Arctic shower

Our traveling planet will reach the solstice on Sunday December 21. This is the point in Earth’s orbit where its north pole is most tilted away from the Sun, so that our northern hemisphere receives sunlight at the lowest angles and for the fewest hours.

Coincidentally, mainly in the night between December 21 and 22, Earth passes through a stream of dust that we see as the Ursid meteors.

My illustration of the December 21 evening sky scene is omitted here, because images are being blocked by some internet entity. So I’ve put it on Facebook, and you cam see it by clicking here:

You can see the Ursids coming into view, and the “anti-Sun” on the northernmost part of the ecliptic.

As described on page 137 of Astronomical Calendar 2025 and 2026, the particles were shed from periodic comet 8P Tuttle and roughly follow its orbit. Because of the angle at which this orbit intersects ours, the meteors’ radiant – the place in the sky from which they appear to dart out – is northerly; indeed it’s in the constellation, Ursa Minor, that contains our North Pole Star.

Latin’s ursa and Greek’s arktos are their words for the “bear,” that cuddly-coated but formidable beast, which is why we call Arctic the region of our planet under the circumpolar region of the sky where the two Ursa constellations revolve. It’s a pleasant, if cold, coincidence that the we are treated to the most Arctic of the yearly meteor showers at the most Arctic date in the year.

You could devote the longest night of the year to watching them, if you dress as sensibly as a polar bear. The Ursid shower is an interesting but not a major one: its ZHR or zenithal hourly rate is only 10 – the estimated number per hour that a single observer could count if sky conditions are good. And at this time of year the ZHR of the Ursids may be outnumbered by the ZHR of the snowflakes.

Come back inside and start getting warmed by Christmas cheer!