When Edwin Hubble observed distant galaxies in the 1920s, he made the groundbreaking discovery that the universe is expanding. It was not until 1998, however, that scientists observing Type Ia supernovae further discovered that the universe is not just expanding but has begun a phase of accelerating expansion.
"To explain this acceleration, we need a source," says Joe Mohr, astrophysicist at LMU. "And we refer to this source as 'dark energy,' which provides a sort of 'anti-gravity' to speed up cosmic expansion." Scientifically, the existence of dark energy and cosmic acceleration are a surprise, and this indicates that our current understanding of physics is either incomplete or incorrect. The significance of the accelerating expansion was underscored in 2011 when its discoverers received the Nobel Prize in Physics. "Meanwhile, the nature of dark energy has become the next Nobel Prize winning problem," says Mohr.
Now I-Non Chiu from National Cheng Kung University in Taiwan, working in collaboration with LMU astrophysicists Matthias Klein, Sebastian Bocquet, and Joe Mohr, has published a first study of dark energy using the eROSITA X-ray telescope, which focuses on galaxy clusters.
On the trail of a mysterious force in space
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