For the week ending January 1, 2011
Did you know that Uranus is a naked eye planet? You never see it on the list of naked eye planets. Uranus is almost as dim as something can be and still be visible to unaided human eyes.
It takes a dark sky. Just a little light makes Uranus a binocular object. A little more makes it vanish. For the lucky, there are hundreds of thousands of stars and a few other naked eye objects.
That’s why Uranus isn’t listed with naked eye planets. Nobody can learn all those naked eye objects and readily spot just one that changes position from night to night. Uranus went unnoticed for thousands of years. Even after astronomers had telescopes and took good notes, they mistook Uranus for just another dim star.
Something like that happened in 1612 and 1613 when Galileo observed Neptune. He was watching Jupiter, noting which stars were near it. Describing Jupiter’s motion, he also noticed that one particular star seemed to have moved. But he stayed with Jupiter and didn’t track the other moving dot. Modern methods now show that dot was Neptune. Galileo missed the chance to be Neptune’s discoverer and it circulated among the stars “undiscovered” until 1846.
Uranus was discovered in 1781, and there’s a similar story. Actually, there are lots of similar stories. Sky watchers jotted its position almost two dozen times before someone realized it’s not a star.
Now is a good time to spot Uranus for yourself. It starts the new year in close quarters with Jupiter. Jupiter’s easy to spot anyway. Point a telescope at Jupiter now and you’re half way to finding Uranus.
Northern hemisphere observers will find Jupiter in the south-southwest at sunset. It’ll move through the southwest to the west as the evening goes on. The big planet is below the Great Square of Pegasus. At low magnifications, you can see Jupiter and see Uranus in the same view.
Of course, there’ll be many other dim objects in the view. You can tell which is which with the help of free astronomy software. There are many programs out there. My favorite is Stellarium.
Don’t worry if you have binoculars but no telescope. The view will be nearly as good if you can make it hold still.
However you view Jupiter and Uranus, do it from night to night. Notice all the dim objects that aren’t moving so you can more easily tell the one that is. You’ll know the joy of positively identifying dim Uranus and you can imagine what fun it would have been to have discovered it yourself.
Things may be difficult while the moon passes nearby a week into the new year, but you may be able to track Uranus for a few more weeks as it pulls away from Jupiter.
Jupiter and Uranus ride into the sunset together during February. Some spring morning, you can try your luck at finding Uranus again without Jupiter being such a close and convenient starting point.