Post by founder on May 1, 2007 15:33:51 GMT -5
There are many meteor showers in summer. You don't have to wait for the popular Perseids of August to see meteors.
Most meteor observers are tempted to take the summer off. Even though viewers can be a little more comfortable in the warmer weather, there seems little to offer until the major meteor shower of the year, the Perseids, occurs in August. The most casual observers know that August is Meteor Month even if they don’t know the names of the showers.
Watching the sky is never completely unfruitful though. The months of May, June and July have minor showers and even on the slowest night there is sporadic activity. You may be lucky enough to see fireballs, bolides or even a reentering satellite. If you choose to observe on a night in early summer when activity may be slight, it helps to know a little about meteors and some special techniques for observing them.
A meteor is the streak of light, the shooting star. A meteoroid is the small body that produces the streak of light. The average meteoroid is tiny, the size of a grain of sand and of very low density. Think of the tiniest chunk of instant coffee (grain of sand size) hitting the earth’s atmosphere at about 70 kilometers per second and burning up. Meteoroids are dust particles left from comets as they come close to the sun. The dust particles follow the orbit in parallel paths eventually making a complete loop of dust. Meteor showers occur when the earth passes through this stream of dust and debris. The meteors seem to come from one small area of the sky through a trick of perspective. This small area is called the radiant. The shower is named for the constellation where the radiant is, not the parent comet. If there is more than one radiant, the nearby star is added to the name. Meteor showers are rated for how many meteors per hour are expected. This rate, called the ZHR or zenithal hourly rate is calculated using perfect conditions so you probably will never see as many meteors as the ZHR predicts. Sporadic meteors are meteors that can’t be shown to belong to a shower. On just about any night you can see 3-8 sporadic meteors per hour. The luminous glow left from the meteor's passage is called the train.
Occasionally, the meteoroid is substantially larger than usual and produces a fireball. A small number of meteoroids are not comet debris but asteroids. These may produce fireballs and meteorites, meteoroids that reach the earth. Bolides are very exciting. They are fireballs that are accompanied by noise.
Reentering satellites are much slower than meteors, last much longer and usually have fluctuations in brightness.
Observing Tips
Observe on a moonless night away from light pollution. Early morning is the best time.
Know which shower is active and where the radiant is. If you don’t know the constellations, have someone show you. Don’t look right at the radiant. There are meteors there but they might be easy to miss, showing very short streaks of light or maybe just a brief flaring point of light. Instead, look about 40 degrees to one side of the radiant.
Use recliners to prevent a crick in the neck. Dress warmly. It’s warmer in summer but not that much warmer. Carry a red flashlight to save your night vision.
The Showers
Eta Aquarids are active April 19- May 28. The maximum can occur anytime between May 2 and May 10. These are particles of Halley’s Comet. In the Northern Hemisphere meteors are mainly during the day but just before dawn observers may see 20 per hour. The Southern Hemisphere is better; the rate per hour (ZHR) is 60. Meteors are fast, 60-65 kilometers per second (km/s) with long trains.
Saggitarids are several minor showers active April 15- July 15. There are several maximums, May 19 being well known. Meteors are slow, 30 km/s and the ZHR is 5.
Tau Herculids are active May 19- June 14. These meteors are very slow, 15 km/s and the ZHR is zero. Expect to see at most 3 per night. They are slower than sporadic meteors.
Pegasids are active for a short time, July 7- July 13 with the maximum occurring on July 10. Meteors are very fast, 70 km/s and faint. The ZHR is 3.
Aquarids active in July and August have several radiants. The S. Delta Aquarids active July 12- August 19 with a maximum July 28, is the strongest radiant of the group and provides most of the activity. The other radiants are: S. Iota Aquarids active July 25- August 15, N. Delta Aquarids active July 15- August 25 and the N. Iota Aquarids active August 11- August 31. The combined count of these showers is 30 per hour. The average meteor is faint, medium speed 34-42 km/s, with long paths.
Capricornids and Alpha Capricornids are active July 3- August 15 with a broad maximum occurring the last week of July and the first week of August. The meteors are slow 23 km/s. Capricornids are noted for fireballs and bright, often yellowish-blue and some red meteors. Unfortunately there aren’t very many of them. The ZHR is only 5.
The most popular and dependable meteor shower of the year in the Northern Hemisphere is the Perseids. Active July 17- August 24, the maximum occurs August 12. . The parent comet 109P/Swift-Tuttle’s return to the solar system in 1992 produced rates of 200-400 meteors per hour. The meteors are fast 60 km/s, with a high proportion of bright ones with persistent trains, fireballs and even some purple sparks. The normal (no comet) ZHR is 80. Many other showers are active during this time.
Kappa Cygnids are active August 3- August 25 with the maximum occurring August 17. Very little is known about this shower because of the low activity. ZHR is reported as 3 but 3 per night is probably more accurate. The meteors are slow 25 km/s and medium bright. It ‘s been proposed that this shower is a fireball shower with a period of about 6-7 years.
Alpha Aurigids are active August 25- September 5. Make sure you are awake, observing on the morning of August 31 because the maximum occurs then for only one hour. You may see up to 50 meteors radiating from the pentagon of Auriga. The meteors are fast 66 km/s, bright with long lasting trains. If you sleep through the maximum, expect to see at most 10 per hour.
As you can see, you don’t have to wait for August- Meteor Month.
Would you like to turn casual observing into scientific contributions? Amateurs as well as professionals commonly neglect meteor observing and observers are encouraged to report their data. You will have to learn some more terms and observational techniques as well as keep records, but there are two organizations willing to help.
The North American Meteor Network (NAMN) recruits new observers and provides training. The International Meteor Organization provides guidance and standards for worldwide observations. Both organizations encourage participation.
Most meteor observers are tempted to take the summer off. Even though viewers can be a little more comfortable in the warmer weather, there seems little to offer until the major meteor shower of the year, the Perseids, occurs in August. The most casual observers know that August is Meteor Month even if they don’t know the names of the showers.
Watching the sky is never completely unfruitful though. The months of May, June and July have minor showers and even on the slowest night there is sporadic activity. You may be lucky enough to see fireballs, bolides or even a reentering satellite. If you choose to observe on a night in early summer when activity may be slight, it helps to know a little about meteors and some special techniques for observing them.
A meteor is the streak of light, the shooting star. A meteoroid is the small body that produces the streak of light. The average meteoroid is tiny, the size of a grain of sand and of very low density. Think of the tiniest chunk of instant coffee (grain of sand size) hitting the earth’s atmosphere at about 70 kilometers per second and burning up. Meteoroids are dust particles left from comets as they come close to the sun. The dust particles follow the orbit in parallel paths eventually making a complete loop of dust. Meteor showers occur when the earth passes through this stream of dust and debris. The meteors seem to come from one small area of the sky through a trick of perspective. This small area is called the radiant. The shower is named for the constellation where the radiant is, not the parent comet. If there is more than one radiant, the nearby star is added to the name. Meteor showers are rated for how many meteors per hour are expected. This rate, called the ZHR or zenithal hourly rate is calculated using perfect conditions so you probably will never see as many meteors as the ZHR predicts. Sporadic meteors are meteors that can’t be shown to belong to a shower. On just about any night you can see 3-8 sporadic meteors per hour. The luminous glow left from the meteor's passage is called the train.
Occasionally, the meteoroid is substantially larger than usual and produces a fireball. A small number of meteoroids are not comet debris but asteroids. These may produce fireballs and meteorites, meteoroids that reach the earth. Bolides are very exciting. They are fireballs that are accompanied by noise.
Reentering satellites are much slower than meteors, last much longer and usually have fluctuations in brightness.
Observing Tips
Observe on a moonless night away from light pollution. Early morning is the best time.
Know which shower is active and where the radiant is. If you don’t know the constellations, have someone show you. Don’t look right at the radiant. There are meteors there but they might be easy to miss, showing very short streaks of light or maybe just a brief flaring point of light. Instead, look about 40 degrees to one side of the radiant.
Use recliners to prevent a crick in the neck. Dress warmly. It’s warmer in summer but not that much warmer. Carry a red flashlight to save your night vision.
The Showers
Eta Aquarids are active April 19- May 28. The maximum can occur anytime between May 2 and May 10. These are particles of Halley’s Comet. In the Northern Hemisphere meteors are mainly during the day but just before dawn observers may see 20 per hour. The Southern Hemisphere is better; the rate per hour (ZHR) is 60. Meteors are fast, 60-65 kilometers per second (km/s) with long trains.
Saggitarids are several minor showers active April 15- July 15. There are several maximums, May 19 being well known. Meteors are slow, 30 km/s and the ZHR is 5.
Tau Herculids are active May 19- June 14. These meteors are very slow, 15 km/s and the ZHR is zero. Expect to see at most 3 per night. They are slower than sporadic meteors.
Pegasids are active for a short time, July 7- July 13 with the maximum occurring on July 10. Meteors are very fast, 70 km/s and faint. The ZHR is 3.
Aquarids active in July and August have several radiants. The S. Delta Aquarids active July 12- August 19 with a maximum July 28, is the strongest radiant of the group and provides most of the activity. The other radiants are: S. Iota Aquarids active July 25- August 15, N. Delta Aquarids active July 15- August 25 and the N. Iota Aquarids active August 11- August 31. The combined count of these showers is 30 per hour. The average meteor is faint, medium speed 34-42 km/s, with long paths.
Capricornids and Alpha Capricornids are active July 3- August 15 with a broad maximum occurring the last week of July and the first week of August. The meteors are slow 23 km/s. Capricornids are noted for fireballs and bright, often yellowish-blue and some red meteors. Unfortunately there aren’t very many of them. The ZHR is only 5.
The most popular and dependable meteor shower of the year in the Northern Hemisphere is the Perseids. Active July 17- August 24, the maximum occurs August 12. . The parent comet 109P/Swift-Tuttle’s return to the solar system in 1992 produced rates of 200-400 meteors per hour. The meteors are fast 60 km/s, with a high proportion of bright ones with persistent trains, fireballs and even some purple sparks. The normal (no comet) ZHR is 80. Many other showers are active during this time.
Kappa Cygnids are active August 3- August 25 with the maximum occurring August 17. Very little is known about this shower because of the low activity. ZHR is reported as 3 but 3 per night is probably more accurate. The meteors are slow 25 km/s and medium bright. It ‘s been proposed that this shower is a fireball shower with a period of about 6-7 years.
Alpha Aurigids are active August 25- September 5. Make sure you are awake, observing on the morning of August 31 because the maximum occurs then for only one hour. You may see up to 50 meteors radiating from the pentagon of Auriga. The meteors are fast 66 km/s, bright with long lasting trains. If you sleep through the maximum, expect to see at most 10 per hour.
As you can see, you don’t have to wait for August- Meteor Month.
Would you like to turn casual observing into scientific contributions? Amateurs as well as professionals commonly neglect meteor observing and observers are encouraged to report their data. You will have to learn some more terms and observational techniques as well as keep records, but there are two organizations willing to help.
The North American Meteor Network (NAMN) recruits new observers and provides training. The International Meteor Organization provides guidance and standards for worldwide observations. Both organizations encourage participation.
