August hosts a plethora of lunar and planetary events, perfect for the backyard astronomer. Even the most basic binoculars or telescope will allow you to enjoy our celestial neighbors as they put on quite the display this month.
August 1 starts off the month with a full supermoon, the second one this year. This event occurs when the moon appears slightly larger in the sky due to its proximity to us in its elliptical orbit. While there is no strict definition of a supermoon, it is commonly accepted that the moon be within 90% of perigee, its closest approach to us. By contrast, the farthest part of an elliptical orbit is called the apogee, and the moon’s distance can vary from about 405,500km to as close as 363,400km (about 252,000-225,000 miles). This full moon was also known in the Great-Lakes region as the Sturgeon Moon for its correlation with the preferred fishing season.
On August 10 Mercury will be at greatest Eastern elongation from the sun, meaning it is as high in the evening sky as we can see it, before it begins to move back around the sun. “Eastern elongation” may seem like a misnomer, referencing where the planets are in relation to each other, because to see it you will look to the western horizon just after sunset. This is the best day of the year to catch a glimpse of the elusive owl whom the Maya regarded as a messenger to the underworld.
In the early hours between August 12 and 13 the Earth will pass through the tail of comet Swift-Tuttle. Having last visited the inner solar system in 1992, and not returning till 2126, the debris cloud of dust and ice particles gives us the annual Perseid meteor shower, with excellent viewing this year because the moon will only be a crescent. Enjoy this show after midnight, when you may catch upward of 60 meteors per hour.
On August 24 the moon will eclipse the bright red head of Scorpius. This rare event will see the occultation of Antares, disappearing behind the moon at 6:55pm and reappearing an hour later, at 7:55.
Saturn puts on a show on August 27, at what we call opposition. Saturn will be closest to Earth on this night, and fully illuminated by the sun directly opposite. Moving through the constellation Aquarius in the southern sky, a medium-sized telescope will allow you to see the rings and maybe even its moon Titan.
Wrapping up the month, the evening of August 31 brings the month’s second supermoon. When two full moons occur in the same calendar month, we call the second one a blue moon. This moon won’t really appear blue, but it is relatively rare to have both full moons in a single month be supermoons.
If you would like to learn more about the sky, telescopes, or socialize with other amateur astronomers, visit us at prescottastronomyclub.org or Facebook @PrescottAstronomyClub to find the next star party, Star Talk, or event.
Adam England is the owner of Manzanita Financial and moonlights as an amateur astronomer, writer, and interplanetary conquest consultant. Follow his rants and exploits on Twitter @AZSalesman or at Facebook.com/insuredbyadam.