Last year, the world reveled as astronomers announced they had witnessed for the very first time the merger of two neutron stars. The historic event, dubbed GW170817, also marked the first occasion for our telescopes to detect gravitational waves, or ripples in the fabric of space-time, emanating from the two colliding neutron stars.
Now, a new study on the gripping phenomenon, published yesterday in the Astrophysical Journal Letters, uncovered that the unprecedented astronomical event may be even more special than previously believed.
According to the recent findings, the GW170817 gravitational wave event has spawned a new object that could potentially be a black hole — the first-ever proof that colliding neutron stars can birth such a physical object, NASA reports.
“Astronomers have long suspected that neutron star mergers would form a black hole and produce bursts of radiation, but we lacked a strong case for it until now,” says study co-author Pawan Kumar, from the University of Texas at Austin.
The conclusion comes from telescope measurements taken by NASA’s Chandra X-ray Observatory days and up to months after the two neutron stars crashed into each other and merged to form something new.
The remarkable event was first discovered on August 17, 2017. According to NASA, the two colliding neutron stars were spotted in an elliptical galaxy called NGC 4993, which lies 130 million light-years away from our planet. The dazzling burst of light and gamma rays emanating from the massive explosion was picked up by NASA’s Fermi Gamma-ray Space Telescope, while the gravitational waves were detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in Livingston, Louisiana.
In the days, weeks, and months following the GW170817 event, Chandra scoured the skies in order to glean more data on the never-before-seen merger of neutron stars. The new study examined the Chandra X-ray data and inferred that the neutron stars merged into what seems to be a black hole — the lowest mass one ever discovered.
LIGO observations established that the newly-formed object spawned from the GW170817 gravitational wave event has a mass of about 2.7 solar masses (or 2.7 times the mass of the sun). This qualified it as either a giant neutron star, the most massive ever detected, or a very low-mass black hole, the lowest mass black hole in existence.
But what really helped scientists unravel the mystery and speculate the identity of the mysterious object were Chandra’s X-ray observations, which revealed that GW170817 emits a level of X-ray radiation far too low for the object to be a neutron star.
In fact, the X-ray level was found to be “a factor of a few to several hundred times lower than expected for a rapidly spinning, merged neutron star and the associated bubble of high-energy particles, implying a black hole likely formed instead,” stated NASA officials.
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Astronomers are planning further observations to settle the case once and for all. If the object continues to become fainter and is thereby unequivocally confirmed to be a black hole, this will prove that black holes can spark into existence from two neutron stars exploding independently from two different supernovae that were close enough for the gravitational waves to pull the stars together and make them merge.
On the other hand, if the mysterious object becomes brighter over the next couple of years and starts shooting out more X-rays, then astronomers will know for certain that what they’re dealing with is a massive, highly-magnetized neutron star.
Either way, the discovery will be undoubtedly a thrilling one, considering that, even if the object turns out to be a heavy neutron star, it will forever change everything we thought we knew about neutron star formation and how massive these objects can really get. As the Inquisitr previously reported, the record for the most massive neutron star is currently held by a “redback” pulsar dubbed PSR J2215+5135, which weighs 2.3 solar masses.
Study co-author J. Craig Wheeler, also from the University of Texas, explains that the historic GW170817 event remains a priceless source of information regardless of whether it spawned a black hole or a neutron star.
“GW170817 is the astronomical event that keeps on giving. We are learning so much about the astrophysics of the densest known objects from this one event.”