| Abell 222 | |
|---|---|
| Observation data (EpochJ2000) | |
| Constellation(s) | Cetus |
| Right ascension | 01h 37m 27.4s[1] |
| Declination | −12° 58′ 45″[1] |
| Brightest member | LEDA 944643[2] |
| Richness class | 3[3] |
| Bautz–Morgan classification | II-III[3] |
| Velocity dispersion | 1,014 km/s[4] |
| Redshift | 0.2110[5] |
| Distance | 2.4 Gly (740 Mpc)[6] |
| ICM temperature | 3.77 ± 0.15 keV[4] |
| Other designations | |
| RXC J0137.4-1259[1] | |
Abell 222 is agalaxy cluster in theconstellation ofCetus. It holds thousands ofgalaxies together. It is located at a distance of 2.4 billion light-years fromEarth.[6]
Astronomers noticed an invisible string of matter was warpingspacetime between Abell 222 andAbell 223. Upon further examination by using images from the Japanese Subaru telescope, astronomers discovered that this "invisible matter" is in factdark matter. The astronomers usedgravitational lensing to detect the dark matter filaments.[7] The cluster is connected by a filament of dark matter toAbell 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 thecosmological standard model.[9] This means that the two bodies would form theAbell 222/Abell 223Supercluster as defined by theIAU.[10]
About 5% of the universe is estimated to be 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 a significant part of the missing baryonic matter is within the gas that bridges the two galaxy clusters. This was difficult to locate because the gas had avery 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 extremely distant gas with the latest high-powerinfrared andX-ray telescopes, within a section of the sky.[11]
