AsianScientist (Jun. 10, 2016) – The Universe is expanding faster than expected, a study involving Australian National University has found. The findings will be published in the Astrophysical Journal.
Lead researcher and astrophysicist from the Research School of Astronomy and Astrophysics, Dr. Brad Tucker, said the precision study of star movements found that the Universe is currently expanding between five percent and nine percent faster than early in its life.
“A funny universe just got funnier,” said Tucker. “We thought we were close to understanding dark energy, but now we know we don’t know the answer at all. There’s a lot of work to do.”
Cosmologists have realized in recent decades that normal matter such as stars, planets and gas constitutes only five percent of the Universe. The rest is 25 percent dark matter and 70 percent dark energy, both of which are invisible and have never been directly detected.
Precise values of the Universe’s expansion from 13.8 billion years ago have been calculated from observations of the cosmic microwave background—the very faint afterglow of the Big Bang.
The research team used the Hubble Space telescope to look at variable stars called Cepheids and Type Ia supernovae, both of which have well-known, easily measured levels of brightness. This enables their distance to be precisely determined.
Using the parallax shift between objects of different distances, the team measured the movements of about 2,400 Cepheid stars and about 300 Type Ia supernovae over two and a half years.
From these measurements they calculated the Universe’s expansion rate, known as the Hubble constant, to be 73.2 km/s per megaparsec. A megaparsec equals 3.26 million light-years. The new value means the distance between cosmic objects will double in another 9.8 billion years.
The team proposed a number of possible explanations for the Universe’s excessive speed: one possibility is that dark energy, already known to be accelerating the universe, may be shoving galaxies away from each other. Another idea is that the cosmos contained a new subatomic particle in its early history that traveled close to the speed of light and affected the expansion rate.
The boost in acceleration could also mean that dark matter possesses some weird, unexpected characteristics; or the speedier Universe may be telling astronomers that Einstein’s theory of gravity is incomplete.
According to Tucker, it could also be due to the assumption that Cepheids and Type Ia supernovae are standard modes of distance measurement. Future studies using different techniques will hopefully shed light on exactly what is going on, he said.
Source: Australian National University; Photo: NASA, ESA, A. Feild (STScI), and A. Riess (STScI/JHU).
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