Great Eruption of Eta Carinae, a massive star some 7,500 light-years away that suddenly lit up the night sky for a decade beginning in 1838 is one of the most studied objects in the Milky Way. But it continues to puzzle astronomers.
An explosion in space first seen in the 19th century was apparently colder than before thought, throwing a new mystery into what may have triggered it, researchers say.
The cosmic eruption came from Eta Carinae, a star about 7,500 light-years away from Earth that is one of the most massive stars in our Milky Way galaxy. It blazed into ultra-brightness in 1838, becoming the second-brightest star in the sky for 10 years in a rare celestial outburst later dubbed the "Great Eruption." The star later dimmed, and is now not even in the top 100 list of brightest stars.
Scientists have found that Eta Carinae is a kind of star known as a luminous blue variable, meaning it goes through episodes of dimness and brightness. These rises and falls in luminosity are caused by mounting instability within the star followed by a dramatic loss of mass. The Great Eruption of Eta Carinae was an especially catastrophic event, where the star — once about 140 times the mass of the sun — lost mass equal to about 20 times that of the sun.
Scientists believed this rare kind of eruption was caused by a stellar wind blowing off the stars. Still, much remained uncertain, since a key detail about the Great Eruption was missing — its pattern of light. This spectrum would help yield details such as the temperature, composition and velocity of matter from the eruption. [Amazing Photos of Star Explosions]