Astronomy Chapter 9 Quiz

Giant stars are larger in diameter than the Sun.

Giant stars are more luminous than the Sun, larger in diameter than the Sun, and cooler than B stars. They are located above the main sequence stars on the H-R diagram.

HR 5337 on the given diagram is most similar to the Sun.

Alnilam, based on the provided diagram, has the highest surface temperature.

Based on the diagram, Antares has the largest radius.

Stars with the smallest radius are found in the lower left corner of the H-R diagram.

Observations of eclipsing binary stars allow calculation of both the masses and sizes of the individual stars.

Doppler shift observations of a spectroscopic binary allow astronomers to calculate the masses of individual stars.

Binary stars can be detected by observing their visual separation, proper motion patterns, eclipses, and spectral features.

The mass of a visual binary star system can be determined from the orbital period and the size of the star's orbit.

Sirius B, a white dwarf star, has a mass similar to the Sun because it is part of a binary system with Sirius A.

90% of stars are on the main sequence of the Hertzsprung-Russell diagram.

Lower main sequence stars are the most common type of star.

Upper main sequence stars and white dwarfs are among the least common types of stars.

If two stars emit the same light, the farther star appears dimmer.

Stars appearing unusually bright or exhibiting periodic movements against the background can indicate proximity to Earth.

The apparent change in the frequency of sound (or light) emitted by a moving source, like a train horn, as the source moves towards or away from an observer. The pitch of the sound is higher as the source approaches; and lower as it recedes.

Stars' temperatures are related to their spectral types. Different spectral types correspond to different surface temperatures. o-type stars are hottest, and M-type stars are coolest.

Star color corresponds to temperature. Hotter stars have bluer colors, cooler stars have redder colors. The color spectrum runs from blue to yellow to red.

The change in wavelength of light or other electromagnetic radiation emitted from a moving source. The wavelength is shorter when the source is approaching, and longer when receding from the observer.

Stars with the highest surface temperatures are classified as O type.

Shock waves can trigger the collapse of interstellar gas clouds, leading to star formation.

An HR diagram plots stars based on surface temperature (or spectral type) along the x-axis and luminosity (brightness) along the y-axis. The main sequence is a prominent diagonal band where most stars reside in the main part of their life cycle.

M-type stars are the coolest of the spectral classes.

A T Tauri star is a young, pre-main sequence star with a luminosity and temperature similar to those found in location 4 on the HR diagram.

The collapse of a molecular cloud, leading to star formation, can be triggered by external forces like supernova shock waves or nearby stars.

The proton-proton chain, a nuclear fusion process in stars, requires high temperatures to overcome the electrostatic repulsion between positively charged protons.

The CNO cycle is a nuclear fusion process that occurs in the cores of massive stars, fusing hydrogen into helium using carbon, nitrogen, and oxygen as catalysts.

The core of the Sun, where nuclear fusion occurs via the proton-proton chain, must have a temperature of at least 10 million Kelvin.

The CNO cycle is most efficient in stars more massive than the Sun, as it requires higher temperatures and densities.

The region just below the Sun's visible surface, the photosphere, is where energy is transported by convection, a process of heat transfer involving the movement of fluids.

Massive main sequence stars, with higher masses than the Sun, utilize the CNO cycle for nuclear fusion in their cores.

The primary energy source for stars on the main sequence is nuclear fusion, where hydrogen atoms fuse into helium, releasing tremendous energy.

Before nuclear fusion begins, the energy source for a forming star is gravitational potential energy. As gas collapses, it heats up.

Low-mass stars cannot become red giants because they cannot heat their cores hot enough to ignite helium fusion. They are too small to develop the necessary pressure.

A planetary nebula is the outer layers of a medium-mass star that have been ejected into space, leaving behind a white dwarf.

The Chandrasekhar limit is the maximum mass a white dwarf can have before collapsing. It's about 1.4 times the mass of the Sun.

A white dwarf doesn't generate new energy. It simply radiates away the heat it has stored from its previous life as a star.

A Type I supernova occurs when a white dwarf in a binary system accretes enough matter from its companion star to exceed the Chandrasekhar limit, leading to a catastrophic explosion.

A nova event is typically associated with a white dwarf in a binary system. As the white dwarf pulls material from its companion, it causes a sudden, bright explosion.

Neutron stars spin rapidly due to conservation of angular momentum during their formation, shrinking from immense sizes into compact objects.

While very hot, neutron stars have small surface areas and don't emit much visible light, making them difficult to locate.

At extreme density and temperature, electrons merge with protons to form neutrons and neutrinos, releasing energy. This reaction contributes to the high density of neutron stars.

Neutron stars are denser than white dwarfs, pulsars, and even a white dwarf's density is greater than a black hole's.

Pulsars, rotating neutron stars, require a rapid rotation, a strong magnetic field, and an axis of rotation different from the axis of the magnetic field.

The event horizon of a black hole marks the boundary beyond which nothing, not even light, can escape. This is the Schwarzschild radius.

The Schwarzschild radius of a black hole is the distance from its center at which the escape velocity equals the speed of light, marking the event horizon boundary.

Black holes are difficult to detect due to their lack of light emission. Finding them often involves searching for X-ray binaries where the companion object's mass exceeds 3 solar masses.