Focus on this artwork and discuss the Back panel of the painting.
On the reverse of this painting is an image of what appears to be a meteor/meteorite or comet. Dürer's inspiration may have been the depictions of comets in the Nuremberg Chronicle of 1493. However, those woodcuts are highly stylized, and are not intended to show historical comets, whereas Dürer's image has the feel of an actual observation, as does the blazing star in Dürer's enigmatic engraving Melencolia I, published in 1514.
If Dürer's images do represent actual celestial objects, then there are three possible candidates. The first is the Comet of 
1491. Dr Sten Odenwald said that it "allegedly came to within 0.0094 AU on 1491 Feb. 20.0 TT, but the orbit of this comet is very uncertain"; NASA's website agrees with Odenwald's comment on the orbit.  The second is the Ensisheim meteorite. This was suggested by Ursula B Marvin ('The meteorite of Ensisheim – 1492 to 1992',(1992)), in relation to Melencolia I. This object fell in Alsace on 7 November 1492. The third is the comet of 1493, mentioned in the chronological section of Sir David Brewster's The Edinburgh Encyclopædia, which said it was: "seen before and after passing its meridian."
meridian Melencolia I Nuremberg Chronicle Alsace Ensisheim meteorite Dürer