Meteor showers

Shooting stars move so fast that they are difficult to see and, according to superstition, they can also grant you wishes. Meteor showers are undoubtedly a spectacle worth watching. But what are shooting stars actually? And how do meteor showers occur?

What is a shooting star?

Shooting stars get their name because they look like a white dot, like stars, but they cross the sky so quickly that they are hard to see.

Although they appear to be as far away as normal stars, they are actually small bits of rock or dust entering the atmosphere. While in space, these pieces of rock are called meteoroids; the streak of light they produce as they enter the atmosphere is called a meteor. Meteors should not be confused with meteorites, since the rock of a meteor does not reach the surface of the Earth. This is because they are so small (from millimeters to centimeters in diameter) that they vaporize and disintegrate in the atmosphere from colliding with the air at high speed.

Contrary to what you may think, the glow is not due to the rock burning. In reality, both the glow and the tail are due to vaporized material from the meteoroid and the hot, ionized air along its path.

What is a meteor shower?

While a meteor can cross paths with Earth at any time, there are times when several shooting stars per hour can be observed over several days. Events like that are called meteor showers.

What causes a meteor shower?

Meteor showers are a consequence of the passage of comets (and, in a few cases, asteroids). Comets are made of a mixture of ice and rock. As the comet approaches the Sun, it slowly disintegrates, producing the familiar comet tail that we can see. The debris that detaches from the comet remains in the same orbit or a very similar one and is concentrated at points close to the comet.

The orbits of comets are usually much more elongated than those of planets, and they are not in the same plane. Sometimes a comet's orbit intersects or overlaps Earth's, and as Earth passes through that area, it encounters the cloud of dust, rock, and ice left by a comet's passage, giving rise to a meteor shower.

How to observe a meteor shower?

The best way to observe them is to find a place with little artificial light and a clear sky. They are best seen with the naked eye, but binoculars can also help. They can usually be seen throughout the night or most of it. The names of each meteor shower come from the constellation from which they appear to come. But meteors can appear anywhere in the sky, so it is best to look at a wide area, somewhat away from that constellation, where the trails look longer.

Meteor showers are usually active from a few days to about a month and, at their peak, between 10 and 50 shooting stars per hour can be observed under dark skies (the strongest, such as the Geminids, can exceed that). The densest showers recorded were the Leonid storms of 1833 and 1966, the latter with estimated peaks of up to 40 meteors per second (about 144,000 per hour); in 2001 the rate reached about 3,000 per hour. The Leonids occur every November. Major storms occur when Earth crosses dense clouds of dust from comet Tempel-Tuttle, which takes about 33 years to orbit the Sun; this caused the storms mentioned above and those in 1866, 1999, 2001 and 2002. According to the International Meteor Organization, Earth is not expected to cross another dense cloud of this debris until 2099, so the comet's next returns might not produce storms.

Don't forget to check the International Meteor Organization's meteor shower calendar to find out when meteor showers occur and under what conditions they are best observed.