Jupiter's moons

I’m still quite thrilled from the night-sky photography I managed tonight with my Olympus. I stepped outside just to have a look at the moon. With the full moon due next Tuesday, it was already about 93 percent illuminated, blazing away in the sky. Normally that kind of brightness, plus light pollution, would wipe out almost everything else, but there it was: a sharp point of light nearby that could only be Jupiter.

Getting a photo of it was another matter. I had to handhold the camera and drop the shutter speed to a risky one-fifth of a second. Most of the shots were a mess, either blurred or streaky beyond saving, and I was close to giving up. But one frame survived. When I pulled it up on the computer, I honestly couldn’t believe what I was seeing. It was better than anything I’d managed in all my previous attempts over the years. Sharp and without any streaky lines. I could clearly make out the four Galilean moons. A quick check online confirmed their positions relative to Jupiter, and that was the moment it really sank in.

Speaking of Jupiter, it turns out my timing couldn’t have been better. About 20 days ago, on the 10th of January, the Earth passed directly between the sun and Jupiter. That put the planet at what astronomers call opposition, when it sits opposite the sun in our sky and is at its best for observation. In fact, Jupiter was actually closest to Earth a day earlier, on the ninth of January, at a distance of about 633 million kilometres. At opposition it was shining away at magnitude –2.7, the fourth brightest object in the sky after the sun, moon and Venus. But with Venus tucked behind the sun in mid-January, Jupiter has effectively been the brightest starlike object in the night sky for weeks now, visible for much of the night. Given that Jupiter takes almost 12 Earth years to complete one orbit of the sun, this kind of alignment only comes around roughly every 13 months. The next one won’t be until 10 February 2027, which makes nights like this feel a bit more special.