Huestis: Astronomical Potpourri in July
Sunday, July 02, 2017
These cloudy/rainy conditions certainly put a dampener on the public open nights at the local observatories. Each year when this happens I often say it can’t get any worse. Then it does!
But once in a while we do get a good clear night. The night of May 16 was perfect. After so many weeks of less than ideal sky conditions forcing closures, Ladd Observatory in Providence opened its dome for public viewing. We were deluged (pun intended) with visitors. They were all treated to fantastic views of Jupiter and his four Galilean moons (until Ganymede disappeared behind the disk of the planet). Ladd Observatory Manager Bob Horton and I estimated 150 folks enjoyed the gorgeous view provided by the 12-inch Brashear refractor telescope that night.
Jupiter will continue to be favorably placed for observation during July. On the first it will form a nice triangle with Virgo’s bright star Spica and a waxing gibbous Moon. By month’s end Jupiter will set just before 11:00pm, so come out to any of the local observatories to take a look at this beautiful planet before it gets too low in the sky to be easily observed.
However, as July begins everyone will be treated to views of the magnificent ringed-planet Saturn. I’m sure Saturn will soon replace Jupiter as the main focus of our open nights. As long as the skies are cloud-free we will be observing Saturn and his absolutely beautiful rings throughout the summer and into mid fall. If the local observatories should encounter cloudy skies for several consecutive weeks, once they reopen be sure to arrive early. For when Saturn is in view crowds descend upon the public open nights.
Currently Saturn’s rings are tilted almost to their maximum angle possible— about 27 degrees— providing a remarkable three-dimensional view of them and the disk of the planet. In astronomer Garrett P. Serviss’ 1901 book, Other Worlds, he wrote, “Many telescopic views in the heavens disappoint the beginner, but that of Saturn does not. Even though the planet may not look as large as he expects to see it from what he has been told of the magnifying power employed, the untrained observer is sure to be greatly impressed by the wonderful rings, suspended around it … No previous inspection of pictures of these rings can rob them of their effect upon the eye and the mind. They are overwhelming in their inimitable singularity, and leave every spectator truly amazed.” I couldn’t agree more.
Contrary to popular belief, the Earth is not at its closest distance to the Sun in July. Our planet is actually at aphelion (farthest from the Sun) on July 3 at about 94,505,901 miles at 4:11pm EDT. It just so happens that the tilt of the Earth’s polar axis has the northern hemisphere tipped toward the Sun at that time, providing more direct sunlight for us. At perihelion (Earth closest to the Sun) back on January 4, the Earth-Sun distance was 91,404,322 miles. The difference, just over three million miles (or 7 percent), has little effect on our planet. However, northern hemisphere summer is warmer than its southern hemisphere counterpart because of the fact that there is much more land mass north of the Earth’s equator to absorb the solar radiation.
Our solar system’s innermost planet Mercury can also be glimpsed this month, providing you have an unobstructed view of the western horizon after sunset. Mercury will be less than ten degrees above that horizon at its highest. Increase your chances of seeing it by looking on July 25 soon after sunset. Mercury will be about seven degrees to the lower right of a waxing crescent Moon, and just one degree (equivalent to two full moon diameters) to the lower left of Regulus, Leo’s brightest star.
And finally, the Moon will not affect observation of two late month meteor showers. These overlapping shooting star displays are best observed from the southern hemisphere, but approximately 15-20 Delta Aquarids and Alpha Capricornids can be seen between midnight and dawn from July 28-30 locally. Face south and scan from the horizon to zenith and left to right. Both showers display fairly bright yellow meteors, while the Alpha Capricornids are noted for producing brilliant fireballs. However, you might see more fireflies than meteors, depending upon sky conditions. That scenario can make it all worthwhile.
Though it doesn’t get sufficiently dark to observe the heavens until after 9:15pm or so during July, all of the local observatories will remain open during the summer months. Seagrave Memorial Observatory in North Scituate is open every clear Saturday night. Ladd Observatory in Providence is open every clear Tuesday night. The Margaret M. Jacoby Observatory at the CCRI Knight Campus in Warwick is open every clear Wednesday night. Frosty Drew Observatory in Charlestown is open every clear Friday night. Check the respective websites for open times.
As always, keep your eyes to the skies.
Great American Total Solar Eclipse on August 21, 2017. Countdown: 51 days as of July 1, 2017.
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