What is an Einstein ring?
Quick Answer
An Einstein ring is a nearly perfect circular image made when gravitational lensing bends light from a distant object around a massive foreground object. It is a rare alignment effect.
The Full Story
Einstein rings form when a background galaxy, a foreground lensing galaxy or cluster, and the observer line up almost perfectly. The foreground mass bends the background light into a ring or near-ring shape instead of a point-like image. The phenomenon is named after Albert Einstein because it follows from general relativity, though Einstein himself did not expect such a dramatic visible result. These rings help astronomers study both the lensing mass and the distant source.
Key Facts
YouTube Angle
Suggested video title for this topic:
"A cosmic halo made when gravity bends light into a circle"