Auroras on ice giant revealed: Space photo of the day

For the first time, the James Webb Space Telescope (JSWT) has revealed bright auroral activity on the planet Neptune.

Capturing the auroral activity on the ice giant has been long in coming, even though similar areas of trapped solar energetic particles have been successfully imaged in the atmospheres of Jupiter, Saturn and Uranus.

Why is this amazing?

Previously, the existence of auroral activity on Neptune was only hinted at, as instruments on NASA’s Voyager 2 probe, which flew by the planet in 1989, and the Hubble Space Telescope were unable to capture the glow.

“Turns out, actually imaging the auroral activity on Neptune was only possible with Webb’s near-infrared sensitivity,” said Henrik Melin of Northumbria University, whose research while at the University of Leicester has now been published in the journal Nature. “It was so stunning to not just see the auroras, but the detail and clarity of the signature really shocked me.”

In Webb's images of Neptune, the aurora appears as lighter blue or cyan areas set against the blue planet.

Is this the same as the northern or southern lights on Earth?

The auroral glow occurs because of the same basic interaction of solar particles interacting with the planet's atmosphere, but instead of being confined to the north and south poles, Neptune’s auroras are located at the planet’s mid-latitudes — roughly where South America is located on Earth.

The location of Neptune's auroral glow is the result the planet's magnetic field, which is tilted by 47 degrees from the planet’s rotation axis. Auroral activity occurs where a planet's magnetic fields converge into its atmosphere, so Neptune’s auroras are found far from its rotational poles.

What can we learn from Neptune's auroras?

The detection of Neptune's auroras will help astronomers better understand how particles from the sun interact with its atmosphere, providing a new area of study about ice giant planets.

The data from the Webb Space Telescope also enabled measurements of the temperature at the top of Neptune's atmosphere for the first time since Voyager 2's flyby. Those results may point to why Neptune’s auroras have gone unseen until now.

"I was astonished — Neptune's upper atmosphere has cooled by several hundreds of degrees,” Melin said in a Space Telescope Science Institute release. "In fact, the temperature in 2023 was just over half of that in 1989."

Where can I learn more?

You can read more about Neptune and aurora on Earth. You can also read what it would be like to see aurora on other planets and how infrared aurora was first detected on Uranus in 2023.