Jupiter is the biggest planet in our solar system. But it is smaller than what scientists had thought in the past.
What are the new measurements?
Scientists have made the most precise measurements to date of Jupiter’s size and shape. They used new data from Nasa’s robotic Juno spacecraft. This information will help them better understand this gas giant.
The Juno observations showed that Jupiter has a diameter of 142,976km through its equator. This is about 8km smaller than past measurements.
The data also showed that Jupiter’s diameter from the north pole to the south pole is 133,684km. This is about 24km smaller than previously estimated.
The older measurements of Jupiter were based on data gathered by Nasa in the 1970s.
Juno was launched in 2011. It has been orbiting Jupiter since 2016 and sending data back to Earth.
How did they measure it?
“When Juno passed behind Jupiter from Earth’s perspective, its radio signal travelled through the planet’s atmosphere before reaching Earth,” planetary scientist Eli Galanti said. He is the lead author of the study published last month in the journal Nature Astronomy.
The team measured how Juno’s signal changed as it passed through the planet. This is how they figured out Jupiter’s size with precision.
In comparison, Earth is a small rocky world.
Jupiter is so big that all the other planets could fit inside it. More than 1,300 Earths could fit in Jupiter. Jupiter is mainly made up of hydrogen and helium, with traces of other gases.
Precise new measurements of Jupiter are helpful to scientists. Models of the planet’s interior and its atmospheric structure rely on the size of its radius. Radius is a measure that is half of a circle or sphere’s diameter.
Galanti said that understanding Jupiter’s structure would be key to understanding how the solar system formed.
“Jupiter likely formed early and strongly influenced the distribution of material, the growth of other planets and the delivery of volatiles to the inner solar system, including Earth,” he said.
Volatiles are substances that evaporate easily. These include water, carbon dioxide and ammonia.
Galanti said volatiles were key because they “supplied Earth with water and key ingredients for its atmosphere and for life”.
Why does Jupiter look so colourful?
Jupiter is covered in colourful stripes and spots (see graphic). These stripes are actually long bands of clouds that circle around the planet. The spots are storms that can be found everywhere on the planet.
Scientists believe Jupiter’s sky has three cloud layers that are about 71km thick in total. The top cloud is probably made of ammonia ice. The middle layer is likely made of ammonium hydrosulfide crystals. The innermost layer may be made of water ice and vapour.
