Eta Carinae
 The Homunculus Nebula, surrounding Eta Carinae, imaged by WFPC2 at red and near-ultraviolet wavelengths Credit: Jon Morse (University of Colorado) & NASA Hubble Space Telescope |
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| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Carina |
| Right ascension | 10h 45m 03.591s |
| Declination | −59° 41′ 04.26″ |
| Apparent magnitude (V) | −1.0 to ~7.6 |
| Characteristics | |
| Spectral type | variable + O |
| Apparent magnitude (U) | 6.37 |
| Apparent magnitude (B) | 6.82 |
| Apparent magnitude (R) | 4.90 |
| Apparent magnitude (J) | 3.39 |
| Apparent magnitude (H) | 2.51 |
| Apparent magnitude (K) | 0.94 |
| U−B color index | −0.45 |
| B−V color index | +0.61 |
| Variable type | LBV & binary |
| Astrometry | |
| Radial velocity (Rv) | −25.0 km/s |
| Proper motion (μ) |
RA: −7.6 mas/yr Dec.: 1.0 mas/yr |
| Distance | 7,500 ly (2,300pc) |
| Absolute magnitude (MV) | −8.6 (2012) |
| Details | |
| η Car A | |
| Mass | ~100-200 M☉ |
| Radius | 60-800 R☉ |
| Luminosity | 5,000,000 L☉ |
| Temperature | 9,400-35,200 K |
| Age | <3 Myr |
| η Car B | |
| Mass | 30-80 M☉ |
| Radius | 14.3-23.6 R☉ |
| Luminosity | <1,000,000 L☉ |
| Temperature | 37,200 K |
| Age | <3 Myr |
| Orbit | |
| Primary | η Car A |
| Companion | η Car B |
| Period (P) | 2022.7±1.3 days (5.54 yr) |
| Semi-major axis (a) | 15.4 AU |
| Eccentricity (e) | 0.9 |
| Inclination (i) | 130–145° |
| Periastron epoch (T) | 2009.03 |
| Other designations | |
| Database references | |
| SIMBAD | data |
Coordinates: 
10h 45m 03.591s, −59° 41′ 04.26″
Eta Carinae (abbreviated to η Carinae or η Car), formerly known as Eta Argus, is a stellar system containing at least two stars with a combined luminosity over five million times that of the Sun, located around 7500 light-years (2300 parsecs) distant in the constellation Carina. First recorded as a 4th-magnitude star, it brightened considerably over the period 1837 to 1856 in an event known as the Great Eruption. Eta Carinae became the second-brightest star in the sky between 11 and 14 March 1843 before fading well below naked eye visibility. It has brightened consistently since about 1940, peaking above magnitude 4.5 in 2014. Eta Carinae is circumpolar south of latitude 30°S, so it is never visible north of latitude 30°N.
The two main stars of the Eta Carinae system have an eccentric orbit with a period of 5.54 years. The primary is a peculiar star similar to a luminous blue variable (LBV) that was initially 150–250 M☉ of which it has lost at least 30 M☉ already, and is expected to explode as a supernova in the astronomically near future. This is the only star known to produce ultraviolet laser emission. The secondary star is hot and also highly luminous, probably of spectral class O, around 30–80 times as massive as the Sun. The system is heavily obscured by the Homunculus Nebula, material ejected from the primary during the Great Eruption. It is a member of the Trumpler 16 open cluster within the much larger Carina Nebula. Although unrelated to the star or Nebula, the weak Eta Carinids meteor shower has a radiant very close to Eta Carinae.
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