Evan Hazard, Northland Stargazing: Orion, perhaps the star of constellations
Orion is now well up after dusk in the east-sotheast. It is one of the most recognizable constellations, and Messier 42, the “Great Nebula” in Orion’s sword, angling below the three stars in his belt, is the nearest conspicuous star nursery, only some 1,345 light-years away. Orion’s bright stars are closer than M42.
The nebula is about 24 light-years across, and is actually a bright region on the surface of the much larger and mostly dark Orion molecular cloud. In recent decades, the cloud’s interior has been studied at infrared and longer wavelengths that penetrate the cloud’s dust. There is a neat Wikipedia entry at http://en.wikipedia.org/wiki/Orion_Nebula .
It’s December; dress extra warmly. Earliest sunset is Dec. 7. Latest sunrise will be in early January. I’ll have the date for you next month, from the “Skygazer’s Almanac 2013” in the January 2013 Sky & Telescope. Solstice is Dec. 21 in this time zone this year.
Mars is still visible low in the southwest, but is little more than a reddish speck. Jupiter dominates the evening sky. It is at opposition as December begins, rising about when Sol sets. It is therefore relatively close to us and at its brightest, particularly so since our orbits are as close as they get in Jupiter’s 12-year “year.”
The other naked-eye planets are morning objects. I see one of them, Venus, when I pick up the Pioneer from the front walk on clear mornings. For the others, get outdoors well before dawn. Saturn is up now around 4 a.m., and will rise about 2:30 a.m. on New Year’s. Mercury has an excellent apparition at December’s start and will be prominent for a week or so. Looking southeast an hour before sunrise on Dec. 1-11, Mercury, Venus above it, and Saturn above Venus are in a line pointing up and left toward Spica in Virgo. By Dec. 11, they are still in that line, but Mercury is getting low and will be lost in Sol’s glare before Christmas.
Full moon is Christmas Eve. Next day, in the evening sky, Luna will be only a degree below Jupiter. Luna actually occults Jupiter for parts of central South America and southern Africa.
The Geminid meteor shower will peak the night of Dec. 13-14, and this year moonlight will not spoil it. Again, remember to put on many layers.
December minima of Algol: 11:29 p.m., Dec. 8; 8:18 p.m. Dec. 11; 5:07 p.m. Dec. 14; and 1:13 a.m. Dec. 29.
EVAN HAZARD also writes “Threescore and Ten” for the Pioneer’s Prime Time.