Meteor Activity Outlook for May 28-June 3, 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.

June is another slow month for meteor activity. There are no major showers active in June and only the Antihelion source can be counted on for continuous activity. Even the Antihelion is located so far south this time of year that rates rarely exceed two per hour as seen from the northern hemisphere. Sporadic rates reach their nadir in June as seen from the mid-northern hemisphere (45 N). Sporadic rates seen from the mid-southern hemisphere (45 S) continue to rise this month toward a maximum in July.

During this period the moon reaches its new phase on Wednesday June 1st. At this time the moon will lie near the sun and will not be visible at night. This weekend the waning crescent moon will not cause any problems viewing meteor activity as it is very thin and rises late in the morning. 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 eight from the northern hemisphere and eighteen 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 May 28/29. 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:

According to Peter Jenniskens, the Earth will pass only 0.0011 AU (100,000 miles) from the 1952 trail of comet 73P/Schwassmann-Wachmann 3 near  05:45 UT on June 2. This corresponds to 1:45am EDT, 12:45am CDT, 11:45pm MDT (on June 1st), and 10:45pm PDT (on June 1st). Unfortunately the comet was relatively inactive on this return and this trail is not expected to produce any activity this year. Still, I would urge observers to try and verify any activity near
the times listed above. This variable shower is known as the Tau Herculids (TAH) and last produced activity back in 1995, when parent comet broke up into several pieces. The radiant is expected to be near the position of 15:44  (236) +41. This area of the sky is located where the boundaries of Bootes, Corona Borealis, and Hercules meet. The nearest easily seen star is Mu Bootis, which lies four degrees southwest of the radiant in northern Bootes. This area of the sky lies high in the east once it becomes dark. It passes nearly overhead near 0100 local daylight time. Luckily, the moon is near new and will not interfere with observing at all. Please post your results either positive or negative to meteorobs as soon as possible. If no activity occurs as expected, then the next close approach will occur in 2017 from the 1941 trail. Looking even further ahead, in 2022, the Earth encounters many trails of SW3, including two of the very active 1995 trails, and an outburst of activity is expected.

The wide Antihelion (ANT) radiant is now centered at 17:24 (261) -23. This area of the sky lies in southeastern Ophiuchus, two degrees northeast of the third magnitude star Theta Ophiuchi. 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 southern Ophiuchus, western Sagittarius, Serpens Cauda, or 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.

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 two per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near fifteen 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
TAU Tau Herculids         15h 44m  +41    15    <1    <1
ANT Antihelions           17h 24m  -23    30     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 May 21-27, 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 last quarter phase on Tuesday May 24th. At this time the moon will lie ninety degrees west of the sun and will rise near 0100 local daylight time (LDT) for observers at mid-northern latitudes. This weekend the waning gibbous moon will seriously interfere with meteor observing as the fainter meteors will be obscured by the lunar glare. As the week progresses conditions will improve and the moon wanes and rises later in the morning. 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 four from the northern hemisphere and nine 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 May 21/22. 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 16:56 (254) -22. This area of the sky lies in southwestern Ophiuchus, six degrees northeast of the first magnitude orange star Antares (Alpha Scorpii). 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 eastern Libra, northern Lupus, southern Ophiuchus, southern Sagittarius, or 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.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately three 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 seven 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. Morning 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
ANT Antihelions           16h 56m  -22    30     1     2

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

The Ups and Downs of T Pyx

Let me just say that I really like this star. On the evening of May 7th UT (6th in local time) I measured T Pyx at magnitude 6.8. This was just a tenth of a magnitude brighter than a convenient magnitude 6.9 star located nearby. The next night I was expecting to find T Pyx even brighter but was surprised to find it fainter than the nearby reference star. After a break of a few days I wasn’t sure what to expect but I was pleasantly surprised to find T Pyx has brightened yet again. My observations placed it as magnitude 6.5.

If all goes according to predictions based on its 1966 outburst, the nova should brighten by another few tenths of a magnitude during the next week or so. Then begins its long fade back to quiescence.

Visual and CCD magnitude measurements for T Pyx. Credit: AAVSO.

T Pyx Fading?

This evening I took another peak at T Pyx and was surprised to find it looking a bit fainter than it did last night. The lightcurve from the AAVSO suggests that T Pyx may have been slowly fading over the past 3 days or so. It will be interesting to see if this is a short-term dip before brightening to its predicted peak later this month, or if this is the beginning of a fade back to quiescence.

Visual and CCD V lightcurve for T Pyx from the AAVSO LightCurve Generator. Credit: AAVSO.

April 21 – 30 Meteors

The last 10 nights of April  saw the peak of one major shower (the Lyrids) and the beginning of activity for May’s only major (the Eta Aquariids).

Obs  Date(UT)      Time    TOT SPO ANT SLE PPU LYR NCY HVI ETA
SAL3 2011-04-31   08h 29m   8   5   1   -   -   -   0   -   2
ALLS 2011-04-30   08h 44m   6   4   0   -   -   -   0   -   2
SAL3 2011-04-29   08h 52m   10  9   0   -   -   -   0   -   0
ALLS 2011-04-29   09h 20m   4   4   0   -   -   -   0   -   0
SAL3 2011-04-28   02h 58m   9   7   2   -   0   -   0   -   0
ALLS 2011-04-28   08h 59m   7   4   2   -   0   -   0   -   1
SAL3 2011-04-27   08h 57m   10  8   2   -   0   -   0   -   -
ALLS 2011-04-27   09h 28m   3   2   1   -   0   -   0   -   -
VISH 2011-04-27   01h 00m   3   1   -   -   -   -   -   -   2 (LM=6.0)
SAL3 2011-04-26   08h 41m   11  6   3   -   0   -   0   2   -
ALLS 2011-04-26   08h 56m   8   7   1   -   0   -   0   0   -
SAL3 2011-04-25   09h 01m   4   3   1   0   0   0   0   0   -
ALLS 2011-04-25   09h 29m   3   3   0   0   0   0   0   0   -
SAL3 2011-04-24   04h 40m   13  7   0   0   0   5   1   0   -
ALLS 2011-04-24   09h 34m   12  6   1   0   0   5   0   0   -
SAL3 2011-04-23   09h 04m   17  8   0   1   0   8   0   0   -
ALLS 2011-04-23   09h 35m   8   4   0   0   0   3   1   0   -
HERM 2011-04-23   01h 29m   5   1   1   0   0   3   0   0   -
SAL3 2011-04-22   09h 07m   15  3   1   0   0   8   1   2   -
ALLS 2011-04-22   09h 37m   11  0   1   0   0   9   1   0   -
HERM 2011-04-22   06h 07m   14  4   4   1   0   5   0   0   -
VISH 2011-04-22   01h 00m   2   1   -   -   -   1   -   -   - (LM=5.0)
SAL3 2011-04-21   09h 09m   12  6   0   0   0   5   1   -   -
ALLS 2011-04-21   09h 39m   8   5   0   0   0   2   1   -   -

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
SLE - Sigma Leonids 
PPU - Pi Puppids 
LYR - Lyrids 
NCY - Nu Cygnids 
HVI - h Viriginds 
ETA - Eta Aquariids

April 11 – 20 Meteors

The period of April 11-20 sees a little more diversity as a number of showers become active. Though most are minor, the Lyrids (LYR) are the first major shower since the Quadrantids of early January. Unfortunately, the Lyrids introduce a theme that will be all too common this year, a major shower ruined by bright moonlight.

Obs  Date(UT)      Time    TOT SPO ANT ZCY SLE PPU LYR NCY
SAL3 2011-04-20   09h 11m   15  6   2   -   1   0   5   1
ALLS 2011-04-20   09h 26m   6   4   0   -   0   0   2   0
SAL3 2011-04-19   09h 13m   6   4   0   -   0   0   0   2
ALLS 2011-04-19   09h 43m   10  8   1   -   0   0   1   0
SAL3 2011-04-18   09h 16m   6   6   0   -   0   0   0   0
ALLS 2011-04-18   09h 34m   4   4   0   -   0   0   0   0
SAL3 2011-04-17   09h 17m   7   7   0   -   -   0   0   -
ALLS 2011-04-17   09h 47m   2   1   0   -   -   0   1   -
SAL3 2011-04-16   09h 19m   11  9   1   -   -   0   1   -
ALLS 2011-04-16   09h 49m   5   3   0   -   -   0   2   -
SAL3 2011-04-15   09h 22m   11  11  0   -   -   0   -   -
ALLS 2011-04-15   09h 51m   4   3   1   -   -   0   -   -
SAL3 2011-04-14   09h 24m   5   4   1   -   0   -   -   -
ALLS 2011-04-14   09h 52m   6   4   2   -   0   -   -   -
SAL3 2011-04-13   09h 26m   7   5   2   0   0   -   -   -
ALLS 2011-04-13   00h 41m   2   2   0   0   0   -   -   -
SAL3 2011-04-12   09h 27m   11  8   2   0   1   -   -   -
ALLS 2011-04-12   09h 57m   3   3   0   0   0   -   -   -
SAL3 2011-04-10   09h 30m   13  11  2   0   0   -   -   -
ALLS 2011-04-11   09h 59m   3   3   0   0   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
ZCY - Zeta Cygnids
SLE - Sigma Leonids
PPU - Pi Puppids
LYR - Lyrids
NCY - Nu Cygnids

T Pyx Brightens Again

Last time we talked about the nova T Pyx it was holding steady around magnitude 7.4 and 7.7. Over the past few days T Pyx has resumed brightening and it currently around magnitude 6.7 to 7.0. If it continues to do as it did in 1966, it should brighten to around magnitude 6.3 over the next 3 weeks.

April 1 – 10 Meteors

The first ten nights of April yielded a steady sprinkle of meteors. As is typical of a month with no major showers and few minor ones, most of the meteors were sporadics or antihelions. Less than 10% were associated with the only active shower, the relatively minor Zeta Cygnids (ZCY).

Obs  Date(UT)      Time    TOT SPO ANT ZCY
SAL3 2011-04-10   00h 00m   Clouds
ALLS 2011-04-10   00h 00m   Clouds
SAL3 2011-04-09   00h 20m   1   1   0   0
ALLS 2011-04-09   07h 59m   2   1   1   0
SAL3 2011-04-08   09h 37m   13  12  1   0
ALLS 2011-04-08   10h 05m   7   3   3   1
SAL3 2011-04-07   02h 34m   5   3   1   1
ALLS 2011-04-07   01h 29m   5   3   1   1
SAL3 2011-04-06   01h 45m   5   5   0   0
ALLS 2011-04-06   10h 10m   3   3   0   0
SAL3 2011-04-05   09h 43m   12  7   4   1
ALLS 2011-04-05   10h 11m   8   6   1   1
SAL3 2011-04-04   09h 45m   13  10  3   0
ALLS 2011-04-04   10h 14m   9   6   3   0
SAL3 2011-04-04   00h 00m   Clouds
ALLS 2011-04-03   00h 00m   Clouds
SAL3 2011-04-02   06h 49m   14  10  3   1
ALLS 2011-04-02   07h 03m   7   7   0   0
SAL3 2011-04-01   08h 43m   12  8   2   2
ALLS 2011-04-01   08h 58m   8   6   0   2

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
ZCY - Zeta Cygnids

In The Sky This Month – May 2011

This feature highlights a number of meteor showers, comets and asteroids which are visible during the month of May 2011.

May 2011 Highlights
* Venus, Jupiter, Mercury and Mars gather low in the dawn sky
* Saturn is easy to spot in the evening
* Eta Aquariids put on a night display for southern observers

Note: If anyone has pictures or observations of these objects/events and want to share them with my readers, send them to the Transient Sky at <transientsky1@yahoo.com>.

Planets

Moon - The table below lists important lunar dates for the month, including the phases of the Moon and nights of lunar-planetary and lunar-stellar conjunctions.

May 1 - Moon 7° from Mercury, 6° from Jupiter and 5° from Mars
May 3 - New Moon
May 5 - Moon 7° from bright star Aldebaran
May 8 - Moon 9° from bright star Pollux
May 9 - Moon 5° from Beehive Cluster
May 10 - First Quarter Moon
May 11 - Moon 5° from bright star Regulus
May 14 - Moon 8° from Saturn
May 15 - Moon 3° from bright star Spica
May 17 - Full Moon
May 18 - Moon 3° from bright star Antares
May 24 - Third Quarter Moon
May 29 - Moon 5° from Jupiter
May 30 - Moon 4° from Mars
May 31 - Moon 4° from Venus

Saturn – Saturn is now a month past opposition. As a result, the ringed planet is still near its brightest for the year (currently magnitude +0.5 to +0.7) and is also visible throughout the evening and most of the morning hours. Saturn is a slow moving planet and takes 29 years to circle the Sun as well as 29 years to do one circuit around the ecliptic constellations. As has been the case all year long, Saturn is still located in Virgo about 13-14° from 1st magnitude Spica.

May 14 - Saturn and Moon 8° apart

Venus, Mercury, Mars and Jupiter -  The planetary show of the year is a series of compact groupings involving Venus, Mercury, Mars and Jupiter. Unfortunately, all the action will take place very close to the eastern horizon in a bright dawn sky for northern observers. South of the equator the view will be much easier to see.

From May 7 to 15, Venus, Mercury and Jupiter will be within 5° of each other. On May 11, the trio will be within ~2° of each other. A similar trio of Venus, Mercury and Mars will be within 5° of each other from May 15-25 with their tightest grouping of ~2° on May 21.

May 1 - Moon 7° from Mercury, 6° from Jupiter and 5° from Mars
May 1 - Jupiter and Mars within 0.4° of each other
May 6 - Mercury at greatest elongation west
May 7 - Mercury and Venus within 1.4° of each other
May 11 - Venus, Mercury and Jupiter within 2.1° of each other
May 18 - Mercury and Venus, again, within 1.4° of each other
May 21 - Venus, Mars and Mercury within 2.1° of each other
May 23 - Venus and Mars within 1° of each other
May 29 - Moon 5° from Jupiter
May 30 - Moon 4° from Mars
May 31 - Moon 4° from Venus

Meteors

Meteor activity is near a seasonal minimum in May. The year is usually split in 2 with January through June having low rates with few major showers while July through December have high rates with many major showers.

Sporadic Meteors

Sporadic meteors are not part of any known meteor shower. They represent the background flux of meteors. Except for the few days per year when a major shower is active, most meteors that are observed are Sporadics. This is especially true for meteors observed during the evening. During May mornings, 10-12 or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

Eta Aquariids (ETA)

The Eta Aquariids are a major shower, especially for southern hemisphere observers, when they peak on May 6. For northern observers, the shower will only be observable for an hour or two before dawn. Since the radiant doesn’t get very high for NH observers, rates can be low. The radiant is located near the “jar” of Aquarius.

The ETA were produced by Comet Halley which also gives us the Orionids in October. Models suggest that the ETA were released by Comet Halley no later than 837 AD. The Orionids are easy to see because the particles are hitting the Earth from the anti-solar direction. This means the meteor shower can be seen in the middle of the night. The ETA are produced by meteoroids moving outbound from the Sun, as a result the radiant is located relatively close to the Sun. As a result the ETA radiant is only visible for an hour or so before twilight. This year the Moon is near New so the sky will be dark.

The shower spans from April 19 to May 28 with a peak around May 5 with a maximum ZHR of ~60. The poor placement of the radiant for northern observers will greatly limit the number of observed meteors.

Minor Meteor Showers

Minor showers produce so few meteors that they are hard to notice above the background of regular meteors. Starting this month, info on most of the minor showers will be provided on a weekly basis by Robert Lunsford’s Meteor Activity Outlook.

Additional information on these showers and other minor showers not included here can be found at the following sites: Wayne Hally’s and Mark Davis’s NAMN Notes, and the International Meteor Organization’s 2011 Meteor Shower Calendar.

Comets

Naked Eye Comets (V < 6.0)

None this month…

Binocular Comets (V = 6.0 – 8.0)

None this month…

Small Telescope Comets (V = 8.0 – 10.0)

C/2011 C1 (McNaught)

It seems like every year sees a bright Comet McNaught and this year is no different. The 58th comet discovery by Rob McNaught and 74th from Siding Spring Observatory, C/2011 C1 was first seen on February 10th of this year. Though intrinsically faint, the comet is currently being reported as bright as magnitude 9.0. CCD images taken by the author on Apr 1 UT confirm that the comet was between magnitude 9.0 and 9.5 at that time (see image below). Unfortunately the comet should fade this month as it passed perihelion on April 17 at a distance of 0.88 AU from the Sun. The comet starts May 0.92 AU from the Sun and 1.23 AU from Earth. These distances will have increased to 1.02 AU from the Sun and 1.39 AU from Earth by mid-month and 1.17 AU from the Sun and 1.52 AU from Earth at the end of the May.  Comet C/2011 C1 is a morning object low in the east and travels from Pegasus to Pisces this month.

.

Asteroids

Binocular and Small Telescope Asteroids (V < 8.0)

(4) Vesta

Vesta is the brightest asteroid in the Main Belt. This is due to its high albedo (or reflectivity) which causes it to reflect ~42% of the light that strikes it. Vesta is also peculiar in that it appears to have evidence of volcanism on its surface. Similar to the Moon, Vesta may be covered with large expanses of frozen lava flows. It is classified as a V-type asteroid and is the only large asteroid with this classification. Many of the smaller V-type asteroids are chips of Vesta blasted off it by past asteroid and comet impacts. Vesta has dimensions of 347x336x275 miles or 578×560×458 km.

The maps below were created from images taken with the Hubble Space Telescope. The geography is dominated by a large impact crater located near the south pole (the blue ‘donut’ in the elevation map). Perhaps this crater is the result of the impact that blasted off the smaller V-type asteroids. We’ll know more this summer when NASA’s Dawn spacecraft enters orbit around Vesta for a full year. Currently the encounter is scheduled for July 2011 to July 2012.

Images and models of the shape of asteroid (4) Vesta. In the upper left is a real HST image, to the upper right is a model of Vesta’s shape, and on the bottom is an elevation map . Credit: NASA/STScI.

Vesta spends the month around magnitude 7.3 to 6.9 as it moves eastwards through western Capricornus. Opposition is on August 4 at magnitude 5.6.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand. Finder chart for Vesta from Heavens Above.

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