As comets travel in their orbit, they shed material along the way. A debris flow known as the Taurid swarm has caught the attention of astronomers. The debris is believed to be remnants of Comet Encke, which also fueled the Taurid meteor shower. The swarm is thought to consist largely of harmless, tiny objects, but there are fears there could also be some larger, kilometer-sized chunks. Fortunately, new observations show that there are on the order of 9-14 of these 1 km large rocks.
Planets, minor planets, asteroids and of course comets are the inhabitants of our solar system. The comets are small objects composed mostly of ice and dust or rocky material. A wonderful and apt description of these icy wanderers are dirty snowballs. Imagine picking up a handful of snow and ice on a winter day. It is likely that pieces of earth and stone get mixed up under the snow, and that is what earned them this name. They come from remote parts of the solar system, particularly the Kuiper Belt and the Oort Cloud. As they approach the sun, the heat causes the ice to sublimate into a gas, creating the gaseous coma and long tail. As the com moves in its orbit, the sublimation of the ice releases dust and debris along the way.
Comet image from Hubble
One such comet is known as Comet Encke, a short-period comet with an orbital period of 3.3 years. It was first discovered by Pierre Mechain in 1786 and its orbit was calculated by Johnann Franz Encke at the end of the 19th century. While most comets come from the Kuiper Belt or Oort Cloud, Encke seems to have found a way closer to the Sun with regular, predictable visits. Like all comets, Encke deposits debris along the way, resulting in the Taurid meteor shower, visible in late October/early November.
Comet Encke, imaged by NASA's Mercury MESSENGER spacecraft. Photo credit: NASA
A team of astronomers used the Zwicky Transient Facility (ZTF) telescope to explore large swathes of the sky to study the stream of debris that is believed to have drifted down from the main Taurid stream. This drifting swarm is believed to be the remnants of Comet Encke. It has long puzzled astronomers and raised concerns that rocks may be heading toward Earth. That is, until now.
The study built on previous efforts to analyze the swarm and had identified a significant number of kilometer-class rocks. Objects of this size would pose a significant threat to Earth. We were reminded of such dangers back in 2013 by the Chelyabinsk asteroid, which exploded over Russia and injured over 1,600 people.
This image of a contrail was taken about 200 kilometers from the Chelyabinsk meteor event, about a minute after the house-sized asteroid entered Earth's atmosphere. Photo credit: Alex Alishevskikh
The team announced their findings at the annual meeting of the American Astronomical Society Division for Planetary Sciences. They confirmed that, contrary to expectations, there are only a handful of asteroids, perhaps up to 14 kilometers in size. Deputy research scientist Quanzhi Ye explained: “Judging from our findings, the parent object that originally created the swarm was probably closer to 10 kilometers in diameter than a massive 100-kilometer object.” “We still need to be on our guard.” “It could be asteroid impacts, but now that we know these results we can probably sleep better.”
By studying features like the Taurid swarm, we can learn more about smaller objects in the solar system and how they break apart over time. The study will also support future asteroid detection and defense planning exercises if real threats are identified. As for the Taurid swarm, follow-up observations will be completed in the coming years as the swarm passes close to Earth again.
Source: New study allays concerns about a possible 'doomsday' asteroid swarm
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