Homunculus Nebula

Astronomers peer into the galaxy’s most violent star system

For the first time, astronomers have stared into the heart of the most hellishly violent star system in the Milky Way galaxy. They like what they see. Eta Carinae is a pair of gigantic stars that shines 5 million times more brightly than the sun. Part of the brightness comes from stellar wind, which the two stars blow off at a furious pace. At a point between the pair, the opposing blasts collide at 12 million kilometers per hour and heat the gas to tens of millions of degrees so that it glows brightly as x-rays. This ejected material, known as the Homunculus Nebula (pictured above), has obscured astronomers’ view—until now. A team of astronomers combined the light from three of the four 8-meter telescopes at the European Southern Observatory’s Very Large Telescope in an optical device called an interferometer. This produces an image with the resolution of a much larger telescope. As they report today in Astronomy and Astrophysics, they were able to make out features in the collision zone (inset above), including a fan-shaped structure as the thinner wind from the smaller star slams into dense gusts from its larger companion. Using the interferometer, they were also able to better measure the speeds of the stellar winds. That will help astronomers model the pas de deux of dying star systems like Eta Carinae, and how that dance can generate such explosive cosmic fireworks.