Nebula - Interstellar dust cloud. Plays havoc with sensors.
Dark Nebula - Nebula that blocks out visible light.
Asteroid field - Various sizes of rocks and ice.
Black hole - Dead star. Dangerous gravity pulls.
Pulsar- Spinning neutron star that send out radio and/or gamma waves.
Quasars - Solar system sized objects that are extremely bright and give off visible light, UV, infrared, x-rays, and even radio waves.
Magentar - Neutron star with a powerful magentic field and gives off x-rays and gamma rays. Starquakes give off extremely powerful gamma rays.
Worm holes- A hole in space/time that connects another part of space.
Supernova - A dying star exploding. You don't want to be near one.
Dyson Sphere - a ring of equipment surrounding a star to capture it's energy output.