Answer these all questions.
Q1. The matter that makes up a star today may have been part of another star that died billions of years ago. How is it possible ?
Q2. When viewed from the Earth, are star and a blue star appear to be equally bright. What could you infer about these two stars ?
Q3. Why is the light-year a useful unit for measuring distance to stars as compared to kilometers ?
Answers
Answer:
Q1. It’s not only possible, it happens quite a bit especially for distant starts. Since starts have lifespans measured in billions of years, it it unlikely that a star like our closest neighbor is gone because it’s only 4 light years away (what are the changes that it was gone in the last 4 years). However, for many stars that are billions of light years away, it is almost a certainty.
Q2. Not much. When we’re talking astronomy it’s important to to remember that the things we observe appear the way they do relative to us as observers here on Earth. The APPARENT brightness of these stars (brightness how it appears from Earth) tells us virtually nothing.
The reason for this is explained nicely in this image:
A dim star, B, that is closer to its observer and a brighter star, A, that is farther away may appear equally bright from our perspective, its all relative.
What if we did know the intrinsic brightness of our two stars? The most prominent mechanisms that drive luminosity in stars are surface area and temperature. But what drives these two things are mass, if we know these stars have the same intrinsic brightness they likely have similar masses.
Q3. The main reason for using light years, however, is because the distances we deal with in space are immense. If we stick to miles or kilometers we quickly run into unwieldy numbers just measuring the distance to the nearest star: a dim red dwarf called Proxima Centauri that sits a mere 24,000,000,000,000 miles away!
Explanation:
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