Triple-Treat SkyWatching This Week!

December 13th, 2017 by Tavi Greiner

This week’s night sky offers a solar system triple-treat, with the Geminid meteor shower on Wednesday night/Thursday morning (12/13-12/14) – a close grouping of Jupiter, Mars, and the crescent Moon on Thursday morning (12/14) – and a near-Earth pass of the Geminids’ source, 3200 Phaethon, on Saturday night (12/16).



Geminids, NASA/JPL

The Geminids; so-called because the shower appears to radiate from constellation Gemini; is a typically prolific event, with frequent fireballs and peak rates of dozens of meteors per hour – and the  meteors, themselves, are bright and often leave long trails. This year’s event should be especially fruitful, with a morning crescent moon offering darker skies for better viewing. has already reported 40+ fireballs in the past three days, so peak night could be especially exciting. UPDATE: reported 475 Geminid fireballs, as of 12/14!

Gemini & Orion, Sky Safari graphic

Gemini rises from the east around 8pm local time, directly east (or to the left) of constellation Orion. As the night progresses, the two constellations will appear to rotate higher and toward the south and west, with Gemini positioned to the upper-left of Orion above the south around 1am, and directly above Orion above the west by 5am. Although Gemini is our meteor-watching focal point, Orion is a much more prominent constellation, so use it to help you keep track of Gemini’s location.


Orion Nebula, Hyades, Pleiades

While you’re watching that region of the sky, take a moment with a pair of binoculars to observe the Orion Nebula and the Pleiades and Hyades star clusters. The nebula can be spotted within Orion’s three “belt stars’; Hyades appears as a V-shaped grouping to the upper-right of Orion – you can use bright red Aldebaran to spot it; and Pleiades is that tighter, brighter cluster located to the near upper-right of Hyades.

If you’re looking closer to dawn, the clusters will be directly right of Orion, as the constellation progressively appears to tilt to the right, when watched from our planet’s rotating point of view. And don’t stop with those three beauties – take your time scanning the entire region to find other star clusters, passing satellites, and maybe even an asteroid or two!



Moon, Mars, Jupiter

As Orion begins to sink into the west, with Gemini following close behind, turn toward the ESE horizon to see the waning crescent Moon rising with Mars and Jupiter. Mars will appear as a reddish star just above the Moon, and Jupiter will be that distinctly bright “star” just beneath the Moon. Together, the three will form a tilted triangle, with Luna at the left corner, Jupiter in the right corner, and Mars at the peak.


Earthshine Moon, Tavi Greiner

A closer look with your binoculars will reveal some hidden gems within the Moon, Mars, Jupiter  – Jupiter’s four brightest moons! Callisto, Ganymede, and Europa should be visible in a line close beneath Jupiter, while Io will be positioned, a little more distant, above the planet.

When the sky begins to brighten, around 6am, use those binoculars to explore the unlit region of the Moon. You’ll notice that the dimmer Earth-reflected sunlight allows you to see lunar features more clearly, as opposed to the glaring brightness of a directly-sunlit fuller Moon. If you have a camera, try capturing an image of that “earthshine”, in both a close-up image and in a wide-field shot of Luna and the two planets.



Phaethon in Andromeda

For those observers interested in a serious challenge, more-powerful binoculars or a small telescope can be used to track the Geminid’s source object, 3200 Phaethon, as it passes through constellation Andromeda, on Saturday night. Astronomy author, Bob King, has provided an excellent write-up and observing charts on the Sky&Telescope website, here.

Sometimes referenced as a “rock-comet”, 3200 Phaethon is a near-Earth-asteroid that passes close enough to the Sun to lose its rocky crust to fracturing and vaporization, an ongoing event that we experience each year as the Geminid meteor shower, when Earth passes through the resulting stream of granulated debris.

Phaethon rounds the Sun every 1.4 years (524 days), but we won’t see the asteroid this close to Earth for nearly eight decades. Not only are amateur astronomers already tracking the fast-moving object with backyard telescopes and remote observatories, professional scientists are taking advantage of the pass to acquire radar images using NASA’s Goldstone facility and the Arecibo Observatory in Puerto Rico .



Whether you observe one, two, or all three of this week’s “triple-treat”, be sure to dress warmly, get comfortable, carry a red-filtered flashlight, and enjoy your star-gazing fun with family, friends, and neighbors. Check out the links, below, for the many ways that you can share your results with others!


Fun Fact: Twenty-one (21) Near-Earth-Objects are passing close enough to be measured in lunar distances, in the month of December. Seventeen (17) of those were discovered just this year. The closest of those twenty-one passes is by the 56-meter-wide Apollo-class object, 2006XY, tonight (12/13-12/14)!


Citizen Science: If you’d like to do more than watch, consider one or more of the following:

  1. Submit your visual Geminids meteor count to the American Meteor Society. Their Visual Observing page includes viewing tips and observation forms.
  2. If you’re in Great Britain, submit your visual count to the British Astronomical Society. Their Visual Observing page includes tips and observation forms.
  3. Listen to the meteor shower’s radio pings on Space Weather Radio and report your count on Twitter, using the #Geminids and #meteorpings hashtags.
  4. Share your meteor and Moon/planet images with our Astronomy.FM Twitter and Facebook
  5. Share your Phaethon observation report, images, and/or sketches with our Astronomy.FM Twitter and Facebook
  6. You can also share your images on the Spaceweather gallery and in the Universe Today Flickr group.

Tags: , , , ,

Comments are closed.