The lunar eclipse early Tuesday morning will be the first total lunar eclipse to occur on the Winter solstice since 1638. The Winter solstice is the shortest day of the year in the Northern Hemisphere.
Columbus Ledger-Enquirer/ Philip Wartena/AP/File
The upcoming Dec. 21 full moon — besides distinguishing itself from the others in 2010 by undergoing a total lunar eclipse — will also take place on the same date as the solstice (the winter solstice if you live north of the equator, and the summer solstice if you live to the south).
Winter solstice is the shortest day of the year in the Northern Hemisphere and marks the official beginning of winter. The sun is at its lowest in our sky because the North Pole of our tilted planet is pointing away from it.
So, how often does the December full moon coincide with the solstice? To answer this question, let's use Universal Time (UT), also sometimes referred to as Greenwich Mean Time (GMT). We do this because in answering this question, it's important to define a specific time zone.
For example, if you live in Honolulu, this December's full moon does not fall on the date of the solstice. Hawaii Time runs 10 hours behind GMT and the full moon occurs on Dec. 20 at 10:13 p.m. local time, while the solstice comes the following day at 1:38 p.m. Alaska, too, will have the full moon and the solstice occur on these respective dates, but in a time zone one hour later than Hawaii.
Prior to this year, there were solstice full moons in 1999 (Dec. 22) and 1980 (Dec. 21).