The Twin Jet Nebula

The Twin Jet NebulaThis cosmic butterfly is called the Twin Jet Nebula. It’s a planetary nebula but not just any planetary nebula—it’s a bipolar nebula.

An ordinary planetary nebulae have one star at its center. A bipolar nebulae has a binary star system. The wings of the Twin Jet Nebula are thought to be caused by the motion of its two central stars around each other. As the dying main star and its white dwarf companion orbit around their common center of mass, the ejected gas from the dying star is pulled into the two lobes. The two stars at the heart of the nebula circle one another about every 100 years. This rotation not only forms the wings of the butterfly and the two jets, it also allows the white dwarf to strip gas from its larger companion which then forms a large disc of material around the stars extending out for billions of kilometers, up to 15 times the orbit of Pluto. Even though that disk is of huuge, it is still too small to be seen on the image taken by Hubble.

Image Credit: ESA / NASA

A Mountain on Ceres

MountainThe Dawn spacecraft has returned images of this tall, conical mountain on Ceres. The mountain is located in the southern hemisphere and is about 6 km high. Its perimeter is sharply defined, and there almost no accumulated debris at the base of the brightly streaked slope.

This image was taken from an altitude of 1470 km. Dawn will spend the next couple of months mapping the planet from that height. Next, it will move to within 375 km of the surface.

BTW, there’s still no word on those bright spots.

Image Credit: NASA

Dione Close Up

Dione chasmsSome parts of the surface of Saturn’s moon Dione are covered by linear features, called chasmata, in dramatic contrast to the round impact craters that cover most moons. The bright network of fractures on Dione was seen in poor resolution Voyager images and was called “wispy terrain.” The actual nature of this terrain was unclear until Cassini photos showed we weren’t seeing something like surface deposits of frost but a pattern of bright icy cliffs among myriad fractures. This stress pattern may be related to Dione’s orbital evolution and the effect of tidal stresses over time.

Image Credit: NASA