Moon Meets The ‘Bull’s Eye’ Star As Mars Greets Uranus: What You Can See In The Night Sky This Week

Each Monday I pick out the northern hemisphere’s celestial highlights (mid-northern latitudes) for the week ahead, but be sure to check my main feed for more in-depth articles on stargazing, astronomy, eclipses and more. 

What To Watch For In The Night Sky This Week: January 18-24, 2021

Stargazers strike ‘bull’s eyes’ this week as the night sky takes on a distinctly bovine theme. Let me explain. If the skies are clear where you are early this week take some time to look southeast after dark for the constellation of Taurus, the bull, then try a star-hop from Orion to a stunning star cluster via the “bull’s eye” star—Aldebaran. 

With a Last Quarter Moon on Wednesday, the night skies will begin to brighten, making star-spotting more challenging. However, a nice tableau of a “half-Moon” near Mars on Thursday also brings a chance to use the red planet to find Uranus, the dim and distant seventh planet that just happens to be close by. Uranus is sometimes called the “bulls-eye planet” because of its unusually vertical rings. 

Later this week also presents a great opportunity to find the tiny, fast-moving planet Mercury in the post-sunset night skies. 

Constellation of the week: Taurus, the bull

Here’s one of the most famous constellations of all—and one of the zodiacal constellations the Sun appears to travel through each year—though it tends to get overshadowed by nearby Orion. A jewel of the winter night sky in its own right, have a go at finding bright orange supergiant star Aldebaran—the “eye of the bull”—and trace-out the V-shaped horns of the bull that stretch above to two stars, Zeta Tauri and Alnath, the latter of which is above Orion. 

Star-hop: Bellatrix to the Pleiades 

Have you seen the “baby Big Dipper” yet? A sparkling star cluster and one of the highlights of the winter sky, the Pleiades can be easily found shimmering above the southeastern horizon after dark tonight, but here’s a fun star-hop. First find the three bright stars of Orion’s Belt. There are two bright stars to the left of Orion’s Belt just after sunset—Betelgeuse lowest and Bellatrix above itt. From Bellatrix travel in a straight line to the first bright star. That’s Aldebaran. Now travel the same distance again and you’ll come to the Pleiades. An easy star-hop, but the Pleiades is around 440 light years from us. Its six or seven easily visible stars—hence its “Seven Sisters” nickname—are a mere 100 million years old. For context our Sun is a 4.6 billion year-old star. They’re baby stars! 

Wednesday, January 20, 2021: First Quarter Moon

Tonight the Moon reaches First Quarter, which means it hangs in the south looking half-lit. Although it’s a beautiful sight—and if you have binoculars or a small telescope it’s a great time to look at craters on its terminator (that line down its middle between light and dark)—it does mean the night skies get bleached slightly. Stargazing gets harder, and you will struggle to see any “shooting stars” from tonight’s minor γ-Ursae Minorid meteor shower. 

Thursday, January 21, 2021: Moon, Mars and Uranus in conjunction

Uranus is so far away and faint that you almost certainly won’t see it with your own eyes, but it is possible and arguably slightly easier than usual tonight because the seventh and fourth planets from the Sun appear together in conjunction. Mars will be so much brighter than Uranus and easily seen with the naked eye, while the faint planet will likely require binoculars or a small telescope to glimpse. You also find a 60%-lit Moon just 5.1º from the planetary pair. 

Saturday, January 23, 2021: the Moon meets Aldebaran

After the Sun has set in the west tonight look to the southeast and you’ll see a big, bright 78%-illuminated Moon close to Aldebaran, the brightest star in the constellation of Taurus.

Sunday, January 24, 2021: Mercury after sunset

If you’ve never seen Mercury then here’s a great chance, though you will need to have a view low to the southwestern horizon to stand a chance. Since Mercury is the closest planet to the Sun and orbits it in a swift 88 Earth-days, it’s usually lost in its glare from our point of view. 

However, Earth and Mercury’s orbits are in such a position that Mercury will this evening appear to be at what astronomers call its greatest elongation east. What that means is that it’s 18.6º east of the Sun, so it’s visible just after the Sun sets for a few days. Look low to the southwest, and be patient. Binoculars will help, but don’t even think of pointing them west before the Sun has completely set. 

Times and dates given apply to mid-northern latitudes. For the most accurate location-specific information consult online planetariums like Stellarium and The Sky Live. Check planet-rise/planet-set, sunrise/sunset and moonrise/moonset times for where you are. 

Wishing you clear skies and wide eyes.