my recent articles |
| Astrophysicists spot earliest signs of dark energy |
|
13 April 2007, for Nature Network Boston Dark energy—thought to be driving our universe to expand at a faster rate—has been at work during most of the universe’s 14-billion-year history, a new study shows. Using the Hubble Space Telescope, a team of researchers, including two from the Harvard-Smithsonian Center for Astrophysics, has discovered 21 supernovas, distant exploding stars, most of which are at least half as old as the universe. This quadruples the number of known supernovas that are more than seven billion years old, and opens up a unique view on what was happening in the early universe. Scientists were astounded in 1998 when they found that the universe was expanding at an accelerated rate and not at a slower rate, as they had expected. This latest study is the earliest evidence of this accelerating expansion. Researchers have given the name “dark energy” to the force behind this cosmic acceleration, but no one is sure what it really is, except that it doesn’t fit with existing cosmological theories. For now, physicists are trying to get a handle on dark energy’s effects, such as the accelerating expansion of the universe.By looking at the brightness and color of supernovas, the researchers could tell how far away they were and how quickly they were moving away from us. By looking at these very old supernovas, the researchers were able to gauge the universe’s rate of expansion as far back as 9 or 10 billion years ago. The results also add confidence to earlier measures of cosmic acceleration, showing that dark energy’s effect has been fairly constant over most of the universe’s history. The research was published this week in the Astrophysical Journal. |