By Patrick Birck
Winter is a great time to explore the wonders of one of the sky’s most recognizable constellations, Orion the Hunter.
On Jan. 1, Orion rises early in the evening in the eastern sky, travels across the sky throughout the night, and sets in the west in the wee hours of the morning. Throughout January, Orion rises and sets earlier each day. It contains a wide variety of interesting stars and deep sky objects. Many of Orion’s stars are visible to the naked eye, and many more are visible through a telescope or binoculars.
Two of Orion’s most distinctive features are the hunter’s belt and sword.
The sword, just below the belt, contains the constellation’s most famous feature, the Great Orion Nebula. From a dark viewing site, the Nebula appears to be a faint smudge, but with a telescope it becomes a large area of nebulosity (dust and gas). The nebula contains many stars, the most famous of which form Trapezium. Four relatively young, hot stars form this trapezoid. This area of Orion is known for birthing stars.
The belt consists of three bright stars in a straight line and many stars of lesser brightness. The right most star, Mintaka, also known as Delta Orion (magnitude 2.2), is an obvious double star when seen through a telescope. The middle star,
Alnilam, also known as Epsilon Orion (magnitude 1.7), is also an obvious double star through a telescope. The left most star, Alnitak, also known as Zeta Orion (at magnitude 1.8), is also a double star through a telescope, but is somewhat difficult to split.
A quick note about magnitude: The lower the number (that is, the closer to zero) the brighter the star.
None of Orion’s stars are more apparent to the naked eye than Betelgeuse and Rigel.
Betelgeuse, in the upper left corner of Orion, also known as Alpha Orion, is about 430 light years from Earth. It is so large that, were it in our solar system, it would encompass Mercury, Venus, Earth, and Mars. To the naked eye, Betelgeuse appears slightly red or orange. With a magnitude of 0.65, it’s currently the 10th brightest star in the sky. Betelgeuse is part of a multiple star system consisting of five stars, but, even with a typical amateur astronomer’s telescope, the other stars are too dim to be seen.
Rigel, in the lower right corner of Orion, also known as Beta Orion, is approximately 770 light years from Earth. Rigel is a blue/white, very hot star with magnitude 0.2 (the seventh brightest star). It’s part of a four-star system, but it’s the only one that’s visible through a typical amateur astronomer’s telescope.
Two other bright stars in Orion are Bellatrix, also known as Gamma Orion (magnitude 1.6) and Saiph, also known as Kappa Orion (magnitude 2.0). Bellatrix, in the upper right corner of Orion, like many other stars in Orion, is a double star. Saiph, in the lower left corner of Orion, is a single star.
There are many other deep sky objects in Orion visible only through binoculars or a telescope, but you only need your eyes (and a reasonably dark sky) to see much of Orion’s beauty.
Just get out and look up.
Patrick Birck is a former president of the Prescott Astronomy Club. He moved to Prescott from Maryland eight years ago. When he’s not stargazing, he’s probably playing third base on a senior softball team.
For more stargazing info, visit PrescottAstronomyClub.Org.