Skywatch: There’s a giant on the rise

Since this past September, Saturn’s been the best planet to enjoy through even a small telescope, even though its ring system still appears nearly on edge from our vantage on Earth currently. There’s a new sheriff in the night sky though, Saturn’s big brother Jupiter, the king of the planets, on the rise in the eastern heavens along with Orion and the rest of the great winter constellations. Jupiter is by far the largest planet in our solar system, 88,000 miles in diameter. Jupiter’s so enormous that if it were hollow about 1,000 Earths would fit inside it.

Without a doubt, Jupiter’s the brightest “star” in the night sky right now. Jupiter’s especially bright now because Earth and Jupiter are the closest they’ll get to each other this year, about 395 million miles. That’s because Earth and Jupiter are in an alignment astronomers call opposition. Earth is nearly in a direct line between the sun and Jupiter. something astronomers call opposition. This is a great time for Jupiter gazing, not only because the great planet is close to us but also because it’s available all night long. Just like a full moon, Jupiter rises at sunset and sets at sunrise. And there’s more great news! Jupiter will dominate the night sky well into this coming spring.

Jupiter, like Saturn, is a wonderful telescope target, even if you have a small scope. It’s basically a tremendously large ball of mostly hydrogen and helium gas, over 300 times more massive than Earth. In fact, Jupiter is twice as massive as all of the other planets combined. Like the rest of the gas giants in the outer solar system, it doesn’t have a solid surface but is thought to have a rocky core about 10 to 15 times the mass of the Earth. Because of its colossal mass, Jupiter has a very strong gravitational field, so strong that even if the planet had a surface to stand on, you wouldn’t be standing there long. The gravity of Jupiter would break you down to a pile of flesh and broken bones very quickly.

Jupiter’s gravity also causes the giant planet to produce energy. Jupiter’s interior gases are constantly being gravitationally compressed, which produces heat that oozes out of the planet. In fact, Jupiter produces over one and a half times the energy that it receives from the sun, mostly as infrared radiation. That heat drives the atmospheric winds hundreds of miles an hour.

Jupiter’s atmosphere is made up of complex bands of wind-driven clouds mainly made up of methane, ammonia, and other gases. The different colors are the result of gases being at different temperatures and densities, as well as ultraviolet radiation from the sun. There are also several storms on Jupiter like the “Great Red Spot”, a storm that’s been raging for over 300 years! It’s been shrinking very gradually over the years but is still larger than the diameter of our Earth.

Through even a small telescope, you can see at least some of these cloud bands, especially two darker ones on either side of Jupiter’s equator. If your scope is larger, you might even see the famous Red Spot but we only see it about half the time since Jupiter rotates on its axis just like the Earth but much faster, taking only just under ten hours to make one rotation. So, about every five hours, the Great Red Spot is facing our way. The absolute best time to spot it though is when it’s on the meridian, near the middle of Jupiter’s giant disk. Even then, it can be really tricky because, honestly, it’s not all that red. Most of the time it’s somewhere between light pink and salmon colored.  Apps like Sky Guide can help you keep up with the Red Spot’s position and when it’s due to be on the meridian.

Jupiter also has dozens and dozens of orbiting moons, four of which can easily be seen using just about any telescope or even a cheap pair of binoculars. There are four larger moons, called the “Galilean” moons, in honor of their discoverer way back in the early 1600s. These look like little “stars” that circle the planet in periods of two to seventeen days. These moons are another story all by themselves, and I’ll have that next week in Skywatch.

Mike Lynch is an amateur astronomer and retired broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is the author of “Stars: a Month by Month Tour of the Constellations,” published by Adventure Publications and available at bookstores and adventurepublications.net. Mike is available for private star parties. You can contact him at mikewlynch@comcast.net.

Mike Lynch astronomy-stargazing programs

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