April Skies – by Dick Cookman
Highlights: Comet Journal, Martian Landers, Meteor Showers, Planet Plotting, Spring Skies, April Moon
Focus Constellations: Auriga, Taurus, Gemini. Cancer, Leo, Leo Minor, Coma Berenices, Bootes, Corona Borealis, Ursa Major, Ursa Minor, Draco, Cepheus, Cassiopeia, Camelopardalis, Lynx
C/2018 Y1 (Iwamoto) is an evening comet at 10th magnitude in Perseus which sets after 8:00PM EDT in April. It passed through perihelion south of western Virgo on Feb. 6 and was closest to Earth (28 million miles) in Leo on Feb. 11 & 12. It will move eastward until July after which it will move north northwestward through Perseus as it exits the inner solar system and returns to its aphelion between the Oort Cloud (10000+ AU’s) and Kuiper Belt (30 – 50 AU’s), the normal homes for longer period comets.
Opportunity’s mission is complete as of Sols 5347 to 5353 (Feb. 7, 2019 – Feb. 13, 2019). No response has been received from Opportunity since Sol 5111 (June 10, 2018,) due to a planet-encircling dust storm on Mars. With the last uplink transmission on Sol 5352 (Feb. 12, 2019), the rover recovery efforts are concluded. Total odometry on Mars for the rover was 28.06 miles (45.16 kilometers).
After arriving in Elysium Planitia on Mars on Nov. 26, the InSight lander unfurled its solar panels and radio antennas. Preliminary deployment of the seismometer on the Martian surface was achieved on December 19. Space.com states: “InSight’s Heat Flow and Physical Properties Package (HP3) instrument burrowed underground for the first time on Feb. 28. The main goal of NASA’s InSight lander, which arrived on the Red Planet in November 2018, is to measure underground heat flow and seismic activity. That isn’t going quite as planned as the drill encountered rocks through which it could not yet penetrate. However, the lander is using one of its less important sensors to make the very first measurements of Mars’s magnetic field from the surface, which may help to find ground water at depth.
Curiosity Rover is investigating 16,404 foot Mt. Sharp at Gale Crater’s center in its search for evidence of pre-existing life on Mars. Curiosity is within Glen Torridon the clay-bearing unit adjacent to Vera Rubin Ridge which was the target of investigation of the rovers activities for the past 17 months. Clay minerals in this unit may hold more clues about the ancient lakes that helped form the lower levels on Mt. Sharp.
In November, the rover’s computer suffered a reset due to a memory failure which caused mission scientists to shut down the computer and to bring the backup computer on line. The issue was corrected by reformatting the computer and isolating the suspect memory chips. On February 15, a hiccup during boot-up interrupted planned activities and triggered a protective safe mode. The rover exited this mode on Tuesday, Feb. 19, and operated normally. On March 6, 2019 (Sol 2,339) Curiosity experienced a computer reset that triggered another safe mode. This was the second computer reset in three weeks; both resets were related to the backup computer’s memory. The mission team decided to switch back to the repaired computer and proceed with analysis of the clay-bearing unit which features several low, linear ridges of sand near the rover. These are shaped by the winds, which have herded the sand grains into transverse dunes. On Sol 2356, the rover targeted Stonebriggs and imaged densely packed round and smooth rocks possibly shaped by water currents. Wind tends to create flat, faceted surfaces due to sandblasting.
Apr. 22: Lyrids. Peak 22hr 30min UT Active Apr 16-25.
Radiant 18h04m -34°. ZHR ~var<90. 49 km/sec. 3 days after Full Moon. Progenitor: Comet C/1861 G1 (Thatcher)
Apr. 24: Pi Puppids Peak 4 UT Active Apr 15-18. Radiant 07h20m -45°. ZHR ~0-40. 18 km/sec. 5 days after Full Moon. Progenitor: Comet 26P/Grigg-Skjellerup
Jupiter (-2.1 to -2.3) in Ophiuchus, Saturn (+0.6 to +0.5) in Sagittarius, Mercury (+0.9 to -0.3) and Venus (-3.9 to -3.8) in Aquarius and Pisces, and Neptune (+8.0 to +7.9) in Aquarius are morning planets in April. They are visible in the southeastern sky with Jupiter rising about 1:30AM EDT in early April, followed by Saturn an hour and a half later, and the last three rise in the twilit skies of dawn. One of April’s highlights occurs on the 3rd when the Moon, Mercury, and Neptune are within a circle of diameter 3.39°; 26° west of the Sun. At the end of April, Jupiter rises before midnight, Saturn rises about 1:15AM EDT, and sunrise is an hour earlier than on April 1. During the month, Venus will sink deeper into the glow of sunrise as it appears to move closer to Mercury, and Neptune will move higher in the dawn sky.
Uranus (+5.9) in Aries and Mars (+1.5 to +1.6) in Taurus are evening planets in April. Uranus may appear briefly on the western horizon after sunset on the 1st but will then disappear for the month as it reaches conjunction with the Sun on the 22nd. Mars is high in the early evening western sky and does not set until after 11:00PM EDT throughout April.
The waning crescent Moon is 3° from Venus at midnight EDT on the 1st, 3° from Neptune and 4° from Mercury at 7:00PM EDT on the 2nd, and 3° from Neptune at 4:00AM EDT on the 30th. Its waxing crescent is 5° from Uranus at 9:00AM EDT on the 6th and 5° from Mars at 3:00AM EDT on the 9th. A waning gibbous Moon is 1.6° from Jupiter at 6:00AM EDT on the 23rd and 0.4° from Saturn at 10:00AM EDT on the 25th.
Sun..Aquarius, Pisces, Aries..-26.8..New Moon..4:50AM EDT..4/5
Mercury..Aquarius, Pisces…-0.9 to +0.3……Neptune, 0.4°S, ……………………3:00PM EDT, 4/2 …………………Max. West Elong. …………………./……….4:00PM EDT..4/11
Venus…..Aquarius, Pisces…-3.9 to -3.8…….Neptune, 0.3°S, ……………Midnight, 4/9
Mars……Taurus……………….+1.5 to +1.6
Jupiter…Ophiuchus………….-2.1 to -2.3
Saturn…Sagittarius………….+0.6 to +0.5
Neptune..Aquarius…………..+8.0 to +7.9 …..Mercury, 0.4°N,………..3:00PM EDT..4/2
……………………………………………………….Venus, 0.3°N,……………..Midnight, 4/9
The spring evening sky serves as an entry into infinity and helps us determine directions. In addition it provides a means of keeping time.
During April and May, the zenith hosts the Milky Way’s north galactic pole in Coma Berenices. When we view the zenith, the plethora of stars and nebulae making up the disk of the Milky Way does not interfere with the scene of the depths of intergalactic space. Instead, we peer parallel to the axis of the disk, its thinnest dimension. Distant galaxies, galactic clusters, and galactic superclusters jump into view because fewer Milky Way stars and nebulae obstruct the infinity beyond.
Discerning the direction of north is easily accomplished all year long by observing the direction of Polaris, the north star at the end of the handle of the Little Dipper in Ursa Minor. Unfortunately, despite Lucy’s contention in the Charlie Brown cartoon, there is currently no visible South Star.
The Big Dipper in Ursa Major is our timepiece. It reveals sidereal time which is time by the stars. When the two pointer stars (Merak and Dubhe) at the end of the cup are lined up due south of Polaris, sidereal time is 11:00, when they are lined up between Polaris and the north horizon, it is 23:00. To convert to local solar time, add ~2 hours for each month (4 minutes for each day) after the Spring Equinox or subtract ~2 hours for each month (4 minutes for each day) before the
The New Moon of April is on the 5th at 4:50AM EDT. It is the beginning of Lunation 1191 which ends 29.55 days later with the New Moon of May on the 4th at 6:46PM EDT.
The Full Moon on the 19th at 7:12AM EDT is the Paschal Full Moon which precedes and defines the date of Easter Sunday and its associated holidays. The April Moon is known as the “Grass, Egg, or Easter Moon”. Although Full Moon is only ~2.5 days after perigee, when Earth and Moon are closest, the Full Moon, although slightly larger than normal, does not qualify as a “supermoon,” like those of the first 3 months of 2019. Colonial Americans called the April Moon the “Planter’s Moon” and Celts called it the “Growing Moon”. It was named the “Seed Moon” in Medieval England. Chinese refer to it as the “Peony Moon” and the Anishinaabe (Odawa and Ojibwe) people recognize it as “Pokwaagami-giizis” (Broken Snowshoe Moon)
Lunar Perigee (minimum orbital distance) occurs on the 16th at 6:05PM EDT when the Moon is at a distance of 226,306 miles.
Planet..Constellation..Magnitude..Moon Passages ………………..Moon Phase..Moon Age
Sun……..Pisces……..-26.8…….4:50AM EDT, 4/5..New..0 days
Mercury..Aquarius….+0.9…….4.0°S, 7:00PM EST, 4/2 …Waning Crescent..27.33 days
Venus…..Aquarius….-3.9……3.0°S, Midnight EDT, 4/1 …Waxing Crescent..25.54 days
Mars……Taurus……..+1.5………5.0°S, 3:00AM EDT, 4/9…Waxing Crescent..3.92 days
Jupiter…Ophiuchus….-2.3….1.6°N, 6:00AM EDT, 4/23 ….Waning Gibbous..18.05 days
Saturn…Sagittarius….+0.5…0.4°S, 10:00AM EDT, 4/25 ..Waning Gibbous..20.22 days
Uranus….Pisces……+5.9……….5.0°S, 9:00AM EDT, 4/6 …Waxing Crescent..1.17 days
Neptune..Aquarius…..+8.0…..3.0°S, 7:00PM EDT, 4/2 …Waning Crescent..27.33 days Neptune..Aquarius..+184.108.40.206°S, 4:00PM EDT, 4/30.+7.9..Waning Crescent.24.97 days