It’s another entry for the “In Galileo’s Shadow” column.
It’s now June 2019, and there’s a great opportunity for astronomers that are both occasional and experienced. Right now, the planet Jupiter is in “Opposition”, meaning that relative to Earth, it’s on the opposite side of Earth from the side that the Sun is closest.
This image shows exactly what is meant by this. This also means that a large part of Jupiter’s surface area is visible to Earth, which will make it for the immediate time the second brightest object in the night sky.
Jupiter is so well-seen in the cloudless sky right now that you can easily see it with a pair of binoculars. But it’s much easier to see it with something that’s tripod mounted.
In my case, my wife and kids bought me a small traveling telescope. The Celestron Travel Scope 70 was a great gift because it was smaller yet more powerful than my last scope (a garage-sale item that held up for a while).
WAITING FOR A CLEAR VIEW
I wanted to see Jupiter on June 10 (the date of Maximum Opposition), but clouds in the Phoenix area hindered this. But I took the time to do some research on Jupiter and what exactly I’d be looking at. Of great significance is that you not only can see Jupiter, but you can see are known as the “Galilean Moons“, namely Jupiter’s largest moons Ganymede, Callisto, Io, and Europa.
Galileo Galilei (1564-1642) helped to establish the argument that the Solar System is heliocentric, or Earth orbits the Sun (as do the other planets including Jupiter). With his telescope, he saw these 4 large moons rotating around Jupiter, hence they are called “the Galilean Moons”. All four of them were discovered or co-discovered by Galileo. The interaction of Jupiter and these four moons make for great case studies on geology, gravitation, and physics.
Some quick facts about the Galilean Moons (shown in size compared to Jupiter’s Great Red Spot):
Callisto (on the bottom) is Jupiter’s second largest moon, the third largest Solar System planetary moon (behind Saturn’s Titan), and almost the same size as planet Mercury.
Ganymede (second from the bottom) is Jupiter’s largest moon, the largest planetary moon in our Solar System, larger than Earth’s Moon (Luna), and is 8% larger than the planet Mercury.
Europa (bluish-brown, second from the top) is the smallest of the four Galilean Moons, the sixth largest Solar System planetary moon, possibly has an ocean made up of H2O (water), and the only known moon with an atmosphere (although very thin) made up of oxygen.
Io (yellow-orange, on top) which is the 3rd largest of the Galilean moons, the fourth largest Solar System planetary moon, the densest moon in the Solar System and, with over 400 active volcanoes, it is the most geologically active object in the Solar System.
I believe all four moons are fascinating but this time I was particularly fascinated by the “volcano moon” Io. The heavy yellow and orange colors come from the sulfur discharges from the moon’s volcanoes, and the numerous craters and pockmarks show eruption sites. Io’s volcanic activity comes from its extremely fast orbit (around Jupiter) of 42.5 Earth hours and the tidal pull of the gravity from the other Galilean moons Europa, Ganymede, and Callisto passing close by.
In this animation (with Callisto not pictured but outside of this image), Io is flexed and stretched in a similar fashion to taking a flexible metal rod and bending it back and forth which will heat the area that experiences constant motion/flexing. Io is shown in the orbit closest to Jupiter and spinning the fastest around the planet. Each time one of the other moons comes close, gravity from that passing moon stretches Io in the direction towards it while Jupiter’s constant gravity does the same in the opposite direction (like a flexing rod which leads to the frictional heating). This leads to explosively hot molten metal in Io’s core which is the source of it’s well-known explosive volcanic activity. Some of Io’s volcanic peaks are even taller than Earth’s Mount Everest!
I’m also interested in Europa, which has a very thin oxygen atmosphere and possibly an ocean of H2O water as well. I’ll definitely have to do more research on this and do another report once I get a larger telescope.
THE TELESCOPE SETUP
On June 12, the sky finally cleared up even with nearby smoke from wildfires in the Superstition Mountain region to the East. I practiced on the nearby half-moon just before evening (making sure that it did NOT face the sun).
The pictures here were on my phone so they don’t show the true clarity I saw. I played around with magnification settings, namely with a 20mm and 10mm eyepiece. To see Jupiter and it’s four Galilean Moons the closest I chose the 10mm.
I then queried the SkyGuide app (that I’ve used for the past 2 years) to see when and where Jupiter would rise during the evening hours. On June 12, it is positioned near constellations Libra and Scorpius, with the Moon to the upper right. Everything was ready later that evening . . .
GETTING A CLEAR VIEW
Around 8:30 PM Arizona time, I took a look. With the telescope, I could clearly make out Jupiter and it’s 4 prominent moons.
Without a larger scope, one of the easiest ways to determine which moon is which is through direct (and patient) observation. Io is the closest and fastest, and over one night show the greatest movement relative to Jupiter (with an orbit time of 42.5 hours around Jupiter). Europa would need more than 1 to 2 nights as it orbits Jupiter every 3.5 Earth Days. Ganymede and Callisto would be 3rd and 4th place respectively over a much longer nightly observation time. With a larger scope, the moons could be visibly discerned (which I hope to do sometime soon).
Even if you’ve missed the June 10th Jupiter-Max Opposition date, there should still be plenty of great opportunities to see Jupiter and it’s four largest moons throughout the rest of June 2019. As before, you could use a pair of binoculars, a small telescope similar to what it was he was here, or go down to an observatory that might be close to you.
For The Great Galactic Space Gimmick, I’m Gimmick Commander Ben Faltinowski. 🔭 ⭐️
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