Are Comets falling stars? Can they strike Earth? NASA reveals what they are
We very well know that in the solar system, planets orbits the Sun. But do you know that along with planets, there are objects made up of dust and ice called comets, that also orbit the sun. They are rare to see and when they come, they flaunt their magnificently luminescent tails. As NASA mentions, comets are large objects made of dust and ice that orbit the Sun. Best known for their long and streaming tails, these ancient objects are leftovers from the formation of the solar system going back as far as 4.6 billion years ago.
After reading about the comets, a question that arises is where do they come from? Comets are usually found in the centre of the solar system. Some of them are found beyond the orbit of Neptune, which is the place where the Kuiper Belt lies. There are also known to exist short period comets that take less than 200 years to orbit around the Sun. Others live in the outer edge of the solar system, called Oort Cloud which is 50 times farther away from the Sun. These comets are known as long-period comets and they take 250,000 years to complete one orbit of the Sun.
We usually get to read news of a comet coming towards Earth and eventually head towards the Sun. So, do comets die when they enter the solar system? The answer is unclear yet, but they do when the gravity of a planet or star pulls the comet from their trajectory towards them and a collision occurs. This changes their direction towards the Sun and this is when some comets dive right into the Sun, never to be seen again. When the comet is in the inner solar system, either coming or going, that's when we see it in our skies.
For thousands of years people have been interested in learning about comets but since we can't see or look at them from the Earth, it was difficult to know much about them. It has certainly changed now as in recent years several spacecraft have had the chance to study comets up close. A case in point was the comet Leonard that visited us a few months ago and spacecraft from Earth were able to photograph it whiz past us.
A few years ago, NASA's Stardust mission collected samples from Comet Wild 2 and brought them back to Earth. Scientists found those particles to be rich in hydrocarbons, which are chemicals we consider the “building blocks” of life.
Rosetta, a mission of the European Space Agency that had several NASA instruments onboard, studied Comet 67P Churyumov-Gerasimenko. Rosetta dropped a lander on the nucleus, then orbited the comet for two years. Rosetta detected building blocks of life on this comet, too.