Meteor Activity Outlook for April 30 – May 6, 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.

May is a fairly slow month for meteor activity. The Eta Aquariids are very active the first two weeks of the month then fade as the month progresses. The only other showers active this month are the weak Nu Cygnids, the Eta Lyrids, and the Antihelion radiant. These will add only 1-2 meteors per hour to the total count. Sporadic rates are low but steady as seen from the mid-northern hemisphere (45 N). Sporadic rates seen from the mid-southern hemisphere (45 S) are strong but beginning to decline.

During this period the moon reaches its new phase on Tuesday May 3. At this time the moon will lie near the sun and will not be visible at night. Toward the end of this period a waxing crescent moon will enter the evening sky but will not interfere with observing. The estimated total hourly rates for evening observers this week is near three as seen from the northern hemisphere and four as seen from the southern hemisphere. For morning observers the estimated total hourly rates should be near fourteen from the northern hemisphere and twenty as seen from south of the equator. 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 April 30/May 1. 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 wide Antihelion (ANT) radiant is now centered at 15:32 (233) -19. This area of the sky lies in eastern Libra, eight degrees northwest of the second magnitude star Dschubba (Delta Scorpii). This radiant is best placed near 0200 local daylight time (LDT) when it lies on the meridian and is located highest in the sky. Due to the large size of this radiant, any meteor radiating from extreme eastern Hydra, Libra, northern Lupus, or western Scorpius could be a candidate for this shower. Rates at this time should be near two per hour as seen from the northern hemisphere and three per hour as seen from south of the equator. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of medium-slow speed.

The team of Sirko Molau and Juergen Rendtel have discovered a weak radiant active at this time in the constellation of Cygnus. Video data shows that the Nu Cygnids (NCY) are active from April 18th through May 7th. Maximum activity occurred on the morning of April 20th. The radiant is currently located at 21:40 (325) +47. This position lies in northeastern Cygnus, just north of the faint star known as Rho Cygni. The radiant is best placed during the last dark hour before dawn, when it lies highest above the horizon in a dark sky. At 42km/sec. the Nu Cygnids would produce meteors of medium velocity. Expected rates are less than one per hour. Due to the northerly declination of the radiant, these meteors are not well seen from south of the equator.

The Eta Aquariids (ETA) are particles from Halley’s Comet, produced in Earth-crossing orbits many centuries ago. We pass closest to these orbits from May 5 through the 9th. During this period the Eta Aquariids are at their best, capable of producing ZHR’s of sixty. The actual visible rates are most often less than half this figure due to the low altitude of the radiant at dawn. Observed hourly rates at maximum normally vary from zero at 60 degrees north latitude to 30 near the equator and back down to near zero again in Antarctica, where the radiant elevation is very low. Hourly rates this weekend are anywhere from zero to five per hour depending on your latitude and observing conditions. Rates will increase significantly as the week progresses as we approach the May 7 maximum. The radiant is currently located at 22:20 (335) -03. This area of the sky is located in northern Aquarius, just south of the fourth magnitude star Gamma Aquarii. The best time to view this activity is during the hour before the start of morning twilight, when the radiant lies highest in a dark sky. No matter your location these meteors will appear from the eastern sky and shoot in all directions. If the radiant has sufficient altitude Eta Aquariid meteors can also be seen shooting down toward the eastern horizon. With an entry velocity of 67 kilometers per second, a majority of these meteors will appear to move swiftly with a high percentage of the bright meteors leaving persistent trains. Surprisingly, this shower produces very few fireballs.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately nine sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near two per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near fourteen per hour as seen from rural observing sites and three 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
ANT Antihelions           15h 32m  -19    30     2     3
NCY Nu Cygnids            21h 40m  +47    42    <1    <1
ETA Eta Aquariids         22h 20m  -03    67     2     3

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 April 23-29, 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.

Meteor activity picks up a bit during April as two major showers are active during the month. The first of these, the Lyrids, are active from the 16th through the 25th, with a pronounced maximum on the 22nd. The Eta Aquariids start appearing near the 28th and reach maximum activity during the first week in May. Sporadic rates are low but steady as seen from the mid-northern hemisphere (45 N). Sporadic rates seen from the mid-southern hemisphere (45 S) rise this month toward a maximum in July.

During this period the moon reaches its last quarter phase on Monday April 25. At this time the moon will lie ninety degrees east of the sun and will rise near 0100 LDT (Local Daylight Time) for those situated in the mid-northern latitudes. While the moonlight will cause interference for meteor observing, the effects will be much less than when the moon is near its full phase. The estimated total hourly rates for evening observers this week is near two 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 nine from the northern hemisphere and twelve as seen from south of the equator. 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 April 23/24. 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 elusive Pi Puppids (PPU) are now active from a radiant located at 07:20 (110) -45. This area of the sky lies in south-central Puppis near the third magnitude star Sigma Puppis. This radiant is best placed as soon as it becomes dark as it culminates during the afternoon hours when the sun is still above the horizon. These meteors are nearly non-existent away from the night of April 24th. Even on that night it would be lucky to spot just one, especially from the northern hemisphere, where the radiant lies low in the southwest at dusk. This shower has produced outbursts in the past so it should be monitored whenever possible, especially from the southern hemisphere. With an entry velocity of only 18 km/sec., the average Pi Puppid meteor would crawl through the sky at a snails pace.

Studies of the IMO video database by Sirko Molau and Juergen Rendtel has revealed a weak radiant active at this time in the constellation of Virgo. Video data shows that the Sigma Leonids (SLE) are active from April 18th through the 25th with maximum activity falling on the 21st. The radiant is currently located at 13:46 (207) +04. This position lies in eastern Virgo, five degrees northwest of the fourth magnitude star Tau Virginis. The radiant is best placed near midnight LDT, when it lies highest above the horizon. At 20km/sec. the Sigma Leonids would produce obvious, slow meteors. Expected rates are less than one per hour no matter your location.

There is also a second new radiant active in Virgo this time of year. Video data shows that the h Virginids (HVR) are active from April 22-25 with maximum activity occurring on the 22nd. On the evening of the 21st (22nd UT), the radiant is located at 14:16 (214) -11. This position lies on the Virgo/Libra border, two degrees southeast of the fourth magnitude star Kappa Virginis. The radiant is best placed near 0200 LDT, when it lies on the meridian and is highest above the horizon. At 24km/sec. the h Virginids would produce more slow meteors. Expected rates would also be less than one per hour no matter your location.

The wide Antihelion (ANT) radiant is now centered at 15:04 (226) -18. This area of the sky lies in central Libra, four degrees southeast of the third magnitude star Zubenelgenubi (Alpha Librae). This radiant is best placed near 0200 LDT when it lies on the meridian and is located highest in the sky. Due to the large size of this radiant, any meteor radiating from Libra, extreme eastern Hydra, northern Lupus, or western Scorpius could be a candidate for this shower. Rates at this time should be near one per hour as seen from the northern hemisphere and two per hour as seen from south of the equator. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of medium-slow speed.

The major shower known as the Lyrids (LYR) are active from April 16th through the 25th. Maximum activity occurs on the 23rd. The radiant is currently located at 18:13 (273) +32. This position lies on Hercules/Lyra border, nine degrees southwest of the brilliant blue-white zero magnitude magnitude star known as Vega (Alpha Lyrae). The radiant is best placed during the last dark hour before dawn, when it lies highest above the horizon. At 48km/sec. the Lyrids would produce meteors of medium velocity. Expected rates this weekend are near two per hour during the last dark hour before dawn. Due to the northerly declination of the radiant, these meteors are not well seen from high southern latitudes.

The team of Sirko Molau and Juergen Rendtel have a third weak radiant active at this time in the constellation of Cygnus. Video data shows that the Nu Cygnids (NCY) are active from April 18th through May 7th. Maximum activity occurred on the morning of April 20th. The radiant is currently located at 20:50 (312) +42. This position lies in central Cygnus, three degrees south of the first magnitude star Deneb (Alpha Cygni). The radiant is best placed during the last dark hour before dawn, when it lies highest above the horizon in a dark sky. At 42km/sec. the Nu Cygnids would produce meteors of medium velocity. Expected rates are near one per hour during the last dark hour before dawn. Due to the northerly declination of the radiant, these meteors are not well seen from south of the equator.

Activity from the Eta Aquariids (ETA) may be seen late next week. This major shower is active from April 28 through May 21. This shower is caused by particles from Halley’s Comet, produced in Earth-crossing orbits many centuries ago. We pass closest to these orbits from May 5 through the 9th. During this period the Eta Aquariids are at their best, capable of producing ZHR’s of seventy. The actual visible rates are most often less than half this figure due to the low altitude of the radiant at dawn. Observed hourly rates at maximum normally vary from zero at 60 degrees north latitude to 25 near the equator and back down to near zero again in Antarctica, where the radiant elevation is very low. Hourly rates this week are anywhere from zero to two per hour depending on your latitude and observing conditions. Rates will increase significantly as we approach the May 7 maximum. On April 28, the radiant will be located at 22:12 (333) -04. This area of the sky is located in northern Aquarius, three degrees southwest of the fourth magnitude star Gamma Aquarii. The best time to view this activity is just before the start of morning twilight, when the radiant lies highest in a dark sky. No matter your location these meteors will appear from the eastern sky and shoot in all directions. If the radiant has sufficient altitude Eta Aquariid meteors can also be seen shooting down toward the eastern horizon. With an entry velocity of 67 kilometers per second, a majority of these meteors will appear to move swiftly with a high percentage of the bright meteors leaving persistent trains. Surprisingly, this shower produces very few fireballs.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately nine sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near one per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near fourteen 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. Evening rates are reduced due to 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
PPU Pi Puppids            07h 20m  -45    18    <1    <1
SLE Sigma Leonids         13h 46m  +04    20    <1    <1
HVR h Virginids           14h 16m  -11    24    <1    <1
ANT Antihelions           15h 04m  -18    30     1     2
LYR Lyrids                18h 13m  +32    48     2    <1
NCY Nu Cygnids            20h 50m  +42    42    <1    <1
ETA Eta Aquariids         22h 12m  -04    67    <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

T Pyx Update

I estimated the brightness of T Pyx at magnitude 7.3 during the past 2 evenings. This is a bit on the bright side with most observers placing it between 7.3 and 7.6. T Pyx should continue to slowly brighten for the next few days before entering a phase of more rapid brightening that should ultimately bring it to a peak magnitude of ~6.3.

Visual magnitude estimates submitted to the AAVSO. My observations are denoted by the blue crosses. Plot produced with the AAVSO Variable Star Plotter. Credit: AAVSO.

T Pyx’s Slow and Steady Brightening

Recurrent nova T Pyxidis continues to slowly brighten in the southern evening sky. The digital camera image below was taken by Bob Lunsford through a Celestron C9.25 schmidt-cassegrain telescope. T Pyx is the bright, slightly bluish star just to the lower right of center.

Image of T Pyx (2011 April 16 UT) and the surrounding star field with a C9.25 telescope and Canon PowerShot S2 camera. T Pyx is the bright bluish star near the center. Credit: Bob Lunsford.

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After rapidly brightening from a faint 15th magnitude to 8th magnitude in only 2 days, T Pyx’s rate of brightening has substantially slowed down. Over the past ~5 nights the nova has only brightened by an additional ~0.5 magnitudes. Last night I used 10×50 binoculars to estimate it at magnitude 7.5.

If T Pyx behaves as it did during its last outburst in 1966 it’s brightening trend should stop during the next few nights. Then for the next week or so its brightness will remain constant. After this short pause, the brightening trend will resume with an estimated peak around magnitude 6.3 in mid-May. That’s of course, if the nova follows the same playbook as it did in 1966 which is not a given.

Visual lightcurve based on visual observations submitted to the AAVSO. Credit: AAVSO.

T Pyxidis Erupts

For the first time in nearly 45 years, the recurrent nova T Pyxidis is in outburst. The usually quiescent 15th magnitude star has rapidly brightened to around magnitude 7.5 to 8.0. If it behaves similar to previous outbursts a further brightening to around magnitude 6.4 should occur over the next month.

Novae are the result of a thermonuclear explosion caused by the buildup of hydrogen on the surface of a white dwarf. As members of a double star system, the hydrogen is stripped from a normal main-sequence star unto the white dwarf. After each explosion it takes some time for the hydrogen to build up again in order to create the next nova outburst. The recycle time can be on the order of thousands to millions of years. A rare class of recurrent nova experience outbursts much more frequently (on the order of tens of years). The shorter outburst interval is due to the white dwarf being near the Chadrasekhar mass (the mass at gravity wins out and a white dwarf would collapse in a Type Ia supernova) and a high rate of hydrogen transfer between the stars.

On April 14, amateur astronomer Mike Linnolt of Hawaii spied T Pyxidis at magnitude 13. Though faint, this was a full 2 magnitudes brighter than usual and a clear sign that a new outburst had begun. Over the next 2 days, the nova rapidly brightened and many observers (including myself and friend of the blog Salvador Aguirre) are currently placing it at magnitude 7.8 (give or take a few 0.1 mags).

Visual lightcurve for recurrent nova T Pyx. Credit: AAVSO.

According to Dr. Bradley Schaefer (Louisiana State University) the nova should slowly brighten further over the next month and become as bright as magnitude 6.4 by May 20. This is based on previous outbursts of T Pyx. More can be found from Dr. Schaefer at the AAVSO website.

The current outburst is the 6th observed outburst by T Pyx. The previous 5 having occurred in 1890, 1902, 1920, 1944 and 1967. An earlier outburst from around 1866 is surmised by debris observed by the Hubble Space Telescope. There have been predictions that the rate of material collecting on T Pyx is slowing down and future outbursts will occur at longer intervals and might even stop for an extended period of time.

T Pyx is located in the faint southern constellation of Pyxis (the mariner’s compass) at a declination of -32°. This makes the star a difficult object for northern observers. Even when if it reaches 6th magnitude it will be a binocular or small telescope object for most observers.

Rest of March Meteors

March is usually one of the slowest months of the year for meteor watchers. Not only are there no major showers active, but sporadic rates are also low. Of the ~208 meteors detected by my 2 cameras over the 2nd half of March, only 5 were shower members 1 GNO, 1 ZSE and 3 ZCY). The only real excitement was on the night of March 28/29 when at least 3 meteors (and possibly 2 more that were not id’d as such by MetRec) were seen coming from a point near the expected radiant of the weak Zeta Cygnid shower.

Obs  Date(UT)      Time    TOT SPO ANT GNO ZSE ZCY
SAL3 2011-03-31   01h 43m   5   5   0   -   -   0
ALLS 2011-03-31   10h 22m   2   2   0   -   -   0
SAL3 2011-03-30   09h 55m   7   4   3   -   -   0
ALLS 2011-03-30   10h 24m   5   4   0   -   -   0
SAL3 2011-03-29   09h 44m   11  8   2   -   -   1
ALLS 2011-03-29   09h 59m   5   3   0   -   -   2
SAL3 2011-03-28   09h 59m   11  0   0   -   0   0
ALLS 2011-03-28   10h 22m   3   3   0   -   0   0
SAL3 2011-03-27   02h 32m   7   7   0   -   0   -
ALLS 2011-03-27   10h 30m   4   4   0   -   0   -
SAL3 2011-03-26   10h 02m   11  9   2   -   0   -
ALLS 2011-03-26   10h 31m   7   6   0   -   1   -
SAL3 2011-03-25   09h 44m   11  0   0   -   0   -
ALLS 2011-03-25   09h 58m   10  8   2   -   0   -
SAL3 2011-03-24   10h 08m   9   8   1   -   0   -
ALLS 2011-03-24   10h 36m   3   3   0   -   0   -
SAL3 2011-03-23   08h 12m   8   7   1   -   -   -
ALLS 2011-03-23   08h 25m   5   4   1   -   -   -
SAL3 2011-03-22   01h 40m   3   3   0   0   -   -
ALLS 2011-03-22   00h 00m   0   0   0   0   -   -
SAL3 2011-03-21   10h 05m   7   6   1   0   -   -
ALLS 2011-03-21   10h 25m   3   2   1   0   -   -
SAL3 2011-03-20   01h 59m   5   4   1   0   -   -
ALLS 2011-03-20   10h 44m   3   2   0   1   -   -
SAL3 2011-03-19   10h 17m   14  14  0   0   -   -
ALLS 2011-03-19   10h 47m   9   8   1   0   -   -
SAL3 2011-03-18   10h 20m   6   6   0   0   -   -
ALLS 2011-03-18   10h 48m   5   5   0   0   -   -
SAL3 2011-03-17   10h 22m   5   4   1   0   -   -
ALLS 2011-03-17   10h 50m   0   0   0   0   -   -
SAL3 2011-03-16   10h 24m   10  8   2   0   -   -
ALLS 2011-03-16   10h 49m   2   2   0   0   -   -
SAL3 2011-03-15   10h 26m   9   6   3   0   -   -
ALLS 2011-03-15   10h 54m   3   2   1   0   -   -

SAL3 - SALSA3 camera in Tucson (Carl Hergenrother)
ALLS - Near all-sky camera in Tucson (Carl Hergenrother)
VIST - Visual observations from Tucson (Carl Hergenrother)
VISH - Visual observations from Hermosillo (Salvador Aguirre)
HERM - PARENI camera in Hermosillo (Salvador Aguirre)
SDG - Camera in San Diego operated by Bob Lunsford
Time - Total amount of time each camera looked for meteors
TOT - Total number of meteors detected
SPO - Sporadics (meteors not affiliated with any particular meteor shower)
ANT - Antihelions
GNO - Gamma Normids 
ZSE - Zeta Serpentids 
ZCY - Zeta Cygnids 

Meteor Activity Outlook for April 16-22, 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.

Meteor activity picks up a bit during April as two major showers are active during the month. The first of these, the Lyrids, are active from the 16th through the 25th, with a pronounced maximum on the 22nd. The Eta Aquariids start appearing near the 28th and reach maximum activity during the first week in May. Sporadic rates are low but steady as seen from the mid-northern hemisphere (45 N). Sporadic rates seen from the mid-southern hemisphere (45 S) rise this month toward a maximum in July.

During this period the moon reaches its full phase on Monday April 18. At this time the moon will lie opposite the sun and will be in the sky all night long. This is the worst time of the month to try and view meteor activity as the bright moonlight will obscure all but the brightest meteors. The estimated total hourly rates for evening observers this week is near one 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 six from the northern hemisphere and seven as seen from south of the equator. 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 this week 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 April 16/17. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.

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
PPU Pi Puppids            07h 06m  -44    18    <1    <1
SLE Sigma Leonids         13h 18m  +06    20    <1    <1
ANT Antihelions           14h 40m  -15    30     1     1
LYR Lyrids                17h 56m  +35    48     1    <1
ZCY Zeta Cygnids          20h 00m  +37    42    <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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