Astronomy and Cosmology Practice Flashcards

Vocabulary flashcards covering fundamental concepts of astronomy, cosmology, the Big Bang timeline, and stellar characteristics based on lecture notes.

Astronomy

The study of celestial objects & processes.

Cosmology

The study of the history and structure of the entire universe.

Galaxy

A system of millions of stars held together by gas, dust, and gravitational force.

Logarithmic thinking

A way of understanding numbers by focusing on how much larger or smaller they are in powers of ten, rather than their exact values.

Lightyears

A measurement of length/distance that light will travel in a year; where $1\text{ year} = 9.46000000000000000$.

Continuous spectrum

A full emission spectra or series of wavelengths emitted by stars.

Absorption spectrum

Produced when light from a star passes through cooler gases in its outer atmosphere and specific wavelengths are absorbed, appearing as dark lines.

Energy-Frequency-Wavelength Relationship

Energy is directly proportional to frequency ($E \text{ Proportional } f$) and inversely proportional to wavelengths ($E \text{ Proportional } \frac{1}{\text{wavelength}}$).

Doppler effect

The change in frequency of a wave in relation to an observer who is moving relative to the wave source.

Redshift

Occurs when something is moving away from us at a lower frequency; evidence for the expansion of the universe.

Blueshift

Occurs when an object is moving toward us with a higher frequency; exhibited by the aerometer galaxy.

Singularity

An infinitely hot and dense point from which space-time and matter originated $13.8$ billion years ago.

Recombination

Occurred at $380,000 \text{ years}$ when the universe cooled to $3000 \text{ degrees}$, allowing atomic nuclei to form and photons to decouple, creating CMB radiation.

Steady State Theory

An incorrect theory suggesting the universe is in a state of eternal expansion with new matter created to fill gaps so the universe remains uniform.

Hubble's Constant ($H_O$)

The constant representing the gradient where recession velocity is directly proportional to distance ($v = H_O \times d$).

Cosmic Microwave Background (CMB) Radiation

The afterglow from the big bang that serves as a snapshot of the hot, dense early universe and evidence of cosmic structure origin.

Light Element Abundance

The specific $3:1$ mass ratio of primordial Hydrogen to Helium that matches theoretical nuclear calculations.

Luminosity

The total amount of energy a star releases each second across all wavelengths; the actual brightness of a star.

Absolute magnitude

A measure of a star's actual brightness if it were observed at a distance of $10 \text{ parsecs}$ ($32.6 \text{ light years}$) from Earth.

Spectral Class

A system (O, B, A, F, G, K, M) that indicates a star's temperature, colour, and present elements.

Nuclear Fusion

The power source of all main sequence stars where two light nuclei are forced together to form a heavier nucleus, requiring temperatures of $15 \text{ million C}$.

Hertzsprung Russell diagram

A diagram showing the relationship between the brightness (magnitude) and the temperature of stars.

What is a key event during Recombination?

The formation of neutral atoms from electrons and nuclei after the universe cooled, allowing photons to decouple.

What is Absolute Magnitude?

A measure of a star's actual brightness if observed from a standard distance of $10 \\text{ parsecs}$ ($32.6 \\text{ light years}$) from Earth, allowing comparison of true brightness among stars.

What are nebulae?

Clouds of gas and dust in space where stars are formed.

What triggers stellar ignition?

Stellar ignition occurs when hydrogen nuclei begin to fuse with helium, initiating nuclear fusion.

What conditions are necessary for nuclear fusion?

Nuclear fusion requires high temperature and high density.

What is gravitational force in stars?

The inward force attempting to collapse a star's mass.

What is radiation pressure?

The outward force generated by energy produced during nuclear fusion.

What is the equilibrium of main sequence stars?

Equilibrium in main sequence stars occurs when gravitational force equals radiation pressure.

What is the lifecycle of a low-mass main sequence star?

Nebula → protostar → low-mass main sequence star → white dwarf → black dwarf (theoretical).

What is the lifecycle of a medium-mass main sequence star?

Nebula → protostar → medium-mass main sequence star → red giant → planetary nebula → white dwarf → black dwarf (theoretical).

What is the lifecycle of a high-mass main sequence star?

Nebula → protostar → high-mass main sequence star → red supergiant → supernova → neutron star or black hole.

What happens in a red giant phase?

A red giant forms when nuclear fusion reactions in the core slow down, causing the core to contract and the outer layers to expand and cool.

What is the significance of equilibrium in a main sequence star?

Equilibrium signifies a stable state where gravitational and radiation pressures balance, allowing the star to maintain its structure.

What role does pressure play in a star's lifecycle?

Pressure increases as the core contracts, allowing fusion reactions to continue, leading to transformations in the star's evolution.

Lifecycle of stars based on initial mass

Stars evolve differently depending on their mass; low-mass stars become red giants and then white dwarfs, while high-mass stars grow into red supergiants, leading to supernovae or black holes.