Measurements suggest that light first arrived at Earth from the Cassiopeia A supernova about 300 years ago and that this supernova is about 10,000 ly distant from Earth.When did the explosion actually occur?

Question

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Based on the information given, we know that light first arrived at Earth about 300 years ago, and that the supernova is 10,000 ly distant from Earth. This means that the light we are seeing now actually left the supernova 10,000 years ago (300 years for the light to travel to Earth + 9,700 years for the light to travel from the supernova to Earth). Therefore, the explosion actually occurred about 10,300 years ago, or about 8300 B.C.

Measurements Suggest That Light First Arrived at Earth from the Cassiopeia