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Jupiter Is the Closest It's Been to Earth All Year - How to See It with a Small Telescope
Explaining the motion of the planets and how to see one for yourself!
Every night is a good night to look through a telescope (provided it’s not cloudy), but if you’re looking for an excuse, Jupiter is lining itself up for some candid closeups. At its farthest point, Jupiter is about 601 million miles away from Earth, but it gets as close as 365 million miles, depending on the position of the planets in their orbits.
On December 6, Earth will reach its closest approach with Jupiter this year, at a distance of 380 million miles. It’s the perfect opportunity for amateur astronomers to see the gas giant up close and personal, without having to hop an interstellar flight like the crew of SYFY's The Ark.
Why Jupiter (and the other planets) are sometimes closer or farther away from Earth
The Earth and Jupiter get closer and farther apart over time as a consequence of their orbits. Each planet travels around the Sun in a slightly squashed circle, and the duration of those orbits vary depending on their distance from the Sun. On Earth an orbit takes a year, but on Jupiter it takes almost 12. As the Earth runs laps around the Sun along its own orbital track, it laps or gets lapped by other planets, bringing us intermittently closer and farther apart.
When Jupiter is at its farthest distance of 601 million miles, light from its surface takes 54 minutes to reach us. During its closest approach, that time reduces to about 34 minutes. Another consequence of its relatively close cosmic proximity is that Jupiter looks about 50% larger during close approach than it does when we’re far apart. Every night leading up to December 6, Jupiter will get a little closer and a little larger in the sky, every night after it will get farther and smaller.
On December 7, just a day after closest approach, Jupiter will reach what’s known as opposition, a time when Jupiter (or any other planet) is directly opposite the Sun from our perspective. At the moment, the Earth will be threading a vast cosmic needle between Jupiter and the Sun. It not only means that we’re the closest we’ll be all year, but also that Jupiter rises as the Sun sets and is visible for most of the night.
Understanding the retrograde motion of planets
This same relationship between orbits also results in apparent retrograde motion of the planets. You’ve probably heard of planets being in retrograde from your horoscope, but it actually helped early astronomers understand the nature of the solar system.
When you look at the night sky, you’ll notice that everything moves east to west. That has less to do with the actual motion of the stars and planets and almost everything to do with the rotation of the Earth. The stars are in motion, of course, but they are so far away that their apparent motion is negligible. The planets, however, are much closer and their motion is more apparent.
If you pay close attention to the brightest spots in the sky, you’ll notice they move with respect to the background stars. That’s why the Greeks called them planets, which means “wanderers.” While they still move east to west over the course of a night, they mostly move west to east with respect to the background stars. That’s the direction all of the planets move around the Sun, but when they are in retrograde it looks like they are moving backward.
If you plotted Jupiter’s course at the same time every night over the course of year, you’d notice that it sometimes reverses course, zigzagging across the night. That weird motion helped early astronomers understand that the whole of the cosmos doesn’t revolve around the Earth, bolstering the heliocentric model of the solar system.
Understanding the apparent backward motion of planets is easier if we think of the Earth, Jupiter, and the rest as runners on a (mostly) circular track. Lately, Jupiter has been leading but Earth is catching up. After opposition, the Earth will pull ahead, courtesy of the orbital inside track. As we move around the track our orientation to the motion of the other planets changes and sometimes it looks like they’re running the wrong way.
How to see and take pictures of Jupiter with a small telescope
Jupiter is close enough and large enough that you can see it with any small telescope or even a pair of binoculars. Of course, the better your hardware, the better your result, but you can get breathtaking views with a telescope that is both affordable and user friendly. The OneSky telescope from Astronomers Without Borders (AWB), is a great entry-level telescope that provides views of the Moon, most of the planets, and some more distant objects like nebulae. And it won’t break the bank. They retail for about $250, which is about standard for a comparable device, but this one has some perks.
It features a 130-millimeter curved mirror at the bottom to collect light. The light is then focused and directed onto a smaller flat mirror positioned at a 45-degree angle. When the light hits that mirror, it’s bounced into the eyepiece. The whole thing only weighs 14 pounds, and it collapses so that it’s about half its normal length when not in use.
The OneSky is produced by Celestron, a trusted name in consumer telescopes, and they provide it to AWB at cost. The organization can then sell it at an ordinary retail price and use the proceeds to fund global S.T.E.A.M. and astronomy programs. Seeing Jupiter with the OneSky is as simple as extending the tube, dropping in an eyepiece, and pointing it in the right direction. Taking photos is a little more complicated.
If you want to get serious about astrophotography, there are dedicated astro cameras and computerized mounts that will keep your target in place even as the world turns. If you’re new to the hobby or you don’t want to drop a considerable investment, a smartphone, an adapter, and some patience can do the job.
The trick is getting your camera lined up directly down the eyepiece, which can be difficult, particularly when working with high magnification in the dark. Try a headlamp with red light, so you can see what you’re doing without losing the ability to see the stars. When taking pictures with your phone, it’s important to know that there are limitations; your photos aren’t going to rival Hubble, but you can improve your chances with a few simple tips.
When shooting in the dark, comparatively bright objects like Jupiter can get blown out (see above). You can minimize this by tapping on your target and dragging down the brightness, though you may lose background objects like moons and stars. You may be able to improve detail by increasing the exposure time and you should set a delay timer or use a remote shutter while you’re at it. Many an astro photo has been ruined by the jiggling of pressing the shutter.
Catch Seasons 1 and 2 of The Ark streaming now on Peacock!
