Highlights: Comet Journal, Martian Landers, Planet Plotting, Meteors, May Moons
Focus Constellations: Cancer, Leo, Coma Berenices, Virgo, Bootes, Hercules, Draco, Ursa Major

Comet Journal

Comet 2P/Enke peaked at magnitude 6.7 before its perihelion in mid–April but is lost in the glow of dawn in May. At the beginning of May it will rise before 7 AM EDT and set at 6:30 PM EDT and will be between Mira in Cetus and Alrisha, the star which connects the two fish in Pisces. By the end of May it will rise about 4:30 AM EDT near the tail of Cetus but will have dimmed to 10th magnitude as it drops into southern hemisphere skies and retreats from the inner Solar System.

After peaking on Jan. 14th at magnitude -5.5 which is about 2.5 times as bright as Venus, Comet C/2006 P1 McNaught toured the skies of the southern hemisphere. It has declined to 10th magnitude and is circuiting the south Celestial Pole before heading into the outer Solar System toward the Southern Cross.

Since passing perihelion on April 4th when it reached 1st magnitude, Comet 96P Macholtz 1 has decreased to 12th magnitude and rises in western Pegasus after 2 AM EDT.

Comet C/2007 E2 is a new comet discovered in the southern hemisphere skies in March. It reached magnitude 7.5 in late April and passes Earth in early May. It can be seen with binoculars in the northern sky near the head of Draco on May 1st and will reach Thuban in Draco by the end of May.

Martian Landers

Opportunity had a rather productive month during late March and early April and has now completed about 33% of its clockwise circuit of the 800 meter diameter Victoria Crater which probably was formed when a 50 meter diameter meteorite impacted the Martian surface. A momentary software glitch during program bootup of the computer on Opportunity on Sol 1116 required intervention by the mission team which was able to ensure that the rover was up and running again by Sol 1121 (Mar. 21, 2007). Opportunity then drove out toward the Cape of Good Hope where it could began its long baseline stereo imaging of the multi-colored layers making up the next promontory, Cape St. Vincent, and the intervening bay, Valley Without Peril, which appears to provide the best route yet examined for access into Victoria Crater. The rover moved along the crater wall during Sols 1122 to 1134, temporarily halting to continue the stereo imaging program and to gather spectral observations of soil, rock, and the sky.

On Sol 1128 mission scientists developed a way to work around a malfunction in the rock abrasion tool (RAT), which enabled continued usage of this valuable instrument. Opportunity then embarked on a sidetrip from Sol 1135 to Sol 1150 (Apr. 19) to examine dark streaks of material which radiate outward from the northern side of the crater and the intervening areas of lighter materials which surround the crater. On Sol 1155, the rover returned to Tierra del Fuego, the next promontory on the edge of Victoria Crater, to continue with long baseline stereo imaging. Opportunity has covered a total of 10,486.20 meters (6.52 miles) since landing on Mars.

Spirit conducted detailed observations of Mitcheltree Ridge from Sol 1140 through Sol 1144 (March 23, 2007). Particular attention was paid to a rock target referred to as Torquas. Upon completion of this study, panoramic imaging of Mitcheltree Ridge proceeded, followed by surveys of layered outcrops known as “Zanor,” “Banth,” “Okar,” and “Dor" (using the miniature thermal emission spectrometer) and photometric measurements using the panoramic camera. On Sol 1145, the rover reversed course and headed back southward between Mitcheltree Ridge and Home Plate Plateau in order to examine a variety of light colored clasts and pebbles referred to as Elizabeth Mahon and a pockmarked rock outcrop called Madeline English, named after women who played in the Girls Professional Baseball League in the 1940's and 50's.
After completing examination of the clasts and pebbles Spirit turned northward on April 10th (Sol 1162) to approach and observe Madeline English. When the observations are completed, the rover will continue northward to find an access route to the top of the plateau. Spirit’s Martian excursion as of April 10th has encompassed 7,092.29 meters (4.41 miles).

Planet Plotting

Venus (-4.1) in Taurus and Gemini will have a brighter crescent in June and July, and reaches maximum eastern elongation on June 9th. However the best viewing may be in May when Venus displays its gibbous phase in the western sky and sunset is still early enough to limit interference by twilight glare. Saturn (0.4) remains almost stationary between Leo and Cancer in May, yet it appears to close in on Venus because the latter moves eastward in the sky faster than the glare of sunset progresses due to Earth's revolution. Mercury (-1.0), also in Taurus and Gemini, presents its best apparition of 2007 in May as it approaches maximum eastern elongation on June 2nd.

Jupiter (-2.5) is in Ophiuchus and rises slightly before midnight at the beginning of May. By month's end it rises at 9:30 PM EST and dominates the night sky after the setting of Venus.

Mars (1.0) in Aquarius and Pisces rises 2.5 hours before the Sun and will brighten to magnitude 0.8 by the end of May, this is the beginning of an 8 month ascent which will culminate in a Christmas Eve opposition and a magnitude of -1.6. Although this is about 1.0 magnitude dimmer than the glorious opposition of 2003 and about 0.5 magnitudes dimmer than that of 2005, the Red Planet will brighten the Christmas sky and light the way for Santa and his reindeer. Uranus (5.9) is in Aquarius all month, and is close to Mars on May 1st. It will rise higher in the predawn skies than does Mars in May because the dawn glare comes earlier and retreats rapidly to the east while Mars moves eastward at a slower pace. Neptune in Capricornus is much dimmer (8.0), but is more distant from the glare of sunrise.

Meteors

The Eta Aquarid Meteor Shower of May 5th is joined by minor Sagittarid Showers in May. The Eta Aquarids Meteors are from a cloud of remnants of Comet Halley, which last passed this way in 1986. Unfortunately, up to 60 meteors per hour viewed well before dawn in dark sky locations will be washed out by glare from the nearby gibbous Moon. We will have a second shot to view a different part of this cloud in September when the Orionid Meteor Shower displays more remnants from Comet Halley.

May Moons

Even though this is a Blue Moon month, don't count on seeing a beautiful azure globe in the night sky. Violet, blue, green or lavender suns and moons result from airborne particles reflecting the red end of the spectrum of light entering Earth's atmosphere. The particles are typically as large or larger than the wavelength of light reflected. Forest fire smoke particles and volcanic eruption particles are of appropriate size and have sporadically created this phenomena throughout history. The rarity of these "Blue Moons" may have instigated the phrase in a 1528 poem that made reference to the absurdity of a "Blue Moon" and led to the definition as an infrequent occurrence which was reinforced by the mid-19th century phrase "once in a blue moon."

The great cultural transition to agriculture from human hunter-gatherer roots was made possible by a change from a lunar to a solar calendar. The period of Earth revolution around the Sun is not an even multiple of the period of lunar revolution, so the number of full moons in a year varies from 12 to 13, requiring a variation in the number of days per month in order to create a constant 12 months per year. If months were still defined solely by the phases of the Moon, there would be 12.37 months per year, and in 16.5 years, December would be occurring in the middle of summer in the northern hemisphere.

In each 19 year interval, 7 years will contain 13 months. During those years, one of the 4 seasons will have 4 full Moons. The 3rd full Moon of that season is called a "Blue Moon", making the Full Moon of May 31, 2007 a "Blue Moon".

The definition as the "second full moon in a month" arose from a mistake in a 1946 issue of Sky and Telescope in which the author deduced that 13 full moons in a year meant that one month probably had two full moons. This definition was then popularized on the 1980 radio show "Stardate", and spread far and wide by the game "Trivial Pursuit." The definition is now a part of popular culture and will not go away. The Full Moon of the 31st meets both definitions.

The 1st Full Moon of May is on the 2nd at 6:09 AM EDT, and the Blue Moon is at 9:04 PM EDT on the 31st. On the 5th, the waning gibbous Moon is 6° south of Jupiter at 8 AM EDT and the last quarter Moon is 1.8° south of Neptune at 4 AM EDT on the 10th. On the 12th, the waning crescent Moon is 3° north of Mars at 9 PM EDT, and a brand new waxing crescent is 3° north of Mercury at 8 PM EDT on the 17th. The crescent Moon then passes 1.7° north of Venus at 9 AM EDT on the 19th, and 0.8° north of Saturn at 3 PM EDT on the 22nd.

via CloudyNights