The disk around 49 Ceti is known to show characteristics of both protoplanetary and debris disks. New observations with Herschel reveal that it is likely a debris disk with gas generated by evaporating comets.
Star formation is enhanced when two galaxies interact or merge. But what is the orbital extent of enhanced star formation in interacting galaxies? At which projected separation of the two galaxies does it disappear?
Shapiro time delays are one of the four tests of general relativity possible in the solar system. Astronomers can use these timing delays to measure properties of binary pulsar systems.
Seven gas clouds have been found in the region between two galaxies. Are they part of a intergalactic filament or remnants from a past galaxy interaction?
Mercury’s high density has been a longstanding puzzle in planetary science. Its density means that it must have a significantly higher iron abundance than Venus, Earth, Mars, or the asteroids, probably in the form of a large iron core. NASA’s MESSENGER mission has challenged many of the hypothesized ways to create an iron-rich Mercury; a new hypothesis is required.