Perhaps the most recognizable constellation in the winter sky is Orion. Many people unfamiliar with the night sky can at least recognize the three stars of Orion’s belt. That is the asterism confused with the cat’s collar in “Men in Black.”
From east to west (left to right when Orion is high in the northern hemisphere sky), the belt stars are Alnitak, Alnilam and Mintaka. They appear close to each other in the sky, but they are at greatly differing distances. Alnitak is approximately 700 light years distant, Mintaka is around 900 and Alnilam is about 1,350 light years away.
The belt lies almost right on the celestial equator, so Orion is one of the few constellations visible to both northern and southern hemisphere observers. Also because it is on the equator, it is a good indicator of east when Orion rises, and west when it sets.
The belt also makes a good pointing tool. Following the line of stars to the west leads to Aldebaran in Taurus. Eastward, they point to Sirius, in Canis Major.
As with many of the brighter stars in the night sky, the belt stars are blue or blue-white supergiants. Burning their fuel at rates hundreds of thousands of times that of the sun, these stars will be very short-lived.
Adjacent to Alnitak are two prominent nebulae. The Flame Nebula and the Horsehead Nebula are extremely challenging objects to observe visually, partially because of their proximity to such a bright star. However, both nebulae do show up in easily in photographs.
Along with the belt, Orion is identified with the bright stars Betelgeuse and Rigel. I often use those two to point out differences in star color. Betelgeuse is similar in apparent brightness to Rigel, but is noticeably redder in color.
Betelgeuse is one of the few stars to ever have its diameter measured directly. If Betelgeuse took the place of our sun, it would swallow the Earth and the star’s surface would be somewhere near the orbit of Jupiter.
Orion will be rising shortly after sunset.
Venus and Mercury will be within 1 degree of each other for a few days around Jan. 10. Look for them shortly after sunset.
Jupiter is rising just after 10 p.m., just to the right of the backward question mark in the constellation Leo.
The usually reliable Quadrantid Meteor shower peaks on the morning of Jan. 4, but that is only a day before the full moon Jan. 5, so many of the faint meteors may not be visible.
Charles Hakes is an assistant professor in the physics and engineering department at Fort Lewis College and is director of the Fort Lewis Observatory. [email protected]