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 <>.

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.


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.


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.


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)