The star has a life cycle that distinguishes its beginning from its death. At its birth, the star exists as a cloud of gas and dust. Over time, the cloud surrounding the star disperses, shrinking its size. Simultaneously, hydrogen gas from within the star ignites. The fire burns first the inner core of the star, then works its way into the outer shell. Abundant energy, or heat, is released as the star burns, causing it to shine and expand. Eventually, the fire will cool as all of the hydrogen is burned and the star will appear red. This stage of the star is known as the red giant. The outer contents of the star will blow away, leaving the cooling core. The core itself fades progressively until it can no longer be seen and the star is now known as a white dwarf.
The life cycle of a star depends greatly on its size. Most stars are smaller--about the size of the sun--and burn slowly, lasting a long time. In contrast, huge stars, those that are greater than the sun, burn very fast. These stars are rare and burn so quickly that they explode upon death instead of fading over time.
Although black holes are a popular subject of astronomy, their occurence is rare. Stars of very large size burn quickly and live shortly. After explosion, some large stars exist as black holes. A black hole is a dense area located in a very small amount of space. The gravity of a black hole does not allow anything, even light, to escape so an object that enters one is essentially lost for all of time.
The majority of stars in our galaxy are smaller, or about the size of the sun, and live for a long time. These stars fade away after billions of years and last as white dwarfs.
The death of one star is the birth of a new one. When some large stars explode, their contents are released to mix with hydrogen and other atmospheric gases. Eventually, these substances will be the beginnings of another star.