Radiant (meteor shower) move along the comet's wake, and when the Earth moves through such debris, a meteor shower results. Because all of the debris is moving in roughly the same direction, the meteors which strike the atmosphere all "point" back to the direction of the comet's path. As an exception, the Geminids are a shower caused by the object 3200 Phaethon, which is thought to be a Palladian asteroid. The radiant is an important factor in observation. If the radiant point is at or below the horizon, then few if any meteors will be observed. This is because the atmosphere shields the
December Hydrids (December 4–15), and the Ursids (December 17-to December 25/26, peaking around December 22). "This list does not necessarily imply either official status or general observance." Last Week of November: November 25 – December 1 First Sunday: December 2 Fourth Sunday before Christmas Day: December 2 First Monday in December and following 7 days: December 3-9 First Friday: December 7 Sunday two weeks before Christmas: December 9 Second Monday: December 10 December 15, unless the date falls on a Sunday, then December 16: December 15 Second-final Sunday before Christmas Day: December 16 Thursday before Christmas: December 20 Winter Solstice: December