UH team sees ‘dark energy’ trail

University of Hawaii astronomers have discovered evidence of "dark energy," one of the great mysteries of science.

Dark energy causes acceleration of the universe's expansion by working against gravity's tendency to pull galaxies together, the scientists said.

NASA calls dark energy "a complete mystery" in an online report on the phenomenon. The name "refers to the fact that some kind of 'stuff' must fill the vast reaches of mostly empty space in the universe in order to be able to make space accelerate in its expansion," it says.

"We were able to image dark energy in action, as it stretches huge supervoids and superclusters of galaxies," Istvan Szapudi, leader of the astronomy team, said in a news release.

Superclusters and supervoids are the largest structures known in the universe, according to the Institute for Astronomy.

There is only a 1-in-200,000 chance that the detection would occur by chance, so the finding is the best evidence to date of dark energy's stretching effect on vast cosmic structures, Szapudi said.

Superclusters are described as vast regions of space half a billion light-years across, with an unusually high concentration of galaxies. Supervoids are similar regions with below-average numbers of galaxies.

UH astronomer will lecture on search for ETs The Search for Extraterrestrial Intelligence will be discussed by University of Hawaii astronomer Gareth Wynn-Williams at 7:30 p.m. Aug. 12 at the Institute for Astronomy, 2680 Woodlawn Drive, Manoa. "SETI: If the Cosmic Telephone Rings, Should We Answer It?" is the title of the free public lecture. Wynn-Williams, born in London, has been an IFA professor for 30 years. He does interstellar research and is author of a book, "The Fullness of Space."

The UH astronomers made the discovery by measuring imprints left by superclusters and supervoids in microwaves that pass through them.

"When a microwave enters a supercluster, it gains some gravitational energy and therefore vibrates slightly faster," Szapudi said. As it leaves the supercluster, he said, "it should lose exactly the amount of energy.

"But if dark energy causes the universe to stretch out at a faster rate, the supercluster flattens out in the half-billion years it takes the microwave to cross it," Szapudi said. "Thus, the wave gets to keep some of the energy as it entered the supercluster."

Postdoctoral astronomer Mark Neyrinck said, "Dark energy sort of gives microwaves a memory of where they've been recently."

The scientists compared a database of galaxies with a map of cosmic microwave background radiation -- "the faint hiss of microwaves left over from the big bang."

They found microwaves were a little stronger if they had passed through a supercluster and a bit weaker if they passed through a supervoid.

"With this method, for the first time, we can actually see what supervoids and superclusters do to microwaves passing through them," said graduate student Benjamin Granett, first author of a paper on the discovery to be published in an upcoming issue of Astrophysical Journal Letters.

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