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.
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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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Source: neatorama