April 2015 – Skies News
April Skies by Dick Cookman
Highlights: Comet Journal, Martian Landers, Meteor Showers, Easter, Planet Plotting, April Moon
Focus Constellations: Draco, Cepheus, Cassiopeia, Perseus, Camelopardalis, Auriga, Taurus, Gemini, Canis Minor, Cancer, Leo, Lynx, Coma Berenices, Bootes, Ursa Major, Ursa Minor
Comet Journal
Comet 88P/Howell (2015) is at 8th magnitude. After perihelion with the Sun on April 6th, it moves from Capricornus to eastern Aquarius which rise in the southeast slightly before the Sun. The comet & Sun appear to move through constellations at the same rate, causing maintenance of the same time interval between comet rise and sunrise all month.
Comet C/2014 Q2 (Lovejoy) is between Cassiopeia and the North Star in April and will pass the North Star in late May. It is at 7th magnitude and will dim after passing Polaris when it will have diminished to 9th magnitude.
C/2014 Q1 (PanSTARRS), currently on the other side of the Sun, is very dim at 13th magnitude. It will brighten and may be visible to naked eyes this summer when reaching 4th magnitude near perihelion when it is closest to the Sun.
Mars Landers
Between February 16th and March 24th, Opportunity successfully completed reformatting of the flash system and installing new flight software and was able to again use flash for nonvolatile data storage.
In addition, the rover was able to complete inspection of an unusual purple colored rock formation named “Sgt. Nathaniel Pryor” not yet observed on Mars. The formation was found in the west rim region of Endeavour Crater near Marathon Valley. The robotic arm used the Microscopic Imager (MI) to collect an image mosaic, then placed the Alpha Particle X-ray Spectrometer (APXS) to collect a multi-hour measurement of the elemental composition of the target. During the month, Opportunity managed to travel over 600 feet in its journey to the site in Marathon Valley where satellite imaging revealed an abundance of clay minerals which may retain complex organic molecules possibly indicative of ancient Martian life. The rover has now traversed 26.241 miles (42.230 kilometers) over the Martian surface. Solar energy in the last month has increased from 554 to 610 watt hours per day.
Curiosity experienced an onboard fault protection action three days after drilling at “Telegraph Peak” on February 24th. The action prevented transfer of the collected sample of drilling powder between devices on the robotic arm. The protection action resulted from detection of a short circuit and the rover was expected to remain stationary with rover arm movement suspended for several days in order to trace the circuit fault. Examination of the event revealed that the 1/100th second short circuit event experienced on Feb. 27th was a transient event in the drill’s percussion motor. Guidelines are being developed to avoid repetition in the future.
On March 11th, Curiosity used its robotic arm to deliver the sample to the Chemistry and Mineralogy (CheMin) instrument inside the rover for analysis. The ensuing trek away from the sites in Pahrump Hills that were examined from September, 2014 to March, 2015 involves a continuation of the climb of Mt. Sharp, the layered mountain in the center of Gale Crater. The mountain exposes some of the oldest rock layers on the planet with progressively younger layers stacked above revealing a detailed history of environmental change.
The Sample Analysis at Mars Instrument suite (SAM), detected nitrogen in nitric oxides released during heating of previously collected sediments, another indication that ancient Mars had the elements necessary for life. Nitric oxides can be released by the breakdown of nitrates during heating. The likely presence of nitrates in windblown dust sediment attests to the probability of their widespread presence on the planet.
Nitrogen is a vital component of the nucleic acids (RNA & DNA) and proteins. Nitrates are biochemically accessible forms of nitrogen produced by some organisms on Earth and can also result from lightning, meteorite impacts, and other non-biological processes, so they are not prima facie evidence for life. However, they are one of the substances required for life on Earth, and their presence on Mars along with previous discovery of evidence for energy sources, liquid water, and the other chemical components of organic molecules encourages continuation of the search for ancient life on Mars.
Meteor Showers
2015 is a favorable year for the Lyrid meteor shower on April 23rd. Lyra rises in the northeast slightly before 10PM EDT and is overhead in the hours before dawn when our side of the Earth is plunging headfirst into the river of debris left by the long period Comet C/1861 G1 Thatcher during previous passages through the inner solar system. Glare from the waxing Crescent Moon which sets before midnight will provide no competition for the shower, so observers can choose a dark sky location, recline on a comfortable lounge or blanket, and watch meteors shooting out in all directions from Lyra.
Easter
Easter Sunday is on the 5th of April following the Full Moon on the 4th which was the 1st Full Moon after the Spring Equinox on March 20th. Many early cultures in the Northern Hemisphere celebrated the Spring Equinox as the beginning of the year because it marked the time when daylight hours began to exceed the hours of darkness. Thus the Full Moon closest to the equinox was considered special, leading church authorities to observe Easter on the Sunday following the Full Moon closest to the Spring Equinox. Dates for Palm Sunday, Good Friday, Ascension Day, and Pentecost/Whitsunday are all in turn based on the date for Easter.
Since the Full Moon closest to the equinox may occur within one half (+/-) of a lunar month on either side of the equinox, the timing of Easter has and will occur between March 22nd and April 25th between 1761 and 2380.
Planet Plotting
Evening planets in April include Mercury, Venus, Earth (when you look down), Mars, and Jupiter.
Mercury (-1.1 to -2.2) is within 1° of Uranus in Pisces before sunset on the 8th, reaches superior conjunction on the 9th, and is slightly more than 1° from Mars in Aries after sunset on the 22nd.
Venus (-4.0 to -4.1) appears to move through the star background slightly faster than the Sun causing the planet to remain above the western horizon for about 3 hours after sunset throughout the month. On the 10th it will be close to the Pleiades and will be in southern Taurus on the 21st when it is approached by a thin waxing crescent Moon. The Anishnaabe (Ojibwe) name for Venus is “Ikwe’ anung” (Women’s Star), nigaabii-anang (Evening Star), or waaban-anang (Morning star).
Annette S. Lee of St. Cloud University, who is engaged in preserving and recovering indigenous astronomy, points out that Native Americans related Venus to human gestation and femininity because the planet appears in the morning for nine months then becomes an evening planet for the next nine months.
Mars (+1.4) is low in the western sky in Aries after sunset and is 1.3° from Mercury on the 22nd. Mars and an extremely thin waxing crescent Moon form a superb pairing on the 19th.
Jupiter (-2.5 to -2.3) rises in Cancer during the afternoon. It dominates the eastern and southern sky in evening and the and moves to the western skies before setting in the wee hours.
Saturn in Scorpius, Uranus in Pisces, and Neptune in Aquarius are morning planets. The former rises before midnight and increases in brightness in April before its late May opposition. It is brighter than Antares, the nearby red supergiant.
Planet……Constellation……Magnitude……Planet Passages
Sun……..Pisces, Aries………-26.8……………New Moon, ………………………………………………………4/18, 2:57PM EDT Mercury..Pisces, Aries, Taurus..-1.1 to -2.2…Superior
……………………………………………………………..Conjunction, ……………………………………………………….4/9, Midnight EDT
……………………………………………………….Uranus, 0.46°NNW ………………………………………………………..4/8, 9AM EDT
………………………………………………………..Mars, 1.3°SSE
………………………………………………………..4/22, 4PM EDT
Venus…..Aries, Taurus………-4.0 to 4.1
Mars……..Aries…………………+1.4…………Mercury, 1.3°NNW …………………………………………………………4/22, 4PM EDT Jupiter…..Cancer………………-2.3 to -2.1
Saturn…..Scorpius…………….+0.3 to +0.1
Uranus….Pisces………………..+5.9
………………………………………………………..Solar Conjunction …………………………………………………………4/6, 10AM EDT ………………………………………………………..Mercury, 0.46°SSE …………………………………………………………4/6, 10AM EDT
Neptune…Aquarius…………..+7.9
April Moon
Lunation 1142 started with the New Moon of March at 5:36AM EDT on the 20th. It will end 29.39 days later with the New Moon of April at 2:57PM EDT on the 18th.
April’s Full Moon in Virgo at 8:06AM EDT is on the 4th. It is the “Egg, Grass, Easter, or Paschal Moon.” Colonial Americans called it the “Planter’s Moon”, Celts called it the “Growing Moon”, and Medieval English referred to it as the “Seed Moon.” Chinese call it the “Peony Moon” and Anishnaabe (Odawa and Ojibwe) of northern Michigan call it “Iskigamizige-giizis(oog)” (Maple Sap Boiling Moon) or (Broken Snowshoe Moon).
The Full Moon provides a brief early morning total eclipse at 8:06AM EDT on the 4th. Observers east of the Mississippi are restricted to a short partial eclipse stating about 6:16AM EDT. Westerners may see up to 4 minutes of totality.
Apogee distance (maximum distance) is 252,284 miles (63.66 Earth Radii) from Earth on the 1st at 9:01AM EDT. The Moon is nearest (perigee) in its orbit (224,329 miles or 56.60 Earth Radii) on April 16 at 11:48PM EDT.
Planet..Constellation…….Magnitude……..Moon Passage
……………………………………………………Moon Phase/Age
Sun………Pisces……….-26.8………….5:36AM EDT, 3/20 ……………………………………………………..New ~ 0 days Mercury..Aries………….-1.3………3.4°SSE, 9AM EDT, 4/19 …………………………………………Waxing Crescent ~ 0.75 days Venus…..Taurus……….-4.1………7.0°S, 2PM EDT, 4/21 …………………………………………Waxing Crescent ~ 1.96 days
Mars…….Aries………….+1.4……3.0°SSE, 4PM EDT, 4/19 ………………………………………….Waxing Crescent ~ 1.04 days Jupiter….Cancer………..-2.1……….5.0°S, 2PM EDT, 4/26 ………………………………………….Waxing Gibbous ~ 6.96 days Saturn….Scorpius………+0.3……….2.0°N, 9AM EDT, 4/8 ………………………………………….Waning Gibbous ~ 19.14 days Uranus….Pisces…………+5.9………0.1°SW, 9PM EDT, 4/17 ………………………………………….Waning Crescent ~ 28.64 days Neptune..Aquarius……..+7.9……..4.0°N, 9AM EDT, 4/15 ………………………………………….Waning Crescent ~ 26.14 days