Astronomers have spotted a colossal explosion emanating from a pair of merging neutron stars lurking in the remains of an ancient cluster of galaxies. The unexpected “collision within a collision” could help answer “not one, but two” major astrophysical questions, the researchers claim.
In a new study, published March 10 in The Astrophysical Journal Lettersan international team of scientists revealed the discovery of a new gamma-ray burst (GRB) – one of the universe’s most powerful and most luminous explosions — firing a beam of radiation directly at Earth some 4.7 billion light years away.
The supercharged shock wave, called GRB 230906A, was detected in 2023 by the Earth-orbiting Fermi Gamma-ray Space Telescope and likely originated from two neutron stars – ultra-dense stellar remnants that pack the mass of a Sun-like star into an object just a few miles above – that were coalesce into a single massive unit. Such a merger can also fail ripples in the fabric of space-timeknown as gravitational waves, seeding their surroundings with valuable metals such as gold and platinum.
The article continues below
GRBs were discovered in the middle of supposedly empty space, with no clear origin in the visible light or radio spectra. This surprised the researchers, as this type of signal usually comes from the center of large galaxies, which The Milky Way.
But when the study team turned other telescopes — including the Hubble Space Telescope, the Chandra X-ray Observatory and Neil Gehrel’s Swift Observatory (all of which orbit Earth) — toward the signal, they found that the pulse of energy actually came from a never-before-seen tiny galaxy.
This mini-galaxy lies in a giant stream of gas and dust that stretches about 600,000 light-years across, which is about six times wider than our galaxy. The researchers have not yet measured the new galaxy’s exact size, but the star cluster is likely very small, given that it was not seen until now.
The giant gas stream is likely left over from when multiple galaxies crashed together and were torn apart in the early universe, the team said. The newfound mini-galaxy lies within a particularly dense patch of gas that would have been a prime place for new stars to form in the wake of this epic collision. The researchers predict that the progenitor stars that eventually gave birth to the merging neutron stars may have been born around 700 million years ago.
“We found a collision within a collision,” co-author of the study Eleonora Troyan astrophysicist at the University of Rome, said in a statement. “The galaxy collision triggered a wave of star formation that over hundreds of millions of years led to the birth and eventual collision of these neutron stars.”
Double cosmic mystery
The discovery of the GRB, combined with its location in a mini-galaxy, provides new clues to explain previous anomalous findings.
“Finding a neutron star collision where we did is a game changer,” lead author of the study Simone Dichiaraan assistant research professor in the Department of Astronomy and Astrophysics at Penn State, said in the statement. “It could be the key to unlocking not one, but two important questions in astrophysics.”
The first mystery to be solved is why we sometimes detect GRBs coming from places other than large galaxies, where star formation is much rarer. This is rare, but when it does happen, astrophysicists are often left scratching their heads. However, the new study suggests that GRBs may come from similar small galaxies that we cannot easily see.
“This discovery reveals new homes for these cosmic collisions and shows that they don’t just happen in large galaxies,” Dichiara and Troja wrote together in a paper in The conversation.
The other mystery that can be solved is why astronomers rarely find elements like gold and platinum, as well as other heavy metals, outside large galaxies. The researchers were unable to detect which metals were emitted by this particular GRB. However, as with the previous mystery, this explosion proves that it is possible for these metals to be seeded outside of large star-forming regions.
“It points to a new pathway for the spread of heavy metals where we least expect them,” Dichiara and Troja wrote.
Look at
