The name of Anthony Wesley, an amateur astronomer from Australia, often comes up in this blog because of his remarkable discoveries of two meteoroid impacts on Jupiter over the past two years. He also takes some of the best pictures of the planet. One of his most recent, made on August 30, when the atmosphere was exceptionally calm, show details that compare well with images made by the Hubble Space Telescope.
It’s rare when the air is calm at both ground level and high up in the atmosphere. To see fine details on a planet, you need high magnification. On most nights, even the seemingly serene ones, the air higher up is roiling and shifting about enough to degrade telescopic images. Everything looks OK at low power, but jump up to 150x – 200x for a better look, and you’ll often discover your image turns to mush. You’re not just magnifying the object, you’ll also magnifying turbulence a couple hundred times. On unsteady nights, planets and stars range from looking a little fuzzy to fluttering around like clothes on a laundry line. I’m not kidding – it can get that bad.
Wesley was granted a rare window of calm and took advantage of it by making a beautiful photograph, certainly one of the best ever taken by an amateur. Having experienced a few serene and steady nights in my life, I can imagine the impression Jupiter must have made. With no flutter, planets and the moon look like the real things, not images – you literally feel like you’ve left the Earth and are now OUT THERE. Details you never imagined you’d see in your lifetime are staring you right in your face. Disbelief is a common feeling shared by many amateur astronomers during these infrequent and splendid moments.
Yesterday we looked at Jupiter and how you could use the planet to guide you to the constellation Pegasus and the Great Square asterism. Over the next couple weeks, we can use it again to find the planet Uranus. Some of you may recall that Jupiter was near fainter Neptune last year when the pair was in Capricornus the Sea Goat. Jupiter, closer to the sun than Neptune and moving more quickly in its orbit, has traveled on, leaving the 8th planet to fend for itself. Jupiter’s new companion is Uranus, another one of our solar system’s large, gaseous planets similar in many ways to Neptune.
Uranus was discovered by William Herschel in 1781 from his backyard garden in England. At the time he interpreted the tiny disk he saw as a comet. Not long after, astronomers determined it was a planet, the first new one identified since antiquity. Uranus is four times the size of Earth, orbits 1.8 billion miles from the sun and is swaddled in a thick atmosphere of mostly hydrogen and helium where the winds can blow up to 560 mph. Check out that robin’s egg blue color. It’s caused by methane gas which absorbs the red light from sunlight and reflects the blue back.
Like Jupiter, Saturn and Neptune, Uranus has no surface to stand on. Beneath the atmosphere, the planet’s interior is filled with a mush of slushy water and ammonia ices. One of the planet’s most delightful peculiarities is the tip of its axis. Our planet’s tip is 23.5 degrees, enough to give us the joy of four seasons, but Uranus is tipped 98 degrees, meaning it axis is nearly parallel with its orbit. The dang planet is spinning sideways with its polar axes sticking out left and right and equator belly up. Scientists suspect a large impact long ago may have knocked it out of kilter.
Since Uranus is 6th magnitude or comparable to the faintest stars visible from a dark sky, only the keenest-eyed will see it without optical aid. Thankfully, it’s plenty bright and easy to see in binoculars. Use the map above to find it, and if you keep watch in the next few weeks, you’ll see the whirrings of the solar system as faster-moving Jupiter passes right under the other blue planet. While you’re taking in the scene, don’t forget to watch for the nightly “moon ballet” of Jupiter’s four brightest satellites.