Thursday, September 30, 2010

Checking the weather

Last night, a tiny light blazed above our neighbour's rooftop, far brighter than Vega or Deneb. It couldn't be the ISS (which really whizzes past) , so I knew I was looking at Jupiter, currently a mere 368.8 million miles away. I can resist anything but temptation, so I finished my chores as quickly as possible, pulled a middling-sized Newtonian reflector out of my car boot and took aim at the heavens.

My luck was in, and my sighting tube was still calibrated; Jupiter appeared almost immediately in my field of view, and seconds later was focused perfectly. I could see the bright disk of the giant himself, and four bright points almost in a line - the 4 largest moons, 1 to the left and 3 to the right*. Knowing the moons to be only a little smaller than Earth, the vast scale of Jupiter was obvious. As I watched, I realised that I could a dark reddish band running across Jupiter's disc, some distance south of the equator.

Standing beneath the glowing windows of my home on a chilly autumnal night, it boggled my mind to be looking at alien weather. Of course, I've seen pictures of Jupiter many times, but somehow, this was much more real. Just think...
  • 70 minutes previously, the photons now hitting my eyes were leaving the roiling surface of our star
  • 30 minutes previously, those same photons bounced off freezing cloud-tops in the very toxic upper atmosphere of a truly enormous planet, and off towards a tiny blue speck...
  • ...where they whizzed down a plastic tube, bounced off two small curved mirrors, and into my eye.
How amazing is that?

* The informed reader, comparing my observations of cloud bands and moon positions with Jupiter's actual orientation might think I'm either observing while standing on my head or an Australian. Well, I'm innocent on both counts - a reflector telescope typically doesn't preserve up/down left/right.