Eta Carinae is an incredible star system. One of its (at least) two stars weighs a few hundred times the mass of our Sun and is likely to go supernova soon. It is known to history thanks to a gigantic eruption that happened almost 180 years ago. Now researchers have estimated that material was expelled by the star very quickly at roughly one-twentieth of the speed of light.
The impressive velocity makes this the fastest stellar outburst that hasn't resulted in the destruction of the star. The findings are reported in two papers in the Monthly Notices of the Royal Astronomical Society. The team estimated that the ejected material was moving between 10,000 and 20,000 kilometers (6,000 and 12,000 miles) per second, 20 times faster than the winds typically produced by massive stars.
"We see these really high velocities all the time in supernova explosions where the star is obliterated," one of the team leaders, Nathan Smith from the University of Arizona, said in a statement. "Something must have dumped a lot of energy into the star in a short amount of time."
To explain the Great Eruption, as the event is known, the team suggest that the system used to have a third star, which collided with another star to form one monster star. And within half a million years, this massive star will go supernova and explode.
The estimate was possible thanks to seven years of observations. The team studied light echoes, the light reflected from the Great Eruption. The light from the event reached us in 1843 and since then stray photons have been redirected towards us by the interstellar medium.
"A light echo is the next best thing to time travel," Smith said. "That's why light echoes are so beautiful. They give us a chance to unravel the mysteries of a rare stellar eruption that was witnessed 170 years ago, but using our modern telescopes and cameras. We can also compare that information about the event itself with the 170-year-old remnant nebula that was ejected. This was a behemoth stellar explosion from a very rare monster star, the likes of which has not happened since in our Milky Way Galaxy."
Other supernovae have been known to produce big blasts in the decades before they explode. Eta Carinae’s end might come sooner rather than later, but being such a peculiar object it might still surprise us.