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Stars Lensed by the Supermassive Black Hole in the Center of the Milky Way: Predictions for ELT, TMT, GMT, and JWST

Michałowski, Michał J. and Mróz, Przemek (2021) Stars Lensed by the Supermassive Black Hole in the Center of the Milky Way: Predictions for ELT, TMT, GMT, and JWST. Astrophysical Journal Letters, 915 (2). Art. No. L33. ISSN 2041-8205. doi:10.3847/2041-8213/ac0f81.

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Gravitational lensing is an important prediction of general relativity, providing both its test and a tool to detect faint but amplified sources and to measure masses of lenses. For some applications, (e.g., testing the theory), a point source lensed by a point-like lens would be more advantageous. However, until now only one gravitationally lensed star has been resolved. Future telescopes will resolve very small lensing signatures for stars orbiting the supermassive black hole (SMBH) in the center of the Milky Way. The lensing signatures, however, should be easier to detect for background stars. We predict that the Extremely Large Telescope (ELT), Thirty Meter Telescope (TMT), and Giant Magellan Telescope (GMT) will resolve the lensed images of around 100 (60) stars in the disk and 30 (20) stars in the bulge in the background of the SMBH, down to 28 (27) mag (Vega) limits at K-band, requiring 5 (1) hr of integration. In order to detect several such stars one needs the limit of at least 24 mag. With decade-long monitoring, one can also detect the rotation of the lensed images. The detection of elongated images will not be possible, because this would require a nearly perfect source-lens alignment. The James Webb Space Telescope (JWST) will likely be limited by the confusion caused by stars near the Galactic center. The detection of such lensed images will provide a very clean test of general relativity, when combined with the SMBH mass measurement from orbital motions of stars, and accurate measurements of the SMBH properties, because both the source and the lens can be considered point-like.

Item Type:Article
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URLURL TypeDescription Paper
Michałowski, Michał J.0000-0001-9033-4140
Mróz, Przemek0000-0001-7016-1692
Additional Information:© 2021. The American Astronomical Society. Received 2021 June 17; revised 2021 June 27; accepted 2021 June 29; published 2021 July 14. We wish to thank the referee for useful suggestions, and Joanna Baradziej, Mattia Negrello, Jean Surdej, and Łukasz Wyrzykowski for discussions and comments. M.J.M. acknowledges the discussion with Hong Du on gravitational lensing, which was a prompt to make calculations presented in the Letter. M.J.M. acknowledges the support of the National Science Centre, Poland, through the SONATA BIS grant 2018/30/E/ST9/00208. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration; the WebPlotDigitizer of Ankit Rohatgi ( and NASA's Astrophysics Data System Bibliographic Services.
Funding AgencyGrant Number
National Science Centre (Poland)2018/30/E/ST9/00208
Subject Keywords:Optical telescopes; Galactic center; Supermassive black holes; Strong gravitational lensing
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Optical telescopes (1174); Galactic center (565); Supermassive black holes (1663); Strong gravitational lensing (1643)
Record Number:CaltechAUTHORS:20210722-170903529
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Official Citation:Michał J. Michałowski and Przemek Mróz 2021 ApJL 915 L33
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109978
Deposited By: Tony Diaz
Deposited On:26 Jul 2021 22:38
Last Modified:26 Jul 2021 22:38

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