Driftless Dark Skies: Winter Asterisms

The January sky glitters with gatherings of stars known as asterisms. Asterisms tend to be smaller than familiar constellations such as Orion the Hunter, Taurus the Bull, and Auriga the Goatherder. While asterisms do not enjoy the “official” status of the 88 constellations, they are simple patterns that are easy to recognize and have long been part of the human heritage of stargazing.

Orion’s Belt is one of the brightest. Look east this month around 6pm and spot three stars less than a finger’s width apart in a row rising up from the horizon. From top to bottom, these blue giant stars are called Alnitak, Alnilam, and Mintaka. While they may seem close together, it’s just a chance alignment as viewed from Earth with hundreds of light years between them. Dangling to the right of Orion’s Belt is Orion’s Sword with three stars that are dimmer and closer together. If your eyesight is sharp, you may notice that the middle “star” is a bit fuzzy. That’s the Great Orion Nebula, a collapsing cloud of gas and dust where hundreds of stars are being born in a stellar nursery. With simple binoculars, you can spot several of these baby stars adrift in the nebula. It’s the closest star formation region to Earth, only 1340 light years
away.

Follow up from Orion’s Belt about two outstretched fists, and you will arrive at the bright orange star Aldebaran and the Hyades. The Hyades is an open star cluster and is a gathering of young blue-white stars born together in a gas cloud much like the Great Orion Nebula. Picture it as five stars in the shape of an arrowhead pointing to the right > with Aldebaran in the lower left corner. You can think of them as the face of Taurus the Bull with Aldebaran as the Bull’s Eye. With binoculars, you can see dozens more sibling stars that are part of this cluster. The Hyades is the open cluster closest to Earth just 153 light years distant. All of its stars are close together and slowly drifting apart. Aldebaran only appears to be part of the cluster. It’s much closer at 65 light years and just happens to be in the same line of sight.

The Pleiades, another open star cluster, is just a fist above the Hyades in the line beginning with Orion’s Belt. Like the Hyades, this is a group of newly born blue-white stars. They go by many names in different cultures including the Seven Sisters and Subaru. The Pleiades appear much closer together than the Hyades because they are thrice the distance from Earth at 444 light years. I like to remember that their light has been traveling towards us since the time when Shakespeare and Galileo were kids. Depending on your eyesight, you may be able to spot a half dozen or maybe more of the Pleiades. With binoculars, we can see dozens.

The area between the Hyades and Pleiades is sometimes known as the Golden Gate of the Ecliptic. The ecliptic is the path across the sky along which the Sun, the Moon, and the planets travel. Watch on January 2 and 3 as the Waxing Gibbous Moon passes through the Golden Gate between the Hyades and Pleiades and then again on January 29 and 30. Mars passed through the Golden Gate back in the summer and is now just to the left of the two star clusters. Mars peaked in brightness last month but is still a little brighter than Aldebaran.

Capella is about a fist above and to the left of Mars. and is the lucida or brightest star of Auriga the Goatherder. Very close to Capella are three less bright stars that are most appropriately called the Kids. It’s a small gem to enjoy on a cold January night. If you are celebrating Winter Festival at Kickapoo Valley Reserve on January 7, be sure to stop by Wildcat Mountain State Park for their Torchlight Ski/Hike/Snowshoe and bring your binoculars. If skies are clear, I’ll be there with other stargazers to share the winter asterisms!

John Heasley is an astronomy educator and stargazer who enjoys connecting people with the cosmos. He volunteers with NASA/JPL as a Solar System Ambassador , with the International Dark-Sky Association as an Advocate, and the International Astronomical Union as a Dark Sky Ambassador. For more information about stargazing in southwest WI, like Driftless Stargazing LLC on Facebook and find out whenever there’s something awesome happening in the skies.