How Far Is the ‘Eye of Sauron’? Astronomers Find Out

A galaxy about 43 million light years from Earth with an actively growing black hole at its center.
Chandra X-ray Observatory Center / X-ray: NASA/CXC/CfA/J.Wang et al.; Optical: Isaac Newton Group of Telescopes, La Palma/Jacobus Kapteyn Telescope, Radio: NSF/NRAO/VLA

How far away is the "Eye of Sauron"? Don't ask Frodo.

The Eye of Sauron is what astronomers call NGC 4151, a galaxy that has a strong resemblance to the villain in the "Lord of the Rings" films. University of Southampton astronomer Sebastian Hönig and his colleagues discovered a new way to measure the distance to such galaxies, which are tens of millions of light-years away. Instead of judging distance by the brightness of an object, which is how astronomers handle most such measurements, the researchers used geometry to tell how far the Eye of Sauron was from Earth.

NGC4151 has an active galactic nucleus, or AGN, which is powered by a supermassive black hole. The AGN releases radiation that lights up the surrounding gas and dust. Using the optical interferometer at the W.M. Keck Observatory on Mauna Kea in Hawaii, astronomers were able to observe the lit-up area and determine the length of the base of a very, very large isosceles triangle.

Their research was published Wednesday in the journal Nature.

So how far away is it? The distance to the Eye of Sauron is 19 megaparsecs, or nearly 62 million light-years. That means any hobbits looking to visit better be prepared for an extremely long journey.