Astro Bob blog: Planets and moons highlight the weekendWhether you're up at dawn or out at dusk there are some cool planet goings-on to see. Update on Jupiter's fireball
By: Bob King, Duluth News Tribune
Planets and moons highlight the weekend
Jupiter and the moon pair up for an eyeful tomorrow (Sunday) morning at dawn. Maps created with Stellarium
No spots yet. That's the word from several Jupiter watchers who've been up at dawn looking for any after-effects of the fireball sighted earlier this week in the planet's cloud tops. I've seen no high resolution photos taken by large telescopes yet. An impact scar could be present but too small to show up in amateur scopes. It's also possible the little asteroid that made the fireball simply grazed the atmosphere and returned to space. Not to worry. Jupiter will have more surprises in store in the coming months. That's a guarantee.
See the planet for yourself tomorrow morning in close company with the last quarter moon. The two will be in conjunction at dawn and should make a lovely sight in the growing light. Small telescope owners will see three of Jupiter's four brightest moons shimmering alongside the bloated giant.The diagram at right will help you identify which moon is which. It depicts Jupiter as seen in most telescopes with the south direction up and west at left.
As you examine the moons, see if you can tell them apart by brightness. Ganymede is the biggest moon with a diameter of 3,268 miles (236 miles bigger than the planet Mercury!) and shines the brightest at magnitude 5.2. Callisto is the faintest of Jupiter's four bright inner moons with a magnitude of 6.4. Europa is brighter than Callisto even though it's over 1000 miles smaller, because its surface is composed of highly-reflective water ice. Io is hidden in Jupiter's shadow Sunday morning until after sunrise. That's why we'll only see three.
Mars has been approaching the bright star Regulus for weeks. Tonight and tomorrow they'll be closest together in the west during late twilight and early night.
Evening sky watchers needn't feel shortchanged. Mars and Regulus are less than a degree apart this evening and next. Look to the southwest in late twilight to spot them. Seeing two bright objects so close always sends a little tingle to my brain. It's special and worth a look. After Sunday, Mars departs from the star's vicinity as it heads for its next bright encounter with Saturn at the end of July.