What is the meaning of 妖星?
well, "妖星" is a category name of observable astronomical / meteorological  phenomenons, those are assigned as "bad omen".

in the book "靈臺秘苑" by 庾季才, in volume 15, it was defined as:

靈臺秘苑　卷十三⋯卷十五　page 195


  妖星者﹒五行五星之變﹒天地惡氣之所生也


roughly, means "evil star (妖星), the so called (者), [is] the rebels of (之變) five elements (五行), [and / or] five planets (五星), produced (生) by (所) the bad force (惡氣) from the sky and earth (天地)"



afterward, the author listed 40+ entries in this category "妖星", an interesting point is:

"彗星", "孛星" &amp; "長星", comets;  &amp; "客星", nova; are also listed as "妖星"

i would suggest you find someone who can read literary chinese, and understand astrology / astronomy to help you. the google translate cannot handle literary chinese, the link provided is, . . . :(

last, the english book "stars of jade" by julius d w staal, would give you some basic ideas about "chinese astronomy".

have fun :)