05/2/2012
May Skies
By Dick Cookman
Highlights: Comet Journal, Martian Landers, Meteor Showers, Analemma, Planet Plotting, May Moon
Focus Constellations: Cassiopeia, Cepheus, Ursa Minor, Draco, Hercules, Bootes, Coma Berenices, Ursa Major, Leo, Lynx, Camelopardalis
Comet Journal
At 8th magnitude we are viewing the last hurrah of Comet C/2009 P1 (Garradd) which moves from southern Lynx into Cancer in May. By June it will diminish to 10th magnitude as it descends into the Asteroid Belt. It is in the northwestern sky after sunset and sets after midnight during May.
Comet 2011 F1 (Linear) is circling between Draco and Ursa Major and is still quite dim at 12th magnitude. It will brighten to 9th or 10th magnitude as it approaches the Sun and Earth and is closest in the autumn.
Preliminary observations of Comet 96P/Machholz 1 (2012) in the southern hemisphere do not obviate the possibility that it may achieve naked eye visibility as it moves into the skies of the northern hemisphere and passes Earth in July.
Martian Landers
Opportunity is on the western rim of Endeavor Crater at a site called Greeley Haven on the north end of Cape York where it has a northward tilt of 15 degrees for favorable solar energy production. Since the winter solstice on March 29th solar panel output increased almost 20% to more than 365 watt hours on Sol 2934 (April 25, 2012). Peak levels of solar energy production by Opportunity have exceeded 500 watt hours during favorable seasons.
The rover is conducting radio Doppler tracking measurements of a distant point on Mars enabling scientists to determine small variations in the rotation and nutation (wobble of rotational axis) of Mars which will allow more detailed understanding of the nature of the core and mantle of Mars.
Further studies of the nearby rock target (Amboy) were conducted during the interval with the microscopic imager and the Mössbauer spectrometer and imaging with the Panoramic Camera (Pancam) revealed additional details in the nature of the surrounding terrain.
Meteor Showers
The last time Comet 1/P Halley passed by in 1986 it added to the gas and dust debris scattered along its orbit. Earth will plunge through this stream of debris in May when the Eta Aquarid meteor shower peaks on the night of May 4/5 and competes with the Moon which is Full on the evening of the 5th. Eta Aquarius rises about 3AM when the Moon is in the western sky so observers who position themselves in the shadows of the gibbous Moon may see brighter components of the meteor shower in the hours before dawn.
The shower is characterized by very swift, bright meteors and occasionally produces as many as 60 meteors per hour in dark skies. Even on the moonlit night of the 5th, a dozen or more bright meteors may be visible during the peak hour. The peak is often spread over a week so meteors may be observed before dawn between May 3rd and May 10th.
Annular Solar Eclipse
Annular eclipses of the Sun occur when the Moon is between the Sun and Earth and the Moon is near the most distant part of its orbit around Earth. Under these conditions on May 20th the Moon will block out 89% of the central part of the Sun's disk and allow light from the outer 11% of the solar disk to reach Earth providing a view of the New Moon surrounded by a bright halo of sunlight.
The annular solar eclipse which culminates on the night of the New Moon will be best viewed between southeast China and western United States. In the United States the annular eclipse will be limited to northern California, central Nevada, southwestern Utah, northern Arizona, central New Mexico, and the western part of the Texas panhandle. However, most of the rest of western United States will see a partial eclipse which becomes progressively smaller farther eastward.
On the west coast the eclipse peaks between 6:18 and 6:38PM PDT and about 7:29PM MDT in Salt Lake City. In Chicago and Toronto the partial eclipse will be slightly before 8:30PM EDT. Although the next annular eclipse in the United States is not for 9.5 years, there will be a total solar eclipse on August 21, 2017.
Planet Plotting
Venus, Mars, and Saturn are the evening planets of May with Mercury (-1.9) joining in next month. Venus is in Taurus in May and doesn't set until after 11PM EDT at the beginning of the month. It was at its brightest of the year at magnitude -4.7 in April and decreases by 50% to -3.9 by the end of May as it catches up and orbits by Earth. Venus catches Earth and is between Earth and the Sun on June 6th when it is at inferior conjunction. As it closes the distance with Earth, it will set closer to sunset and its crescent will thin causing the drastic diminution of brightness. By the 31st, it sets less than an hour after sunset. Observers may be able to see Venus before sunset when it is east of the Sun during the annular solar eclipse on the 20th.
Mars (0.0) in Leo is in the southeast and south and sets before 4AM EDT on the 1st. By the 31st its magnitude will drop to +0.5 and it will set by 2AM EDT. Saturn in Virgo passed through opposition on April 15th and diminishes from magnitude +0.3 to +0.5 in May. Saturn is in the southern sky after sunset and sets after midnight.
Mercury moves from Pisces to Taurus in May and increases in brightness from magnitude -0.1 to -1.9. It was at greatest western elongation in mid-April and is approaching superior conjunction on May 27th. It is lost in dawn's glow for much of May although fortunate observers may catch it right before sunrise in early May. Jupiter is in Taurus and is on the other side of the Sun. Superior conjunction is on the 13th. Uranus (+5.9) in Pisces and Neptune (+7.9) in Aquarius are morning planets which rise before sunrise in May. Neptune is best observed at the beginning of morning twilight and Uranus will not be very visible in the twilight until late May. Both require at least 10x50 binoculars to be seen.
| Planet | Constellation | Magnitude | Planet Passages |
|---|
| Sun | Aries, Taurus | -26.8 | |
| Mercury | Pisces, Aries, Taurus | -0.1 to -1.9 | Jupiter, 0.41°SE, 5/22, Midnight EDT
Superior Conjunction, 5/27, 7AM EDT |
| Venus | Taurus | -4.7 to -4.1 | |
| Mars | Leo | 0.0 to +0.5 | |
| Jupiter | Aries | -2.1 to -2.0 | Mercury, 0.41°NW, 5/22, Midnight EDT
Superior Conjunction, 5/13, 9AM EDT |
| Saturn | Virgo | +0.3 to +0.5 | |
| Uranus | Pisces | +5.9 | |
| Neptune | Aquarius | +7.9 | |
May Moon
April's New Moon on the 21st at 3:18 AM EDT marked the start of lunation 1105 which ends with the New Moon on May 20th at 7:47PM EDT and is 29.69 days long.
The Full Moon of May at 11:35PM EDT on the 5th is the "Milk, or Planting Moon". Colonial Americans called it the former and the American Cherokees call it the latter. Celts referred to it as the "Bright Moon" and is is the "Dragon Moon" to the Chinese. Medieval English thought of it as the "Hare Moon" and the Anishnaabe (Chippewa and Ojibwe) of northern Michigan call it “Waabigwani-giizis" (Blossom Moon).
Lunar perigee is 0.1 hours before Full Moon on May 5th at 11PM EDT when the Moon will be closest to Earth at 221,712 miles or 55.97 Earth radii. The close proximity of perigee and Full Moon will produce unusually high tides. Apogee occurs on May 19th at Noon EDT, two days before New Moon. The Moon will be farthest from Earth at 252,555 miles or 63.72 Earth radii.
| Planet | Constellation | Magnitude | Moon Passage | Moon Phase/Age |
|---|
| Sun | Taurus | -26.8 | 7:47PM EDT, 5/20 | New ~ 0 days |
| Mercury | Aries | -1.4 | 2.1°SSE, Midnight EDT, 5/19 | Waning Crescent ~ 28.86 days |
| Venus | Taurus | -4.5 | 4.7°N, 6PM EDT, 5/22 | Waxing Crescent ~ 2.18 days |
| Mars | Leo | 0.0 | 7.3°NNE, 3AM EDT, 5/1 | Waxing Gibbous ~ 9.99 days |
| Mars | Leo | +0.5 | 6.5°NNE, 1AM EDT, 5/29 | Waxing Gibbous ~ 8.22 days |
| Jupiter | Aries | -2.0 | 1.8°S, 10AM EDT, 5/19 | Waning Crescent ~ 28.86 days |
| Saturn | Virgo | +0.3 | 6.2°N, 4PM EDT, 5/4 | Waxing Gibbous ~ 13.53 days |
| Uranus | Pisces | +5.9 | 5.2°SSE, 9AM EDT, 5/16 | Waning Crescent ~ 22.49 days |
| Neptune | Aquarius | +7.9 | 5.9°SSE, 3PM EDT, 5/13 | Waning Crescent ~ 25.24 days |
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