By using galaxies as giant gravitational lenses, an international group of astronomers using the NASA/ESA Hubble Space Telescope have made an independent measurement of how fast the Universe is expanding. The newly measured expansion rate for the local Universe is consistent with earlier findings. These are, however, in intriguing disagreement with measurements of the early Universe. This hints at a fundamental problem at the very heart of our understanding of the cosmos.
The Hubble constant -- the rate at which the Universe is expanding -- is one of the fundamental quantities describing our Universe. A group of astronomers from the H0LiCOW collaboration, led by Sherry Suyu (associated with the Max Planck Institute for Astrophysics in Germany, the ASIAA in Taiwan and the Technical University) used the NASA/ESA Hubble Space Telescope and other telescopes [1] in space and on the ground to observe five galaxies in order to arrive at an independent measurement of the Hubble constant [2].
The new measurement is completely independent of -- but in excellent agreement with -- other measurements of the Hubble constant in the local Universe that used Cepheid variable stars and supernovae as points of reference heic1611.
However, the value measured by Suyu and her team, as well as those measured using Cepheids and supernovae, are different from the measurement made by the ESA Planck satellite . But there is an important distinction -- Planck measured the Hubble constant for the early Universe by observing the cosmic microwave background.
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