Celestial News: See Jupiter at its best
For Steamboat Pilot & Today
Jupiter is the planet that was almost a star. It’s true! Like a star, Jupiter is composed mostly of hydrogen gas. It radiates more heat than it receives from space. It generates a powerful magnetic field around itself. It has a family of smaller worlds that formed alongside it and continue to orbit around it. What does a star have that Jupiter doesn’t have?
Although Jupiter’s core is hot, it is not hot enough to create a nuclear furnace, something that every real star possesses. Jupiter would need to be about 80 times more massive than it is in order to fire up nuclear fusion in its core.
As big as it is, Jupiter has to settle for being the largest planet in our solar system. Jupiter could swallow 1,000 Earths, if it were hollow inside, and the Sun could swallow 1,000 Jupiters!
Jupiter and Earth are in a perpetual race around the Sun, a race that the faster Earth will always win. Once every 13 months, the Earth gains a lap on Jupiter and pulls up alongside it in an event called opposition. It is during opposition that a planet is closest to the Earth and best visible in our sky.
This year, Jupiter arrives at opposition on the night of Monday, June 10. At a distance of 398 million miles, this will be the closest opposition of Jupiter since January 2014. Jupiter will outshine everything in our evening sky.
When at opposition, Jupiter shines all night long, rising in the southeast at sunset and setting in the southwest at sunrise. The best view of the giant planet will happen around midnight, when the planet is at its highest point in the southern sky. Behind Jupiter will shine the stars of the constellations Ophiuchus and Scorpius and the rich star clouds of the Milky Way.
About one fist-width to Jupiter’s lower right shines the red giant star Antares, the heart of the celestial Scorpion. Two handspans to Jupiter’s left is the ringed planet Saturn, shining in the neighboring constellation of Sagittarius.
If you have a telescope of any size, even a good pair of binoculars, aim them at Jupiter around the time of opposition to experience one of the greatest thrills that backyard astronomy has to offer — seeing the Galilean moons of Jupiter.
These four planet-sized moons, discovered by Galileo in 1610, swing around Jupiter in just a few days and are never in the same positions twice. Sometimes, all four might appear on the same side of Jupiter; at other times you’ll see two on one side and two on the other. Occasionally, one or more moons might play hide and seek in front of or behind Jupiter.
As a kid, I used to love keeping track of Jupiter’s moons from night to night with my little 3-inch telescope. Their names became very familiar to me: Io, Europa, Ganymede and Callisto.
A good backyard telescope will reveal Jupiter to be a glowing yellow ball with two dark cloud stripes straddling its equator. It requires a 6-inch telescope or larger to get a good glimpse of Jupiter’s colossal storm, the Great Red Spot.
Recent studies have shown that the Great Red Spot is shrinking. It was once wider than three Earths, but Jupiter’s most famous storm now is only a bit wider than one Earth. Will it continue to shrink and soon disappear? Scientists aren’t sure what’s going to happen next with the Great Red Spot.
Our own moon will team up with Jupiter in the sky about once a month for the remainder of the year. Look for them side by side on the following nights: 10 p.m. June 16, 10 p.m. July 13, 9 p.m. Aug. 9, 9 p.m. Sept. 5, 8 p.m. Oct. 3, 7 p.m. Oct. 31 and 5:30 p.m. Nov. 28.
Jimmy Westlake retired from full-time teaching at Colorado Mountain College Steamboat Springs in 2017 after 19 years as professor of physical sciences. Celestial News appears monthly in the Steamboat Pilot & Today. Check out Westlake’s astrophotography website at jwestlake.com.
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