The edge of space is blasting outwards at the rate of around 74.3 kilometres per second per megaparsec; a megaparsec is about three million light-years in length.
NASA initially announced the results October 3, but clarified it a few days later to include mention of an independent study from the United States' Space Telescope Science Institute (STSCI) in Baltimore, Maryland.
"Spitzer is yet again doing science beyond what it was designed to do," stated JPL project scientist Michael Werner in a recent press release.
"First, Spitzer surprised us with its pioneering ability to study exoplanet atmospheres, and now, in the mission's later years, it has become a valuable cosmology tool."
Spitzer Space Telescope
The Spitzer Space Telescope (SST), formerly the Space Infrared Telescope Facility (SIRTF) is an infrared space observatory launched in 2003. It is the fourth and final of the NASA Great Observatories program.
The Hubble Constant
The universe's expansion rate is known as the Hubble Constant, and it has been revised several times over the years as the technology to measure it has improved.
Measuring Cepheids
Astronomers used the Spitzer telescope to observe Cepheids, which are stars that pulse at a regular rate.
Since observed Cepheids pulse at a rate that is relative to their brightness, these provide a useful measuring stick for astronomers seeking to measure the expanse of the universe.
Standard Candles
Cepheids are also known as "standard candles" because the principle to measuring the universe with them is similar to a person trying to measure his surroundings by observing candles.
Spitzer watched 10 Cepheids in the Milky Way and another 80 in the Large Magellanic Cloud, a galaxy that is relatively close to Earth.
Because Spitzer can peer through cosmic dust that obscures starlight, the measurements of brightness it came up with were more precise than previous observations.
This measurement led to the calculation of a more precise Hubble Constant.
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