Distance to sagittarius a*
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Distance to Sagittarius A* – Galactic Center Distance Measurements
Modern Parallax and Astrometric Measurements of Sagittarius A*
The most precise and direct measurement of the distance to Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, comes from trigonometric parallax observations. Recent results using the VERA radio interferometry array measured the parallax of Sgr A* to be 117 ± 17 micro-arcseconds, which corresponds to a Galactocentric distance of 8.5 kpc (kiloparsecs), with an uncertainty range of +1.5 to -1.1 kpc . This value is consistent with other modern measurements and is widely accepted as the standard distance to the Galactic Center.
Stellar Orbit Analysis and Consistency with Parallax
Observations of stars orbiting very close to Sgr A* have provided independent confirmation of this distance. High-resolution imaging of stellar orbits, such as the 15.2-year orbit of the star S2, has allowed astronomers to fit Keplerian orbits and derive the mass and distance to Sgr A*. These studies consistently find a distance of about 8 kpc to the Galactic Center 38. The agreement between parallax and stellar orbit methods strengthens confidence in this value.
Historical and Early Estimates
Earlier studies, before the advent of high-precision astrometry, estimated the distance to Sgr A* using indirect methods such as hydrogen absorption and the distribution of interstellar gas. These early estimates placed Sgr A* at a distance of 3–4 kpc, but these values are now known to be underestimates due to limitations in the data and methods available at the time .
Distance to Nearby Structures and Context
The distance to Sgr A* is distinct from the distance to other objects in the region, such as the Sagittarius Dwarf Galaxy, which is much farther away at about 24.8 kpc . Studies of clusters and features near Sgr A*, like the IRS 13E cluster, also rely on the established 8 kpc distance for context and further analysis .
Summary of Current Consensus
Current research, using both direct parallax and stellar orbit measurements, places Sagittarius A* at a distance of approximately 8–8.5 kpc (about 26,000–28,000 light-years) from Earth 368. This value is now the standard for studies of the Galactic Center and is crucial for understanding the structure and dynamics of the Milky Way.
Conclusion
The distance to Sagittarius A* is now well established at about 8–8.5 kpc from Earth, thanks to precise parallax measurements and detailed studies of stellar orbits. This distance underpins much of our understanding of the Milky Way’s structure and the behavior of its central supermassive black hole 368.
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