NASA’s Webb Telescope has made history by capturing never-before-seen auroras on Neptune, the most distant planet in our solar system. Located 2.8 billion miles away from Earth, Neptune is not alone in displaying this phenomenon, as it occurs on every other planet except Mercury due to three essential ingredients: high-speed charged particles, a magnetic field, and an atmosphere.
Auroras form when charged particles collide with the planet’s atmosphere, creating a spectacular display of lights. The process requires a source of positively or negatively charged particles, which can be seen in Earth’s auroras caused by solar upheavals. Even planets without natural magnetic fields, like Venus, can still have auroras due to induced magnetic fields from the sun.
NASA’s Voyager 2 probe spotted signs of possible auroral activity on Neptune during its 1989 flyby, but clear images remained elusive until June 2023. The Webb Telescope captured these images using its infrared-sensitive instruments, revealing a patchy auroral glow and the presence of trihydrogen cation (H3+), a positively charged form of hydrogen.
Notably, Neptune’s auroras do not appear at its rotational poles like on Earth or Jupiter and Saturn but instead spread across mid-latitudes. This is due to Neptune’s peculiar magnetic field, tilted 47 degrees from its rotation axis. The cause of this hidden phenomenon lies in a steep temperature drop in Neptune’s upper atmosphere.
According to scientists, the Webb team measured an unprecedented cooling of this region, which could result in fainter auroras. This significant change might be related to a dramatic shift in Neptune’s magnetic field over time. With the Webb Telescope now studying Neptune over a full solar cycle, results could provide insights into its unique magnetic field and even shed light on its unusual tilt.
Source: https://www.duluthnewstribune.com/lifestyle/astro-bob/astro-bob-nasas-webb-telescope-captures-never-before-seen-auroras-on-neptune