Star Size Illusion

On the topic of the size of the stars, see this story which describes that the visible stars are truly huge. Since a heliocentric model requires distant stars, the measurable diameters of the stars shows that the sizes would need to be of tremendous proportions, and was one of the early controversies in astronomy. The geocentric model's closer stars seemed more reasonable. In response Copernicans claimed the mystery of God and later ones postulated an "optical illusion".

The Popular Creation Story of Astronomy is Wrong
The Popular Creation Story of Astronomy Is Wrong (Archive) Christopher M. Graney

The old tale about science versus the church is wide of the mark.

The Case Against Copernicus — Scientific American
On this same topic also see this Scientific American article about the history of Heliocentrism vs. Geocentrism starting on p.75:

The Case Against Copernicus — Scientific American



The Illusion
The later Copernicans argued that the size of the visible of the stars were an illusion, and cite an observation of stars winking out when touching the edge of the Moon:

Galileo's Observations
Interestingly, astronomer Galileo Galilei himself claimed to be able to divide stars. Galileo claimed to see an effect which should be impossible according to the star size illusion.

Professor Graney relates his claims:

Strange Tales of Galileo and Proving: Splitting the Stars


 * GalileoStar1.jpg


 * A star seen through a telescope of very small aperture. This illustration is from the Treatise on Light by the nineteenth century astronomer John Herschel (son of William Herschel). Center—simulated view of the star supposedly divided in half by Galileo’s distant beam. Right—simulated view showing how, after a period of months, the Earth’s motion relative to the star might cause the position of the beam against the star to change ever so slightly, proving that Earth indeed moves. If, after one year, the star is once again divided in half by the beam, then Earth’s motion around the sun (in which it returns annually to the same place) will be clearly demonstrated.


 * GalileoStar4.jpg


 * Galileo’s divided star could never happen!

This observation is impossible, of course, and so Professor Graney declares that Galileo is a liar.