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The Night Sky of April

Dr. Wayne Wooten
Professor of Astronomy

For April 2018, the Moon will be Full Moon, the Paschal Moon following the Vernal Equinox, is on March 31, and sets the following Sunday, April 1st, as the date for Easter this year. On April 3rd, the Waning gibbous moon is four degrees north of Jupiter in the morning sky. The third quarter moon is April 7th, and lies two degrees north of Saturn and three degrees north of Mars. The new moon is on April 15th. The thin crescent moon lies five degrees south of brilliant Venus at dusk on April 17th; look for earthshine lighting up the rest of the lunar disk, a great photo op. The moon is first quarter on April 22nd, and will be well placed for smartphone photos.

Our photo this month of the waxing gibbous moon is typical of what you can expect to get with your phone and our scopes. The Moon is Full, the Strawberry Moon, on April 29th; the second full moon of April also makes this a "blue moon". As April ends, the moon passes four degrees north of bright Jupiter, both rising about an hour after sunset in the east.

Mercury is too close to the Sun for easy observing this month, but Venus dominates the early evening sky for the rest of this year. It climbs farther east of the Sun each evening. It passes south of the Pleiades star cluster on April 17th, with the crescent moon just south of Venus; great photo op about an hour after sunset! At month’s end, it sits between the cluster and the bright star Aldeberan in Taurus.

Mars is in the morning sky, and moves past Saturn in Sagittarius. It passes 1.3 degrees south of the ringed planet on April 2nd. It gets brighter, bigger, and closer to earth as we overtake it this summer, with the closest approach at opposition on July 27th. This will be our best views of the Red Planet since the famously close opposition of August 2003. After opposition, Mars will be in the evening sky for the rest of 2018, but we have already overtaken it and are pulling away from it, making it become smaller and fainter in our scopes for the rest of the year.

Jupiter reaches opposition on May 8th, so will be rising right after sunset in Libra this April. With a small telescope, its four largest Galilean moons are visible in a row around its equator. Your smartphone will be able capture these moons and some disk detail with our scopes.

Saturn rises in the SE about midnight as April begins, and reaching opposition on June 27th. The ringed wonder is at its best in the east in Sagittarius, with brighter red Mars to the lower left of it and the gibbous moon on April 7th, a nice photo op. When viewed with a telescope, the rings are open 27 degrees and double the planet’s disk brightness. Note the big moon Titan and several smaller moons fall on either side of the most beautiful telescopic sight in the sky.

Yellow Capella, a giant star the same temperature and color as our much smaller Sun, dominates the northwestern sky. It is part of the pentagon on stars making up Auriga, the Charioteer (think Ben Hur). Several nice binocular Messier open clusters are found in the winter milky way here. East of Auriga, the twins, Castor and Pollux highlight the Gemini. South of Gemini, Orion is the most familiar winter constellation, dominating the southern sky at dusk.

The reddish supergiant Betelguese marks his eastern shoulder, while blue-white supergiant Rigel stands opposite on his west knee. Just south of the belt, hanging like a sword downward, is M-42, the Great Nebula of Orion, an outstanding binocular and telescopic stellar nursery. The bright diamond of four stars that light it up are the trapezium cluster, one of the finest sights in a telescope. In the east are the hunter’s two faithful companions, Canis major and minor. Procyon is the bright star in the little dog, and rises minutes before Sirius, the brightest star in the sky. At 8 light years distance, Sirius is the closest star we can easily see with the naked eye from West Florida.

To the northeast, look for the Big Dipper rising, with the top two stars of the bowl, the pointers, giving you a line to find Polaris, the Pole Star. Look for Mizar-Alcor, a nice naked eye double star, in the bend of the big dipper’s handle. Take the pointers at the front of the dipper’s bowl south instead to the head of Leo, looking much like the profile of the famed Sphinx. The bright star at the Lion’s heart is Regulus, the "regal star".

Now take the curved handle of the Big Dipper, and follow the arc SE to bright orange Arcturus, the brightest star of the spring sky. Recent studies of its motion link it to the Sagittarius Dwarf Galaxy, a companion of our Milky Way being tidally disrupted and spilling its stars above and below the plane of the Milky Way, much like dust falling away from a decomposing comet nucleus. So this brightest star of Bootes the Bear Driver is apparently a refugee from another galaxy!

Now spike south to Spica, the blue-white gem in Virgo rising in the SE. Virgo is home to many galaxies, as we look away from the obscuring gas and dust in the plane of the Milky Way into deep space. To the southwest of Spica is the four sided Crow, Corvus. To the ancient Greeks, Spica was associated with Persephone, daughter of Ceres, goddess of the harvest. She was abducted by her suitor Pluto, carried down to Hades (going to Hell for a honeymoon!) and when Jupiter worked out a compromise between the newlyweds and the angry mother-in-law, the agreement dictated Persephone come back to the earth’s surface for six months of the year, and Mama Ceres was again placated, and the crops could grow again. As you see Spica rising in the SE, it is time to "plant your peas", and six months from now, when Spica again disappears in the sun’s glare in the SW, you need to "get your corn in the crib"….so was set our calendar of planting and harvesting in antiquity. In the arms of Virgo is a rich harvest of galaxies for modern astronomers.

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