Back in 2016, physicist Stephen Hawking and billionaireYuri Milner revealed a plan for traveling to the stars. The so-called Breakthrough Starshot project is a $ 100 million program to develop and demonstrate the technologies needed to visit the nearest star system. Potential targets include Proxima Centauri, a system located about four light-years away, with several exoplanets, one of which resembles Earth.
Project Breakthrough Starshot
Hawking and Milner’s plan was toBuild thousands of tiny microchip-sized spacecraft and use light to accelerate them to relativistic speed — that is, close to the speed of light. A large fleet increases the chances that at least one of them will arrive safely. Each "star chip" is attached to a light sail the size of a badminton court, and then irradiated with extremely powerful ground-based lasers.
The laser movement has many advantages. The most important thing is that the spacecraft do not need any fuel, and therefore should not take extra weight with them. Also, with the help of acceleration of the light sail, you can accelerate the ship to 20% of the speed of light. In this scenario, the fleet will arrive at Proxima Centauri in less than 30 years.
The fantastically powerful lasers needed for such a mission will be particularly difficult and expensive to develop. An obvious question is born: is there another way to achieve relativistic velocities?
Today we have a kind of answer, thanksthe work of David Kipping, an astronomer from Columbia University in New York. Kipping came up with a new form of gravitational slingshot, the same technology that NASA used to send, for example, the Galileo spacecraft to Jupiter. The idea is to speed up the spacecraft, directing it next to a huge object, such as a planet. Thus, the spacecraft will take away part of the speed of the planet, accelerate with its help.
Gravitational slingshots work great formassive bodies. In the 1960s, physicist Freeman Dyson calculated that a black hole can accelerate a spacecraft to relativistic speeds. But forces on a spacecraft approaching such an object will most likely destroy it.
Therefore, Kipping offered a clever alternative. His idea is to direct the photons around the black hole and then use the extra energy they receive to accelerate the light sail. “The kinetic energy of a black hole is transmitted to the light beam as a blue displacement, and upon return, the photons not only accelerate the spacecraft, but also add energy to it,” says Kipping.
This process depends on an extremely powerful gravitational field around a black hole. Since the photons have a small, but still rest mass, this field is able to trap light in a circular orbit.
Kipping's work is based on a slightly differentThe orbit directing photons emitted by the spacecraft around the black hole and back is a kind of boomerang orbit. During travel, photons on the boomerang will receive kinetic energy from the movement of a black hole.
It is this energy that can accelerate the cosmicship equipped with a corresponding light sail. Kipping calls his idea "halo-engine". A halo engine transmits the kinetic energy of a moving black hole to a spacecraft using gravity. In this case, the spacecraft does not consume any of its own fuel in this process.
Because the halo engine uses motionblack hole, it is best applied to binary systems in which a black hole rotates around another object. Then the photons receive energy from the motion of the black hole at the corresponding points in its orbit.
And such an engine should work with any mass,which is significantly less than the mass of a black hole. Kipping says that mechanisms of the size of a planet are possible with him. Thus, a well-developed civilization can travel with relativistic speeds from one part of the galaxy to another, jumping from one binary system of black holes to another. “A developed civilization could use the concept of a light sail to achieve relativistic velocities and extremely effective motion,” he says.
The same mechanism can also slow downspaceship. So this advanced civilization will probably look for pairs of binary systems with black holes that will act as accelerators and decelerators.
The Milky Way contains about 10 billionbinary black hole systems. But Kipping notes that there will most likely be only a limited number of trajectories that link them together, so these interstellar highways are likely to be very valuable.
Of course, the technology needed toThe use of this concept is currently beyond the reach of humanity. But astronomers should be able to figure out where the best star highways are located, as well as search for techno-signatures of civilizations that can exploit them.
Well, maybe one day we can ride them. Would you ride? Tell us in our chat in Telegram.