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article imageWe may have overestimated the expansion rate of the universe

By James Walker     Apr 12, 2015 in Science
New observations of supernovae have suggested that the universe may be expanding much slowly than has been thought up until now. This is a large change that could influence future theories about the end of the universe.
The observations were made by astronomers at the University of Arizona and found that there may be potential inaccuracies in the way in which astronomical distance is measured.
The discovery that the universe is expanding was made based on observations of the light from distant supernovae moving towards the red end of the spectrum in a phenomenon known as redshift. Redshift is observed by looking at a specific type of supernovae known as "type la supernovae" that are thought to be very similar to each other.
These act as cosmic beacons that allow scientists to gauge distance and movement in the universe and make it possible to detect the expansion of the universe.
The researchers have found that supernovae can be far from the same though. Distinct categories were discovered where some are much brighter than others.
The data used was obtained by a large sample of type la supernovae from the Hubble Space Telescope and the NASA Swift satellite. Commonalities were found in the two samples and later in more datasets to confirm the trend.
This is crucial to our current knowledge of the universe's expansion. The current method of comparing the redshift of supernovae to galaxies of a known distance from earth only works if every type la supernova is about the same as they are believed to be. This makes it possible to attribute any observed differences to distance, creating a redshift observation.
Peter A Milne, the group's lead investigator, told Motherboard: "There are different populations out there, and they have not been recognized. The big assumption has been that as you go from near to far, type Ia supernovae are the same. That doesn't appear to be the case."
What this all means is that the universe may not be expanding so rapidly as previously thought. The discovery that the universe's expansion was accelerating was made by Saul Perlmutter, Brian Schmidt and Adam Riess by looking closely at redshift observations.
The acceleration was explained by the theory of the mysterious "dark energy", the theoretical force that is responsible for pushing the universe outwards. The discoveries regarding type la supernovae by Milne's group suggest that the universe may contain much less dark energy than previously thought, leading to less force to expand the universe with.
Much work now needs to be reexamined in the light of the findings. Now that it is known that not all type la supernovae are the same after all and are not reliable indicators of distance, many redshift observations may be invalid or incorrect and we could have overestimated the expansion of the universe.
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