23-1 Flashcards
(15 cards)
what is the sun? how is it held?
center of a rotating system of planets and moons, held by its gravity
How do planets orbit the Sun, and how does distance affect their motion?
planets orbit in the same direction in elliptical paths. the closer it is to the sun the shorter the orbit
what are the two groups planets fall into?
terrestrial (inner) planets, and Jovian (outer) planets
what are terrestrial planets? where is it, what planets, how dense, what are cores like, etc
Mercury, Venus, Earth, Mars; closest to sun, small, dense, solid, rocky, metallic surface, small amounts of gases/ices, where heat vaporized light elements, leaving rocky planets with heavy iron cores
what are Jovian planets? size, what planets, cores, density, rotation?
Jupiter, Saturn, Uranus, Neptune; keeps light gases and forms large, gas giants, less dense; rocky, metallic, small cores compared to overall size of planets, colder, rotates on axis more quickly than inner planets
what are the 3 parts of the interior of planets?
- Gases: hydrogen and helium, melting points near absolute zero
- Rocks: silicate minerals and metallic iron; melting points above 700
- Ices: ammonia, methane, carbon dioxide, water; melting points of around 0
What determines the thickness and composition of a planet’s atmosphere? What type of atmosphere do terrestrial and jovian planets have?
Gravity determines whether it can hold onto an atmospehre. terrestrial planets have thin atmosphere, jovian planets have thick atmosphere of hydrogen, helium, methane, and ammonia.
What must rockets do to escape a planet’s gravity and stay in orbit? what would happen if too slow/fast?
rockets need more upward thrust than the planet’s gravity to lift off. to stay in orbit they must reach oribtal velocity - too slow, they fall back to Earth. too fast, they escape into space
What is escape velocity, and how does it relate to a planet’s atmosphere?
Escape velocity is the speed needed to break free from a planet’s gravity. Gas molecules can escape a planet’s atmosphere if they reach this speed.
How do temperature and gravity affect a planet’s ability to keep an atmosphere?
Warmer inner planets lose gases faster, so they have thin atmospheres. Larger, cold inner planets can hold onto heavier gases so they have strong gravity and slow-moving gas molecules, allowing them to keep dense atmospheres.
what is nebula?
region of widely spread dust and gases, similar to fog, consists of 90% hydrogen, 9% helium, 1% heavier elements
what is the nebular theory?
a theory that after the Big Bang, matter spread everywhere in universe, causing solar systems to form
what is solar nebula? how is it formed?
forms as gravity pulls gas and dust inward, increasing density and rotation. flattens into a disk, and the core heats up until nuclear fusion starts so a star is born
what are planetesimals? how are they formed?
asteroid-like and comet-like bodies, formed when outer gas and dust particles combine when not all gas and dust was drawn into core
what is accretion?
when matter collides and clump together becoming larger forming planets and moons
