This week in What’s Up is another meteor shower, the Geminids. This meteor shower is known for being reliable compared to others. However, the time the meteors will be visible this year is limited by the Moon’s brightness.
The source of the Geminids, the radiant or the point on the sky the meteors come from, is easy to find. In the south-southwest is the brightest star in the sky, Sirius. Follow it well up to the pair of stars that are Castor and Pollux, two of the major stars in the constellation Gemini. The radiant for the Geminids is slightly west of the star Castor, the western star of the pair, as viewed during the morning of December 14 during the peak of the shower.
At 2 am on the 14th, no matter where you are on the planet, is the peak of the shower because that’s when the radiant is highest in the sky, but it’s visible starting the night of the 13th. Unfortunately so is the Moon, and it won’t set until 3 or 4 am. However, the Geminids are bright enough that you may see some of them even while the Moon is up. At a dark sky site, you can see as many as fifty meteors an hour, and in better years without a nearly full moon, you could see up to 150 meteors an hour.
The comet that provides the material for the Geminids is 3200 Phaethon, a “rock comet” otherwise known as an asteroid in a really eccentric orbit. In this case, 3200 Phaethon’s orbit goes from between the orbits of Mars and Jupiter all the way to seven times closer than Mercury’s orbit at 0.14 astronomical units. This is the closest any named asteroid gets to the Sun. It was the first asteroid to be discovered by spacecraft data after two scientists found it using images from the Infrared Astronomical Satellite. It was formally named 3200 Phaethon in 1985. It is a potentially hazardous asteroid because it does cross Earth’s orbit, but given that it has been continuously observed for 36 years, its orbit is well known. The closest it will get in the next 178 years is just inside the Moon’s orbit in December 2193.
Now our usual advice on how to see a meteor shower: with the unaided eye, the widest field of view you can get. Be sure to let your eyes get well adjusted to the dark; don’t use a planetarium app on your phone. Even if it has a red light function the brightness will impact your dark adaption. You can download a map from a link at our website and print it out to bring with you to the field. Use a proper red light flashlight to see the map when you’re out. You can get one from Amazon using our affiliate link so we can benefit as well. A reclining chair or hammock may also be helpful for remaining comfortable for hours of looking for meteors.
If you want to try to take pictures of this meteor shower, the best way to do that is to use an interchangeable lens camera with a wide-angle lens, at least 20mm, wider if possible. Erik likes the new Canon RF 16mm f/2.8 lens which he rented on his own a few months ago to try out. You can see a full review of that lens that Erik presented a few weeks ago at a link in our show notes for this episode. Note: We’re not sponsored by Canon (but we could be). Mount your camera on a tripod and take very long exposures using bulb mode and a remote shutter release cable (but not an app on your phone because you want to preserve your night vision), and you might capture a few meteors.
So remember, any night with a clear sky is always a good night to look up, but some nights might be better than others. Good luck hunting for meteors!
3200 Phaethon (NASA JPL)