Stars

Distance = speed x time.
Time = 1 year = 365.25 days x 24 hours x 60 minutes x 60 seconds = 31,557,600 s
Distance = (3.0 x 10^8 m/s) x (31,557,600 s) = 9.47 x 10^15 m. One light-year is the distance light travels in a year, so we multiply the speed of light by the number of seconds in a year.

1. The Sun is a star.
2. The Sun is located in the Milky Way galaxy.
3. Other stars in the Milky Way are much further away from Earth than the Sun is.

Distance = (Number of light-years) x (Distance of 1 light-year)
Distance = 4.6 x 9.5 x 10¹⁵ m
Distance = 4.37 x 10¹⁶ m

This calculation uses the definition of a light-year to find the distance light travels in 4.6 years.

One light-year is the distance that light travels through a vacuum in one year. It is equal to 9.5 x 10¹⁵ meters.

1. Interstellar Cloud: Stars form from interstellar clouds of gas and dust, mainly hydrogen.
2. Protostar: The cloud collapses under gravity, increasing temperature.
3. Stable Star: Nuclear fusion begins; outward pressure from fusion balances inward gravity.
4. Red Giant/Supergiant: Hydrogen fuel depletes; core contracts, outer layers expand and cool.
5a. White Dwarf: For smaller stars, the red giant sheds its outer layers as a planetary nebula, leaving behind a white dwarf.
5b. Supernova/Neutron Star/Black Hole: For massive stars, the red supergiant explodes as a supernova. The core collapses to form a neutron star, or a black hole if the star is massive enough.

As the interstellar cloud collapses, its gravitational potential energy is converted into kinetic energy. The increased kinetic energy results in increased particle motion, causing the temperature of the gas and dust to rise.