What star in the milky way passes all five tests scientists require for it to be a candidate for extraterrestrial life?

Proxima Centauri

Alpha Centauri passes five tests which is conducted on extra-terrestrial life.

Explanation:

Alpha Centauri is a three-star system in the Milky Way which is closer to the sun and could possibly provide extra-terrestrial life. The three stars are Alpha Centauri A, Alpha Centauri B, and finally the Proxima Centauri. For a planet to be listed as habitable like earth it must pass five conditions.

A closer look at the three stars separately shows that Alpha Centauri A passes all the conditions, while Alpha Centauri B passes only 4 and fail to meet one criterion. However, Proxima Centauri is excluded since it doesn't qualify.