December night sky
—Charlie Christmann
Thanks to a recent outbreak of solar activity, those with dark skies in rural New Mexico have had several opportunities to see the aurora borealis (northern lights), a rare treat this far south. Normally, only the northern tier of the United States, Alaska, and Canada are privileged to see auroras.
In late October the sun began to behave strangely. Three giant sunspots appeared on the surface of the Sun, each one larger than the planet Jupiter. On November 4, Sunspot 486 unleashed the most powerful flares ever recorded.
In New Mexico, our infrequent northern lights are usually dim, so dark skies are very important if we hope to see them. The best time to look is around midnight about two days after the report of an X-class flare. If we keep the skies dark by turning off outdoor lighting when not needed, we all may get the chance to see the auroras dance across our skies.
Top ten brightest stars—Part three
Finally, here are the final four brightest stars in the night sky.
- Number 4: Arcturus—Magnitude -0.04
This is the brightest star in the northern hemisphere. Known as the Bear Watcher, Arcturus follows Ursa Major, the Great Bear, around the north celestial pole. With a struggle between gravity and pressure in the latter part of its life, Arcturus has swelled to twenty-five times the Sun’s diameter. Eventually the outer envelope of Arcturus will be peeled away and the material ejected as a planetary nebula. Light from Arcturus believed to originate at the time of the previous Chicago World Fair—held forty years earlier, in 1893—was collected and used to activate a series of switches and officially open the 1933 World Fair in Chicago.
- Number 3: Alpha Centauri—Magnitude -0.27
Alpha Centauri is actually a system composed of three gravitationally bound stars. The two main stars are Alpha Centauri A and Alpha Centauri B. The tiniest star in the system is a red dwarf known as Alpha Centauri C. The Alpha Centauri system is a special one. At an average distance of 4.3 light-years, these stars are our nearest known neighbors in space beyond the solar system. Centauri A and B are remarkably Sun-like, with Centauri A being a near twin of the Sun. You are only able to see this bright star if you live further south than the latitude of Naples, Florida.
- Number 2: Canopus—Magnitude -0.72
Canopus resides in the constellation Carina, the Keel. This star is a true powerhouse. Its brilliance from our vantage point is due more to its great luminosity than its proximity. Though 316 light-years away, star number two on our list is 14,800 times the intrinsic luminosity of the Sun. Canopus is a yellow-white F super giant—a star with a temperature from ten to fourteen thousand degrees Fahrenheit—that has ceased hydrogen fusion and is now in the process of converting its core helium into carbon. Eventually, Canopus will become one of the largest white dwarfs in the galaxy and may just be massive enough to fuse its carbon, turning into a rare neon-oxygen white dwarf. These are rare because most white dwarfs have carbon-oxygen cores. This star is visible only south of the United States.
- Number 1: Sirius—Magnitude -1.42
All stars shine, but none do it like Sirius, the brightest star in the night sky. Aptly named, Sirius comes from the Greek word seirios, meaning searing or scorching. Sirius is best seen by northern hemisphere observers at a favorable time during the winter months. To find the Dog Star, use the constellation of Orion as a guide. Follow the three belt stars twenty degrees southeast to the brightest star in the sky. Your fist at arm's length covers about ten degrees of sky. Intrinsically, Sirius is twenty-three times more luminous and about twice the mass and diameter of the Sun. At a mere 8.5 light-years away, Sirius seems so bright in part because it is the fifth-closest star to the Sun.
The Leonids are not the only meteor show going. In fact, except for the past four years when the Leonids have raged with storm-level activity, the December Geminid meteor shower is typically a more active annual event.
And this year, the Geminid peak activity is forecast to occur, conveniently, on a weekend, at around 2:00 a.m. MST on Saturday, December 14. Moonlight will not be as much of a problem as with the Leonids. Cold weather could be your worst enemy. As many as two meteors per minute might be visible during the peak.
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