The scientists noticed that they were looking at the galaxy cluster known as SDSS J223010.47-081017.8 when they found what they thought was an exact reflection of the galaxy and its companion.
Scientists discovered an unusual configuration of the gravitational lens, because they saw two bright objects that looked like mirror images of each other, while another eccentric object was nearby.
In other words, there are three observations of the same galaxy for no apparent reason.
These features confused astronomers so much that it took them several years to discover the mystery.
Using two gravitational lensing experts, the researchers determined that the three objects were distorted images of a distant, undiscovered galaxy. But the biggest surprise was that the linear objects were exact copies of each other, a rare event caused by the exact alignment of the background system and the foreground group.
The Hubble Telescope made this discovery thanks to a gravitational pull, first predicted by Albert Einstein’s theory of general relativity.
A gravitational lensing occurs when a massive number of objects, such as cluster galaxies, “create a gravitational field that distorts light and magnifies galaxies behind, but in the same line of sight,” according to NASA.
This effect is similar to seeing in a magnifying glass, and enables researchers to discover early galaxies not yet visible with modern technology.
The reflected images are now named after the astronomer Timothy Hamilton of Shawnee State University in Portsmouth, Ohio, who made the discovery.
“We were really shocked,” Hamilton said. “My first thought was that they might be interacting with galaxies with arms outstretched in tidal form. It didn’t really fit, but I also did not know what to think.”
Hubble looked at the nuclei of active galaxies, also called quasars, when he encountered the two bright images that seemed to be reflections of each other.
“Think of the wavy surface of a pool on a sunny day, with patterns of bright light on the bottom of the pool,” Richard Griffiths, co-author of the study, said in a statement.
He explained, “These light patterns at the bottom are caused by a similar kind of gravitational lensing effect. The wrinkles on the surface act as split lenses and focus sunlight on the glossy zigzag patterns below.”
“This gravitational pull is very different from most lenses Hubble has studied before, particularly in the Hubble Frontier Fields survey of clusters,” Griffiths added. “You do not have to stare at those groups for long to find many lenses. In this object, this is the only lens we have. We did not even know about the block at first.”
The images show that the galaxy is 11 billion light-years away, while the foreground mass known as SDSS J223010.47-081017.8 is more than 7 billion light-years away.
Astronomers hope that observations of “Hamilton objects” will provide clues as to the nature of dark matter.