Galactic gas caused by colliding comets suggests mystery ’shepherd’ exoplanet

Latest research has uncovered a massive clump of carbon monoxide in a young solar system. The gas is the result of near constant collisions of icy comets - suggesting vast swarms of tightly packed comets in thrall to the gravitational pull of an as-yet-unseen exoplanet. We think the Beta Pictoris comet swarms formed when the hypothetical planet migrated outward - Mark Wyatt Astronomers exploring the disk of debris around the young star Beta Pictoris have discovered a compact cloud of carbon monoxide located about 8 billion miles (13 billion kilometers) from the star. This concentration of poisonous gas - usually destroyed by starlight - is being constantly replenished by ongoing rapid-fire collisions among a swarm of icy, comet-like bodies. In fact, to offset the destruction of carbon monoxide (CO) molecules around the star, a large comet must be getting completely destroyed every five minutes, say researchers. They suggest the comet swarm is most likely frozen debris trapped and concentrated by the gravity of an as-yet-unseen exoplanet. This mystery 'shepherd' exoplanet - so-called for its capacity to corral the swarms of comets through its gravitational pull, like Jupiter in our own solar system - is likely to be about the size of Saturn.     "Detailed dynamical studies are now under way, but at the moment we think this shepherding planet would be around Saturn's mass and positioned near the inner edge of the CO belt," said Mark Wyatt, from Cambridge's Institute of Astronomy, who proposed the shepherd model - currently the favoured hypothesis because it explains so many puzzling features of the Beta Pictoris disk.