Uranus (and moons!) in motion

I had so much fun creating the Pluto animation that I decided to track Uranus across the sky from the telescope in the Canary Islands. I was excited to see two and sometimes three of Uranus' moons swarming around the planet (click the image to see the larger version.) The animation above shows July 24, 2015 - August 5, 2015 (I missed July 25 and 28, so there are 11 frames).

There are two interesting and unplanned aspects of this animation.

First, I caught Uranus going retrograde. The animation begins on July 24. The next frame is July 26. This was the day that Uranus appeared stationary in the sky because our orbit around the sun is much faster than Uranus, which takes about 84 Earth years to complete one orbit. When our orbit overtakes, or "laps," Uranus in the race around the sun, we see Uranus in our rearview mirror and it appears to move backwards. This is called retrograde. So, in the animation, you can see Uranus moving toward the left at the very beginning, then pause for a moment before moving toward the right. Had I planned this better, I could've gotten more frames before July 24, but now I know better.

Second, those moons! Uranus is 1.7 billion miles away from Earth (maybe further, depending on where we both are in our orbits). Uranus has 4 large moons and a bunch of really small ones for a total of 27. The large moons are Oberon, Titania, Ariel, and Umbriel. They range in size from about 4,926 km (3060 miles) to about 3673 km (2282 miles). That's about the distance from Los Angeles to New York. And you can see them from so far away. Amazing.

On a side note, you may notice that the last two frames have some light distortion. That's the light from the Moon. Today (Aug 5, 2015), Uranus will be only 1° north of the Moon. Still in Waning Gibbous phase, Uranus will probably be washed out in the glare of the Moon. Even so, when you look up at the Moon today, remember that you are also looking at Uranus and those moons over a billion miles away.

Adam BrownComment