May 11-19 Meteors

The middle of May saw some nice meteor nights over Tucson. Even with the Eta Aquariids dropping off from their early May peak, enough Sporadic and minor shower activity is ongoing to keep nightly video rates at a dozen or more.

The last third of May may bring many more meteors than usual as the Camelopardalids, a usually very minor shower, may experience an outburst on the night of May 23/24. More on this shower in the next few days.

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Obs  Date(UT)      Time    TOT SPO ANT ETA XLI ELY SOP CCA
SAL  2014-05-19   08h 49m   13  9   0   2   -   -   1   1
SAL  2014-05-18   08h 51m   10  7   1   0   -   -   1   1
SAL  2014-05-17   07h 18m   7   5   0   1   -   -   0   1
SAL  2014-05-16   08h 51m   20  15  3   2   -   -   0   0
SAL  2014-05-15   08h 55m   16  14  1   1   -   -   0   -
SAL  2014-05-14   08h 43m   13  11  0   2   -   -   0   -
SAL  2014-05-13   08h 59m   11  9   1   1   -   -   1   -
SAL  2014-05-12   08h 58m   14  7   0   4   -   2   1   -
SAL  2014-05-11   08h 47m   18  11  0   7   0   0   0   -

SAL - SALSA3 camera in Tucson (Carl Hergenrother)
VIS - Visual observations from Tucson (Carl Hergenrother)
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
ETA - Eta Aquariids
XLI - April Chi Librids
ELY - Eta Lyrids
SOP - Southern May Ophiuchids
CCA - Chi Capricornids

May 1-10 Meteors

The end of last month experienced the peak of the major Lyrid meteor shower. The first week or so of May is seeing some signifiant activity from the Eta Aquariids (ETA). The ETAs are actually debris from Comet Halley. They are the sister shower to October’s Orionids (ORI). So if you’ve been seeing some long bright meteors during your early morning walks the past few mornings, you’ve actually been seeing small pieces of Halley’s comet.

The IMO Live ZHR page presents reports from visual observers from all around the world. They have been observing a good shower with ZHRs of ~50. It’s too bad the radiant is only observable for an hour or so prior to sunup from the the NH.

The ETAs were predicted to peak around May 7 UT and the IMO reports confirm this. My meteor camera totals disagree as the number of ETAs has continued to climb even though we are 2-3 days past the peak. Perhaps the number of bright ETAs (which are the only ones my camera can detect) are still increasing even though the total number of meteors (bright and faint) peaked a few nights ago. Regardless, the ETAs should wind down from here on out.

2014May10_ETA

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Obs  Date(UT)      Time    TOT SPO ANT ETA ABO PBO XLI ELY SOP
SAL  2014-05-10   08h 58m   23  11  0   11  -   -   0   1   0
SAL  2014-05-09   08h 55m   23  8   2   11  -   -   1   0   1
SAL  2014-05-08   09h 07m   17  9   1   7   -   -   0   0   0
SAL  2014-05-07   06h 16m   12  4   1   7   -   -   0   0   0
SAL  2014-05-06   09h 11m   12  3   2   7   -   -   0   0   0
SAL  2014-05-05   06h 49m   5   3   0   1   -   -   0   0   0
SAL  2014-05-04   09h 14m   16  9   2   5   0   0   0   0   0
SAL  2014-05-03   08h 42m   12  5   0   5   0   0   2   0   -
SAL  2014-05-02   08h 31m   25  14  4   5   1   0   1   -   -
SAL  2014-05-01   09h 06m   15  14  0   1   0   0   0   -   -

SAL - SALSA3 camera in Tucson (Carl Hergenrother)
VIS - Visual observations from Tucson (Carl Hergenrother)
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
ETA - Eta Aquariids
ABO - Alpha Bootids
PBO - Phi Bootids
XLI - April Chi Librids
ELY - Eta Lyrids
SOP - Southern May Ophiuchids 

Late April Meteors

April 22 marked the peak of the Lyrid meteor shower. The Lyrids are considered a major shower though, in reality, they are the weakest of the major showers. You might even be able to call them the strongest minor shower.

The Lyrids were produced by comet C/1861 G1 (Thatcher), a comet seen only in 1861. It is a high inclination (~80º) long-period comet with a period of ~400 years. The shower is also prone to outbursts though none was predicted for or reported this year. On the April 22 UT, a total of 21 Lyrids were observed. The star chart below shows the radiant of the Lyrids halfway between Lyra and the keystone of Hercules.

2014Apr22_Lyrids

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Obs  Date(UT)      Time    TOT SPO ANT SLE PPU LYR ETA
SAL  2014-04-30   09h 13m   16  12  1   -   -   -   3
SAL  2014-04-29   09h 23m   13  11  2   -   -   -   0
SAL  2014-04-28   09h 09m   12  10  1   -   0   -   1
SAL  2014-04-27   09h 01m   16  13  2   -   0   -   1
SAL  2014-04-26   08h 03m   6   4   0   2   0   -   0
SAL  2014-04-25   09h 07m   12  10  2   0   0   0   0
SAL  2014-04-24   08h 15m   11  8   1   0   0   2   0
SAL  2014-04-23   07h 39m   15  8   1   2   0   4   0
SAL  2014-04-22   09h 08m   30  8   1   0   0   21  0
SAL  2014-04-21   09h 12m   14  9   1   1   0   3   0
SAL  2014-04-20   07h 54m   15  13  0   1   0   1   0
SAL  2014-04-19   06h 19m   5   4   0   0   0   1   0
SAL  2014-04-18   00h 00m    "Clouds All Night"
SAL  2014-04-17   08h 23m   11  7   2   1   0   1   -
SAL  2014-04-16   09h 49m   17  13  3   1   0   0   -

SAL - SALSA3 camera in Tucson (Carl Hergenrother)
VIS - Visual observations from Tucson (Carl Hergenrother)
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 - AntihelionsZSE - Zeta Serpentids
SLE - Sigma Leonids
PPU - Pi Puppids
LYR - Lyrids
ETA - Eta Aquariids

Meteor Shower Activity for May 10-16, 2014

The Meteor Activity Outlook for the period 2014 February 15-21 has been posted by Bob Lunsford on the American Meteor Society website.

The Outlook has details on meteors from the Antihelion region and the following showers: Eta Aquariids (ETA), Eta Lyrids (ELY) and Theta 2 Sagittariids (TTS).

Orionids Peak This Weekend

Everyone know that the most famous comet is Comet Halley. Once every 76 years or so, Hally visits the inner Solar System. Sometimes is can be quite spectacular (such as in 1910), other times not so much (as in 1986). For those that missed Halley in ’86, it will be back again in 2061. If you don’t want to wait that long, there is a way to see pieces of Halley every year. Dust released by Halley over the past few thousand years produce meteor showers in early May (the η-Aquariids) and mid-October (the Orionids).

Computer simulations of the past movements of Halley and its dust suggest that many of this year’s Orionid meteors were released by Halley between 1265 BC and 910 BC (for some points of reference, the Trojan War took place around 1200 BC and King David ruled around 1000 BC).

This year the Orionids are forecast to peak tonight (Oct 20/21) though this shower usually produces high rates for a few days on either side of its peak time. According to the Live ZHR page on the International Meteor Organization’s page, rates last night reached a ZHR of 20-30. Tonight rates should be a little better, probably between 30-40. ZHR’s been as high as 70 per hour in the past but during the last 2 years ZHRs only reached 35-45 per hour. This year’s activity should be similar to the last few years.

The Orionids appear to come from an area in northern Orion. This area, called the radiant, rises around 10pm local time. It is best to wait till the radiant is high in the sky before looking for meteors (say 1am). The radiant is highest around 3:30am which is the best time to look. Meteors can appear anywhere in the sky so you don’t have to look at the radiant. The chart below is for around 3-4am local time and shows the radiant and directions of the Orionids.

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Hints for watching the Orionids:

  1. Orionid meteors are not visible before ~10-11 pm. Even then the radiant is too low to see many meteors. It is best to go out sometime between 2 am and the start of dawn.
  2. Even though the Zenithal Hourly Rate (ZHR) for the Orionids may be as high as 40 per hour this year.  Most people will see fewer meteors. The ZHR is calculated for perfect conditions (radiant overhead, dark skies, and no obstructions in your view). If you observe from rural areas where the Milky Way is bright and obvious you might see 40 per hour. Suburban skies were the Milky Way is just barely visible will probably only produce 10-20 per hour. City observers will see only a few per hour.
  3. It may take some time to see some meteors. Going out for a minute or two won’t cut it. Plan to spend at least 30 minutes of more outside. Also allow your eyes some time to get adapted to the dark. It will take at least 10-20 minutes after walking out of a well-lit house to start seeing faint enough to see most Orionids.
  4. Find a spot that is safe, free of as many obstructions (trees, buildings, etc) as possible and free of annoying lights shining in your face. This is not always possible these days. You don’t need to look directly at the radiant. In fact, it is better to place the radiant just outside your field of view. As long as you do this, it won’t matter what direction you look in.
  5. Be prepared to be cold. The early October mornings can get very chilly. Dress warm and bring a blanket. Also plan to be as comfortable as possible. A nice reclining chair works great. It will keep your neck from being strained and keep you off of the cold ground.
  6. Enjoy the show! The split second meteors are tiny dust grains from Comet Halley released thousands of years ago; are hitting the Earth’s atmosphere at speeds of ~40 miles per second (~66 km per second) and are burning up 60 miles (100 km) above your head.

In the Transient Sky – May 2012

The big event this month (at least for folks around the northern Pacific basin) is the annular solar eclipse on May 20. As for planets, Venus, Mars and Saturn are easy to see in the evening.

May 2012 Highlights
* Annular Solar Eclipse for western North America, the north Pacific basin and far eastern Asia
* Venus dominates the evening sky
* Mars fades but still is high in the evening sky
* Saturn is easily seen in eastern evening sky
* Comet C/2009 P1 (Garradd) is a nice binocular object in the evening sky

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>.

Annular Solar Eclipse

The big event this month is an annular eclipse of the Sun on May 20. For more information on when and where this event can be seen go to Science News @ NASA Science.

Planets

Evening Planets

Venus  – Venus reaches its maximum brilliance at magnitude -4.7 right at the start of the month. At the start of the month Venus is riding high in the West and sets up to 3.5 hours after the Sun. But Venus is now on a bee-line towards the Sun. By mid-month it sets 2.5 hours after the Sun and by the end of the month it will be so close to the Sun that it sets within 40 minutes of the Sun. All during the month, Venus will slightly fade but in a telescope it will appear to become bigger in apparent diameter while also becoming more crescent. All of this leads up to a rare Venus transit on June 5 when Venus will appear to pass in front of the disk of the Sun. The Moon makes a nice pair with Venus on May 22.

Mars - Mars is the bright reddish “star” nearly overhead early in the evening. Mars reached opposition (the point opposite the Sun on the sky) in early March. Since Mars was near its aphelion when we passed it on our inside track, this opposition is almost as faint as can be at a magnitude of -1.2. In May, it fades from +0.0 to +0.5. The red planet will spend the month moving eastwards below the constellation of Leo. The 1st Quarter Moon visits on the 28th.

Saturn - Saturn reached opposition on April 15 at a distance of 8.75 AU (813 million miles or 1.3 million km) from Earth. Opposition meant Saturn was directly opposite the Sun in the sky. This month it can be seen in the east at the start of evening making a nice but distant pair with bright 1st magnitude Spica. Being past opposition it will fade from magnitude +0.3 to +0.5. The nearly Full Moon visits on the mornings of the 3rd and 4th.

Morning Planets

Mercury – If you live in the Southern Hemisphere, Mercury is still in the middle of a nice morning apparition at the start of the month. By mid-month it will be too low for easy observation.  If, like me, you live north of the equator, this month’s display will be a hard one to observe. At the every end of the month, Mercury starts a better apparition for northern observers in the evening. Though still very low, It will be within ~2° of Venus although both will be only 8° from the Sun at the time.

Jupiter – With conjunction on May 13th, this planet will be located to close to the Sun to be easily seen this month.

Meteors

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. Background rates will remain low in May.

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, 6 or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

Eta Aquariids (ETA)

The Eta Aquarids are a major shower, especially for southern hemisphere observers, when they peak on May 5. 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. This means that the ETA radiant is only visible for an hour or so before twilight. Unfortunately the Moon is full just a day after the expected peak of the ETAs on May 5 making this a difficult shower to observe this year.

The shower spans from April 19 to May 28 with a peak around May 5 with a maximum ZHR of ~60.

Additional information on these showers and other minor showers not included here can be found at the following sites: Robert Lunsford’s Meteor Activity Outlook and the International Meteor Organization’s 2012 Meteor Shower Calendar.

Minor Meteor Showers

Minor showers produce so few meteors that they are hard to notice above the background of regular meteors. Info on many minor showers are 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 International Meteor Organization’s 2012 Meteor Shower Calendar.

Comets

Naked Eye Comets (V < 6.0)

None this month.

Binocular Comets (V = 6.0 – 8.0)

C/2009 P1 (Garradd)

First seen way back on August 13, 2009 by Gordon Garradd who was observing for the Siding Spring Survey, a NASA-funded survey observing from Australia. At the time of discovery it was located at a distance 8.7 AU from the Sun, nearly the distance of Saturn. Perihelion occurred 2 days before Christmas 2011 at 1.55 AU from the Sun. Though the comet does not get very close to the Sun, it is an intrinsically bright comet and could have been a real sight had it come closer to the Sun and Earth.

The comet is in full retreat from the Earth and Sun as it heads outward on its long journey back to the cold depths of the outer Solar System.  Comet Garradd is slowly moving south through the constellation of Cancer in the evening sky.  Since the comet is moving away from us and the Sun it should continue to fade from around magnitude 8.0 to 8.9 as the month progresses. The comet does appear to be fading rather slowly and may be brighter than predicted here as the month progresses.

Date       RA       DEC     Delta    r    Elong   Mag
May  1   08h 50m  +38°01'   2.190  2.311    84    8.0
May 10   08h 50m  +33°56'   2.420  2.395    77    8.3
May 20   08h 52m  +30°07'   2.677  2.489    68    8.6
May 30   08h 56m  +26°51'   2.929  2.584    60    8.9

Small Telescope Comets (V = 8.0 – 10.0)

None

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

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.

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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.

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
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