This Week’s Sky at a Glance, February 4 – 11 ~ 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 820 light years (ly) away, 100 ly closer than Mintaka on the right. Alnilam, the middle star, is about 50% farther at 1300 ly. Orion must have a lumpy belly. Saiph and bright Rigel, marking Orion’s feet or knees, are reasonably equidistant at 770 ly and 720 ly, respectively. In the giant hunter’s shoulders orange Betelgeuse is 430 ly and Bellatrix is 245 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 more than four times brighter than Venus. Adhara, in the dog’s rear leg, is the 23rd brightest star and at the same distance as Betelgeuse (tenth brightest). Wezen in the dog’s butt is 1800 ly, and the tail star Aludra is 3200 ly distant. Obviously, the constellations are just chance alignments of stars from our viewpoint.
This Week in the Solar System
Saturday’s sunrise in Moncton is at 7:38 am and sunset will occur at 5:29 pm, giving 9 hours, 51 minutes of daylight (7:41 am and 5:36 pm in Saint John). Next Saturday the Sun will rise at 7:28 am and set at 5:40 pm, giving 10 hours, 12 minutes of daylight (7:31 am and 5:46 pm in Saint John).
The Moon is full on Friday, February 10, with the added attraction of a subtle penumbral eclipse. A light gray shading could be detectable between 8 and 9:30 pm. For a total lunar eclipse, this is the shading you see before the Moon enters Earth’s shadow and after it leaves. This time, the Moon is passing just below the shadow. If you happen to be staying at the Luna Hilton that day you would see a partial eclipse of the Sun. This Sunday, as twilight darkens, look for the Moon passing near Aldebaran, the fiery eye star of Taurus the Bull.
Venus moves a couple of degrees further westward of Mars over the week, heading toward inferior conjunction in late March. Saturn is high enough in the southeast for decent observing by morning twilight, as is Jupiter in the southwest. On Monday Jupiter ceases its normal eastward motion relative to the stars and begins four months of retrograde motion that will carry it a fist-width west of Spica. It doesn’t really back up; that is our perspective as Earth laps Jupiter in their racetrack orbits.
The Saint John Astronomy Club meets on February 4 at 7 pm in the Rockwood Park Interpretation Centre. All are welcome. The annual Irving Nature Park snowshoe hike and telescope observing occurs Friday, February 10 at the Sheldon’s Point barn in Saint John. Visit the park Web site for details.
Questions? You can contact Curt Nason here.