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There's no denying that Mars is now one of the brightest lights in the night sky. Only Jupiter and the moon exceed it. The Red Planet shines from Taurus the Bull. Rising shortly after sunset in the northeastern sky, Mars clears the treetops around 7 p.m. local time, shining with a powerful, fiery light in the company of another orange-red luminary, the star Aldebaran.
Mars also joins Betelgeuse inside the scintillating Winter Hexagon, a gigantic, six-sided asterism comprised of the brightest stars of the season: Rigel, Sirius, Procyon, Pollux, Capella and Aldebaran. That's a lot of firepower in just one slice of sky!
At magnitude -1.8, the Red Planet is even brighter than Sirius, the night sky's brightest star. About every 26 months, the faster Earth catches up to slowpoke Mars and passes it at opposition, the time when the two planets are closest. As the name implies, Mars appeared directly opposite the sun in the sky that evening, rising at sunset and shining the entire night. That happened on Dec. 8. Since then we've been slowly parting ways but will remain close (and Mars stunningly bright) for the next couple months.
Earth's orbit is nearly circular, but Mars revolves around the sun on a more elliptical orbit, which looks something like a squashed circle. When the two planets line up at opposition, sometimes Mars sits at the far end of that ellipse so it's more distant from the Earth. Other times it's on the near end, so the two planets get especially close.
This opposition is smack in the middle, neither close nor far, but it's the closest the two planets will get until May 2031 — all the more reason to get outside and enjoy the sight of this little but bigly-bright red orb.
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Mars is truly small. With a diameter of just 4,212 miles (6,780 km) it's just twice the moon's size. That's why you'll need a telescope that can magnify at least 75x so you can poke around on its surface in search of dark markings and the bright cloud cap known as the North Polar Hood. The higher the magnification the better. I've found that a red filter greatly helps to improve the contrast of surface features as well as to "calm" the image and tame glare.
Mars is something of a rarity as the only planet with a plainly visible surface. All the rest are covered in clouds except for Mercury, which is so small and close to the sun it's next to impossible to discern anything more than its changing phases.
Keep an eye on the Red Planet, and you'll see something a little peculiar. Normally, planets travel from west to east across the sky as they orbit the sun. That's exactly what Mars was doing a few months ago before it slowed down, stopped and then reversed direction. It's now moving to the west in retrograde motion and will continue to do so until early January, when stops once again and then turns back east.
Appearance aside, Mars isn't actually stopping and switching directions. That would be catastrophic! Instead, we're seeing what happens when the faster planet (Earth) laps the slower one. When you pass a slower car on the freeway you move into the left lane and accelerate. As you do, the car you're passing appears to travel backwards and recede behind you. That's exactly what's happening with Mars. We're passing it, so it temporarily appears to slide backwards in the sky.
If you check on Mars once a week, you'll clearly see it retrograde to the west. By the end of December it will shine directly atop Aldebaran and add an extra side to the Winter Hexagon, making it a Winter Heptagon. Nice work, Mars!
