Sky at a Glance 2023 January 7 – 14

Photo showing the Orion, Canis Major and Lepus constellations.

This Week’s Sky at a Glance, 2023 January 7 – 14 ~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 650 ly and 860 ly distant, respectively. In the giant hunter’s shoulders orange Betelgeuse is about 550 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 400 ly away, Wezen in the dog’s butt is 1600 ly, and the tail star Aludra is 1100 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 4:50 pm, giving 8 hours, 50 minutes of daylight (8:02 am and 4:58 pm in Saint John). Next Saturday the Sun will rise at 7:58 am and set at 4:58 pm, giving 9 hours of daylight (8:00 am and 5:06 pm in Saint John).

The Moon is full on Friday, January 6 and at third quarter next Saturday. Venus leads the evening parade of four planets, setting around 6:30 followed by Saturn 70 minutes later. On Monday Jupiter’s moon Ganymede, the largest in the solar system and even larger than Mercury, might be seen with a telescope disappearing behind the planet at 5:16 and reappearing at 8:13. Mars is stationary on Thursday, resuming its eastward motion away from the Pleiades and above the Hyades star clusters over the month. Mercury is at inferior conjunction this weekend, popping up in the morning sky an hour before sunrise by the end of the week.

On Sunday evening at 8 pm, tune in to the Sunday Night Astronomy Show via the Facebook page or the YouTube channel of Astronomy by the Bay.

Questions? Contact Curt Nason.

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