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Eta Carinae

Eta Carinae in Context

B/W HST of Eta Carinae Superposition of two optical images taken 17 months apart. Black: Apr '94; White: Sep '95
Photo: NASA/HST/J. Morse/K. Davidson
Eta Carinae is one of the most enigmatic and intriguing objects in our galaxy. Between 1837 and 1856 it increased dramatically in brightness to become the brightest star in the sky except for Sirius, even though it is 7,500 light years away, more than eight hundred times the distance to Sirius.

This "Great Eruption," as it is called, is thought to have been caused by internal radiation pressure in the massive star that somehow triggered an instability, or by interaction with a nearby companion star. After the Great Eruption, Eta Carinae faded to become a dim star, invisible to the naked eye. Since 1940, it has begun to brighten again, becoming visible to the naked eye.

Modern day observations of Eta Carinae have shown it to be the most luminous object known in our galaxy. It radiates at the rate of several million times that of the Sun. Most of the radiation is at infrared wavelengths, from dust in the bipolar nebula. Astronomers still do not know what lies at the heart of Eta Carinae. Most believe that it is powered by an extremely massive star which may have a companion.
XRAY OF Eta Carinae X-ray image of ETA CARINAE

Eta Carinae may be an extreme example of a luminous blue variable-a critical stage in the evolution of the most massive stars. Such a star can produce intense amounts of radiation that causes violent instabilities before it explodes as a supernova, or even possibly a "hypernova," a type of super-supernova explosion that has been hypothesized to produce gamma ray bursts.

The Chandra X-ray image gives an important glimpse deep into the nebula where the fastest material being thrown off by Eta Carinae is found. The outer ring provides evidence of another large explosion that occurred over a thousand years ago. Further Chandra observations of Eta Carina are planned for the near future and should give astronomers deeper insight into this cryptic colossus.

Return to Eta Carinae (08 Oct 99)