A Possible Scenario

These six panels show a possible scenario for the powerful blast seen 170 years ago from the star system Eta Carinae.

1. Eta Carinae initially was a triple-star system. Two giant stars (A and B) in the system were orbiting closely and a third companion C was orbitint much farther away.

2. When the more massive of the close binary stars (A) neared the end of its life, it began to expand and lost most of its material, which fell into its slightly smaller companion (B).

3. As the companion (B) grew to about 100 solar masses, it became extremely bright. Meanwhile, the donor star (A) was losing its outer hydrogen layers, exposing its hot helium core. The shift in the masses of the stars altered the gravitational balance of the system, and the helium-core star moves farther away from its monster sibling.

4. As it moved outward, the now smaller, but still quite large, helium-core star interacted gravitationally with the outermost star (C), pulling it into the fray. The two stars traded places, as the outermost star was kicked inward.

5. The massive inner stat’s gravity interacted with Star C, moving inward, creating a disk of material around the giant star.

6. Eventually, star C merged with the inner star, producing an explosive event that formed the bipolar lobes of material ejected. Meanwhile, the surviving companion, A, settles into an elongated orbit around the merged pair. Every 5.5 years it passes through the giant star’s outer gaseous envelope, producing shock waves that are detected in X-rays.

Image Credit: NASA / ESA / SRScI

The Homunculus Nebula

A massive pair of gas and dust clouds have been blown outward from the supermassive star Eta Carinae. A sequence of eight images taken through red and near-ultraviolet filters by the Hubble Space Telescope have been combined to produce this color image. Multiple exposures necessary to cover the nebula’s wide dynamic range: the outer blobs are 100,000 times fainter than the central star. Eta Carinae exploded about 160 years ago and became one of the brightest stars in the southern sky. Even though the star released as much visible light as a supernova explosion, it survived and produced the two lobes and a large, thin equatorial disk, all moving outward at about 1 million km/h.

Image Credit: NASA