Are you feeling warm? Sunday, January 6, 2020 is “perihelion day”, the day of the year when Earth makes its annual closest approach to the sun , get ready. 

For those in the frigid northern hemisphere, that seems to make little sense. In fact, perihelion isn’t the only weird and wonderful astronomical event in January 2020 that needs a little explaining. 

Here’s your skywatching guide to January 2020, with explanations and ideas for stargazing underneath. 

  • Sunday, January 5: Perihelion
  • Friday, January 10: “Wolf Moon Eclipse” penumbral lunar eclipse
  • Thursday, January 23: Jupiter occulted by the Moon (as seen from southern Australia and New Zealand).
  • Friday, January 24: New Moon (ideal conditions for stargazing for several nights either side) 
  • Saturday, January 25: Chinese Lunar New Year – “Year Of The Gold Rat” begins
  • Monday, January 27: Venus 0.07° SE of Neptune (so a great time to find Neptune with a small telescope)
  • Tuesday, January 28: Crescent Moon, Venus, and Neptune together after sunset

Perihelion and why matters

Occurring at 7:48 UTC on January 5, 2020 (so 2:48 a.m. EST), perihelion sees Earth get “just” 91,398,199 miles from the sun. It’s caused by Earth’s slightly elliptical orbit of the sun. The reason why it’s not super-warm in the northern hemisphere during perihelion is that Earth’s axis is tilted 23° relative to its orbit around the sun, and during winter the northern hemisphere is tilted away from the sun. 

So when is aphelion, the day when Earth is farthest from the sun? That will happen in 2020 on July 4, about two weeks after the solstice, when Earth will be 94,507,635 miles from the sun.

A “Wolf Moon Eclipse” 

A few weeks ago there was a solar eclipse in the Middle East and Asia. The Moon and Sun are still in sync, which will cause a slight lunar eclipse on January 10. A penumbral lunar eclipse, it’s not one to get particularly excited about because our satellite will enter only the Earth’s outer shadow. However, if you love watching or photographing the monthly rise of the moon, a penumbral lunar eclipse—which sees the full moon lose it brightness and look truly odd for a few hours—is definitely worth catching.

On January 10, 2020 only those on the night-side of Earth at 5:07 p.m. Universal Time—in Europe, Africa, Asia and Australia—will see the show. North America must wait until the “Thunder Moon Eclipse” on the July 5, 2020 to see something similar, though the regular rise of the full moon at dusk will still be an entrancing sight in clear skies. 

Stargazing in January

January’s skies are the darkest, clearest and longest of the entire year for those in the northern hemisphere. They also contain some of the most prominent, beautiful and memorable stars, constellations and asterisms (shapes) in the night sky, so January is the ideal time to go stargazing … if you can stand the cold. Bite-size stargazing is the way to go in January, taking in the famous winter constellations of Orion, Canis Major, Gemini, Taurus and Auriga—and the fabulous sights within them.

Here’s a few things to look for that are in the southeastern sky right after dark: 

  • Orion’s Belt of three stars—Alnitak, Alnilam and Mintaka—and Betelgeuse, the reddish giant star above it which has been visibly dimming in recent weeks (see below)
  • Sirius, the brightest star in the night sky, which is in Canis Major and easy to find (Orion’s Belt points almost straight at it) 
  • The two bright stars of Gemini, bright Pollux and second-brightest Castor
  • The Pleiades (or Seven Sisters) in Taurus, a sparkling star cluster of blue stars that’s among the most wondrous sights of all (head the other way from Orion’s Belt)
  • Bright star Capella in Auriga

The Winter Circle and the Winter Triangle

This is an “asterism” of the very brightest stars in the winter night sky, which puts together many of the highlights I listed above. First, find Orion’s Belt, then Betelgeuse above it, which is roughly in the middle of the Winter Circle. It’s made up of Rigel, Sirius, Procyon, Castor and Pollux in Gemini, Capella and Aldebaran just below the Pleiades. Now look for the Winter Triangle; Betelgeuse, Sirius and Procyon. 

Watching a star ‘faint’ … and go supernova?

Have you been looking at the reddish supergiant star Betelgeuse lately? The giant red star is easily found in the constellation of Orion, but it’s been noticeably dimming in recent weeks. It’s puzzling astronomers. Luckily, it’s precisely the best time of year for to take a close look at Betelgeuse, which is prominent as soon as it gets dark.

Very occasionally a star explodes—goes supernova—and becomes visible by day and night for weeks on end. Betelgeuse could go supernova at any time, and some are wondering if its recent dimming is a precursor to just that. It’s possible, but the chances of it going supernova in the lifetime of humanity—let alone that of a single person—are tiny, and besides, there are plenty of other supernova candidates in the night sky.

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