NGC 1851

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NGC 1851
Caldwell 73 (50291856937).jpg
Hubble image of NGC 1851
Observation data (J2000 epoch)
Class II [1]
Constellation Columba
Right ascension 05h 14m 06.76s [2]
Declination –40° 02′ 47.6″ [2]
Distance 39.5  kly (12.1  kpc) [3]
Apparent magnitude (V)7.3 [4]
Apparent dimensions (V)11′ [4]
Physical characteristics
Absolute magnitude −7.80 [3]
Mass5.51×105 [5]   M☉
Metallicity  = −1.27 [3] dex
Estimated age9.2  Gyr [6]
Other designationsGCl 9, [7] ESO 305-SC 016, [8] Caldwell 73, Melotte 30
See also: Globular cluster, List of globular clusters

NGC 1851 (also known as Caldwell 73) [9] is a relatively massive [3] globular cluster located in the southern constellation of Columba. Astronomer John Dreyer described it as not very bright but very large, round, well resolved, and clearly consisting of stars. [4] It is located 39.5 kilolight-years from the Sun, and 54.1 kilolight-years from the Galactic Center. [3] The cluster is following a highly eccentric orbit through the galaxy, with an eccentricity of about 0.7. [10]

This object has a Shapley–Sawyer Concentration Class of II, [1] indicating a dense central concentration. It has one of the highest concentrations known for Galactic globular clusters. [3] The stellar components show two separate populations of subgiant stars, with the brighter branch being more concentrated in the outer regions of the cluster. [10] NGC 1851 is an estimated 9.2 [6]  billion years old with 551,000 times the mass of the Sun. [5]

The cluster is surrounded by a diffuse halo of stars that stretches outward to a radius of 240 pc or more. This feature, if combined with the lack of tidal tail or associated stream of stars, suggests the cluster may be a stripped dwarf galaxy nucleus, similar to Omega Centauri, that has been accreted by the Milky Way. [3] The tidal tail is still present though. [11] It is also possible the cluster is the result of the merger of two separate clusters, but the fact that they would need to have the same metallicity – what astronomers term the abundance of elements other than hydrogen and helium – makes this scenario less likely. [10]

PSR J0514-4002A is a millisecond pulsar in NGC 1851. It is orbiting a massive object that may also be a neutron star. The pair have an orbital period of 18.8 days with a large eccentricity of 0.89. [12] A nearby pulsar PSR J0514−4002E is orbiting a massive object which appears to occupy the "mass gap" between the heaviest neutron stars and the lightest black holes, making it an unusual star system which may be useful for studying theories of gravity. [13] The TRAPUM Large Survey Project using the MeerKAT radio telescope discovered thirteen new pulsars in the cluster, which consist of six isolated millisecond pulsars (MSPs) and seven binary pulsars, of which six are MSPs and one is mildly recycled. [14] 43 RR Lyrae variables have been discovered in the cluster, which show this to be an Oosterhoff type I cluster but having properties similar to type II. Two populations of horizontal branch stars have been observed, with the pair having an age difference of around two billion years. [15] Spectroscopic analysis of the red giant branch member stars suggests there are actually three different populations of stars in the cluster. [16]

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<span class="mw-page-title-main">Messier 28</span> Globular cluster in the constellation of Sagittarius

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<span class="mw-page-title-main">Messier 62</span> Globular cluster in the constellation Ophiuchus

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<span class="mw-page-title-main">Messier 79</span> Globular cluster in constellation Lepus

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<span class="mw-page-title-main">47 Tucanae</span> Globular cluster in the constellation Tucana

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<span class="mw-page-title-main">NGC 5986</span> Globular cluster in the constellation Lupus

NGC 5986 is a globular cluster of stars in the southern constellation of Lupus, located at a distance of approximately 34 kilolight-years from the Sun. It was discovered by Scottish astronomer James Dunlop on May 10, 1826. John L. E. Dreyer described it as, "a remarkable object, a globular cluster, very bright, large, round, very gradually brighter middle, stars of 13th to 15th magnitude". Its prograde–retrograde orbit through the Milky Way galaxy is considered irregular and highly eccentric. It has a mean heliocentric radial velocity of +100 km/s. The galacto-centric distance is 17 kly (5.2 kpc), which puts it in the galaxy's inner halo.

<span class="mw-page-title-main">NGC 6760</span> Globular cluster in the constellation Aquila

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<span class="mw-page-title-main">NGC 6934</span> Globular cluster in the constellation Delphinus

NGC 6934 is a globular cluster of stars in the northern constellation of Delphinus, about 52 kilolight-years distant from the Sun. It was discovered by the German-born astronomer William Herschel on 24 September 1785. The cluster is following a highly eccentric orbit through the Milky Way along an orbital plane that is inclined by 73° to the galactic plane. It may share a common dynamic origin with NGC 5466. As of 2018, it has been poorly studied.

<span class="mw-page-title-main">NGC 2808</span> Globular cluster in the constellation Carina

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<span class="mw-page-title-main">NGC 6539</span> Globular cluster in the constellation Serpens

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<span class="mw-page-title-main">NGC 362</span> Globular cluster located in the constellation Tucana

NGC 362 is a globular cluster located in the constellation Tucana in the Southern Hemisphere, slightly north of the Small Magellanic Cloud, to which it is completely unrelated. It was discovered on August 1, 1826, by James Dunlop. It is visible to the naked eye in dark skies, and is an impressive sight in a telescope, although it is somewhat overshadowed by its larger and brighter neighbour 47 Tucanae.

<span class="mw-page-title-main">NGC 1261</span> Globular cluster in the constellation Horologium

NGC 1261 is a globular cluster of stars in the southern constellation of Horologium, first discovered by Scottish astronomer James Dunlop in 1826. The cluster is located at a distance of 53 kilolight-years from the Sun, and 59 kilolight-years from the Galactic Center. It is about 10.24 billion years old with 341,000 times the mass of the Sun. The cluster does not display the normal indications of core collapse, but evidence suggests it may have instead passed through a post core-collapse bounce state within the past two billion years. The central luminosity density is 2.22 L☉·pc−3, which is low for a globular cluster. Despite this, it has a Shapley–Sawyer Concentration Class of II, indicating a dense central concentration.

<span class="mw-page-title-main">NGC 2298</span> Globular cluster in the constellation Puppis

NGC 2298 is a globular cluster in the southern constellation of Puppis. Discovered by James Dunlop on May 30, 1826, it is probably a former member of the disputed Canis Major Dwarf galaxy.

<span class="mw-page-title-main">NGC 6401</span> Globular cluster in the constellation Ophiuchus

NGC 6401 is a globular cluster in the equatorial constellation of Ophiuchus. This star cluster was discovered by German-English astronomer William Herschel in 1784, but he mistakenly classified it as a bright nebula. Later, his son John Herschel came to the same conclusion because the technology of the day did not allow the individual stars to be visually resolved. It is visible in a small telescope, with an apparent visual magnitude of 7.4 and an angular diameter of 4.8′.

<span class="mw-page-title-main">NGC 6256</span> Globular cluster in the constellation Scorpius

NGC 6256 is a globular cluster of stars in the southern constellation of Scorpius. It was discovered by the Scottish astronomer James Dunlop on Aug 2, 1826. In J. L. E. Dreyer's New General Catalogue annotation it is described as, "very faint, very large, very gradually bright in the middle, well resolved clearly consisting of stars." The cluster is located at a distance of 22 thousand light-years (6.8 kpc) from the Sun.

<span class="mw-page-title-main">NGC 6441</span> Globular cluster in Scorpius

NGC 6441, sometimes also known as the Silver Nugget Cluster, is a globular cluster in the southern constellation of Scorpius. It was discovered by the Scottish astronomer James Dunlop on May 13, 1826, who described it as "a small, well-defined rather bright nebula, about 20″ in diameter". The cluster is located 5 arc minutes east-northeast of the star G Scorpii, and is some 43,000 light-years from the Sun.

<span class="mw-page-title-main">NGC 6440</span> Globular cluster in the constellation of Sagittarius

NGC 6440 is a globular cluster of stars in the southern constellation of Sagittarius. It discovered by German-English astronomer William Herschel on 28 May 1786. With has an apparent visual magnitude of 9.3 and an angular diameter of 4.4′, it can be viewed as a fuzzy blob in a small telescope. Its Shapley–Sawyer Concentration Class is V.

<span class="mw-page-title-main">Gaia Sausage</span> Remains galaxy merger in the Milky Way

The Gaia Sausage or Gaia Enceladus is the remains of a dwarf galaxy that merged with the Milky Way about 8–11 billion years ago. At least eight globular clusters were added to the Milky Way along with 50 billion solar masses of stars, gas and dark matter. It represents the last major merger of the Milky Way.

References

  1. 1 2 Shapley, Harlow; Sawyer, Helen B. (August 1927), "A Classification of Globular Clusters", Harvard College Observatory Bulletin, 849 (849): 11–14, Bibcode:1927BHarO.849...11S.
  2. 1 2 Goldsbury, Ryan; et al. (December 2010), "The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters", The Astronomical Journal, 140 (6): 1830–1837, arXiv: 1008.2755 , Bibcode:2010AJ....140.1830G, doi:10.1088/0004-6256/140/6/1830, S2CID   119183070.
  3. 1 2 3 4 5 6 7 Kuzma, P. B.; et al. (January 2018), "The outer envelopes of globular clusters. II. NGC 1851, NGC 5824 and NGC 1261*", Monthly Notices of the Royal Astronomical Society, 473 (3): 2881–2898, arXiv: 1709.02915 , Bibcode:2018MNRAS.473.2881K, doi: 10.1093/mnras/stx2353 .
  4. 1 2 3 "SEDS NGC Catalog Online". Results for NGC 1851. Retrieved 2011-01-09.
  5. 1 2 Boyles, J.; et al. (November 2011), "Young Radio Pulsars in Galactic Globular Clusters", The Astrophysical Journal, 742 (1): 51, arXiv: 1108.4402 , Bibcode:2011ApJ...742...51B, doi:10.1088/0004-637X/742/1/51, S2CID   118649860.
  6. 1 2 Koleva, M.; et al. (April 2008), "Spectroscopic ages and metallicities of stellar populations: validation of full spectrum fitting", Monthly Notices of the Royal Astronomical Society , 385 (4): 1998–2010, arXiv: 0801.0871 , Bibcode:2008MNRAS.385.1998K, doi: 10.1111/j.1365-2966.2008.12908.x , S2CID   17571531.
  7. ↑ "NGC 1851". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2020-04-10.
  8. ↑ "NASA/IPAC Extragalactic Database". Results for NGC 1851. Retrieved 2011-01-09.
  9. ↑ O'Meara, Stephen James (2016), Deep-Sky Companions: The Caldwell Objects, Cambridge University Press, p. 344, ISBN   9781107083974.
  10. 1 2 3 Carballo-Bello, Julio A.; et al. (February 2018), "Tails and streams around the Galactic globular clusters NGC 1851, NGC 1904, NGC 2298 and NGC 2808", Monthly Notices of the Royal Astronomical Society, 474 (1): 683–695, arXiv: 1710.08927 , Bibcode:2018MNRAS.474..683C, doi: 10.1093/mnras/stx2767 .
  11. ↑ Carballo-Bello, Julio A.; Martínez-Delgado, David; Navarrete, Camila; Catelan, Márcio; Muñoz, Ricardo R.; Antoja, Teresa; Sollima, Antonio (2017), "Tails and streams around the Galactic globular clusters NGC 1851, NGC 1904, NGC 2298 and NGC 2808", Monthly Notices of the Royal Astronomical Society, 474 (1): 683–695, arXiv: 1710.08927 , Bibcode:2018MNRAS.474..683C, doi: 10.1093/mnras/stx2767
  12. ↑ Ridolfi, A.; et al. (December 2019), "Upgraded Giant Metrewave Radio Telescope timing of NGC 1851A: a possible millisecond pulsar - neutron star system", Monthly Notices of the Royal Astronomical Society, 490 (3): 3860–3874, arXiv: 1909.06163 , Bibcode:2019MNRAS.490.3860R, doi: 10.1093/mnras/stz2645 , PMC   6859652 , PMID   31762495.
  13. ↑ Ewan D. Barr et al. A pulsar in a binary with a compact object in the mass gap between neutron stars and black holes. Science 2024; 383:275-279. doi : 10.1126/science.adg3005
  14. ↑ Ridolfi, A.; Freire, P. C. C.; Gautam, T.; Ransom, S. M.; Barr, E. D.; Buchner, S.; Burgay, M.; Abbate, F.; Venkatraman Krishnan, V.; Vleeschower, L.; Possenti, A.; Stappers, B. W.; Kramer, M.; Chen, W.; Padmanabh, P. V.; Champion, D. J.; Bailes, M.; Levin, L.; Keane, E. F.; Breton, R. P.; Bezuidenhout, M.; Grießmeier, J.-M.; Künkel, L.; Men, Y.; Camilo, F.; Geyer, M.; Hugo, B. V.; Jameson, A.; Parthasarathy, A.; Serylak, M. (2022), "TRAPUM discovery of 13 new pulsars in NGC 1851 using MeerKAT", Astronomy & Astrophysics, 664: A27, arXiv: 2203.12302 , Bibcode:2022A&A...664A..27R, doi:10.1051/0004-6361/202143006, S2CID   248208657
  15. ↑ Subramaniam, Annapurni; et al. (December 2017), "The Horizontal Branch Population of NGC 1851 as Revealed by the Ultraviolet Imaging Telescope (UVIT)", The Astronomical Journal, 154 (6): 233, arXiv: 1710.03730 , Bibcode:2017AJ....154..233S, doi: 10.3847/1538-3881/aa94c3 , S2CID   119207523, 233.
  16. ↑ Lim, Dongwook; et al. (January 2015), "Low-resolution Spectroscopy for the Globular Clusters with Signs of Supernova Enrichment: M22, NGC 1851, and NGC 288", The Astrophysical Journal Supplement, 216 (1): 13, arXiv: 1412.1832 , Bibcode:2015ApJS..216...19L, doi:10.1088/0067-0049/216/1/19, S2CID   119248182, 19.
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