Microlensing Observations in Astrophysics

{{Short description|Astronomical research project}}

{{about|the MOA observatory project|the astrophysical process|Gravitational microlensing}}

{{use dmy dates |date=October 2020 }}

Image:Dome for MOA telescope.jpg

Microlensing Observations in Astrophysics (MOA) is a collaborative project between researchers in New Zealand{{cite news |author=Staff |title=MOA (Microlensing observation in Astrophysics) |url=https://sites.astro.caltech.edu/~srk/Workshops/TDAMMS/Files4Facilities/MOA.pdf |date=1995 |work=Caltech |access-date=3 October 2020 }} and Japan,{{cite journal |last=Yock |first=Philip |title=Review article - A quarter century of astrophysics with Japan |date=2012 |journal=New Zealand Science Review |volume=69 |issue=3 |arxiv=1510.05688 }} led by Professor Yasushi Muraki of Nagoya University.{{cite book |last1=Latham |first1=David W. |last2=Gaudi |first2=B. Scott |title=Encyclopedia of Astrobiology |chapter=Microlensing Observations in Astrophysics |chapter-url=https://link.springer.com/content/pdf/10.1007%2F978-3-642-27833-4_1850-2.pdf |date=2014 |work=Encyclopedia of Astronomy |page=1 |doi=10.1007/978-3-642-27833-4_1850-2 |isbn=978-3-642-27833-4 |access-date=3 October 2020 }} They use microlensing to observe dark matter, extra-solar planets, and stellar atmospheres from the Southern Hemisphere. The group concentrates especially on the detection and observation of gravitational microlensing events of high magnification, of order 100 or more, as these provide the greatest sensitivity to extrasolar planets. They work with other groups in Australia, the United States and elsewhere. Observations are conducted at New Zealand's Mt. John University Observatory using a {{convert|1.8|m|in|1|abbr=on}} reflector telescope built for the project.{{cite journal |author=Sumi, T. |display-authors=et al. |title=Microlensing Optical Depth toward the Galactic Bulge from Microlensing Observations in Astrophysics Group Observations during 2000 with Difference Image Analysis |url=https://iopscience.iop.org/article/10.1086/375212/fulltext/ |date=1 July 2003 |journal=The Astrophysical Journal |volume=591 |issue=1 |pages=204–227 |doi=10.1086/375212 |arxiv=astro-ph/0207604 |bibcode=2003ApJ...591..204S |s2cid=118776894 |access-date=3 October 2020 }}

In September 2020, astronomers using microlensing techniques reported the detection, for the first time, of an earth-mass rogue planet unbounded by any star, and free floating in the Milky Way galaxy.{{cite news |last=Gough |first=Evan |title=A Rogue Earth-Mass Planet Has Been Discovered Freely Floating in the Milky Way Without a Star |url=https://www.universetoday.com/148097/a-rogue-earth-mass-planet-has-been-discovered-freely-floating-in-the-milky-way-without-a-star/ |date=1 October 2020 |work=Universe Today |access-date=2 October 2020 }}{{cite journal |author=Mroz, Przemek|display-authors=et al.|title=A terrestrial-mass rogue planet candidate detected in the shortest-timescale microlensing event |journal=The Astrophysical Journal|date=29 September 2020 |volume=903|issue=1|pages=L11|doi=10.3847/2041-8213/abbfad|arxiv=2009.12377 |bibcode=2020ApJ...903L..11M|s2cid=221971000 |doi-access=free }} In January 2022 in collaboration with Optical Gravitational Lensing Experiment (OGLE) they reported in a preprint the first rogue BH{{cite journal |last1=Sahu |first1=Kailash C. |last2=Anderson |first2=Jay |last3=Casertano |first3=Stefano |last4=Bond |first4=Howard E. |last5=Udalski |first5=Andrzej |last6=Dominik |first6=Martin |last7=Calamida |first7=Annalisa |last8=Bellini |first8=Andrea |last9=Brown |first9=Thomas M. |last10=Rejkuba |first10=Marina |last11=Bajaj |first11=Varun |date=2022-05-25 |title=An Isolated Stellar-mass Black Hole Detected through Astrometric Microlensing |journal=The Astrophysical Journal |volume=933 |issue=1 |page=83 |doi=10.3847/1538-4357/ac739e |arxiv=2201.13296|bibcode=2022ApJ...933...83S |s2cid=246430448 |doi-access=free }}{{cite journal |last1=Lam |first1=Casey Y. |last2=Lu |first2=Jessica R. |last3=Udalski |first3=Andrzej |last4=Bond |first4=Ian |last5=Bennett |first5=David P. |last6=Skowron |first6=Jan |last7=Mroz |first7=Przemek |last8=Poleski |first8=Radek |last9=Sumi |first9=Takahiro |last10=Szymanski |first10=Michal K. |last11=Kozlowski |first11=Szymon |date=2022-05-31 |title=An Isolated Mass-gap Black Hole or Neutron Star Detected with Astrometric Microlensing |journal=The Astrophysical Journal Letters |volume=933 |issue=1 |pages=L23 |doi=10.3847/2041-8213/ac7442 |arxiv=2202.01903|bibcode=2022ApJ...933L..23L |s2cid=246608178 |doi-access=free }}{{Cite web |last=Gianopoulos |first=Andrea |date=2022-06-07 |title=Hubble Determines Mass of Isolated Black Hole Roaming Milky Way |url=http://www.nasa.gov/feature/goddard/2022/hubble-determines-mass-of-isolated-black-hole-roaming-our-milky-way-galaxy |access-date=2022-06-12 |website=NASA}}{{Cite web |last=O'Callaghan |first=Jonathan |title=Astronomers Find First Ever Rogue Black Hole Adrift in the Milky Way |url=https://www.scientificamerican.com/article/astronomers-find-first-ever-rogue-black-hole-adrift-in-the-milky-way/ |access-date=2022-02-08 |website=Scientific American |language=en}} while there have been others candidates{{Cite journal|last1=Bennett|first1=D. P.|last2=Becker|first2=A. C.|last3=Quinn|first3=J. L.|last4=Tomaney|first4=A. B.|last5=Alcock|first5=C.|last6=Allsman|first6=R. A.|last7=Alves|first7=D. R.|last8=Axelrod|first8=T. S.|last9=Calitz|first9=J. J.|last10=Cook|first10=K. H.|last11=Drake|first11=A. J.|date=2002-11-10|title=Gravitational Microlensing Events Due to Stellar-Mass Black Holes|url=https://iopscience.iop.org/article/10.1086/342225|journal=The Astrophysical Journal|language=en|volume=579|issue=2|pages=639–659|doi=10.1086/342225|arxiv=astro-ph/0109467|bibcode=2002ApJ...579..639B|s2cid=44193135|issn=0004-637X}} this is the most solid detection so far as their technique allowed to measure not only the amplification of light but also its deflection by the BH from the microlensing data.