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Meteor Showers

A meteor shower is an astronomical event during which many meteors can be seen in a short period of time. Most meteor showers have a peak activity period that lasts between several hours and a couple of days. During this peak period, observers may spot between about 10 to more than 100 meteors per hour in the case of the major meteor showers. On rare occasions, during an extraordinarily intense meteor shower, observers might see as many as thousands of meteors per hour. There are about eight major meteor showers each year, and many more minor showers that produce smaller numbers of meteors.

The meteors from each meteor shower seem to fan outward from a specific spot in the sky. This spot in the sky is called the shower’s “radiant”. The name of each shower is derived from the location of its radiant. For example, the radiant of the Orionid meteor shower is in the constellation Orion, while the radiant of the Geminid meteor shower is in the constellation Gemini.

Astronomers have long known that each meteor shower occurs around the same date each year, year after year. Why is this so? The many small meteoroid particles that produce meteor showers are actually the cast-off debris from comets! As comets occasionally swing close to the Sun in certain parts of their orbits, the icy materials that make up the bulk of the comets are heated and melted. They escape into space, trailing behind the comets as the spectacular tails that we sometimes see from Earth. Although comets are mostly made of ice, they also contain bits of dust and small rocks embedded within the ice. As the ice melts, the rocks and dust also are freed and float off into space. Gradually, this cloud of debris drifts away from the comet itself, but continues to orbit the Sun along roughly the same path as the comet. Over many years, the debris spreads out along the orbit of the comet. When Earth, traveling along its orbit, crosses a comet’s orbit (though not necessarily anywhere near the comet itself), the cloud of debris slams into our atmosphere at high speeds, producing a meteor shower! For example, the Orionid meteor shower, which happens each October, is generated by Earth’s passage through the debris stream strewn along the orbit of the most famous comet of all – Halley’s Comet!

Most meteoroid particles that generate the meteors in a shower are quite small, ranging in size from a grain of sand to a pea-sized pebble. However, the particles are traveling extremely fast relative to Earth when they streak into our atmosphere. Typical speeds range between about 20 and 70 km per second (45 thousand to 157 thousand miles per hour)! The incredible pressure meteoroids experience when they collide with Earth’s atmosphere shatters them, transferring energy to atoms and molecules in the atmosphere, which then release the energy by glowing. This glow produces the bright trails of light in the sky we see as meteors.

Although the peak activity period for each meteor shower lasts a short time, it is often possible to see at least a few meteors associated with a given shower for several days before and after the peak. How should you look for meteors when there is a shower? Find a comfortable place to sit or lie down outside; lounge chairs that let you recline for viewing the sky are ideal. You don’t need to look directly at a shower’s radiant to see meteors; though the meteors will seem to fan out from the radiant, they will be visible all over the sky. It is best to be sure that the constellation in which the shower’s radiant lies is in the sky; take a look at our sky maps to help you with this. Since many meteors are faint, it is best to get away from lights if you want to see many meteors. Some years a shower’s peak happens near the time of a full moon; those are not the best years to view that shower. The best time for viewing meteors is between midnight and dawn, but meteors can be seen at any time of night if you don’t want to stay up that late!

Here is a list of the major meteor showers that can be seen each year:

  • Quadrantids (early January)
This movie shows the orbit of asteroid 2003 EH1. This “asteroid” may actually be an “extinct” comet. It may be the comet that the Quadrantid meteors come from. The movie flips between a view from above the Sun’s North Pole to a view from the ecliptic (the plane of the Earth’s orbit). It shows how this asteroid’s orbit carries it far out of the ecliptic plane. See how Earth is closest to the asteroid’s orbit around January 3rd. That is the time each year when the Quadrantid meteor shower happens.
Original animation by Windows to the Universe staff (Randy Russell). Images courtesy NASA/JPL.

The Quadrantid meteor shower happens every year in January. Meteor showers are times when you can see many meteors or “shooting stars” in one night. There are several meteor showers each year. Most meteor showers can be seen for several nights. Usually, there is one night when you can see the most meteors. That night is called the “peak” of the meteor shower. The peak of the Quadrantid shower is around January 3rd.

In 2010, the evening of January 3rd will be the best time to see Quadrantid meteors. However, the Moon may make it hard to see Quadrantid meteors in 2010. The Moon will be just past its full phase. Bright moonlight makes it hard to see dim meteors.

During a meteor shower, it looks like all of the meteors shoot outward from one place in the sky. That point in the sky is called the “radiant” of the meteor shower. Each shower has a different radiant. Meteor showers are usually named after the constellation that their radiant is in. But the Quadrantids are a bit odd!

In 1795 a French astronomer made up a new constellation. He called it Quadrans Muralis, which is the name of an instrument he used to measure the positions of stars. About 40 years later, other astronomers discovered a new meteor shower. The radiant of the new shower was in Quadrans Muralis, so they named it the Quadrantid meteor shower. However, in 1922 a group of astronomers got together and made up the official list of 88 constellations that we have today. Quadrans Muralis was not on that list… so the Quadrantids are named after a constellation that doesn’t exist any more!

Most of the Quadrantid meteoroids are very, very small – about the size of a grain of sand! However, they are moving very, very fast – around 41 km/s (about 92,000 mph)! When they hit Earth’s atmosphere, they burn up and glow; the glowing trails they leave behind for a second or two are what we see as meteors.

Can you guess where meteors come from? Most meteoroids in meteor showers are actually dust from a comet! When a comet gets near the Sun and heats up, its ices melt and dust trapped in the ice escapes into space. The dust spreads out over the comet’s orbit. When Earth crosses the comet’s orbit, we run into the dust – and see a meteor shower!

The Quadrantids are a strange meteor shower. People have known about most of the big meteor showers for many, many years. But not the Quadrantids! The first time anyone noticed the Quadrantids was in the 1820s and 1830s. Astronomers hunted for the comet that the Quadrantids came from for a long time. Finally, in 2003, an astronomer named Peter Jenniskens found an asteroid that seemed like it was on the right orbit to make the Quadrantids. Some astronomers think that asteroid is really a piece of an old, “extinct” comet. Some scientists believe that it might be part of a comet that was seen in China, Korea, and Japan in 1490 and 1491. Maybe that comet broke apart, and some of the pieces became the Quadrantid meteoroids.

  • Lyrids (mid to late April)
The red dot shows the “radiant” for the Lyrid meteor shower. The radiant is the spot in the sky that the meteors seem to fan out from.
Image courtesy of NASA.

The Lyrid meteor shower happens every year in April. Meteor showers are times when you can see many meteors or “shooting stars” in one night. Most meteor showers can be seen for several nights. Usually, there is one night – called the “peak” of the meteor shower – when you can see the most meteors. The peak of the Lyrid shower is around April 22nd.

During a meteor shower, it looks like all of the meteors shoot outward from one place in the sky. That point in the sky is called the “radiant” of the meteor shower. The radiant for the Lyrid shower is in the constellation Lyra.

If you want to see Lyrid meteors, go outside at night on April 22nd or one of the nights just before or after that date. You can see more meteors if you can watch from someplace very dark, away from streetlights. If you are lucky, you might see as many as 15 or 20 meteors in an hour! 2009 might be a good year for watching the Lyrids. At the peak of the shower the Moon will be at its waning crescent phase. That means there won’t be much bright moonlight (which makes it hard to see meteors).

Sometimes, very rarely, the peak of the Lyrids brings 100 or more meteors per hour. In 1982, observers counted over 90 meteors per hour. In 1803, a newspaper reporter watching the Lyrids “counted 167 meteors in about 15 minutes”! It was probably just such a “Lyrid storm” that caught the eye of Chinese astronomers in 687 BC, who wrote of “stars that fell like rain.” Humans have known of the Lyrid Meteors for more than 2,600 years… longer

  • Eta Aquarids (early May)
  • Delta Aquarids (late July)
  • Perseids (mid August)
  • Orionids (mid to late October)
This picture shows part of the sky at night. The constellation Orion is on the right. The place where meteors that are part of the Orionid meteor shower seem to shoot out from is on the left. That spot is called the “radiant” of the meteor shower.
Original Windows to the Universe artwork by Randy Russell.

The Orionid meteor shower happens every year in October. Meteor showers are times when you can see many meteors or “shooting stars” in one night. There are several meteor showers each year. Most meteor showers can be seen for several nights. Usually, there is one night when you can see the most meteors. That night is called the “peak” of the meteor shower. The peak of the Orionid shower is around October 21st.

During a meteor shower, it looks like all of the meteors shoot outward from one place in the sky. That point in the sky is called the “radiant” of the meteor shower. Each shower has a different radiant. The radiant for the Orionid shower is in the constellation Orion. That is why this shower is called the “Orionids”.

If you want to see Orionid meteors, go outside at night on October 21st or one of the nights just before or after that date. You can see more meteors if you can watch from someplace very dark, away from street lights. If you are lucky, you might see as many as 20 meteors in an hour!

Orion does not rise into the sky in late October until about 11 PM. The best time to see Orionids is late at night. However, it is still possible to see some meteors earlier in the night. Look towards the southeast to find Orion if you live in the northern hemisphere; or look towards the northeast if you live south of the equator.

Look at these sky maps to help you find Orion if you live in the United States. The 2 AM maps for October 15th should work pretty well. If you live somewhere other than in the USA, you might want to use an interactive sky map program to help you find Orion. See the link at the bottom of this page to an interactive sky map made by “Sky & Telescope” magazine. Even if you can’t find Orion, you can still see Orionid meteors. Just look up at the night sky in the southeast or northeast, depending on where in the world you live.

Most of the Orionid meteoroids are very, very small – about the size of a grain of sand! However, they are moving very, very fast – around 66 km/s (about 148,000 mph)! When they hit Earth’s atmosphere, they burn up and glow; the glowing trails they leave behind for a second or two are what we see as meteors.

Can you guess where these meteors come from? They are actually dust from a comet! When a comet gets near the Sun and heats up, its ices melt and dust trapped in the ice escapes into space. The dust spreads out over the comet’s orbit. When Earth crosses the comet’s orbit, we run into the dust – and see a meteor shower!

The dust that makes Orionid meteors is from a very famous comet. Have you ever heard of Halley’s Comet? Orionid meteors come from Halley’s Comet.

  • Leonids (mid November)
This picture shows a bright Leonid meteor that was seen in November 1998. The light from this meteor lit up some clouds, creating this beautiful photo opportunity!

The Leonid meteor shower is one of several major meteor showers that occur on roughly the same date each year. The Leonids typically “peak” (are at their greatest level of activity) in mid to late November. The Leonid shower’s name is derived from the fact that its meteors appear to fan out from a point in sky, called the shower’s “radiant”, which lies within the constellation Leo.

In 2009, the Leonid shower is expected to peak on the night of Tuesday, November 17th. Since there will be a New Moon around this time, this year should be a good year to spot some Leonids. A bright Moon makes it hard to see meteors.

As is the case with most meteor showers, it will be possible to see Leonid meteors for several days before and after the peak on the 17th. In fact, it is sometimes possible to see some Leonids as early as November 14th and to continue to spot a few up to November 21st. At this shower’s peak observers may be able to see as many as 100 “shooting stars” per hour under dark skies (away from city lights). However, the Leonids, as compared to other meteor showers, present a highly variable celestial show. The number of meteors visible at the shower’s peak can change quite a bit from year to year in an unpredictable fashion.

The Leonids are actually bits of dust that have been shed over the centuries by a comet named comet 55P/Tempel-Tuttle! The dust, which spews forth from the comet’s nucleus each time it passes near the Sun, gradually spreads out over the entire orbit of the comet. If Earth’s orbit happens to cross the comet’s orbit, the swarm of debris scattered along the comet’s orbit is visible to us as a meteor shower. Since the Earth crosses the comet’s orbit at the same time each year, each meteor shower is predictably visible at the same time of year, year after year.

Most meteors in a shower are quite small, about the size of a grain of sand. Leonids are among the fastest-moving meteors. These meteors typically strike our atmosphere while traveling at speeds around 72 kilometers per second (about 161,000 mph). Because of their high speeds, Leonids typically leave long, glowing trails in the sky.

  • Geminids (mid December)
This movie shows a very bright Geminid meteor. This meteor was seen in December 2002.

he Geminid meteor shower happens every year in December. Meteor showers are times when you can see many meteors or “shooting stars” in one night. There are several meteor showers each year. Most meteor showers can be seen for several nights. Usually, there is one night when you can see the most meteors. That night is called the “peak” of the meteor shower. The peak of the Geminid shower is around December 14th.

During a meteor shower, it looks like all of the meteors shoot outward from one place in the sky. That point in the sky is called the “radiant” of the meteor shower. Each shower has a different radiant. The radiant for the Geminid shower is in the constellation Gemini. That is why this shower is called the “Geminids”.

If you want to see Geminid meteors, go outside at night on December 14th or one of the nights just before or after that date. You can see more meteors if you can watch from someplace very dark, away from street lights. If you are lucky, you might see as many as 100 meteors in an hour!

Most of the Geminid meteoroids are very, very small – about the size of a grain of sand! However, they are moving very, very fast – around 35 km/s (about 78,000 mph)! When they hit Earth’s atmosphere, they burn up and glow; the glowing trails they leave behind for a second or two are what we see as meteors.

Can you guess where meteors come from? Most meteoroids in meteor showers are actually dust from a comet! When a comet gets near the Sun and heats up, its ices melt and dust trapped in the ice escapes into space. The dust spreads out over the comet’s orbit. When Earth crosses the comet’s orbit, we run into the dust – and see a meteor shower!

The Geminids are a strange meteor shower. People have known about most of the big meteor showers for many, many years. But not the Geminids! The first time anyone noticed the Geminids was in 1862. At that time, there were only about 15 meteors per hour in the Geminids. Astronomers started looking for the comet that the Geminids came from. They couldn’t find one! Finally, in 1983 a satellite named IRAS (Infrared Astronomical Satellite) discovered an object in the right orbit to make the Geminids. The object is named 3200 Phaethon. The strange object looks more like an asteroid than a comet. Maybe 3200 Phaethon is an asteroid that crashed into another asteroid, making a cloud of dust and small rocks. Maybe that cloud is what makes the Geminid meteor shower. Or maybe 3200 Phaethon isn’t an asteroid after all. Maybe it is an old, “dead” comet that has lost all of its ice. Scientists aren’t quite sure which is true.

source: windows to the universe

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