Fellow Durango Herald columnist Andrew Gulliford recently extolled the virtues of presidential dog ownership, and there is even a celestial precedent for having dogs. Orion, the great hunter in the winter sky, has two dogs following him in his nightly westward trek. His big dog is Canis Major, and his little dog is Canis Minor.
Canis Major includes the sky’s brightest star Sirius and several noteworthy open clusters. Sirius is the dog star. If you are a Harry Potter fan, you will already know that Sirius Black was the character who could change into a large black dog. A fun myth about the star Sirius is that when it is out in the daytime (during the summer months) the dog days of summer are so called because the brightness of Sirius adds its heat to that of the sun.
Sirius is the brightest star in the sky for two reasons. It is one of the sun’s nearer companions at only 8.6 light years distance, and it is 25 times more luminous than the sun. Sirius is also a double star, but you likely won’t see the pair even through a telescope. Sirius A is a main sequence star, which means it is a mid-life adult star. It is roughly twice as massive as the sun, which is what makes it hotter and thus bluer and more luminous than the sun.
Sirius B is a white dwarf. A white dwarf is the leftover core of a main sequence star that has finished its life cycle. After using up the hydrogen and helium in its core, the star evolved through a red giant phase and ejected its hydrogen shell into a planetary nebula that has now completely dispersed. This white dwarf has almost as much mass as the sun, but it is compressed into the size of the Earth.
About 4 degrees to the south of Sirius is the open cluster M41. This cluster is the size of the full moon and contains about 100 stars. It is easily visible in binoculars and will appear as a faint fuzzy patch to the naked eye under dark skies.
Canis Minor, the lesser dog, has only two easily visible stars – Procyon and Gomeisa. Procyon is slightly farther than Sirius, and slightly less luminous, a combination that still makes it the eighth brightest star in the sky. And like Sirius, it is a main sequence star with a white dwarf companion.
This monthFind Sirius and the rest of Canis Major by following the line made by Orion’s belt toward the east a little over 20 degrees, or just over two fist widths at arms length. Procyon and Canis Minor will be 25 degrees (two and a half fist widths) to the north of Sirius.
Venus is still the bright evening star. Mars is continuing to dim and is just over 5 degrees above and to the left of Venus. On Feb. 26, Uranus will move to less than 1 degree to the east of Mars. At almost 6th magnitude, Uranus is on the edge of naked-eye visibility. Jupiter is rising around midnight and will be the brightest object in the sky after Venus has set.
When the full moon rises Feb. 11, it will be slightly dimmer than usual. This is because of a penumbral eclipse. The moon will be passing through part of the Earth’s shadow, but no part of the moon will be totally darkened. If you were standing on the moon, you would be seeing a partial solar eclipse.
Two weeks later, on Feb. 28, Durango will experience another new moon. However, for those in the far southern hemisphere, there will be an annular solar eclipse. This is where the moon passes in front of the sun, but at apogee, the moon is too small to completely cover the sun.
Comet 45P/Honda-Mrkos-Pajdusakova that I mentioned last month has turned out to be not very bright. It will make its closest approach to Earth on Feb. 11, but at dimmer than 8th magnitude, it will be quite a telescope challenge to see.
Charles Hakes teaches in the physics and engineering department at Fort Lewis College and is the director of the Fort Lewis Observatory. Email him at firstname.lastname@example.org.