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“Eye of Sauron” Helps Astronomers Measure Cosmic Distances

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“Eye of Sauron” Helps Astronomers Measure Cosmic Distances

The universe is vast, making it extremely difficult to measure distances between heavenly bodies. Currently, the most common method can measure relative distances, but researchers from the Niels Bohr Institute at the University of Copenhagen, the University of Southampton, and the Kyoto Sangyo University have found another way thanks to “Eye of Sauron.”

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.

Thanks to measuring the “Eye of Sauron,” researchers were able to come up with a new technique making it possible to more accurately measure distance in space.

Thanks to measuring the “Eye of Sauron,” researchers were able to come up with a new technique making it possible to more accurately measure distance in space.

All big galaxies in the universe host a supermassive black hole in their center, and in about 10 percent of all galaxies, these supermassive black holes are growing by swallowing huge amounts of gas and dust from their surrounding environments.

In this process, the material heats up and becomes very bright — becoming the most energetic sources of emission in the universe known as active galactic nuclei (AGN).

This hot dust forms a ring around the supermassive black hole and emits infrared radiation, which the researchers used as the ruler. However, the apparent size of the Eye of Sauron’s ring is so small, the observations were carried out using the Keck Interferometer, which combines Keck Observatory’s twin 10-meter telescopes.

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.

“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.”

Dr. Hoenig, together with colleagues in Denmark and Japan, is currently setting up a new program to extend their work to many more AGN (active galactic nuclei ). The goal is to establish precise distances to a dozen galaxies in this new way and use them to constrain cosmological parameters to within a few per cent. In combination with other measurements, this will provide a better understanding of the history of expansion of our universe.

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Study Source: http://goo.gl/h1FpM1.

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