Stars over Sisters

No unicorns inhabit the earth. But according to sky lore, there is one in the starry realm.

Monoceros the Unicorn is a faint wintertime constellation that lies due east of Orion. One would need a dark, clear night just to have a shot at finding it. It extends about 10 degrees north and south of the celestial equator.

While none of the stars in this constellation are bright, a few of them are of special interest. Beta Monocerotis is an impressive triple star system. When William Herschel discovered it in 1781, he remarked that it is "one of the most beautiful sights in the heavens." In a telescope these pale blue stars appear to form a curved line. The star system lies at a distance of about 700 light-years.

Plaskett's Star is a giant binary system that has a combined mass about 100 times greater than the sun. The two stars rotate around a common center of gravity in just over 14 days. It is about 5,245 light-years from the earth.

Several deep-sky objects are scattered throughout Monoceros, but the largest and most impressive is the Rosetta Nebula. Discovered independently in the early 1800s by comet hunters Lewis Swift and Edward Emerson Barnard, this object is a large, circular-shaped diffuse nebula where new stars are being born. It is roughly 130 light-years in diameter and lies at a distance of some 5,200 light-years.

After passing to within 43 million miles of the earth on January 7, and coming as close as 120 million miles of the sun on January 30, comet Lovejoy is heading back toward the outer reaches of the solar system. Though dimming, it should be easily visible in a pair of binoculars. The comet will lie very close to the star Almach in Andromeda on February 4, and graze the planetary nebula M76 in Perseus on February 20 before moving into Cassiopeia thereafter. A nearly full moon early in the month will interfere with efforts to locate the comet, but from about February 11 through February 20 a moonless evening sky will make the task much easier.

As the month progresses, Venus slowly climbs higher in the western sky while Mars sinks lower toward the horizon. On February 20 the two planets are joined by a thin crescent moon, creating a picturesque setting. Jupiter reaches opposition on February 6, meaning it will be positioned directly opposite the sun as viewed from the earth, and be visible all night long. Currently residing in Cancer, the giant planet is the brightest object in the night sky after the moon.

Speedy Mercury will hang out in Capricornus most of the month and become visible very low in the southeastern sky about 45 minutes before sunrise toward the end of February.

Saturn is in Scorpius this month, and by about 4 a.m. both it and the orange star Antares show prominently above the southeastern horizon.

The month begins with a brightening moon that becomes the Snow Full Moon (boy, what a misnomer this year in Central Oregon!) on February 3. Then the illumination of our only natural satellite begins to wane, reaching last quarter by February 11. The dimming continues until the moon goes dark on February 18. Past its new phase, the moon once again begins to wax, appearing half illuminated at first quarter on February 25.