In the Sky This Month

Today is Groundhog Day, which is a modern commemoration of a cross-quarter day. Such days come roughly half way between a solstice and an equinox. In many cultures, these dates represented the beginning of a season, not its mid-point.

Ceres, the largest member of the asteroid belt, is lining up opposite the Sun, so it is closest to Earth for the year, at more than 150 million miles. At that range it shines brightest, although not bright enough to see with the eye alone.

Orion climbs high across the south tonight. It’s marked by its three-star belt, with bright orange Betelgeuse to its upper left and blue-white Rigel to its lower right. And a giant stellar nursery lurks below the belt, known as the Orion Nebula.

The Moon will experience a spectrum of colors tonight. As the second full Moon of the month, it’s known as a Blue Moon. It won’t look blue, though. Instead, from most of the United States it will turn dark orange as it undergoes a total eclipse.

Castor, the fainter of the twins of Gemini, is about a third of the way up the eastern sky at nightfall, close to the upper left of Gemini’s brighter twin, Pollux. Tonight, the Moon will stand to the upper right of the twins.

The brightest star with a known planet climbs high across the sky on winter nights. Pollux is the brighter of the “twin” stars of Gemini. It is about a third of the way up the eastern sky as night falls, with the other twin, Castor, to its upper left.

Aldebaran, the brightest star of Taurus, stands to the lower left of the Moon at nightfall. Over the following few hours the Moon will move ever closer to the star. At their closest, they will be separated by less than the width of your finger at arm’s length.

Gemini is in the east at nightfall. The constellation is marked by its two brightest stars, Pollux and Castor, which represent Gemini’s twins.

The Northern Cross is in the west and northwest at nightfall. A star system near its center is home to the hottest planet yet discovered. Dayside temperatures on KELT-9b soar to 8,000 degrees Fahrenheit, which is hotter than most stars.

Look northeast in late evening for the Big Dipper. The handle points toward the horizon, with the bowl high in the sky. The second star from the end of the handle is Mizar. If you look carefully, you might see its faint companion, Alcor.