A new class of exoplanet could exist in the neighborhood around supermassive black holes, with researchers proposing the existence of complex worlds known as ‘blanets.’

According to modelling by a Japanese team of researchers, a safe zone exists around each supermassive black hole which could well be occupied by hundreds, if not thousands of these black-hole planets.

“Our results suggest that blanets could be formed around relatively low-luminosity active galactic nuclei during their lifetime,” the researchers write. 

Keiichi Wada of Kagoshima University and his team suggest that these blanets form around newly-emerging stars in much the same way as planets do: a vast gas cloud collapses in on itself, begins spinning, firing material outward and generating a disc of material which then feeds it. Some of the material flies further out, eventually cooling and taking up a stable orbit before forming planets. 

A similar process could occur in the accretion disc of a black hole, wherein larger clumps of material grow larger and larger.

Eventually one such clump goes rogue after growing big enough and colliding with others, breaking free from the enormous gravity and reaching a point of relative stability where it can cool and form a planet (after about a million years or so).

The scientists even suggest that blanet formation might be more efficient than their planetary counterparts, owing to the crushing authoritarian gravity of a supermassive black hole, which dwarfs that of a star.

Given that these are supermassive black holes, blanets would also dwarf their planetary counterparts formed by stars, as the mass involved is so much greater. 

Assuming a black hole of one million solar masses, roughly 13 light-years out, blanets of between 20 and 3,000 Earth masses could theoretically form in stable orbits.  

We already know that black holes can reach up to 10 million solar masses, which would mean that, according to Wada’s team’s hypothesis at least, some of these blanets could reach brown dwarf territory – not quite a gas giant and not quite a star, but massive enough that they fuse deuterium in their cores, stopping just short of hydrogen fusion. 

Owing to the distances to supermassive black holes and the gravity they exude on their surroundings, we can’t actually detect any blanets (yet), so they’ll remain hypothetical for now, joining objects like moonmoons (moons of moons) and ploonets (rogue moons of large exoplanets that boast their own orbit independent of their original host planets), which may exist but have yet to be found.

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