The nature of black holes, astrophysical objects so dense and gravitationally strong that they swallow up all matter and light that ventures too close to them, prevents scientists from seeing their interiors and forces them to use mathematics to “observe” their depths.
Now, researchers from Towson University and Johns Hopkins University have come up with a breakthrough that will provide scientists with a new way to sneak a peek through a black hole’s event horizon and see what lies beneath. While their new approach doesn’t actually let us see all that goes on inside a black hole, it could shed new light on their internal structures.
Currently, scientists use special coordinate systems to illustrate the structure of a rotating black hole, the authors explained, but this can distort the results based on particular set of coordinates selected by the observer. The most accurate way to depict a black hole’s properties, they noted, is by using a series of mathematical quantities known as invariants, which have the same value regardless of which coordinates are used by the researchers.
By plotting and computing all of the independent curvature invariants of rotating, charged black holes for the first time, the authors said that they were able to discover a more complex, intricate and beautiful structure within black holes than previously thought. They presented their findings this week at the 228th meeting of the American Astronomical Society in San Diego.
Technique could help explain why not all black holes have jets
As Kielan Wilcomb, who presented the findings, and colleagues James Overduin and Richard C. Henry also reported in a paper currently available online, their method also revealed tremendous variations in curvature between different regions of the internal structure of a black hole.
In a statement, the trio explained that the findings are timely in light of the recent detections of the very first gravitational waves by the LIGO and Virgo observatories. Those spacetime ripples, produced by a pair of distant black holes colliding, are now known to exist, but as Overduin and his colleagues said, since information cannot escape a black hole, we can’t look inside them.
Thus, scientists can only explore these phenomenon mathematically, the authors of this newly published study set out to find the best way to visualize black hole interiors using these methods. In general, they said that most black holes (those with mass, spin and electric charge) possess a total of 17 curvature invariants, but due to mathematical relationships with one another, only five of them are truly independent.
The simplest of those quantities, the Ricci scalar, is at the core of general relativity theory while a second, the Weyl invariant, plays an comparable role in an alternative theory called conformal gravity. This invariant is equivalent to a third, the Kretschmann scalar, that exists in black holes that have no electric charge (which is expected to be the case most of the time).
Fluctuations in this quantity’s value near the singularity inside a spinning black hole include regions of negative curvature that are usually associated with gravitomagnetism, a phenomenon involving the gravitational analog of ordinary magnetism, the authors noted. Gravitomagnetic fields, fed by rotational energy, are believed to generate the jets emanating from the polar areas of some supermassive black holes, and improved curvature mapping inside the event horizon may help scientists understand why some galaxies have these jets and other do not.
Image credit: NASA, ESA, and D. Coe, J. Anderson, and R. van der Marel