Monday, January 25
Roughly two hours before sunrise, the Moon has finally set and Gemini the Twins are standing upright on the western horizon. The Twins’ heads, Castor (which appears on the right) and Pollux (left), shine brightly about 20° high.
They’re roughly the same magnitude (Pollux is a few tenths of a magnitude brighter) but through binoculars or a telescope, you may notice they’re slightly different colors: Castor appears blue-white, while Pollux is a bit more orange-hued. That’s because Castor is a hot type A star, while Pollux is a type K star and slightly cooler than the Sun.
But Castor has another advantage over Pollux: sheer numbers. A small telescope will reveal that Castor appears to be not one, but two stars about 4" apart. Called Castor A and B, both are type A stars. However, the Castor family is larger, still — Castor C, which is visible about 70" from A, is a cooler, dimmer type M star orbiting A and B together.
Each of these three stars is also a binary, bringing the total number of stars in the Castor system to six.
Sunrise: 7:14 A.M.
Sunset: 5:11 P.M.
Moonrise: 2:12 P.M.
Moonset: 4:49 A.M.
Moon Phase: Waxing gibbous (90%)
Tuesday, January 26
A few days ago, we visited Canis Minor. Tonight, let’s visit Canis Major, which has cleared the horizon by two hours after sunset. Wait a little longer, and it will rise even higher in the sky.
Again, the bright Moon is nearby, but tonight we’re seeking out a bright open cluster, NGC 2362, also called the Tau Canis Majoris Cluster after its brightest star: Fourth-magnitude Tau (τ) Canis Majoris. This star dominates the cluster’s light; you’ll need to train binoculars or a small scope on the region to see any of its neighbors. Look about 2.8° east-northeast of Wezen (Delta [δ] Canis Majoris), which marks the top of the Big Dog’s hindquarters, to find the cluster. It covers roughly 8' of sky, although some stars may be hard to spot with the Moon’s brighter background light. (So keep this target in mind and plan to return once the Moon’s phase has progressed.)
Tau itself is sometimes called the Mexican Jumping Star, possibly because it always remains relatively low in the sky. That, coupled with its relative brightness, makes it particularly susceptible to
scintillation, which occurs when starlight is viewed through Earth’s turbulent atmosphere. This can cause a star to change apparent brightness and even color quite rapidly, sometimes looking as if you’re viewing it through a kaleidoscope. Sirius, the Dog Star, is also subject to this effect when it’s low on the horizon.
Compare the two now — Sirius is roughly 11° higher in the sky, climbing away from the turbulent horizon air more quickly, and so may be twinkling less.
Sunrise: 7:13 A.M.
Sunset: 5: 13 P.M.
Moonrise: 3:05 P.M.
Moonset: 5:46 P.M.
Moon Phase: Waxing gibbous (95%)
Wednesday, January 27
With a nearly Full Moon in Cancer tonight, only bright stars are easily visible. After sunset, test your eyesight in Taurus the Bull, who hosts the famous Pleiades star cluster, also cataloged as M45. Most observers can see six or seven stars with the unaided eye, and that might be the most you’ll see tonight. But come back in several days on a darker night and you may see as many as 11 stars without optical aid, depending on the quality of your eyesight.
The Pleiades is a young open cluster of stars estimated at just a few tens of millions of years in age. Look to their southeast and you’ll find another open cluster of stars making the “v” of the Bull’s face: the Hyades, one of the closest open star clusters to Earth. Among them shines bright Aldebaran, the eye of the Bull, although this star is not actually part of the cluster. It’s also moving in a different direction on the sky than the cluster, meaning Taurus’ v-shaped visage will eventually start to deform over the next several tens of thousands of years.
Keep following a line drawn between the Pleiades and Hyades, and eventually you’ll reach Betelgeuse, the famous red giant star marking the shoulder of Orion the Hunter. This star became recently famous as it underwent a
strange dimming event that astronomers attribute to a “stellar sneeze,” in which the star blew out a cool cloud of dust, temporarily blocking some of its light. It’s now back to its original brightness.
Sunrise: 7:13 A.M.
Sunset: 5:14 P.M.
Moonrise: 4:04 P.M.
Moonset: 6:38 A.M.
Moon Phase: Waxing gibbous (99%)