The "Eye of Sauron" is assisting astronomers seeking new methods to accurately measure distances to far-flung galaxies.
Using the Keck Observatory, perched on Mauna Kea in Hawaii, astronomers have developed a new method of determining distances to galaxies, located far from Earth. The method is similar to the one used by land surveyors here on Earth. By measuring the angular size of a known length between two points, it is possible to determine the distance to the targets.
The "Eye of Sauron," known to astronomers as NGC 4151, is a galaxy containing a supermassive black hole. Astronomers had been unable to determine an accurate distance to the galactic feature. Estimates ranged anywhere from just over 13 million light years to over 94.5 million light years away from Earth.
Using the new method for determining galactic distance, astronomers discovered the Eye of Sauron lies just under 62 million light years from our solar system.
"Such distances are key in pinning down the cosmological parameters that characterize our universe or for accurately measuring black hole masses. 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 per cent," Sebastian Hoenig from the University of Southampton said.
Large galaxies all contain supermassive black holes at their centers, and roughly one in 10 of these are observed consuming vast quantities of dust, radiating energy as active galactic nuclei (AGN). This material forms into a ring around the massive black hole.
A pair of telescopes, nearly 33 feet across, was used to examine the distant ring, glowing in infrared radiation from the perimeter of the black hole's event horizon. Computers combined the images from each instrument, producing images with a level of detail equivalent to using a telescope nearly 280 feet in diameter.
"Using telescopes on Earth, we can now measure the time delay between the ultraviolet light from the black hole and the subsequent infrared radiation emitted from the dust cloud," Darach Watson of the Dark Cosmology Centre at Niels Bohr Institute in Denmark said.
Future researchers can utilize the same method to accurately determine the distance to around 12 additional galaxies. This will provide cosmologists with data revealing details about the expansion of the Universe.
The popular name of the galaxy is due to its resemblance to the Eye of Sauron in the Lord of the Rings.
Development of the new astronomical technique was detailed in the journal Nature.
