As part of the Chicago-Carnegie Hubble Program, astronomers using the NASA/ESA/CSA James Webb Space Telescope have performed new measurements of the Hubble constant. Their results are consistent with the current standard Lambda cold dark matter (ΛCDM) model, without the need for the inclusion of additional new physics.
“The new evidence is suggesting that our Standard Model of the Universe is holding up,” said University of Chicago’s Professor Wendy Freedman.
“It doesn’t mean we won’t find things in the future that are inconsistent with the model, but at the moment the Hubble Constant doesn’t seem to be it.”
There are currently two major approaches to calculating how fast our Universe is expanding.
The first approach is to measure the remnant light left over from the Big Bang, which is still traveling across the Universe.
This radiation, known as the Cosmic Microwave Background, informs astronomers about what the conditions were like at early times in the Universe.
Professor Freedman and colleagues specialize in a second approach, which is to measure how fast the Universe is expanding right now, in our local astronomical neighborhood.
Paradoxically, this is much trickier than seeing back in time, because accurately measuring distances is very challenging.
Over the last half century or so, scientists have come up with a number of ways to measure relatively nearby distances.
One relies on catching the light of a particular class of star at its peak brightness, when it explodes as a supernova, at the end of its life.
If we know the maximum brightness of these supernovae, measuring their apparent luminosities allows us to calculate its distance.
Additional observations tell us how fast the galaxy in which that supernova occurred is moving away from us.
Professor Freedman has pioneered two other methods that use what we know about two other types of stars: red giant stars and carbon stars.
However, there are many corrections that must be applied…
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