With a single glance at Jupiter in the telescope, you will see what appears to be a mini solar system lined up around it. Come back again and again to discover what I personally think reveals the coolest secret Jupiter has to offer…
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I’ve taken tens-of-thousands of pictures of Jupiter over the years. The gas giant is the brightest object in the night sky after the Moon and sometimes Venus, and visible right after sunset for six months of every year.
While Saturn might be the prettiest object to look at in the night sky (sorry, Moon, I stand firm on this hill), Jupiter holds a secret that is only revealed when you come back to the telescope about two hours after you first look.
Some of your first thoughts might be, “The Great Red Spot!” Nope, though, when front-facing, you can see the little red splotch. But it’s very difficult for even me to see on a good night, let alone the middle of a city.
Jupiter is always accompanied by a group of other dots: the Galilean Moons, discovered by Galileo Galilei back in December 1609 when the famed astronomer turned the first “designed for stargazing” telescope skyward–equivalent to a cheap pair of binoculars today.
When you view Jupiter in the telescope, you’ll see them in some sort of line. If you come back the next day, the moons will have moved. And the next. And then next.
Each day brings a new sight. But we can go one step further!
I like to take a picture of Jupiter every 30-60 minutes. Not because it’s so cool that I need dozens of blurry pictures filling up every last byte of my phone’s storage, but because of its moons.
The Galilean Moons…move. Right before your very eyes. Waiting an hour between pictures shows this movement the most, but sometimes if they are close together, or directly beside Jupiter, you can see the moons moving on an hour-to-hour and sometimes even minute-to-minute basis.
Take, for example, the night of Saturday, January 10th: the motion of the moons was apparent to everyone to stopped at the telescope, thanks to a picture I took at 7:51pm showing the moons in a nearly straight line.
By 9:26pm, two of the moons were angled with each other, Io moving away from Jupiter, and Ganymede moving toward Jupiter.
And by 10:03pm, right before I stopped viewing for the night, the two moons were stacked on top of each other.
All of this motion is thanks to the angle of the moons relative to their lateral (sideways) position near Jupiter. Adding to that, the closer moons naturally orbit faster, and the farther moons orbit slower, so in general, you will notice the motions of Io and Europa in a shorter period than the motions of Ganymede and Callisto.
Several people returned to the telescope to view the changes for themselves, seeing in real-time how dynamic the solar system truly is.
Not every night will show large changes in position like this, particularly if all the moons are spread far to the sides, such as the red dots in my diagram above. On the other hand, nights where you can only see two or three of the moons, and then one or two begin poking out the edge of Jupiter’s disc are super cool, like playing peekaboo with a tiny dot that gradual sticks off the side, and then moves farther out to the side within 30-60 minutes.
The moons aren’t always lined up, either. Due to differences in their orbital tilts, you’ll often see them in different patterns that visually reflect these tilts. The image below shows one of my favorite arrangements from November 9th, 2024, where the moons appear in a box shape:
Earth reached its closest point to Jupiter for the year on Saturday, January 10th, so from here on out it will get smaller and smaller, decreasing in size by about 25% before it vanishes behind the Sun in late June. Make sure to come see it every night I’m hosting sidewalk astronomy wherever you are! After this cycle, it won’t return to the post-sunset night sky until the end of January in 2027. Check my tour dates to see where I’ll be while it’s visible, and make sure to book me for a private stargazing tour and explore the entire night sky from your own home, or our dark sky observing site in Sedona, Arizona.
Other planet visibilities: Find My Viewing Guide
- Saturn until early March (St. Pete city will block out the western views by the end of January, but it will be in the sky until early March no matter where you live)
- Jupiter until mid-June
- Venus from late February until October 2026
- Mars does not return to post-sunset night sky until February 17, 2027
- Mercury you need a clear low horizon to view, I almost never show it
- Uranus and Neptune are never visible to the naked eye; don’t fool yourself into thinking you can. It literally took mathematics for astronomers to discover Neptune after they noticed Uranus was didn’t orbit according to their original calculations
The next cycle of our own Moon, viewed through my telescope in St. Pete, will be from January 23rd – February 3rd. I will NOT be out on Saturday January 30th due to a private event in Parrish, Florida scheduled for that night.
This world is beautiful.
Alex
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