We all have a crazy neighbor, whether we realize it or not.
Sound familiar? This hot-headed, fiery personality is one of the biggest kids on the block - huge in fact. This kid is a little unstable, with a history of doing things that are hard to figure out. And what a clothes-horse this one is - all wrapped up in amazing colors. Oh yeah, and there's a little irritating sibling who comes around every so often.
Our "neighbor" is a star about 120 times bigger than our sun and lives relatively nearby - about 7,500 light years away. It goes by the name Eta Carinae. It's possibly the most studied object outside our own solar system.
Mainly Eta is famous for its mysterious temper tantrum of astronomical proportions that rocked the galaxy back in the 1840s. The tantrum, dubbed the Great Eruption, ignited Eta for just a few years to become among the brightest stars in the night sky before it drastically faded, all for reasons unknown.
Eta is only one of two giant eruptions known in our galaxy in the past 1,000 years. (The other is P Cygni, first observed in the 17th century.)
A team led by Armin Rest says it has identified - for the first time - light echoes of the Great Eruption.
The light echoes, which provide direct scientific data from the Great Eruption, are sort of like fingerprints, says Rest. And they cast doubt on a popular theory about what caused the Great Eruption.
Learning more about what irritates Eta might help us find out more about the evolution of stars and the formation of the basic elements of the universe.
Eta, which is hundreds of thousands of years old, is close to the end of its life. It's much younger than our 5-billion-year-old sun, which is expected to remain the same for another 5 billion years. But Eta is so big that it's burning its fuel a lot faster than smaller stars.
In fact, Eta could explode in a supernova tomorrow - or anytime within the next 1 million years, says Rest. When that happens, the massive explosion will be visible on Earth during the day. But don't worry, it likely wouldn't have any other effect.
Theories about the Great Eruption put limits on how far Eta's temperature could have dropped at the time. But data from the light echoes shows Eta's surface got thousands of degrees cooler than expected - 8,540 degrees Fahrenheit, instead of the predicted 12,140. That throws water on the accepted Great Eruption theory called the opaque wind model.
That theory: the buildup of pressure inside the star blew off some of its surface area and let loose a mind-boggling amount of light. Now, "it seems like there must be something else" behind the eruption, says Rest, "and it's really unclear what it is."
The epic blow-out of material from the Great Eruption wrapped the star in a spectacular gaseous shroud called the homunculus nebula. It may be pretty to look at, but it gets in the way of scientists trying to learn more about Eta and its smaller sibling, an orbiting star discovered in 2005.
It's "wimpy," says Rest, comparing the companion star to a fly landing on a human nose. But he says he's "pretty convinced that it has something to do with the Great Eruption."
So when you think about it, it's pretty amazing to realize that light echoes can still reveal details about something that happened nearly 170 years ago. How does that work?
"These light echoes are not so easy to find," says Rest, but based on color, direction, motion and other factors, they can be identified. Basically, they're light from the Great Eruption that has been bouncing off gas, dust and other particles for all these years.
Some of the light is reaching us after bouncing off dust located behind Eta, which offers a chance to study Eta's backside, so to speak.
Before he first stumbled on Eta's light echoes a year ago, Rest was very doubtful about finding traces of this very old eruption. He normally studies light echoes from supernovas, which are very bright. "I had an hour of time at the end of the night, and I thought, 'it can never hurt, let's have a look.' "
"They're probably not even there," he recalls thinking. But after looking at the fourth of fifth image, he realized his expectations were wrong.
"I said, 'Oh my God, that's a light echo!' I've seen lots of them before, and so normally I can recognize light echoes pretty well," Rest remembers. "I was floored. I truly was floored."
The discovery has opened a door for Rest to conduct more light echoes research on Eta Carinae, perhaps fill in more blanks about the Great Eruption and maybe help solve one of astronomy's most vexing mysteries.