The astronomer who published his theory that the Sun is a motionless body at the center of the solar system with planets revolving around it on his deathbed was Nicolaus Copernicus.

However, it's important to note that:

* Copernicus did not die on his deathbed publishing his theory. He actually published his book "De Revolutionibus Orbium Coelestium" (On the Revolutions of the Heavenly Spheres) in 1543, the year of his death.

* He wasn't the first to propose a heliocentric model. Aristarchus of Samos, a Greek astronomer, proposed a heliocentric model around 250 BC, though it didn't gain traction.

* Copernicus's work was controversial. His model contradicted the geocentric model (Earth-centered) which was widely accepted at the time.

So, while Copernicus's theory was indeed published in the year of his death, it's inaccurate to say he published it on his deathbed. He worked on it for years, and his book was a culmination of his research.