Researchers have found that the star was cooler than it was previously suggested.
"When the eruption was seen on Earth 170 years ago, there were no cameras capable of recording the event," explained Armin Rest, who is leading researcher. "Everything astronomers have known to date about Eta Carinae's outburst is from eyewitness accounts. Modern observations with science instruments were made years after the eruption actually happened. It's as if nature has left behind a surveillance tape of the event, which we are now just beginning to watch. We can trace it year by year to see how the outburst changed."