REID: We’ve talked before about the biggest stars in the galaxy and we’ve told you about the smallest, but then there are stars like Eta Carinae A—a star so massive that it seems to defy the laws of physics. Eta Carinae is five million times brighter than the sun, one of the brightest stars in the galaxy. It’s so luminous that it’s gravity can barely contain the outward pushing pressure of its radiation. So it’s constantly shedding mass. And yet it’s still about ninety times as massive as the sun. With all these freaky features, this star, the larger of the two stars in the Eta Carinae system, have been dazzling astronomers for centuries. For observers here on earth, things started to get weird for Eta Carinae A back in the early eighteen hundreds. It started flickering faster and faster like the warning light on a bomb that’s about to explode. Then in 1837 it suddenly erupted pouring so out much gas out into space that it lost nearly the equivalent of the mass of the sun every year. Throughout this eruption, it grew in brightness until it was the second brightest star in the sky and stayed that way for almost twenty years. Eta Carinae A released nearly as much energy as a super nova but at a slower rate. By the time it’s outburst was finished it had released so much gas and debris that it actually created a nebula around itself. Nearly a century later, Argentine astronomer Enrique Gaviola called it a homunculus nebula because apparently he thought it looked like a plump little man. Eta Carinae is an example of the most extreme types of stellar heavy weights, stars that are among the most massive in the galaxy. With luminosity's that are millions of times higher than the sun. And since their surfaces are tens of thousands of degrees, these stars appear to be blue. So astronomers call them Luminous Blue Variables or LBVS. Stars this massive tend to go through huge outbursts like Eta Carinae did, but catching them in the act is tricky. That’s because these outbursts are only a short phase in the already short lifetimes of these extreme, high-mass stars. Keep in mind most stars, including the sun, loose some mass through stellar wind. But LBVS are the biggest losers, sometimes shedding half or more of their original mass through a combination of their winds and catastrophic outburst. When an LBVS is at its brightest so much light comes blasting out that the outer atmosphere of the star acts like a kind of solar sail, carried away on an unbelievably powerful stellar wind. This could be what happened when Eta Carinae A erupted in the eighteen-hundreds. Since then, astronomers have continued observing Eta Carinae and have been able to make highly detailed 3-D models of this funky looking homunculus nebula.Today these models help untangle how the streams of hot ionized gases flowing from the star interact with each other.  And it’s one of the few astrophysical structures that has been fully modeled in 3-D. You can even download the model and 3-D print your own homunculus nebula. But there are still a lot of questions we can’t answer yet. Like how exactly the end of the LBVS phase fits into the high-mass star’s life. Plus we don’t even know how these ultra-mass stars form in the first place, but we do know that some formerly LBVS stars have gone super nova soon after they erupted. So, Eta Carinae may have one more explosion in the works which means we may have one more amazing spectacle to look forward to. From one of the most unusual stars in the sky. Thanks for watching this episode of Sci Show Space, if you’d like to learn how you can help us keep exploring the universe together, go to subbable.com/scishow and don’t forget to go to youtube.com/scishowspace and subscribe.