Exoplanets are used to the limelight exocomets less so. Now, a fresh crop of comets found around alien stars suggests that these icy dirt-balls stalk solar systems across the Milky Way. Discs of debris swirling around young stars clump up to form planets. Asteroids and comets are the leftovers. But until now, astronomers had not seen many examples of these intermediate clumps. Read more
Using ESA's Herschel space observatory, astronomers have discovered vast comet belts surrounding two nearby planetary systems known to host only Earth-to-Neptune-mass worlds. The comet reservoirs could have delivered life-giving oceans to the innermost planets. In a previous Herschel study, scientists found that the dusty belt surrounding nearby star Fomalhaut must be maintained by collisions between comets. In the new Herschel study, two more nearby planetary systems - GJ 581 and 61 Vir - have been found to host vast amounts of cometary debris. Read more