Gravity’s lens: Finding a sextet of images

A team of astronomers has for the first time discovered a gravitational lens in which the image of a distant galaxy has been split into six distinct images. This unusual configuration is caused by three galaxies acting as a compound lens, strung out along the line of sight between the distant galaxy and Earth.

The trio of galaxies in orange form a gravitational lens that split the image of a background galaxy into six images (white). Rusin/ESA/STScI/NRAO/AU/NSF

Simpler than a lens produced by a galaxy cluster, yet more complicated than that generated by a single galaxy, this type of lens is expected to be rare. Study coauthor David Rusin of the University of Pennsylvania in Philadelphia says, “[It] will give us insights we can’t get from other types of lenses.” The team expects to learn about the structure of the galaxies serving as lenses.

The galaxy whose image has been split lies 11 billion light-years from Earth. The galaxies that act as a lens lie 4 billion light-years closer to Earth. Rusin and his colleagues describe their work in the Aug. 20 Astrophysical Journal.

Both the Very Large Array Radio Telescope in Socorro, N.M., and the MERLIN network of radio telescopes in England showed hints of six objects that astronomers suspected were images generated by a gravitational lens. Follow-up data from the Hubble Space Telescope and the Very Large Baseline Array, a group of 10 radio telescopes spread across the United States, confirmed the finding and provided additional details about the structure of the system.

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