hundred times the mass of our sun what are called  stellar mass black holes or they're millions to  

billions of times more massive than our sun aptly  named supermassive black holes so what is going on  

here where are all the in-between sized black  holes and why does the scale range stop there  

could black holes be really tiny or even as new  research suggests stupendously large you may  

remember when the large hadron collider was first  coming online some alarmists claimed it would  

create a black hole that would destroy the earth  while microscopic black holes seem far-fetched  

there are some theoretical ways they could  exist but you'd need extra dimensions to do it  

gravity as we know it isn't strong enough  to compress subatomic particles small enough  

to make them collapse into a black hole because  that size is smaller than the smallest meaningful  

measurement of distance the plank length if  discovered microscopic black holes would change  

our understanding of how gravity works at the  quantum scale and even imply the existence of  

extra dimensions that amplify gravity's force so  microscopic black holes could be made in particle  

accelerators but they would also exist for only  the briefest of moments decaying in an octillionth  

of a nanosecond not exactly enough time to devour  the entire planet so if they do exist they're  

nothing to lose sleep over stellar mass black  holes though are very much real and we have a  

pretty solid understanding of how they form when  large stars run out of fuel they collapse and go  

supernova if the core they leave behind is more  than about three solar masses the star's remnants  

collapse in on themselves and a black hole is born  these black holes can grow by devouring nearby  

material or merging with neutron stars or other  black holes you might imagine if a stellar mass  

black hole was allowed to just keep accumulating  matter eventually it would balloon to the size  

of the supermassive black holes that we think  are at the center of almost all large galaxies  

but there's an upper limit to how fast matter can  fall into a black hole so growing that large would  

take billions of years since we've observed black  holes with billions of solar masses that formed  

within hundreds of millions of years of the big  bang something else must be at work the mechanism  

for how supermassive black holes come to be is one  of the great mysteries of astronomy there are a  

few competing ideas each with their own strengths  and weaknesses for example maybe they formed from  

large seed black holes that are already very  massive when they form and then they continue  

to grow as they suck in matter these large seeds  would be the remnants of stars as big as 250  

000 solar masses stars that large should be rare  making large seeds less likely another idea is  

they're the product of several intermediate-sized  black holes these intermediate-sized black holes  

could form in dense star clusters as stars  collide after formation they sink toward the  

center of a galaxy where they merge as i said  before though there seems to be a gap in the  

sizes of black holes there is very little evidence  that intermediate-sized black holes exist beyond  

supermassive black holes there could be even  more jumbo cosmic pits one recent suggestion is  

there could be black holes larger than a trillion  solar masses more than 10 times larger than even  

the very biggest black hole we've discovered  the researchers who proposed their existence  

dubbed them stupendously large black holes even  our explanations for supermassive black holes  

wouldn't account for these giants their existence  would require us to rethink how black holes form  

or maybe there just is an upper limit to how  big black holes can get black holes could  

run the gamut from the microscopic to the mind  meltingly massive but so far the only thing we  

know for sure is they exist in two size ranges  and we're not even certain how the larger size  

is possible there's no doubt scientists are going  to keep probing for black holes at all scales  

because black holes have not only captured light  but our imaginations too you might think that  

stupendously large black holes are the result  of when supermassive black holes combine but  

something called the final parsec problem makes  their merger impossible check out my video on that  

here all right wild hypothesis time where do you  think all the intermediate-sized black holes are  

let us know your thoughts in the comments be sure  to subscribe and i'll see you next time on seeker