In our search for alien life, stars may be distorting their signals

The only place we know for sure that life exists is right here on Earth. But when we look out at the vastness of space – our neighboring planets and their moons, and the billions of others thought to exist in solar systems – it’s hard not to wonder whether life exists elsewhere in the universe.

Although there is no single accepted definition of life, scientists agree on some key clues. Gases such as oxygen, carbon dioxide, and methane in a planet’s atmosphere can serve as potential indicators of life.

But there is also a small field of research that is looking for signs of alien life without relying on biology at all.

Known as the Search for Extraterrestrial Intelligence (SETI), the effort looks for technological signatures – evidence of technology developed by intelligent beings, such as electromagnetic signals – that stand out from the natural background noise of the universe.

Unlike the rumble of black holes or the whistles of solar winds, these signals would be structured in ways that suggest artificial origins, much like the radio and television broadcasts Earth sends into space.

If other intelligent life forms develop similar technologies, they may also inadvertently leak signals that our antennas may one day detect.

But a search The study, published in March in The Astrophysical Journal, points to an overlooked complication in this type of discovery: Space weather from the stars, where potential signals originate, can interfere.

Since the earliest days of the search for intelligent life, scientists have focused on a particular type of transmission, known as a narrowband signal – a beam of energy so tightly focused at a single frequency that it resembles a needle, says Vishal Gajjar, lead author of the study.

Gajjar is a staff astronomer at the SETI Institute, a nonprofit based in Silicon Valley dedicated to understanding the origins of life.

He says narrowband signals have become a prime target because they are unlikely to originate from known natural astrophysical processes, especially when they are found more than once in the same location, raising the possibility that they could be generated by distant intelligent life.

A signal lost in the noise

But despite decades of searching, scientists have encountered massive radio silence – prompting them to ask whether a fundamental property of planets orbiting stars could distort signals.

Every star, including our own Sun, says Gajjar, is surrounded by an interplanetary medium: a chaotic mix of plasma and magnetic fields stirred by stellar winds, flares, and sometimes even more violent explosions. Disruptive coronal mass ejection from the host star.

If a narrowband signal passes through it, especially when it’s overcast, it can get quite wide, making it wider and flatter than most devices, he says.

His takeaway? “We need to adjust our search strategy.”

To understand how the stars might influence the discovery, Gajjar and his team turned to a natural laboratory: spacecraft in our solar system.

Radio transmissions between Earth and these probes already travel through the Sun’s turbulent plasma and solar wind and offer real-world examples of how narrowband signals are altered.

By analyzing these broad and flat transmissions, the researchers calibrated models explaining how a star’s outflow reshapes the signal’s spectrum.

They used their findings to develop a framework to estimate how much a star might interfere with transmissions in different systems.

Observations of our own Solar System confirm that narrowband signals are often broadened under the Sun’s chaotic influence, and Gajjar’s team concluded that similar effects are likely to occur in the Milky Way.

“If (signals from alien life) are originating from a planet around a star, they will be spectrally broadened,” Gajjar said.

He says the study also shows that space weather varies widely between stars, with some environments far more disruptive to narrowband signals than others.

M dwarf stars, which make up about three-quarters of the galaxy, are a prime example.

These small, active stars are incredibly long-lived – no star ever formed in the universe has died – making them abundant and potentially excellent hosts for planets where life could evolve.

But their strong magnetic activity and frequent flares can cause signals to become weak and widespread, making them far more difficult to detect from Earth.

Rethinking the search for intelligence

Gajjar says the study shows that looking for “needle-like” signals is unlikely to be successful.

Instead, instruments will need to be adapted to detect broader, fainter signals, he says, because stellar turbulence can amplify a transmission – from 1 Hz to 10 Hz – reducing its intensity by about 94 percent.

Despite these challenges, Gajjar remains optimistic about the discovery of life beyond Earth.

Advances in technology now allow instruments to scan wider bandwidths and analyze signals that was impossible just a few decades ago.

Additionally, Gajjar says that understanding what the needle looks like when deformed will make his job “a little easier.”

Combined with artificial intelligence and high-powered graphics processing units, researchers can analyze more data than ever before.

“I think our chances of finding life have definitely increased,” he said.