Scientists Meet Scientists – Wednesday Coffee Talk by Prof. Dr. Sherry Suyu on “New Measurement of the Universe’s Expansion Rate Using Cosmic Lenses”


On December 2nd, Prof. Dr. Sherry Suyu (TUM Department of Physics) will give a talk entitled “New Measurement of the Universe’s Expansion Rate Using Cosmic Lenses”.

Knowing the precise value for the Hubble constant, a measure for how fast the universe expands, is important for determining the age, size and fate of our cosmos. Unravelling this mystery is one of the greatest challenges in astrophysics. Using cosmic lenses, Professor Suyu and her team determined the universe’s expansion rate, completely independent of any previous method. This latest value for the Hubble constant represents the most precise measurement yet using gravitational lensing, where the gravity of a foreground galaxy acts like a giant magnifying lens, amplifying and distorting light from background objects. Through the lensing effect, multiple images of the same background object appear around the foreground galaxy. Depending on the position of the object behind the foreground galaxy, the light of the different images has to travel over unlike distances to reach the observer. Brightness fluctuations of the background object therefore arrive at different times for each of the multiple images. The time delay can be measured in lensed quasar systems, where quasars are extremely distant cosmic streetlights produced by active black holes.

Professor Suyu and her team’s result further strengthens a troubling discrepancy between the expansion rate calculated from measurements of the local universe and the rate as predicted from background radiation of the early universe. The new study adds evidence to the idea that new theories may be needed to explain the underlying physics (TUM press release).

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