Jupiter and its moons

This past Monday turned out to be a rather rare event for skywatchers: the planet Jupiter’s closest point of approach to the Earth since 1963! This was the coincidence of two situations. The first is the planet being in opposition to the Earth: the Earth was directly between the Sun and Jupiter, which not only makes it relatively close to us, but also results in the strongest illumination of the planet from our view. The second situation is perigee — the planet is as close to us as it ever gets. (I believe this coincides with the perihelion of the planet, i.e. its closest point of approach to the Sun in its elliptical orbit.)

I’ve been trying to get out more at night to appreciate these special events, and I went out late on Monday to try and snap a few photos with my 50x Canon digital camera. I in fact almost missed the event, as I had forgotten about it, but when I took out the trash late at night, Jupiter was unmissable in the sky! I ran in for my tripod and camera to try and get a few photos.

The last time I tried to photograph Jupiter was during the 2020 planetary conjunction, when Jupiter and Saturn were close together in the sky. The planets were much dimmer, and I failed to capture the moons of Jupiter in my photos, though I could see them clearly in the camera viewfinder. This time, I was much more successful!

The bright spot in the center is, of course, Jupiter, and the four dimmer dots around it are its four Galilean moons: Io, Europa, Ganymede, and Callisto. They are of course given the name “Galilean moons” because they were first observed by Galileo Galilei on January 7, 1610. They received their individual names from the German astronomer Simon Marius, who remarkably discovered the moons one day after Galileo, on January 8, 1610.

I endeavored to get a more detailed photo, and used the digital zoom on my camera to bring things a little closer.

I am not sure which moon is which, because I have no idea at which point any of them are in their orbits. Incidentally, the eclipses of these moons by Jupiter resulted in the first quantitative measurement of the speed of light, by Ole Christensen Römer and published in 1672. Römer had noticed that the eclipses of Jupiter’s moon Io happened more frequently when Earth is moving towards Jupiter, and less frequently when Earth is moving away from Jupiter. Römer correctly concluded that these changes arose because light takes a finite amount of time to reach us from Jupiter, and therefore the relative motion of the Earth and Jupiter changes the observed time of the eclipses.

A reproduction of an illustration from a 1676 news report about his discovery is shown below. I have always liked the smiley sun!

I am not a particularly good photographer, and my images are not particularly good when compared with what amateur astronomers have taken. But I love the fact that one can see, and photograph, another planet and its moons even with very little experience and a relatively inexpensive camera!

To close, let me note that as I write this, NASA’s Juno spacecraft is less than six hours away from its closest point of approach to Jupiter’s icy moon Europa, and it will come within 222 miles of the surface! Expect to see lots of remarkable images from NASA in the near future!

PS: I recently got my old telescope out of storage from Chicago. Assuming it isn’t damaged, I’ll hopefully have more detailed astronomy photos in the future.

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2 Responses to Jupiter and its moons

  1. > “Incidentally, the eclipses of these moons by Jupiter resulted in the first quantitative measurement of the speed of light, by Ole Christensen Römer and published in 1672.”

    I did not know that! Learn something new every day.

  2. Bradley Kjell says:

    Nice to see what can be done with an off-the-shelf camera!
    The photos people take with their 14″ reflector in the dark skies of Arizona are all very well, but nice to see something more approachable. Lucky that you took out the trash!

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