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Universe is expanding faster than we thought - Technology & science - Space | NBC News

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Expansion of space measurement improved

Source: EurekaAlert
How fast is our universe expanding? Over the decades, there have been different estimates used and heated debates over those approximations, but now data from the Spitzer Space Telescope have provided the most precise measurement yet of the Hubble constant, or the rate at which our universe is stretching apart. The result? The universe is getting bigger a little bit faster than previously thought. The newly refined value for the Hubble constant is 74.3 plus or minus 2.1 kilometers per second per megaparsec. The best previous estimation came from a study from the Hubble Space Telescope, at 74.2 plus or minus 3.6 kilometers per second per megaparsec. A megaparsec is roughly 3 million light-years. To make the new measurements, Spitzer scientists looked at pulsating stars called Cepheid variable stars, taking advantage of being able to observe them in long-wavelength infrared light. In addition, the findings were combined with previously published data from NASA's Wilkinson Microwave Anisotropy Probe. The new determination brings the uncertainty down to 3 percent, a significant advance in accuracy for cosmological measurements, scientists say. WMAP obtained an independent measurement of dark energy, which is thought to be winning a battle against gravity, pulling the fabric of the universe apart. Research based on this acceleration garnered researchers the 2011 Nobel Prize in physics. The Hubble constant is named after the astronomer Edwin P. Hubble, who astonished the world in the 1920s by confirming that our universe has been expanding since it exploded into being 13.7 billion years ago. In the late 1990s, astronomers discovered the expansion is accelerating, or speeding up over time. Determining the expansion rate is critical for understanding the age and size of the universe. "This is a huge puzzle," said the lead author of the new study, Wendy Freedman of the Observatories of the Carnegie Institution for Science in Pasadena. "It's exciting that we were able to use Spitzer to tackle fundamental problems in cosmology: the precise rate at which the universe is expanding at the current time, as well as measuring the amount of dark energy in the universe from another angle." Freedman led the groundbreaking Hubble Space Telescope study that earlier had measured the Hubble constant. Glenn Wahlgren, Spitzer program scientist at NASA Headquarters in Washington, said the better views of Cepheids enabled Spitzer to improve on past measurements of the Hubble constant. "These pulsating stars are vital rungs in what astronomers call the cosmic distance ladder: a set of objects with known distances that, when combined with the speeds at which the objects are moving away from us, reveal the expansion rate of the universe," said Wahlgren. Cepheids are crucial to the calculations because their distances from Earth can be measured readily. In 1908, Henrietta Leavitt discovered that these stars pulse at a rate directly related to their intrinsic brightness. To visualize why this is important, imagine someone walking away from you while carrying a candle. The farther the candle traveled, the more it would dim. Its apparent brightness would reveal the distance. The same principle applies to Cepheids, standard candles in our cosmos. By measuring how bright they appear on the sky, and comparing this to their known brightness as if they were close up, astronomers can calculate their distance from Earth. Spitzer observed 10 Cepheids in our own Milky Way galaxy and 80 in a nearby neighboring galaxy called the Large Magellanic Cloud. Without the cosmic dust blocking their view, the Spitzer research team was able to obtain more precise measurements of the stars' apparent brightness, and thus their distances. These data opened the way for a new and improved estimate of our universe's expansion rate. "Just over a decade ago, using the words 'precision' and 'cosmology' in the same sentence was not possible, and the size and age of the universe was not known to better than a factor of two," said Freedman. "Now we are talking about accuracies of a few percent. It is quite extraordinary." "Spitzer is yet again doing science beyond what it was designed to do," said project scientist Michael Werner at NASA's Jet Propulsion Laboratory. Werner has worked on the mission since its early concept phase more than 30 years ago. "First, Spitzer surprised us with its pioneering ability to study exoplanet atmospheres," said Werner, "and now, in the mission's later years, it has become a valuable cosmology tool." Paper on arXiv: A Mid-Infrared Calibration of the Hubble Constant Source: JPL This report was originally published on Universe Today as "Spitzer Provides Most Precise Measurement Yet of the Universe's Expansion." Copyright © 2013 Universe Today. Republished with permission.
Public release date: 3-Oct-2012 [ | E-mail | Share ] Contact: Wendy Freedman freedman@obs.carnegiescience.edu 626-304-0204 Carnegie Institution Expansion of space measurement improved Pasadena, CA� A team of astronomers, led by Wendy Freedman, director of the Carnegie Observatories, have used NASA's Spitzer Space Telescope to make the most accurate and precise measurement yet of the Hubble constant, a fundamental quantity that measures the current rate at which our universe is expanding. These results will be published in the Astrophysical Journal and are available online. The Hubble constant is named after 20th Century Carnegie astronomer Edwin P.Hubble, who astonished the world by discovering that our universe is expanding now and has been growing continuously since its inception. Astronomers now know that the universe exploded into being in a Big Bang about about 13.7 billion years ago. Determining Hubble's constant, a direct measurement of the rate of this continuing expansion, is critical for gauging the age and size of our universe. Spitzer's new measurement, which took advantage of long-wavelength infrared instead of visible light, improves upon a similar, seminal study from NASA's Hubble Space Telescope by a factor of three, bringing the uncertainty down to only three percent, a giant leap in accuracy for a cosmological measurement. The newly refined value, in astronomer-speak, is: 74.3 � 2.1 kilometers per second per megaparsec (a megaparsec is roughly 3 million light-years). "Spitzer is yet again doing science it wasn't designed to do," said Michael Werner, the mission's project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., who has worked on the mission since its early concept phase more than 30 years ago. "First, it surprised us with its pioneering ability to study exoplanet atmospheres, and now, in the mission's later years, it's become a valuable cosmology tool." In addition, the findings were combined with published data from NASA's Wilkinson Microwave Anisotropy Probe (WMAP) to obtain an independent measurement of dark energy, one of the greatest mysteries of our cosmos. In the late 1990s, astronomers were shocked to learn that the expansion of our universe is speeding up over time, or accelerating. Dubbed dark energy, this force or energy is thought to be winning a battle against gravity, pulling the fabric of the universe apart. Research documenting this acceleration garnered the 2011 Nobel Prize in physics. "This is a huge puzzle," said lead author Freedman. "It's exciting that we were able to use Spitzer to tackle fundamental problems in cosmology: the precise rate at which the universe is expanding at the current time, as well as measuring the amount of dark energy in the universe from another angle." Spitzer was able to improve upon past measurements of Hubble's constant due to its infrared vision, which sees through dust to provide better views of variable stars called Cepheids. These pulsating stars are vital "rungs" in what astronomers called the cosmic distant ladder: a set of objects with known distances that, when combined with the speeds at which the objects are moving away from us, reveal the expansion rate of the universe. Cepheids are crucial to these calculations because their distances from Earth can be readily measured. In 1908, Henrietta Leavitt discovered that these stars pulse at a rate that is directly related to their intrinsic brightness. To visualize why this is important, imagine somebody walking away from you while carrying a candle. The candle would dim the farther it traveled, and its apparent brightness would reveal just how far. The same principle applies to Cepheids, standard candles in our cosmos. By measuring how bright they appear on the sky, and comparing this to their known brightness as if they were close up, astronomers can calculate their distance from Earth. Spitzer observed ten Cepheids in our own Milky Way galaxy and 80 in a nearby neighboring galaxy called the Large Magellanic Cloud. Without the cosmic dust blocking their view at the infrared wavelengths, the research team was able to obtain more precise measurements of the stars' apparent brightness, and thus their distances, than previous studies had done. With these data, the researchers could then tighten up the rungs on the cosmic distant ladder, opening the way for a new and improved estimate of our universe's expansion rate. "Just over a decade ago, using the words 'precision' and 'cosmology' in the same sentence was not possible, and the size and age of the universe was not known to better than a factor of two," Freedman said. "Now we are talking about accuracies of a few percent. It is quite extraordinary" The research team included former and current Carnegie scientists Barry Madore, Vicky Scowcroft, Andrew Monson, Chris Burns, Mark Seibert, Eric Persson, and Jane Rigby. ### The Carnegie Institution for Science is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science. 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