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NGC 2419

NGC 2419
NGC 2419 by HST[1]
Observation data (J2000 epoch)
ClassVII[2]
ConstellationLynx
Right ascension07h 38m 08.51s[3]
Declination+38° 52′ 54.9″[3]
Distance275 kly (from the Sun)
300 kly (from the GC) (84.2 kpc (Sun)
91.5 kpc (GC)[4])
Apparent magnitude (V)+9.06[3]
Apparent dimensions (V)6′
Physical characteristics
Mass9 x 10^5 M☉
Radius260 ly[5]
VHB20.45[4]
Metallicity = –2.14[6] dex
Estimated age12.3 Gyr[6]
Other designationsGCl 112,[3] Caldwell 25
See also: Globular cluster, List of globular clusters

NGC 2419 (also known as Caldwell 25) is a globular cluster in the constellation Lynx. It was discovered by William Herschel on December 31, 1788.[7] NGC 2419 is at a distance of about 300,000 light years from the Solar System and at the same distance from the Galactic Center.

NGC 2419 bears the nickname "the Intergalactic Wanderer," which was bestowed when it was erroneously thought not to be in orbit around the Milky Way. Its orbit takes it farther away from the galactic center than the Magellanic Clouds, but it can (with qualifications) be considered as part of the Milky Way. At this great distance it takes three billion years to make one trip around the galaxy.[8]

The cluster is dim in comparison to more famous globular clusters such as M13. Nonetheless, NGC 2419 is a 9th magnitude object and is readily viewed, in good sky conditions, with good quality telescopes as small as 102mm (four inches) in aperture. Intrinsically it is one of the brightest and most massive globular clusters of our galaxy, having an absolute magnitude of −9.42[4] and being 900,000 times more massive than the Sun.[9]

It was proposed that NGC 2419 could be, as Omega Centauri, the remnant of a dwarf spheroidal galaxy disrupted and accreted by the Milky Way.[10] However, that hypothesis has been disputed.[11]

Astronomer Leos Ondra has noted that NGC 2419 would be the "best and brightest" for any observers in the Andromeda Galaxy, looking for globular clusters in our galaxy since it lies outside the obscuring density of the main disk.[8] This is analogous to the way the cluster G1 can be seen orbiting outside of the Andromeda Galaxy from Earth.

It was found to be composed of two different populations, one being more helium-rich than the other, which does not fit the current model for globular cluster formation (which leads to a very homogeneous population in the cluster). This raises new questions on how this globular cluster was formed.[12]

References

  1. ^ "The two mysterious populations of NGC 2419". www.spacetelescope.org. Retrieved 25 February 2019.
  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.
  3. ^ a b c d "NGC 2419". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-11-17.
  4. ^ a b c Harris, W.E. (1996). "A Catalog of Parameters for Globular Clusters in the Milky Way". The Astronomical Journal. 112: 1487. Bibcode:1996AJ....112.1487H. doi:10.1086/118116.
  5. ^ distance × sin( diameter_angle / 2 ) = 260 ly. radius
  6. ^ a b Forbes, Duncan A.; Bridges, Terry (May 2010), "Accreted versus in situ Milky Way globular clusters", Monthly Notices of the Royal Astronomical Society, 404 (3): 1203–1214, arXiv:1001.4289, Bibcode:2010MNRAS.404.1203F, doi:10.1111/j.1365-2966.2010.16373.x, S2CID 51825384.
  7. ^ http://messier.seds.org/xtra/ngc/n2419.html NGC 4189 at SEDS
  8. ^ a b Ferris, Timothy. Seeing in the Dark. 2002. p. 244
  9. ^ Baumgardt, H.; Côté, P.; Hilker, M.; Rejkuba, M.; et al. (2009). "The velocity dispersion and mass-to-light ratio of the remote halo globular cluster NGC2419". Monthly Notices of the Royal Astronomical Society. 396 (4): 2051–2060. arXiv:0904.3329. Bibcode:2009MNRAS.396.2051B. doi:10.1111/j.1365-2966.2009.14932.x. S2CID 7956224.
  10. ^ van den Bergh, Sidney; Mackey, A. D. (2004). "Globular clusters and the formation of the outer Galactic halo". Monthly Notices of the Royal Astronomical Society. 354 (3): 713–719. arXiv:astro-ph/0407346. Bibcode:2004MNRAS.354..713V. doi:10.1111/j.1365-2966.2004.08228.x. S2CID 15407602.
  11. ^ RIPEPI V.; CLEMENTINI G.; DI CRISCIENZO M.; GRECO C.; et al. (2007). "On the remote galactic globular cluster NGC 2419". The Astrophysical Journal. 667 (1): L61–L64. arXiv:0705.0966. Bibcode:2007ApJ...667L..61R. doi:10.1086/522000. S2CID 15186576.
  12. ^ "The two mysterious populations of NGC 2419". www.spacetelescope.org. February 2019. Retrieved 2021-02-25.


Quelle: https://en.wikipedia.org/wiki/Caldwell_25