A glowing shape that looks like a musical treble clef, hidden behind the dust and stars of our own galaxy, was created by a supermassive black hole outburst and later revived by a crash between two galaxy clusters, according to a NASA analysis using the Chandra X-ray Observatory. The structure sits "almost directly behind the plane of the Milky Way," NASA said, a part of the sky astronomers have long struggled to study.

The object glows in radio waves, not visible light, so the "clef" only appears in maps from radio telescopes. Pairing those maps with X-ray data revealed that it lives inside a massive galaxy cluster no one had properly characterized before.

For skywatchers and space fans, the image is a striking reminder of how much remains hidden behind the Milky Way. For astronomers, it is a rare look at how cosmic collisions recycle old energy in a region of sky that is usually off limits.

A Musical Symbol Written in Radio Waves

The Treble Clef, catalogued as VLSS J0318.9+5755, was spotted in surveys by LOFAR, the Low Frequency Array, a European network of radio antennas. Its looping, filament-like shape gave it the nickname.

In NASA's composite image, radio data from LOFAR appear in red, X-rays from Chandra and the German eROSITA telescope reveal hot gas, and infrared data from the United Kingdom Infrared Telescope fill in stars along the line of sight. The X-ray glow showed that a galaxy cluster, a collection of hundreds or thousands of galaxies bound by gravity and filled with hot gas, hosts the radio source.

NASA's Chandra photo release for the object is dated Oct. 14, 2026. The paper also draws on new follow-up observations from the upgraded Giant Metrewave Radio Telescope in India, which measured how the radio glow changes across frequencies.

The research team, led by Andrea Botteon of Italy's National Institute for Astrophysics, described the object in a paper accepted by the journal Astronomy & Astrophysics and posted on arXiv.

Black Hole Energy, Faded and Reborn

The story unfolded in two stages — first, a supermassive black hole at the cluster's center erupted, blasting charged particles and magnetic fields outward at nearly the speed of light. Those particles produced bright radio emission that slowly faded over time as they lost energy.

Later, two galaxy clusters collided. The crash compressed and reenergized the old cloud of particles, making it shine in radio waves again. Shock waves from the collision may have helped. Astronomers call this kind of revived remnant a radio phoenix, because it rises from the fading ashes of an earlier outburst.

The paper suggests the swirling gas motions stirred up during the merger may have twisted the revived plasma into its filamentary, clef-like form. The same merger may also power a fainter, cluster-wide radio glow at the center, which the team lists as a candidate rather than a confirmed detection.

Reading a Collision in X-Ray Light

Chandra provided the key evidence for the crash — the team removed the smooth, oval glow of hot gas from the X-ray image to see what was left. The leftover emission was brightest to the left and right of the center, which suggests the two clusters collided along that axis.

NASA said the direct collision happened a few hundred million years ago, and the clusters are now moving apart. That timeline fits a picture in which the merger's aftermath is still shaping the radio structure today.

The Treble Clef is also extreme in another way. The arXiv paper reports that its radio brightness drops off unusually steeply at higher frequencies, a sign of very old, tired particles. That is why it shows up mainly at low radio frequencies.

Looking Through the Milky Way's Blind Spot

Most of the sky near the Milky Way's flat disk is hard to study because dust blocks visible light and crowds of foreground stars confuse the view. Astronomers sometimes call this region the Zone of Avoidance. Radio waves and X-rays pass through the dust far more easily, which is how this cluster came to light.

That makes the finding useful beyond one pretty picture. It also shows the value of combining telescopes that see different kinds of light, since no single instrument could have explained the Treble Clef on its own. Clusters hidden behind the galactic plane are undercounted in surveys, and finding them helps complete maps of how matter is distributed in the nearby universe.

There are limits to what this study shows. NASA's announcement did not give the cluster's distance, and some features, including the central radio halo, remain candidates. The explanation of a black hole outburst followed by a merger is the team's best interpretation of the data, not a direct observation of the events as they happened.

Chandra, launched in 1999, is managed by NASA's Marshall Space Flight Center in Huntsville, Alabama, with science operations run from the Chandra X-ray Center at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts. The researchers say the Treble Clef is a strong target for sharper, very low-frequency follow-up with the upgraded LOFAR2.0 network.

The bottom line is that a treble clef drawn in radio waves behind the Milky Way turned out to be the reborn remnant of a black hole outburst, revived by a galaxy cluster collision a few hundred million years ago. It is a vivid example of how combining radio and X-ray telescopes can reveal hidden structure in the universe.

What Readers Want to Know

What is the Treble Clef?

It is a radio-wave structure, catalogued as VLSS J0318.9+5755, whose looping shape resembles the musical symbol. It sits inside a galaxy cluster behind the Milky Way's disk.

Can I see it with a telescope?

No. It glows mainly in radio waves and is hidden behind our galaxy's dust, so it does not appear in ordinary telescopes.

What created the shape?

A supermassive black hole outburst left a cloud of energetic particles that faded, and a later collision between galaxy clusters revived and shaped it.

What is a radio phoenix?

It is an old, faded cloud of radio-emitting particles that has been compressed and reenergized, so it shines again.

When did the cluster collision happen?

NASA says the direct collision occurred a few hundred million years ago, and the clusters are now moving apart.

Which telescopes were used?

Chandra and eROSITA in X-rays, LOFAR in radio, and the United Kingdom Infrared Telescope in infrared.