Space is sufficiently distorted in the presence of black holes that even light rays can curve around them multiple times. We may be able to witness several copies of the same thing thanks to this phenomena. While this has been known for decades, according to Albert Sneppen, a Niels Bohr Institute student, we now have an accurate mathematical expression. The result was just published in the journal Scientific Reports, and it is even more effective in realistic black holes.
You've
probably heard of black holes, those fantastic gravitational masses from which
not even light can escape. You may have also heard that around black holes,
space and even time act strangely; space is distorted.
Space
curves so much in the presence of a black hole that light beams are deflected,
and extremely close light can be deflected so much that it travels many times
around the black hole. As a result, when we observe a distant background galaxy
(or another celestial body), we may be fortunate enough to see the same image
of the galaxy numerous times, albeit distorted.
Galaxies in multiple versions
A faraway galaxy glows in all
directions; some of its light approaches the black hole and is weakly
deflected; some light approaches the hole even closer and circumvolves it once
before fleeing down to us; and so on. As we go closer to the black hole's edge,
we observe more and more replicas of the same galaxy.
How much
closer to the black hole do you have to look from one image to see the next
image? The result has been known for over 40 years, and is some 500 times (for
the math aficionados, it is more accurately the "exponential function of
two pi", written e2Ï€).
Calculating
this is so difficult that we didn't have a mathematical or physical intuition
for why it happened to be this exact factor until recently. Albert Sneppen, a
master's student at the Cosmic Dawn Facility, a basic research centre
affiliated with both the Niels Bohr Institute and DTU Space, has now
successfully demonstrated why.
"Understanding
why the visuals repeat themselves in such an attractive manner is a
tremendously beautiful thing. Furthermore, it opens up new avenues for testing
our understanding of gravity and black holes "Albert Sneppen gives
clarification.
Proving
anything mathematically is not only enjoyable in and of itself; it also brings
us closer to comprehending this amazing event. Because the factor
"500" is intimately related to how black holes and gravity work, the
image repetitions are now used to analyse and test gravity.
Spinning black holes
Sneppen's
method can also be modified to apply not only to "simple" black
holes, but also to rotating black holes, which is an entirely new feature. They
all do it, in fact.
"It
turns out that when it rotates really quickly, you don't have to get 500 times
closer to the black hole, but much closer. In fact, each image is now just 50,
5, or even 2 times closer to the black hole's edge than before "Albert
Sneppen explains.
Because
each new image requires looking 500 times closer to the black hole, the photos are
quickly "squeezed" into one annular image, as seen in the figure on
the right. The numerous images will be tough to observe in practise. However,
because "additional" images have more room as black holes rotate, we
may be able to observe the theory in the not-too-distant future. We can learn
not just about black holes, but also about the galaxies that surround them, in
this way:
The more
times light has to go around the black hole, the longer it takes to travel,
therefore images get increasingly "delayed." If a star bursts as a
supernova in a background galaxy, for example, the explosion will be visible
repeatedly.
Reference: Journal Scientific Reports
0 Comments