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Slow Death of the Universe

An international team of astronomers studying 200,000 galaxies has discovered that the energy generated within a large portion of space is only half what it was 2 billion years ago – and declining.

Researchers from the International Centre for Radio Astronomy Research (ICRAR) in Western Australia used seven of the world’s most powerful telescopes to observe galaxies at 21 different wavelengths from the far ultraviolet to the far infrared. Initial observations were conducted using the Anglo-Australian Telescope, and supporting observations were made by two orbiting space telescopes operated by NASA and another belonging to the European Space Agency. The research is part of the Galaxy and Mass Assembly (GAMA) project, the largest multi-wavelength survey ever put together.

“We used as many space and ground-based telescopes we could get our hands on to measure the energy output of over 200,000 galaxies across as broad a wavelength range as possible,” said Prof Simon Driver of ICRAR, who presented the findings at the International Astronomical Union’s General Assembly in Honolulu.

All energy in the universe was created in the Big Bang, with some portion locked up as mass. Stars shine by converting this mass into energy as described by Einstein’s famous equation E=mc2.

“While most of the energy was created in the aftermath of the Big Bang, additional energy is constantly being released by stars as they fuse elements like hydrogen and helium together,” Driver said. “This newly released energy is either absorbed by dust as it travels through the host galaxy, or escapes into intergalactic space and travels until it hits something such as another star, planet, or very occasionally a telescope mirror.”

It has been known since the late 1990s that the universe is slowly fading, but this work shows that it’s happening across all wavelengths from the ultraviolet to the infrared, representing the most comprehensive assessment of the energy output of the nearby universe.

“The universe is fated to decline from here on in, like an old age that lasts forever. The universe has basically plonked itself down on the sofa, pulled up a blanket and is about to nod off for an eternal doze,” Driver said.

The GAMA team hopes to expand the work to map energy production over the entire history of the universe using a swathe of new facilities such as the world’s largest radio telescope, the Square Kilometre Array, which will be built in Australia and South Africa in the next decade.