Appearing in 1604, it is the most recent supernova in the Milky Way galaxy to have been unquestionably observed by the naked eye,[3] occurring no farther than 6 kiloparsecs (20,000 light-years) from Earth.

The interstellar space might be filled with something similar to our atmosphere, as in the physics of the Stoics, to which Tycho had referred in his lengthy account of the nova of 1572.

And if the material of the firmament resembled that of bodies here below, a theory of motion built on experience with objects within our reach might apply also to the celestial regions.

When Kepler replied later that year, he simply observed that by including a broader range of data Roeslin could have made a better argument.

[14] The supernova remnant of SN 1604, Kepler's Star, was discovered in 1941 at the Mount Wilson Observatory as a dim nebula with a brightness of 19 mag.

[17] The available evidence supports a type Ia supernova as the source of this remnant,[1] which is the result of a carbon-oxygen white dwarf interacting with a companion star.

[1] There is evidence for interaction of the supernova ejecta with circumstellar matter from the progenitor star, which is unexpected for type Ia but has been observed in some cases.

[16] Observations of the remnant are consistent with the interaction of a supernova with a bipolar planetary nebula that belonged to one or both of the progenitor stars.

A remnant rich in nitrogen and silicon indicates that the system consisted of a white dwarf with an evolved companion that had likely already passed through the asymptotic giant branch stage.