Black holes have forever been shrouded in mystery, their veil uncovering a deeper conundrum to be decoded each time we “seem to get somewhere.” However, recent times have witnessed a more active scene with black holes exhibiting stupendous occurrences, offering us a piece of this mystifying puzzle or rather, at the very least, a glimpse into a part of the actual science behind a black hole. The most recent event pertaining to this strange cosmic body could arguably be the most fascinating yet.
Around nine hundred million years ago, a black hole is said to have released a terrible belch that echoed through the lone universe. This “burp” of sorts resulted in ripples resonating through the fabric of space-time (yes, we are reminded of Doctor Who). Interestingly, these ripples from a time unknown passed through the earth on August 14th, 2019 and with it, provided the scientists back at home some stellar evidence and information about the enigmatic universe!
The most obvious thought that comes to mind questions the inception of these ripples and the cause of the terrible belch. After much study, it was detected that the occurrence, called S190814bv, was likely triggered by the collision of a black hole and a neutron star. Neutron stars are essentially highly dense material or rather, leftovers of an exploded star. Scientifically, such binary systems are known to exist but nobody had expected a spectacle of such order to pose the possibility of being observable on mere telescopes used in scanning different wavelengths of light.
Astronomers had predicted the existence of potential ripples, known as gravitational waves, emerging from the merged black hole and neutron star. These ripples in the fabric of the cosmos were predicted more than a century ago by Einstein’s general theory of relativity, which suggested that the collision of two extremely massive bodies would cause the very fabric of the universe to wrinkle.
This isn’t the first time observatories have picked up gravitational waves resulting from mergers. The first gravitational wave was noticed in 2015 when the LIGO observatory picked up the signal of two black holes becoming one. Since then, LIGO in collaboration with Virgo observatory (its European counterpart) has detected other black hole mergers along with the collision of two neutron stars. The very recent signal marks the third time a phenomenon of such nature is being recorded.
Curiously, another recent occurrence mimicked a neutron star – black hole merger. On the 26th of April, 2019, scientists observed a phenomenon that very much resembled the current event, in its workings. However, it was deemed less compelling due to the existence of a one-in-seven chance of the noise emerging from Earth. False alarms corresponding to the April signal are expected to pop up once every 20 months. Reasonable evidence suggests that S190814bv is indeed not of this world. One might think; why not wait for a false alarm resembling S190814bv to confirm its legitimacy? The scary catch? You would have to wait longer than the age of the universe.
“This is something to get much more excited about,” says LIGO team member Christopher Berry, a physicist at Northwestern University. “It’s much more likely to turn up a real one, so that means it’s worth investing more time and effort.”
With so much compelling evidence in the bag, the next step would be to track down the origin of S190814bv. LIGO and Virgo have closed in on an oval patch of sky about eleven times wider than the full moon—making it possible for telescopes to follow up for unusual flashes of light. Instruments from across the world have joined in and have been encouraged to halt their scheduled observations in order to capture and observe this cosmic relic.
“It’s very exciting,” says Aaron Tohuvavohu, the observatory duty scientist for NASA’s Swift telescope, which has been searching for flashes of x-rays and ultraviolet light in the same patch of sky as the gravitational wave signal. “I didn’t sleep all night, and I’m very happy to do that.” Witnessing the afterglow from the collision would propel astronomy into a different era marking the possibility to visually behold the innards of a neutron star for the very first time in history. This could put the relativity theory to test in wonderful ways.
However, there are chances that the observatories might not be able to see a glow as neutron stars and black holes don’t always give off light, depending on how the two objects’ masses compare. More comparable masses of the two indicate a longer time required for the neutron star to spiral down the unknown depths of a black hole. This lets the pair orbit each other in closer proximity giving the black hole more opportunity to gravitationally shred the neutron star.
The visual spectacle that subsequently arises may be captured by a telescope. However, in the event that these two bodies have contrasting masses with the black hole being significantly larger, the dark giant gulps the star with not much opportunity for anything. Keeping in mind the recent events, scientists are in the midst of calculating the proportions of these bodies to determine if anything can be caught visually.
Conversely, another theory suggests the possibility that S190814bv might not be a neutron star at all. Seems a bit mind-boggling now after all that story eh? The scientists have something to say and we ought to hear them out. Anything below three times the mass of our sun is considered a neutron star. Anything more than five times the mass of our sun is considered a black hole. In this case, the smaller object in S190814bv is estimated to be less than three solar masses. Theoretically, smaller black holes are known to exist but strangely, we have never encountered one. What if S190814bv is a proof of this theorized anomaly?
“There’s really two mysteries that this event might tell us about,” Berry says. “What is the maximum mass of a neutron star, and what is the minimum mass of a black hole?” Weeks of study and the observation of the subtle features of the gravitational waves could indicate the true nature of the speculated neutron star. Either way, the discovery of any one of these theorized phenomena is nothing short of revolutionary. It marks a huge step in our way towards decoding the cosmic domain and the results from the study of this recent event, as Berry says, can only be a “win-win situation.”