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April 2016 Skies

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April Skies

by Dick Cookman


Highlights: Comet Journal, Martian Landers, Meteor Showers, Mother Goose and the Headlands, Planet Plotting, April Moon

Focus Constellations: Camelopardalis, Ursa Major, Ursa Minor, Draco, Cepheus, Cassiopeia, Perseus, Auriga, Taurus, Gemini, Cancer, Lynx, Leo, Coma Berenices, Canes Venatici, Bootes, Hercules

Comet Journal

There are two comets at or approaching naked eye visibility in April night skies. Comet 252P/LINEAR (2016) is between magnitudes 5 and 6 and near its peak brightness after passing through perihelion last month when it was about 3 million miles south of Earth. It moved into northern skies at the end of March and will circle through Ophiuchus during the Spring and early Summer as it moves outward toward and beyond Jupiter's orbit.

Comet C/2013 X1 (PanSTARRS) is about 8th magnitude between Pisces and Aquarius and is getting brighter as it approaches perihelion on the 20th. In mid-June, it may reach 6th magnitude when passing within 56 million miles of Earth between the orbits of Earth and Mars. It will appear south of Capricornus in morning skies.

Mars Landers

Opportunity is up on the steep slopes of "Knudsen Ridge" in Marathon Valley on the rim of Endeavour crater. On Sol 4297 (Feb. 24, 2016), the rover performed its first contact measurements of an exposed rock named "Charles Caugee" and followed that up on Sols 4299 - 4302 by moving 6.0 meters uphill toward another target "Pvt. Joseph Whitehouse". The gravely slopes in excess of 30° prevented further progress toward the target despite numerous attempts in the following 11 sols so the effort was abandoned. Even though Opportunity failed in its attempts to reach the target, the interval provided valuable information as the rover was able to conduct a wide variety of remote sensing measurements of the surrounding environments.

On Sol 4316 (March 15, 2016), Opportunity moved further downhill, driving about 22 feet (6.7 meters) north to set up for a longer drive towards the next science target along "Knudsen Ridge". On Sol 4320 (March 19, 2016), the rover drove about 31 feet (9.5 meters) to the southwest towards areas with spectral signatures of phyllosilicate clays from satellite measurements. Supporting Navcam and Pancam panoramas were collected after the drive to prepare for the next drive. On Sol 4323 (March 22, 2016), Opportunity headed due west about 41 feet (12.5 meters).

From Sol 4325 (March 24, 2016) through Sol 4330 (March 29, 2016), the rover drove 142 feet (44 meters) to reach the clay area and proceeded to document the terrain with extensive Pancam color (multi-filter) panoramas. As of Sol 4330 (March 29, 2016), the solar array energy production has increased to 650 watt-hours and the total distance Opportunity has traveled on Mars is 26.55 miles (42.74 kilometers).

On Sol 1275 (Mar. 5, 2016), Curiosity reached the finely laminated rock at the boundary between the "Murray Formation" and the overlying "Stimson Formation", a short distance from a target with rather interesting knobby nodules. The next 6 sols were devoted to collection of nodule laser data with the ChemCam and then the rover ascended the slope from the edge to the top of the "Stimson Formation" which is called the "Naukluft Plateau". Mission scientists planned to cross the rugged terrain of the plateau and to collect data from various targets in the process. The rover drove for the next 20 sols and by Sol 1302 traveled over 200 meters over the plateau making numerous atmospheric, panoramic and sedimentary structure observations along with bedrock outcrop chemistry analyses.

Meteor Showers

The best meteor shower in April is the Lyrids in the predawn hours of the 22nd which, sadly, coincides with the night of the Full Moon. One to two hours before sunrise, the Moon will be in the western sky and Lyra will be high the south at the best viewing time for the shower which normally displays fairly bright meteors that may stand out in the moonglow. The shower occurs when Earth plunges through the trail of debris shed from Comet C/1861 Thatcher, last seen 155 years ago.

Mother Goose and the Headlands

Mary Stewart Adams is the program director for the Headlands Dark Sky Park near the straits of Mackinaw in Emmet County, Michigan. She is an English literature graduate from the University of Michigan who led the initiative to have the International Dark Sky Society in Tucson, Arizona recognize the Headlands as one of the first ten International Dark Sky Parks in the world in 2011. Now there are 20 and the Headlands is the only recognize dark sky park in Michigan.

Mary is a renowned expert on constellation stories and mythology, presenting the role of sky observation in the development of literature and the cultural history of humanity's relationship to the night sky. Many writers utilized celestial events as inspiration for their creations.

As an example, Enerdyne sponsored the "Midwest Space Fest" in the Fall of 2013 where she presented a wonderful story about the inspiration for the Mother Goose tales.

The following is my attempt to communicate the sense of her story:

Hey diddle diddle, the cat (Leo) and the fiddle (Lyra), the cow (Taurus) jumped over the Moon (see 4/10 to 4/12 this month). The little dog (Canis Minor) laughed to see such a sight, and the dish (Milky Way) ran away with the spoon (Big Dipper).

She has a plethora of similar examples which she presents as part of the program offerings which she hosts at the Headlands and at events and conferences to which she is invited throughout the world. I highly recommend any opportunity to attend her presentations which are always educational and entertaining.

The Headlands is a county park supported by Emmet County and donations. Rental facilities are available in the park and there is camping, motels, and hotels in neighboring Mackinaw City.

As mentioned above, the Headlands has very active public program —— from star parties to viewing of celestial events, northern lights, birding events and activities, dances, hiking, winter sports, and other activities. As can be seen on their fascinating website at: www.midarkskypark.org, the park is located in one of the most spectacularly beautiful areas of the United States, on the shores of Lake Michigan.

Planet Plotting

April's morning planets include brilliant Venus (-3.8 to -3.9) in Pisces and Neptune (+7.9) in Aquarius. Venus rises about an hour before sunrise in early April and draws closer to the Sun as it approaches solar conjunction in June. After the conjunction, Venus will make a brilliant reappearance in evening skies. Best viewing of Venus in April is early in the month before it drops too deeply into the glow of sunrise. It makes an attractive pairing with the waning crescent Moon in the predawn hours on April 6th. Uranus (+5.9) in Pisces reaches conjunction with the Sun on the 9th and rises slightly before the Sun in late April.

Mars (-0.5 to -1.4) moves from Scorpius and Ophiuchus in April and along with Saturn (+0.3 to +0.2) in Ophiuchus rises before midnight. They are low in the west before dawn. Mars is approaching opposition on May 22 when it will reach magnitude -2.1, outshining everything but Jupiter and the Moon in the night sky. By the last half of April it will already be close enough to see surface details in good 4 to 6 inch telescopes. The polar caps are subdued because the southern cap is tilted away from Earth and the northern cap is reduced by the long northern Martian summer. On the nights of the 24th - 26th, Saturn, Mars, Antares, and a large waning gibbous Moon make an impressive show in the southern sky in the hours after midnight.

Mercury (-1.5 to+2.7) is progressively higher in the west-northwest evening sky in April as it moves from Pisces into Aries putting on its best show for 2016. Jupiter (-2.4 to -2.3) in Leo passed through opposition last month and is still very bright. It dominates the southeastern evening sky, surpassed only by the Moon.

PlanetConstellationMagnitudePlanet Passages
SunPisces, Aries-26.8New Moon, 4/7, 7:24PM EDT
MercuryPisces, Aries-1.5 to +2.7Max. East Elongation 4/18, 10:00AM EDT
VenusPisces-3.8 to -3.9 
MarsScorpius, Ophiuchus-0.5 to -1.4 
JupiterLeo-2.4 to -2.3 
SaturnOphiuchus+0.3 to +0.2 
UranusPisces+5.9Solar Conjunction 4/9, 5:00PM EDT

April Moon

The New Moon on April 7th at 7:24AM EDT marks the beginning of Lunation 1154 which ends 29.34 days later with the New Moon on May 6th at 3:30PM EDT.

April's Full Moon is in Virgo and occurs at 1:24AM EDT on the 22nd. It was referred to as the "Planter's Moon" in Colonial America. Celts referred to it as “Growing Moon” and Chinese call it “Peony Moon." To Medieval English it was the “Seed Moon” and Anishinaabe (Chippewa and Ojibwe) of northern Michigan celebrate it as the “Iskigamizige-giizis(oog)” (Sugarbushing Moon).

Perigee distance is 221,931 miles or 56.00 Earth radii on the 7th at 1:36PM EST. This is the second closest perigee of 2016 and almost coincides with new moon, causing ocean tides to be higher than normal. The Moon is at the apogee position in orbit (maximum orbital distance) at 252,495 miles (63.71 Earth radii) from Earth on the 21st at 12:05PM EDT.

PlanetConstellationMagnitudeMoon PassageMoon Phase/Age
SunPisces-26.87:24AM EDT, 4/7New ~ 0 days
MercuryPisces-1.05.0°S, 7AM EDT, 4/8Waxing Crescent ~ 0.98 days
VenusPisces-3.80.7°N, 4AM EDT, 4/6Waning Crescent ~ 28.80 days
MarsOphiuchus-1.25.0°N, Midnight EDT, 4/24Waning Gibbous ~ 16.69 days
JupiterLeo-2.32.0°S, 1AM EDT, 4/18Waxing Gibbous ~ 10.73 days
SaturnOphiuchus+0.23.0°N, 3PM EDT, 4/25Waning Gibbous ~ 18.32 days
UranusPisces+5.91.9°SSE, 11AM EDT, 4/7Waxing Crescent ~ 0.15 days
NeptuneAquarius+7.91.9°N, 6AM EDT, 4/4Waning Crescent ~ 27.50 days


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