Eta Carinae, our Neighboring Superstars

eta-carinae-our-neighboring-superstars

Eta Carinae, formerly known as Eta Argus, a stellar system containing at least two stars with a combined luminosity greater than five million times that of the Sun.

What is Eta Carinae?

Eta Carinae is located around 7,500 light-years (2,300 parsecs) distant in the constellation Carina. Previously a 4th-magnitude star, it brightened in 1837 to become brighter than Rigel marking the start of the Great Eruption. It became the second-brightest star in the sky between 11 and 14 March 1843 before fading well below naked eye visibility after 1856. In a smaller eruption, it reached 6th magnitude in 1892 before fading again. It has brightened consistently since about 1940, becoming brighter than magnitude 4.5 by 2014. Eta Carinae is circumpolar south of latitude 30°S, so it is never visible north of about latitude 30°N.

Composition

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 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.3

Visibility

As a 4th-magnitude star, Eta Carinae is comfortably visible to the naked eye in all but the most light-polluted skies in inner city areas according to the Bortle scale. Its brightness has varied over a wide range, from the second-brightest star in the sky at one point in the 19th century to well below naked eye visibility. Its location at around 60°S in the far Southern Celestial Hemisphere means it cannot be seen by observers in Europe and much of North America.

Image: NASA / JPL-Caltech
Text: Wikipedia contributors. “Eta Carinae.” Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 2 Aug. 2017. Web. 2 Aug. 2017

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