This Week’s Sky at a Glance, 2021 January 9 – 16 ~by Curt Nason
Looking at a constellation it is easy to imagine its component stars being fairly close together in space, as if it is an actual body. Let us look at two prominent winter constellations to see if that is true. Surely the three stars of Orion’s Belt are equidistant; at first glance they appear to be almost equally bright. Alnitak, the left star, is 1260 light years (ly) away, slightly farther than dimmer Mintaka on the right. Alnilam, the middle star, is much farther at 2000 ly. Saiph and bright Rigel, marking Orion’s feet or knees, are reasonably equidistant at 650 ly and 860 ly, respectively. In the giant hunter’s shoulders orange Betelgeuse is about 600 ly away and Bellatrix is 250 ly.
Following the belt to the lower left we arrive at Canis Major, the Big Dog, with brilliant Sirius at its heart. Sirius is the brightest star of the night sky and the closest naked-eye star we can see in New Brunswick at 8.6 ly (only 82 trillion kilometres), which is the main reason it is the brightest. If Rigel were that close it would be about as bright as the quarter Moon. Adhara, in the dog’s rear leg, is the 23rd brightest star and 430 ly away, Wezen in the dog’s butt is 1600 ly, and the tail star Aludra is 2000 ly distant. Obviously, the constellations are just chance alignments of stars from our viewpoint. The distances cited here are taken from Wikipedia, but other sources could vary significantly as stellar distances are difficult to determine precisely.
This Week in the Solar System
Saturday’s sunrise in Moncton is at 8:00 am and sunset will occur at 4:53 pm, giving 8 hours, 53 minutes of daylight (8:02 am and 5:00 pm in Saint John). Next Saturday the Sun will rise at 7:56 am and set at 5:01 pm, giving 9 hours, 5 minutes of daylight (5:58 am and 5:09 pm in Saint John).
The slim waning crescent Moon is near Venus on Monday and it is new on Wednesday. Jupiter, Saturn and Mercury make an interesting array of triangles from Saturday to Tuesday as Mercury slides up to the left of the other two. With a clear sky and a good horizon you might catch all three in the same binocular field before they set at 6 pm. Mars is high in the south in evening twilight, glowing as brightly as Vega. Venus continues to edge sunward in the morning, heading toward superior conjunction in early spring. Uranus is stationary on Thursday (make up your own joke), resuming its slow eastward motion against the stars.
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.