Black holes are the most daunting mysterious and dangerous things in the entire universe
the idea of getting pulled into one and getting spaghettified is enough to give you nightmares
now imagine hundreds of them in one place scared yet welcome the Factnomenal and today let's dive
headfirst into the cosmic swamps of the universe black hole swarms a groundbreaking discovery
in early summer during what could be described as the most fitting time a group of astronomers
planning to work on the European space agency's laser interferometer space antenna made an
astonishing discovery during black hole week what they found was like looking at a Rorschach test
in space made by the universe a swarm of black holes a globular cluster called NGC 6397 has been
orbiting our galaxy and is about 8,000 light years from earth with data gathered from Hubble, Gaia,
and the MUSE spectrograph the astronomers tried to detect imprints of an intermediate mass black hole
in the center of this core collapsed cluster interestingly black holes usually exist in two
extremes they are either stellar mass black holes that form when a single massive star collapses
or the supermassive behemoths millions to billions of times the mass of the sun which usually form
the epicenter of a galaxy intermediate mass holes like the one the astronomers were looking for
in the globular cluster have the gravitational heft of hundreds to tens of thousands of stars
among physicists they are thought to bridge the gap between the two extremes however as we know by
now these intermediate black holes are very rare only a few candidates have been identified to date
globular clusters are the primary candidates where we can find this rare breed of black holes that
are neither too small nor gargantuan clusters like the one orbiting our own galaxy ngc 6397
are concentrated assemblies of ancient stars that are nearly as old as the cosmos
the astronomers working on LISA are expecting the antenna to work in earth's orbit
as a gravitational wave detector that could harvest the signals of black hole collisions
and any other events or objects that ripple space-time going all the way back to the big bang
and while they were studying the data related to ngc 6397 what they found was nothing like an
intermediate mass black hole it was like looking at a cosmic swamp of sinkholes
in the collapsed core of ngc 6397 there wasn't just one black hole there were speculatively
many black holes concentrated together like a hive these stellar black holes could have
a total mass of about a thousand to two thousand suns and therefore the number of black holes in
this swarm could vary from a dozen to a couple hundred the reason behind this conclusion is
that when physicists tried to determine the distribution of the globular cluster's total mass
by using the velocity stars inside the cluster their analysis indicated that the orbits
of the stars are close to random rather than systematically circular or extremely elongated
researchers concluded that the invisible component can only be made of the remnants of massive stars
they added that the stellar corpses progressively sank to the cluster center
after gravitational interactions with nearby less massive stars if this finding proves to
be authentic it will very well define how the clusters came to be the way they are
but can they really co-exist another paper published soon after the one proclaiming the
existence of a black hole swarm disputed the claim and pointed at the origin of globular clusters
when the cluster first forms massive stars are born inside it and explode as supernovae rather
quickly leaving behind neutron stars and black holes which means there could have been several
hundred black holes in ngc 6397 a few million years after it formed as clusters are so dense
there won't be much room between these massive black holes and stars inside them
so when they pass each other the black hole will tend to lose orbital energy and sink to the center
while the star gains energy and moves outward because of the dynamic friction
the next few steps get complicated but as the black holes settle into the core
they capture each other to become binaries orbiting each other if a star passes them
that star gets a decent kick from the orbital energy of the two black holes orbiting each other
and the binary black holes will feel the jolt as well the push may end up thrusting them out
of the core and sometimes out of the cluster entirely because of such massive struggle for
space due to the gravitational tug of war between the black holes and stars the core
of the cluster will inflate making it larger as stars would be pushed away from the center
however what makes the cluster ngc 6397 so strange is that it does not have an inflated
core in fact its core is super compact which can only happen if there are no black holes there
yet the glaring question remains that the first study convincingly proved the population of dark
objects in the core of the cluster so if they are not black holes what could they
be well according to the contrasting paper these mysterious objects are supposed to be white dwarfs
white dwarfs are the low mass cores of stars like the sun after they die and eject their
outer layers they have a mass equal to the sun whereas black holes constitute at least three
to five times the mass of our sun and that's just the beginning of it the nearest white dwarf to us
sirius b has the mass of the sun but the size of the earth for comparison the sun is over 100 times
wider than earth therefore the gravitational tug of war inside globular cluster ngc 6397 is much
milder than we thought and that allows the core to be compact yet still have dark objects in it
based on this logic the contrasting claims against the presence of a swarm of black holes in ngc
6397 do seem irrefutable the best possibility could have been that the cluster may only
have a single black hole in its core and it would hardly be ten times the mass of the sun
this revelation may have denied the glory of harboring a black hole swarm to globular cluster
ngc 6397 but it is for better as the findings in the contrarian paper doesn't dismiss the idea of a
globular cluster harboring a swarm of black holes but rather refines it and improves the process
of searching for such space oddities by asking us to look for clusters with the inflated core
and the results showed up in no time in July 2021 we've found a globular cluster which
seems to be a perfect candidate to be housing a swarm of over 100 stellar mass black holes
Palomar 5 located around 80 000 light years away can be considered a fossil of the early universe
it's very dense and spherical containing roughly one hundred thousand to one million very old
stars some of them nearly as old as the universe itself palomar five is different from ngc 6793
it has both a very wide loose distribution of stars and a long tidal stream
spanning more than 20 degrees of the sky and that is why it has been gathering so much attention
recent evidence suggests that populations of black holes could exist in the central regions
of globular clusters and are careening stars away from the core of the cluster scientists ran a
simulation of palomar 5 and threw a significantly higher number of black holes than what should be
the predicted quantity the simulation displayed the orbital interactions that would have
slingshotted the stars out of the cluster and into the tidal stream in around a billion years
what remains of the cluster will consist entirely of black holes orbiting the galactic center this
suggests that Palomar 5 will dissolve completely into a stellar stream it also suggests that other
globular clusters will likely share the same fate eventually this explains why the star
cluster is trailed by very thin streams of stars stretching some 22 800 light years behind it
further study of the cluster revealed around 30 black holes in the core of palomar 5
but that was just the beginning until now we have found as many as a 124 black holes inside
Palomar 5. and as expected the core of Palomar 5 is indeed inflated or shall we say fluffy because
it is 10 times less massive and 5 times more spread out than most clusters of its kind and
at 11.5 billion years old Palomar 5 is well on its way toward dissolution astronomers and scientists
will continue to study these cosmic fossils to get a better understanding of the early universe
they may also stumble upon the secret of why the intermediate mass black holes are so rare and what
could be the reason behind black holes existing in such extreme groupings until physicists find
that out here's food for thought for you what would you name the swarm of black holes would
it be a collective name tell us in the comments and as always thanks for watching Factnomenal!