Sky at a Glance August 10 – 17

Photo showing location of the constellation Perseus in the northeastern night sky.

This Week’s Sky at a Glance, 2019 August 10– 17 ~by Curt Nason

With the Perseid meteor shower peaking this week, let us visit its namesake constellation. Perseus the Hero stands on the northeastern horizon by midnight, just below the W shape of his mother-in-law, Cassiopeia. He is a hero because, among other deeds, he prevented his future wife Andromeda from becoming a tasty lunch for a ferocious sea monster.

The brightest star in Perseus, Mirfak, is part and namesake of the Alpha Persei Cluster. This is one of my favourite binocular targets because it resembles a miniature version of the constellation Draco. Another popular binocular target is a close pair of star clusters – NGC 869 and 884 – located halfway between Perseus and Cassiopeia, which astronomers have cleverly called the Double Cluster. The Perseid meteors appear to originate from a point near the Double Cluster.

The constellation’s second brightest star is Algol the Demon, representing the eye of the Gorgon Medusa. Perseus beheaded the Medusa in a plan to avenge an embarrassing moment by using her head to turn his hecklers into stone. The sea monster was his first victim of this weapon. Algol is famous for dimming by a factor of three every 69 hours. It is a very close pair of stars orbiting each other in our line of sight, and their combined brightness drops when the dimmer star passes in front of the brighter one. Look for the star cluster M34 about a binocular width above Algol.

This Week in the Solar System

Saturday’s sunrise in Moncton is at 6:12 am and sunset will occur at 8:36 pm, giving 14 hours, 24 minutes of daylight (6:19 am and 8:39 pm in Saint John). Next Saturday the Sun will rise at 6:20 am and set at 8:25 pm, giving 14 hours, 5 minutes of daylight (6:27 am and 8:28 pm in Saint John).

The Moon is full on Thursday, the Mi’gmaw Ripening Moon, and passes near Saturn on Monday. Jupiter is stationary on Sunday, after which it begins its normal eastward motion relative to the stars. Telescope users might see its Red Spot around 11:30 pm on Sunday and 11 pm on Friday. Saturn is highest in the south and at its best for observing around 11 pm. Mercury will slowly start moving sunward but it also brightens in doing so, making this week a good time to look for it with binoculars 45 minutes before sunrise. Venus reaches superior conjunction behind the Sun on Wednesday and will move into the evening sky in autumn. The highlight of the week is the annual Perseid meteor shower, which peaks over Monday evening into Tuesday morning. Moonlight will obscure the fainter meteors but this shower is noted for having more than its share of bright shooting stars. The nights immediately before and after will typically produce half the number seen on the peak night.

There will be public observing in Cambridge Narrows on Saturday evening as part of the Life at the Lakes Festival, and at Oak Bay on Friday, August 16.

Questions? Contact Curt Nason.

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