Question

Difference between asters and spindle fibres.

Answer 1

Aster simply means star, i.e. a point from which something radiates. In this case, that something is microtubules. 
All the fibers that radiate from centrosome are called SPINDLE FIBERS(also microtubules). They are called spindle fibers because with the union of chromosomes, they form the mitotic spindle. 
Microtubules are of three types:
1)Kinetochore microtubules: those microtubules that attach to chromosomes.

2)Interpolar microtubules: those microtubules that bind to the microtubules of the opposite pole.

3)Astral microtubules: those microtubules that attach to neither chromosomes nor to each other, but they end abruptly in cortical cytoplasm. (It is believed that astral microtubules help the centrosomes to stay firmly at their position.

Answer 2

aster simply means star.
all the fibres that radiate from centrosome are called spindle fibres