# Astrophysicist Says 2.86 Million Earth-Like Planets Could Orbit a Black Hole

Monday, 11 June 2018 - 1:02PM
Monday, 11 June 2018 - 1:02PM
Image credit: Outer Places

If you had a degree in astrophysics, access to high-powered computers, and a love of sci-fi, you might do what Sean Raymond did: Create a model of a solar system that would simulate the conditions on Kalgash, the fictional planet from Isaac Asimov's novel Nightfall that only experiences night once every two millennia.

All Raymond had to do was create two concentric rings of stars, put an Earth-sized planet between the rings, and a big black hole at the center of it all.

Now, however, Raymond has stepped up his game big-time by creating a model for what is (by his own estimation) the "Ultimate Solar System."

Aside from creating fictional sci-fi worlds, the key question for Raymond is: How many potentially habitable planets could one system have?

It's the challenge at the heart of his long-running blog series that experiments with different configurations of stars, planets, orbits, and more. It turns out the answer is several million.

To pull it off, though, you'd need an incredibly specific set of conditions.

First off, you'd need a supermassive black hole (with a mass equal to 1,000,001 suns) at the center of your star system, orbited by a Sun-sized star at a distance of about 0.2 astronomical units (1 AU is the distance between the Earth and the Sun).

The energy output of the black hole-star combo would be about the same as our Sun, so the habitable range would be the same.

According to Raymond, there would be enough space for 689 orbit "rings" around this solar center, and each ring would be able to hold 4,154 planets—that adds up to 2.86 million planets orbiting a black hole.

Thanks to an astute observation by a colleague, however, Raymond realized that the star in this scenario wouldn't last too long.

To create some alternatives, he also created a model with a ring of nine stars around the black hole, then one with 36 stars orbiting on the outside of the planet rings.

Even after decreasing the number of planets in the system to 1 million, here's how Raymond describes living there:

"You would never feel alone in these systems. The other planets would loom huge in the sky! Neighboring planets are about ten times closer than the Moon (on an Earth-like orbit in systems 1 and 3). Earth is about 4 times larger than the Moon, so neighboring planets would be about 40 times larger in the sky than the full Moon. That's 20 degrees in the sky. That's about the size of a laptop computer held at arm's reach, only up in the sky!"

So there you have it. The uppermost limit to habitable planets in one solar system. Hopefully, the universe decides to meet us halfway on this and create a system with at least one habitable planet.