astronomy eoc

Aristarchus

First person to propose a heliocentric model

Galileo Galilei

Used a telescope to observe phases of Venus and 4 largest moons of Jupiter; supported heliocentrism

Johannes Kepler

Created the 3 Laws of Planetary Motion using Tycho Brahe's data

Claudius Ptolemy

Created complex geocentric model using epicycles (80+ circles)

Tycho Brahe

Gathered 38 years of naked-eye observations and proposed a hybrid model

Eratosthenes

Measured Earth's circumference using shadows and geometry

Nicolaus Copernicus

Proposed heliocentric model again, motivated by simplicity

Gravity

More mass = stronger gravity; closer distance = stronger gravity

Exoplanets

Thousands of exoplanets have been discovered

Radial Velocity

Detects star wobble using Doppler shift

Transit Method

Detects dip in brightness

Gravitational Microlensing

Gravity bends light from background star

Direct Imaging

Blocks star light to see planet

Astrometry

Measures tiny star movement

Electromagnetic Spectrum

Longest Wavelength → Shortest Wavelength: Radio → Infrared → Visible → Ultraviolet → X-rays → Gamma Rays

Emission Line Spectrum

Bright lines on dark background; hot gas

Continuous Spectrum

Smooth rainbow; solid/dense gas

Absorption Line Spectrum

Dark lines on rainbow; cool gas between source and observer

H-R Diagram

Vertical axis = Luminosity; Horizontal axis = Temperature

Main Sequence

Long strip through center; most stars are here

Stellar Life Cycles

Lowest mass stars live about 1 trillion years

Nuclear Fusion

Hydrogen → Helium

General Relativity

Mass bends and warps spacetime

Gravitational Redshift

Light loses energy escaping gravity

Black Hole

Gravity so strong light cannot escape

Galaxy

Billions of stars, gas, dust bound by gravity

Supercluster

Groups/clusters of galaxies