The observations of the angular diameter of certain stars. We know now (and Galileo did later show) that from our distance stars are point sources of light. Tycho Brahe however estimated up to 2 minutes of arc for the brightest stars. This diameter was actually caused by bloom because the human eye isn't a perfect lens.
No stellar parallax was observed at the time. The reasoning was that with the apparent diameter of 2 minutes and no observable parallax stars would have to be absolutely massive compared to the sun (far bigger than any actual super giant). This reasoning is correct; it is only Brahe's observations that are incorrect.
The observations of the angular diameter of certain stars. We know now (and Galileo did later show) that from our distance stars are point sources of light. Tycho Brahe however estimated up to 2 minutes of arc for the brightest stars. This diameter was actually caused by bloom because the human eye isn't a perfect lens.
No stellar parallax was observed at the time. The reasoning was that with the apparent diameter of 2 minutes and no observable parallax stars would have to be absolutely massive compared to the sun (far bigger than any actual super giant). This reasoning is correct; it is only Brahe's observations that are incorrect.