Mysterious Signals Keep Coming From Space. Scientists May Finally Know Why

Astronomers may finally understand why mysterious radio signals keep coming from space. A new study points to a pair of interacting stars as the source.

These signals, called long-period transients, are rare. They repeat slowly compared to other radio sources.

Decoding Cosmic Signals

ASKAP J1745 is a new source of these repeating radio bursts. It seems to come from two stars orbiting each other closely.

Scientists have been trying to explain these strange radio flashes for years. They were first found by accident when telescopes scanned the sky.

Only about a dozen of these unusual sources are known. Their origins have been a mystery.

A new study in Nature Astronomy reports the first time both radio and X-ray bursts have been detected repeating in sync with each orbit.

ASKAP J1745 is special because astronomers have identified its source. This is unlike 10 of the 12 known long-period transients. It's also valuable because multiple telescopes observed it, detecting different types of light.

This extra information about ASKAP J1745 is like the Rosetta Stone. It will help astronomers understand all long-period transients.

What Are Long-Period Radio Transients?

Long-period transients are objects in space that produce bright, repeating bursts of radio light. We know little about where most of them come from. Many are found near the dusty center of our galaxy, making them hard to see with visible-light telescopes.

Even with only a dozen found, they vary in type. Their radio bursts repeat every few minutes to several hours.

Some have pulsed regularly for over 30 years. Others turn off for days or go silent forever.

Where Do They Come From?

Astronomers first thought these transients were slowly spinning neutron stars, called pulsars. Neutron stars are dense cores left after massive stars explode.

The first few transients repeated about every 20 minutes. This is much slower than most pulsars, which repeat every few seconds.

Pulsars should stop making radio light when they spin down. So, radio bursts from such slow-spinning neutron stars shouldn't happen.

This led astronomers to look at other ideas, like white dwarfs. These are the cooling cores of less massive stars. Recently, some long-period transients were found in binary systems. These systems had a white dwarf and a smaller red dwarf star.

The ASKAP J1745 Discovery

ASKAP J1745 is a new long-period radio transient. It was found using the ASKAP radio telescope in Australia. It's the first of these sources identified as a "cataclysmic variable."

Cataclysmic variables are systems with two stars. One is a white dwarf. They orbit so closely that they interact. The white dwarf's gravity can pull material from the other star. These are also called accreting white dwarf binaries.

Another long-period radio transient was recently found with X-ray bursts. These bursts repeated at the same rate as the radio signals. But the source of the bursts and their timing was unclear.

Now, for the first time, observations from radio, X-ray, and optical telescopes have been combined. They show that ASKAP J1745 produces both X-ray and radio bursts with each orbit of its two stars.

In these fast-orbiting systems, X-ray light comes from material heating up as it flows onto the white dwarf.

The bright radio bursts were more puzzling. But knowing it's an accreting binary system helped explain them.

This type of pulsed radio light usually comes from energetic particles interacting with strong magnetic fields. Here, there are two stars with strong magnetic fields, thousands of times stronger than an MRI machine. Charged particles flow from one star to the white dwarf. This creates the perfect conditions.

What This Means for Astronomy

This discovery is unique because it provides more information across different wavelengths than any other long-period transient.

Like the Rosetta Stone helped decode ancient Egyptian symbols, ASKAP J1745 will help understand other long-period radio transients. These others lack information at different wavelengths.

ASKAP J1745 is the first long-period transient showing signs of accretion across the entire light spectrum. This stream of charged material is vital for creating the radio light detected from these systems.

Studying how long-period radio bursts are made gives scientists a new way to learn about extreme physics. This includes plasma flows and magnetic fields in conditions impossible to create on Earth.

Deep Dive & References

Periodic radio and X-ray emission from an accreting white dwarf binary - Nature Astronomy, 2026