In the designation Kepler-186f, what does the letter 'f' signify about the planet's discovery?

Answer

It is the sixth planet found orbiting the star Kepler-186

Exoplanet naming conventions start with a letter designating the order of discovery around a specific star; thus, 'f' indicates it is the sixth planet found orbiting that star.

In the designation Kepler-186f, what does the letter 'f' signify about the planet's discovery?
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