The Perseids Peak During a Major Moon, and Venus at Dawn, while Saturn shines at Night!
The Perseid Meteor Shower Peaks!
The prolific Perseid Meteor Shower peaks during the daytime on Saturday morning, August 12th, so we can expect to receive plenty of meteors both Friday night and Saturday night. Within a couple of nights before and after the peak date, the quantity will be reduced somewhat, but still worth looking for. The Moon will be waning gibbous (i.e., about 70% illuminated) on the peak nights, and sitting in the sky after midnight — spoiling this year’s show. (Next year the moon will be new, setting up a fantastic show.)
Meteor showers are annual events that occur when the Earth’s orbit passes through zones of debris left by multiple passes of periodic comets. (It’s analogous to the material tossed out of a dump truck as it rattles along. The roadway gets pretty dirty if the truck drives the route a number of times!) Over centuries, or longer, the dust-sized and sand-sized (or larger) particles accumulate and spread out a bit. When the Earth encounters them, they are caught by our gravity and burn up as they fall through our atmosphere at speeds on the order of 200,000 km/hr. The duration of a meteor shower depends on the width of the zone, and the intensity depends on whether we pass through the densest portion, or merely skirt the edges.
The nickname for meteors is “shooting stars” or “falling stars”, but they bear no physical connection to the distant stars, and all your favourite constellations will look the same as ever at the end of the shower!
The source of the Perseids material is thought to be a 130 year period comet named Comet 109P/Swift-Tuttle. The active period this year’s shower is July 13th through August 26th, so keep an eye out for them beyond this week. This shower is known for producing 60–80 meteors per hour at the peak — many manifesting as bright, sputtering fireballs!
While visible anywhere in the night sky, they appear to radiate from a point in the sky between the constellations of Camelopardalis (the Giraffe) and Perseus (the Hero), which are low in the NE sky in evenings — and nearly overhead by dawn. Meteor showers are best observed in the dark skies before dawn, because that’s the time when the sky overhead is plowing directly into the oncoming debris field.
Try to find a dark viewing location with as much open sky as possible. You can start watching as soon as it’s dark. Don’t worry about watching the radiant. Bring a blanket and a chaise to avoid neck strain. And remember that binoculars and telescopes will not help. Their field of view is too narrow. Good hunting!
Sun, Moon, and Planets
The August full moon occurs Monday afternoon. Known as the “Corn Moon”, “Sturgeon Moon”, “Red Moon”, “Green Corn Moon”, and “Grain Moon”, it always shines in or near the stars of Aquarius (the Water-bearer) and Capricornus (the Sea-goat), constellations far too dim to see next to the bright orb. Full moon phases occur when the moon is precisely opposite the sun in the sky, and since the sun visits the same constellations on the same date every year, an object opposite the sun will do the same thing. The number of days it takes the moon to orbit the earth and return to the same phase doesn’t divide evenly into a year, so the date for every month’s full moon varies from year to year.
Due to its 5° tilted orbital plane, the moon usually sits above or below the direct line between the sun and the earth. While the earth completes a single orbit of the sun each year, that line traces a large circle around the sky called the ecliptic. (The sun appears to journey along that line, visiting the zodiac constellations one-by-one, but it’s actually simply a perspective change due to the earth moving.) This full moon will occur near enough to the ecliptic to generate a partial lunar eclipse visible in Eastern Europe, most of Africa and Asia, and Australia. In a lunar eclipse, the moon crosses through the round dark shadow cast by the earth in the night sky. In two weeks, the same alignment will cause the new moon to occur on the ecliptic — producing the total solar eclipse on August 21.
Through the rest of this week, the moon will wane and rise later, lingering longer and longer into the morning daytime sky. By next Sunday, the moon will be almost to Last Quarter, when it rises just before midnight among the stars of Pisces (the Fishes).
Mercury continues to drop lower in the western evening sky while shifting westward towards the Sun this week. It sets about 9 pm local time. Jupiter is the extremely bright object low in the southwestern evening sky. It sets at 11 pm local time — about two hours behind Mercury. The Great Red Spot is visible on Jupiter for about three hours centred on Thursday, August 10 at 9:40 pm EDT (in dark twilight).
Saturn is the medium-bright, yellowish object partway up the southern sky after the evening sky darkens. It sets in the west about 2 am local time. Once it’s fully dark, look for the easy to recognize star pattern called the Teapot sitting about 20° (two fist diameters) to the lower left of Saturn. The Teapot is an asterism — a simple pattern of stars that look like an object. It’s shape is an old-fashioned teapot tipped slightly towards the west, with the handle on the east (left), a pointed lid, and large spout. This one is made from part of the larger constellation Sagittarius (the Archer). The Milky Way rises up from the southern horizon like steam from the teapot’s spout. The stars of Scorpius (the Scorpion) flank Saturn on the lower right.
The icy giant planets Uranus and Neptune are well-placed for viewing between midnight and dawn. Uranus, in Pisces (the Fishes) rises about 11:30 pm local time and is visible with binoculars under a dark sky. Neptune, which rises about 9:45 pm local time this week, is in the southeastern sky about two finger widths to the lower left of the medium-bright star Hydor in Aquarius (the Water-Bearer).
Extremely bright Venus rises in the eastern sky about 3:15 am local time and can be seen easily until dawn. This week, the planet continues to descend slowly sunwards, passing through the legs of Gemini (the Twins). Viewed in a telescope, the planet presents a more than half illuminated phase.
Stargazing News for this week (from August 6th) by Chris Vaughan.