Universe, Solar System, and Celestial Mechanics Flashcards

Flashcards for reviewing lecture notes on the universe, solar system, and celestial mechanics.

Steady State Theory

States that the universe is always in a constant state, everywhere and at all times. Largely refuted by the observation that the universe is expanding.

Oscillation Theory

Proposes that all matter in the universe moves away from each other, stops, contracts, and repeats periodically, suggesting a finite, rather than infinite, universe.

Big Bang Theory

Posits that all matter and energy in the universe were once concentrated into a giant ball that exploded, causing the universe to expand. Evidence includes cosmic background radiation.

Nebula Theory

Proposed by Immanuel Kant and Pierre de Laplace in 1796, suggests the solar system formed from a giant, rotating nebula that contracted under gravity, forming the Sun and planets.

Tidal and Collision Theories

Suggests that the passage or collision of a star with the Sun drew gas from the Sun, which then formed into planets.

Turbulence Theory

Proposed by F.C. van Weizsacker in 1945, suggests the Sun formed from a nebula surrounded by a rotating gas cloud, leading to turbulence and the formation of protoplanets.

Protoplanet Theory

Proposed by G.P. Kuiper in 1950, suggests the solar system formed from a rotating cloud of gas and dust, with the Sun forming at the center and protoplanets forming in the surrounding disk.

Differentiation

The process where heavier elements sink towards the core of a planet, while lighter elements rise to the surface, resulting in layered structure within the planet.

Core (of the Sun)

The innermost layer of the Sun, where hydrogen fusion occurs, generating vast amounts of energy.

Radiative Zone

A region in the Sun where energy is transported primarily through radiation. Energy is emitted as photons, which are absorbed and re-emitted by other particles.

Convective Zone

A region in the Sun where energy is transported primarily through convection due to lower temperature and pressure.

Photosphere

The visible surface of the Sun, characterized by granular appearance due to convection cells. It is relatively thin and emits photons into space.

Limb Darkening

The phenomenon where the edge of the Sun appears darker because we are observing the upper, cooler layers of the solar atmosphere.

Granulation

Convection in the photosphere creates these, which are small, short-lived features typically around 1000 km in size.

Supergranulation

Larger convective cells than granulation, spanning about 35,000 km and lasting up to a day, best observed in Dopplergrams.

Chromosphere

A layer above the photosphere with a higher temperature, characterized by spicules, which are jets of gas rising from the photosphere.

Corona

The outermost layer of the Sun's atmosphere, extending millions of kilometers into space. It is extremely hot but has very low density, expanding into solar wind.

Sunspots

Dark spots on the photosphere, cooler than the surrounding areas due to strong magnetic activity which inhibits convection.

Coronal Loops

Features that follow magnetic field lines in the corona, originating from the photosphere with positive and negative polarities.

Filaments

Dark, cooler features made of chromospheric material, supported by magnetic fields in the corona, seen against the solar disk.

Prominences

Filaments viewed from the edge of the solar disk, appearing bright against the dark background of space.

Plage

Bright areas associated with sunspots.

Flares

Sudden releases of electromagnetic radiation from the Sun, spanning all wavelengths and consisting largely of ionized material.

Coronal Mass Ejections (CMEs)

Large ejections of plasma and magnetic field from the Sun's corona, which can reach Earth and cause auroras.

Aurora (Borealis and Australis)

The luminous atmospheric phenomenon seen in the sky near the polar regions, resulting from the collision of charged particles with atoms in the upper atmosphere.

Inner Planets

Planets with orbits inside the asteroid belt (Mercury, Venus, Earth, Mars).

Outer Planets

Planets with orbits outside the asteroid belt (Jupiter, Saturn, Uranus, Neptune).

Inferior Planets

Planets closer to the Sun than Earth (Mercury, Venus).

Superior Planets

Planets farther from the Sun than Earth (Mars, Jupiter, Saturn, Uranus, Neptune).

Terrestrial Planets

Rocky planets similar in composition to Earth (Mercury, Venus, Earth, Mars).

Jovian Planets

Gas giants, similar in composition to Jupiter (Jupiter, Saturn, Uranus, Neptune).

Mercury

Has a very thin atmosphere, extreme temperature variations, and is heavily cratered.

Venus

Known for its thick CO2 atmosphere, extreme greenhouse effect, and retrograde rotation.

Astronomical Unit (AU)

The average distance between the Earth and the Sun.

Daily Phenomena (e.g., day/night, sunrise/sunset)

Phenomena caused by the Earth's rotation.

Sidereal Day

The time it takes for a star to return to the same meridian, shorter than a solar day.

Solar Day

The time it takes for the Sun to return to the same meridian, defined as 24 hours.

Seasons

Phenomenon caused by Earth's revolution around the Sun.

Axial Tilt (23.5 degrees)

The angular tilt of Earth's axis relative to its orbital plane.

William Herschel

Discovered the planet Uranus in 1781.

Giant-impact hypothesis

The theory that the Moon formed from debris ejected during a collision between Earth and a Mars-sized object.

Asteroids

Small, rocky or metallic objects orbiting the Sun, mostly found in the asteroid belt between Mars and Jupiter.

Comets

Icy bodies that release gas and dust when they approach the Sun.

Meteoroid

Small rocky or metallic body traveling through space.

Meteor

The luminous phenomenon seen when a meteoroid burns up in Earth's atmosphere.

Meteorite

A meteoroid that survives its passage through the atmosphere and impacts the Earth's surface.

Newton’s Law of Universal Gravitation

A physical law describing the gravitational attraction or repulsion between objects.

Escape Velocity

The minimum speed required for an object to escape the gravitational influence of a massive body.

Orbit

The path of an object in orbit around another object.

Kepler's First Law

States that planets move in elliptical orbits with the Sun at one focus.

Kepler's Second Law

States that a line connecting a planet to the Sun sweeps out equal areas during equal intervals of time.

Kepler's Third Law

States that the square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit.

Radio Waves

Electromagnetic waves with wavelengths between a few millimeters and 20 meters.

Infrared Waves

Electromagnetic waves with wavelengths from 7500 Å to about 1 mm.

Optical Waves

Electromagnetic waves with wavelengths between 3800 Å and 7500 Å.

Ultraviolet Waves

Electromagnetic waves with wavelengths less than 3500 Å.

Black Body

Objects that perfectly absorb and emit all electromagnetic radiation.

Wien's Law

The law stating the inverse relationship between temperature and wavelength of maximum emission for a black body.

Flux

The total radiant energy emitted by an object per unit area.

Luminosity

The total amount of energy emitted by an object per unit time.

Apparent Magnitude

A measure of the brightness of an object as seen from Earth.

Absolute Magnitude

A measure of the intrinsic brightness of an object, defined as the apparent magnitude it would have at a distance of 10 parsecs.

Color Index

The difference between photographic and visual magnitudes, indicating the color and temperature of a star.

Hertzsprung-Russell Diagram (H-R Diagram)

A graph plotting stellar luminosity against temperature, showing the distribution of stars based on their properties.

Main Sequence

A band on the H-R diagram where most stars are located, representing stars fusing hydrogen in their cores.

Giant Star

Large, luminous stars that have evolved off the main sequence.

Supergiant Star

Extremely luminous stars that are nearing the end of their lives.

White Dwarf

Small, dense, and faint stars that represent the final stage in the evolution of low-mass stars.

Spectrum

The separation of light into its component colors.

Absorption Lines

Dark lines in a spectrum caused by the absorption of specific wavelengths of light by atoms or molecules.

Emission Lines

Bright lines in a spectrum caused by the emission of specific wavelengths of light by excited atoms or molecules.

Kirchhoff's Laws

A set of rules describing the conditions under which continuous, emission, and absorption spectra are formed.

Balmer Series

A series of spectral lines in the visible region of the electromagnetic spectrum created by hydrogen atoms.

Stellar Spectral Classification

A classification system for stars based on their spectral characteristics, which are indicative of their temperature and composition.

Doppler Effect

The change in frequency or wavelength of a wave due to the relative motion between the source and the observer.

Doppler Broadening

The broadening of spectral lines due to the motion of atoms in a star.

Parsec

A unit of distance equal to 3.26 light-years, defined as the distance at which an object has a parallax of one arcsecond.

Parallax

The apparent shift in the position of a nearby star relative to distant stars due to Earth's motion around the Sun.

Trigonometric Parallax

Using trigonometry and the baseline of half of the Earth's orbit around the Sun to measure the distance to nearby stars.

Angular Size

The angle subtended by an object at a given distance, measured in degrees, arcminutes, or arcseconds.

Angular Separation

The angular separation between two objects as seen by an observer, measured in degrees, arcminutes, or arcseconds.

Doppler shift

The change in the observed wavelength of light due to the motion of the source or observer.