Geminid in moonlight
A Geminid fireball competes with the waning gibbous Moon on December 11, 2022. Moonlight will affect this year's shower as well.
Eliot Herman
It's a tough year for the Geminids. The annual meteor shower butts up against the nearly full Moon when it reaches maximum on the night of December 13-14. The official peak is forecast for around 8 p.m. EST on December 13th (1:00 UT, December 14). Under moonless conditions with the radiant near the zenith, up to 150 meteors per hour might be visible from a rural sky. But the 98%-illuminated waxing gibbous Moon will stick around till dawn and scrub out many — though not all — Geminids. On another night we might admire the resplendent moonlight. Just not that one.
That doesn't mean you have to hang up your coat and retreat indoors. Moonlight selectively removes the fainter meteors, those from roughly magnitude 3 down to the naked-eye limit. But everything second magnitude and brighter should push through the noise albeit with diminished luster. That includes fireballs, for which the Geminids are well-known.
Another ploy to counter moonlight would be spend more time with the shower to ensure a satisfying number of flashes. I suspect most of us will lower our expectations and accept what comes. I've watched Geminids fly by at one a minute under a really dark sky. This time around I would estimate maybe a quarter of that rate assuming no unexpected outbursts. However, since even the most reliable meteor showers can offer surprises I'd hate to skip it and learn later I'd missed something cool.
Geminids 2024
A bright Moon will wash out fainter Geminids during the shower's peak. Another option — watch the shower in a dark sky after moonset and before the start of dawn on the mornings of Dec. 12th and 13th. Geminids are easy to distinguish from stray meteors because they point back to the radiant, which is located near the bright star Castor in Gemini.
Stellarium with additions by Bob King
Although Geminid numbers tend to peak overnight as the radiant rises higher in the sky, given the timing of maximum and the Moon's presence, this might be a good year to spend more time watching during the evening hours. Weather gods permitting, I hope to be out from 9-11 p.m. local time, during which time the meteor streaming point (radiant) climbs from about 25° to 50° altitude. Starting even earlier, say around 6-7 p.m., is optimal for spotting earthgrazers — long, slow-moving meteors that strike the atmosphere tangentially. They streak upward from the northeastern horizon the way a rocket leaves a launch pad.
Watching the Geminid shower requires only a pair of eyes, the comfort of a lounge chair and a hot beverage at the ready. You'll mostly be sitting still, so dress as warmly as possible and tuck under a wool blanket or sleeping bag to trap your body heat. Shower members can appear anywhere in the sky so face any direction you like. Meteors that flare near the radiant make short streaks, while those at a distance from it produce longer ones. This is due to perspective — meteors from the radiant's direction arrive head-on while those streaking across Pegasus, for example, appear off to our side. For a pleasing mix of both, face about 90° away from the radiant, either north or south. Most importantly, avoid facing the Moon to preserve as much of your night-vision as possible.
Kitt Peak Geminids 2023
This composite image of the Geminid meteor shower was captured during the shower's peak at the Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory on December 14, 2023. The shower has a broad maximum so rates should be good for the remainder of the week. If you're totally clouded out you can "listen" to the Geminids at LiveMeteors.com.
KPNO/NOIRLab/NSF/AURA/R. Sparks (NSF’s NOIRLab)
Even in cold weather, meteor-watching is one of amateur astronomy's most relaxing activities. Having a friend or family member along will help pass the time and make it easier to forget the cold.
Unlike many meteor showers that originate from comets, the Geminids' parent is the 6-kilometer-wide asteroid 3200 Phaethon. With a perihelion distance of just 21 million kilometers, Phaethon's orbit brings it closer to the Sun than any other named asteroid — well inside Mercury's orbit. Surface temperatures can reach 750° C (1,390° F), hot enough to vaporize sodium from rock and create a comet-like tail of sodium atoms. Exactly where the meteor shower material originates remains a mystery, but it may be linked to a partial disruption of the asteroid through rapid rotation or another cause sometime in the last few thousand years.
When Earth crosses Phaethon's path every December, the debris strikes the atmosphere at 35 kilometers a second (78,000 miles an hour), heats up and etches glowing ionization trails many still call shooting stars. Check out the interactive graphic (above) where you can explore the Geminid stream from any angle by simply dragging and scrolling your mouse. Tap the Meteor Showers link in the lower right corner for a larger image and other options.
DESTINY+ mission
Japan's DESTINY+ is a science and technology demonstration mission that will conduct an in-situ analysis of Phaethon with the goal of understanding the source of the material behind the Geminid meteor shower. Right: Radar image of the asteroid by the former Arecibo Observatory.
Left: JAXA / ISAS Right: Arecibo Observatory / NASA / NSF
We'll soon learn more about the Geminids' parent when the Japanese DESTINY+ mission launches in 2028 and flies by Phaethon in 2030. Short for Demonstration and Experiment of Space Technology for INterplanetary voYage with Phaethon fLyby and dUst Science, the probe will will zip some 500 kilometers (310 miles) from Phaethon while analyzing its dust composition and mapping the surface with a multi-wavelength telescopic camera. As we seek answers to the Geminids' origin and evolution what better way to bide the time than to ease back for an hour under a frosty sky waiting for Phaethon to fling another fiery clue.