For April 2021, the last quarter moon is on April 4. The waning crescent passes below Saturn in the dawn on April 6, then below brighter Jupiter on April 7. It is new on April 11. The waxing crescent passes below Mars in the evening sky on April 15. First quarter moon is April 19, and the full moon, the Egg Moon, is on April 26.
Mercury is visible just below the Pleiades cluster in the northwest at the very end of the month in the evening sky. You will start to see much brighter Venus emerge into the evening sky in early May. Mars is the only easy planet to spot in the evening sky, moving well up in the NW from the horns of Taurus into the feet of Gemini. Both Jupiter and Saturn are well placed for morning viewing in Capricornus.
Visit skymaps.com for a more extensive calendar, and list of best objects for the naked eyes, binoculars, and scopes on the back of the map.
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. 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 Betelgeuse 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 eight 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. It is just north of the end of the handle of the Big Dipper that we find our featured object for April, the Pinwheel Galaxy. Under dark skies, binoculars will reveal it in an equilateral triangle with Mizar and Alkaid, the end star of the handle. Now is the best time of year for us in the northern hemisphere to see such external galaxies, since the dust, gas, and stars of our own Milky Way are largely out of view now. All around the horizon, the winter Milky Way is setting in the west, and the brighter summer arms are still to rise in the south east. To the south, the bright Centaurus-Crux arm lies just below our southern horizon. So, we now look straight overhead into the depths of intergalactic space, with little dust obscuring our visible light views. The Pinwheel lies about 20 million light years distant, and is about twice the size and mass of our own Galaxy. Our solar system would be located about two-thirds the way out in the spiral arms of this great spiral for comparison. And there are literally millions of solar type stars very similar to our Sun in this galaxy as well. Is anyone listening?
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 southeast 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.
Out at the edge of our Galaxy are hundreds of globular star clusters, and one of the finest lies just east of Arcturus. It is the third entry in Messier’s listing of smudges in the sky that did not move and thus were not his beloved comets. M-3 is visible as a compact blur in binoculars, and resolves itself into thousands of stars at about 100X in scopes six inches or larger. Many more globulars will join it in the eastern sky in the next few hours, with over 100 in range of amateur scopes.
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 southeast, it is time to “plant your peas”, and six months from now, when Spica again disappears in the sun’s glare in the southwest, you need to “get your corn in the crib” — so was set our calendar of planting and harvesting in antiquity.
For more information on the Escambia Amateur Astronomers, join us on Facebook at visit our website at eaaa.net or call our sponsor, Lauren Rogers at Pensacola State at (850) 484-1155 or lrogers@pensacolastate.edu.