If you’re not one for staying up past midnight, or getting up before dawn, your best bet for catching the waning crescent moon and the brilliant planet Jupiter will come at dawn September 29. Look in your southern sky. Or if you live in the Southern Hemisphere, look in the northern sky. But don’t count on seeing much other than the moon and Jupiter, unless you wake up at least a good hour before sunrise.
You can also catch two planets at evening dusk after sunset. Look in the southwest sky for Venus and Saturn. People at more southerly latitudes (northwern tropics and Southern Hemisphere) can even catch the planet Mercury beneath Venus and Saturn at dusk and/or nightfall.
Back to the morning sky. For the next several mornings, before dawn, you can watch as the moon moves between the two morning planets, Jupiter and Mars. The moon is moving in an eastward direction – away from Jupiter and toward Mars. The moon paired up with Jupiter last night and will couple up with Mars in a day or two. If you’re up before dawn, you should easily see the Gemini twin stars, Castor and Pollux, in the vicinity of Jupiter. Although Castor and Pollux are respectfully bright stars, they pale next Jupiter. Still, you’ll enjoy picking them out. Castor and Pollux are noticeable on the sky’s dome for being bright and close together.
Castor and Pollux depict the heads of the mythological twins, the sons of Zeus and Leda. The two stars are similar in brightness, though Pollux is actually the brighter of the two. Castor is magnitude 1.58 and Pollux is magnitude 1.16. (The brighter a star, the lower its magnitude – aka apparent magnitude – value.) These two stars have been labeled as twins throughout history. The Arabs referred to them as the “two peacocks” and the Hindus as the “twin deities.”
The first-magnitude star Regulus sits fairly low in the eastern sky in the dark hour before dawn. By drawing an imaginary line from Jupiter through the star Regulus, you can imagine the ecliptic – the pathway of the planets – with the mind’s-eye. The sun, moon and planets travel in front of the zodiacal constellations, and always reside on or near the ecliptic – the Earth’s orbital plane projected onto the sphere of stars. Because the planets orbit the sun on nearly the same plane that Earth does, the ecliptic serves as a great reference for finding planets. Scan for Mars tomorrow morning about two to three finger-widths above Regulus, remembering to hold your hand at an arm length when making measurements on the sky’s dome. Mars appears fainter than the Gemini stars do but this world should be fairly easy to spot in the predawn sky. If not, try binoculars.
If you have binoculars, try your luck at spotting some of the celestial streetlights that line up along the great roadway of the ecliptic. Aim binoculars at Jupiter to see the faint star Wasat of the constellation Gemini right below Jupiter. During the upcoming week, watch for Jupiter to move to the other side of this star. Also, try locating the star Asellus and the Beehive star cluster of the constellation Cancer the Crab.
But let’s not forget about Castor and Pollux, whose moment of glory also comes in December. After all, these twin stars mark the radiant point of the December Geminid meteor shower, one of the finest showers of the year for the Northern Hemisphere.
If you’re up shortly before sunrise, look for the moon and Jupiter. If up before dawn, enjoy seeing Jupiter in front of the constellation Gemnini the Twins, Mars in front of the constellation Leo the Lion, and seek out the faint constellation Cancer the Crab between the two.