Is Jupiter on a diet: New measurements say it's smaller than we thought

New measurements from NASA’s Juno spacecraft reveal that Jupiter, the largest planet in our solar system, is slightly smaller and flatter than previously thought. This discovery means that textbooks may need to be updated to reflect the new data, according to Yohai Kaspi of the Weizmann Institute in Israel.

A Revised Understanding of Jupiter’s Size

For over 50 years, scientists relied on measurements from NASA’s Pioneer 10 and 11, as well as Voyager 1 and 2 missions, which provided just six data points. The new measurements, based on 26 data points collected by Juno, indicate that Jupiter’s equatorial diameter is approximately 88,841 miles (142,976 km) – about 5 miles (8 km) smaller than earlier estimates. The planet is also about 15 miles (24 km) narrower at the poles than previously recorded.

Did You Know? Jupiter’s fast rotation, completing a rotation in just under 10 hours, causes it to bulge at the equator.

How Juno Made the Discovery

Juno’s measurements were obtained using a technique involving radio signals. As the spacecraft passed behind Jupiter from Earth’s perspective, scientists tracked how the signals bent due to Jupiter’s upper atmosphere. These signal distortions provided detailed information about the planet’s shape and size. Maria Smirnova of the Weizmann Institute developed the techniques used to process this data.

Since 2016, Juno has been orbiting Jupiter, and since 2021, its trajectory has allowed for close fly-bys of Jupiter’s Galilean moons and passes behind the planet as seen from Earth.

Expert Insight: While the difference of a few kilometers may seem small, these refined measurements are crucial for improving models of Jupiter’s interior structure and gaining a more accurate understanding of the gas giant’s composition and dynamics.

Implications for Planetary Science

The revised measurements are significant because they allow for a better fit between models of Jupiter’s interior, gravity data, and atmospheric measurements. Understanding Jupiter, the “gold standard” for gas giant planets, can also improve our understanding of similar planets both within our solar system and around other stars.

The findings were published on February 2 in the journal Nature Astronomy.

Frequently Asked Questions

Is Jupiter actually shrinking?

No, the size of Jupiter itself has not changed. The new measurements reflect improvements in how scientists are able to measure the planet’s dimensions.

What is Juno’s role in these new measurements?

Juno, currently orbiting Jupiter, has provided 26 new data points, allowing for more precise measurements than the six data points collected by previous missions like Pioneer and Voyager.

How are scientists measuring Jupiter’s size?

Scientists measure Jupiter’s size by tracking how radio signals bend as they pass through the planet’s atmosphere while Juno passes behind Jupiter from Earth’s perspective.

As our understanding of Jupiter evolves, what other surprises might the gas giant reveal about the formation and evolution of planetary systems?

Is Jupiter on a diet: New measurements say it’s smaller than we thought