Gravitational lensing explained
Channel: Stefan Jordan
Date: 2023-10-10

This animation provides a visual demonstration of how the position of a quasar relative to a lensing galaxy influences the position, number, and brightness of gravitational lensed images. Quasars are supermassive black holes that continuously accrete immense amounts of gas and matter, making them the brightest objects in the Universe.In some rare cases, the light from an extremely distant quasar passes near a massive galaxy or a cluster of galaxies. The gravitational field of these intervening objects bends the quasar's light rays, resulting in the production of multiple images of the quasar that would otherwise be a single background source. This phenomenon is known as strong gravitational lensing.The animation highlights that the distribution of mass within the lensing galaxy and its position relative to the line-of-sight toward the quasar determine the number and positions of the lensed images that are created.To explore the potential configurations of the lensed images, the animation artificially moves the position of the quasar in relation to the lensing galaxy. When the quasar and the lensing galaxy are not well aligned, only a single image of the quasar is observed. If they are closer in alignment, two images can be seen. And when they are almost perfectly aligned, four images of the quasar become visible.The animation notes that these changes cannot be observed in reality because quasars are located at such vast distances that their motions are incredibly small. Nonetheless, this visualization helps illustrate how the relative positions of quasars and lensing galaxies influence the appearance of gravitational lensed images.

More info on the Gaia mission: https://www.cosmos.esa.int/web/gaia

More on Gaia's search for gravitational lenses: https://www.cosmos.esa.int/web/gaia/fpr-gravitational-lens-search

Credits: ESA/Gaia/DPAC / This animation explains the content of the paper: "Focus Product Release: Search for strongly lensed quasars." by Gaia Collaboration, A. Krone-Martins, et al. 2023; and makes use of: Artist’s impression of quasar ULAS J1120+0641, ESO/M. Kornmesser, CC BY 4.0 / Galaxy Picture: Hubble Space Telescope image of Messier 77, NASA, ESA & A. van der Hoeven / Background image: NASA, ESA and T.M. Brown (STScI) / The artificial voice was created with https://ttsmp3.com / Video Animation created by Stefan Jordan / Based on a simulation by  Quentin Petit, Laboratoire d'Astrophysique de Bordeaux, France / Text of the animation created by: Stefan Jordan, Ludovic Delchambre, Christine Ducourant