Abell 222

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Abell 222
Observation data (Epoch J2000)
Right ascension 01h 37m 27.4s[1]
Declination−12° 58′ 45″[1]
Brightest memberLEDA 944643[2]
Richness class3[3]
Bautz–Morgan classificationII-III[3]
Velocity dispersion1014 km/s[4]
2.4 Mly (0.74 Mpc)[6]
ICM temperature3.77 ± 0.15 keV[4]
Other designations
RXC J0137.4-1259[1]
See also: Galaxy group, Galaxy cluster, List of galaxy groups and clusters

Abell 222 is a galaxy cluster in the constellation of Cetus. It holds thousands of galaxies together. It is located at a distance of 2.4 billion light-years from Earth.[6]

Discovery of dark matter[edit]

Astronomers noticed an invisible string of matter was warping spacetime between Abell 222 and Abell 223. Upon further examination by using images from the Japanese Subaru telescope, astronomers discovered that this "invisible matter" is in fact dark matter. The astronomers used gravitational lensing to detect the dark matter filaments.[7] The cluster is connected by a filament of dark matter to Abell 223 that is permeated by hot X-ray emitting gas.[8] Further research shows that this filament only contains about 20 percent of normal matter, the rest is assumed to be dark matter. This is seen to be in good agreement with the cosmological standard model.[9]

Baryonic matter[edit]

5% of the universe is made up of baryonic or ordinary matter which contains protons and neutrons, also known as baryons, and electrons. Baryons and electrons are the foundation for atoms. Astronomers have not been able to locate the full 5% of baryonic matter within other galaxies, stars or gases. After observing gas that connects Abell 222 and Abell 223, scientists believe that the missing baryonic matter is within the gas that bridges the two galaxy clusters. This was difficult to locate due to the fact that the gas had a very low density, which made it hard to detect. This discovery was made possible because of Abell 222’s location. It is within Earth’s line of sight, so scientists were able to see a strong concentration of this gas within a section of the sky.[10]

See also[edit]


  1. ^ a b c "ACO 222". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 24 November 2017.
  2. ^ "2MASX J01373406-1259288". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 24 November 2017.
  3. ^ a b Abell, George O.; Corwin, Harold G., Jr.; Olowin, Ronald P. (May 1989). "A catalog of rich clusters of galaxies" (PDF). Astrophysical Journal Supplement Series. 70 (May 1989): 1–138. doi:10.1086/191333. ISSN 0067-0049.
  4. ^ a b Durret, F; Laganá, T. F; Adami, C; Bertin, E (2010). "The clusters Abell 222 and Abell 223: A multi-wavelength view". Astronomy and Astrophysics. 517: A94. arXiv:1005.3295. Bibcode:2010A&A...517A..94D. doi:10.1051/0004-6361/201014566.
  5. ^ "NED results for object ABELL 0222". National Aeronautics and Space Administration / Infrared Processing and Analysis Center. Retrieved 24 November 2017.
  6. ^ a b Pete Spotts (5 July 2012). "Cosmic scaffolding uncovered? Scientists find thread of dark matter". The Christian Science Monitor. Christian Science Publishing Society. Retrieved 14 July 2012.
  7. ^ "Dark Matter Filaments Detected In Abell 222 And Abel 223 Supercluster". Science 2.0. 27 August 2014. Retrieved 16 October 2017.
  8. ^ "ID: SEMHZOZXUFF: Galaxy clusters Abell 222 and Abell 223". esa. Retrieved 24 September 2012.
  9. ^ "Eine Brücke aus dunkler Materie zwischen zwei Galaxienhaufen" (in German). Neue Zürcher Zeitung. 17 July 2012. Archived from the original on 17 July 2012. Retrieved 24 September 2012.
  10. ^ "Do Abell 222 And Abell 223 Contain The Universe's 'Missing' Baryonic Matter?". Science 2.0. 27 August 2014. Retrieved 16 October 2017.