An extremely massive star can collapse until it is so dense that nothing, not even light, can escape from its immediate vicinity. This type of object is called a

A pulsar is a highly magnetized, rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles. While pulsars are remnants of massive stars, they are not regions of space where light cannot escape; rather, they are detectable due to their periodic emissions, making them fundamentally different from black holes.

A nebula is a massive cloud of dust and gas in space, often serving as a stellar nursery where new stars are born. Unlike black holes, nebulae do not possess the extreme gravitational pull that prevents light from escaping; instead, they are often illuminated by nearby stars or are in the process of star formation.

A white dwarf is the remnant core of a medium-sized star that has exhausted its nuclear fuel and shed its outer layers. While white dwarfs are dense, they do not have the gravitational force needed to prevent light from escaping, distinguishing them from black holes, which exhibit this property due to their immense mass.