A new sky survey finds stars and galaxies are dimming — releasing far less energy than even a few billion years ago
You won’t be alive 100 billion years from now? Don’t worry. You won’t be missing much. Astronomers say that by then, the universe will be dark, empty and boring.
This new finding comes from looking at more than 200,000 galaxies. The energy they are producing today is about half of what it was 2 billion years ago. In other words, the universe is fading. More stars are dying than are being born. And as space continues to expand, things will get farther apart. With the stars’ falling output of light now spread over a broader expanse of space, the universe will dim even more.
Scientists described the new assessments on August 10. Their presentation was part of the International Astronomical Union XXIX General Assembly in Honolulu, Hawaii.
“There’s not going to be a single cataclysmic event” to end the universe, notes Simon Driver. He’s an astronomer at the University of Western Australia in Crawley. He also heads the Galaxy and Mass Assembly (GAMA) project. It’s one of the largest sky surveys ever made. And this survey shows “a slow decline” in the light being emitted far and wide.
FLY THROUGH Australian astronomer Luke Davies takes viewers on a “fly through” of our universe. Along the way, he points out that the celestial objects we’re passing are getting older. Some are becoming quite elderly. W. Parr, M. Swinbank and P. Norberg/ ICRAR
The findings aren’t a complete surprise. Scientists had believed for years that the universe was cooling and dimming. Earlier studies had showed that was true for a few types of energy — wavelengths of light — as measured in certain areas of the sky. But the new GAMA study now shows the same thing has been happening in large sections of the universe and in every direction. To show that general dimming, the scientists examined 21 different wavelengths (colors or energy levels) of light.
Concludes Driver, “Any way we slice or dice it, we find very hard, empirical evidence that the universe is slowing down.”
The GAMA scientists looked deep into the universe. They studied light that came from so far away, it was more than two billion years old by the time it arrived. “We’re drilling a core sample through the universe,” Driver explains. “It’s like a fossil record.”
The astronomers peered at large sections of space in five directions out from Earth. They made their observations using telescopes around the world. These included some of the largest and most powerful on Earth. Then the scientists put all of their gathered images together and calculated how much energy was being released by stars, galaxies and other objects millions and billions of years ago. They compared this to what’s being released today.
“This is one of the most comprehensive maps we’ve ever been able to make of the universe,” says Andrew Hopkins. This GAMA astronomer works at the Australian Astronomical Observatory in North Ryde, New South Wales. Still, he notes, this study looked at less than one percent of the universe.
Some people might find the data “bleak,” Hopkins admits. In a sense, it indicates the universe is dying. But he’s inspired by the thought of all the new scientific discoveries that may come from these data. The ancient light now reaching Earth comes from “the youthful, energetic universe,” he says. So, “We’re probing the exciting, early stages of the universe’s history.”
But there’s no sugar-coating the conclusions. The universe is getting old. “Just as we become less active in our old age, the same is happening to the universe,” notes Luke Davies. He works at the International Centre for Radio Astronomy Research (ICRAR) in Perth, Western Australia. The universe, he quips, is “well past its prime. Its active, athletic, partying days are behind it.”
Adds Driver, the universe is sliding gently into old age. He says you might think of it as having “basically sat down on the sofa, pulled up a blanket and [prepared] to nod off for an eternal doze." Fortunately, that doze is still billions of years away.
(for more about Power Words, click here)
astronomy The area of science that deals with celestial objects, space and the physical universe as a whole. People who work in this field are called astronomers.
cataclysm An enormous, violent, natural event. A meteor hitting Earth and wiping out most living species would qualify as a cataclysmic event.
empirical Based on observation and data, not on theory or supposition.
fossil Any preserved remains or traces of ancient life.
galaxy A massive group of stars bound together by gravity. Galaxies, which each typically include between 10 million and 100 trillion stars, also include clouds of gas, dust and the remnants of exploded stars.
star The basic building block from which galaxies are made. Stars develop when gravity compacts clouds of gas. When they become dense enough to sustain nuclear-fusion reactions, stars will emit light and sometimes other forms of electromagnetic radiation. The sun is our closest star.
telescope Usually a light-collecting instrument that makes distant objects appear nearer through the use of lenses or a combination of curved mirrors and lenses. Some, however, collect radio emissions (energy from a different portion of the electromagnetic spectrum) through a network of antennas.
universe The entire cosmos: All things that exist throughout space and time. It has been expanding since its formation during an event known as the Big Bang, some 13.8 billion years ago (give or take a few hundred million years).
wavelength The distance between one peak and the next in a series of waves, or the distance between one trough and the next. Visible light — which, like all electromagnetic radiation, travels in waves — includes wavelengths between about 380 nanometers (violet) and about 740 nanometers (red). Radiation with wavelengths shorter than visible light includes gamma rays, X-rays and ultraviolet light. Longer-wavelength radiation includes infrared light, microwaves and radio waves.
A. Grant. “Dust erases evidence of primordial gravity waves.” Science News for Students. February 10, 2015.
B. Geiger. “We are stardust.” Science News for Students. February 28, 2014.
S. Ornes. “New, older age for the universe.” Science News for Students. April 4, 2013.
S. Ornes. “When the universe began … again.” Science News for Students. December 6, 2010.
Read about the age of the universe here, in a piece presented by the American Institute of Physics.
Original Scientific Paper: S.P. Driver et al. Galaxy and Mass Assembly (GAMA): Panchromatic Data Release (far-UV|far-IR) and the low-z energy budget. Posted at arXiv.org on August, 11, 2015. http://arxiv.org/abs/1508.02076.