Our galaxy the Milky Way may not be the most ancient of the galaxies in the universe out there
but she is not that young and naive either she has experienced the death of its children and if
astronomers are to be believed it must have lost hundreds of billions of stars who completed their
life cycles but not all of them are gone entirely it is estimated that about one in a thousand stars
is massive enough to give birth to a black hole after dying then it is elementary my dear viewers
that there should be hundreds of millions of them scattered throughout the milky way galaxy
but they can be very shy to detect despite their ever hungry nature especially if they
are isolated however we have finally found one probably welcome the Factnomenal and
today let's find out if astronomers have finally found a free-floating black hole in our galaxy
black holes by their very nature can be very hard to detect especially if they are isolated after
all a black hole has such powerful gravity that light doesn't escape so we generally detect them
by their gravitational influence on other objects or by radiation created by the surrounding matter
that they are feeding on without nearby objects or accreting matter there could be hundreds of
millions of black holes throughout our galaxy that are essentially invisible to astronomers
however with the help of gravitational lensing a team at the University of California Berkeley
has found a gravity demon that is checking most of the boxes to be a loner black hole
gravitational lensing is a tried and tested method which is most commonly used to find
exoplanets in our galaxy the gravitational microlensing technique is based on Einstein's
general theory of relativity which states that massive objects cause space time to curve
and gravity is simply the curvature of space-time as light travels through space-time the theory
predicts that the path taken by the light will also be curved by an object's mass
gravitational lensing is a dramatic and observable example of Einstein's theory in action
with microlensing we're able to probe these lonely compact objects and weigh them this
is the first free-floating black hole or neutron star discovered with gravitational microlensing
Jessica Lu leader of the UC Berkeley team and associate professor of astronomy
thinks that we have opened a new window onto these dark objects which can be seen any other way there
is still a possibility that the astronomer team's classification of this cosmic object is wrong
Lu is playing it safe and believes that if their estimation is incorrect then this
object could very well be a neutron star and not a black hole neutron stars are also dense highly
compact objects but their gravity is balanced by internal neutron pressure which prevents further
collapse to a black hole whether a black hole or a neutron star the object is the first dark stellar
remnant an astral phantom discovered wandering through the galaxy unpaired with another star
the team also concluded that the likely population of black holes in the galaxy is 200 million pretty
close to what most theorists predicted but there is a bit of complication the uc berkeley
team wasn't the only group of astronomers who were keeping an eye on this microlensing event
but more on that later let's look at this prospective black hole for a minute now
the UC Berkeley team was able to spot the micro lensing event using the Hubble Telescope and the
possible rogue black hole is supposed to be give or take about 5 000 light years away from earth
with more precise measurements they were also able to determine an approximate mass
of this hard to detect object and that is where complications arise the estimated mass of the
invisible compact object is between 1.6 and 4.4 times that of the sun because astronomers think
that the leftover remnant of a dead star must be heavier than 2.2 solar masses in order to
collapse into a black hole the surprisingly low mass means there's a chance this object may not
actually be a black hole this wandering object suspected to be a black hole is located in the
carina sagittarius spiral arm of our galaxy despite the mass issue there are other clues
and characteristics of this object that makes the data lean toward it being a black hole in
2011 Hubble data indicated a star brightening and that's how the story of this object began earlier
observations led to the assumption that this event was caused by a foreground black hole drifting
in front of the star along our line of sight the star brightened and then subsequently faded over
several months back to its normal brightness has the entity suspected to be a black hole passed by
as you all intelligent viewers remember a black hole doesn't emit or reflect light and
that's why it cannot be directly observed but its unique thumb print on the fabric of space can be
measured through these microlensing events while astronomers have used gravitational microlensing
for approximately 30 000 events so far for studying objects such as stars and exoplanets
the signature of a black hole stands out as a unique feat among other micro lensing events
while the uc berkeley team was paying attention to the micro lensing event
they weren't alone a competing team from the space telescope science institute stsci in
baltimore was analyzing the same microlensing event dozens of astronomers on the competing
team have now worked for over six years studying this object their claim regarding the mass of this
so-called black hole is way off from team uc berkeley's finding as they claim that the mass
of the compact object is closer to 7.1 solar masses and therefore is indubitably a black hole
this is interesting because both teams use the same data photometric measurements of
the distance stars brightening as its light was distorted or lensed by the super compact object
and astrometric measurements of the shifting of the distant star's location in the sky
as a result of the gravitational distortion by the lensing object the two teams even named the object
differently moa 2011 blg 191 and ogle 2011 blg0462 or ob110462 for short another difference between
the two teams findings is the distance the uc berkeley berkeley-led team estimated that it lies
between 2280 and 6260 light years or 700 to 1920 parsecs away in the direction of the center of
the milky way galaxy and near the large bulge that surrounds the galaxy's central massive black hole
the stsci group estimated that it lies about 5153 light years or 1580 parsecs away the
sdscit mentioned that the very intense gravity of the black hole will stretch out the duration
of the lensing event to over 200 days also if the intervening object was instead a foreground star
it would cause a transient color change in the starlight as measured because the
light from the foreground and background stars would momentarily be blended together
but no color change was seen in observing this object and that is why the leader of
the stsci team kailash sahu is positive that the discovered cosmic object is a rogue black hole
until now star-sized black holes have been found only as part of binary star systems black holes
and binaries are seen either in x-rays revealed when material from the star falls onto the black
hole or by recent gravitational wave detectors which are sensitive to mergers of two or more
black holes but these events are rare jessica liu of the uc berkeley team has been looking
for free floating black holes since 2008 but she and her team specifically casey lam became
interested in this object in 2020 after the stsci team tentatively concluded that five microlensing
events observed by hubble lasted for more than 100 days and thus could be black holes for astronomers
this data is supposed to help them estimate the abundance of black holes better in the galaxy
which has been roughly estimated at between 10 million and 1 billion further study of ob110462
revealed that the lensing object seemed dark so it could not be a star the stellar brightening lasted
as long as 300 days and the distortion of the background star's position also was long lasting
searching for the black hole through microlensing is like searching for a needle in a haystack
as only one percent of detectable microlensing events are likely to be from black holes however
with the calculations followed by the discovery of ob110462 astronomers have new data that about
40 percent of microlensing events that last more than 120 days are likely to be black holes if the
two teams are correct and this object that they found is indeed a black hole our understanding
of black holes is about to be changed either how many of them are out there how fast they move or
how much their mass could be but are we sure that we have found a black hole and not a neutron star
luckily hubble has provided more data on the event in october 2021 however this set of data has only
been useful for eliminating other possibilities except for neutron stars and black holes
so we may need a little bit more effort from the aging hubble telescope and observation is
tentatively scheduled for fall 2022. there is also a matter of discrepancy in the findings of the two
teams but that could be due to the fact that the astrometric and photometric data give different
measures of the relative motions of the foreground and background objects astrometric analysis also
differs between the two teams that said both teams are hopeful that further observations would
help to clear all doubts and give us some solid results the existence of stellar mass black holes
has been known since the early 1970s to this date every black hole's mass has been surmised either
statistically through interactions in binary systems or the course of galaxies since stellar
mass black holes are usually found with companion stars this new object has piqued everyone's
curiosity and opened new paths to understanding our galaxy and black holes themselves determining
how many of these compact objects populate the milky way galaxy will also help astronomers
understand the evolution of stars and how they die perhaps this study will also reveal whether
any of the unseen black holes are primordial black holes that is according to some cosmologists the
black holes that were produced in large quantities during the big bang will we get another window to
the past of our universe or would this black hole help us understand the most mysterious object in
our universe better tell us in the comments and thanks again for watching Factnomenal
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