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The Night Sky of July

Dr. Wayne Wooten
Professor of Astronomy

For July 2024, the waning crescent moon passes north of Mars in the morning sky on July 1st, then above Jupiter on July 3rd. New moon is July 5th, the same day we are at aphelion, farthest from the Sun at 94.5 million miles. As your thermometer reminds us, our almost circular orbit plays a much lesser role in our seasons than does our axial tilt. The slender waxing crescent passes just above Mercury in twilight on July 7th, a fine photo op and great chance to catch the innermost planet with the naked eyes. The first quarter moon is on July 13th. The full moon, the Thunder Moon, is on July 21st. The waning gibbous moon rises just below Saturn about 10 p.m. on July 24th. The last quarter moon is on July 27th. The waning crescent passes Mars in the dawn on July 30th, and much brighter Jupiter on July 31st.

Mercury is visible low in the western twilight for the first two weeks of July, but never gets very high for us. But in the southern hemisphere, this will be their best chance to observe it in 2024. Venus is still too close to the Sun to spot yet. Mars is in the morning sky in Taurus, south of the famed Pleiades cluster. Jupiter is now back in the dawn, north of the Hyades cluster in Taurus. This is a great photo op

Saturn rises about 10 p.m. in Capricornus, it looks a lot different than last year. The rings are thinning fast, and will be edge on and disappear for earth-based observers next March, so enjoy them this Fall as they get thinner and more edge on daily. Like earth, Saturn has seasons, and even more tilt (27 degrees versus our 23.5 degrees). At its solstices, the rings are bright and widely open for us, but in the next year, Saturn’s almost edge on rings drop its apparent brightness in the sky by half as it approaches its equinox. The icy rings reflect much more light than the darker disk of the planet.

High overhead is the Big Dipper, and good scouts know to use the pointers at the end of the bowl to find Polaris, the pole star, staying 30 degrees high in our night sky all year long. By midnight, the earth’s rotation will carry the dipper low in the NW sky, yet Polaris will still be in the same place. This was critical to early navigators like Columbus, for if they kept Polaris at the same altitude in their northern sky, they knew they were sailing due west, leading him to the new world.

If you drop south from the bowl of the Big Dipper, Leo the Lion is in the SW. 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" SE 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 barred 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.

Arcturus is currently the brightest star overhead, but that can change any day now. To the NE of Arcturus is the Northern Crown, Corona Borealis. Its brightest jewel is Gemma (or Alphecca, here), in the center of the crown, but below the eastern edge of the curve near epsilon Corona Borealis, the dwarf nova T Corona Borealis is due to flare 100X brighter any time. Here is the finder chart to see if it has flared yet. At its maximum light, it should outshine Gemma for at least a few days, based on previous explosions seen in 1217, 1787, and 1866. Stay tuned!

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 NE as twilight deepens. Twice as hot as our Sun, it appears blue-white, like most bright stars.

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. of the Galaxy, and a little above (north) of Vega.

South of Deneb, on a dark clear night, 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. The star at the south end of the Northern Cross is one of my favorites, Albireo, the "gator star", a notable orange and blue double at 20X.

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.

As we head 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.

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. This view of our home galaxy stretching overhead is for about midnight on July evenings, looking from the South to overhead. My favorite way of learning the many deep sky objects (open and globular clusters, bright nebulae like the Lagoon, and the many dark nebulae that make up the "Dark Constellations" of the Inca) is to use low power binoculars (I prefer 8x40s because they are light and easier to hold steady with my Parkinson’s, but younger folks with a better grip on life will find 10x50’s will show fainter objects and at high power) and lean back in a lawn chair (also an ideal way to observe meteor showers like August’s Perseids with just your naked eyes) and slowly sweep up and down the Galaxy, marking off the deep sky objects on your SkyMap as you spot them.

Note the back of the SkyMap has a fine selection of the best deep sky objects to spot with the naked eyes, binocs, and small scopes to help you find your way across the Galaxy this summer. Of course, you will need dark skies to see this kind of beauty, but many have plans for trips to parks and out west this summer, so be sure to plan for at least a few evenings under dark skies to appreciate our galaxy. Also, most new smartphones can get fine shots with timed exposures on a tripod like this one, using night camera or Starry Camera Pro programs. Try out yours dark evening.

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