First fast radio burst detected below 300 MHz without targeting a known source.

Fast radio bursts are bright, millisecond-long radio flashes from outside our galaxy, but their origins remain unknown. Scientists have found thousands above 400 MHz, yet almost none at lower frequencies. At these low frequencies, space stretches out the signals into delays of tens of seconds and scatters them, making standard computer searches too difficult. To overcome this, researchers ran an untargeted survey that mapped broad areas of the sky with the Murchison Widefield Array. Using this imaging technique, they found an unexpected burst below 300 MHz. The discovery reveals that bursts occur at low frequencies just as often as at high frequencies. This shows these signals are not blocked or scattered away, proving low frequencies are great for studying burst environments.

Why it matters

For years, low-frequency radio telescopes could only find fast radio bursts by pointing at sources already known from higher frequencies. This detection shows they can find them blindly, meaning many more could be discovered. That matters because low-frequency signals carry unique information about the gas and magnetic fields around the burst's origin, helping astronomers understand what causes these mysterious flashes.

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