This Week’s Sky at a Glance, 2022 June 18 – 25 ~by Curt Nason
Seasons are the result of the earth’s rotational axis being tilted about 23.5 degrees off the vertical, with respect to its orbit. The first day of astronomical summer is this Tuesday. The “astronomical” qualification is used because meteorologists have taken to confusing people with meteorological seasons based on temperatures. Meteorological summer in the northern hemisphere includes June, July and August because they have the highest average temperatures for the year.
On the summer solstice, the Sun rises and sets at its most northerly points on the horizon. For those of us at 45 degrees latitude, at midday (1:20 pm in Moncton) the Sun is about 68.5 degrees above the southern horizon; its highest altitude for the year. If we lived at latitude 23.5 degrees the Sun would be directly overhead at midday on the solstice. Several millennia ago the Sun was “in” the constellation Cancer on the solstice, hence that latitude is marked on maps as the Tropic of Cancer. The dim constellation does resemble a crab somewhat, but there is speculation that the Sun’s forth and back movement along the horizon at that time of year was reminiscent of a crab’s sideways walk.
The summer solstice point on the ecliptic, the Sun’s path through the constellations, has since passed through Gemini into Taurus. The roaming solstice is due to Earth’s axis wobbling like a top, making one revolution every 25,800 years in what we call the precession of the equinoxes. Enjoy your summer, whenever it starts.
This Week in the Solar System
Saturday’s sunrise in Moncton is at 5:27 am and sunset will occur at 9:13 pm, giving 15 hours, 46 minutes of daylight (5:35 am and 9:14 pm in Saint John). Next Saturday the Sun will rise at 5:29 am and set at 9:14 pm, giving 15 hours, 45 minutes of daylight (5:37 am and 9:16 pm in Saint John). At 6:14 am on Tuesday the Sun is at it farthest point north, our summer solstice.
The Moon joins the morning planetary line-up this week, visiting Saturn on Saturday, Jupiter on Tuesday when it is at third quarter phase, and Mars on Wednesday. For the few days at the end of the week it represents Earth in the line-up in order of distance from the Sun: Mercury, Venus, Earth-Moon, Mars, Jupiter and Saturn. Although Mercury is now moving toward the Sun it is also brightening, making it easier to detect with binoculars. By midweek Saturn will be rising before midnight.
On Sunday evening at 8 pm, tune in to the Sunday Night Astronomy Show via the Facebook page or YouTube channel of Astronomy by the Bay.
Questions? Contact Curt Nason.