Einstein Rings: Astronomers Discover Eight New Gravitational Lenses with Hubble Telescope

Images from the Hubble telescope reveal eight new Einstein rings, joining only three others previously known. Einstein rings are pairs of galaxies, with a foreground galaxy bending the light of a background galaxy into a ring by gravitational effects. The ring helps astronomers precisely estimate the mass of the foreground galaxy.
CAMBRIDGE, Mass--Ever look at the stars and wonder how it all came to be? Astronomers are now proving how our universe was created.
Seventy years ago, Einstein predicted how his theory of relativity could be demonstrated in space. Today, astronomers are using the Hubble telescope to confirm Einstein's prediction and shed light on how the world formed.
It starts when we're children ... Looking high in the sky and wondering how this was all created. Adam Bolton and a team of astronomers are one step closer to unraveling the mystery, with the discovery of these eight new Einstein rings. "The Einstein Rings are a pair of galaxies -- one, say, 4-billion light years away or so, and another one, maybe twice as far," says Adam Bolton, an astronomer at Harvard Smithsonian Center for Astrophysics in Cambridge, Mass.
In 1936, Albert Einstein wrote a paper using his theory of relativity, predicting the formation of the rings. Today, combining his information plus new data and photos from the Hubble telescope astronomers can find the rings. Bolton says, "What Hubble can do that telescopes on the ground cannot do is resolve very, very fine detail in images."
The phenomenon that created the rings is called gravitational lensing. The gravity of the nearer galaxy bends the path of light from the galaxy in the background, creating a dramatic bull's-eye. By studying the rings, astronomers precisely measure the mass of the closer galaxy.
"It teaches us more about the whole picture of the universe and, by extension, about how we fit into that," Bolton says.
Before this discovery only three other Einstein rings were visible. Astronomers believe they will discover even more.
BACKGROUND: Astronomers have combined two major astronomical projects -- the Hubble Space Telescope and the Sloan Digital Sky Survey -- to discover eight new rings of light, an optical illusion predicted by Albert Einstein. Previously, only three such rings have been observed in visible light.
WHAT CAUSES THE RINGS: "Einstein rings" are an optical illusion created when the fabric of spacetime is warped by the presence of massive objects, like stars or entire galaxies. The effect is known as gravitational lensing, and it is nature's equivalent to having a giant magnifying glass in space that bends and amplifies the light of more distant objects. Light from a distant galaxy can be deflected by an intervening galaxy to create an arc or multiple separate images. When both galaxies are exactly lined up, the light forms a bulls-eye pattern -- the Einstein ring -- around the foreground galaxy.
GENERAL RELATIVITY BASICS: Albert Einstein proposed his theory of general relativity in 1917. This attributes the force of gravity to the unseen warping of the fabric of spacetime, caused by the presence of mass (or energy). In a 1936 paper, he used general relativity to predict that the gravitational field formed by a massive object could not only warp space and deflect light, but in special cases, the light from a distant object could be so distorted it would create a complete ring.
WHAT WE CAN LEARN: "Einstein rings" serve as guideposts to help astronomers map the distribution of matter creating the warp in spacetime, and precisely determine the mass of the foreground galaxies. By studying this data, astronomers can glean more knowledge about the unseen "dark matter." This is an invisible and exotic form of matter that can't be seen, but its existence can be inferred by measuring its gravitational influence. Dark matter makes up most of the matter in the universe. Astronomers also hope to test the notion that galaxies form from collision, and through mergers of smaller galaxies.
HOW HUBBLE WORKS: Hubble has a long tube that is open at one end, with mirrors to gather and focus light to its "eyes" -- various instruments that enable it to detect different types of light. Light enters the telescope through the opening and bounces off a primary mirror to a secondary mirror, which reflects the light through a hole in the center of the primary mirror to a focal point behind the primary mirror. Smaller mirrors distribute the light to the various scientific instruments, which analyze the different wavelengths. Each instrument uses charge-coupled devices instead of photographic film to capture light -- the same array of photosensitive diodes that are used in digital cameras. The captured light is stored in on-board computers and relayed to Earth as digital signals, and this data is then transformed into images.

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