Two of the greatest mysteries of astrophysics today is dark matter and black holes.
Regarding dark matter, It’s simply not known what this material is, other than that it
has a profound effect gravitationally on the rest of the universe.
Candidates for what it could be include things like undetected subatomic particles that only
interact with other particles through gravity, and no other way.
But another candidate seems to stand out, or at least may for a portion of the missing
mass in the universe.
It’s the concept of primordial black holes.
And further, it’s plausible that one could be rather close to us.
Perhaps uncomfortably so.
The concept of a primordial black hole goes back to the 1960’s, and was first studied
in depth by Stephen Hawking in the early 1970s.
The idea is this, during the initial aftermath of the big bang, literally about one second
afte,r it’s thought, densities were such that black holes could form that were far
smaller than the stellar collapse black holes that we’re most familiar with today.
It’s thought that these types of black holes would generally not have been very long lived
in terms of the age of the universe under a certain mass, and should have mostly evaporated
by now.
However, if string theory is correct, this may lengthen the life of a tiny primordial
black hole.
But, above a certain mass, they might well still be around.
And with ones that are gaining mass in high density areas, they may have even served as
the seed cores for such things as supermassive black holes at the centers of galaxies.
But, the possibility of primordial black holes explaining dark matter recently took a major
hit.
Earlier this year an international team studied the Andromeda galaxy looking for microlensing
events.
The idea here is that the immense space between us and Andromeda should be full of primordial
black holes, and they would bend the light from the stars in Andromeda behind them in
such a way as to be detectable.
The results were interesting to say the least.
While they essentially eliminated primordial black holes as a major component of dark matter
through a lack of detections, they did see one that might have been a primordial black
hole.
This would suggest that yes, they exist, but they are significantly rarer than previous
estimates.
The team cautions however that certain other phenomena might account for this single detection,
and that further study is needed to determine if it is indeed a primordial black hole.
While contentious and hotly debated, as are many things regarding black holes, the concept
of primordial black holes is still out there, if not a major candidate for dark matter.
And if a recent paper ends up holding true, there may be one much closer than anyone ever
anticipated.
In a paper by Jakub Scholtz and James Unwin, they detail that the strange features seen
with some of the objects in the outer solar system may not be due to a ninth planet lurking
out there at all, but rather a primordial black hole.
This ties into the Planet 9 story, see the videos on this channel for that topic, and
this hypothesis is based on two gravitational anomalies of unknown origin that have been
detected in the outer solar system and in deep space.
One is a strange gravitational effect on certain transneptunian objects in the outer solar
system, leading to speculation that there may well be a ninth planet, or Planet 9, far
out in the outer solar system.
This planet has not yet been directly detected, if it’s there at all, but could represent
either a primordial planet ejected from somewhere the inner solar system early in its history,
or possibly even a captured rogue planet originally from somewhere else entirely.
Trouble is, it’s somewhat difficult to have a planet in the predicted orbit, though not
impossible.
The problem is that to form a planet that far out you need material, and the density
of material in the outer solar system isn’t very high, making it unlikely that a large
planet could form that far out.
Another option is that it might be either an ejected planet from somewhere else in the
solar system, or even a planetary core from a forming gas giant that was tossed out, but
again there are problems with the physics of how it managed to go into an outer orbit
without leaving the solar system entirely.
The last option for a planet is the captured rogue planet idea.
Space is very likely full of wandering planets that get tossed out of their original systems.
It may be that the solar system captured one, though it’s not very likely for such a thing
to have happened, but it’s certainly not impossible.
The search for Planet 9 continues, but there’s no reason to say that a primordial black hole
couldn’t be captured in the same way, and at similar odds.
The other anomaly is something else entirely.
These are distant, unexplained microlensing events.
Observed by the OGLE experiment, whatever is causing these, they are near the galactic
plane and are gravitationally microlensing objects behind them.
This could suggest a population of free floating planets passing by in deep space, which is
interesting enough, but could also be an indicator for primordial black holes.
The researchers noticed that the predicted mass of planet 9 is very similar to the predicted
mass of a primordial black hole, so the two ideas may be linked.
Perhaps most interestingly, the authors give a way for how such a black hole might be detected.
If it exists, the primordial black hole would be surrounded by accumulated dark matter.
If that dark matter were to annihilate with anti-matter, then x-rays and gamma rays would
be emitted, and should be detectable.
But even if it weren’t detected directly, if no evidence of planet 9 is ever found,
and the anomalies in the outer solar system continue to pile up, it will lead to a very
interesting mystery indeed.
On the other hand, if a tiny lack hole lurks in the outer solar system, literally on our
doorstep, it would revolutionize the study of black holes as we know it.
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently requesting that the
primordial black hole please vacate the solar system to at least 10 light-years distance,
or the nearest convenient empty patch of space nowhere close to Earth.
We have an enormous star that’s going to red giant, two huge scary looking gas giants,
asteroids, comets, interstellar oumuamuas passing through, gamma ray burst possibilities
… in other words, we have enough to worry about already.
We don’t need to add a lurking close black hole to the list.
Worries everywhere.
So if you can’t sleep at night, try one of my books which you can get at your favorite
online book retailer, and subscribe to my channels for regular, in-depth explorations
into the interesting, weird and unknown aspects of this amazing universe in which we live.