Kitt Peak. Los Alamos. St. Croix. Pie Town.
What do these places have in common? They each house one of 10 giant telescopes in the Very Large Baseline Array, a continent-spanning collection of telescopes that’s flexing its optical muscles, reaching farther into space — with more precision — than any other telescope in the world.
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And today, at the 177th annual meeting of the American Association for the Advancement of Science in Washington, DC, VLBA researchers announced an amazing feat: They’ve used the VLBA to peer, with stunning accuracy, three times as far into the universe as they had just two years ago. New measurements with the VLBA have placed a galaxy called NGC 6264 (coordinates below) at a distance of 450 million light-years from Earth, with an uncertainty of no more than 9 percent. This is the farthest distance ever directly measured, surpassing a measurement of 160 million light-years to another galaxy in 2009.
Previously, distances beyond our own Galaxy have been estimated through indirect methods. But the direct seeing power of the VLBA scraps the need for assumptions, noted James Braatz, of the National Radio Astronomy Observatory.
The VLBA provides the greatest ability to see fine detail, called resolving power, of any telescope in the world. It can produce images hundreds of times more detailed than those from the Hubble Space Telescope, at a power equivalent to sitting in New York and reading a newspaper in Los Angeles. VLBA sites include Kitt Peak, Arizona; Los Alamos and Pie Town, New Mexico; St. Croix in the Virgin Islands, Mauna Kea, Hawaii; Brewster, Washington; Fort Davis, Texas; Hancock, New Hampshire; North Liberty, Iowa; and Owens Valley in California. Sure, I could include pictures of the scopes in Hawaii or the Virgin Islands. But Pie Town, besides hosting the Very Large Array, also has two fun restaurants (the Daily Pie and the Pie-O-Neer) with really amazing pie. And an annual pie-eating festival. So it wins:
Tripling the visible “yardstick” into space bears favorably on numerous areas of astrophysics, including determining the nature of dark energy, which constitutes 70 percent of the Universe. The VLBA is also redrawing the map of the Milky Way and is poised to yield tantalizing new information about extrasolar planets, the NRAO points out.
Fine-tuning the measurement of ever-greater distances is vital to determining the expansion rate of the Universe, which helps theorists narrow down possible explanations for the nature of dark energy. Different models of Dark Energy predict different values for the expansion rate, known as the Hubble Constant.
“Solving the Dark Energy problem requires advancing the precision of cosmic distance measurements, and we are working to refine our observations and extend our methods to more galaxies,” Braatz said. Measuring more-distant galaxies is vital, because the farther a galaxy is, the more of its motion is due to the expansion of the Universe rather than to random motions.
As for the map of our own galaxy, the direct VLBA measurements are improving on earlier estimates by as much as a factor of two. The clearer observations have already revealed the Milky Way has four spiral arms, not two as previously thought.
Mark Reid, of the Harvard-Smithsonian Center for Astrophysics led an earlier VLBA study revealing that the Milky Way is also rotating faster than previously believed — and that it’s as massive as Andromeda.
Reid’s team is now observing the Andromeda Galaxy in a long-term project to determine the direction and speed of its movement through space. “The standard prediction is that the Milky Way and Andromeda will collide in a few billion years. By measuring Andromeda’s actual motion, we can determine with much greater accuracy if and when that will happen,” Reid said.
The VLBA is also being used for a long-term, sensitive search of 30 stars to find the subtle gravitational tug that will reveal orbiting planets. That four-year program, started in 2007, is nearing its completion. The project uses the VLBA along with NRAO’s Green Bank Telescope in West Virginia, the largest fully-steerable dish antenna in the world. Early results have ruled out any companions the size of brown dwarfs for three of the stars, and the astronomers are analyzing their data as the observations continue.
Ongoing upgrades in electronics and computing have enhanced the VLBA’s capabilities. With improvements now nearing completion, the VLBA will be as much as 5,000 times more powerful as a scientific tool than the original VLBA of 1993.
NGC 6264 Coordinates, from DOCdb: 16<sup>h</sup> 57<sup>m</sup> 16.08<sup>s</sup>; +27° 50′ 58.9″
Source: A press release from the National Radio Astronomy Observatory, via the American Astronomical Society (AAS). Not to be confused with the American Association for the Advancement of Science (AAAS), which now conducting its annual meeting in Washington, DC — and where the VLBA results were presented.