Astronomy Picture of the Day

Explanation: How did the Eta Carinae star system create this unusual expanding nebula? No one knows for sure. About 170 years ago, the southern star system Eta Carinae (Eta Car) mysteriously became the second brightest star system in the night sky. Twenty years later, after ejecting more mass than our Sun, Eta Car unexpectedly faded. Somehow, this outburst appears to have created the Homunculus Nebula. The three-frame video features images of the nebula taken by the Hubble Space Telescope in 1995, 2001, and 2008. The Homunculus nebula's centre is lit by light from a bright central star, while the surrounding regions are expanding lobes of gas laced with filaments of dark dust. Jets bisect the lobes emanating from the central stars. Expanding debris includes streaming whiskers and bow shocks caused by collisions with previously existing material. Eta Car still undergoes unexpected outbursts, and its high mass and volatility make it a candidate to explode in a spectacular supernova sometime in the next few million years.