Jupiter, fifth from the sun and 300 times larger than Earth
A young patron from the Grayslake Area Public Library wondered, "How far is Jupiter from Earth?"
Time flies, at least on Earth. Earth years zoom by at supersonic speed compared to Jupiter's years. The big, gassy planet savors its journey around the sun, making one revolution every 11 Earth years.
Jupiter has some remarkable qualities. It's a gigantic gas ball mostly made of helium and hydrogen. Fifth in line from the sun, it's the biggest planet in our solar system, 300 times larger than Earth. It's kept company by a multitude of moons -- 79 and possibly more.
In 24 hours the Earth makes one full rotation, a spin around its axis that marks one 24-hour day. The nimble giant Jupiter does that in half the time. Its freaky fast rotation binds together its gasses into a planetary mass.
"Jupiter is so massive that even the lightest gas, hydrogen, cannot escape Jupiter's gravity, and, in fact, is compressed into a liquid form in Jupiter's interior," NASA spokesperson David C. Agle said.
"Jupiter's rapid rotation causes it to bulge out near the equator, so its actual shape is not quite spherical. Jupiter's many moons are mostly ice and rock, but many of them are large enough that their own gravity has pulled them into spherical shapes as well."
So how far is Jupiter from Earth? There are two answers to the question.
"Jupiter is currently about 413 million miles from the Earth," Lake County Astronomical Society President Tony Yelk said. "The distance between the planets varies from 365 million to 600 million miles," due to their elliptical orbits.
There's about a 13-month cycle in which the planets pull closer and then traverse apart, Yelk said. This year, they were closest in June. That will recur in July of next year.
Grab a telescope or binoculars and gaze into the night sky. Don't have any? Borrow a telescope from your local library. The Lake County Astronomical Society has made telescopes available to patrons at Lake County libraries.
Jupiter is now visible in the southeastern sky. Yelk promises a stellar experience.
"When you look at Jupiter through a telescope or binoculars, you will see what appears to be four stars to either side of the planet. But those aren't stars. They are the four largest moons of Jupiter -- Io, Europa, Ganymede, and Callisto," Yelk said. "They are called the 'Galilean Moons' because they were first seen by Galileo back in the early 1600s."
In the 1960s, experts determined that they could use Jupiter's gravitational pull to propel space objects beyond our solar system. Scientists later focused on Jupiter as a destination for scientific exploration and launched a solar-powered space probe called Juno in 2011.
Scientists believe studying Jupiter will help complete the story of how our solar system formed.
Juno made the 400-million-plus-mile journey to Jupiter in only four years. The Juno probe snaps pictures of the giant planet and carries specially crafted instruments to measure and map Jupiter, take readings on the planet's auroras and magnetosphere, and investigate the core.
Originally designed to make 14-day orbits of the planet, the spacecraft makes a 53-day orbit to better manage Juno's fuel reserves.
Yelk stresses the impact of the mission.
"Recently, Juno detected changes in Jupiter's magnetic field. This is important to scientists because it marks the first time the changes in another planet's magnetic field have been measured," he said.
"These observations can't be made from Earth and are of special interest to scientists studying the Earth's magnetic field. Last year, NASA extended the mission until July 2021, so we'll see what else we can learn about our giant celestial neighbor."
See the stars from your library's backyard with the Lake County Astronomical Society. Upcoming programs include Astronomy Under City Lights Aug. 7 at Aspen Drive Library in Vernon Hills and Sept. 9 at the Grayslake Area Public Library in Grayslake.
More information can be found on the library's website or at www.lcas-astronomy.org.
Check it outThe Grayslake Area Public Library suggests these titles on Jupiter:
• "Exploring Jupiter" by Richard Alexander
• "20 Fun Facts About Gas Giants" by Arielle Chiger and Matthew Elkin
• "Jupiter" by Rosanna Hansen
• "Destination Jupiter" by Giles Sparrow
• "Planet Jupiter" by Ann O. Squire