Sky at a Glance January 12 – 19

Photo of the winter constellations accompanied by some interesting distance to Earth comparisons in the post.

This Week’s Sky at a Glance, 2019 January 12 – 19 ~by Curt Nason

Looking at a constellation it is easy to imagine its component stars as 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 almost equidistant; at first glance they appear to be almost equally bright. Alnitak, the left star, is 1260 light years (ly) away, 60 ly farther than Mintaka on the right. Alnilam, the middle star, is much farther at 2000 ly. Orion must have a lumpy belly. 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 is an update of an article I wrote two years ago and most of the values have changed.

This Week in the Solar System

Saturday’s sunrise in Moncton is at 7:59 am and sunset will occur at 4:56 pm, giving 8 hours, 57 minutes of daylight (8:01 am and 5:03 pm in Saint John). Next Saturday the Sun will rise at 7:54 am and set at 5:05 pm, giving 9 hours, 11 minutes of daylight (7:57 am and 5:12 pm in Saint John).

The Moon is at first quarter on Monday and it sits to the left of Aldebaran after sunset on Thursday. Jupiter lies nine degrees to the lower left of Venus this Saturday; watch them close the gap by half over the week. Mercury meets up with Saturn in the morning sky this weekend but they will be difficult to observe, rising just half an hour before the Sun. Mars resembles a first magnitude red star in the southwest during the evening.

There will be public observing at Moncton High School Observatory on Friday, January 11 from 7:00 pm to 8:30 pm. RASC NB, the provincial astronomy club, meets in the Rockwood Park Interpretative Center on January 19 at 1 pm. All are welcome.

Questions? Contact Curt Nason.

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