Proxima Centauri: The closest star to Earth is extremely violent

In our vast galaxy, one star holds a special position – Proxima Centauri. Located just over four light-years away, it’s the closest star to our solar system. This proximity alone makes it a focus of scientific curiosity. But there’s another reason it captures attention.

Proxima Centauri hosts a planet that lies in the star’s habitable zone – a region where conditions could support liquid water. That simple fact sparks questions about the possibility of life.

Yet, this hope runs into a powerful obstacle: Proxima Centauri itself. A recent study reveals that this star may be far too volatile for comfort.

While astronomers already knew Proxima flared in visible light, new radio and millimeter-wavelength data from the Atacama Large Millimeter/submillimeter Array (ALMA) uncovers just how extreme its behavior truly is.

What we once saw as a quiet red dwarf now shows itself as an engine of explosive energy.

Dark side of a habitable zone

Proxima Centauri’s flares are no minor sparks. These are intense surges of radiation and particles, resembling solar flares from our Sun – but with much greater impact.

In our solar system, Earth’s thick atmosphere and magnetic field protect us. They absorb and deflect these charged particles, turning potential destruction into dazzling auroras.

But what happens when a planet doesn’t have that protection? That’s the core concern for scientists observing Proxima Centauri. Its rocky planet, Proxima b, may lie at the right distance for liquid water – but it also sits right in the blast zone of near-constant stellar flares.

Each flare carries the potential to tear apart an atmosphere, destroying essential elements like ozone and water vapor. Without these, surface conditions become hostile to any form of life we currently understand.

The engine behind the storm

A team of astronomers led by Kiana Burton from the University of Colorado and Meredith MacGregor from Johns Hopkins University took a closer look.

They examined both new and archival ALMA data to study flare activity in the millimeter-wavelength range. Their findings, published in The Astrophysical Journal, offer fresh insight into the nature of these flares.

Proxima Centauri is not just small – it’s magnetically intense. Unlike our Sun, which has a layered structure with both convective and non-convective zones, Proxima appears to be fully convective.

This structure allows magnetic fields to twist freely, build tension, and then violently snap. That process releases massive amounts of energy and particles into surrounding space.

“Our sun’s activity doesn’t remove Earth’s atmosphere and instead causes beautiful auroras, because we have a thick atmosphere and a strong magnetic field to protect our planet. But Proxima Centauri’s flares are much more powerful, and we know it has rocky planets in the habitable zone,” noted MacGregor.

“What are these flares doing to their atmospheres? Is there such a large flux of radiation and particles that the atmosphere is getting chemically modified, or perhaps completely eroded?”

Explosive flare activity

The team examined over 50 hours of data from ALMA. They used both the 12-meter main array and the smaller 7-meter Atacama Compact Array.

The result? They identified 463 flare events, each lasting between 3 and 16 seconds. The energy levels of these flares spanned from 10²⁴ to 10²⁷ erg, showcasing the star’s explosive character.

This is the first study of its kind to look at flare activity in the millimeter-wavelength range. Previous work focused mainly on optical flares. Now, with ALMA’s sensitive detection power, scientists have a much clearer view of what’s truly happening on – and around – Proxima Centauri.

“When we see the flares with ALMA, what we’re seeing is the electromagnetic radiation – the light in various wavelengths. But looking deeper, this radio wavelength flaring is also giving us a way to trace the properties of those particles and get a handle on what is being released from the star,” MacGregor explained.

Unusual flare patterns

By studying the frequency and intensity of flares, the experts mapped out what’s called a flare frequency distribution. This shows how often flares occur at different energy levels. In most stars, smaller flares are common, while large ones are rare.

Proxima Centauri doesn’t quite follow that rule. The team found a surprising number of large flares, even at the highest energies. These powerful flares had an odd pattern: their decay phase lasted much longer than their initial burst. That asymmetry gives clues to the physical processes driving them.

More importantly, it tells us that Proxima b – if it ever had a stable atmosphere – may have lost it long ago. Or worse, it may still be losing it flare by flare.

Refining the search for habitable planets

This study also made one thing clear: visible light isn’t enough. Millimeter-wavelength observations offer a deeper, more accurate picture. Flares look very different in this part of the spectrum. The frequency and energy distribution of flares seen by ALMA didn’t match those seen in optical studies.

“The millimeter flaring seems to be much more frequent – it’s a different power law than we see at the optical wavelengths. So if we only look in optical wavelengths, we’re missing critical information. ALMA is the only millimeter interferometer sensitive enough for these measurements,” said MacGregor.

That point reshapes how scientists evaluate stars with potentially habitable planets. If we rely only on optical data, we could misjudge whether a planet can sustain life. Radio and millimeter-wave observations add a new dimension – literally – to the search.

Proxima b may not be habitable

Proxima Centauri may be close, but it’s also dangerous. The very traits that make it fascinating – its size, structure, and flaring – also make it hazardous. While Proxima b may lie in the habitable zone, it doesn’t mean it’s truly habitable.

This research reveals more than just flare mechanics. It urges a reevaluation of what “habitable zone” means, especially around M dwarf stars like Proxima. Life needs more than the right temperature. It needs protection from the very star that gives it light.

In Proxima’s case, that light might come with a lethal price.

Image Credit: NSF/AUI/NSF NRAO/S. Dagnello

The study is published in The Astrophysical Journal. 

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