 A few years later, in his Letters on Sunspots (1613), Galileo offered new telescopic evidence that supported the Copernican theory. But these observations also served as additional reasons for dissolving the celestial-terrestrial distinction. One was that the sun is not an immutable aetherial sphere, but has changing spots (maculae) on its surface. Another was that the sun rotates circularly around its axis, like the Earth. A third was the discovery that Venus undergoes a full sequence of phases (like the moon), which entails that Venus revolves around the sun, and suggests that the Earth is likewise a celestial body moving around the sun. Certainly the phases of Venus contradicted the Ptolemaic ordering of the planets.