Stars

2. How does a new star form?

The formation of a new star occurs in a similar way as the Sun did. A new star begins its formation with a cloud of interstellar gas and dust. This cloud is known as a nebula and collapses on itself as a result of its own gravity. The cloud's rotation forces it into a disk shape as the cloud contracts, and contains a hot condensed object at the center. This object is known as a protostar, which is brightest at infrared wavelengths. The condensed object will become a new star.

3. What causes a supernova to occur? Explain.

A supernova is a massive explosion that occurs when the outer portion of the star is blown off. Once reactions in the core of the star have created iron, no further energy-producing reactions can occur, and the core of the star violently collapses in on itself. As this is happening, protons and electrons in the core merge to form neutrons. Neutrons cannot be squeezed too closely together and their resistance to being squeezed creates a pressure that halts the collapse of the core, and therefore the core becomes a neutron star, which forms quickly while the outer layers of the star are still falling inward. The infalling gas rebounds when it strikes the hard surface of the neutron star and explodes outward which is the massive explosion that occurs.

4. Is the lifetime of a massive star shorter or longer than a star like the Sun? Why?

A massive star's lifetime is shorter than the lifetime of a star like the Sun. This is because the massive star is very luminous and therefore it uses up its fuel quickly. A star like the sun gradually becomes more luminous because the core density and temperature rise slowly and increase the reaction rate. It takes approximately 10 billion years for a star like the Sun to convert all of the hydrogen in its core into helium; therefore, these stars have a main sequence lifetime of 10 billion years.

5. In what ways is the evolution of a massive start similar to the evolution of the Sun, and in what ways is it different?

The evolution of a massive star and the evolution of the Sun are both similar and different. Both begin their lives in the same way, however a massive star begins its life much higher on the main sequence, with hydrogen being converted to helium. The main