This Week’s Sky at a Glance, 2023 August 26 – September 2

This Week’s Sky at a Glance, 2023 August 26 – September 2

This Week’s Sky at a Glance, 2023 August 26 – September 2

You will probably hear or read of a Super Blue Moon this week when it reaches the full phase on Wednesday evening, less than ten hours after it is closest to Earth in 2023 (357,181 km). Technically, this is referred to as a perigean full Moon; the Moon is at perigee when it is closest for the month. A decade ago the media began calling this a Super Moon, and it seems the definition has expanded to include any full Moon occurring within 90% of its perigee for that orbit. That makes for three or four a year and, like the overabundance of superheroes in Hollywood, the term loses its lustre, so to speak.

Wednesday’s full Moon will be 14% wider (and hence 30% brighter in theory) than the one in February when the Moon was near apogee, its farthest for the month; which I call the Puny Moon to match the silliness of it all. The size difference is about the same as a quarter and a nickel, which when held at arm’s length (if your arms are two metres long) will give approximately the same relative size of the Moon in the sky.

Since full Moons occur every 29 and-a-half days, there was also a full Moon on August 2, and this is where the Blue Moon comes in. For the past half-century the second of two full Moons in a calendar month has been awarded that term. In older times, when the Moon was a calendar for many societies, the full phase was given names related to what was occurring in nature at that time of year. Every few years we get 13 full Moons (do the math) and therefore four in one season. To preserve the meaning of the full Moon names, a version of the Farmer’s Almanac called the third of four in a season a Blue Moon. This was misinterpreted as the second in a calendar month, and now some media outlets are using both definitions. A real blue Moon can occur following natural events that blow thick dust high into the atmosphere, as happened following the volcanic eruption in Krakatoa in 1883 and western forest fires seven decades ago. The dust absorbed the long wavelength red and orange parts of sunlight and passed relatively more blue light reflecting from the Moon.

This Week in the Solar System

Saturday’s sunrise in Moncton is at 6:32 am and sunset will occur at 8:09 pm, giving 13 hours, 37 minutes of daylight (6:38 am and 8:12 pm in Saint John). Next Saturday the Sun will rise at 6:40 am and set at 7:56 pm, giving 13 hours, 16 minutes of daylight (6:46 am and 8:00 pm in Saint John).

The Moon is full, at perigee and rising near Saturn on Wednesday (Ringo and Keith Moon drumming up interest.) Look for extreme tides late in the week. Saturn is at opposition on Sunday, rising around sunset and spending autumn in the evening sky for telescope users. Its rings are open slightly, enough to see space between them and the planet, and they will open a little more from our perspective over the next few months. Jupiter rises two and a half hours after sunset so its best viewing will occur in the early morning. Mercury and Mars are too close to the setting Sun for viewing. Venus, the brightest planet, rises around 5:20 this weekend, 20 minutes after Sirius, the brightest star. The winter constellations in the morning sky remind us to enjoy what is left of summer.

The Saint John Astronomy Club meets at the Rockwood Park Interpretation Centre on September 2 at 7 pm. All are welcome.

Weekly Sky at a Glance ~by Curt Nason

 

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