Although we have a pretty good idea that our galaxy contains a supermassive black hole at its core, there could be another — albeit rather exotic — explanation for our observations of Sagittarius A*. It might be a wormhole.
This is according to two researchers who explore the possibility in a new paper submitted to the arXiv pre-print service. Although their work is purely theoretical, Zilong Li and Cosimo Bambi of Fudan University in Shanghai have identified a specific emission signature surrounding their hypothetical wormhole, a signature that may be detected by a sophisticated instrument that will soon be attached to one of the world’s most powerful telescopes.
Sagittarius A* (or Sgr A*) is a region in the Milky Way’s core that generates powerful radio waves and astronomers have long suspected that it is the location of a black hole approximately 4 million times the mass of our sun. It wasn’t until astronomers were able to track stars orbiting close to the suspected black hole’s event horizon, however, that the supermassive black hole was confirmed to be there.
But supermassive black holes are a conundrum.
Now we know what signature our supermassive black hole generates, astronomers have discovered that the majority of other galaxies also possess supermassive black holes in their cores. Even when looking into the furthest cosmological distances at the youngest known galaxies, they also appear to host these black hole behemoths.
For a black hole to gain so much mass, it’s logical to think they need lots of time to pile on the mass — eating interstellar gas, stars and other galactic material. But to explain the earliest supermassive black holes in the youngest galaxies, there had to be some as-yet to be understood rapid growth mechanism.
According to Li and Bambi, however, to explain our observations of Sgr A* and other galaxies’ cores, a primordial consequence of Einstein’s general theory of relativity may be called into play instead, thereby sidestepping the puzzle of how supermassive black holes grew so big so quickly.
“While of exotic nature, at least some kinds of primordial WHs (wormholes) can be viable candidates to explain the supermassive objects at the center of galaxies,” they write. “These objects have no solid surface, and therefore they may mimic the presence of an event horizon. They would have been produced in the early Universe and grown during inflation, so they could explain their presence even at very high redshift.”
High redshift galaxies are the youngest galaxies we can observe; where the galactic light has traveled billions of light-years, with frequencies shifted to the reddest part of the electromagnetic spectrum.
The type of wormhole that can mimic a black hole could only have been formed during the Big Bang, exerting a mass millions of times our sun’s mass, possibly explaining why the earliest galaxies appear to have supermassive black holes in their cores; they may not be black holes at all, they could in fact be gargantuan wormholes, linking disparate regions of space and time. (Though whether they can be traversed would likely remain a mystery.)
This may sound like some theoretical fun and games bordering on science fiction, but Li and Bambi have identified a powerful new instrument that could be used to differentiate emissions from space plasma surrounding the Sgr A* black hole or hypothetical wormhole.
GRAVITY will soon be installed at the ESO’s Very Large Telescope (VLT) in the Atacama Desert in Chile and will be used to observe the galactic center with unprecedented precision. The researchers hope to analyze emission data from energized gases (or plasma) that could be found around the object inside Sgr A*. Should the object in fact be a wormhole, that plasma will generate a very different signature as the hypothetical wormhole will be physically smaller than a supermassive black hole.
By modeling a hot blob of plasma trapped in the warped spacetime surrounding a black hole and a wormhole, Li and Bambi noticed two very different emission signatures that both cases will generate. A wormhole would generate a “very narrow emission line,” whereas a black hole would have spectra that is “broad and skewed as a result of special and general relativistic effects,” they write.
It is rare that such exotic theories could be supported or disproved by an instrument that will be commissioned within a couple of years, but it will be very exciting to see whether the plasma emissions around the object in Sgr A* are more black hole-like or wormhole-like. And although the chances are slim, if the latter is detected, it could re-write our understanding of the Cosmos.