A bright image of a newly identified candidate black hole light echo that could be one of the largest ever detected. (Image credit: Julian Shapiro, Chilescope T1)
ANAHEIM, Calif. — Even after a black hole at the center of a galaxy fades, its ghostly remains can remain visible in surrounding gas clouds, sparkling with residual radiation like wisps of smoke from a dying fire. Astronomers call these cosmic ghosts “light echoes,” and that’s what Julian Shapiro, a high school student, discovered while scanning the cosmos for traces of supernovae.
“The outer regions of the gas are ionized by the supermassive black hole, which leads to the formation of this echo,” Shapiro said in a presentation March 20 at the American Physical Society (APS) 2025 Global Physics Summit.
Shapiro, 17, is a student at the Dalton School in New York City. But beyond his studies and college choices, he is also an independent astronomer who speaks at international conferences, such as this week’s APS meeting.
Shapiro initially began analyzing data from the DECaPS2 survey, a catalog of the southern galactic plane taken by the Dark Energy Camera at the Cerro Tololo Inter-American Observatory in Chile, to look for debris from exploded stars in supernova remnants and planetary nebulae.
But when he zeroed in on one such object, he found that its structure did not match the thin filaments characteristic of supernova remnants and showed no signs of a supernova at its center. “It was quite a revelation to stumble upon this,” Shapiro told Live Science.
The object, which he believes to be a light echo, is located in a region of potential supermassive black holes. Using data from the South African Large Telescope, he found high levels of oxygen and ionized sulfur scattered in the region, both elements that point to impact material. All of these signs suggest that the object is the afterglow of a currently dormant black hole that once emitted radiation that ionized the surrounding gas, causing it to glow even after the black hole had gone quiet.
Epic echo
Shapiro currently estimates the light echo to be about 150,000 to 250,000 light-years in diameter — about 1.5 to 2 times the width of the entire Milky Way galaxy. If his estimates are correct, he believes it could be a genuine candidate for the largest light echo ever recorded.
“This object takes up a significant area of the sky, which makes it a little easier to get detailed images of it,” Shapiro said.
Echoes like the one Shapiro found could help us better understand the behavior of black holes at the centers of galaxies, says Sasha Plavin, a black hole researcher at Harvard University who was not involved in the study.
“I really like how thoroughly [Shapiro] analyzed these images,” Plavin told Live Science. “These galactic phenomena are always interesting, and I think these echoes are a great way to study them.”
Plavin is also interested in seeing how this new light echo compares to others — whether it happened faster or slower than known examples. “Putting this discovery in a broader context could be useful in the future,” he added.
As he continues to study the light echo, Shapiro hopes to learn more about its composition by measuring different regions of it. However, he is also excited to continue contributing to black hole science – even if this discovery came as a surprise to him.
“My involvement in this area of research has come as a bit of a surprise to me,” he said. “But I hope that this object in particular will help to expand our knowledge of galactic activity that we don't know much about.”
Sourse: www.livescience.com
