Jove begins a new apparition with a redder Red Spot, pirouetting moons, and ever-changing cloudscapes. 

New Arrival
Jupiter adds extra sparkle to the eastern sky at mid-evening this month. Photo taken on February 20, 2016 around 10 p.m. The planet shines at magnitude –2.5 with a diameter of 44″. 
Bob King

I see a new face in the east now when I take the dog for her evening walk. Jupiter has returned, the first of the morning planet crew to transition to the p.m. side.

Although Jupiter reaches opposition on March 8th, when it'll be closest to Earth and brightest for the year, it's nearly as impressive right now. Watch for the planet to rise high enough for a sharp, clear view by 9:30-10 p.m.

We greet the biggest planet with new enthusiasm each year in part because its constantly changing and often unpredictable weather means surprises in the telescope. Will a cloud belt go missing? What color will the Great Red Spot (GRS) be this season? While no major belts have disappeared (so far) this winter, I have good news on the GRS front. Instead of the usual pink, pale orange or tan color we've seen so often in the past dozen years, the Spot really looks red.

Solids and Stripes
Jupiter on February 10 shows a host of detail including a red GRS set in a distinctive hollow, a two-component South Equatorial Belt, a necklace of white ovals in the South Temperate Belt and pale blue festoons in the planet's Equatorial Zone. South is up.
Anthony Wesley

I observed it several nights ago in my 10-inch reflector astride the planet's central meridian (CM), an imaginary line crossing from north to south that exactly bisects Jupiter's globe. Though the Spot has shrunk considerably in the past few decades, I'm thrilled to report that its color this season resembles a cherry sucker. Australian amateur Anthony Wesley, avid Jupiter watcher and discoverer of the 2009 Jupiter impact event, concurred in an e-mail exchange earlier this week:

"It's very red this year and makes a nice change from the very pale orange we had a few seasons ago which made it almost invisible at the eyepiece," wrote Wesley in an e-mail.

Find Your Way In The Clouds
The image used for this key was taken by the Hubble Space Telescope in January 2015. It shows the most prominent atmospheric features of the planet. Smaller scopes will show 2-4 belts separated by pale zones. Larger telescopes will reveal subtle texture inside the GRS, festoons, bar or rod-shaped clouds called barges and a low contrast, miniature version of the GRS, aptly named Red Spot Jr. White vortices or ovals show well in digital images but make for a visual challenge. North is up.

Jupiter has a lot to like. It's big, bright, and shows off at least two prominent cloud belts — the Northern and Southern Equatorial Belts — and four moons in even the smallest telescope. Larger scopes and higher magnification can tease out additional belts separated by pale "zones"; the Red Spot Hollow, a crisp indentation within the South Equatorial Belt; blue patches or clearings within the Equatorial Zone, also home to the plume-like festoons.

Much To See When The Air Allows
The turbulent region following the GRS makes for fascinating viewing when the seeing is good. Textural changes in the North Equatorial Belt throughout the coming apparition will also be apparent if you regularly observe the planet. January 12, 2016 photo. South is up.
Christopher Go

Occasionally one or more dark, elongated clouds called barges can appear strikingly red-colored or create the impression of a partial belt. Be on the watch for changes ... anywhere! The area following (east of) the Red Spot displays a curious "bubbly" texture, while Red Spot Jr., the result of the merger of three white ovals several years back, slowly drifts around the planet. In July 2006, it was "in conjunction" with the GRS; despite their proximity, both spots emerged unscathed.

Even at low power, Jupiter looks slightly oval. Its vast, gaseous globe is flattened by the planet's rapid rotation, which also causes its clouds to be drawn out in long, parallel stripes. Because sunlight illuminates the outer edge of the giant planet from a low angle, and we look through more of its atmosphere to see down to the cloud tops, Jupiter exhibits noticeable limb darkening.

Dancing the Night Away
Jupiter's four brightest moons are easy to spot in a small telescope, but don't expect to see all four all the time. One or more may be "hiding" in front or behind the planet or covered by its shadow.
Bob King

We can use this to our advantage when watching the four bright moons transit the planet. Io and Europa, being fairly reflective and small, often disappear from view when directly in front of Jupiter but stand out like tiny pearls against the dusky limb as they enter or exit the globe.

Watching shadows cast by the moons on Jupiter's cloudscape helps us to better picture the Jovian system in three dimensions with the Sun off to one side, the moons hovering above the planet, and their shadows projected below.

No two shadows are alike — Europa's looks only a little larger than a pinpoint; larger Ganymede as big as a pinhead. It's fun to imagine being in the shadow of a Jovian moon, watching a total eclipse of the Sun from the tops of Jupiter's blustery ammonia-ice clouds.

Jupiter With Two "Black Eyes"
Double shadow transit of Ganymede (top) and Io on January 3, 2013. Moons can cast shadows, undergo eclipses, and be occulted by the planet. 
Damian Peach

Moons also pass in and out of eclipse as they enter and exit Jupiter's shadow. If you plan your evening right, you can observe a bright moon slowly fade to invisibility as it undergoes an eclipse or magically reappear as it frees itself from Jove's shadow. Each of the four bright moons, Io, Europa, Ganymede, and Callisto, has a different period of revolution around the great planet, providing an endless supply of transits, eclipses, and just-plain-picturesque alignments.

Liftoff With a Lion
Jupiter shines in Leo near the border with Virgo. It's currently moving westward in retrograde motion.

Because Jupiter takes a similar path around the sky as the moon, every year we're treated to several fine conjunctions; the next occurs on the evening of February 23, when the two will be just over 2° apart.

You can get find out when to expect transits and eclipses at Sky & Telescope's Jupiter's Moons site. To get the best views of the Great Red Spot, you'll need to know when it transits the planet's central meridian. No problem. Check out the GRS Transits page.

We'll get you started with shadow transits for the remainder of this month and rarer double transits visible next month in North America during convenient viewing hours. Times shown below are CST or CDT. Add 1 hour for Eastern, subtract 1 hour for Mountain and 2 for Pacific:


* Feb. 18–19: Europa shadow transit 10:38 p.m. – 1:27 a.m.
* Feb. 20: Io shadow transit 8:12 – 10:28 p.m.
* Feb. 27–28: Io shadow transit 10:06 p.m. – 12:21 a.m.
* Feb. 29–March 1 – Leap Night: Relatively rare shadow transit of Callisto 9:08 p.m. – 12:16 a.m. Only one visible for North America during March. Of the four moons, Callisto lies farthest from Jupiter, so the shadow it casts falls much farther from the center of the planet than closer-in Io and Europa. Watch for it in Jupiter's north polar region.


Double shadow transits only with two shadows on the disk at the same time. Times are Central Daylight:

* March 14–15: Europa shadow transit 8:46 – 11:13 p.m.; Io shadow transit 9:22 – 11:37 p.m.
* March 21–22: Io shadow transit 11:15 p.m. – 1:31 a.m.; Europa shadow transit 11:23 p.m. – 2:11 a.m.
* March 29: Io shadow transit 1:10 – 3:25 a.m.; Europa shadow transit 2 – 4:47 a.m.

Great Red Spot transit times:

Feb. 17 (9:27 p.m.), 19 (11:05 p.m.), 22 (12:43 a.m. and 8:34 p.m.), 24 (10:12 p.m.), 26 (11:50 p.m.) and 27 (7:41 p.m.)


Image of Anthony Barreiro

Anthony Barreiro

February 17, 2016 at 7:13 pm

This past Sunday night, February 14, 2016, I was observing Jupiter through a 102 mm f/7 refractor, at magnifications up to 159x. I could see the Great Red Spot as a distinct little bump on the south equatorial belt, and the spot did seem redder than the belt. A light blue filter made the spot stand out a little more vividly. During recent years I had stopped bothering to keep track of the Great Red Spot, but when I read in S&T that the Red was back in the Great Red Spot, I decided to give it another try. It's always good to get a weather report!
Especially in a small telescope, the Great Red Spot will be most visible when it is in the middle of Jupiter's disk -- 30 or 45 minutes before and 30 or 45 minutes after transiting the meridian. Jupiter rotates once every 10 hours, so from one night to the next the GRS will transit the meridian about four hours earlier. The GRS will be well placed around the same time of the night about every five nights. Hope for clear, calm weather here on Earth, at least along your line of sight to Jupiter.

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Bob King

February 18, 2016 at 2:02 pm

Thanks Anthony for sharing your observing experience. Good commentary especially for someone with a small scope.

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February 23, 2016 at 1:08 am

I had a small star party at my house Saturday night. We had the pleasure of watching the transit of Io across the face of Jupiter the evening of Feb 20. At first we thought it might have been the GRS but a phone app soon corrected our mistake. Following it was fun, especially as it exited the planet and the gap reappeared.

Ed Anderson
Long Island, NY.

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Image of Anthony Barreiro

Anthony Barreiro

February 23, 2016 at 2:49 pm

How big was your telescope? What magnification were you using?

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Bob King

February 23, 2016 at 8:20 pm

Anthony - sorry to get back late. I typically use a 10-inch reflector. That's what I was using the night I made my observation of the GRS for the article.

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