_____ describes the life cycle of a star.
It's not color
The life cycle of a star can be described in several stages:
1. Nebula: The first stage begins with a giant cloud of gas and dust called a nebula. Gravity causes the nebula to collapse and condense.
2. Protostar: As the nebula collapses, it forms a dense core called a protostar. At this stage, the protostar is not yet hot enough to produce nuclear fusion.
3. Main Sequence: Once the protostar reaches a temperature of about 10 million degrees Celsius, nuclear fusion ignites in its core. This initiates the main sequence phase, during which the star fuses hydrogen into helium. This phase is the longest and stablest period in a star's life, lasting billions of years.
4. Red Giant or Supergiant: As the star consumes its hydrogen fuel, it starts to exhaust its core's nuclear fuel. The core contracts, and the outer layers of the star begin to expand, causing the star to swell in size and become a red giant (for lower-mass stars) or a red supergiant (for higher-mass stars).
5. Planetary Nebula or Supernova: Once the star exhausts its nuclear fuel, its fate depends on its mass. Lower-mass stars shed their outer layers, forming a colorful cloud of gas and dust called a planetary nebula. Higher-mass stars, on the other hand, undergo a violent explosion known as a supernova.
6. White Dwarf or Neutron Star/Black Hole: After a planetary nebula or supernova, what remains of the star depends on its mass. In the case of lower-mass stars, the core collapses inward and becomes a white dwarf—a small, dense remnant composed mostly of carbon and oxygen. In the case of higher-mass stars, the core may collapse even further to form a neutron star or a black hole.
It's important to note that the exact details of a star's life cycle can vary depending on its mass.