The most fascinating exciting things I've learned in the NASA program thus far are the extremes that occur in space.

Extreme velocities
Jupiter, saturn, other planets and objects: things that move with such velocity that it creates distortions in light wavelengths called redshift and blue shift. 

Extreme masses
Black holes. A result from explosive supernovas from massive Red Giants. The insanely large mass of these stars could be compressed into extremely small areas, and that this results in an object so massive that even light itself could not escape its gravitational pull.

Extremely powerful magnets
Strong magnetic fields produces from neutron stars supply the power needed to generate large quantities of gamma rays. 
hot interior rotates with plasma= normal magnetic fields. 
Core changes for hydrogen to helium etc then to iron core. 
Iron core grows bigger until it could no longer sustain itself
Supernova occurs
the core is compressed. This leaves an enormously powerful magnetic field.

(earth controls a magnetic field=1 gales. An exploding Neutron star=10^15 gales. The magnet is strong enough to effect the structure of atoms.)

Extreme frequencies
Gamma beams that could kill people. Cause cells to ionize and be killed. Powerful enough to pierce though lead, and strong enough to scan through metal containers.
(If the one in a million year gamma ray bursts in our galaxy hit wrath directly, all life will end)