How did planetary nebulae get their name?
Planetary nebulae were mistaken for planets and hence their name.
Nebulas are named after William Herschel, who believed they were planets when he observed them in the 1780s. The word "nebula" is derived from the Latin word for cloud.
In reality, planetary nebulae are the remains of stars that are too small to explode as supernovae; material is ejected from the star to create these relatively short-lived structures, which only last tens of thousands of years.
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When viewed through early telescopes, planetary nebulae resembled planets, hence their name.
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When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.
When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.
When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.
When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

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