Jim Colyer
A meteor shower is a phenomenon in which meteors emanate from a point in the sky called a radiant. Most meteors are no larger than grains of sand. They come from streams of debris left behind by comets. When the earth's orbit intersects with a stream of "meteoroids," showers occur.
Meteors travel in parallel paths. That is why they appear to radiate from a single point. It's a matter of perspective. Meteor showers are named after the constellations their radiants are in. Radiants cross the sky as the earth spins.
More meteors are seen in the wee hours because we are on the leading side of the planet.
Meteors heat up when they enter the atmosphere. A temperature of 3,000 degrees is reached. Most meteors are vaporized about 50 miles above us.
The words "fireball" and "bolide" can be used interchangeably. The International Astronomical Union IAU defines a fireball as a meteor that is is brighter than Venus. A bolide is a very bright fireball.
The American Meteor Society keeps track of meteor activity.
http://www.amsmeteors.org/
Seven major meteor showers:
QUADRANTIDS - Peak the night of January 3
Only the most avid meteor buffs will be outside on a cold night in January. And if the name of this shower looks strange, it is because it is named after an extinct constellation. Its radiant is in the constellation Bootes. Its meteroid stream is narrow, and high northern latitudes like Sweden offer the best observation. Quadrantids are medium-paced and generally faint.
LYRIDS - Peak the night of April 21
Associated with Comet Thatcher, the Lyrids were observed as early as 687 BC by the Chinese. The earth crosses the stream the night of April 21. It is a modest shower whose radiant is near the first magnitude star Vega. The Lyrids flared up in 1982, producing 90 meteors per hour.
ETA AQUARIDS - Peak the night of May 5
These meteors are associated with Halley's Comet. Their radiant is in the constellation Aquarius near the star Eta Aquarii. Some meteor showers are named for stars close to their radiants. This radiant rises about an hour before dawn in the northern hemisphere. Australians get a better view since Aquarius is higher in the sky. They may see up to 40 meteors an hour.
PERSEIDS - Peak the night of August 11
The Perseids is the best meteor shower because of its numbers and because of the warm weather. It can be cloudy, however, and the moon can interfere. The action starts around midnight when the earth has turned in the right direction. The Perseids peak before dawn as its radiant rises in the sky. A meteor is seen once every minute. They are fast. Trace them backward, and they will originate from a point near Perseus' head. Counting meteors is a lazy man's sport. All you need is a lawn chair and some mosquito repellant. Look for dark skies in the open with as few trees as possible.
The Perseids are associated with the comet Swift-Tuttle. Debris stretches all along its orbit. Swift-Tuttle last approached the earth in 1992. It returns every 130 years. The Perseids begin on July 23 and continue through August 20. Tiny pea-like bits enter earth's atmosphere at 25 miles per second. The Perseids were observed as far back as 36 AD by the Chinese.
ORIONIDS - Peak the night of October 20
Still another shower passing through the dust of Halley's Comet, the Orionids favor observers in the Southern Hemisphere. The radiant is not far from Betelgeuse. Orionids are beautiful because they occur against the background of the bright winter stars. E.C. Herrick is credited with their discovery in 1839.
LEONIDS - Peak the night of November 17
The Leonids are associated with comet Temple-Tuttle. They peak on the night of November 17, which is a shame because this can be a prolific shower and cold weather acts as a deterrent. Its radiant is in Leo, inside the sickle. The Leonids are famous for meteor storms, outbursts of 1000 or more meteors per hour. The 1833 meteor storm was so intense that people thought it was the end of the world. Joseph Smith, the founder of Mormonism, thought it heralded the second coming of Jesus. The Leonids repeated their grand show in 1866, and it happened again a century later in 1966, I was at Lindsey Wilson College in Columbia, Kentucky, and completely unaware of it. The Leonids have been traced back to 902 AD.
GEMINIDS - Peak the night of December 13
The Geminids are caused by an asteroid rather than a comet. They are slow moving and thought to be on the increase. The radiant is near Castor in Gemini. 50-70 meteors an hour are possible. Again, cold nights tend to discourage.
Meteors travel in parallel paths. That is why they appear to radiate from a single point. It's a matter of perspective. Meteor showers are named after the constellations their radiants are in. Radiants cross the sky as the earth spins.
More meteors are seen in the wee hours because we are on the leading side of the planet.
Meteors heat up when they enter the atmosphere. A temperature of 3,000 degrees is reached. Most meteors are vaporized about 50 miles above us.
The words "fireball" and "bolide" can be used interchangeably. The International Astronomical Union IAU defines a fireball as a meteor that is is brighter than Venus. A bolide is a very bright fireball.
The American Meteor Society keeps track of meteor activity.
http://www.amsmeteors.org/
Seven major meteor showers:
QUADRANTIDS - Peak the night of January 3
Only the most avid meteor buffs will be outside on a cold night in January. And if the name of this shower looks strange, it is because it is named after an extinct constellation. Its radiant is in the constellation Bootes. Its meteroid stream is narrow, and high northern latitudes like Sweden offer the best observation. Quadrantids are medium-paced and generally faint.
LYRIDS - Peak the night of April 21
Associated with Comet Thatcher, the Lyrids were observed as early as 687 BC by the Chinese. The earth crosses the stream the night of April 21. It is a modest shower whose radiant is near the first magnitude star Vega. The Lyrids flared up in 1982, producing 90 meteors per hour.
ETA AQUARIDS - Peak the night of May 5
These meteors are associated with Halley's Comet. Their radiant is in the constellation Aquarius near the star Eta Aquarii. Some meteor showers are named for stars close to their radiants. This radiant rises about an hour before dawn in the northern hemisphere. Australians get a better view since Aquarius is higher in the sky. They may see up to 40 meteors an hour.
PERSEIDS - Peak the night of August 11
The Perseids is the best meteor shower because of its numbers and because of the warm weather. It can be cloudy, however, and the moon can interfere. The action starts around midnight when the earth has turned in the right direction. The Perseids peak before dawn as its radiant rises in the sky. A meteor is seen once every minute. They are fast. Trace them backward, and they will originate from a point near Perseus' head. Counting meteors is a lazy man's sport. All you need is a lawn chair and some mosquito repellant. Look for dark skies in the open with as few trees as possible.
The Perseids are associated with the comet Swift-Tuttle. Debris stretches all along its orbit. Swift-Tuttle last approached the earth in 1992. It returns every 130 years. The Perseids begin on July 23 and continue through August 20. Tiny pea-like bits enter earth's atmosphere at 25 miles per second. The Perseids were observed as far back as 36 AD by the Chinese.
ORIONIDS - Peak the night of October 20
Still another shower passing through the dust of Halley's Comet, the Orionids favor observers in the Southern Hemisphere. The radiant is not far from Betelgeuse. Orionids are beautiful because they occur against the background of the bright winter stars. E.C. Herrick is credited with their discovery in 1839.
LEONIDS - Peak the night of November 17
The Leonids are associated with comet Temple-Tuttle. They peak on the night of November 17, which is a shame because this can be a prolific shower and cold weather acts as a deterrent. Its radiant is in Leo, inside the sickle. The Leonids are famous for meteor storms, outbursts of 1000 or more meteors per hour. The 1833 meteor storm was so intense that people thought it was the end of the world. Joseph Smith, the founder of Mormonism, thought it heralded the second coming of Jesus. The Leonids repeated their grand show in 1866, and it happened again a century later in 1966, I was at Lindsey Wilson College in Columbia, Kentucky, and completely unaware of it. The Leonids have been traced back to 902 AD.
GEMINIDS - Peak the night of December 13
The Geminids are caused by an asteroid rather than a comet. They are slow moving and thought to be on the increase. The radiant is near Castor in Gemini. 50-70 meteors an hour are possible. Again, cold nights tend to discourage.