Alcyoneus (galaxy)
Alcyoneus is a low-excitation, Fanaroff–Riley class II radio galaxy located 3.5 billion light-years (1.1 gigaparsecs) from Earth, corresponding to the galaxy SDSS J081421.68+522410.0. It is located in the constellation Lynx and it was discovered in Low-Frequency Array (LOFAR) data by a team of astronomers led by Martijn Oei. It has the largest extent of any radio galaxy identified, with lobed structures spanning 5 megaparsecs (16 million light-years) across, described by its discoverers as the "largest known structure of galactic origin." For comparison, another similarly sized giant radio galaxy is 3C 236, with lobes 15 million light-years across.
| SDSS J081421.68+522410.0 | |
|---|---|
Composite image of Alcyoneus in LOFAR radio data at 144 MHz (orange) and WISE infrared data at 3.4 micron (blue) | |
| Observation data (J2000.0 epoch) | |
| Constellation | Lynx |
| Right ascension | 08h 14m 21.68s |
| Declination | +52° 24′ 10.08″ |
| Redshift | 0.24674±0.00006 |
| Heliocentric radial velocity | 73,969.90±17.69 km/s |
| Galactocentric velocity | 74,013±18 km/s |
| Distance | 3.5 billion light-years (1.1 Gpc) |
| Apparent magnitude (V) | 17.16 |
| Characteristics | |
| Type | E (purported with 89% chance) |
| Mass | 2.4×1011 M☉ |
| Size | 242,700 ly (74.40 kpc) (diameter; 25.0 r-mag/arcsec2) |
| Notable features | Giant radio galaxy |
| Other designations | |
| Alcyoneus, 2MASS J08142169+5224103, WISEA J081421.70+522410.0 | |
References: | |
Aside from the size of its radio emissions, the central galaxy is otherwise of ordinary radio luminosity, stellar mass, and supermassive black hole mass. It is a standalone galaxy with an isophotal diameter at 25.0 r-mag/arcsec2 of about 242,700 light-years (74.40 kpc), with the nearest cluster located 11 million light years away from it. The galaxy was named after the giant Alcyoneus from Greek mythology.