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Map of the position and speed of the Milky Way. The arrows show the position and velocity data of the 224 objects used to model the Milky Way. The solid black lines indicate the positions of the spiral arms of the Galaxy. The colors indicate groups of objects belonging to the same arm. The background is a simulation image. Acknowledgments: NAOJ
The Earth just accelerated 7 km / s (~ 16,000 mph) and was about 2,000 light years closer to the supermassive black hole in the middle Milky Way Galaxy. But don’t worry, this doesn’t mean our planet is plunging into a black hole. Instead, the changes are the result of a better model of the Milky Way based on new observational data, including a catalog of objects observed for more than 15 years by the Japanese radio astronomy project VERA.
The VERA program (VLBI Exploration of Radio Astrometry, by the way, VLBI stands for Very Long Baseline Interferometry) started in 2000 to map three-dimensional velocities and space structures in the Milky Way. VERA uses a technique known as interferometry to combine data from radio telescopes scattered across the Japanese archipelago to achieve the same resolution as a telescope with a diameter of 2300 km. Measurement precision achieved with this resolution, 10 micro-arc seconds is theoretically sharp enough to distinguish the cent of a dollar placed on the surface of the Moon.
Since the Earth is inside the Milky Way, we cannot back down and see what the Galaxy looks like from the outside. Astrometry, the accurate measurement of the positions and movements of objects, is a vital tool for understanding the overall structure of the Galaxy and our place in it. This year, the first VERA astrometric catalog was released, containing data on 99 objects.
Based on the VERA astrometric catalog and recent observations by other groups, the astronomers constructed a map of position and velocity. From this map, they calculated the center of the Galaxy, the point around which everything revolves. The map indicates that the center of the Galaxy and the supermassive black hole there are 25,800 light years from Earth. This is closer than the official value of 2,700 light-years adopted by the International Astronomical Union in 1985. The velocity component on the map indicates that the Earth orbits the galactic center at a speed of 227 km / s. This is faster than the official value of 220 km / s.
Now VERA hopes to observe more objects, especially those near the central supermassive black hole, to better characterize the structure and motion of the Galaxy. As part of this effort, VERA will participate in the EAVN (East Asian VLBI Network) consisting of a radio telescope located in Japan, South Korea and China. By increasing the number of binoculars and the maximum distance between binoculars, EAVN can achieve even greater accuracy.
“The first VERA astrometric catalog” by VERA partnership et al. appeared in the publications of the Japanese Astronomical Society in August 2020.
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