For July 2020, the Full Moon (the Hay or Thunder Moon) occurs on July 5. It will be just to the lower left of bright Jupiter, making a fine triangle with fainter Saturn to the east (left) of Jupiter as all three rise in the sunset sky. The last quarter moon is to the lower left of brightening Mars in the dawn on July 11. The waning crescent moon is just below the Pleiades cluster on the morning of July 16, and just left of brilliant Venus on July 17. Note Venus is close to Aldebaran and the head of Taurus, making this a fine photo op. The thin crescent Old Moon is just left of Mercury in the dawn on July 19; binoculars will help spot them with a clear northeast horizon. The new moon is July 20. The first quarter moon is July 27, and as the month ends, the waxing gibbous moon is again below Jupiter on August 1, and to the left of Saturn on August 2.
Mercury is too close to the sun for convenient observing in July, but Venus returns to the dawn sky. She passed between us and the Sun in June, and climbs higher and brighter in the dawn in July. The striking crescent is best seen just at sunrise, against a brighter blue-sky background.
Mars comes to a historically close and bright opposition this fall, so as our faster moving Earth overtakes the red planet, it gets brighter in the dawn sky all month. By the end of the month, moderate sized scopes should reveal a tiny summer south polar cap, with the disk now 86% sunlit, 14” of arc across, and shining at an impressive red -1 magnitude. It will be more than six times brighter at opposition in three months!
The highlights of July skies are the two giants at opposition. Jupiter rises at sunset on July 13, and Saturn follows on July 20. With smaller scopes, note the four Galilean moons in a row around its equator, shifting positions hour by hour. The Great Red Spot is within range of 3” scopes, and a lot of detail in its belts and zones emerges with even bigger scopes. Also note Jupiter spins so fast, in less than 10 hours, that its equator bulges 10% wider than its polar diameter. It will happen to you, too, young’uns.
While the naked eye, dark adapted by several minutes away from any bright lights, is a wonderful instrument to stare up into deep space, far beyond our own Milky Way, binoculars are better for spotting specific deep sky objects. Visit Skymaps and download the map for July 2020; it will have a more extensive calendar.
If you drop south from the bowl of the Big Dipper, Leo the Lion is in the southwest. Note the Egyptian Sphinx is based on the shape of this Lion in the sky. Taking the arc in the Dipper’s handle, we “arc” southeast to bright orange Arcturus, the brightest star of Spring. Cooler than our yellow sun, and much poorer in heavy elements, some believe its strange motion reveals it to be an invading star from another smaller galaxy.
This is the Sagittarius Dwarf Galaxy, now colliding with the Milky Way in Sagittarius in the summer sky. It lies on the far edge of our own barrel spiral, and may account for the formation of our bar. Moving almost perpendicular to the plane of our Milky Way, Arcturus was the first star in the sky where its proper motion across the historic sky was noted, by Edmund Halley.
Spike south to Spica, the hot blue star in Virgo, then curve to Corvus the Crow, a four sided grouping. North of Corvus, in the arms of Virgo, is where our large scopes will show members of the Virgo Supercluster, a swarm of over a thousand galaxies about 50 million light years distant.
To the east, Hercules is well up, with the nice globular cluster M-13 marked on your sky map and visible in binocs. The brightest star of the northern hemisphere, Vega (from Carl Sagan’s novel and movie, “Contact”), rises in the northeast as twilight deepens. Twice as hot as our Sun, it appears blue-white, like most bright stars. At the opposite end of the parallelogram of Lyra is M-57, the Ring Nebula.
Northeast of Lyra is Cygnus, the Swan, flying down the Milky Way. Its bright star Deneb, at the top of the “northern cross” is one of the luminaries of the Galaxy, about 50,000 times more luminous than our Sun and around 3,000 light years distant. Under dark skies, note the “Great Rift”, a dark nebula in front of our solar system as we revolve around the core of the Milky Way in the Galactic Year of 250 million of our own years.
To the east, Altair is the third bright star of the summer triangle. It lies in Aquila the Eagle, and is much closer than Deneb; it lies within about 13 light years of our Sun. Use your binocs to pick up many clusters in this rich region of our own Cygnus spiral arm rising now in the east.
To the south, Antares is well up at sunset in Scorpius. It appears reddish (its Greek name means rival of Ares or Mars to the Latins) because it is half as hot as our yellow Sun; it is bright because it is a bloated red supergiant, big enough to swallow up our solar system all the way out to Saturn’s orbit! Scorpius is the brightest constellation in the sky, with 13 stars brighter than the pole star Polaris. Note the fine naked eye clusters M-6 and M-7, just to the left of the Scorpion’s tail. Beautiful Saturn now sits well north of the stinger on the scorpion’s tail.
Just a little east of the Scorpion’s tail is the teapot shape of Sagittarius, which lies toward the center of the Milky Way. From a dark sky site, you can pick out the fine stellar nursery, M-8, the Lagoon Nebula, like a cloud of steam coming out of the teapot’s spout. Jupiter and Saturn both lie east of the teapot, on the border with Capricornus.
For more information on the Escambia Amateur Astronomers, visit our website at eaaa.net, join us on Facebook or contact Lauren Rogers at Pensacola State College at 484-1155, or e-mail lrogers@pensacolastate.edu.