A Bit of Summer in December
Even though December is upon us we still have some summer constellations residing in the western skies. Just like professional sports seasons, there's a lot of overlap with the constellation seasons. In fact, something called the "Summer Triangle" is still hanging in there in the western heavens.
The Summer Triangle itself is not a constellation, but is made up of three bright stars from three separate constellations. They're the brightest stars in the western sky and each is the brightest in their respective constellations. Deneb, the highest star in the west, is the brightest shiner in the constellation Cygnus the Swan. Within the stars of Cygnus is the famous and easy to see "Northern Cross" with Deneb at the top of the cross and the dimmer star Albireo at the foot. To make the cross into a swan, picture Deneb at the tail of the celestial swan and Alberio at the head. Then look for fainter stars beyond and above both ends of the crosspiece. The fainter stars, together with the three crosspiece stars, form an arc that makes up the wingspan of the swan. You can't help but notice that Cygnus the Swan appears to be making a swan dive toward the western horizon. That seems appropriate, since Cygnus will begin to disappear from the evening sky before the end of this month, setting before evening twilight as the Earth in its orbit turns away from the big heavenly bird.
In the southwestern sky, shining above Jupiter, is the Great Square of Pegasus, the torso of Pegasus the Winged Horse. Just to the northeast of the Square is the constellation Andromeda the Princess, with the Andromeda Galaxy just above the Princess. The Andromeda Galaxy is the next door neighbor to our Milky Way Galaxy. Our galactic neighbor isn't very close, though, at well over two million light years away, with just one light year equaling nearly six trillion miles. Despite that distance, you can just see the Andromeda Galaxy with the naked eye in the dark countryside as a fuzzy faint patch of light.
Gazing in the east after evening twilight, you'll be bombarded with all kinds of bright stars and constellations, especially later in the evening. You are witnessing the rising of the winter constellations, the best of the year in my opinion. The constellations Auriga the Chariot Driver and Taurus the Bull lead the charge. Just above Taurus is the best star cluster in the sky, known both as the Pleiades and the Seven Little Sisters. This is a young group of stars, 410 light years away, that looks like a tiny Big Dipper. After 8pm Orion the Hunter, the great centerpiece of the winter constellations, takes to the low eastern sky. The three stars in a row that make the belt of the great hunter will definitely jump out at you.
The brightest star in the east, however, is actually the planet Jupiter. By 8:30, if not sooner, you will see it on the rise in the low east-northeastern sky. Right now Jupiter is a little over 409 million miles away, but over the course of this month the largest planet of our solar system will come nearly 30 million miles closer. It will also take a very high arc across the sky through the overnight hours. Jupiter is a great prime telescope target, even for smaller scopes. For sure you can see up to four of its brighter moons, depending on where the moons are in their two to seventeen day orbits around the big planet. If skies are clear and steady enough, you may even see some of Jupiter's horizontal cloud bands. By the way, next week in Skywatch I'll have my annual holiday shopping guide for telescopes and other fun star watching goodies.
Comet Ison could put on show in early morning eastern sky and it may be bright enough to be seen with the naked eye. Since this is a new comet there's a lot of uncertainty about how bright it'll be or whether or how it'll hold together as it passes very close to the sun. If it holds together and is visible to the naked eye look for it in the very low eastern sky in the early morning twilight around 7am. Stay tuned!