This month we are reprising a popular segment of The Astronomer’s Universe that talks about the giant star Eta Carinae. This stellar behemoth is a supermassive star that will go supernova soon.
Astronomers have been studying the region of the sky in the Southern Hemisphere constellation Carina with great interest since the 1840s. That’s Eta Carinae — a supermassive star embedded in a nebula there brightened up considerably, making it one of the brightest stars in the sky. Over time, it dimmed down again. Today, we know that Eta Carinae is a massive stellar giant, called a luminous blue variable, is paired with a white dwarf. We also know that Eta Carinae is going to explode as a type of supernova called a hypernova. It will be an incredibly bright event, something that could brighten that region of the sky again when it finally occurs.
Eta Carinae is part of the vast Carina Nebula, a cloud of gas and dust and bright stars that lies about 7,500 light-years from Earth. The star itself has about 100 times the mass of the Sun, making it one of the most massive stars known. If this star could be placed in our solar system where the Sun is now, its atmosphere would reach all the way out past the orbit of Jupiter.
Eta Carinae is a million times brighter than the Sun, and it may only be a few million years old. That makes it a newborn in comparison to stars like the Sun, which is around 6 billion years old. Stars as massive as Eta Carinae live fast and die young. This one has entered its final stage of life and is very unstable. It’s losing mass through giant outbursts, and the material it’s puffing off is creating a double-lobed cloud around the star. Astronomers are zeroing in on that cloud to understand the process that is causing the star to emit such prodigious quantities of material. Is this a part of the death of all supermassive stars? When will this star ultimately explode? Those are questions astronomers are still working to answer through continuing observations of Eta Carinae.