""which kind of star is highly unlikely to be found in the halo of the milky way? "

The answer to the question above is O-star or O-type star.
The O-star is a kind of star which is highly unlikely to be found in the halo of the Milky Way. The O-star, also known as the O-type star, is a hot, blue-white type of star, which are usually found in regions of active star formation.

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