'Eye of Sauron' Measures Distances to Far Flung Galaxies

The "Eye of Sauron" isn't just something that appears in The Lord of the Rings movies. Astronomers are now using a cosmic feature with the same namesake to measure precise distances to galaxies that are tens of millions of light-years away.

The new method is similar to what land surveyors use on Earth. By measuring the physical and angular, or "apparent" size of a standard ruler in the galaxy, the scientists can calculate distance from this information. In this case, the researchers identified the accurate distance of the galaxy, NGC4151, also known as the "Eye of Sauron."

All large galaxies in the universe hold a supermassive black hole at their center, and the Eye of Sauron is no exception. The hot dust being swallowed by this black hole forms a dusty ring that emits infrared radiation, which the scientists used as their ruler.

To measure the physical size of the ring, the researchers measured the time delay between the emission of light from very close to the black hole and the infrared emission. This delay was the distance the light had to travel from close to the black hole out to the hot dust. By combining this physical size of the dust ring with the apparent size measured with the data from the Keck interferometer, the scientists determined the distance to the galaxy, which is 19 megaparsecs.

"Such distances are key in pinning down the cosmological parameters that characterize our universe or for accurately measuring black hole masses," said Sebastian Hoenig, one of the researchers, in a news release. "Indeed, NGC 4151 is a crucial anchor to calibrate various techniques to estimate black hole masses. Our new distance implies that these masses may have been systematically underestimated by 40 percent."

The findings reveal a bit more about this galaxy and also pave the way for future studies when it comes to distances in the universe.

The findings are published in the journal Nature. 

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