Key Definitions of Phenomena
- Fast Phenomena: Speed is greater than 10% of the speed of light.
- Slow Phenomena: Speed is less than 10% of the speed of light.
- Large Phenomena: Size is greater than a nanometer ($10^{-9}$ m).
- Small Phenomena: Size is less than a nanometer.
Examples:
- Large Objects: Viruses, solar systems, galaxies.
- Small Objects: Electrons, atoms, protons.
Celestial Mechanics
Discovery of Neptune
- Year: 1846.
- Discoverers: Johann Gottfried Galle and Heinrich Louis d'Arrest.
- Method: Mathematical predictions by Urbain Leverrier and John Couch Adams.
- Significance: Neptune was theorized due to irregularities in Uranus's orbit.
- Pre-discovery observations: Seen by Galileo in 1612 and James Challis in 1845.
Discovery of Uranus
- Year: 1781.
- Discoverer: William Herschel.
- Method: Improvements in observational techniques and mathematical theories for orbit determination (Carl Friedrich Gauss, Wilhelm Olbers).
Newtonian Gravity
- Foundational Idea: Isaac Newton's law states $F = \frac{GM1M2}{r^2}$, where:
- $F$ = gravitational force
- $G$ = gravitational constant
- $M1$, $M2$ = masses of the two bodies
- $r$ = distance between the centers of the two masses.
- Significance: Basis for celestial mechanics in 18th and 19th centuries.
Speed of Light
- Ole Roemer: Demonstrated that the speed of light is finite based on the observation of Jupiter's moons.
Early Star Catalogues
- Uranometria (1603): Created by Johann Bayer, introduced star naming conventions (Greek letters).
- Historia Coelestis Britannica (1712): Created by John Flamsteed with Flamsteed numbers.
- Messier Catalogue (1781): Compiled by Charles Messier containing 103 entries.
- General Catalogue (1864): Compiled by John Herschel, included over 5000 non-stellar objects.
Telescope Innovations
- Galileo Galilei (1609): First to use telescope for stellar observations, discovered moons of Jupiter, sunspots, and other celestial phenomena.
- Types of Telescopes: Refracting (with lenses), reflecting (with mirrors).
Historical Models of the Universe
Ancient Models
- Geocentric Model: Earth as center of the universe; proposed by early Greek philosophers like Anaximander and Pythagoras.
Heliocentric Model
- Copernicus (1543): Proposed sun-centered solar system; model rejected circular orbits in favor of epicycles.
- Galileo's Support: Provided observational evidence through discoveries of Jupiter's moons and phases of Venus.
- Kepler's Laws: Described elliptical orbits for planetary motion.
The Heliocentric System & Stellar Concepts
- James Bradley (1729): First proof of Earth's orbital motion through light aberration.
- Friedrich Bessel (1838): Discovered stellar parallax, confirming the heliocentric model.
- Notable Discoveries: Variable stars and proper motion of stars by Edmond Halley (1718).
Spectroscopy and Stellar Evolution
- William Huggins (1864): Investigated the spectra of stars and nebulae confirming their gaseous nature.
- Doppler Effect: Observes shifts in spectral lines to measure the velocity of stars towards or away from Earth.
Stellar Classification and Evolution
- Main Sequence Stars: Includes 90% of stars where higher mass indicates higher luminosity.
- Spectral Classifications: Conducted through the Henry Draper Catalogue.
Astronomical Epochs
- Planetary (1600): Telescopes unveil new planets.
- Stellar (1875): Investigation of star properties.
- Galaxy (1900): Definition of galaxies and discovery of the Milky Way.
- Clusters of Galaxies (1920): Discovery of multiple galaxies.
- The Big Bang (1927): Expanding universe concept.
- Multiverse (1957): Theory suggesting multiple universes.
Theoretical Frameworks
- Observational Instruments: Evolved with technology leading to advances such as photographic and digital recordings.
- Mathematical Theories: Underpin advancements in understanding celestial phenomena, including laws of physics governing stellar dynamics.
The Electromagnetic Spectrum
- Ranges from gamma rays (highest energy) to radio waves (lowest energy), crucial for understanding the universe.