Dr. Wayne Wooten: July Skies Of The Gulf Coast
For July 2021, the last quarter moon occurs on July 1. The new moon is on July 8, but no eclipse of the sun this month. Our next local partial solar eclipse is the new moon in October 2023. Venus is overtaking Mars in the western twilight, and the waxing crescent moon joins the show on July 11, with the thin crescent to the lower right of Venus, and faint Mars only a moon diameter to the left of Venus. The fatter crescent is above Venus on July 12, with Regulus in Leo just to the left of the Moon. Fine phase to capture earthshine on the moon’s dark upper side. The first quarter moon is July 17. The Full Moon, the Thunder or Hay Moon, is July 23. That same night, the moon is just to the right of Saturn two hours after sunset, and just below much brighter Jupiter on July 25. The moon is again last quarter on July 31; note this interval from one phase to its next recurrence is the moon’s synodic period, of 29.5 days.
Mercury is at the greatest western elongation in the dawn sky on July 4 but disappears into Sun’s glare by midmonth. Venus dominates the dusk and overtakes most, smaller, and much fainter Mars on July 12, passing only a half-degree (the diameter of the disks of the Sun and Moon to our naked eyes) on July 12, the same evening the waxing crescent moon lies to the upper right of the pair.
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. For a detailed map of the northern hemisphere, skies visit Skymaps and download the map for July.
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.
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, 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.
With the ending of Covid restrictions, we can again schedule public gazes at the Pensacola Beach Pavilion. With clear skies permitting, we plan to be south of the famed Beach Ball Water Tower on July 16-17, August 13-14 (Perseid Meteor Shower), September 10-11, and finally October 15-16.
We have set new dates for our public gazes at Big Lagoon State Park west of Pensacola for these Saturdays: July 31, August 28, and September 25. Be sure to check-in at the gate before sunset. We are also checking if changes in the National Park Service administration will make us again welcome at Fort Pickens, where we held sky interpretation sessions from 1976-2019.
For more information on the Escambia Amateur Astronomers, visit our website, join us on Facebook or call our sponsor, Lauren Rogers at Pensacola State College at (850) 484-1155, or e-mail her at the college at email@example.com. All EAAA events are free and open to the public.