For years, red giants were thought to have the same peak brightness. Because of this characteristic, scientists have used this knowledge as basis in estimating cosmic distances.
It’s hard to know how far away a star is without knowing its intrinsic brightness — a star may appear dim because it’s very far away, or just because it’s dim, or both. Because red giants always peak at a certain brightness, they can act as distance markers across the universe, giving astronomers cosmic landmarks to measure the space between Earth and far-off galaxies.
But what if some red giants are dimmer than others? This could put previous calculations in doubt.
That slight shift could make a big difference to cosmology, and particularly to estimates of the universe’s expansion rate — a number known as the Hubble constant.
More details about this over ScienceNews.
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