Eta Carinae
Eta Carinae is a star in the constellation Carina, magnitude 4.3.
The star that briefly outshone all but Sirius, then vanished — a doomed giant waiting to explode.
On the evening of 16 December 1837, John Herschel, observing from South Africa, was astonished to see a star in the ship Argo outshining Rigel. It was Eta Carinae, and its ‘Great Eruption’ had begun. By March 1843 only Sirius outshone it. Then, over the following decades, it faded from naked-eye view, hidden by dust from its own outburst.
The gas it threw off now forms the Homunculus, a two-lobed nebula wrapped around the star. At its heart are at least two stars on a 5.54-year orbit. The primary was born with perhaps 150 to 250 times the Sun’s mass and has already lost at least 30; its companion is a hot star of 30 to 80 solar masses. Together they shine over five million times as brightly as the Sun.
Astronomers expect the primary to explode as a supernova — soon, by the standards of stars. Until then it holds a strange record: it is the only star known to produce ultraviolet laser light.
Eta Carinae is 7,500 light-years away: the light we see from it set off around 5480 BC, around the time the first towns were growing in the Fertile Crescent.
Did you know?
- Old Woman Crow. The Boorong people of north-western Victoria told of a reddish star, Collowgullouric War, wife of the Crow (Canopus). In 2010 astronomers showed this was Eta Carinae during its 1840s eruption.
- “Very like Arcturus”. In 1843 the Reverend W. S. Mackay wrote from Calcutta that the star had become ‘fully as bright as Canopus, and in colour and size very like Arcturus’.
- Coming back. After sinking out of sight, Eta Carinae has slowly brightened since about 1940. By 2014 it was again a 4th-magnitude star, visible to the naked eye.
An orange-tinted 4th-magnitude star at the heart of the Carina Nebula, easy to see with the naked eye from dark southern skies. At high power a small telescope shows it as a tiny orange blob rather than a point — the cloud it blew off in the 1840s.
When and where to see it
It is best placed in the evening sky around April, when it crosses the meridian at about 10 pm local time (around midnight in February). It can be seen from everywhere south of 30°N and never sets south of 30°S.
At its highest it stands below the horizon from 50°N, below the horizon from 35°N, 30° up from the equator, 65° up from 35°S.
Facts
- Type
- Star
- Constellation
- Carina
- Designations
- Eta Car, η Car, HR 4210, HD 93308
- Magnitude
- 4.3
- Position
- RA 10h 45.1m, Dec −59° 41′ (J2000)
- Spectral type
- LBV
- Colour
- yellow (B−V 0.55)
- Distance
- 7,500 light-years
- Discovered
- Edmond Halley, 1677, First firm record; its Great Eruption began in 1837
Open AstroPilot to see when Eta Carinae is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.