Astronomy: Kepler's and Newton's Laws

• Earth orbits the Sun.
• The Sun is a typical star within the Milky Way Galaxy.
• The Milky Way is one of 100 billion galaxies.
• The universe is expanding, as described by Hubble’s Law.
• Andromeda, the closest galaxy to the Milky Way, is moving towards us.
• Looking at distant objects is looking back in time because light travels at a finite speed.
• The sky is divided into 88 constellations.
• Earth’s rotation causes stars to rise and set.
• Seasons are caused by Earth's axial tilt.
• The phases of the Moon are a result of its orbit around Earth.
• Planets appear to wander across the sky.
• Ancient Greeks developed early models of the universe.

Kepler’s Laws

• Planetary orbits are elliptical.
• A planet sweeps out equal area in equal time.
• P^2 = a^3 : Period squared equals semi-major axis cubed.
• The scientific method is important for advancing astronomy.
• Motion is described by velocity, acceleration, and momentum.

Newton’s Laws

• Objects stay in motion unless acted on by a force.
• F = ma: Force equals mass times acceleration.
• Every action has an equal and opposite reaction.
• Gravity: F = GM1M2/r^2
• Light behaves as both a wave and a particle (photon).
• Wavelength and frequency determine light's energy.
• Spectral lines are created by electron energy levels.
• The Doppler effect causes light to shift due to motion.
• Telescopes collect and focus light.
• Two types of telescopes: refracting (lenses) and reflecting (mirrors).
• The atmosphere limits which wavelengths reach the ground.
• The solar system has 8 planets: terrestrial (rocky) and jovian (gas giants).
• The solar system also contains moons, comets, asteroids, and dwarf planets.
• Spacecraft study planets using flybys, orbiters, landers, and sample returns.
• The solar system formed from a collapsing nebula about 4.6 billion years ago.
• The nebula heated up and spun faster as it collapsed.
• Internal structure of terrestrial planets can be inferred from geology.
• Surface temperature depends on the cooling rate of the planet.
• A planet's atmosphere affects its climate and weather.
• Greenhouse gases trap heat within a planet's atmosphere.
• Jovian planets are gas giants and lack solid surfaces.
• Jupiter and Saturn have compositions similar to the Sun.
• All jovian planets have ring systems.
• Some moons may have subsurface oceans, like Europa and Enceladus.
• Asteroids are rocky, while comets are icy.
• Meteors enter Earth's atmosphere; meteorites reach the ground.
• Impact events are expected; efforts exist to detect and prevent them.
• Exoplanets are mainly detected through transits and Doppler shifts.
• These methods reveal an exoplanet's orbit, mass, radius, density, and composition.

Final Notes

• Focus on conceptual understanding.
• Know key definitions, laws, and principles.
• Apply concepts to varying scenarios.

Commonly Missed Homework Questions

• Potassium-40 decreases by half every 1.25 billion years.
• After two half-lives (2.5 billion years), only 25% remains.
• After 1.875 billion years (1.5 half-lives), 35% remains using the formula: 0.5^(1.5) = 0.35.

Terrestrial Planets (Continued)

• Internal structures determined through seismic activity, gravity measurements, and surface geology.
• Smaller planets cool faster due to surface area-to-volume ratio.
• Volcanic activity and tectonics indicate internal heat.
• The greenhouse effect describes how gases trap heat, influencing climate.
• Weather patterns differ by planet, resulting from varied atmosphere composition and pressure.

Jovian Planets (Continued)

• Jupiter and Saturn are mainly hydrogen and helium.
• Uranus and Neptune have more hydrogen compounds.
• Some moons have internal heating due to tidal forces, such as Io’s volcanoes.
• Icy moons, like Europa and Enceladus, might have subsurface oceans.
• All gas giants have rings made of ice and rock debris.

Small Bodies (Continued)

• Asteroids are rocky and found in the asteroid belt.
• Comets are icy and originate from the Kuiper Belt & Oort Cloud.

Dwarf Planets

• Pluto, Eris, Haumea, Makemake, and Ceres.

Space Rocks

• Meteoroid: A rock in space.
• Meteor: Burns in Earth's atmosphere.
• Meteorite: Survives impact on Earth's surface.
• Large impacts have shaped planetary surfaces.
• Space agencies work on detecting and deflecting objects.

Exoplanets (Continued)

• Transit Method: Planet blocks starlight, leading to brightness dips.
• Radial Velocity Method: Star wobbles due to a planet’s gravity.
• Direct Imaging: Possible but rare, using advanced telescopes.
• Can determine an exoplanet's orbital period, distance, mass, radius, density, and atmosphere.
• Some exoplanets may be in the habitable zone, where liquid water can exist.

Final Study Tips

• Review key formulas and applications.
• Understand conceptual differences between terrestrial and jovian planets.
• Explain observational techniques used in astronomy.
• Practice interpreting data from graphs and equations related to planetary motion and light.