Nebulous space image of Messier 78

Minnesota Skies: February 2021

Your local guide to observing celestial objects and events

Published01/19/2021 , by Sarah Komperud and Thaddeus LaCoursiere

February

Orion the Hunter still strides across the evening sky as we continue to fight our way through our cloudy and snowy world. Known to them as the Wintermaker, the Ojibwe connected together the same stars as the Greeks and Romans and extended his arms to the stars Procyon (to the east) and Aldeberan (to the west)—a reach almost as long as a Minnesota winter. If the skies clear for you, this giant can guide you to a whole host of intriguing deep sky objects.

The three stars near the middle of the constellation mark out the same thing in both Ojibwe and Greek culture: a belt. Hanging below the Belt, and surely noticed by every culture to watch the sky, is one of the most famous deep sky objects: the Great Orion Nebula, or M42. Much ink (fluid and digital) has been spilled about M42, and resources to learn more are as abundant as the thousands of stars being born in the nebula. Some places to start are this NASA page, this article from Universe Today, and this Sky & Telescope page.

While the area below the belt is captivating, cast your gaze upward. From the leftmost belt star—Alnitak—a few finger widths up and to the east, you can find the reflection nebula Messier 78. About the same distance from the Earth as M42—1,300 light years—this nebula is smaller in size and requires a telescope to observe—although those with very dark skies should give it a try with binoculars! Large Earth and space-borne observatories reveal glowing clouds of gas, illuminated by massive B-class stars, cut through with cold dark dust lanes that give a 3-dimensional view to this stellar nursery.

The multitude of nebulae in and around Orion are not unexpected, given where you’re looking in the sky. Running above the star Betelguese—one of his shoulders—you can find the main disc of our galaxy: the hazy path of the Milky Way. There, you can find the greatest concentrations of gas and dust, along with the biggest and brightest stars.

Traveling down and east from the Belt, a hand length away nearer to the horizon, you can spot the famously bright star Sirius, in Canis Major. To the unaided eye—and ignoring the Sun—Sirius is the brightest star in the sky. Sirius achieves this rank in two ways: it’s twice the mass of the Sun, thus releasing more light and it’s exceptionally close compared to the rest of the stars we can see, a mere 8.6 light years away. If you expand your view and start looking at more stars, Sirius is not that exceptional. The “true” brightest star in our sky is close at hand. One fist length down, at the end of the Larger Dog, you’ll find Adhara—1,500 times the brightness of Sirius and 38,700 times the brightness of the Sun! This massive star is over 400 light years away by the best observations—limiting our view of it to a bright spot in the sky.

From the Belt, to Sirius, and down to Adhara, you can draw something of a straight line in the sky, and this will let you track down dozens more objects, from the Tau Canis Majoris cluster above Adhara, to Thor’s Helmet Nebula straight up from Sirius, to the Horsehead Nebula back near Alnitak.

Portion of  a star map including Orion, Canis Major, and Monoceros

The line can also help you find much fainter things, including a constellation made of a spattering of stars, located in between the belt and Sirius. Almost halfway in between the two is a dim reddish star named Gamma (γ) Monocerotis; at magnitude 4 it’s about one-sixth the brightness of Alnitak. A few finger widths to the east and slightly up is a similarly bright star, Beta (β) Monocerotis—described as “one of the most beautiful sights in the heavens” by the first person to make a recording of it, William Herschel. Taking a turn and going almost straight up a full fist length will bring you to Delta (δ) Monocerotis, again about the same brightness as Gamma and Beta. Taking one final turn to the east at a right angle from Delta, another fist length away, will bring you to Alpha (α) Monocerotis.

With these hops, skips, and a jump or two, you’ve tracked down almost all of the stars generally connected together into Monoceros—the Unicorn. A faint modern constellation put together in the 1600s by Dutch cartographer Petrus Plancius, this constellation does not (as far as I know) refer to any real animal on Earth. But its faint stars serve as a fun challenge for those who take the time to brave the cold and clouds as they head outside in our February skies.