NASA / JPL-Caltech / SSI

NASA's Cassini orbiter captured this view of Saturn on June 15, from a distance of about 1.8 million miles (2.9 million kilometers). The rings' shadow runs across the planet's sunlit side. The speck in the lower left corner is Enceladus, a 313-mile-wide (504-kilometer-wide) moon of Saturn.

NASA's Cassini sent back this big, beautiful, black-and-white picture of Saturn — but what's that little white speck in the corner?

The image, unveiled by Cassini's imaging team on Monday, shows tiny Enceladus at lower left. It's just 313 miles wide (504 kilometers wide), and yet it shines brightly from a distance of 2 million miles or so. Enceladus is arguably as intriguing as Saturn, and here's why: The icy moon has geysers of water spouting up from cracks in its surface, suggesting that there's a deep ocean and perhaps even some sort of life down below.

To get a more imaginative view of Enceladus, check out this posting on the io9 blog, featuring an illustration from "Planetfall: New Solar System Visions," a big, beautiful, full-color coffee-table book by Michael Benson. NPR's Robert Krulwich showed off the same image earlier this month on his Krulwich Wonders blog.

Enceladus is just one of the moons of the solar system that's been soaking up the spotlight lately: Also this month, NASA's Curiosity rover watched Mars' two moons, Phobos and Deimos, pass over the sun's disk during a series of mini-eclipses. The rover won't see such a sight again for 11 months or so. Here's a smooth animation of Deimos' transit from Nahum Chazarra on UnmannedSpaceflight.com. And if you haven't seen it already, you'll want to catch up with the sight of a crescent Phobos in Mars' dusky sky. 

Shine on, Harvest Moon
Our own moon is definitely worth watching over the next few days: Saturday brings a "Harvest Moon" — that is, the full moon that's closest to the September equinox. That's traditionally a good moon to bring in the harvest by, since it lights up the whole night for late-working farmers.

The Harvest Moon also can serve as a guidepost for finding the planet Uranus in the night sky, although the moon's glare interferes with the view this weekend. If you'd like some extra help, the Slooh Space Camera is planning a couple of online viewing parties over the weekend — with Uranus as the guest of honor. Video feeds will be coming in to the Slooh website from a variety of observatories, and a panel of experts will provide commentary. The first show begins at 7 p.m. ET on Saturday, with an encore performance at 10.

Next week, the moon continues to act as a guide, as Sky & Telescope's Alan M. MacRobert explains. On Oct. 3, the moon lingers near the Pleiades star cluster. The next night, it sits near the bright red star Aldebaran in the constellation Taurus. And on Oct. 5, the waning moon hangs out with Jupiter, starting around 10 p.m.

This weekend is also a good time to look for the International Space Station as well as the European Space Agency's Automated Transfer Vehicle, which undocked from the station today. To find out when and where to look, check out NASA's satellite sighting database.

Where in the Cosmos
Cassini's picture of Saturn and Enceladus served as today's "Where in the Cosmos" picture puzzle on the Cosmic Log Facebook page. It took just a few minutes for Ian Slota to solve the riddle and report that the speck in the picture was Enceladus. As a reward, I'm sending Ian a pair of big, beautiful, cardboard 3-D glasses, courtesy of Microsoft Research's WorldWide Telescope project. Those glasses will come in handy for seeing 3-D pictures of Saturn's moons. Click the "like" button for the Cosmic Log Facebook page, and you too may be a winner in next week's "Where in the Cosmos" game.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ circles. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter. You can also check out "The Case for Pluto," my book about the dwarf planet and the search for new worlds.

Laurent Lamy

These composite images show Uranian auroras as bright spots on the planet's disk on Nov 16, 2011 (left), and on Nov. 29 (right). The images from the Hubble Space Telescope have been processed to bring out details in Uranus' faint ring system.

Thanks to the Hubble Space Telescope, astronomers have caught a rare display of auroras on Uranus, which ranks among the solar system's oddest planets.

Unlike the beautiful, rippling curtains of greenish light we've been seeing in earthly skies over the past few months, the Uranian auroras are short-lived bright spots sitting on top of the ice giant's bluish cloud tops. But they're caused by a similar mechanism, involving the interaction of electrically charged particles with atoms and ions in the planet's upper atmosphere.

NASA's Voyager 2 probe picked up the first evidence of Uranus' auroras in 1986. "Since then, we've had no opportunities to get new observations of this very unusual magnetosphere," Laurent Lamy, an astronomer at the Observatoire de Paris, said today in a news release. There have been a few hints of auroral observations, but Hubble's views from last November rank as the best views yet. Lamy and his colleagues provide the details in a paper published by Geophysical Research Letters.

The team took advantage of a lucky break and a favorable planetary alignment: Last year, Earth, Jupiter and Uranus were lined up so that energetic solar emissions could flow past each planet in turn. When the sun produced several outbursts in September, the astronomers timed the flow of the particle storm past Earth a couple of days later, and then detected the flow past Jupiter two weeks after that. On the basis of those readings, they calculated that the outburst would reach Uranus in mid-November, and scrambled to schedule observing time on the Hubble Space Telescope.

Uranus is an oddity because it basically rotates on its side as it orbits the sun. The orientation of its magnetosphere is tilted 60 degrees with respect to its rotational axis. As a result, during the current season, each of the planet's magnetic poles turns to face the sun in the course of a Uranian day. "This configuration is unique in the solar system," Lamy said.

Hubble was well-placed to catch the auroral flashes on the sunlit side, near Uranus' north magnetic pole. Each flash appeared to last only a couple of minutes, the astronomers said.

These new findings solidify Uranus' place on the list of planets flashing with auroral lights. Jupiter and Saturn are also on the list. Mars is thought to be capable of localized auroral effects, even though it doesn't have a global magnetic field. (In fact, some observers suspect we saw evidence of those effects last month.) Earlier this month, astronomers reported seeing auroral-type activity on Venus as well.

Lights on Earth
And then there's Earth. Last October, a solar outburst sparked northern lights that could be seen as far south as the state of Mississippi, and over the past month, higher-latitude residents have been treated to almost as many fireworks displays as Disneyland tourists typically get to see. Although the approach of summer is starting to cut down on the opportunities to see auroras in the Northern Hemisphere, some folks got great views as recently as last night. Here are a few of the highlights:

Shawn Malone of Marquette, Mich., snapped pictures of the aurora from the shores of Lake Superior. "The sky was ablaze in light," Malone told SpaceWeather.com. "Northern lights were so bright they lit up the beach!" For more from Malone, check out LakeSuperiorPhoto.com and his Vimeo video gallery.

Brian Larmay

Here's a different angle on the aurora and the International Space Station, captured by Brian Larmay of Beecher, Wis. The long streak in this time-lapse photograph is the space station, sailing across the sky. To see more of Larmay's pictures, check out his SmugMug gallery.

'Where in the Cosmos'
Today's picture of auroral displays on Uranus served as this week's "Where in the Cosmos" picture puzzle on the Cosmic Log Facebook page. It took only a couple of minutes for Shirley Beningo to blurt out which celestial body was shown in the picture, and what the bright spots were. To reward her for her quick cosmic vision, I'm sending her a pair of cardboard 3-D glasses, wrapped up in a 3-D picture of yours truly. Ashley Nicole and Gerry Marien came in as the runners-up, and are eligible for 3-D glasses as well. Be sure to click the "like" button on the Cosmic Log Facebook page so you're ready for next Friday's "Where in the Cosmos" contest.

Earlier stories of auroral glories:

• Farewell to the northern lights
• Northern lights make for must-see TV
• Southern exposure for auroral lights
• Sky lights go wild, north and south
• Solar storm lights up northern skies
• Slideshow: The best of the northern lights
• Cosmic Log's auroral archive

In addition to Lamy, the authors of "Earth-Based Detection of Uranus' Aurorae" include R. Prange, K.C. Hansen, J.T. Clarke, P. Zarka, B. Cecconi, J. Aboudarham, N. Andre, G. Branduardi-Raymont, R. Gladstone, M. Barthelemy, N. Achilleos, P. Guio, M.K. Dougherty, H. Melin, S.W.H. Cowley, T.S. Stallard, J.D. Nichols and G. Ballester.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto,"my book about the controversial dwarf planet and the search for other worlds.