Infrared universe: Hubble spies dark energy clue

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  • Published: Feb 1, 2012
  • Author: David Bradley
  • Channels: Infrared Spectroscopy
thumbnail image: Infrared universe: Hubble spies dark energy clue

Changing the universe

NASA's Hubble Space Telescope has looked deep into near-infrared of the distant universe to detect the feeble afterglow of a star that exploded more than 9 billion years ago. The research offers the first glimpse of constraints to help us explain dark energy.

In the late 1990s, the universe changed. The mathematical underpinning the Big Bang theory no longer worked. Astronomers had spotted that remnants of ancient stars that exploded billions of years ago, Type Ia supernovae, known colloquially as "standard candles" because of their unflickering luminosity, seem to be moving away from us faster and faster. According to Big Bang theory, the universe is expanding, but it should either be slowing down as gravity drags the matter back together, or if its total mass is inadequate it would simply expand forever. But, the evidence from the standard candles suggested that a mysterious invisible force is working against gravity. This "force" known as dark energy pervades the universe and is causing an acceleration of the expansion of the universe.

Unfortunately, scientists have absolutely no idea what dark energy is. They know nothing of its origins nor ultimately how it might affect the evolution of the universe. Such a puzzle cannot be left to its own devices and several large research teams across the globe have been working to develop astronomical technology to help them find an answer. This new sighting is the first in what has been described as an ambitious survey that could allow astronomers and cosmologists to put constraints on dark energy.

Building on Hubble

"This new observation builds upon the revolutionary research using Hubble that won astronomers the 2011 Nobel Prize in Physics, while bringing us a step closer to understanding the nature of dark energy which drives cosmic acceleration," says NASA's John Grunsfeld. As an astronaut, Grunsfeld visited Hubble three times, performing a total of eight spacewalks to service and upgrade the observatory.

The SN Primo stellar explosion is a Type Ia supernovae, one of many distant, and so ancient, bright beacons that act as universal distance markers that have helped cosmologists pin down the rate of expansion of the universe. Type Ia supernovae are thought to occur when a white dwarf star, the burned-out core of "normal" star, attracts enough material from a companion star to cause a supernova explosion.

SN Primo, which was discovered by a three-year Hubble program is the most distant, and so oldest known, Type Ia supernova. Near-infrared spectroscopic observations of SN Primo confirmed its distance. However, investigating these supernovae more closely will help astronomers decide whether or not they are still dependable cosmic distance markers across an epoch of the universe stretching back to just a few billion years after the Big Bang.

The CANDELS+CLASH Supernova Project exploits the sharpness and versatility of Hubble's Wide Field Camera 3 (WFC3) to search for supernovae in the near-infrared and uses the spectral data to confirm distance. CANDELS is the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey and CLASH is the Cluster Lensing and Supernova Survey with Hubble.

"In our search for supernovae, we had gone as far as we could go in optical light," explains lead investigator on the project Adam Riess of the Space Telescope Science Institute and The Johns Hopkins University in Baltimore, Maryland. "But it's only the beginning of what we can do in infrared light. This discovery demonstrates that we can use the Wide Field Camera 3 to search for supernovae in the distant universe."

Popcorn supernova

"If we look into the early universe and measure a drop in the number of supernovae, then it could be that it takes a long time to make a Type Ia supernova," adds team member Steve Rodney of JHU. "Like popcorn kernels in a pan waiting for the oil to heat up, the stars haven't had enough time at that epoch to evolve to the point of explosion. However, if supernovae form very quickly, like microwave popcorn, then they will be immediately visible, and we'll find many of them, even when the universe was very young. Each supernova is unique, so it's possible that there are multiple ways to make a supernova," he explains.

If it turns out that Type Ia supernovae deviate from the expected norm, then this should allow astronomers to measure the effect of dark energy even more precisely. The researchers presented their new data to a meeting of the American Astronomical Society meeting in Austin, Texas on 11th January 2012.

 



The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

Credit: NASA - NASA's Hubble Space Telescope has looked deep into near-infrared of the distant universe to detect the feeble afterglow of a star that exploded more than 9 billion years ago. The research offers the first glimpse of constraints to help us explain dark energy.
SN Primo

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