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Meteor Showers and Shooting Stars: Formation, Facts and Discovery

Watching a meteor shower on a clear, dark night is an unforgettable experience. This cosmic show makes even the most hardened astronomer gaze in awe at the thousands of streaking light strobes that pierce the night sky for an impressive celestial display.

Meteor showers occur when dust or particles from asteroids or comets, entering the Earth's atmosphere at very high speed. When they hit the atmosphere, meteors rub against air particles and create friction, heating the meteors to more than 3,000 degrees Fahrenheit. The heat vaporizes most meteors, creating what we call shooting stars (most become visible at around 60 miles up). Some large meteors splatter, causing a brighter flash called a fireball, which can often be heard up to 30 miles away.

What meteors are

Most meteors are very small, some as tiny as a grain of sand, so they disintegrate in the air. Larger ones that reach the Earth's surface are called meteorites and are rare.

Whether an object breaks apart depends on its composition, speed, and angle of entry. A faster meteor at an oblique angle suffers greater stress. Meteors made of iron withstand the stress better than those of stone. Even an iron meteor will usually break up as the atmosphere becomes denser, around 5 to 7 miles up.

Large meteors can explode above the surface, causing widespread damage from the blast and ensuing fire. This happened in 1908 over Siberia, in what’s called the Tunguska event.

Facts about meteor showers

This view of comet Halley's nucleus was obtained by the Halley Multicolour Camera (HMC) on board the Giotto spacecraft, as it passed within 600 km of the comet nucleus on March 13, 1986.
This view of comet Halley's nucleus was obtained by the Halley Multicolour Camera (HMC) on board the Giotto spacecraft, as it passed within 600 km of the comet nucleus on March 13, 1986.
Credit: ESA. Courtesy of MPAe, Lindau

Meteors are often seen falling from the sky alone — one here, one there. But there are certain times in a year when dozens or even hundreds of meteors per hour will light up the sky, seemingly coming from one part of the sky, radiating in all directions, and falling toward Earth one after the other.

Meteor showers happen when the earth passes through a trail of debris left by a comet. For example, the Orionid meteor shower happens when the earth passes through a cloud of debris left by Halley's comet. Others are caused by debris from asteroids. Thousands of these particles can enter the earth's atmosphere, ignite, and leave fiery trails as they burn out.

On average, meteors can speed through the atmosphere at about 30,000 mph (48,280 kph) and reach temperatures of about 3,000 degrees Fahrenheit (1,648 degrees Celsius). Sometimes, meteors can explode in magnificent fireballs that can sometimes be seen during the day.

Meteor showers to watch out for

There are several periodic meteor showers that astronomers and amateur observers wait for every year.

Leonids: The brightest and most impressive is the Leonid meteor shower or King of Meteor Showers which can produce a meteor storm that showers the earth with thousands of meteors per minute at its peak. In fact, the term meteor shower was coined after astronomers' observed one of Leonids' most impressive displays in 1833. Leonids most beautiful meteor shower only happens at intervals of approximately 33 years, with the last one lighting the earth's sky in 2002 and is not expected to be repeated until 2028. [Amazing Leonid Meteor Shower Photos]

Perseids: Another shower that is worth keeping awake at night is the Perseid meteor shower, which is associated with the comet Swift-Tuttle. The earth passes through the comet's orbit during the month of August every year. It is not as active as the Leonids, but it is the most widely watched meteor shower of the year, peaking at August 12 with more than 60 meteors per minute.

Orionids: The Orionid meteor shower, as mentioned above, showers the earth with meteors from the Halley's comet which orbits the sun every 75 to 76 years. The Orionids shower happens every October and can last for a week, treating patient observers to a show of 50-70 shooting stars per hour at its peak. Meteor showers are named after the constellations from where the shower appears to be coming from. [Photos: Orionid Meteors of 2011]

The Orionids originate from the mighty Orion constellation while Perseid meteors seem to be coming from the Perseus constellation. Other meteor showers worth watching for are the Quadrantids, Geminids, and Lyrids.

Quandrantid Meteor over Northern Florida
Richard Hay sends this image of a Quadrantid meteor and says: "My wife and I ventured out into the frigid 26-degree Florida night this morning to catch the shower with our own eyes, and [were] rewarded with about 20 or so bright Quadrantids over a 90 minute period."
Credit: Richard Hay

Quadrantids: The Quadrantid meteor shower came from the debris the asteroid called 2003 EH1 which is most probably a part of a comet that broke apart centuries ago. The debris entered the earth's atmosphere early January 2012 and offered astronomers and other earth observers a brief show that lasted a few hours. [Spectacular Quadrantid Meteor Photos]

Geminids: Like the Quadrantids, the Geminid meteor shower also came from dust particles of an asteroid, this time a near-earth asteroid called 3200 Phaeton. Meteor showers are mostly from comets, so having an asteroid as parents make the Quadrantids and Geminids different from other meteor showers. The Geminids spray up to 40 meteors per hour out of the Gemini constellation at its peak.

Best time and place to see meteor showers

People living in the Northern Hemisphere are in the best position to observe the most beautiful meteor showers. For example, North America is right below the region of the sky where the January Quadrantids shower appears.

A bright moon can dim the prospect of seeing a good meteor shower, drowning out all but the brightest meteors. Local light pollution dampens prospects, too, so the best place to view a meteor shower is from out in a rural location.

Most meteor showers are best viewed in the pre-dawn hours, when the part of the Earth you are standing on is facing the direction of Earth’s orbit. It’s like bugs hitting a car's windshield. In the late evening hours, on the other hand, the meteors are less frequent — loosely akin to bugs hitting a car’s rear bumper.

Best time of year for meteor showers

Meteor showers can be seen at different times of the year depending on when the Earth is going to pass through the comet's or asteroid's path. Some meteor showers happen annually; others only appear over a period of several years, while some of the best shows — meteor storms — happen just once or twice in a lifetime.

Weather can also hamper a good view of meteor showers. A clear sky is a gift to night gazers, which is why meteor showers during the summer are more anticipated than those that fall in the winter months.

Sources and more reading

  • http://earthsky.org/astronomy-essentials/earthskys-meteor-shower-guide
  • http://solarsystem.nasa.gov/planets/profile.cfm?Object=Meteors
  • http://www.nasa.gov/topics/solarsystem/features/watchtheskies/quadrantids_2012.html

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