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"Before Hubble, astronomers could not decide if the universe
was 10 billion or 20 billion years old," said team leader
Wendy Freedman of the Observatories of the Carnegie Institution
of Washington. "The size scale of the universe had a range
so vast that it didn't allow astronomers to confront with any
certainty many of the most basic questions about the origin and
eventual fate of the cosmos. After all these years, we are finally
entering an era of precision cosmology. Now we can more reliably
address the broader picture of the universe's origin, evolution
and destiny." The team measured the Hubble Constant to be 70 km/sec/mpc,
with an uncertainty of 10 percent. This means that a galaxy appears
to be moving 160,000 miles per hour faster for every 3.3 million
light-years away from Earth.
The team used the Hubble telescope to observe 18 galaxies out to 65 million light-years. They discovered almost 800 Cepheid variable stars, a special class of pulsating star used for accurate distance measurement. Although Cepheids are rare, they provide a very reliable "standard candle" for estimating intergalactic distances. The team used the stars to calibrate many different methods for measuring distances. "Our results are a legacy from the Hubble telescope that
will be used in a variety of future research," said Jeremy
Mould of the Australian National University, also a co-leader
of the team. "It's exciting to see the different methods
of measuring galaxy distances converge, calibrated by the Hubble
Space Telescope."
The universe's age is calculated using the expansion rate from precise distance measurements, and the calculated age is refined based on whether the universe appears to be accelerating or decelerating, given the amount of matter observed in space. A rapid expansion rate indicates the universe did not require as much time to reach its present size, and so it is younger than if it were expanding more slowly. The Hubble Space Telescope Key Project Team is an international group of 27 astronomers from 13 different U.S. and international institutions. The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc. for NASA, under contract with NASA's Goddard Space Flight Center, Greenbelt, MD. |
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HUBBLE COMPLETES EIGHT-YEAR EFFORT TO MEASURE EXPANDING UNIVERSE, NASA HQ press release, May 25, 1999 The Expansion Rate and Size of the Universe., W.L. Freedman. From Scientific American, March 1998. The Shapley-Curtis Debate in 1920.What is the scale of the Universe? What was the debate, why was it important, and how was it resolved? From Astronomy Picture of the Day. 75 years later: the 1996 debate on the size and age of the Universe. What is the scale of the Universe? What was the debate, why was it important, and how was it resolved? From Astronomy Picture of the Day. Edwin Powell Hubble -- Biographical Memoir The Hubble Constant -- from a NASA Space Science Short Hubble's Constant and the Expanding Universe (I) -- Astronomy Picture of the Day, May 13, 1996 Hubble's Constant and the Expanding Universe (II) -- Astronomy Picture of the Day, May 14, 1996 Edwin Hubble Discovers the Universe -- Astronomy Picture of the Day, Feb 17, 1996 The Cepheids of M100 -- Astronomy Picture of the Day, Jan 10, 1996 PG 1115: A Ghost of Lensing Past -- Astronomy Picture of the Day, Nov 2, 1998 Cosmic Gamma-ray Bursts -- News and Research More Space Science Headlines - NASA research on the web NASA's Office of Space Science press releases and other news related to NASA and astrophysics |
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