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| gravitational lensing | |
|---|---|
| Name | Gravitational lensing |
| Caption | Einstein Cross in Hubble Space Telescope |
| Field | Astrophysics, General relativity |
| Discovered | 1919 Solar eclipse of 1919 |
| Key people | Albert Einstein, Sir Arthur Eddington, Ostrogradsky |
| Notable instruments | Hubble Space Telescope, Very Large Telescope, Atacama Large Millimeter/submillimeter Array |
gravitational lensing
Gravitational lensing is the deflection and magnification of light from a background source by the gravitational field of an intervening mass. First tested during the Solar eclipse of 1919 in observations associated with Royal Observatory, Greenwich and expeditions led by Sir Arthur Eddington, the phenomenon provides a probe of mass distributions and spacetime curvature predicted by General relativity. It underpins techniques used by observatories such as the Hubble Space Telescope and facilities like the Very Large Telescope to map dark matter and study distant galaxies.
Gravitational lensing occurs when light from a background object, for example a quasar or galaxy observed by Hubble Space Telescope or the James Webb Space Telescope, is bent by the gravity of a foreground lens such as a galaxy cluster like Abell 1689 or a massive galaxy observed by the Sloan Digital Sky Survey. Lensing creates observable features—multiple images, arcs, Einstein rings—documented in surveys led by teams from European Southern Observatory, Harvard–Smithsonian Center for Astrophysics, and National Aeronautics and Space Administration. Phenomena are categorized by angular scale and alignment, with practical applications in programs run by Keck Observatory, Subaru Telescope, and the Large Synoptic Survey Telescope consortium.
The theoretical framework rests on General relativity and the deflection angle derived from solutions associated with Karl Schwarzschild and the Schwarzschild metric; early analytic work traces to Albert Einstein and later formalism by Ostrogradsky and others in gravitational theory. Lens modeling uses the lens equation formulated in contexts like the Friedmann–Lemaître–Robertson–Walker metric and incorporates mass profiles such as the Navarro–Frenk–White profile developed by researchers affiliated with Princeton University and University of California, Santa Cruz. Techniques include ray tracing used in simulations by groups at Max Planck Institute for Astrophysics and inverse methods applied by teams at California Institute of Technology to reconstruct lens mass from image configurations.
Strong lensing produces multiple discrete images and rings seen in systems studied with Hubble Space Telescope and cataloged by the Sloan Digital Sky Survey; classic examples involve quasars such as those observed by Palomar Observatory teams. Weak lensing, measured statistically across fields surveyed by the Canada–France–Hawaii Telescope and the Dark Energy Survey collaboration, causes subtle shear patterns exploited by projects at European Space Agency missions and the Euclid consortium. Microlensing, detected in time-domain studies by collaborations like Optical Gravitational Lensing Experiment and Microlensing Observations in Astrophysics, reveals compact objects including exoplanets found by teams at Space Telescope Science Institute and probes stellar remnants referenced in work from Harvard University.
Observations employ space telescopes such as Hubble Space Telescope and James Webb Space Telescope, ground-based facilities including Very Large Telescope, Keck Observatory, and radio arrays like Atacama Large Millimeter/submillimeter Array and Very Large Array. Imaging surveys by the Sloan Digital Sky Survey, spectroscopic follow-up at Gemini Observatory, and time-domain monitoring by the Large Synoptic Survey Telescope enable detection and characterization of lenses. Data analysis relies on pipelines developed at institutions such as Lawrence Berkeley National Laboratory and Jet Propulsion Laboratory using algorithms from groups at Carnegie Observatories and Max Planck Institute for Astronomy.
Lensing maps mass distributions in systems like Coma Cluster and Bullet Cluster, providing evidence for non-baryonic dark matter studied by researchers at University of Chicago and Columbia University. Time delays between multiple images measured in systems monitored by Hubble Space Telescope and the Keck Observatory furnish independent estimates of the Hubble constant used by teams at Carnegie Institution for Science and European Southern Observatory. Microlensing surveys conducted by Optical Gravitational Lensing Experiment and Microlensing Observations in Astrophysics constrain compact dark matter candidates emphasized in studies from University of Cambridge and Princeton University. Lensing also magnifies high-redshift galaxies targeted by James Webb Space Telescope and aids investigations into galaxy evolution led by Space Telescope Science Institute researchers.
Historic tests during the Solar eclipse of 1919 by expeditions from Royal Observatory, Greenwich established early confirmation; later milestones include the discovery of the Einstein Cross imaged by Hubble Space Telescope and catalogs from the Sloan Digital Sky Survey and COSMOS survey conducted by teams at California Institute of Technology and University of Hawaii. The Dark Energy Survey and the Hyper Suprime-Cam Subaru Strategic Program produced extensive weak-lensing measurements analyzed by collaborations at Fermi National Accelerator Laboratory and Stanford University. Microlensing detections by Optical Gravitational Lensing Experiment and the Microlensing Observations in Astrophysics project revealed exoplanets announced by groups at Max Planck Institute for Astronomy and European Southern Observatory.
Key challenges include systematic errors in shear measurement tackled by consortia like the Euclid team and the Large Synoptic Survey Telescope collaboration, degeneracies in mass models addressed by researchers at Max Planck Institute for Astrophysics and Kavli Institute for Cosmological Physics, and the need for higher-resolution follow-up using platforms such as James Webb Space Telescope and next-generation arrays like the Square Kilometre Array. Future prospects involve surveys by Euclid and the Large Synoptic Survey Telescope plus targeted programs with Atacama Large Millimeter/submillimeter Array and Very Large Telescope to refine constraints on dark matter and the expansion history pursued by scientists at Princeton University and Harvard–Smithsonian Center for Astrophysics.