Three naked eye planets are completely or mostly out of sight this month. A few people may catch a glimpse of Mercury early on. Venus and Mars are simply too close to the sun all month.
Earth is at perigee just a few days into the month. Our planet will be 98.3% of its average distance from the sun on the 3rd. That’s just two days after the moon starts the new year at perigee, 360,400 kilometers from Earth. Apogee will be on the 13th at 405,400 kilometers. We get a second lunar perigee on the 29th at 364,900 kilometers.
We also get two northern lunistices this month. The first is on the 2nd at 28.3 degrees north. The southward crossing over the equator is on the 8th. Southern lunistice is on the 16th at 28.3 degrees south. Luna goes north over the equator on the 23rd. The next northern lunistice after that is on the 29th at 28.4 degrees north.
The moon’s almost full on the 2nd when it occults Elnath in Auriga for observers in much of South America, the southern Atlantic Ocean, and Liberia. Full phase is on the 3rd. The moon will be close to Jupiter and Pollux in Gemini that night. A few nights later, a waning gibbous moon passes by Regulus. Some observers in Asia get an occultation. Last quarter phase is on the 10th when the moon passes by Spica.
After that, the next bright star the moon passes is Antares on the 14th. New moon happens on the 18th. The close call won’t be visible, but the moon’s also close to Venus and Mars that day. Seeing the moon near Saturn on the evening of the 23rd won’t be a challenge though. Neptune is also nearby.
First quarter phase is on the 26th. As the moon passes close to Uranus on the 27th, it also occults the Pleiades for northern hemisphere observers. Then we have another Elnath occultation on the 29th. You’ll have to be in a western Pacific Ocean location to see that. The month ends with the moon in Gemini again near Pollux and Jupiter.
Venus is at superior conjunction on the 6th. Within a few weeks, you can spot the planet in the evening sky. Binoculars will help you find it. Since Venus will set not long after sunset, you’ll have to find it close to the horizon with the dusk light still bright. Also on the 6th, Mercury is at aphelion, 0.467 astronomical units from the sun.
Venus and Mars would appear at their closest on the 8th. But their apparent proximity to the sun means we don’t get to see the close call. Mars is in conjunction with the sun on the 9th. Mars and Mercury are closest on the 18th.
Mercury’s superior conjunction happens on the 21st. Mercury and Venus appear closest on the 29th. If you’re careful and observing close to the equator, you can spot Mercury early in the month rising before the sun.
Jupiter is at opposition on the 10th. So the planet is up all night this month. And it’s closest to Earth, giving the best views in telescopes. Jupiter passes very close to Wasat at the waist of Pollux around the 18th.
Saturn is up in the evening, partway up the western side of the sky dome at dusk. The view in a telescope reveals the rings becoming less edge-on than last month. Binoculars or a telescope will help you see Neptune somewhat close to Saturn. And the magnification will help you spot Ceres and Hebe. Ceres had the distinction of being the first asteroid discovered until the International Astronomical Union categorized it as a dwarf planet. Hebe is the sixth asteroid discovered. Both orbit in the asteroid belt between Mars and Jupiter.
In the popular imagination, the asteroid belt is thought of as a planet that broke apart or one that never came together. Scientists today say the latter is more accurate, but they say the most accurate description is these asteroids are rocks that never joined any of the other planets as they were coming together. The asteroids in the belt don’t have as much mass all together as Earth’s moon. Ceres itself is believed to have 1/3 of the asteroid belt’s cumulative mass. Some of the asteroids are big solid pieces. Others are what we might liken to piles of gravel, except they don’t pile up like on a hill. The pieces hang on to each other through gravity.
The variable star Mira is on its way to peak brightness, which should happen in early March. With binoculars or a telescope, you can spot the star now. And it may become bright enough to see with the naked eye this month. It goes from about magnitude 10 at its dimmest to magnitude 2 at its brightest.
For most northern hemisphere observers, January nights are the coldest but are already getting noticeably shorter. Away from the fronts, cold air masses provide dense air with less turbulence and less moisture. This makes it easier to see dimmer stars and finer details on planets. Sometimes, when you’re out on such a night and the seeing isn’t so good after all, it’s an early warning of coming snow or rain.