Ursids and GEMINIDS
WHEN: Nights of 12-15 December for the Geminids, 22/23 December for the Ursids
The Geminid meteor shower reaches peak activity on the night of 13/14 December. Assuming the weather is kind, on the night of the peak, the Moon will appear as a 14%-lit waning crescent, rising above the eastsoutheast horizon around 04:00 UT on 14 December. Astronomical twilight begins around 05:20 UT, marking the end of true darkness. Consequently, even when it has climbed appreciably above the horizon, that slender crescent Moon is not going to interfere much at all.
The Geminids have a zenithal hourly rate (ZHR) of around 120 meteors per hour. This is a normalised rate used to assess true activity. The visual rate varies according to conditions, but it’s realistic to expect between 35-55 meteors per hour under skies with a limiting magnitude of +6.0 to +6.5. For less perfect skies with a limiting magnitude of +5.0 to +5.5, the
expected visual rate drop to around 14-22 meteors per hour. It pays to get somewhere as dark as possible for the best show.
The shower is expected to peak at 06:30 UT on the morning of 14 December but in contrast to the sharp Perseid peak in August which lasts just a few hours, the Geminid peak is broad, lasting for around a day.
A day ahead of the peak, the shower tends to show a good number of faint
meteors. Don’t be fooled though, because this is just a taster for the main event. A clear peak night display of the Geminids can be pretty spectacular, often with many bright events streaking across the winter sky. The meteoroids that cause the shower have an entry speed of 35km/h, making makes them ideal photographic targets.
The Geminids are active from 4-17 December. For a trail to qualify as a Geminid it must appear to come from the shower radiant; the chart above shows where this is located. If a meteor isn’t coming from the radiant, it isn’t a Geminid.
Geminids appear when Earth passes through debris distributed around the orbit of asteroid 3200 Phaethon. This month we get a rare chance to see Phaethon as well, as it passes relatively close to Earth. Check page 59 for further information on how to see it through a small telescope.
The Ursid meteor shower continues directly after the Geminids, with activity from 17-26 December. The ZHR for this shower is much lower, at just 10 meteors per hour, but again the Moon will be out of the way, leading to excellent dark skies. Peak activity occurs on the night of 22/23 December from a radiant position close to mag. +2.1 Kochab (Beta (`) Ursae Minoris).