In terms of the public reaction it received, the Astronomia Nova didn't fare much better than the Mysterium Cosmographicum. Once again, Kepler's peers didn't understand the profound importance of his work. The full significance of the two planetary laws did not become apparent until years later, when Newton used them to formulate his theory of universal gravitation. Until then, Kepler's system was little more than an aesthetic monstrosity. Even Kepler was dismayed by the loss of uniform circular motion – he disliked the idea of elliptical orbits as much as everyone else.
Although no one fully understood the ramifications of his work, it was accorded respect by the scientific community. Kepler was in a far different position than he'd been in ten years before. By the time the Astronomia Nova was published, Kepler was one of the most famous astronomers in Europe, primarily due to his title as the Imperial Mathematicus. He was also well respected for the other scientific research he'd done while working on the orbit of Mars, including the impressive work he'd done in the field of optics. In 1604, a new star had appeared in the sky and Kepler had proved that it was indeed a new star, not merely an atmospheric phenomena. As an indication of his newfound fame, the star became known as Kepler's Nova. While few recognized the Astronomia Nova for the landmark work that it was, the book only added to his prestige. Kepler's star was on the rise.
As one of Europe's top astronomical experts, Kepler was expected to have an opinion on any news in the field. The scientific community was eager to hear he had to say in 1610, when an Italian scientist named Galileo Galilei announced he had made a startling discovery. Galileo, who was a few years older than Kepler, was the first major astronomer to make use of a brand new tool for observing the stars: the telescope. In 1610, Galileo published his short book Sidereus Nuncius, or A Message From the Stars. He announced that he had discovered four new celestial bodies: the moons of Jupiter.
Kepler and Galileo had corresponded briefly in earlier years; in 1597, Galileo had complemented Kepler on his support of the Copernican system. In a later, Galileo admitted that he too supported it, but was hesitant to make that fact public. Kepler responded with a letter urging Galileo to get over his fears – a letter which Galileo may have taken as a personal affront, as he never responded.
Kepler and Galileo had not spoken for twelve years, but when the report of Galileo's observations came out, Kepler supported them. Kepler was the only one; the rest of the scientific community was quick to decry Galileo's discoveries. When Kepler requested that Galileo send him a telescope so that he could make an independent confirmation of Galileo's discoveries, Galileo ignored him. Frustrated and a bit embarrassed that he had staked his scientific reputation on a discovery of which he had no evidence, Kepler persevered. Finally, he was able to borrow the telescope of a nearby nobleman and publish Observation – Report on Jupiter's Four Wandering Satellites. It was the first independent confirmation of the existence of the moons of Jupiter.
But if Kepler's professional life was finally soaring, his personal life was falling apart. In 1611, Kepler's wife and favorite child died of the Hungarian Fever. Adding to this misery, the situation in Prague was becoming increasingly unstable. In 1611, Kepler's patron, Rudolph II, went insane and was forced to give up the throne; he died in January of 1612. While Kepler continued to serve as the Imperial Mathematicus, his new patron was not nearly as interested in astronomy as Rudolph II had been. The new emperor didn't care whether his imperial astronomer was by his side or across the country, so Kepler was free to leave Prague. The city was being torn apart by civil war, and Kepler decided to leave immediately.