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This Week’s Sky at a Glance, 2021 June 19 – June 26

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, on YouTube at:  https://www.youtube.com/channel/UCAEHfOWyL-kNH7dBVHK8spg

Questions? Contact Curt Nason at nasonc@nbnet.nb.ca.

 

 

This Week’s Sky at a Glance, 2021 June 12 – June 19

If you note the times of sunrise and sunset over the month you might be surprised to discover the earliest sunrise and latest sunset do not occur on the solstice. Although the most amount of daylight occurs then, we get our earliest sunrise around June 16 and latest sunset around June 26. Earth’s tilt plays a role in that, as does the fact that its orbit is not circular. We are about five million kilometres closer to the Sun in early January than we are in early July. Four centuries ago Johann Kepler showed that planets travel faster when they are nearer the Sun. Have you noticed that the time between the beginning of spring and fall is a week longer than between fall and spring?

We expect the Sun to reach its highest daily position in the sky, crossing the meridian, at midday (noon local standard time, accounting for distance from the centre of our time zone). However, the Sun’s daily north-south movement over the seasons and Earth’s varying speed in orbit make the Sun appear to reach the meridian ahead or behind schedule by as much as 16 minutes. Consequently, our 24-hour clock is based on an annual average noon called mean solar time. Sundial aficionados know they have to account for these daily corrections to agree with the clock.

This Week in the Solar System

Saturday’s sunrise in Moncton is at 5:27 am and sunset will occur at 9:10 pm, giving 15 hours, 43 minutes of daylight (5:35 am and 9:12 pm in Saint John).  Next Saturday the Sun will rise at 5:27 am and set at 9:13 pm, giving 15 hours, 46 minutes of daylight (5:36 am and 9:15 pm in Saint John).

The Moon passes above Mars this Sunday and it is at first quarter late Thursday evening, after midnight. Friday evening, the 110 kilometre lunar fault line known as Rupes Recta or the Straight Wall will be visible in a telescope. At midweek, Venus sets around 10:45 pm, followed by Mars 50 minutes later, and within the next hour Saturn and Jupiter will have risen.

With astronomy meetings and outreach activities on hold you can watch the local Sunday Night Astronomy Show at 8 pm, and view archived shows, on YouTube at:  https://www.youtube.com/channel/UCAEHfOWyL-kNH7dBVHK8spg

Questions? Contact Curt Nason at nasonc@nbnet.nb.ca.

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