National Astronomical Observatory of Japan



Ancient Eye in the Sky

| Science

Eye of Horus in pseudo color. Enlarged image to the right (field of view of 23 arcseconds x 19 arcseconds) show two arcs/rings with different colors. The inner arc has a reddish hue, while the outer arc has a blue tint. There are also the lensed images of the background galaxies which are originally the same galaxies as the inner and the outer arcs. The yellow-ish object at the center is a massive galaxy at z = 0.79 (distance 7 billion light years), which bends the light from the two background galaxies. Original size (1.79MB)

Light from a distant galaxy can be strongly bent by the gravitational influence of a foreground galaxy. That effect is called strong gravitational lensing. Normally a single galaxy is lensed at a time. The same foreground galaxy can - in theory - simultaneously lens multiple background galaxies. Although extremely rare, such a lens system offers a unique opportunity to probe the fundamental physics of galaxies and add to our understanding of cosmology. One such lens system has recently been discovered and the discovery was made not in an astronomer’s office, but in a classroom. It has been dubbed The Eye of Horus, and this ancient eye in the sky will help us understand the history of the universe.

The research paper was published on-line on June 26, 2016 in the Astrophysical Journal Letters (Tanaka et al. 2016, "A Spectroscopically Confirmed Double Source Plane Lens System in the Hyper Suprime-Cam Subaru Strategic Program").