Help with astronomy homework?

I have a question for my astronomy class that I do not know how to answer:

"You are observing a star that is 100 million light years away. you can tell the star is 10 million years old and will have a total life time of 50 million years, ending in a supernova."

How old does the star appear on earth?

How long will it be before we get the light from the supernova event?

has the supernova already occurred? If so when?

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  • 9 years ago
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    Since "you can tell the star is 10 million years old," it appears to be 10 million years old on Earth.

    We will get the light from the supernova in 40 million years, at the end of the star's life as observed from Earth.

    Whether you think the supernova has already occurred depends on your definition of time and simultaneity. Here is what I *think* your teacher wants: The supernova occurred 60 million years ago. Its light has traveled 60 million light years since it occurred, and that light is still 40 million light years from us, which is why it will not arrive for another 40 million years.

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