NGC 7492

Last updated
NGC 7492
NGC 7492 legacy dr10.jpg
NGC 7492 with legacy surveys
Observation data (J2000 epoch)
Class XII
Constellation Aquarius
Right ascension 23h 08m 26.7s [1]
Declination −15° 36 39 [1]
Distance 24,500  kpc (80,000×10^3  ly) [2]
Apparent magnitude (V)11.2
Apparent dimensions (V)4.2
Physical characteristics
Absolute magnitude 0.38±0.04 [3]
Metallicity  = -1.69 [4] dex
Estimated age12 Gyr [2]
Other designationsGCl 125, MWSC 3705
See also: Globular cluster, List of globular clusters

NGC 7492 is a globular cluster [1] in the constellation Aquarius. It was discovered by the astronomer William Herschel on September 20, 1786. [5] It resides in the outskirts of the Milky Way, about 80,000 light-years away, more than twice the distance between the Sun and the center of the galaxy, and is a benchmark member of the outer galactic halo. [6] The cluster is immersed in, but does not kinematically belong to, the Sagittarius Stream. [7]

NGC 7492 possess a tidal tail 3.5 degrees long, [8] embedded into an over-density of stars which may be the remnants of a disrupted dwarf galaxy. [9] The shape of the cluster is flattened rather than spherical, likely due to dynamical interaction with the Milky Way. [10]

Related Research Articles

<span class="mw-page-title-main">Globular cluster</span> Spherical collection of stars

A globular cluster is a spheroidal conglomeration of stars that is bound together by gravity, with a higher concentration of stars towards its center. It can contain anywhere from tens of thousands to many millions of member stars, all orbiting in a stable, compact formation. Globular clusters are similar in form to dwarf spheroidal galaxies, and the distinction between the two is not always clear. Their name is derived from Latin globulus. Globular clusters are occasionally known simply as "globulars".

<span class="mw-page-title-main">Sagittarius Dwarf Spheroidal Galaxy</span> Satellite galaxy of the Milky Way

The Sagittarius Dwarf Spheroidal Galaxy (Sgr dSph), also known as the Sagittarius Dwarf Elliptical Galaxy, is an elliptical loop-shaped satellite galaxy of the Milky Way. It contains four globular clusters in its main body, with the brightest of them—NGC 6715 (M54)—being known well before the discovery of the galaxy itself in 1994. Sgr dSph is roughly 10,000 light-years in diameter, and is currently about 70,000 light-years from Earth, travelling in a polar orbit at a distance of about 50,000 light-years from the core of the Milky Way. In its looping, spiraling path, it has passed through the plane of the Milky Way several times in the past. In 2018 the Gaia project of the European Space Agency showed that Sgr dSph had caused perturbations in a set of stars near the Milky Way's core, causing unexpected rippling movements of the stars triggered when it moved through the Milky Way between 300 and 900 million years ago.

<span class="mw-page-title-main">Messier 2</span> Globular cluster in the constellation Aquarius

Messier 2 or M2 is a globular cluster in the constellation Aquarius, five degrees north of the star Beta Aquarii. It was discovered by Jean-Dominique Maraldi in 1746, and is one of the largest known globular clusters.

<span class="mw-page-title-main">Messier 54</span> Globular cluster in Sagittarius

Messier 54 is a globular cluster in the constellation Sagittarius. It was discovered by Charles Messier in 1778 and then included in his catalog of comet-like objects.

<span class="mw-page-title-main">Messier 53</span> Globular cluster in the constellation Coma Berenices

Messier 53 is a globular cluster in the Coma Berenices constellation. It was discovered by Johann Elert Bode in 1775. M53 is one of the more outlying globular clusters, being about 60,000 light-years (18.4 kpc) light-years away from the Galactic Center, and almost the same distance from the Solar System. The cluster has a core radius (rc) of 2.18 pc, a half-light radius (rh) of 5.84 pc, and a tidal radius (rtr) of 239.9 pc.

<span class="mw-page-title-main">Dwarf galaxy</span> Small galaxy composed of up to several billion stars

A dwarf galaxy is a small galaxy composed of about 1000 up to several billion stars, as compared to the Milky Way's 200–400 billion stars. The Large Magellanic Cloud, which closely orbits the Milky Way and contains over 30 billion stars, is sometimes classified as a dwarf galaxy; others consider it a full-fledged galaxy. Dwarf galaxies' formation and activity are thought to be heavily influenced by interactions with larger galaxies. Astronomers identify numerous types of dwarf galaxies, based on their shape and composition.

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

Messier 79 is a globular cluster in the southern constellation Lepus. It was discovered by Pierre Méchain in 1780 and is about 42,000 light-years away from Earth and 60,000 light years from the Galactic Center.

The Canis Major Overdensity or Canis Major Dwarf Galaxy is a disputed dwarf irregular galaxy in the Local Group, located in the same part of the sky as the constellation Canis Major.

<span class="mw-page-title-main">Fornax Dwarf</span> Dwarf galaxy in the constellation Fornax

The Fornax Dwarf Spheroidal is a dwarf elliptical galaxy in the constellation Fornax that was discovered in 1938 by Harlow Shapley. He discovered it while he was in South Africa on photographic plates taken by the 24 inch (61 cm) Bruce refractor at Boyden Observatory, shortly after he discovered the Sculptor Dwarf Galaxy.

<span class="mw-page-title-main">Palomar 1</span> Globular cluster in the constellation Cepheus

Palomar 1 is a globular cluster part of the Palomar group in the constellation Cepheus in the halo possibly in the Outer Arm of the Milky Way galaxy. First discovered by George O. Abell in 1954 on the Palomar Survey Sky plates, it was catalogued as a globular cluster. At 6.3 to 8 Gyr, it is a very young cluster when compared to the other globular clusters in the Milky Way. It is a relatively metal-poor globular with [Fe/H] = −0.60. It is likely that Palomar 1 has a similar evolutionary history to the Sagittarius dwarf companion globular Terzan 7, that is, it may have once been associated with a dwarf spheroidal galaxy that was later destroyed by tidal forces.

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

NGC 2808 is a globular cluster in the constellation Carina. The cluster currently belongs to the Milky Way, although it was likely stolen from a dwarf galaxy that collided with the Milky Way. NGC 2808 is one of our home galaxy's most massive clusters, containing more than a million stars. It is estimated to be 12.5-billion years old.

<span class="mw-page-title-main">NGC 1851</span> Globular cluster in the constellation Columba

NGC 1851 is a relatively massive 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. It is located 39.5 kilolight-years from the Sun, and 54.1 kilolight-years from the Galactic Center. The cluster is following a highly eccentric orbit through the galaxy, with an eccentricity of about 0.7.

<span class="mw-page-title-main">Terzan 7</span>

Terzan 7 is a sparse and young globular cluster that is believed to have originated in the Sagittarius Dwarf Spheroidal Galaxy and is physically associated with it. It is relatively metal rich with [Fe/H] = -0.6 and an estimated age of 7.5 Gyr. Terzan 7 has low levels of nickel which supports its membership in the Sag DEG system since it has a similar chemical signature. It has a rich population of blue stragglers that are strongly concentrated toward the center of Terzan 7. It has an average luminosity distribution of Mv = -5.05. It has a half-light radius (Rh) of 6.5pc.

In astronomy, the Sagittarius Stream is a long, complex structure made of stars that wrap around the Milky Way galaxy in an orbit that nearly crosses the galactic poles. It consists of tidally stripped stars from the Sagittarius Dwarf Elliptical Galaxy, resulting from the process of merging with the Milky Way over a period of billions of years.

<span class="mw-page-title-main">NGC 4147</span> Globular cluster in the constellation Coma Berenices

NGC 4147 is the New General Catalogue identifier for a globular cluster of stars in the northern constellation of Coma Berenices. It was discovered by English astronomer William Herschel on March 14, 1784, who described it as "very bright, pretty large, gradually brighter in the middle". With an apparent visual magnitude of 10.7, it is located around 60,000 light years away from the Sun at a relatively high galactic latitude of 77.2°.

<span class="mw-page-title-main">NGC 5053</span> Globular cluster in the constellation Coma Berenices

NGC 5053 is the New General Catalogue designation for a globular cluster in the northern constellation of Coma Berenices. It was discovered by German-British astronomer William Herschel on March 14, 1784 and cataloged as VI-7. In his abbreviated notation, he described it as, "an extremely faint cluster of extremely small stars with resolvable nebula 8 or 10′ diameter, verified by a power of 240, beyond doubt". Danish-Irish astronomer John Louis Emil Dreyer reported in 1888 that the cluster appeared, "very faint, pretty large, irregular round shape, growing very gradually brighter at the middle".

<span class="mw-page-title-main">NGC 3311</span> Galaxy in the constellation Hydra

NGC 3311 is a super-giant elliptical galaxy located about 190 million light-years away in the constellation Hydra. The galaxy was discovered by astronomer John Herschel on March 30, 1835. NGC 3311 is the brightest member of the Hydra Cluster and forms a pair with NGC 3309 which along with NGC 3311, dominate the central region of the Hydra Cluster.

<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.

<span class="mw-page-title-main">Palomar globular clusters</span> Faint globular clusters in the Milky Way galaxy

The Palomar globular clusters are some of the faintest of all globular clusters in the Milky Way galaxy, and been discovered in the 1950s on the survey plates of the first Palomar Observatory Sky Survey (POSS). In total there are 15 Palomar globular clusters, which include Palomar 1, Palomar 2, Palomar 3, Palomar 4, Palomar 5, Palomar 6, Palomar 7, Palomar 8, Palomar 9, Palomar 10, Palomar 11, Palomar 12, Palomar 13, Palomar 14, and Palomar 15. Some Palomar Globulars, like Palomar 6, Palomar 7, Palomar 9, Palomar 10 and Palomar 11 are clusters of average size located nearby, yet obscured in our line of sight by dust. Other Palomar globulars, like Palomar 3, Palomar 4 and Palomar 14 are giants located in the far outer halo of the Milky Way. Some even originated from a different galaxy, such as Palomar 12 from the Sagittarius Dwarf Spheroidal Galaxy, which is now known as a satellite of the Milky Way. Observation of different Palomar globulars greatly varies in the degree of difficulty depending on the cluster. Some are small and compact, others are very sparse, to the point where they may be hard to distinguish from foreground stars.

References

  1. 1 2 3 "NGC 7492". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2021-09-30.
  2. 1 2 Ultraviolet Imaging Telescope (UVIT) observation of the Galactic Globular Cluster NGC 7492
  3. Variable stars in the globular cluster NGC 7492, New discoveries and physical parameter determination
  4. ULTRAVIOLET PROPERTIES OF GALACTIC GLOBULAR CLUSTERS WITH GALEX. II. INTEGRATED COLORS
  5. Seligman, Courtney. "New General Catalogue objects: NGC 7450 - 7499". cseligman.com. Retrieved 2021-10-02.
  6. Koch, Andreas; Xu, Siyi; Rich, R. Michael (2019), "Chemical composition of the outer halo globular cluster Palomar 15", Astronomy & Astrophysics, 627: A70, arXiv: 1907.02071 , Bibcode:2019A&A...627A..70K, doi:10.1051/0004-6361/201935467, S2CID   195798995
  7. The globular cluster NGC 7492 and the Sagittarius tidal stream: together but unmixed
  8. Navarrete, C.; Belokurov, V.; Koposov, S. E. (2017), "The Discovery of Tidal Tails around the Globular Cluster NGC 7492 with Pan-STARRS1", The Astrophysical Journal, 841 (2): L23, arXiv: 1705.04324 , Bibcode:2017ApJ...841L..23N, doi: 10.3847/2041-8213/aa72e1 , S2CID   59384819
  9. Sollima, A.; Martínez Delgado, D.; Muñoz, R. R.; Carballo-Bello, J. A.; Valls-Gabaud, D.; Grebel, E. K.; Santana, F. A.; Côté, P.; Djorgovski, S. G. (2018), "A survey for dwarf galaxy remnants around 14 globular clusters in the outer halo", Monthly Notices of the Royal Astronomical Society, 476 (4): 4814–4829, arXiv: 1802.09255 , doi: 10.1093/mnras/sty539
  10. MASS SEGREGATION AND TIDAL TAILS OF THE GLOBULAR CLUSTER NGC 7492