moneti, A.; Glass, I. S.; Moorwood, A. F. M. (1994). "Spectroscopy and Further Imaging of IRAS Sources Near the Galactic Centre". Monthly Notices of the Royal Astronomical Society. 268: 194–202. Bibcode:1994MNRAS.268..194M. doi: 10.1093/mnras/268.1.194 .
  10. ↑ Figer, Donald F.; McLean, Ian S.; Morris, Mark (1995). "Two New Wolf-Rayet Stars and a Luminous Blue Variable Star in the Quintuplet (AFGL 2004) near the Galactic Center". Astrophysical Journal Letters. 447: L29–L32. Bibcode:1995ApJ...447L..29F. doi: 10.1086/309551 .
  11. ↑ Okuda, Haruyuki; Shibai, Hiroshi; Nakagawa, Takao; Matsuhara, Hideo; Kobayashi, Yukiyasu; Kaifu, Norio; Nagata, Tetsuya; Gatley, I.; Geballe, T. R. (1990). "An infrared quintuplet near the Galactic center". The Astrophysical Journal. 351: 89. Bibcode:1990ApJ...351...89O. doi: 10.1086/168447 .
  12. ↑ Moneti, A.; Stolovy, S.; Blommaert, J. A. D. L.; Figer, D. F.; Najarro, F. (2001). "Mid-infrared imaging and spectroscopy of the enigmatic cocoon stars in the Quintuplet Cluster". Astronomy and Astrophysics. 366: 106–120. arXiv: astro-ph/0010558 . Bibcode:2001A&A...366..106M. doi:10.1051/0004-6361:20000192. S2CID   9973563.
  13. ↑ Gullixson, C.; Gehrz, R. D.; Hackwell, J. A.; Grasdalen, G. L.; Castelaz, M. (1983). "The stellar component of the galaxy as seen by the AFGL infrared sky survey". Astrophysical Journal Supplement Series. 53: 413. Bibcode:1983ApJS...53..413G. doi: 10.1086/190897 .
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  15. ↑ Lang, Cornelia C.; Figer, Don F.; Goss, W. M.; Morris, Mark (1999). "Radio Detections of Stellar Winds from the Pistol Star and Other Stars in the Galactic Center Quintuplet Cluster". The Astronomical Journal. 118 (5): 2327–2330. arXiv: astro-ph/9907176 . Bibcode:1999AJ....118.2327L. doi:10.1086/301092. S2CID   12515939.
  16. 1 2 3 4 Liermann, A.; Hamann, W.-R.; Oskinova, L. M. (2009). "The Quintuplet cluster". Astronomy and Astrophysics. 494 (3): 1137–1166. arXiv: 0809.5199 . Bibcode:2009A&A...494.1137L. doi:10.1051/0004-6361:200810371. S2CID   260300.
  17. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Sander, A.; Hamann, W.-R.; Todt, H. (2012). "The Galactic WC stars". Astronomy & Astrophysics. 540: A144. arXiv: 1201.6354 . Bibcode:2012A&A...540A.144S. doi:10.1051/0004-6361/201117830. S2CID   119182468.
  18. 1 2 3 4 5 6 7 8 9 10 11 12 Liermann, A.; Hamann, W.-R.; Oskinova, L. M.; Todt, H.; Butler, K. (2010). "The Quintuplet cluster". Astronomy & Astrophysics. 524: A82. arXiv: 1011.5796 . Bibcode:2010A&A...524A..82L. doi:10.1051/0004-6361/200912612. S2CID   30091594.
  19. ↑ Lau, R. M.; Herter, T. L.; Morris, M. R.; Adams, J. D. (2014). "Nature Versus Nurture: Luminous Blue Variable Nebulae in and Near Massive Stellar Clusters at the Galactic Center". The Astrophysical Journal. 785 (2): 120. arXiv: 1403.5298 . Bibcode:2014ApJ...785..120L. doi:10.1088/0004-637X/785/2/120. S2CID   118447462.
  20. ↑ Mauerhan, J. C.; Morris, M. R.; Cotera, A.; Dong, H.; Wang, Q. D.; Stolovy, S. R.; Lang, C.; Glass, I. S. (2010). "Discovery of a Luminous Blue Variable with an Ejection Nebula Near the Quintuplet Cluster". The Astrophysical Journal. 713 (1): L33–L36. arXiv: 1002.3379 . Bibcode:2010ApJ...713L..33M. doi:10.1088/2041-8205/713/1/L33. S2CID   42696538.
  21. 1 2 3 Najarro, Francisco; Figer, Don F.; Hillier, D. John; Geballe, T. R.; Kudritzki, Rolf P. (2009). "Metallicity in the Galactic Center: The Quintuplet Cluster". The Astrophysical Journal. 691 (2): 1816–1827. arXiv: 0809.3185 . Bibcode:2009ApJ...691.1816N. doi:10.1088/0004-637X/691/2/1816. S2CID   15473563.
  22. ↑ Nazé, Y.; Rauw, G.; Hutsemékers, D. (2012). "The first X-ray survey of Galactic luminous blue variables". Astronomy & Astrophysics. 538: A47. arXiv: 1111.6375 . Bibcode:2012A&A...538A..47N. doi:10.1051/0004-6361/201118040. S2CID   43688343.
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