Beautiful Star Death Imaged in Spectacular Picture

When a star dies, it can sometimes go out in a spectacular way, creating lights and colors that are beautiful to see in pictures. Now, scientists have gotten a closer look at one of these dying stars, known as a planetary nebula. They've imaged NGC 2392, also known as the "Eskimo Nebula," in an effort to learn a bit more about these types of nebulas.

Planetary nebulas form when a star uses up all of the hydrogen in its core--something that our own Sun will experience in about five billion years. When this happens, the star begins to cool and expand, increasing its radius by tens to hundreds of times its original size. The outer layers of the star are then carried away by stellar winds, which strip away material and leave behind the hot core. This core then continues to eject more layers in a much faster wind. Eventually, this creates the complex and filamentary shell of a planetary nebula. In time, the remnant will collapse to form a white dwarf star.

In order to more closely examine NGC 2392, researchers used X-ray data from NASA's Chandra X-ray Observatory and the Hubble Space Telescope. With this information, the scientists were able to see the location of million-degree gas near the center of the planetary nebula, colored in purple. They were also to see the intricate pattern of the outer layers of the star colored in red, green and blue. This allowed them to see exactly how the stellar winds were interacting.

So what did the researchers find? It turns out that NGC 2392 has unusually high levels of X-ray emission compared to two other planetary nebulas that the scientists examined. Because of these emissions, it's very likely that NGC 2392 possesses an unseen companion-the interaction between a pair of binary stars could explain the elevated X-ray emissions. The fainter X-ray emission observed in the two other planetary nebulas, in contrast, is likely produced by shock fronts (like sonic booms) in the wind from the central star. 

The findings are available online and were published in The Astrophysical Journal.