Written by: Zhang Hua
The wormhole is a fast channel connecting the remote space-time region. This mysterious structure, according to the theory of general relativity, is the dream of many people to realize the time-to-air travel. But in the real world, scientists have not yet confirmed the existence of the wormhole, let alone through the wormhole.
So, if wormholes really exist, based on observable physical effects, can humans find their traces?
In a study published in Physical Review D, Professor Dai Dechang from the school of physical science and technology of Yangzhou University and D. Stojkovic from the State University of New York at Buffalo proposed that if there is a wormhole, thenThe physical effect of the wormhole can be observed by the acceleration of the stars near the black hole.
Looking for wormhole from gravitational field
No matter what kind of wormhole model, wormhole always connects two black holes, so the gravitational field can be transferred from one black hole to another through wormhole. The disturbance of the gravitational field provides the observation object for the scientists to find the wormhole.
According to this idea, in this paper, the author constructs a simple。 In this model, there is a star around the black hole at the end of the wormholeElliptical orbit motionAround the black hole at the other end is a black holeApproximate circular motionStars.
Because of the transmission of wormholes and the change of gravitational field of stars in elliptical motion, the orbits of stars in approximate circular motion will eventually be affected byGravitational perturbation。 It is this perturbation that constructs an indirect observation of wormholes.
In an interview with the New York Times, Stojkovic described it as follows:
So, how to make quantitative observation for the disturbance through wormhole?
In this paper, they construct a wormhole, which connects two black holes (regardless of the relationship between wormhole and negative energy density, assuming that wormhole really exists).
Through a series of detailed estimates, the researcher finally got a simple but crucial formula:
For a star moving in a circle near the second black hole, it will be affected by the gravitational field of the star near the first black hole, that is, gravitational perturbation. Gravitational perturbation results in the change of acceleration of star motion. This formula describesAcceleration variation。
To the right of the formula,AAnd RP, which are the semi major axis and the semi minor axis of its orbit. RTwoIs the radius of a star moving approximately in a circle. R is the radius of the wormhole.
Therefore, for the change of acceleration,Indirect observation of wormhole。 Although this is not a direct observation of wormholes, it is just as a scientific method to infer the existence of gravitational waves through orbit attenuation between two stars before directly detecting gravitational waves.
Looking for evidence in the center of the galaxy
In the center of the galaxy, there is a black hole with a large mass. The mass of this black hole is about 4 million times that of the sun.
This black hole is called Sagittarius A *. Moreover, near Sagittarius A *, there is a blue star, S2, moving around it in a nearly circular motion.
The track period of S2 is 15.56
According to the paper of Professor Dai and his collaborators, as long as the acceleration of S2 is accurately measured, the wormhole can be indirectly observed. (assuming that the black hole in the center of the galaxy is connected to another black hole through a wormhole, and that there are stars around it.)
Astronomers have been observing the orbit of S2 since 1992. According to the observation results in May 2018, at that time, the orbit of S 2 is very close to Sagittarius A *, the distance between the two is about 20 billion kilometers (about 120 astronomical units), and the orbit speed is about 7650 km / S (about 2.55% of the speed of light).
On earth, two research groups used the Keck telescopes and the very large telescope (VLT) to track S2. To locate the star more precisely, researchers used state-of-the-art adaptive optics technology, which effectively counteracts the distortions caused by the earth's atmosphere.
The team used four VLT telescopes as interferometers to combine the collected light with a resolution equivalent to a 130 meter diameter super telescope. This kind of interference technology is essentially similar to that of the first black hole photo taken recently.
Finally, with these technologies, researchers can track the apparent path of S2 star in the sky, and measure its radial velocity (also known as apparent velocity) and acceleration towards or far away from the earth through the Doppler frequency shift of the star. Finally, the researchers measured the acceleration of S2 star accurately,The accuracy of the measurement is up to 10-4M/sTwo。
High resolution measurement expected
However,Such accuracy is not enough for observation of wormholes。 In this paper, the researchers point out that after several years of research, astronomers can measure S2's orbit more accurately.
Dai Dechang said:Ten-6M/sTwoOnly then can we determine whether the central black hole in the Milky way is connected to another through one wormhole.
Therefore, from the current measurement accuracy, the measurement accuracy of S2 star acceleration is not enough to observe the physical effect of wormhole, but with the improvement of measurement accuracy, the future is not entirely hopeless. Whether the wormhole can be observed in this way or not, this paper formally puts forward the wormhole observation as a physical subject, which is a great progress in thinking.