Topic: Oort Cloud

Where did Earth's water come from? Comet Hartley 2 offers new clues.

The composition of comet Hartley 2 suggests that comets might have been a bigger source of Earth's water than previously thought. It's also challenging models of solar system formation.

Stars hurtling through space could someday mess up our cosmic neighborhood

Researchers calculated the orbits of 40,000 low-mass M-dwarf stars and found 18 that may come dangerously close to our cosmic neighborhood in the next billion years. While the chances of this actually happening are probably slim, researchers said, the results could be dramatic.

Meteor shower August 2010: how you can get the best view

Meteor shower August 2010 peak comes early Friday. Emanating from the constellation Perseid, the meteor shower could yield sightings in some locations of up to 75 meteors an hour.

Comet Lulin arrives tonight - break out your telescopes

Look for comet Lulin -- it won't be back for a million years

The pros are turning major amounts of telescope glass on comet Lulin; the rest of us can see it through binoculars

Across the Milky Way, more planet Earths?

Two new discoveries suggest that sunlike solar systems like ours – with life-hosting planets – are more common than previously thought.