How did astronomers rule out the MACHO dark matter hypothesis?

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Astronomers ruled out the MACHO dark matter hypothesis by using microlensing observations. Microlensing occurs when a massive object passes in front of a background star, causing a temporary increase in brightness. If MACHOs were the primary source of dark matter, then we would expect to see more of these microlensing events. However, the observations did not match up with the predictions made by the MACHO hypothesis, leading scientists to rule it out as a viable explanation for dark matter.

How Did Astronomers Rule Out the MACHO Dark Matter Hypothesis