Star Evolution, Black Holes, and Cosmology: Key Concepts for Astronomy

What is the surface temperature of one-solar-mass protostars?

It stays roughly constant.

What happens to the luminosity of one-solar-mass protostars as their radius decreases?

Luminosity decreases.

What is the evolutionary track of one-solar-mass protostars on the H-R diagram?

It moves downward.

What occurs to the internal temperature of a protostar as it evolves?

It increases and ionizes, becoming less opaque.

How is energy converted in the present-day Sun?

By radiation in the interior and convection in the opaque outer layers.

What is hydrostatic equilibrium in a main-sequence star?

A balance between the inward force of gravity and the outward pressure produced by hydrogen fusion.

What is a zero-age main-sequence star?

A freshly formed main-sequence star.

What happens to the core of a star over time during its main-sequence lifetime?

The total number of atomic nuclei decreases as hydrogen is converted to helium.

What characterizes red dwarfs?

They are small in size and red in color due to low surface temperature.

What is the relationship between a star's mass and its main-sequence lifetime?

M-s lifetime depends directly on mass; massive stars have shorter lifetimes.

What elements are produced during carbon fusion in stars?

Oxygen, neon, sodium, and magnesium.

What happens after neon fusion in a star?

The core contracts and oxygen fusion begins, producing silicon.

What is the principle product of silicon fusion?

Iron and nickel.

What is the Schwarzschild radius?

The distance from the center of a nonrotating black hole to its event horizon.

What does the no-hair theorem state about black holes?

Black holes are completely described by their mass, electric charge, and angular momentum.

What is Hawking radiation?

Radiation that allows black holes to lose mass and evaporate.

What is dark matter?

Unseen material that is the predominant constituent of our galaxy outside the sun's orbit.

What causes spiral arms in galaxies?

Density waves that sweep around the galaxy.

What is the Hubble Law?

It relates the redshifts of remote galaxies to their distances from Earth.

What does a higher redshift indicate about a galaxy?

The greater its distance from Earth.

What is the formula for redshift (z)?

z = (lambda - lambda(initial)) / lambda(initial).

What is the significance of E=mc^2?

It shows the relationship between mass and energy.

What is the proton-proton chain?

A process where hydrogen nuclei are fused into helium, releasing energy.

What is the Stefan-Boltzmann law?

F = O T^4, relating flux and surface area of a star.

What do Hertzsprung-Russell diagrams reveal?

Different kinds of stars based on their surface temperature and luminosity.

What is the relationship between a star's luminosity and its radius?

For a given luminosity, the greater the surface temperature, the smaller the radius.

What is a white dwarf?

The smallest type of star with very high surface temperature but low luminosity.

What is the role of neutrinos in stellar processes?

They are released when protons change into neutrons.

What is neutrino oscillation?

One type of neutrino spontaneously turns into another type.

What happens to the core of a high-mass star at the end of its life?

It undergoes core-collapse leading to a supernova explosion.

What is photodisintegration?

The process where gamma-ray photons break iron nuclei into smaller helium nuclei.

What is the significance of the core-collapse supernova?

It ejects a large amount of material into the interstellar medium.

What is the effect of mass on the evolution of stars?

Higher mass stars evolve more rapidly and have shorter lifetimes.

What is the main product of oxygen fusion in massive stars?

Silicon.

What happens to the core of a star when enough iron builds up?

It leads to a cataclysmic core collapse.

What is the role of degenerate electrons in a collapsing star?

They briefly hold up pressure but cannot support high mass.

What is the relationship between temperature and pressure in a star's core?

Contraction increases core density, temperature, and pressure.

What is the significance of the Hubble constant?

It relates the recessional velocity of galaxies to their distance.

What is the fate of a star with a mass greater than 8 M?

It evolves into a supergiant and undergoes complex fusion processes.

What is the primary process that powers the Sun?

Thermonuclear fusion.

What is the role of convection in stars?

It circulates gases between hot and cool regions.

What is the main characteristic of flocculent spiral galaxies?

Their spiral arms are broad, fuzzy, chaotic, and poorly defined.

What is microlensing?

A phenomenon where gravity bends light, making stars appear to brighten.

What are WIMPs?

Weakly interacting massive particles that may compose dark matter.

What is the significance of the galactic center observations?

They reveal the presence of a supermassive black hole.

What is the relationship between the distance of galaxies and their redshift?

More distant galaxies have greater redshifts and are receding more rapidly.

What happens to a star's hydrogen during its main-sequence phase?

It is consumed and converted to helium.

What is the role of energy transport in stars?

It moves energy to the surface through convection and radioactive diffusion.

What is the result of the gravitational field of a black hole?

It distorts the image of other stars.

What happens to the core of a star during a supernova?

It becomes very dense and releases a flood of neutrinos.

What is the significance of the core's stiffness during a supernova?

It causes the inner core to bounce back and send a powerful wave outward.

What is the relationship between stellar mass and the formation of elements?

Reactions producing heavier elements than iron require significant energy input.

What is the primary fusion process in stars hotter than the Sun?

The CNO cycle.

What is the effect of stellar evolution on the interstellar medium?

Stars eject material that contributes to the formation of future stars.

What is the main sequence band in a luminosity diagram?

It is a band that runs from the upper left to the lower right, where most stars are found.

How do main sequence stars generate energy?

Through the conversion of hydrogen to helium in their cores.

What are giants in terms of stellar classification?

Luminous, cool, and huge stars.

What are red giants?

Cooler members of the giant star category.

What are supergiants?

Very luminous stars that make up about 1% of stars in the sky.

What are white dwarfs?

Stars that have exhausted their nuclear fuel and are in a final stage of evolution.

What are brown dwarfs?

Objects that never became stars due to insufficient mass.

Why is dark matter considered mysterious?

Because its true nature and composition remain unknown despite its significant presence.

What is the dark-matter problem?

The challenge of determining what form the invisible matter takes.

What is gravitational lensing?

The distortion of background images caused by a powerful source of gravity.

What is an Einstein Ring?

A perfect ring-like image formed by gravitational lensing.

What does the overall arrangement of visible galaxies indicate?

It traces the location of dark matter.

What are exotic dark matter candidates?

Hypothesized new forms of matter that are not made of protons and neutrons.

Where does dark matter lie in relation to galaxies?

Within and immediately surrounding galaxies, not in the vast spaces between them.

What is required for gravitational lensing to work?

The alignment of the lensing object and the background source must be correct.

What is the significance of dark matter in the universe?

It accounts for more mass than is visible and is crucial for the stability of galaxies.

What is the implication of not finding the edge of galaxies?

It suggests that a considerable amount of dark matter extends well beyond the visible portion of the disk.