Tuesday, August 21 , 2018, 11:28 am | Overcast with Haze 70º


Dennis Mammana: Return of Jupiter Heralds Spring’s Arrival

See the return of Jupiter after dark this week. Click to view larger
See the return of Jupiter after dark this week. (Creators.com illustration)

What a great way to begin springtime. Jupiter is back in our night sky, and no one could be happier.

Oh, sure. Everyone talks about the stunning rings of Saturn, the glistening crescent of Venus or the ruddy red hue of Mars, but to me, Jupiter’s where it’s at. Fortunately for me and other Jupiter gazers, this planet reaches its opposition point on April 7, appearing opposite the sun in our sky.

In other words, as the sun sets in the southwest, Jupiter rises in the northeast and shines brightly in our sky all night long.

Opposition also means that the planet lies closest to Earth and, therefore, appears larger and brighter than at any other time in its orbit. So Jupiter, which is always impressive to view through a small telescope, will be especially impressive to view right now. In fact, it will be quite a sight for the next month or two.

Jupiter is always one of my favorites because it’s one of the few celestial bodies that actually seems to do something. Here’s a world that’s 11 times the diameter of Earth, yet it rotates on its axis once every 10 hours or so.

This means that its Earth-facing side changes completely in just five hours and, with patience, sky watchers with a small telescope can easily watch its pastel cloud bands and, sometimes, its Great Red Spot spin completely around in just one long evening of stargazing.

Equally amazing is knowing that Jupiter is made entirely of gas; there is absolutely no surface on which to stand. Astronauts trying to land on the planet would just sink deeper and deeper into its murky atmosphere until they became crushed beyond recognition by its tremendous weight.

Perhaps the most enjoyable part of watching this planet is keeping up with the antics of its four largest moons. These are known as the Galilean satellites — Io, Europa, Ganymede and Callisto — because it was the Italian astronomer Galileo who discovered them and their movements some four centuries ago.

These moons do-si-do around the Jovian disk from night to night, sometimes vanishing behind or slipping in front of Jupiter. Sometimes they even cast their shadows onto the giant planet’s cloud tops and provide endless entertainment for the backyard astronomer.

And sometimes, if two moons are passing each other, or approaching or receding from the planet’s disk, a sharp-eyed observer can see their movements in just a few minutes.

Much of the fun of watching these moons is knowing which is which. Click here to identify them by typing in the date and time to receive a graphic representation of their positions. Click here to learn more about these incredible moons and their amazing parent world.

Now that Jupiter’s back in our evening sky, try aiming your telescope in its direction, or contact your local astronomy club to learn when it will be hosting its next free star party, so you can get a close-up look at the exciting Giant Planet and its exciting family of moons.

It’s definitely going to be a fun springtime of Jupiter gazing!

Dennis Mammana is an astronomy writer, author, lecturer and photographer working from under the clear dark skies of the Anza-Borrego Desert in the San Diego County backcountry. Contact him at [email protected] and follow him on Twitter: @dennismammana. Click here to read previous columns. The opinions expressed are his own.

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