Friday, October 21, 2011

Spiral arms in disk suggests unseen planets

This image of the disk that is in orbit about the young star SAO 206462 suggests that this disk might be perturbed by one or more unseen planets. This image was acquired at the Japenese Subaru telescope in Hawaii by Carol Grady (Eureka Scientific). In this image, the central star is deliberately masked by the telescope's optics, which revealing a broad disk of gas and dust in orbit about the star. The size of this disk is at least twice the diameter of our Solar System. Planets are known to form in these circumstellar disks, and computer simulations of this process show that a young giant planet can also launch spiral density waves in such a disk. So this disk's spiral appearance does suggest that giant planets may have formed here. But keep in mind that this is not the only explanation. For instance, the gravity of passing star can also disturb a disk, and such a disturbance would wind-up over time and also resemble a spiral. But further study of this system may one day reveal whether the disk at SAO 206462 is indeed planet forming. See this press release for more details.

Thursday, October 13, 2011

Vesta's rugged surface

This image is a computerized rendering of what a hypothetical observer migth see when looking obliquely along the mountains and craters on the giant asteroid Vesta. Of course the Dawn spacecraft is in orbit about Vesta, and thus is always looking down upon the asteroid, so Dawn would never see anything like this. But Dawn has now collected enough measurements of Vesta surface topography to assemble a detailed computer model of the asteroid's surface. With that model, one can then calculate the view that any observer might see when looking in any direction about Vesta. Keep in mind that Vesta is only about 700 miles across, so the more distance mountains shown here would not be seen by that observer; they'd lie below the horizon and thus would be hidden. But that computerized view can be adjusted to remove the asteroid's curvature (ie, flatten the asteroid) while preserving its topography, as is seen here. See the Dawn website for more details about this computerized image of Vesta's rugged surface.