Interesting science facts - Comets

Comets are small Solar system bodies composed of a mixture of rocks, dust, frozen water, methane, and ammonia.

Comets orbit the Sun, and most of them have highly elliptical orbits.

We can see a comet's tail when comet comes close enough to the Sun because of the reaction between the the solar radiation and the comet's nucleus.

Comets, unlike planets in our solar system do not always stay approximately at the same place, spend most of their time on the outskirts of the Solar System, even beyond Pluto.

The comet's tail always points away from the Sun, but not away from the comet’s direction of motion.

As of May 2009 there are a reported 3,648 known comets.

Short-period comets originate in the Kuiper Belt. Kuiper Belt is a region of the Solar System beyond the planets extending from the orbit of Neptune to approximately 55 AU (astronomical units) from the Sun.

Long-period comets originate in the Oort cloud. Oort cloud is basically a hypothetical spherical cloud of comets which lies approximately one light year from the Sun.

Comet nuclei can range from about 100 meters to more than 40 kilometers.

Each time a comet swings into the inner solar system toward the Sun, it loses some of its ice.

The most famous comet of them all, Halley's comet loses one meter of its surface (ice) each time it comes near the Sun.

Halley's comet can be see every 75–76 years, and it is one of the few comets that can be seen with the naked eye.

Comets always have irregular shapes due to the fact that they have low mass so they cannot become spherical under their own gravity.

Most comets can't be visible without the aid of a telescope but some like Halley's comet can.

The comets in the Oort Cloud need more than one million years to make a single revolution around the Sun.

Every year there are dozens of new comet discoveries.

Meteor showers are the result when comet's path crosses Earth's path. The most famous meteor shower is definitely the Perseid meteor shower that happens every year in period between August 9 and August 13, at the time when Earth passes through the orbit of the Swift–Tuttle comet.

Many scientists believe that about 4 billions years ago comets bombarded the Earth also bringing in the process the vast quantities of water into Earth's oceans, and even to Moon.

Earth's collision with some comet is less likely than earth's collision with some asteroid.

A catastrophic collision of some comet with Earth is only likely to happen at several-million-year intervals on average.

The comets are rich resources for water and carbon-based molecules necessary to sustain life unlike asteroids that are excellent source of minerals.