(Solved): Johannes Kepler observed a supernova about 400 years ago and measurements indicate that this superno ...

Johannes Kepler observed a supernova about 400 years ago and measurements indicate that this supernova was about 20,000 light years away from the Earth. When did the explosion actually occur? Select one: out of 3. 400 years ago, or about 1600 A.D. Qquestion b. 19,600 years ago, or about

c. 20,400 years ago, or about 18,400 B.C. d. It is not possible to say when it occurred from the information given.