Astrology Final

Orders of Magnitude

Comparing quantities by powers of 10; focuses on scale, not precision.

Scientific Notation

Writing numbers as A × 10ⁿ with 1 ≤ A < 10.

Dimensional Analysis

Checking equations by making sure units match.

Celestial Sphere

Imaginary sphere used to map object positions in the sky.

Celestial Pole

Projection of Earth's rotation axis onto the sky.

Celestial Equator

Projection of Earth's equator onto the sky.

Horizon

Boundary between Earth and sky.

Zenith

Point directly overhead.

Meridian

Line dividing eastern and western sky; objects highest when crossing it.

Ecliptic

Sun's apparent yearly path; plane of Solar System.

Circumpolar Stars

Stars that never set; DEC ≥ 90° − latitude.

Latitude

North-south Earth coordinate.

Longitude

East-west Earth coordinate.

Right Ascension (RA)

Celestial longitude, measured in hours.

Declination (DEC)

Celestial latitude, −90° to +90°.

Cause of Seasons

Earth's axial tilt (23.5°), not distance from the Sun.

Why Polaris Is Special

Located near North Celestial Pole; appears stationary.

Visibility of Objects

Depends on latitude and object declination.

Newton's First Law

Objects resist changes in motion (inertia).

Newton's Second Law

F = ma.

Newton's Third Law

Every action has an equal and opposite reaction.

Universal Law of Gravitation

F = GmM / r².

Inverse-Square Law

Force/flux decreases as 1/r².

Weight

Force from gravity acting on a surface.

Weightlessness

Freefall; gravity still present.

Orbit

Continuous freefall around a mass.

Emission

Light produced by excited atoms.

Absorption

Atoms remove specific wavelengths.

Scattering

Light redirected (blue sky).

Reflection

Light bouncing off surfaces.

Transmission

Light passing through material.

Why Objects Have Color

Colors reflected/emitted, not absorbed.

Wavelength

Distance between wave peaks; sets color.

Frequency

Number of waves per second.

Photon

Particle of light.

Energy-Frequency Relation

E = hν.

Electromagnetic Spectrum Order

Radio → IR → Visible → UV → X-ray → Gamma.

Flux

Observed brightness.

Luminosity

Intrinsic power output.

Flux-Luminosity Relation

Flux ∝ L / d².

Angular Size

Apparent size of an object.

Spectrum

Light spread by wavelength.

Blackbody

Ideal thermal emitter; hotter = bluer & brighter.

Continuous Spectrum

Emitted by hot, dense objects.

Emission Spectrum

Hot, thin gas.

Absorption Spectrum

Continuous source + cooler gas.

Quantized Energy Levels

Electrons occupy fixed energies.

Ionization

Removal of an electron (H → H⁺).

Why Elements Have Unique Spectra

Different atomic energy levels.

Attenuation

Dimming by dust/gas.

Why Sky Is Blue

Rayleigh scattering favors blue light.

Why Sunsets Are Red

Blue scattered away over long paths.

Why Use Telescopes

Collect light, improve resolution, observe all wavelengths.

Why Bigger Telescopes Are Better

More light + better angular resolution.

Refracting Telescope

Uses lenses.

Reflecting Telescope

Uses mirrors (dominant in research).

Angular Resolution

Ability to separate close objects.

Light Pollution

Artificial light interfering with observations.

Atmospheric Effects

Absorption, distortion.

Adaptive Optics

Corrects atmospheric turbulence.

Photometry

Measuring brightness.

Image

Spatial distribution of light.

True Color Image

Uses visible wavelengths.

False Color Image

Assigns visible colors to non-visible light.

Spectroscopy

Splitting light to study composition and motion.

Spectral Resolving Power (R)

R = λ / Δλ.

Space Telescopes (Pros)

No atmosphere.

Space Telescopes (Cons)

Expensive, difficult to repair.

What the Sun Is

G2V main-sequence star.

Solar Structure

Core → Radiation Zone → Convection Zone → Photosphere → Chromosphere → Corona.

What Makes the Sun Shine

Nuclear fusion.

Proton-Proton Chain

Hydrogen → helium fusion.

Hydrostatic Equilibrium

Gravity balanced by pressure.

Sunspots

Cooler, magnetic regions.

Planet Definition

Orbits Sun, round, clears orbit.

Atmosphere Retention

Higher mass, colder, heavier gases.

Kepler's First Law

Orbits are elliptical.

Kepler's Second Law

Equal areas in equal times.

Kepler's Third Law

P² ∝ a³.

Astronomical Unit (AU)

Earth-Sun distance.

Most Important Stellar Property

Mass.

H-R Diagram

Luminosity vs temperature.

Main Sequence

Hydrogen fusion phase.

Magnitude System

Lower magnitude = brighter.

Apparent Magnitude

Observed brightness.

Absolute Magnitude

Brightness at 10 pc.

Spectral Types

OBAFGKM (hot → cool).

Luminosity-Radius-Temperature Relation

L ∝ R²T⁴.

Parallax

Apparent shift due to Earth's orbit.

Parsec

Distance at 1 arcsec parallax.

Low-Mass Star Life Cycle

MS → red giant → planetary nebula → white dwarf.

Mirror Principle

Core contracts → envelope expands.

Helium Flash

Sudden helium fusion in low-mass stars.

Triple-Alpha Process

Helium → carbon.

High-Mass Star Life Cycle

MS → supergiant → core-collapse supernova.

CNO Cycle

Fusion in massive stars.

Iron Problem

Fusion past iron consumes energy.

Supernova Remnant

Expanding debris cloud.

Stellar Nucleosynthesis

Element creation in stars.

Binary Stars

Two stars orbiting each other.