On the evening of May 14, 2013, the waxing crescent moon shines close to Castor and Pollux, the two brightest stars in the constellation Gemini the Twins. On the opposite side of the moon is even a brighter star, Procyon. By the way, an imaginary line drawn from Procyon and right in between the Gemini stars takes you to Polaris, the North Star. It’s a very long jump across the heavens but the imaginary line will take you there. Try it tonight!
But the first thing you want to do at dusk is to look for the planets Jupiter and Venus in the west. Venus sets before nightfall and Jupiter sets around mid-evening. In contrast, the moon and Gemini stars stay out until late night, even flirting with the midnight hour.
People often refer to Castor and Pollux as “The Twins” but they aren’t really twins at all. At a distance of about 34 light-years, Pollux is the closest giant star to our solar system. It’s one of the very few giant stars in our galaxy known to have a planet.
Castor is farther away, at 52 light-years. It looks like a single star to the eye, but it’s actually six stars in one, all revolving around one another in an intricate dance.
With binoculars, you might be able to discern Castor and Pollux’s contrasting colors. Pollux looks orange, while Castor appears white. An orange star has a relatively low surface temperature, indicating that Pollux is in the autumn of its years. On the other hand, a more youthful star – like Castor – displays a white color, a sure sign of this star’s higher surface temperature.
Meanwhile, tonight’s moon is in a waxing crescent phase. It’ll continue to wax larger until the full moon on the night of May 24/25. Mark your calendar: the full moon will be visible all night long, from dusk until dawn.
When you’re finished looking at Castor and Pollux with binoculars, be sure to take a closer look at the moon. The interplay of light and shadow along the terminator – the shadow line dividing the lunar day and night – features the best three-dimensional views of the the lunar landscape. The terminator shows you where it’s sunrise on the waxing moon.
Tonight, use the moon to find the Gemini stars Castor and Pollux, and Procyon, the brightest star in the constellation Canis Minor!
Bottom line: On the evening of May 14, 2013, the waxing crescent moon shines close to Castor and Pollux, the two brightest stars in the constellation Gemini the Twins. Mark your calendar for the May 24/25 full moon.