Astronomy Exam 2 Part 2

In a supernova explosion, all of the given statements are true. The star can shine as brightly as billions of stars due to the immense energy released during the explosion. Elements heavier than iron are formed through nuclear reactions in the intense heat and pressure of the explosion. Material that later formed the Earth and humans is distributed between the stars as the explosion scatters matter into space. Additionally, matter is ejected at extremely high speeds, reaching tens of thousands of kilometers per second. Therefore, the correct answer is E. All of the above.

The most important characteristic of a star for determining its lifetime is its mass. The mass of a star determines its internal pressure and temperature, which in turn determines the rate at which nuclear fusion reactions occur in its core. These fusion reactions provide the energy that allows a star to shine. A star with a higher mass will have a higher core temperature and a faster rate of fusion, leading to a shorter lifetime. Conversely, a star with a lower mass will have a lower core temperature and a slower rate of fusion, resulting in a longer lifetime. Therefore, the mass of a star is crucial in determining how long it will live.

A one solar mass star primarily uses hydrogen as its nuclear fuel during the main sequence phase of its evolution. As hydrogen fuses into helium in the star's core, it releases a tremendous amount of energy through nuclear fusion reactions. This process continues until the hydrogen in the core is depleted. At this point, the star begins to evolve and expand, and helium fusion starts to occur in the core. However, the primary nuclear fuels used over the entire evolution of a one solar mass star are hydrogen and helium.

A white dwarf is the correct answer because it is the remnant core of a star that has exhausted its nuclear fuel. It is very dense because it has a mass similar to that of the Sun but is compressed into a much smaller volume, about the size of Earth. This high density is a result of gravitational forces that are no longer balanced by the outward pressure from nuclear fusion.

Particles of matter, particles of antimatter, visible light, and X-rays cannot escape from inside the event horizon of a black hole. The event horizon is the boundary beyond which nothing, not even light, can escape the gravitational pull of the black hole. Therefore, any form of matter or energy that crosses the event horizon is trapped inside the black hole, making the correct answer E. None of the above.

A white dwarf is supported against collapse by electron degeneracy pressure. This is because the white dwarf is composed of degenerate matter, where electrons are packed so tightly that they cannot occupy the same quantum state, leading to an increase in pressure. This pressure counteracts the force of gravity, preventing the white dwarf from collapsing further. Neutron drip, neutrino pressure, neutron degeneracy pressure, and a central black hole do not play a role in supporting a white dwarf against collapse.

Iron does not liberate energy when burned via nuclear fusion in the center of a star because it is the most stable element with the highest binding energy per nucleon. Fusion reactions involving iron require more energy to occur than they release, making it an end point for nuclear fusion in stars.

All of the statements A, B, C, and D are true regarding pulsars. Pulsars have very strong magnetic fields, they rotate very rapidly, they are neutron stars, and they have a density approximately equal to the density of an atomic nucleus. Therefore, the correct answer is E, All of the above are true.

When a neutron star forms, it is a result of a massive star collapsing under its own gravity. As the star collapses, its angular momentum is conserved, which means that the rotational speed increases. This is similar to an ice skater spinning faster when they pull their arms in. Therefore, the correct answer is D, it conserved angular momentum when it collapsed.

If two stars have the same spectral type, it means that they have similar patterns of spectral lines, indicating that they have similar surface temperatures. The spectral type of a star is determined by its surface temperature, so if two stars have the same spectral type, it implies that they have approximately the same surface temperature. The other options, such as mass, parallactic distance, chemical composition, and luminosity, are not necessarily related to the spectral type of a star.