Tonight turn your left shoulder towards the North Star Polaris and you will be looking due east. The first thing that you will see–in fact, you can’t miss it–is a very bright, fat star about halfway up to the zenith. This is actually the giant planet Jupiter. Tonight three of its many satellites are visible with binoculars although often four can be seen. From left to right their names are Europa, Ganymede and Callisto. Io is in front of Jupiter at the moment, but will pop out from the glare later tonight on the right. As the days go by, the satellites constantly shuffle their positions. One thing that never changes is they always fall on a nearly straight line that also goes through Jupiter.
Just over two degrees to the left of Jupiter (a finger width at arm’s length) is the planet Uranus, a much fainter planet. Although just visible to the naked eye at a dark site, you will need binoculars to glimpse it if there is any light pollution at all. Uranus is not physically close to Jupiter but merely lies in nearly the same line of sight. It is, in fact, nearly a billion and a half miles further out than Jupiter, and no details can be discerned with binoculars other than its existence.
High in the east tonight (in fact, by midnight it will be directly overhead), is the asterism known as the Great Square of Pegasus. An asterism is a group of stars that form a noticeable pattern but is not necessarily a constellation. The square consists of four modestly bright stars, each side of the “square” is about 25 degrees wide. If you hold your hand at arm’s length and spread your thumb and pinky finger as far apart as they will go, that will cover about 25 degrees of sky – so the Great Square is a big asterism! One can use the Square to gauge the amount of light pollution at your viewing location. On a perfect night under a completely dark sky there are roughly 20 stars visible to the naked eye inside the Square. How many can you see? In Southwest Florida count yourself lucky to see five.
Off to the southeast, about 10 degrees closer to the horizon than Jupiter, is the star Fomalhaut. It’s the only bright star in an otherwise rather barren section of the sky. It’s interesting to note that it’s a rather close neighbor of our Sun – only about 25 light years off. Fomalhaut also is known to have at least one planet circling it; a possible goal for explorers of the distant future.
MichaelUsher is Vice President of the Everglades Astronomical Society, which meets every second Tuesday, at 7:00PM, at the Norris Center, Cambier Park, Naples.