Thanks to the eerie "Eye of Sauron" galaxy, which gets its nickname from the Lord of The Rings, astronomers now have a better tool in measuring distances of galaxies from Earth, and like its namesake, it has something to do with a ring.
The ring in question is a ring of dust surrounding the massive black hole at the center of the NGC 4151 galaxy, otherwise known as the "Eye of Sauron."
We've attempted to measure the distance of NGC 4151 from Earth before, but estimates varied from 13 million to 95 million light-years. That's hardly accurate. So astronomers turned to two telescopes at the W.M. Keck Observatory in Hawaii and imaged the galaxy, getting resolutions a hundred times greater than the Hubble Space Telescope.
These new observations let astronomers see the glowing ring of dust around the galaxy's black hole, which is common in active galaxies. They then used geometry to figure out the distance from the ring to the center of the black hole and using that, triangulated the distance from Earth. This is similar to how land surveyors on Earth measure distances.
So how far is the Eye of Sauron from Earth? This new technique puts it at 62 million light-years away.
"One of the key findings is that the distance determined in this new fashion is quite precise - with only about 10 percent uncertainty," says Dr. Sebastian Hoenig from the University of Southampton. "In fact, if the current result for NGC 4151 holds for other objects, it can potentially beat any other current methods to reach the same precision to determine distances for remote galaxies directly based on simple geometrical principles."
This gives us the opportunity to measure distances to celestial objects farther away than ever before. However, it also gives us a way to measure how quickly certain parts of the Universe are expanding, as well as tell us how big specific black holes and galaxies are.
NGC 4151 is about 124,000 light-years wide. Its black hole is about 37 million times the mass of our sun.
If you're interested in seeing the Eye of Sauron yourself, you can easily do so this time of year from the northern hemisphere using a telescope with a mirror or lens four inches or larger. Just look in the constellation Canes Venatici just before dawn. You'll see NGC 4151 about halfway up in the northeast just below the Big Dipper.
Of course, you won't see the sort of detail telescopes like the Hubble have picked out, but it should still appear as a small oval patch of light in the sky.
[Photo Credit: X-ray: NASA/CXC/CfA/J.Wang et al.; Optical: Isaac Newton Group of Telescopes, La Palma/Jacobus Kapteyn Telescope, Radio: NSF/NRAO/VLA]
