On this Day in Astronomy in 1610

Hello again fellow SkyWatchers.

Just an interesting astronomy history tidbit this time – On this day 399 years ago, January 13, 1610, Galileo Galilei discovered Ganymede, Jupiter’s largest moon and the largest moon in our solar system. 

Ganymede is 5268 kilometers (3273 miles ) in diameter, which makes it much larger than both Mercury (4880 km) or Pluto (2300 km), and huge compared to our Moon (3476 km). 

 

Steve Nipper

Manager of Planetarium & Senior Programs

January SkyWatch

Earth was at its closest point to the Sun (91,400,939 miles), which is called perihelion, in its orbit on Sunday, January 4th. We are actually closest to the Sun in the winter (for the northern hemisphere) and farthest from the Sun during the summer in July, called aphelion, on July 3rd this year, when Earth will be 94,505,048 miles from the Sun.

If you noticed the full Moon last Saturday night, January 10^th looked as impressive as the one in December, you were correct.  Just as the December full Moon was the largest and brightest of 2008, the January full Moon was the largest and brightest of 2009, and for the same reason – the Moon was full while it was at perigee, the closest point in its orbit to the Earth.

 

The bright standout in the evening sky right now after sunset is Venus.  This Thursday, January 14^th, Venus reaches is greatest angular distance East of the Sun, 47 degrees.  This means that it will be as high in the sky after sunset as it can get, so the next week or so will be a great time to admire the brilliant “evening star” (weather permitting, of course.) 

 

 

Steve Nipper

Manager of Planetarium & Senior Programs

New Year's Eve SkyWatch

New Year's Eve will present a striking view in the southwest after sunset.  The two brightest objects in our night sky, Venus and the crescent Moon will be in a beautiful close pairing.  If you have a clear view low in the sky and close to the horizon, you will also find Jupiter and Mercury side by side.  Mercury will be just to the left of Jupiter, much fainter and much harder to see in the fading twilight.

You'll have plenty of time to see the Moon and Venus, but you'll have to look very soon after sunset to see Jupiter and Mercury.

By the way, Neptune will be just to the lower right of Venus, and almost directly beneath the Moon, about twice as far from Venus as Venus is from the Moon.  Unfortunately, you won't be able to see Neptune without a telescope, and it is so far away that even in a telescope it looks like a faint blue, slightly swollen star.

As a bonus, at Midnight, Saturn will have risen and will be low near the horizon and due East below the constellation Leo the lion.

Happy New Year!  Be safe, have fun, and remember to go outside and look up.

-Steve Nipper, Manager of Planetarium