July Meteor Showers + More Astronomical Events
Monday, July 16, 2012
While it may appear counter-intuitive to northern hemisphere residents, the Earth was at aphelion (farthest from the Sun) on July 4 at about 94,510,232 miles. 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 91,406,283 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 there is much more land mass north of the Earth’s equator to absorb the solar radiation.
Planets to look for
High in the southwestern sky after sunset you can still see Mars and Saturn. At the beginning of the month they were about 23.5 degrees apart. By month’s end they will have narrowed that distance to only eight degrees. If you have a telescope Saturn will still display a great image. However, Mars will be quite small and show little or no detail, since it will be so far away (140,631,634 miles on July 14 and still increasing).
The morning sky will have its share of beautiful scenes to view as well. Jupiter and Venus will be brilliant beacons in morning twilight. Both can be found in the constellation of Taurus.
And finally, there are two meteor showers at the end of July. These shooting star displays are spread out over a couple of days and therefore overlap. Though a waxing gibbous Moon will pose some interfering moonlight before midnight, once it sets you’ll have several hours of dark sky to observe a few meteors blaze across the sky.
The first meteor shower, the Delta Aquarids, peak from July 28-30, with the morning of the 29th being the best time to observe. Once the Moon sets around 1:46am EDT, an observer well away from light polluted skies can expect to see about 20 bright, yellow meteors per hour. Because these meteors nearly broadside the Earth, their speed is a moderate 25.5 miles per second.
The second meteor shower you should observe comes a day later on the morning of July 30 with the peak of the Capricornid meteor shower. The Capricornids are also yellow meteors and are noted for producing brilliant fireballs. They are slow interplanetary interlopers, hitting our atmosphere at around 15 miles per second. You can expect only 15 meteors per hour once the bright Moon sets around 2:48am EDT on the morning of the 30th.
Aquarius and Capricornus, the constellations from which these shooting stars appear to emanate from, will be just less than halfway between the southern horizon and zenith (straight up) around 2:00 am. And don’t forget — wait until the bright waxing gibbous Moon sets so you can maximize your viewing pleasure.
Though it doesn’t get sufficiently dark to observe until after 9:15pm or so during July, several fine observatories remain open during the summer months for observing the heavens. Aldrich Astronomical Society will be holding its annual StarFest on July 28 from 6 to 10 pm at Anna Maria College. Seagrave Memorial Observatory in North Scituate is open every clear Saturday night for observing. And if you wish to observe from perhaps the darkest skies in Rhode Island, grab your passport, pack an overnight bag, and make the trip down to Charlestown and visit Frosty Drew Observatory on any clear Friday night. Please visit the respective websites for details.
If you know of an institution within 25 miles of Worcester that offers public telescopic observing opportunities or has a great astronomy program to promote, please contact me via email at: [email protected], David A. Huestis, GoLocalWorcester Contributor.
As always, keep your eyes to the skies.