Physics 1002: Astronomy I & Physics 1007: Space Science & Astrophysics I - Solar System

Flashcards covering key vocabulary and concepts from a Solar System and Astrophysics lecture.

Astronomical Unit (AU)

A unit of measurement approximately equal to 150 million kilometers, representing the average distance from Earth to the Sun.

Light Year (ly)

The distance light travels in one year, equivalent to approximately 10 million million kilometers or 63,240 AU.

Heliopause

The boundary between the solar system and interstellar space, located at approximately 100 AU radius.

The Sun

The G2 V type star at the center of our solar system, providing heat and energy to Earth. It has a surface temperature of approximately 5,800 K.

Sunspots

Regions on the Sun's photosphere where twisted magnetic field lines penetrate the surface, varying in numbers with an 11-year cycle.

Coronal Mass Ejection (CME)

A large release of plasma and magnetic field from the solar corona that can cause disturbances in space weather and potentially disrupt satellites and power grids on Earth.

Ecliptic

The plane of Earth’s orbit around the Sun; the other planets orbit in nearly the same plane.

Axial Tilt

The tilt of a planet's equator relative to its orbit; this causes seasons.

Mare

Huge lava flows on the moon, younger than the highland terrain, indicated by different cratering densities.

Tharsis Rise

A volcanic plateau on Mars with a 5-6 km elevation.

Valles Marineris

A large canyon on Mars, 4000 km long, 600 km wide, and 8 km deep.

Galilean Moons

Jupiter's most massive moons. lo, Europa, Ganymede, and Callisto.

Titan

A moon of Saturn with methane rivers, lakes, and seas, where methane plays a role similar to water on Earth.

Terrestrial Planets

Planets with rocky surfaces, mountains, craters, and thin atmospheres, composed of heavier elements like Iron, Silicon, Magnesium, and Nickel. Mercury, Venus, Earth, and Mars.

Jovian Planets

Gas or ice giants composed mainly of molecular hydrogen and helium with traces of methane, ammonia, and water, possessing rocky, metallic cores and numerous satellites. Includes Jupiter, Saturn, Uranus, and Neptune.

Dwarf Planet

A celestial body that orbits the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and has cleared the neighbourhood around its orbit.

Asteroids

Irregularly shaped rocky objects ranging from meters to hundreds of kilometers in size, often cratered, resulting from collisions and impacts.

Meteoroids

Small rocky or metallic body in outer space. Smaller than asteroids, ranging from a few cms to a few meters.

Comets

Irregularly shaped objects composed of rocks and ice, generally less than 10-20 km in diameter, which become active near the sun, emitting gases and forming tails.

Radiation

Solar (wind, flares, CMEs) from the sun and cosmic radiation from everywhere else, consisting of particle radiation dominated by protons

Retrograde Motion

The apparent backward motion of a planet as seen from Earth.

Geocentric Ptolemaic System

A mathematical model of the universe where Earth is at the center, with planets moving in epicycles along deferents, used to predict planetary positions for over 1000 years.

Johannes Kepler

A student of Tycho Brahe, developed three laws on heliocentric planetary motion.

Galileo Galilei

Observed with a telescope and saw phases on Venus AND moons orbiting Jupiter. (Earth not the centre of everything!)

Isaac Newton

Developed gravitational theory that explained the movement of the planets.

Kepler's First Law

The orbit of a planet about the Sun is an ellipse with the Sun at one focus.

Kepler's Second Law

A line joining a planet and the Sun sweeps out equal areas in equal times.

Kepler's Third Law

The square of the orbital period (P) of the planet is proportional to the cube of the semi-major axis (a) of the orbit.

Perihelion

Closest distance to the sun

Aphelion

Furthest distance from the sun.

Greatest Elongation

when the sun- planet-Earth angle is a right angle and only applies to inferior planets.

Inferior Planets

orbits are smaller than that of the Earth

Elongation

The angle between sun and planet as viewed from Earth.

Opposition

planet is in opposite part of the sky to the sun (therefore is visible at night).

Conjunction

in same part of the sky as the sun

Synodic Period

is the time between two successive identical configurations as seen from Earth (e.g. oppositions of Mars)

Sidereal Period

is the time a planet takes to complete one orbit with respect to the stars or any fixed frame of reference

Inclination

the angle from the ecliptic plane to the orbital plane in the space lying on the north side of the ecliptic. Inclinations between 90 and 180 degrees indicate a retrograde orbit.