Neptune, the eighth and most distant planet in our Solar System, is a fascinating ice giant well known for its blue appearance and fascinating atmospheric phenomenon. It gets it’s colouration from its composition, being made up of mostly of hydrogen, helium, and methane. Winds in its atmosphere can reach speeds of up to 2,400 kilometres per hour and it’s home to a massive storm just like the Great Red Spot on Jupiter. Not surprisingly given Neptune’s distance from the Sun, it remains one of the coldest planets in the Solar System with its temperature dropping to around -214°C.
NASA image captured by Voyager 2 in 1989 (Credit : NASA)
NASA’s James Webb Space Telescope (JWST) often hones in on Neptune and just recently has spotted auroral activity. It’s previously only been seen fleetingly by Voyager 2 when it passed by in 1989. The aurora on Neptune are no different to those we often seen here on Earth where solar particles become trapped in the magnetic field and collide with the upper atmosphere. This creates the amazing glow we perceive as the northern lights or aurora borealis in the northern hemisphere or aurora australis or southern lights in the south. Aurora on Jupiter, Saturn, and Uranus are fairly common place but Neptune’s have been rather elusive so this recent observation is somewhat of a breakthrough.
“Actually imaging the auroral activity on Neptune was only possible with Webb’s near-infrared sensitivity,” – lead author Henrik Melin of Northumbria University.
The images from JWST’s NIRCAM (the Near Infra-Red Camera) showed a strong emission line of the trihydrogen cation (containing three hydrogen atoms and two electrons,) which is an indicator of auroral activity. The image from Webb reveals subtle cyan-coloured splotches that represent the aurora. This wouldn’t have been possible without the advanced capabilities of the JWST.
Artist impression of the James Webb Space Telescope (Credit : NASA)
Unlike auroras on Earth, Jupiter, or Saturn, Neptune’s auroral activity is unusually positioned at the planet’s mid-latitudes instead of near its poles. It’s thought this is the result of its magnetic field being tilted 47 degrees from its rotational axis. This unusual alignment, first discovered by Voyager 2 in 1989, means that the auroras occur far from the planet’s rotational poles, creating a fascinating pattern.
The absence of Neptunian aurora can now be attributed to significantly colder temperatures, as revealed by this recent study published in Nature Astronomy. The images not only reveal these extraordinary aurora but also provide more into how solar particles interact with Neptune’s magnetic field, opening a whole new window of understanding into the atmospheric science of ice giants. The team now hope to further study Neptune’s auroras over a complete solar cycle using JWST.
Source : NASA’s Webb Captures Neptune’s Auroras For First Time