For centuries, comets have captured our imagination. Across history they have been the harbingers of doom, inspired artists and fascinated astronomers. These icy remnants of the formation of the Solar System hold secrets to help us understand the events nearly 5 billion years ago. But before these secrets can be revealed, comets have to be studied and to study them they need to be found. A team of researchers have developed a technique to hunt down comets based upon data from meteor showers and to asses if they pose any threat to us here on Earth!
Comets are objects that orbit the Sun like the planets but their orbits are usually more elliptical. They are composed of dust, gas and water ice and often called ‘dirty snowballs.’ Many comets are part of, or were a part of the Oort Cloud or Kuiper Belt. These distant regions of space house many of the Solar System’s icy bodies. On occasions, interactions between the bodies in the clouds can send chunks in toward the inner Solar System transforming the dormant chunks of rock and ice into the comets we recognise. Driven by heating from the Sun, the ice immediately sublimates into a gas giving rise to a comets familiar fuzzy coma and tail. Contrary to popular belief, the tail of a comet doesn’t stream out behind the comet as it travels through space, instead, it always points away from the Sun pushed in that direction by the Solar Wind.
Comets are categorised as either short period comets or long period with the latter group having an orbit of more than 200 years. Due to their long orbits, scientists fear that one will be on a collision course with Earth and go completely un-noticed until it is too late. The risk of this occurrence is of course incredibly small but the impact could be catastrophic to life on Earth. A team of astronomers led by Samantha Hemmelgarn from the Northern Arizona University has published a paper in Planetary Science Journal where they explain their technique for identifying threats from long period comets using data from meteor showers.
“This research gets us closer to defending Earth because it gives us a model to guide searches for these potentially hazardous objects,” Hemmelgarn said. Meteor showers occur when the Earth passes through the debris left behind by a comet. The team has studied 17 meteor showers that are associated with long period comets and calculated where the parent comet should be in space.
Using the path of the meteor showers, the team can assess the liklihood that a long period comet could pose a threat over its future orbits. In the test cases, the model accurately predicted the comet locations including its direction and speed of travel. This provides the opportunity for astronomers to hone their search around the sky looking for long period comets rather than hope one might be spotted through automated searchers that scour the whole sky.
The obvious benefit is that early identification of a comet on a collision course with Earth means that there is more time to develop a plan for our defence. There is nothing yet that provides any concern for astronomers but the next impact event of extinction level, may be millions of years away. The team hope that their work and model will help to provide humanity with the earliest warning of potential impacts.
Source : How to Find a Comet Before it Hits Earth
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