A Graveyard of Dead Comets
Back in the days of sailing ships, sailors found interesting areas in the world’s ocean. The Sargasso Sea was one of them. It’s a region in the North Atlantic Ocean where currents create the North Atlantic Gyre. Those currents bring in all kinds of debris, which remains stuck in the region. It’s also rich in a type of seaweed called Sargassum. Occasionally ships would get stranded there for brief periods of time due to lack of wind power to push their ships along. The Sargasso isn’t an especially deadly place, but it has been an area of great interest to marine biologists.
Our solar system has a Sargasso-like region called the Asteroid Belt, which contains a LOT of debris that has long thought to be leftovers of planetary formation that couldn’t quite get it together because of gravitational interference from Jupiter. It’s also apparently home to a lot of “dead” cometary nuclei. This area of the solar system contains more than a million objects that range in size from a meter to more than to 800 kilometers.
A team of astronomers from the University of Antioquia, Medellin, Colombia, have examined this region of space and discovered what they call a graveyard of dead comets in the belt. Astronomer Ignacio Ferrin has just published a paper in the journal Monthly Notices of the Royal Astronomical Society, describing how what observers long thought were dead rocks in the Asteroid Belt actually turned out to be dormant comets stuck floating around out there in a solar system Sargasso.
“Dormant” means that these cometary corpses could come back to life. All they need is a Sunward nudge, and many of them would perk up as their remaining gases and ices started to sizzle again. A little push from Jupiter (via its strong gravitational pull), and the shape of any of these objects’ orbits could change, sending them closer to the Sun.
According to Ferrin and his team, the main region of the Asteroid Belt had a population of comets that formed “in situ” (meaning they formed right where they’re found) as the solar system formed. This area was once bristling with thousands of very active comets millions of years ago. As they aged and lost their outer ices, these comets began to quiet down. Ferrin’s team has studied at least 12 of these once-glorious comets that somehow got a little push toward the Sun and began fizzing again. There are very likely many more of what Professor Ferrin calls “Lazarus Comets” circling out in the Belt, just waiting for the chance to get a little closer to the Sun and get active again. Interested in learning more about how Ferrin and his team studied these comets and their implications for solar system history? Check out their paper here or, if you’re a member of the Royal Astronomical Society, you can learn more here.