“We are coming to understand the present state and complex environment of this remarkable object, but we have a long way to go to explain Eta Carinae’s past eruptions or predict its future behavior,” says NASA astrophysicist Ted Gull.
Eta Carinae has always been a puzzle for scientists. In the 19th century, the superstar erupted twice and no one knows why.
Gull led a group of astronomers who studied the superstar for more than a decade. Everything from NASA satellites to ground-based telescopes to theoretical modeling was used to create the most in-depth look at Eta Carinae.
Eta Carinae sits 7,500 light-years away from Earth in the southern constellation of Carina. The star system is actually comprised of two huge stars. The stars’ orbits bring them incredibly close to each other every 5.5 years.
Getting a closer look at the two stars has proved difficult due to the amount of stellar winds produced by the two stars.
Here’s what Gull and his fellow astronomers do know. The brighter primary star has 90 times the mass of our sun and shines 5 million times brighter. Info on the smaller star is a bit less concrete, but it is believed to be about 30 times the size of the sun and shine a million times brighter.
When the two stars are at their closest, just 140 million miles separate them. That’s about the distance between Mars and the sun. Sounds far to us, but is incredibly close for stars.
Astronomers noted increases in X-ray flares as the two stars reached periastron (closest approach). Right after periastron, X-ray emissions see a sudden decline as the smaller star whips around the bigger star. The X-ray emissions than recover.
The simulation above shows the two stars of Eta Carinae as black dots. Lighter colors show dense stellar winds.
Gull and his team noted different properties in stellar wind from each star. The primary star’s (bigger one) stellar winds blow at one million miles per hour. The smaller star’s stellar winds blow at six times that speed. But, the primary star’s wind carries the equivalent mass of our sun every thousand years. The smaller star’s wind carries 100 times less material.
You can see the material in the image below.
The two explosions in the 1840s created the Homunculus Nebula. Stretching about a light-year long, it has enough material to produce 10 sun-like stars.
Image credits: NASA