Aurora on Neptune, as seen by the james Webb Space Telescope and the Hubble Space Telescope.
NASA, ESA, CSA, STScI, Heidi Hammel (AURA), Henrik Melin (Northumbria University), Leigh Fletcher (University of Leicester), Stefanie Milam (NASA-GSFC)
Astronomers have used the combined talents of the James Webb Space Telescope and the Hubble Space Telescope to capture vivid auroras on the planet Neptune for the first time.
The farthest planet from the sun, Neptune is an ice-giant planet that looks blue thanks to methane in its atmosphere and an incredibly complex magnetic field.
That magnetic field has been laid bare by this first-ever image of Neptune’s aurora. Auroras are caused by charged particles in the solar wind — which originates in the sun — getting trapped in a planet’s (or moon’s) atmosphere and “exciting” atoms in the upper atmosphere, creating photons of light as energy is released.
That process typically results in aurora around the poles of a planet or moon because that's where its magnetic field is weakest. However, things are different in Neptune. As well as being very distant from the sun and extremely cold, Neptune's magnetic field is irregular. That's because Neptune is tilted 47 degrees from its rotational axis, [according](https://science.nasa.gov/neptune/neptune-facts/) to NASA, with this misalignment making its magnetic field vary hugely during one rotation — which takes 16 hours. That's why, in this image of the cyan-colored aurora, it's patchy and scattered rather than around the poles.
The image of the aurora was taken using the extremely sensitive Near-Infrared Spectrograph on the Webb telescope, with that data combined with visible light images from Hubble’s Wide Field Camera 3 to create the first direct visual confirmation of aurora on Neptune.
At the left, an enhanced-color image of Neptune from the Hubble Space Telescope. At the right, that ... More image is combined with data from the James Webb Space Telescope.
NASA, ESA, CSA, STScI, Heidi Hammel (AURA), Henrik Melin (Northumbria University), Leigh Fletcher (University of Leicester), Stefanie Milam (NASA-GSFC)
NIRSpec captures infrared light — electromagnetic radiation with wavelengths longer than visible light — invisible to the human eye. It's essentially heat, which Webb cap captures because it operates at -370 degrees Fahrenheit (-223 degrees Celsius).
It's been difficult for astronomers to capture Neptune's auroras because, it's theorized, the planet's upper atmosphere is cooling. Webb’s instruments detected a temperature drop of several hundred degrees when it took the images, which is thought to be why they were detectable when typically they are not.
**Auroras Across The Solar System: Planets**
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Neptune joins a growing list of solar system bodies that exhibit auroral activity. Every planet in our solar system experiences auroral activity save for Mercury, which lacks a substantial atmosphere.
Saturn exhibits bright ultraviolet auroras that, unlike Earth's, maintain consistent intensity regardless of solar wind turbulence, suggesting its magnetic field can absorb and dissipate energy without injecting it into the atmosphere.
Jupiter has probably the most spectacular auroras in the solar system, displaying bright, vibrant, multi-colored auroras. Mars has faint proton auroras of Mars, and Uranus has faint ultraviolet emissions.
A curtain of glowing gas is wrapped around Jupiter''s north pole like a lasso December 19, 2000 in a ... More Hubble telescope photo. (Photo by NASA/Newsmakers)
Getty Images
**Auroras Across The Solar System: Moons**
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Studying auroras allows researchers to map planetary magnetic fields, assess atmospheric composition, and even infer the presence of subsurface oceans — as seen with some of Jupiter’s moons.
Ganymede, Jupiter’s largest moon, has auroral ovals that remain fixed regardless of the moon's wobble, suggesting the presence of an electrically conductive layer (likely a saltwater ocean) beneath its surface. Europa and Callisto (other Jovian moons) also boast auroras, which has helped scientists identify them as potentially harboring subsurface oceans.
_Wishing you clear skies and wide eyes._