An Einstein ring, also known as an Einstein gravitational lens, is a phenomenon predicted by Albert Einstein's theory of general relativity. It occurs when the light from a distant object, such as a galaxy, is gravitationally bent by the massive gravitational field of a foreground object, typically a massive galaxy or cluster of galaxies. This bending of light creates a circular or elliptical shape, resembling a ring, around the foreground object.
The James Webb Space Telescope (JWST) is an advanced space observatory designed to study the universe in infrared light. It has significantly greater sensitivity and resolution than previous telescopes, allowing astronomers to observe faint and distant objects with unprecedented detail.
Regarding the specific case you mentioned, astronomers used the JWST to observe a galaxy located more than 12 billion light-years away by utilizing the gravitational lensing effect. The massive foreground object, acting as a gravitational lens, distorted and magnified the light from the distant galaxy, making it brighter and easier to observe.
The gravitational lensing effect provided by the foreground object created an Einstein ring or a partial ring, depending on the alignment of the objects involved. By studying the shape, size, and properties of the Einstein ring, astronomers could deduce valuable information about the distant galaxy, such as its morphology, star formation rate, and distribution of dark matter within it. This observation technique using gravitational lensing enables scientists to explore and study objects that would otherwise be challenging to detect or analyze.
It's important to note that while the James Webb Space Telescope will enable groundbreaking observations, the details of specific observations and discoveries made by the telescope after my understanding in 2023 are not available to me. For the most up-to-date and accurate information, I recommend referring to official sources and astronomical publications.