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April Skies


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April Skies

by Dick Cookman

04/1/2014

Highlights: Comet Journal, Martian Landers, Meteor Showers, Galaxies Galore, Planet Plotting, April Moon

Focus Constellations: Cassiopeia, Camelopardalis, Lynx, Ursa Major, Ursa Minor, Cepheus, Draco, Bootes, Canes Venetici, Coma Berenices, Virgo, Leo, Cancer

Comet Journal

Comet C/2012 X1 (LINEAR) and Comet C/2012 K1 (PanSTARRS) are the spring comets for 2014. Both are at 8th magnitude and will remain that bright until July. PanSTARRS circuits on a path north of Bootes and below the handle of the Big Dipper in April and is visible throughout the night. LINEAR is an early morning apparition as it moves westerly along a path north of Capricornus.

PanSTARRS is dropping into the plane of the solar system along a steeply inclined orbit. It passes above Earth in April, reaches perihelion on the other side of the Sun on August 27th and may reach 6th magnitude when closest to and below Earth in southern hemisphere skies in November. LINEAR is on a similar less inclined path and will descend through the solar system plane in May and be nearest to Earth on June 27th.

Mars Landers

Opportunity is on Solander Point on the rim of Endeavor Crater. It is climbing the highest hill encountered during the mission's ten years on Mars. The hill is part of Murray Ridge rising southward from Solander Point as a ridge forming an elevated portion of the western rim of the 14 mile (22 kilometer) diameter crater. The ridge materials were uplifted by the great impact that excavated the crater billions of years ago, reversing the common geological pattern of older materials lying lower than younger ones.

The rover is analyzing a number of rocks and rock outcrops on the ridge. Between Sol 3588 (Feb. 26, 2014) and Sol 3609 (March 19, 2014) Opportunity traveled 158 ft. (50 meters) in the process of examining targets at four different sites.

Solar array energy production rose about 10% during the interval to 558 watt-hours per day as a result of a wind-induced solar panel dust cleaning event in mid-March.

In search of a smoother route to avoid escalation of the damage done by sharp rocks to the aluminum wheels since landing on Mars, the Science Laboratory rover, Curiosity, cut through a shallow valley called Dingo Gap blocked by a 3 foot high sand dune. After crossing the dune on February 9th, Curiosity proceeded southwestward along the smoother route toward Kimberly, the next drilling site.

On Feb. 18th mission scientists turned the rover around and initiated a backwards drive of 329 ft. (100.3 meters) as a test for more extensive backwards driving which may be required on rougher routes. During the trip, the rover passed a tilted sequence of layered rocks dipping in the direction of travel toward Mt. Sharp. The rock layers were overturned by the impact that excavated Endeavor Crater so the "downdip" direction of travel which typically leads to younger rock layers in this case produces older rock layers which are turned upside down. The impact peeled back preexisting rock layers and flopped them over as if a bomb were fired into a gigantic layer cake.

Meteor Showers

April hosts the Lyrid meteor shower first recorded by the Chinese in 687 BC. The shower is refueled every 415 years by debris lost from Comet C/1861 G1 Thatcher which last visited the inner solar system in 1861. The Lyrids, which peak on the morning of the 22nd and can be seen between the 16th and 25th, typically produce 15 to 20 meteors per hour in dark skies. The shower seldom approaches displays of 100 or more meteors/hr., but over 250 meteors/hr appeared for a short period of time in 1982. Lyra rises in the northeast after 10PM EDT and the best viewing will be high in the south in the predawn hours.

Galaxies Galore

April is one of the best months for evening observation of galaxies. A band of some of the most magnificent bright elliptical and spiral galaxies visible from Earth can be scanned north-northeastward from the gigantic Virgo Supercluster of galaxies. The band streches along a line sub-parallel to the axis of our galaxy. It passes by the tail of Leo and extends to the north pole of the Milky Way in Coma Berenices, then through Canes Venetici and the cup of the Big Dipper to M-81/M-82 northwest of Dubhe in Ursa Major.

Planet Plotting

In April, the evening planets which span the sky from west to southeast include Jupiter (-2.2 to -2.0) in Gemini, Mars (-1.3 to -1.4 to -1.2) in Virgo, and Saturn (+0.3 to +0.1) in Libra.

Mars is at opposition at 5PM EDT on the 8th when Earth is precisely between Mars and the Sun. Mars is closer to Earth and brighter than at any other time during the 4 year interval between the last opposition in 2012 and the next one in 2016. The Red Planet rises at sunset and sets at sunrise, and even small backyard telescopes will reveal surface patterns and details normally restricted to larger instruments.

Mars oppositions differ in terms of distance from Earth and apparent size and brightness of the disk. When closest, Mars can equal or even exceed Jupiter's brightness. During the last 60 years close oppositions occurred in 1956, 1971, 1988, and 2003. The latter was the closest of the four at 34.69 million miles, a distance matched only 4 times in the last 400 years.

I was fortunate enough to witness the 1956 opposition when Mars was 35.25 million miles distant. Martian proximity initiated my interest in astronomy, inspiring me to purchase a telescope and embark on a extended program of Mars observation and sketching.

Bright Jupiter rises in the afternoon and sets after midnight, and Saturn rises in mid-evening and sets after sunrise. Jupiter dominates the evening sky in the southwest and west and Saturn is easily seen in the east and southeast.

Morning planets are limited to brilliant Venus (-4.4 to -4.2) in Capricornus and Aquarius and Neptune (+7.9) in Aquarius. Venus rises two hours before sunrise in April while Neptune rises an hour and a half before the Sun on the 1st and 2.5 hours earlier than sunrise on the 30th.

Uranus in Pisces and Mercury in Capricornus and Aquarius are buried in twilight. Each planet has a conjunction with the Sun on April 2nd and April 21st respectively.

PlanetConstellationMagnitudePlanet Passages
SunPisces, Aries-26.8New Moon, 4/29, 2:14AM EDT
SunPisces, Aries-26.8Uranus Conjunction, 4/2, 3:00AM EDT
MercuryAquarius, Pisces, Aries-0.2 to -1.6Superior Conjunction, 4/21, 11PM EDT
VenusCapricornus, Aquarius-4.4 to -4.2Neptune, 0.7°S, 4/12, 4AM EDT
MarsVirgo-1.3 to -1.4 to -1.3Opposition, 4/8, 5PM EDT
JupiterGemini-2.2 to -2.0 
SaturnLibra+0.3 to +0.1 
UranusPisces+5.9Solar Conjunction, 4/2, 3AM EDT
NeptuneAquarius+7.9Venus, 0.7°N, 4/12, 4AM EDT

April Moon

The New Moon on March 30th marks the beginning of Lunation 1129 which ends 29.20 days later with the the New Moon of April on the 29th at 2:14AM EDT. The New Moon of April coincides with an annular Solar Eclipse limited to the southern Indian Ocean and Antarctica.

The Full Moon of April is the first full moon after the Spring Equinox so the following Sunday is Easter. The Full Moon in Virgo on the 15th at 3:41AM EDT passes through the shadow of the Earth and is totally eclipsed for observers in western South America, Central America and most of North America excepting New England, Maritime Canada and Alaska. Mid eclipse at the zenith occurs slightly north of Easter Island. The next Total Lunar Eclipse in October will be less accessible for observers in eastern North America as it is centered farther west in the Pacific.

According to Alan MacRobert in April's Sky & Telescope Magazine, the eclipse starts with the penumbral stage at 1:20AM EDT and is followed by the partial stage at 1:58AM EDT. Totality begins at 3:07AM EDT with mid-eclipse at 3:45AM EDT and ends at 4:25AM EDT. The exiting partial stage ends at 5:33 AM EDT followed by the exiting penumbral stage. The Moon may assume a reddish color due to light passing around the solid Earth and through our atmosphere. During passage, the blue end of the spectrum is scattered by Earth's atmosphere. The residual light which is shifted toward the red is refracted so that which passes Earth and heads toward the Moon can be reflected back to Earth. The color may be intensified and darkened by volcanic eruptions occurring prior to and during the eclipse, and observers may even see ephemeral shadows caused by clouds in the atmosphere along the Earth's rim.

The April Moon was traditionally named the "Planter's Moon" in Colonial America. For Celts it was “Growing Moon” and Chinese call it the “Peony Moon." To Medieval English it was “Seed Moon” and the Anishnaabe people (Chippewa and Ojibwe) of northern Michigan celebrate it more realistically for 2014 as “Iskigamizige-giizis(oog)” (Broken Snowshoe Moon).

The Moon is at the farthest point in its orbit, 251,334 miles (63.42 Earth Radii) from Earth at apogee on the 8th at 10:52AM EDT. Perigee, at a distance of 229,761 miles (57.97 Earth Radii), is on the 27th at 8:24PM EDT.

PlanetConstellationMagnitudeMoon PassageMoon Phase/Age
SunAries-26.82:14AM EST, 4/29New ~ 0 days
MercuryAries-1.91.6°S, 2PM EDT, 4/29Waning Crescent ~ 26.69 days
VenusAquarius-4.24.0°N, 7PM EDT, 4/25Waning Crescent ~ 25.90 days
MarsVirgo-1.43.0°S, 2PM EDT, 4/14Waxing Gibbous ~ 14.69 days
JupiterGemini-2.25.0°S, 7PM EDT, 4/6Waxing Crescent ~ 6.90 days
SaturnLibra+0.20.4°S, 3AM EDT, 4/17Waning gibbous ~ 17.23 days
UranusPisces+5.92.0°N, 7AM EST, 4/27Waning Crescent ~ 27.40 days
NeptuneAquarius+7.95.0°N, 6PM EDT, 4/24Waning Crescent ~ 24.85 days




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