Twin stars from different fathers play key role in February night sky

Posted Jan. 31, 2010, at 6:04 p.m.

Prominent in the winter sky are the stars Castor and Pollux of the constellation of Gemini, the Twins. In Greek mythology, the mother of both was Leda, but Pollux was fathered by the god Zeus and was immortal while Castor’s father was the Spartan king Tyndareus and was mortal. When Castor died, Pollux begged Zeus to al-low him to share his immortality with his brother and Zeus placed them together in the sky forever as the constellation Gemini. Pollux is a first-magnitude star while Castor is dimmer at second-magnitude; however, Castor is the more interesting of the two. Castor is a visual binary with both components being spectroscopic bina-ries, making the “star” a quadruple system. Some references associate a faint third binary with the other two, making Castor a sextuple system in all. Pollux does have its own claim to fame in that a planet, roughly three times the size of Jupiter, orbits it. Allen, in his book “Star Names,” says the legend of the Twins stretches far back into antiquity long predating Greek mythology.

Focus on the planets

Mercury rises low on the southeastern horizon about a half-hour before sunrise. Look for Mercury on the 12th of the month when the thin crescent moon is to its immediate upper right.

Venus is essentially lost in the glare of the sun, although it possibly may be spotted near Jupiter by midmonth.

Mars shines brightly in the east at twilight beneath the twin stars of Castor and Pollux. Mars will gradually fade as Earth pulls away from the Red Planet as they orbit the sun.

Jupiter is well up in the southwest about 45 minutes after sunset as February opens but dips toward the horizon and is lost by month’s end. On Feb. 16, look for Jupiter and Venus less than a degree apart on the southwestern horizon.

Saturn rises in the east around 9:30 p.m. at the start of the month and two hours earlier by month’s end. Saturn’s fabled ring system continues to narrow.

Uranus is very hard to spot as it sinks into the evening twilight, while Neptune is lost to sight behind the sun.

February events

1 Sunrise, 6:55 a.m.; sunset, 4:43 p.m.

2 Candlemas or Groundhog Day, a cross-quarter day marking the midpoint between the winter solstice and the spring equinox.

5 Moon in last quarter, 6:50 p.m.

8 Peak night for the Alpha Centaurid meteor shower. Average of about six an hour although displays of up to 25 an hour have been known, and the moon will pose little problem.

11 Look for Mercury low in the southeast about a half-hour before sunrise with the thin crescent moon to its upper right.

13 The moon is at apogee and at its farthest distance from Earth for the year.

14 New moon, 9:52 p.m. Happy Valentine’s Day! Jupiter, Venus and the barely discernable new moon are grouped together on the southwest horizon about 15 minutes after sunset.

16 The sun enters Aquarius on the ecliptic. Also the start of Mardi Gras, or “Fat Tuesday,” when all “sinful” foods were used up before Lent. Venus and Jupiter are separated by less than one degree in the southwest after sunset.

18 The sun enters the astrological sign of Pisces but, astronomically, has only just entered Aquarius.

22 Moon in first quarter, 7:42 p.m.

25 Mars is closely situated to the upper left of the moon in the southeast around 9 p.m. Castor and Pollux are directly above the pair.

27 Moon at perigee, or closest approach to Earth. With the full moon less than a day away, astronomical high tides are likely.

28 Full moon, 11:37 a.m. The full moon of February is known as the Hunger Moon or Snow Moon. Sunrise, 6:15 a.m.; sunset, 5:22 p.m.

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