Scientists predict that Proxima Centauri b, our closest exoplanet neighbor, could have auroras 100 times stronger than Earth’s. Detecting this ‘pale green dot’ would be a revolutionary way to confirm its atmosphere and learn about its potential for life.

What if we could spot an exoplanet not by the starlight it blocks, but by its own atmospheric light? That’s the incredible idea behind the ‘Pale Green Dot’ concept. Researchers led by Rodrigo Luger focused on Proxima Centauri b, our nearest exoplanetary neighbor. They knew its host star is an active red dwarf, constantly blasting the planet with a ferocious stellar wind. If Proxima b has an Earth-like magnetic field and atmosphere, it should produce auroras. Because the planet is so close to its star—about 20 times closer than Earth is to the Sun—these auroras wouldn’t just be a minor flicker. The scientists calculated they would be at least 100 times more powerful than Earth’s Northern Lights. During a solar storm, that power could jump by thousands of times, making the planet briefly glow in a specific shade of green light from excited oxygen atoms.

Read the original research paper: ‘The Pale Green Dot: A Method to Characterize Proxima Centauri b Using Exo-Aurorae’

This method would yield an independent confirmation of the planet’s existence and constrain the presence and composition of its atmosphere.
— Rodrigo Luger, Lead Author

Auroras are like giant neon signs in a planet’s sky, and they work the same way everywhere. First, a star spews out a stream of charged particles called the stellar wind. If a planet has a magnetic field, this field acts like a shield, deflecting most of the particles. However, some get trapped and funneled down toward the magnetic poles. These high-energy particles then slam into atoms and molecules in the planet’s atmosphere. This collision excites the atoms, and when they calm down, they release that extra energy as light. On Earth, when particles hit oxygen high up, we get the famous green glow. The researchers predict the same thing would happen on Proxima b. The key difference is the intensity. Proxima b is getting hit by a stellar wind that’s more like a fire hose than a sprinkler, leading to a much more intense and constant light show.

Here at NorthernLightsIceland.com, we know that auroras are more than just a pretty sight—they are the visible signature of a planet’s protective shield. The same magnetic field that creates auroras is essential for life, as it deflects harmful stellar radiation and prevents the star’s wind from stripping the atmosphere away into space. For a planet like Proxima b orbiting an angry red dwarf, this protection is even more critical. Detecting an aurora there would be monumental. It wouldn’t just confirm an atmosphere; it would prove the existence of a magnetic shield strong enough to help that atmosphere survive. It would tell us that this nearby world has two of the key ingredients necessary for potential habitability: a blanket of air and a planetary force field. The pale green dot is a beacon of hope for finding a protected, and possibly living, world right next door.

Detection of aurorae would constrain the presence of an atmosphere… a crucial step in assessing habitability.
— NorthernLightsIceland.com Science Team

So, how do you find a tiny green glow from 4.2 light-years away? The team first looked at existing data from the HARPS instrument, a high-precision spectrograph that originally helped discover Proxima b. They scanned the data for the specific wavelength of green light from oxygen (5577 Ångströms), but found no signal. This wasn’t a failure; it confirmed the aurora wasn’t ridiculously bright and set a baseline. Next, they calculated what it would take for future telescopes to succeed. Their models showed that an Extremely Large Telescope (ELT), paired with a sophisticated coronagraph to block the star’s glare, could detect a powerful aurora from a stellar storm in just a few hours. Detecting the fainter, steady-state aurora would be a bigger challenge, requiring an advanced, nearly noiseless telescope to stare at the system for several nights. This research provides a roadmap for the next generation of planet hunters.

Q: So Proxima b has auroras just like Earth?
A: The physics would be the same, but the show would be far more intense! Scientists predict its auroras would be at least 100 times stronger than ours on a normal day, and potentially thousands of times stronger during a stellar storm from its very active host star.

Q: What color would the auroras be?
A: If Proxima b has an Earth-like atmosphere, the dominant color would be green. This is because the 5577 Ångström emission from excited oxygen atoms is one of the strongest and most common auroral lines we know of.

Q: Can we see these alien auroras with a telescope right now?
A: Unfortunately, no. The signal is far too faint and buried in the glare of the host star. The paper shows that even our best current telescopes aren’t sensitive enough, but the next generation of 30-meter class telescopes might just be able to spot them.

Q: Does this mean there’s life on Proxima b?
A: Not necessarily, but it’s a very positive sign! Detecting an aurora would confirm the planet has an atmosphere and a magnetic field. These two features are crucial for protecting a planet’s surface and are considered essential ingredients for a world to be habitable.

Using the Cassini spacecraft, scientists discovered that Saturn’s auroras are more complex than ever imagined. By observing in radio, ultraviolet, and infrared light simultaneously, they found parts of the main aurora spin with the planet while other ‘hot spots’ lag behind, revealing a dynamic dance in Saturn’s atmosphere.

In January 2009, NASA’s Cassini spacecraft stared at Saturn’s southern pole for a full planetary rotation, about 11 hours. What it saw changed our understanding of the ringed planet’s auroras. Scientists expected to see a single, unified light show spinning in sync with Saturn’s powerful magnetic field. Instead, they saw two different dances happening at once. The main auroral oval hosted a huge, bright region that was locked in step with the planet’s rotation, a phenomenon known as corotation. But simultaneously, smaller, isolated ‘hot spots’ were also seen drifting along the oval at a slower pace. This sub-corotation matches the speed of the cold plasma trapped further out in Saturn’s magnetosphere. This was the first time both motions were clearly observed co-existing, revealing a far more complex and layered auroral system than previously thought.

Read the original research paper on arXiv

We saw a complex dance: a huge, steady waltz accompanied by smaller, slower-moving spotlights all within the same auroral ring.
— L. Lamy, Lead Researcher

Like on Earth, Saturn’s auroras are created when energetic charged particles spiral down the planet’s magnetic field lines and collide with gases in the upper atmosphere. The main auroral oval marks the boundary between magnetic field lines that close near the planet and those that stretch far out into space. The discovery of two speeds tells us about the different sources of these particles. The large, co-rotating feature is likely powered by a massive electrical current system that is rigidly tied to Saturn’s fast rotation. In contrast, the smaller, sub-corotating spots are thought to be footprints of plasma blobs moving more slowly in the middle region of the magnetosphere. As these plasma blobs drift, they rain down electrons, creating glowing spots that lag behind the planet’s spin. Seeing both at once means we’re watching two different layers of the magnetosphere interacting with the atmosphere simultaneously.

Here at NorthernLightsIceland.com, we often talk about how the Sun’s solar wind triggers Earth’s auroras. But this study revealed Saturn can create its own ‘space weather’. During the observation, Cassini witnessed a powerful substorm-like event—a massive injection of energetic ions into the inner magnetosphere. This wasn’t caused by the Sun, but by an instability in Saturn’s own stretched-out magnetic tail, likely a plasmoid ejection where a magnetic bubble of plasma is violently released. This internal explosion of energy caused the aurora to flare up dramatically on the dawn side. This shows that while the Sun has an influence, giant planets like Saturn are powerful enough to drive their own auroral activity from within. It’s a reminder that every planet’s magnetic field and atmosphere interact in unique and spectacular ways.

It’s like finding out Saturn can create its own storms, independent of the Sun. The magnetotail stores energy and then releases it in powerful bursts.
— NorthernLightsIceland.com Science Team

This groundbreaking discovery was only possible because Cassini used a whole suite of instruments at the same time. The Ultraviolet Imaging Spectrograph (UVIS) captured detailed images of the auroral shapes. The Visual and Infrared Mapping Spectrometer (VIMS) measured the temperature and energy of the aurora in infrared. The Radio and Plasma Wave Science (RPWS) instrument listened for Saturn’s natural radio emissions, known as SKR. And the Ion and Neutral Camera (INCA) detected the injection of energetic particles that fueled the storm. By combining these datasets, scientists could directly link events. They saw that a specific type of flickering radio signal, called an SKR arc, perfectly corresponded to a sub-corotating UV hot spot. It was like hearing a sound and seeing exactly what was making it, a true multi-spectral ‘aha!’ moment in planetary science.

Q: Why do parts of Saturn’s aurora move at different speeds?
A: The different speeds reflect different regions of Saturn’s magnetosphere. The fast, co-rotating part is tied to the inner magnetic field which spins rigidly with the planet. The slower, sub-corotating spots are connected to plasma further out, which can’t keep up and lags behind.

Q: What is a ‘plasmoid ejection’?
A: It’s when a planet’s magnetic tail becomes so stretched and loaded with energy that it snaps back like a rubber band. This process violently ejects a massive bubble of plasma (a plasmoid) away from the planet, while sending another burst of energy and particles rocketing back towards it, causing intense auroras.

Q: Could we see Saturn’s aurora with a telescope from Earth?
A: No, not really. Saturn’s auroras are primarily in ultraviolet and infrared wavelengths, which are blocked by Earth’s atmosphere. To see them in their full glory, we need space-based telescopes like Hubble or spacecraft in orbit around Saturn, like Cassini was.

Q: How is Saturn’s aurora different from Earth’s?
A: While both are caused by particles hitting the atmosphere, Saturn’s auroras are more influenced by its rapid rotation and internal magnetospheric processes. Earth’s auroras are much more directly and immediately controlled by the activity of the solar wind blowing from our Sun.

Scientists were thrilled by a faint radio signal from the distant planet τ Boötis b, a potential sign of a massive aurora. But when they listened again with the same powerful telescope, the planet was silent, creating a cosmic mystery.

Imagine tuning an old radio and hearing a faint, mysterious broadcast from a station you’ve never heard before. That’s what happened in 2017 when scientists using the LOFAR radio telescope found a tentative signal from the τ Boötis system, 51 light-years away. They suspected it was coming from the planet τ Boötis b, a massive ‘hot Jupiter’. This whisper from across the stars was incredibly exciting because it suggested the planet had a powerful magnetic field—a key ingredient for planetary evolution. But science demands proof. A follow-up campaign was launched in 2020 to listen again, covering more of the planet’s orbit than ever before. The telescope was aimed, the data poured in, but this time… there was only static. The signal was gone.

Read the full research paper on arXiv: “Follow-up LOFAR observations of the τ Boötis exoplanetary system”

If confirmed, this detection will be a major contribution to exoplanet science. However, follow-up observations are required to confirm this detection.
— Jake D. Turner et al., Abstract

So, what kind of signal were they looking for? It’s created by a process called the Cyclotron Maser Instability (CMI). Think of it like a natural cosmic laser. When energetic particles from the star (the stellar wind) slam into a planet’s magnetic field, they get trapped and spiral around the magnetic field lines at incredible speeds. This spiraling motion makes the electrons radiate powerful, focused beams of radio waves. It’s the same basic physics that creates auroras on Earth, but on a ‘hot Jupiter’ like τ Boötis b, this process would be thousands of times more powerful. The radio waves are beamed out like a lighthouse, and we can only detect them if that beam happens to sweep across Earth. This is why finding such a signal is both difficult and incredibly informative.

CMI radio emission is circularly polarized, beamed, and time-variable.
— Philippe Zarka et al., Introduction

On Earth, our magnetic field funnels solar particles to the poles, creating the beautiful Northern and Southern Lights. The signal from τ Boötis b would be the radio equivalent of an aurora on a colossal scale. Finding a magnetic field tells us so much about a planet. It acts as a shield, deflecting harmful stellar radiation and preventing the planet’s atmosphere from being stripped away into space. For rocky planets in the habitable zone, a magnetic field might even be essential for life. For a gas giant like τ Boötis b, it gives us clues about its deep interior, where the field is generated. While this planet is far too hot for life, understanding its magnetic environment helps us build better models for all kinds of planets, including potentially habitable ones.

A magnetic field might be one of the many properties needed on Earth-like exoplanets to sustain their habitability.
— Jean-Mathias Grießmeier et al., Introduction

How did the scientists know the silence wasn’t just a problem with their telescope? Their method was clever. For every observation, they used an ‘ON-beam’ pointed directly at τ Boötis and three simultaneous ‘OFF-beams’ aimed at empty patches of sky nearby. This allowed them to subtract any background noise or radio interference from Earth, ensuring that any real signal would have to come from the target. When they compared the ON-beam to the OFF-beams in the new data, they were identical—just cosmic static. The lack of a signal is now a puzzle. Was the first detection an error? Or is the planet’s radio broadcast variable? The star itself has a rapid 120-day magnetic cycle, which could be turning the planet’s radio show on and off. The detectives need more clues.

Our new observations do not show any signs of bursty or slow emission from the τ Boötis exoplanetary system. The cause for our non-detection is currently degenerate.
— Jake D. Turner et al., Abstract

Q: So, does the planet τ Boötis b have a magnetic field or not?
A: We still don’t know for sure. The first hint of a signal suggests it might, but the follow-up non-detection makes it an open mystery. More observations are needed to solve it.

Q: Why would the signal disappear?
A: There are a few possibilities. The first signal could have been a very rare fluke or an instrumental glitch. More likely, the planet’s radio emission is variable. The host star’s own activity changes, which could affect the ‘power’ of the planet’s aurora, making it sometimes too faint for us to detect.

Q: What is a ‘hot Jupiter’?
A: A hot Jupiter is a type of gas giant planet, similar in size to our Jupiter, but that orbits extremely close to its star. This makes them incredibly hot, with temperatures reaching thousands of degrees.

Q: Why is it important to find magnetic fields on other planets?
A: Magnetic fields act like a protective shield for a planet, deflecting harmful particles from its star. This can prevent the atmosphere from being blown away into space, which is considered a critical factor for a planet’s long-term habitability.

Scientists used one of the world’s most powerful telescopes to hunt for the glowing auroras on two distant ‘hot Jupiter’ planets. But the search came up empty, creating a cosmic mystery about these strange and stormy worlds.

Imagine a planet bigger than Jupiter, orbiting so close to its star that its year lasts only a few days. These are ‘hot Jupiters’, and scientists believe they should have spectacular auroras, far more powerful than Earth’s Northern Lights. Researchers aimed the giant Keck telescope at two of these worlds, WASP-80b and WASP-69b, hoping to catch the tell-tale infrared glow of a special molecule called H3+. This molecule is created when energetic particles from the star slam into the planet’s atmosphere, guided by a magnetic field. Finding this glow would be a huge discovery, but after hours of staring into the cosmos, the light just wasn’t there.

Read the original research paper on arXiv

On Earth, auroras happen when solar wind particles hit oxygen and nitrogen, making them glow green and red. But on gas giants like Jupiter, the atmosphere is mostly hydrogen. When charged particles funnel down the planet’s powerful magnetic field lines and crash into the hydrogen gas, they create a new, energized molecule called H3+ (pronounced ‘H-three-plus’). This molecule is unstable and quickly releases its extra energy as infrared light—light that is invisible to our eyes but can be seen by special telescopes. Scientists call H3+ the ‘thermostat’ of Jupiter’s upper atmosphere because this process is the main way the planet cools itself down. Finding this specific infrared light on an exoplanet is the best way to confirm an aurora is happening.

Auroras aren’t just pretty light shows; they are giant signposts in space. The single most important thing an aurora tells us is that a planet has a magnetic field. A magnetic field acts like a planetary shield, deflecting harmful radiation and stopping the star’s wind from blowing the atmosphere away. Finding a magnetic field on an exoplanet would be a first, and it would give us vital clues about the planet’s interior and its potential to hold onto an atmosphere over billions of years. Studying these distant auroras also helps us understand the ‘space weather’ created by the host star, giving us a window into the violent interactions between stars and their planets.

Observations of auroras on exoplanets would provide numerous insights into planet-star systems, including potential detections of the planetary magnetic fields.
— Richey-Yowell et al. (2025)

Finding a faint aurora from trillions of miles away is like trying to hear a whisper in a rock concert. The planet’s light is completely overwhelmed by its star. To find the signal, astronomers used high-resolution spectroscopy, a technique that splits the incoming light into thousands of different shades of color. Then, they used a powerful data-sifting method called cross-correlation. They created a computer model of what the H3+ aurora ‘fingerprint’ should look like, with all its dozens of individual light lines. They then compared this model to the real data, shifting it around to match the planet’s velocity as it orbited its star. If a real signal was hidden in the noise, it would pop out when it lined up perfectly with the model. But even with this clever trick, no signal appeared.

Q: Does this mean these planets have no auroras or magnetic fields?
A: Not necessarily. It just means that any auroras they have are too faint for our current telescopes to see. The magnetic fields might be weaker than expected, or something else in the atmosphere could be interfering with the aurora’s glow.

Q: Why can’t we just take a picture of the auroras like we do on Earth?
A: These planets are incredibly far away and extremely faint compared to their bright host stars. We can’t resolve them into a picture; all we receive is a single point of light that contains the combined light of the star and the planet, which we must then carefully separate using techniques like spectroscopy.

Q: What is a ‘hot Jupiter’?
A: A hot Jupiter is a type of gas giant exoplanet, similar in size to our own Jupiter, but that orbits extremely close to its star. This makes them incredibly hot, with temperatures reaching thousands of degrees, and gives them very short orbital periods (a ‘year’ can be just a few Earth days).

Q: What’s the next step in the search for alien auroras?
A: The next step is to use even more powerful observatories, like the upcoming class of Extremely Large Telescopes (ELTs). With their giant mirrors, they will be sensitive enough to either finally detect these faint auroras or confirm that they are truly absent, deepening the mystery.

Scientists studying WASP-76b — a giant planet 640 light-years away — discovered that its skies may rain molten metal. This strange world helps us understand how heat, magnetism, and space weather shape the Northern Lights on Earth.

In 2020, astronomers using the European Southern Observatory’s Very Large Telescope (VLT) observed something extraordinary on a distant exoplanet known as WASP-76b. Spectroscopic data revealed clear signatures of ionized and neutral metals, including vaporized iron, in its upper atmosphere — a discovery that sparked intense interest across the astrophysics community.

Building on that initial detection, a 2021 analysis led by Ehrenreich et al., published on arXiv as “The three-dimensional structure of the ultrahot Jupiter WASP-76 b” (arXiv:2102.01095v1), explored how the planet’s extreme temperature differences drive such exotic chemistry. Their findings suggest that the day side of WASP-76b — blasted by constant stellar radiation — reaches over 2400 °C (≈4350 °F), hot enough to vaporize metals like iron.

Intense supersonic winds then carry these metallic vapors toward the cooler night side, where the temperature drops dramatically. There, the vapor condenses into molten droplets of iron rain — a literal storm of liquid metal falling through alien skies.

“It’s like a cosmic foundry — one side acts as a furnace, the other a cooling chamber,” explains Dr. David Ehrenreich of the University of Geneva, lead author of the study.

WASP-76b is what scientists call an ultra-hot Jupiter — a gas giant similar in size to Jupiter but orbiting extremely close to its star. It’s so close, in fact, that a full “year” on the planet lasts less than two Earth days. Because of this tight orbit, WASP-76b is tidally locked, meaning one side permanently faces its star while the other remains in endless night.

This leads to staggering temperature contrasts. On the day side, conditions are so extreme that molecules break apart and metals like iron literally turn into vapor. Meanwhile, the night side is much cooler — still thousands of degrees hot, but cold enough for those metal vapors to condense back into liquid.

The study by Ehrenreich et al. (2021, arXiv:2102.01095v1) used a method called high-resolution transmission spectroscopy to map how gases move across the planet. By watching how starlight filters through different parts of the atmosphere during its orbit, researchers could trace wind speeds, temperature gradients, and chemical signatures in three dimensions.

What they found was a massive heat-driven circulation system — winds likely exceeding 5 km per second (about 18,000 km/h) transporting vaporized metals from the scorching day side to the cooler night hemisphere. Once there, the vapor condenses and falls as molten iron droplets before being re-vaporized when the winds carry it back into daylight again.

In essence, WASP-76b operates like a planet-sized metal recycling machine, continuously melting and raining iron in a dramatic loop powered by stellar radiation.

This discovery matters not just for its strangeness, but because it gives astronomers a glimpse into how extreme heat, magnetism, and atmospheric flow interact — processes that also influence space weather and auroral activity throughout the galaxy, including here on Earth.

Why does a planet hundreds of light-years away matter to Icelanders watching the Northern Lights?

Because the same forces are at work.
The way charged particles move in WASP-76b’s magnetic field mirrors how the solar wind interacts with Earth’s magnetosphere to produce auroras.

Studying these alien storms helps scientists predict how radiation and plasma behave in extreme conditions — improving models of space weather that affect satellites, GPS, and auroral activity.

The discovery relied on spectroscopy — analyzing starlight as it passes through a planet’s atmosphere.
Different elements absorb specific wavelengths, creating a chemical “fingerprint.”
By detecting these signatures, scientists can tell which gases are present — even from hundreds of light-years away.

“Spectroscopy is our interstellar thermometer and barometer,” explains Dr. Ehrenreich. “It tells us what’s happening in atmospheres we can’t physically reach.”

Future missions like the James Webb Space Telescope will look for similar signs of metallic weather — and possibly even aurora-like glows on other worlds.

Q: What is WASP-76b?
A: It’s an ultra-hot gas giant orbiting very close to its star. The extreme heat vaporizes metals like iron.

Q: Does it really rain metal there?
A: Yes — iron gas from the day side likely condenses and falls as molten droplets on the night side.

Q: What does this have to do with auroras?
A: Both involve the movement of charged particles and magnetic fields — studying one helps us understand the other.

Q: Can telescopes actually see the rain?
A: Not directly. Scientists infer it from the light signatures captured by spectrographs like ESPRESSO and HARPS.

Q: How far away is WASP-76b?
A: Roughly 640 light-years from Earth, in the constellation Pisces.