NASA Finds Massive Star a Partner
After first radiating to prominence in the early 1840’s when it fired to become the second brightest star in the sky, Eta Carinae is back in news as scientists using NASA’s Far Ultraviolet Spectroscopic Explorer satellite made the first direct detection of a companion star of Eta Carinae.
Eta Carinae is one of the most massive and unusual stars in the Milky Way galaxy. This mysterious star, which scientists think is in the final stages of life, is located 7,500 light-years from Earth in the constellation Carina. Its companion star completes an orbit every 5.5 years, and FUSE was able to detect when it passed behind Eta Carinae, briefly dimming the amount of high-end ultraviolet radiation coming from the pair.
"Until now, Eta Carinae’s partner has evaded direct detection," said Dr. Rosina Iping, a research scientist at Catholic University of America in Washington. "This discovery significantly advances our understanding of the enigmatic star."
Evidence that Eta Carinae might be a double star system was inferred from a repeating pattern of changes in visual, X-ray, radio and infrared light over approximately 5.5 years. Astronomers thought a second star in a 5.5 year orbit around Eta Carinae might cause the repeated changes in its light. The strongest indirect evidence supporting the double star theory is that once every 5.5 years, the X-rays coming from the system disappear for about three months. Eta Carinae is too cool to generate X-rays, but it continuously blasts a flow of gas into space as a stellar wind at about 300 miles per second.
Several scientists searched for light from Eta Carinae’s companion using ground-based telescopes to detect the possibility of a double star system, but none succeeded. Because the companion is thought to be much hotter than Eta Carinae, astronomers reasoned it should be brighter at shorter wavelengths like ultraviolet light. However, it still escaped detection when it was searched for using the ultraviolet capabilities of the Hubble Space Telescope.
This discovery is all set to be published in the Astrophysical Journal Letters.
