This Week’s Sky at a Glance, August 11 – 18 ~by Curt Nason
The main event in the sky this week is the Perseid meteor shower. On any clear night this weekend you will have a better chance of seeing meteors, especially in the wee hours before morning twilight. The peak time is predicted to occur around 10 pm on Sunday when, unfortunately, the constellation Perseus is still low on the northeast. You can see a few meteors per hour any night in a clear, dark sky, but the number increases greatly when Earth passes through a trail of pebbles and dust left by a comet that makes frequent orbits around the Sun. The pebbles left by comet Temple-Tuttle in its 133 year orbit are quite large at a few centimetres, and they enter our atmosphere at a high relative velocity of 60 km/s (Earth travels at 30 km/s). Therefore, they can be very bright.
Meteors, also called shooting stars or falling stars, are the streaks of light created when particles enter the atmosphere at an altitude of about 100 kilometres, and those particles from comets disintegrate before they reach an altitude of 50 kilometres. Many meteors are faint and easily made invisible by moonlight and light pollution. This year the Perseid shower occurs near the new Moon phase so we can expect to see more than usual. They will seem to be coming from a point within the constellation Perseus, which is at its highest in the sky in early morning. You will see fewer in the evening but they tend to be long and bright.
Although a dark sky is preferred for watching meteors, many can still be enjoyed from an urban or suburban area. Get comfortable in a chair, have extra clothes or blankets if you plan to stay long as it can get very chilly, and select a patch of sky that is free of clouds and light. It is better to keep Perseus to your side rather than look in that direction because the meteors will look more spectacular, covering a longer distance. Be very happy if you see about 20-30 per hour on the peak night, or fewer a day before or after. Anything more is a bonus, and this could be a bonus year.
This Week in the Solar System
Saturday’s sunrise in Moncton is at 6:13 am and sunset will occur at 8:34 pm, giving 14 hours, 21 minutes of daylight (6:20 am and 8:37 pm in Saint John). Next Saturday the Sun will rise at 6:22 am and set at 8:22 pm, giving 14 hours of daylight (6:28 am and 8:26 pm in Saint John).
The Moon is new on Saturday, August 11 and it is at first quarter the following Saturday. Venus has a twilight photo opportunity with a slim Moon on Tuesday, and it is at its greatest elongation from the Sun on Friday. Saturn is at its best in the early evening. On Thursday, telescope users might see the shadows of Jovian moons Io and Europa moving across the atmosphere of Jupiter, starting around 9:08 pm and lasting for more than two hours. Mars is in good position for observing by late evening and its global dust storm is weakening. The Perseid meteor shower peaks in a moonless sky Sunday evening and should be active enough to keep most stargazers happy over the weekend and Monday.
The RASC NB star party at Mactaquac Provincial Park takes place this weekend, August 10-11.
Questions? Contact Curt Nason.