Meteor Activity Outlook for September 24-30, 2011

The following is a slightly edited version of Bob Lunsford’s excellent weekly summary of meteor activity. The original version can be found at the American Meteor Society’s site.

September offers longer nights in the northern hemisphere that tend to be less hazy than those experienced in mid-summer. In the sky, no major showers are visible from either hemisphere but the northern hemisphere enjoys the advantage of higher sporadic rates. Most of the shower activity this month is produced from the Perseus-Aurigid complex active this time of year. These showers rarely produce more than five meteors per hour but still manage to produce most of the shower activity seen this month. Unfortunately the Perseus-Aurigid complex lies too low in the northern sky for southern hemisphere observers to view very well. Video studies have shown that the Southern Taurids are visible as early as September 7th therefore after this date the Antihelion radiant will no longer be listed until the Taurid showers end in December. The Antihelion meteors are still active but their radiant is superimposed upon that of the more numerous Taurids, therefore it is impossible to properly separate these meteors. Observers in the southern hemisphere suffer from some of their lowest rates of the year this month. The Southern Taurid radiant is not too badly placed so observers south can expect to see a little of this activity this month.

During this period the moon reaches its new phase on Tuesday September 27th. At this time the moon will lie near the sun and will not be visible at night. This weekend the waning crescent moon will rise during the late morning hours but will not interfere with meteor observing. The estimated total hourly rates for evening observers this week is near four as seen from the northern hemisphere and three as seen from the southern hemisphere. For morning observers the estimated total hourly rates should be near eleven as seen from mid-northern latitudes and six from mid-southern latitudes. The actual rates will also depend on factors such as personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity.

The radiant (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday night/Sunday morning September 24/25. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.

The following showers are expected to be active this week:

The Southern Taurid (STA) radiant is now centered at 01:16 (019) +06. This area of the sky lies on the Pisces/Cetus border, six degrees southeast of the fourth magnitude star Epsilon Piscium. This radiant is best placed near 0200 local daylight time (LDT), when it lies on the meridian and is located highest in the sky. Rates at this time should be near one per hour no matter your location. With an entry velocity of 27 km/sec., the average Southern Taurid meteor would be of medium-slow speed. While looking at this area of the sky, notice how bright the variable star Mira (Omicron Ceti) is these nights. It normally is too dim to be seen with the naked eye but now stands at second magnitude, nearly the brightest star in the constellation of Cetus the whale. It lies approximately fifteen degrees southeast from the center of the STA radiant or just six degrees southeast of the fourth magnitude star Al Rischa (Alpha Piscium). It is probably near peak magnitude and will soon begin fading.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately ten sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near three per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near five per hour as seen from rural observing sites and two per hour during the evening hours. Locations between these two extremes would see activity between the listed figures.

The list below presents a condensed version of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning.

Shower Name                 RA     DEC   Vel     Rates
                                         km/s   NH    SH
STA Southern Taurids      01h 16m  +06    27     1     1

RA - Right Ascension
DEC - Declination
Vel - Velocity relative to Earth (in km per sec)
Rates - Rate of visible meteors per hour from a dark site
NH - Northern Hemisphere
SH - Southern Hemisphere

Meteor Activity Outlook for September 17-23, 2011

The following is a slightly edited version of Bob Lunsford’s excellent weekly summary of meteor activity. The original version can be found at the American Meteor Society’s site.

September offers longer nights in the northern hemisphere that tend to be less hazy than those experienced in mid-summer. In the sky, no major showers are visible from either hemisphere but the northern hemisphere enjoys the advantage of higher sporadic rates. Most of the shower activity this month is produced from the Perseus-Aurigid complex active this time of year. These showers rarely produce more than five meteors per hour but still manage to produce most of the shower activity seen this month. Unfortunately the Perseus-Aurigid complex lies too low in the northern sky for southern hemisphere observers to view very well. Video studies have shown that the Southern Taurids are visible as early as September 7th therefore after this date the Antihelion radiant will no longer be listed until the Taurid showers end in December. The Antihelion meteors are still active but their radiant is superimposed upon that of the more numerous Taurids, therefore it is impossible to properly separate these meteors. Observers in the southern hemisphere suffer from some of their lowest rates of the year this month. The Southern Taurid radiant is not too badly placed so observers south can expect to see a little of this activity this month.

During this period the moon reaches its last quarter phase on Tuesday September 20th. At this time the moon will lie ninety degrees west of the sun and will rise near 0100 local daylight time (LDT) as seen from mid-northern latitudes. This weekend the waning gibbous moon will interfere with meteor observing during the morning hours. Skies will be dark during the early evening hours until moon rise, which will occur during the late evening hours. It would be better to wait until later this week to view meteor activity, when the moon becomes less bothersome. The estimated total hourly rates for evening observers this week is near four as seen from the northern hemisphere and two as seen from the southern hemisphere. For morning observers the estimated total hourly rates should be near nine as seen from mid-northern latitudes and six from mid-southern latitudes. The actual rates will also depend on factors such as personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity. Morning rates are reduced due to moonlight.

The radiant (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday night/Sunday morning September 17/18. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.

The following showers are expected to be active this week:

The Southern Taurid (STA) radiant is now centered at 01:08 (017) +05. This area of the sky lies in southern Pisces, three degrees north of the fourth magnitude star Epsilon Piscium. This radiant is best placed near 0200 LDT, when it lies on the meridian and is located highest in the sky.  Rates at this time should be near two per hour no matter your location. With an entry velocity of 27 km/sec., the average Southern Taurid meteor would be of medium-slow speed.

Many radiants in the region of Eridanus have been suspected this time of year. Recent studies of the IMO’s video database by Sirko Molau and Juergen Rendtel has verified a radiant active in Eridanus from September 3rd through the 24th with maximum activity occurring on the 7th. The Nu Eridanid (NUE) radiant is currently located at 04:53 (073) +06. This position lies in western Orion near the third magnitude star Pi 3 Orionis. The radiant is best placed during the last hour before the start of morning twilight. Rates may be close to one per hour this week. With an entry velocity of 68 km/sec., most activity from this radiant would be swift. With the radiant lying close to the celestial equator, these meteors are seen equally well from both hemispheres.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately six sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near three per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near three per hour as seen from rural observing sites and one per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Morning rates are reduced by moonlight.

The list below presents a condensed version of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning.

Shower Name                 RA     DEC   Vel     Rates
                                         km/s   NH    SH
STA Southern Taurids      01h 08m  +05    27     2     2
NUE nu Eridanids          04h 53m  +06    68     1     1

RA - Right Ascension
DEC - Declination
Vel - Velocity relative to Earth (in km per sec)
Rates - Rate of visible meteors per hour from a dark site
NH - Northern Hemisphere
SH - Southern Hemisphere

Southwest US Fireball – September 14

A brilliant fireball was observed over southern California, Nevada, Arizona and Sonora on Wednesday evening, September 14. Hundreds of reports have been submitted to the American Meteor Society, and even a few to this blog. The best site for learning more about this event and other fireball events is at the American Meteor Society. Their page dedicated to this fireball (including a map of all reported eyewitnesses) can be found here.

An eyewitness in southern California was able to get a video of the event.

Down in Hermosillo, Sonora, Mexico, Salvador Aguirre picked up the fireball on his all-sky camera. In the image below, the fireball is seen low on the horizon to the NNW of Hermosillo.

September 14 fireball seen from Hermosillo, Mexico. Image taken by Salvador Aguirre with his all-sky meteor camera. Credit: Salvador Aguirre.

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So what caused the fireball? Most likely it was a small asteroid, no bigger than a basketball, hitting the upper atmosphere at 20-40 km per second. Based on the behavior of similar objects, it first became visible at an altitude of ~90 km and ceased to be visible at an altitude of ~20-30 km. Though some material may have survived to impact the ground as small meteorites, at least 90% or more of the asteroid burned up in flight.

Long time… no blog…

It has been a long time since I’ve updated the Transient Sky blog. I’ll update everyone with more details later. In the meantime, all is well with me. I just ran out of time this summer to keep the blog up to date. A new (or newish) job and 1 year old twin boys will do that.

Meteor Activity Outlook for September 10-16, 2011

The following is a slightly edited version of Bob Lunsford’s excellent weekly summary of meteor activity. The original version can be found at the American Meteor Society’s site.

September offers longer nights in the northern hemisphere that tend to be less hazy than those experienced in mid-summer. In the sky, no major showers are visible from either hemisphere but the northern hemisphere enjoys the advantage of higher sporadic rates. Most of the shower activity this month is produced from the Perseus-Aurigid complex active this time of year. These showers rarely produce more than five meteors per hour but still manage to produce most of the shower activity seen this month. Unfortunately the Perseus-Aurigid complex lies too low in the northern sky for southern hemisphere observers to view very well. Video studies have shown that the Southern Taurids are visible as early as September 7th therefore after this date the Antihelion radiant will no longer be listed until the Taurid showers end in December. The Antihelion meteors are still active but their radiant is superimposed upon that of the more numerous Taurids, therefore it is impossible to properly separate these meteors. Observers in the southern hemisphere suffer from some of their lowest rates of the year this month. The Southern Taurid radiant is not too badly placed so observers south can expect to see a little of this activity this month.

Meteor season finally gets going in July for the northern hemisphere. The first half of the month will be much like June. After the 15th though, both sporadic and shower rates increase significantly. For observers in the southern hemisphere, sporadic rates will be falling but the overall activity will increase with the arrival of the Delta Aquariids.

During this period the moon reaches its full phase on Monday September 12th. At this time the moon will lie opposite the sun and will be in the sky all night long. This is the worst time to try and view meteor activity this month as the intense moonlight will obscure all but the brightest meteors. Conditions will not improve until the moon wanes to its last quarter phase and does not rise until near 0100 local daylight time (LDT). The estimated total hourly rates for evening observers this week is near two as seen from the northern hemisphere and one as seen from the southern hemisphere. For morning observers the estimated total hourly rates should be near eight as seen from mid-northern latitudes and five from mid-southern latitudes. The actual rates will also depend on factors such as personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity. Rates are reduced during this period due to the intense moonlight.

The radiant (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday night/Sunday morning September 11/12. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.

Detailed descriptions of the active showers will continue next week when the moonlight conditions will be more favorable. The following showers are expected to be active this week. Rates and positions are exact for Saturday night/Sunday morning.

Shower Name                  RA     DEC   Vel     Rates
                                          km/s   NH    SH
STA Southern Taurids       00h 48m  +03    27     1     1
SIC Sept Iota Cassiopeiids 02h 27m  +64    50    <1    <1
SPE Sept Epsilon Perseids  03h 12m  +41    66    <1    <1
NUE Nu Eridanids           04h 36m  +03    68     1     1

RA - Right Ascension
DEC - Declination
Vel - Velocity relative to Earth (in km per sec)
Rates - Rate of visible meteors per hour from a dark site
NH - Northern Hemisphere
SH - Southern Hemisphere
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