Neptune♆

Blanet: A new class of planet that could form around black holes

The dust clouds around supermassive black holes are the perfect breeding ground for an exotic new type of planet.

Blanets are fundamentally similar to planets; they have enough mass to be rounded by their own gravity, but are not massive enough to start thermonuclear fusion, just like planets that orbit stars. In 2019, a team of astronomers and exoplanetologists showed that there is a safe zone around a supermassive black hole that could harbor thousands of blanets in orbit around it.

The generally agreed theory of planet formation is that it occurs in the protoplanetary disk of gas and dust around young stars. When dust particles collide, they stick together to form larger clumps that sweep up more dust as they orbit the star. Eventually, these clumps grow large enough to become planets.

A similar process should occur around supermassive black holes. These are surrounded by huge clouds of dust and gas that bear some similarities to the protoplanetary disks around young stars. As the cloud orbits the black hole, dust particles should collide and stick together forming larger clumps that eventually become blanets.

The scale of this process is vast compared to conventional planet formation. Supermassive black holes are huge, at least a hundred thousand times the mass of our Sun. But ice particles can only form where it is cool enough for volatile compounds to condense.

This turns out to be around 100 trillion kilometers from the black hole itself, in an orbit that takes about a million years to complete. Birthdays on blanets would be few and far between!

An important limitation is the relative velocity of the dust particles in the cloud. Slow moving particles can collide and stick together, but fast-moving ones would constantly break apart in high-speed collisions. Wada and co calculated that this critical velocity must be less than about 80 meters per second.

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Red Spots On Jupiter.

Credit M Wong and I de Pater

Moon (Jun. 23, 2020)

新幹線と富士山 (via かがみ～)

Saturn and Neptune by Voyager II

A rendering (Motion Edit) of a thunderstorm, based on a single photograph of a cumulonimbus cloud lit by a lighting, captured by night from an airliner at 40,000ft (12,000m), visualize a towering cumulus convection emerging from an altocumulus cloud cover.

An altocumulus cloud cover from below.

And the angel said, “DO NOT BE AFRAID.”

The faint rings of Uranus, shot in 1986, are made of countless fragments of water ice containing radiation-altered organic material.

Credit: NASA/JPL/Michael Benson, Kinetikon Pictures

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