AsianScientist (Aug. 2, 2016) – A new gravitational lens, where light from a distant galaxy is distorted by the gravitational influence of a foreground galaxy, has just been observed in the skies. Interestingly, the discovery was made not in an astronomer’s office, but in a classroom.
Light from a distant galaxy can be strongly bent by the gravitational influence of a foreground galaxy. This effect is called strong gravitational lensing. Normally, a single galaxy is lensed at a time, but the same foreground galaxy can in theory simultaneously lens multiple background galaxies.
Nicknamed the Eye of Horus for the sacred eye of an ancient Egyptian god, the gravitational lens was discovered by students attending a yearly workshop in Japan organized by Subaru Telescope. Together with a group of astronomers, they were analyzing data from the Hyper Suprime-Cam (HSC), the large camera that takes images for the Telescope, when they found this unique lens system. Details of this ‘eye’ in the sky were published in The Astrophysical Journal Letters.
“When I was looking at HSC images with the students, we came across a ring-like galaxy and we immediately recognized it as a strong-lensing signature,” said lead author Dr. Masayuki Tanaka, from the National Astronomical Observatory of Japan.
A close inspection of the images revealed two distinct arcs or rings of light with different colors. This strongly suggested that two distinct background galaxies were being lensed by the foreground galaxy. The distinct features for the system—several bright knots, an arc, a complete Einstein ring—arise from the alignment of the central lens galaxy and both sources.
According to calculations, the lensing galaxy is about seven billion light-years away. Follow-up spectroscopic observations of the lensed objects confirmed that there are actually two galaxies behind the lens, which are nine and 10.5 billion light-years away, respectively.
The article can be found at: Tanaka et al. (2016) A Spectroscopically Confirmed Double Source Plane Lens System in the Hyper Suprime-Cam Subaru Strategic Program.
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Source: Subaru Telescope.
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