The king of the planets, at least in our solar system, has made a grand entrance into our early summer skies, and will continue to dominate the early evening heavens well into October.
A couple of weeks ago, our Earth and Jupiter reached their closest approach to each other. Back then Jupiter was a little over 398 million miles away, but it’s still plenty close at just under 400 million miles.
It’s by far the largest planet in our solar system, with an equatorial diameter of 88,000 miles, dwarfing our Earth’s 7,900 miles. In fact, if Jupiter were a hollow sphere you could fill it with about 1,200 Earths!
Toward the end of evening twilight, Jupiter resembles a tremendously bright star rising in the low southeast sky. It’s available in our heavens all night long as it takes a low arc across the sky through the night. Jupiter is still really close to in what astronomers call opposition, which means the Earth is lying in the line between the sun and Jupiter. Because of that, Jupiter and the sun are at opposite ends of the sky. That’s where the term opposition comes from. Just like a full moon, Jupiter rises at sunset and sets at sunrise.
Jupiter is a wonder telescope target, but if possible, wait until it rises at least a little ways above the horizon, which unfortunately won’t be until after 11 p.m., at least for the next several weeks. When you’re viewing Jupiter, or anything else in your telescope, the higher the better. The higher in the heavens Jupiter is, the better the chance you’ll have to get a clearer image in your scope because Jupiter’s light doesn’t have to pierce through as much of Earth’s blurring atmosphere as it does when it’s close to the horizon.
Another thing that really helps when viewing anything through your telescope is to start with a low magnification eyepiece and work your way up to a higher magnification. You will reach a point of limiting higher magnification where the image will become too blurry or muddy. There’s no sense in seeing a blurry Jupiter, so bump down to a lower magnification.
Remember also that not all nights are the same for telescope viewing. Even if the skies are clear, high winds in the upper and lower atmosphere can diminish what you see and how much magnification you can obtain clearly. This is referred to as "bad seeing" conditions. If Jupiter doesn’t come in too clear one night, try it again the next night, or whenever.
One other thing — it’s always a good idea to look through your telescope at Jupiter or any other object for a continuous extended time. Try to keep your eye plugged to the eyepiece for at least 10 minutes at a time. That will give you more time to get used to the different light level and will allow you to see more detail.
Jupiter is basically a huge ball of hydrogen and helium gas, much like our sun. When you get Jupiter in the eyepiece of your telescope as it’s rising in the southeast, you’ll see at least some of its parallel cloud bands that will be oriented diagonally on the disk of the gargantuan planet. Even the smallest of scopes with decent focus can usually pick up two of the dark cloud bands running on either side of Jupiter’s equator.
But since Jupiter is so close this month, you might see more of them. You may even see some faint color in the bands. The clouds are mostly made up of ammonia and methane compounds. They swirl around Jupiter at speeds around 400 mph and contain eddies and storms within them. The biggest of Jupiter’s storms is the famous Red Spot, that’s way bigger than even our Earth. Other smaller red spots have also been seen on the great planet.
No matter how the seeing conditions are, you can easily see up to four of Jupiter’s largest moons. They look like little stars in a line on either side of the planet, depending on where they are in their individual orbits. You can easily spot them with even a pair of binoculars. There are many times when you can’t see all four of them because one or more may be behind Jupiter or masked in front of it. Even the tiniest of scopes and binoculars can pick them up.
Jupiter is so close to Earth right now that some eagle-eyed folks can see the moons with just their naked eyes. See if you can spot a very faint and very short tail on Jupiter. I’ll have much more on Jupiter’s Galilean moons next month.