This Week’s Sky at a Glance, 2021 June 19 – 26 ~by Curt Nason
Five millennia ago, Persian and perhaps Egyptian astrologers designated four of the first magnitude stars (the 20 brightest) as Watchers of the Sky, with each guarding one of the four cardinal directions. With their proximity to the Sun at the equinoxes and solstices they were also used to mark seasonal changes. Collectively, they were known as the Royal Stars.
Regulus in Leo and Antares in Scorpius were two of the Royal Stars, and we see them now appearing through evening twilight. Regulus guarded the north and marked the summer solstice, while Antares guarded the west and marked the beginning of autumn. Fomalhaut, in Piscis Austrinus below Aquarius, guarded the south and marked the winter solstice. Aldebaran, currently rising in Taurus an hour before sunrise, guarded the east and marked the spring equinox. These stars no longer mark the seasons as they did 5000 years ago due to precession of Earth’s polar axis, which makes one complete wobble every 25,800 years. On the summer solstice, the Sun is now located near the border of Gemini and Taurus.
None of the Royal Stars make the top ten in brightness. The brightest star in the sky for this time of year, Arcturus, is at its highest at sunset. It precedes almost equally bright Vega, which anchors the Summer Triangle with Deneb and Altair. Vega reaches its highest point about half an hour before Fomalhaut rises around 2:30 am. These two stars are the same distance from us, at 25 light years.
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 (5:36 am and 9:15 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 (5:38 am and 9:16 pm in Saint John). The Sun reaches its farthest position north on Monday at 12:32 am, the summer solstice for the northern hemisphere.
The Moon is full on Thursday evening, rising nearly southeast and setting less than eight and a half hours later; a short night for stargazers and werewolves. Mercury is stationary on Tuesday and will be at its best for morning observing during the second week of July. Venus blazes through evening twilight in the northwest, and Mars makes a pretty binocular sight in the middle of M44, the Beehive star cluster, on Wednesday evening. Jupiter is stationary on Monday, beginning four months of westward retrograde motion against the stars. Saturn rises before midnight and it is well placed for displaying its beautiful rings in morning twilight.
With astronomy meetings and outreach activities on hold, you can watch the local Sunday Night Astronomy Show at 8 pm and view archived shows.
Questions? Contact Curt Nason.