A recent research by team of astronomers revealed that strange planets could be orbiting each supermassive black hole out there in the vast universe.
Conditions are quite wild in the immediate vicinity of the event horizon of a supermassive black hole. But travel a little further, and other object, like the stars orbiting the supermassive black hole at the center of our galaxy, Sagittarius A*, may be snapped in its gravitational influence.
It is not just stars, according to a new paper. There might be planet oodles circling supermassive black holes, trapped in their gravitational grip, but far beyond immediate danger-tens of light-years away.
A team of astronomers led by Keiichi Wada of Kagoshima University in Japan, using planetary formation models, have shown, for the first time, a new class of planets that can form directly around a black hole.
And those planets would not be subject to the same limitations as those around a baby star forming planets.
“Our calculations show that tens of thousands of planets with ten times the Earth’s mass could be formed from a black hole for about ten light-years,” said astronomer Eiichiro Kokubo of Japan’s National Astronomical Observatory.
“There may be incredible planetary systems around black holes.”
Unlike baby stars, a large, dense disc of dust and gas can often surround black holes. In the case of a star, this rotating disc is left over from the matter that formed the star; planets can then form and continue to spin around their home star from that protoplanetary disc.
The fluffy dust aggregate that makes up the disc begins to cling together due to electrostatic forces, then collisions, and then gradually accumulates more and more grains until it is massive enough for gravitational forces to take over, et voilà-after a few million years, you have a planet.
Now, their discs contain a lot more dust when it comes to supermassive black holes-up to a billion times more than a protoplanetary disc, the researchers say. Similar dynamics of planet formation are likely to be present in the outer reaches of the black hole discs as you see in a protoplanetary disc.
Even black hole discs may be more efficient at planet formation at large distances than protoplanetary discs. This is because the planet’s seeds, called planetesimals, would not be subject to a protoplanetary disc phenomenon called the radial drift barrier.
This occurs when a planetesimal accumulates so much mass that its orbit is no longer stable, and it starts to move rapidly to an accreting star, meeting its eventual demise, according to dynamic modeling.
Compared to the orbital velocity of the rotating disc, the radial drift velocity would be negligible in a disc around a black hole. The inertia of this orbital velocity in any meaningful time period would prevent the planetesimal from moving to the black hole.
Planets also start to form in cooler regions of a protoplanetary disc, where the dust grains are coated with ice. The outer regions could be shielded from this radiation by the dust itself in a disc around an active black hole, blasting radiation from the intense heat produced by the friction of the spinning gas falling into it.
It would block the radiation because the dust is so dense, creating cool, planet-forming-safe pockets.
While the findings of the researchers are tempting, at the moment we are sadly unable to detect such planets hosted by black-hole. Nevertheless, one day, this research could lead to a whole new way of discovering alien worlds-and it could be quite a sight to behold.
The research was published in The Astrophysical Journal.