Tonight’s moon might look full to you. But the moon that shines on January 31, 2015 – appearing fairly close the constellation Gemini’s brightest stars, Castor and Pollux – isn’t astronomically full. In other words, it isn’t most opposite the sun on this date. Instead, the January 31 moon is a waxing gibbous moon. The moon will turn full during the evening hours on February 3, 2015 for us in North America (February 4 for Europe, Africa and Asia).
These bright Gemini stars outline the northeastern part of the Winter Circle.
By the way, that exceptionally brilliant star by the horizon at nightfall is really no star at all. It’s actually the dazzling planet Jupiter. Watch the moon descend toward this brilliant beauty of a planet as darkness falls over the new several days.
When the moon turns full on February 3, the full moon and Jupiter will accompany each other all night long.
After the first 10 days or so of February – after the moon drops out of the evening sky – look for Gemini to shine in all its starlit majesty.
You can also use the Big Dipper to locate the Gemini stars, Castor and Pollux. Draw an imaginary line diagonally through the bowl of the Big Dipper, as shown on the sky chart on the right.
Bottom line: On the night of January 31, 2015, let the full-looking waxing gibbous moon guide your eye to the bright Gemini stars, Castor and Pollux!