Why is a solar system black

Planet 9 or the mini black hole in the solar system

ESO astronomers have discovered the closest black hole to Earth to date, 1000 light-years away, but our solar system could also have a tiny one with 5-10 times the mass of Earth

A few days ago, astronomers from the European Southern Observatory (ESO) and other institutes reported that they had discovered a relatively near-Earth black hole. It is "only" 1000 light-years away, making it the closest black hole to date, and an invisible part of a triple system that still consists of two visible companion stars.

The observations of HR 6819, initially considered a two-body system, in the southern constellation Telescopium with the FEROS spectrograph at the MPG / ESO 2.2-meter telescope in La Silla showed that one of the stars orbits an invisible object, the other Stern is far from the two of them. "An invisible object with a mass at least four times that of the sun can only be a black hole," says ESO scientist Thomas Rivinius.

So far, only a few black holes have been discovered in the Milky Way, which can be identified by the release of powerful X-rays. Scientists suspect that many more stars became black holes. The discovery of the silent black hole in HR 6819, which is really black and invisible because it does not "swallow" any matter, could guide the search for more, according to astronomers: "There must be hundreds of millions of black holes, but we only know about them very few. If we know what to look for, we should be better able to find them, ”says Rivinius. The astronomers who published their report in Astronomy & Astrophysics suspect that the LB-1 system, which is further away from the earth, could also be a three-body system.

Since Pluto is no longer considered a planet, but only as one dwarf planet among others, a planet 9 is speculated or searched for (in search of planet 9). It was not observed, but astronomers have deduced its existence from the existence of deviations in the orbits of trans-Neptunian objects (Sednoids). Planet 9 is located on the edge of the solar system, well beyond the orbit of Neptune.

For some it should be a big planet. But there were also suspicions that it could be a black hole, which is also the reason that it cannot be seen. Although the mass is five to ten times larger than that of the earth, it could be a tiny black hole - just 5 cm in size. So far, however, no observations have been made of interactions with surrounding dark matter that indicate its existence.

Now, as Discover Magazine writes, Ed Witten of the Institute for Advanced Study in Princeton, New Jersey, has come up with an original idea. If you can't see anything from Earth, then you could send a fleet of mini-spaceships in the direction you suspect the mini-black hole to be, and then watch to see if they unexpectedly deflect from their trajectory Would give clues to the effect of the black hole's gravity.

A five centimeter object would be difficult to find at such a great distance. An armada of tiny spaceships that cover a larger space and contain a chip that transmits their position data back to Earth, the deviation from some could make the hypothesis of such a mini-black hole more likely. Too bad that the swarms of mini spacecraft required for this do not (yet) exist.

This would require a laser beam that acts as a drive for the mini spacecraft and accelerates them further and further. A technique that the Breakthrough Starshot initiative wants to develop to explore Alpha Centauri. It would be necessary for the laser beam to accelerate the spaceships to a speed of hundreds of kilometers per second. The biggest problem for Witten is that the tiny spaceships would have to carry a high-precision clock with them: "A sufficiently accurate time measurement in a tiny spaceship should be the biggest obstacle for this project," says Witten.

But it is also questionable who should finance such a mission, the cost of which could run into the billions - just to prove a mini black hole or to falsify the hypothesis? (Florian Rötzer)

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