Crater 2 Dwarf

Last updated
Crater 2
Observation data (J2000.0 epoch)
Constellation Crater [1]
Right ascension 11h 49m 14.400s
177.310°±0.03° [1]
Declination −18° 24′ 46.80″
−18.413°±0.03° [1]
Heliocentric radial velocity 88 km/s [2]
Galactocentric velocity-74 km/s [2]
Distance 383,000  ly (117.5  kpc) [1]
Apparent magnitude  (V)12.15 mag [1]
Absolute magnitude  (V)−8.2±0.1 mag [1]
Characteristics
Type dSph [1]
Apparent size  (V)62.4′ (rh=31.2′ ± 2.5′) [1]
6,950  ly (2,132  pc)
rh=1066pc ± 84pc [1]
Notable features4th largest satellite
galaxy to Milky Way [1]

Crater 2 is a low-surface-brightness dwarf satellite galaxy of the Milky Way, [1] located approximately 380,000 ly from Earth. Its discovery in 2016 revealed significant gaps in astronomers' understanding of galaxies possessing relatively small half-light diameters and suggested the possibility of many undiscovered dwarf galaxies orbiting the Milky Way. [3] Crater 2 was identified in imaging data from the VST ATLAS survey. [3]

Contents

The galaxy has a half-light radius of ~1100  pc , making it the fourth largest satellite of the Milky Way. [1] It has an angular size about double of that of the moon. [3] [4] Despite the large size, Crater 2 has a surprisingly low surface brightness, implying that it is not very massive. [5] In addition, its velocity dispersion is also low, suggesting it may have formed in a halo of low dark matter density. [6] Alternatively, it may be a result of tidal interactions with it and larger galaxies, such as the Milky Way and the Large Magellanic Cloud, [5] but according to some simulations, this would not explain the relatively large size. [6] This unusually low velocity dispersion was predicted using Modified Newtonian Dynamics, an alternative to the dark matter hypothesis. [7] This prediction was later confirmed by observations. [8]

See also

Related Research Articles

<span class="mw-page-title-main">Local Group</span> Group of galaxies that includes the Milky Way

The Local Group is the galaxy group that includes the Milky Way, where Earth is located. It has a total diameter of roughly 3 megaparsecs (10 million light-years; 9×1019 kilometres), and a total mass of the order of 2×1012 solar masses (4×1042 kg). It consists of two collections of galaxies in a "dumbbell" shape; the Milky Way and its satellites form one lobe, and the Andromeda Galaxy and its satellites constitute the other. The two collections are separated by about 800 kiloparsecs (3×10^6 ly; 2×1019 km) and are moving toward one another with a velocity of 123 km/s. The group itself is a part of the larger Virgo Supercluster, which may be a part of the Laniakea Supercluster. The exact number of galaxies in the Local Group is unknown as some are occluded by the Milky Way; however, at least 80 members are known, most of which are dwarf galaxies.

<span class="mw-page-title-main">Hydra–Centaurus Supercluster</span> Closest neighboring galaxy supercluster

The Hydra–Centaurus Supercluster, or the Hydra and Centaurus Superclusters, was a previously defined supercluster in two parts, which prior to the identification of Laniakea Supercluster in 2014 is the closest neighbour of the former Virgo Supercluster. Its center is located about 39 Mpc (127 Mly) away, with it extending to a maximum distance of around 69 Mpc (225 Mly).

<span class="mw-page-title-main">Dwarf spheroidal galaxy</span> Low-luminosity galaxy of old stars & little dust

A dwarf spheroidal galaxy (dSph) is a term in astronomy applied to small, low-luminosity galaxies with very little dust and an older stellar population. They are found in the Local Group as companions to the Milky Way and as systems that are companions to the Andromeda Galaxy (M31). While similar to dwarf elliptical galaxies in appearance and properties such as little to no gas or dust or recent star formation, they are approximately spheroidal in shape and generally have lower luminosity.

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

The Fornax Dwarf Spheroidal is an elliptical dwarf 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">Satellite galaxy</span> Galaxy that orbits a larger galaxy due to gravitational attraction

A satellite galaxy is a smaller companion galaxy that travels on bound orbits within the gravitational potential of a more massive and luminous host galaxy. Satellite galaxies and their constituents are bound to their host galaxy, in the same way that planets within our own solar system are gravitationally bound to the Sun. While most satellite galaxies are dwarf galaxies, satellite galaxies of large galaxy clusters can be much more massive. The Milky Way is orbited by about fifty satellite galaxies, the largest of which is the Large Magellanic Cloud.

The Milky Way has several smaller galaxies gravitationally bound to it, as part of the Milky Way subgroup, which is part of the local galaxy cluster, the Local Group.

<span class="mw-page-title-main">Boötes I</span> Galaxy in the constellation Boötes

The Boötes Dwarf Galaxy is a galaxy discovered in 2006, which appears faint, with a luminosity of 100,000 L☉ and an absolute magnitude of –5.8. It lies about 197,000 light-years away in the constellation Boötes. This dwarf spheroidal galaxy appears to be tidally disrupted by the Milky Way Galaxy, which it orbits, and has two stellar tails that cross over to form a cross. Tidally disrupted galaxies usually only form one tail. The galaxy appears to be significantly elongated, with an ellipticity of ε = 0.68 ± 0.15.

<span class="mw-page-title-main">Stellar kinematics</span> Study of the movement of stars

In astronomy, stellar kinematics is the observational study or measurement of the kinematics or motions of stars through space.

<span class="mw-page-title-main">Hercules (dwarf galaxy)</span> Dwarf spheroidal galaxy in the constellation Hercules

Hercules, or Her, is a dwarf spheroidal galaxy situated in the Hercules constellation and discovered in 2006 in data obtained by the Sloan Digital Sky Survey. The galaxy is located at a distance of about 140 kpc from the Sun and moves away from the Sun with a velocity of about 45 km/s. It is classified as a dwarf spheroidal galaxy (dSph). It has a noticeably elongated shape with a half-light radius of about 350 pc. This elongation may be caused by tidal forces acting from the Milky Way galaxy, meaning that Her is being tidally disrupted now. Her also shows some gradient of velocities across the galaxy's body and is embedded into a faint stellar stream, which also points towards its ongoing tidal disruption.

Pisces II is a dwarf spheroidal galaxy situated in the Pisces constellation and discovered in 2010 in the data obtained by the Sloan Digital Sky Survey. The galaxy is located at the distance of about 180 kpc (kiloparsecs) from the Sun. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an elongated shape with the half-light radius of about 60 pc and ratio of the axis of about 5:3.

<span class="mw-page-title-main">NGC 5286</span> Globular cluster in the constellation Centaurus

NGC 5286 is a globular cluster of stars located some 35,900 light years away in the constellation Centaurus. At this distance, the light from the cluster has undergone reddening from interstellar gas and dust equal to E(B – V) = 0.24 magnitude in the UBV photometric system. The cluster lies 4 arc-minutes north of the naked-eye star M Centauri. It was discovered by Scottish astronomer James Dunlop, active in Australia, and listed in his 1827 catalog.

<span class="mw-page-title-main">Laevens 1</span> Galaxy in the constellation Crater

Laevens 1 is a faint globular cluster in the constellation Crater that was discovered in 2014. It is also known as Crater, the Crater cluster and PSO J174.0675-10.8774.

Reticulum II is a dwarf galaxy in the Local Group. Reticulum II was discovered in 2015 by analysing images from the Dark Energy Survey. It is a satellite of the Magellanic Clouds and was probably captured relatively recently. Like other dwarf spheroidal galaxies, its stellar population is old: the galaxy was quenched before 11.5 billion years ago.

<span class="mw-page-title-main">Dragonfly 44</span> Galaxy in constellation Coma Berenices

Dragonfly 44 is an ultra diffuse galaxy in the Coma Cluster. This galaxy is well-known because observations of the velocity dispersion in 2016 suggested a mass of about one trillion solar masses, about the same as the Milky Way. This mass was consistent with a count of about 90 and 70 globular clusters observed around Dragonfly 44 in two different studies.

<span class="mw-page-title-main">NGC 4660</span> Galaxy in the constellation Virgo

NGC 4660 is an elliptical galaxy located about 63 million light-years away in the constellation Virgo. The galaxy was discovered by astronomer William Herschel on March 15, 1784 and is a member of the Virgo 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">Antlia II</span> Low surface-brightness dwarf satellite galaxy of the Milky Way

Antlia II is a low-surface-brightness dwarf satellite galaxy of the Milky Way at a galactic latitude of 11.2°. It spans 1.26° in the sky just southeast of Epsilon Antliae. The galaxy is similar in size to the Large Magellanic Cloud, despite being 1/10,000 as bright. Antlia II has the lowest surface brightness of any galaxy discovered and is ~ 100 times more diffuse than any known ultra diffuse galaxy. The large size of the galaxy suggests that it is currently being tidally disrupted, and is in the process of becoming a stellar stream. The southeast side of Antlia II is farther away than the northwest side, likely due to the tidal disruption. It was discovered using data from the European Space Agency's Gaia spacecraft in November 2018.

Price-Whelan 1 is a young stellar association or disrupting star cluster with low metallicity and extragalactic origin, more specifically the leading arm of the Magellanic gas stream originating in the Magellanic Clouds. Price-Whelan 1 was discovered by Adrian Price-Whelan using Gaia data and additional cluster members were identified using DECam data. The star cluster contains less than a thousand stars. The existence of Price-Whelan 1 suggests that the stream of gas extending from the Magellanic Clouds to our Milky Way is about half as far from the Milky Way as previously thought.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 Torrealba, G.; Koposov, S. E.; Belokurov, V.; Irwin, M. (2016). "The feeble giant. Discovery of a large and diffuse Milky Way dwarf galaxy in the constellation of Crater". Monthly Notices of the Royal Astronomical Society. 459 (3): 2370–2378. arXiv: 1601.07178 . Bibcode:2016MNRAS.459.2370T. doi: 10.1093/mnras/stw733 .
  2. 1 2 Kashibadze, Olga G.; Karachentsev, Igor D. (2018). "Cosmic flow around local massive galaxies". Astronomy & Astrophysics. 609: A11. arXiv: 1709.09420 . Bibcode:2018A&A...609A..11K. doi:10.1051/0004-6361/201731645. S2CID   55486336.
  3. 1 2 3 Croswell, Ken (14 April 2016). "Never-before-seen galaxy spotted orbiting the Milky Way". New Scientist . Retrieved 14 April 2016.
  4. ↑ Howard, Jacqueline (2016-04-16). "Elusive Dwarf Galaxy Found Orbiting Our Milky Way". Huffington Post. Retrieved 2016-04-19.
  5. 1 2 Ji, Alexander P.; Koposov, Sergey E.; Li, Ting S.; Erkal, Denis; Pace, Andrew B.; Simon, Joshua D.; Belokurov, Vasily; Cullinane, Lara R.; Da Costa, Gary S.; Kuehn, Kyler; Lewis, Geraint F.; MacKey, Dougal; Shipp, Nora; Simpson, Jeffrey D.; Zucker, Daniel B.; Hansen, Terese T.; Bland-Hawthorn, Joss; S5 Collaboration (2021). "Kinematics of Antlia 2 and Crater 2 from the Southern Stellar Stream Spectroscopic Survey (S 5)". The Astrophysical Journal. 921 (1): 32. arXiv: 2106.12656 . Bibcode:2021ApJ...921...32J. doi: 10.3847/1538-4357/ac1869 . S2CID   235624056.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  6. 1 2 Borukhovetskaya, Alexandra; Navarro, Julio F.; Errani, Raphaël; Fattahi, Azadeh (2022). "Galactic tides and the Crater II dwarf spheroidal: A challenge to LCDM?". Monthly Notices of the Royal Astronomical Society. 512 (4): 5247–5257. arXiv: 2112.01540 . Bibcode:2022MNRAS.512.5247B. doi: 10.1093/mnras/stac653 .
  7. ↑ McGaugh, Stacy S. (2016-11-14). "MOND Prediction for the Velocity Dispersion of the 'Feeble Giant' Crater II". The Astrophysical Journal. 832 (1): L8. arXiv: 1610.06189 . Bibcode:2016ApJ...832L...8M. doi: 10.3847/2041-8205/832/1/L8 . ISSN   2041-8213. S2CID   51764960.
  8. ↑ Caldwell, Nelson; Walker, Matthew G.; Mateo, Mario; Olszewski, Edward W.; Koposov, Sergey; Belokurov, Vasily; Torrealba, Gabriel; Geringer-Sameth, Alex; Johnson, Christian I. (2017-04-10). "Crater 2: An Extremely Cold Dark Matter Halo". The Astrophysical Journal. 839 (1): 20. arXiv: 1612.06398 . Bibcode:2017ApJ...839...20C. doi: 10.3847/1538-4357/aa688e . hdl: 10150/623952 . ISSN   1538-4357. S2CID   119422981.


This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.