'Eye of Sauron' Helps Scientists Determine Distance to Galaxies

The "Eye of Sauron," scientifically known as the nearby NGC 4151 galaxy, is helping scientists to determine the distance to other galaxies tens of millions of light-years away, according to a new study.

Using the W. M. Keck Observatory in Hawaii, researchers can measure the physical and angular - or "apparent" - size of a standard ruler in a galaxy. From this, they can determine its distance from Earth.

"Such distances are key in pinning down the cosmological parameters that characterize our Universe or for accurately measuring black hole masses," leader Dr. Sebastian Hoenig, from the University of Southampton, said in a statement.

So how far away is the "Eye of Sauron"? Though the galaxy may be named for the villain in the "Lord of the Rings" trilogy, don't look to Frodo this time for the answer.

NGC 4151 lays 19 megaparsecs, or nearly 62 million light-years, away from Earth.

"One of the key findings is that the distance determined in this new fashion is quite precise - with only about 10 percent uncertainty," added Hoenig.

To achieve this measurement, Hoenig's team used the dusty ring surrounding the black hole at the center of NGC 4151 as a ruler. However, the apparent size of this ring is so small that the observations were carried out using infrared interferometry.

Then, to measure the physical size of the hot ring of dust, the researchers determined the delay in the time it took for light to travel from close to the black hole out to the hot dust.

So as in the famous saga, a ring plays a crucial role. These new measurements are key for determining the masses of far away black holes, and show just how far of a journey it would be to the "Eye of Sauron."

The results were published Wednesday in the journal Nature.

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