Jupiter is smaller and more ‘squashed’ than scientists believed, NASA said in a press release announcing a new study.
Jupiter, the biggest planet in our solar system, is not as big as we thought.
For more than half-a-century, astronomers thought they had a good idea of the gas giant’s shape and size. Now, a fresh analysis of observations from NASA’s Juno orbiter is causing scientists to rethink their understanding of the imposing planet.
Juno, which for nine years divided its time between observing Jupiter and studying its moons, has beamed back plenty of data for scientists to comb through even after the orbiter’s primary mission came to an end in 2025. Some of that data, compiled from a series of flybys of Jupiter, is what helped a team of researchers to determine that the planet may be slightly smaller and more “squashed” than previous observations suggested, according to NASA.
The new measurements of Jupiter’s size and shape, published Feb. 2 in a study the journal Nature Astronomy, are the first since two NASA missions observed the planet more than 50 years ago.
“Textbooks will need to be updated,” study coauthor Yohai Kaspi, an astronomer at the Weizmann Institute of Science in Israel, said in a statement.
Here’s everything to know about Jupiter, and the latest measurements of its size.
How big is Jupiter? What to know about gas giant
Jupiter is not only the largest in the solar system, but is so humongous that it’s more than twice as massive as the other planets combined.
The gas giant is about 11 times wider than Earth alone, with a diameter around its equator of 88,846 miles.
And it’s size is far from the only extreme feature that defines the fifth planet from the sun. The world is home to gigantic storms bigger than Australia, 100-mph winds pummeling its northern reaches and a rocky moon named Io orbiting it that is notoriously riddled with lava-spewing volcanoes.
Jupiter’s gravity, often called the “architect” of our solar system, played a critical role in shaping the orbits of other planets and sculpting the disk of gas and dust from which they formed.
NASA’s Juno orbiter helps redefine size of gas giant
Jupiter is still gigantic, even after the latest analysis of observations made by NASA’s Juno spacecraft.
Just not as big as scientists previously believed.
Observations from the Juno orbiter made during 13 flybys of the gas giant helped scientists determine that Jupiter is about five miles narrower at its equator and 15 miles flatter at the poles than previous measurements concluded.
To reach the new conclusions, a team of researchers analyzed Juno’s radio occultation data, which essentially allows the spacecraft to peer through Jupiter’s dense clouds in order to understand the planet’s internal structure.
As it passed behind Jupiter from Earth’s point of view, Juno beamed signals back to NASA’s array of giant radio network antennas on Earth known as the Deep Space Network. By measuring the change in frequency when the signals were bent in Jupiter’s upper atmosphere, the ionosphere, scientists can calculate characteristics of the planet.
The measurements are the first made of Jupiter’s size and shape since both NASA’s Pioneer and Voyager missions made observations of the gas giant in the 1970s, the agency said in a press release highlighting the study.
Why did Jupiter get smaller?
Jupiter is not only smaller than previously believed, but has also been steadily shrinking over the course of its lifetime. Astronomers estimate that Jupiter was long ago twice the size it is now, and could be losing up to two centimeters a year.
This is because of a process by which the planet grows smaller as it gradually cools and its internal temperature drops, causing the planet to lose energy and consistently contract.
What to know about the Juno spacecraft
NASA’s Juno spacecraft has been probing beneath Jupiter’s dense clouds since it arrived in 2016 seeking answers about the origin and evolution of the gas giant.
That mission, which was slated to end in September 2025, also extends to Jupiter’s rings and many moons. For instance, the orbiter has gotten several looks at the volcano-ridden surface of the Jovian moon Io.
Now that Juno’s mission has officially come to a conclusion, the spacecraft will eventually be pulled by Jupiter’s powerful gravity into the planet’s atmosphere to be destroyed – not unlike how NASA’s Cassini spacecraft was deliberately plunged into Venus in 2017.
But a successor to the mission, NASA’s Europa Clipper, is on the way to Jupiter’s orbit to study a Jovian moon of the same name.
Eric Lagatta is the Space Connect reporter for the USA TODAY Network. Reach him at elagatta@gannett.com