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The distance between our solar system and Sagittarius A *, the 4 million solar mass black hole at the center of our Milky Way galaxy, is about 25,800 light years, or about 1,900 light years longer than the ‘previous estimate, according to an analysis of data from the Japanese project VLBI (Very Long Baseline Interferometer) VERA (VLBI Exploration of Radio Astrometry).
Position and speed map of the Milky Way; arrows show position and velocity data for 224 objects used to model the galaxy; solid black lines show the positions of the spiral arms of the galaxy; the colors indicate groups of objects belonging to the same arm. Image credit: NAOJ.
“Because Earth is located inside the Milky Way, we cannot step back and see what our galaxy looks like from the outside,” said Dr. Tomoya Hirota, astronomer at the Mizusawa VLBI Observatory. at the National Astronomical Observatory of Japan and Department of Astronomical Sciences of SOKENDAI, and colleagues in the VERA collaboration.
“Astrometry, the precise measurement of the positions and movements of objects, is an essential tool for understanding the overall structure of the galaxy and our place in it.
“VERA was launched by the National Astronomical Observatory of Japan in the 2000s,” they added.
“The project was designed to focus on VLBI astrometric observations to reveal the 3D speed and spatial structures of the Milky Way.”
“These were four 20m radio telescopes in Japan: at Mizusawa, Iriki, Ogasawara and Ishigaki-jima stations.”
Using data from the first VERA Astrometry Catalog, astronomers modeled the structure of the Milky Way to estimate fundamental parameters such as the distance to the galactic center and the speed of the Sun around it.
“Our results suggest that the center of the Galaxy, and the supermassive black hole that resides there, are located 25,800 light years from Earth,” they said.
“This is closer than the official value of 27,700 light years adopted by the International Astronomical Union in 1985.”
“The speed component of the map indicates that the Sun is moving at 227 km / s as it orbits the galactic center. This is faster than the official value of 220 km / s. “
VERA researchers now plan to observe more objects, especially those close to Sagittarius A *, to better characterize the structure and movement of the Milky Way.
“As part of these efforts, VERA will participate in EAVN (East Asian VLBI Network) comprising a radio telescope located in Japan, South Korea and China,” they said.
“By increasing the number of telescopes and the maximum separation between telescopes, EAVN can achieve even higher precision.”
The VERA catalog was recently published in the Publications of the Astronomical Society of Japan.
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Tomoya hirota et al. (VERA collaboration). 2020. The first VERA astrometry catalog. Publications of the Astronomical Society of Japan 72 (4): 50; doi: 10.1093 / pasj / psaa018
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