What is the Habitable Zone?

DescriptionIn astronomy and astrobiology, the circumstellar habitable zone, or simply the habitable zone, is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric
pressure.

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The habitable zone is the not-too-hot, not-too-cold region around a star where liquid water can exist on a planet’s surface.
Liquid water is a key ingredient for life as we know it, so exoplanets in their stars’ habitable zones are compelling places to search for life.
In certain cases liquid water can exist outside of a star’s habitable zone, such as Europa’s subsurface ocean.

Your answer is going to be a. i know my biology

The answer is one amu.