Planetary systems ‘of astonishing scale’ could exist on doorstep of supermassive black holes

Astronomers studying planet formation have proposed a bold new theory which suggests that entire planetary systems can form outside supermassive black holes across the universe.

Using existing planetary formation models, a team of astronomers, led by Keiichi Wada of Kagoshima University in Japan, suggest that a new class of planets can form directly outside (relatively speaking) supermassive blackholes, like the monstrous Sagittarius A*, which resides at the center of the Milky Way. 

These planets would form a mere tens of light-years away, caught by the black holes' gravity, but sitting far enough away to escape annihilation.

“Around black holes there might exist planetary systems of astonishing scale,” astronomer Eiichiro Kokubo of the National Astronomical Observatory of Japan said of the new research.

Similar to stars, black holes are often surrounded by large, dense discs of dust and gas, the leftover matter from the celestial objects' creation. Within these protoplanetary discs around stars, planets can and do form. 

However, unlike stars, supermassive black holes contain a lot more stray matter in their protoplanetary discs - up to a billion times more, according to Kokubo and his team. The researchers say that these planet 'seeds,' also known as planetesimals, could form thousands of planets, each with 10 times the mass of Earth. 

The distance between a supermassive black hole and its proprietary planetary system means it would actually create a more stable environment for planets to form than they would otherwise experience near a star. Many of these planets would also be protected from the extreme radiation emitted by the black holes by the icier sections of the dust cloud itself. 

While the theory does sound promising, we have yet to actually detect any such black hole-borne planets. Even so, it could open an exciting new realm of planetary exploration in the future. 

The team’s paper 'Planet Formation around Super Massive Black Holes in the Active Galactic Nuclei', was published in The Astrophysical Journal.

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