Introduction to Astronomy

Astronomy is the scientific study of celestial bodies, space, and the universe as a whole.

Observational Astronomy
- Focuses on acquiring data from observations of celestial objects.
- Utilizes telescopes and other instruments.
Theoretical Astronomy
- Involves the development of models and simulations to understand astronomical phenomena.
- Applies mathematics and physics to predict celestial behaviors.
Astrophysics
- Combines aspects of physics and astronomy to understand the nature and behavior of celestial bodies.
- Studies concepts like gravity, radiation, and the fundamental forces of the universe.
Planetary Science
- Examines planets, moons, and planetary systems, including their composition and geology.
Cosmology
- Study of the universe's origin, evolution, structure, and eventual fate.
- Explores the Big Bang theory, dark matter, and dark energy.

Stars
- Luminous celestial bodies composed of plasma, undergoing nuclear fusion.
- Examples include the Sun, red giants, and white dwarfs.
Planets
- Large celestial bodies orbiting stars; can be terrestrial (rocky) or gas giants.
- Notable planets: Earth, Mars, Jupiter, Saturn.
Moons
- Natural satellites that orbit planets.
- Example: Earth's Moon.
Galaxies
- Vast systems of stars, gas, dust, and dark matter bound by gravity.
- Types include spiral, elliptical, and irregular galaxies.
Nebulae
- Clouds of gas and dust in space, often the birthplaces of stars.
- Types include emission, reflection, and dark nebulae.

Light Year
- A unit of distance; the distance light travels in one year (~9.46 trillion kilometers or ~5.88 trillion miles).
Gravity
- The force that attracts objects with mass towards each other; essential for the formation of celestial bodies and orbits.
Redshift/Blueshift
- Redshift indicates objects moving away from an observer, while blueshift indicates objects moving closer; used to measure the universe's expansion.
Hubble's Law
- The observation that galaxies are moving away from us, with their velocity proportional to their distance, suggesting the universe is expanding.

Telescopes
- Instruments that gather and magnify light from distant objects.
- Types: optical, radio, X-ray, and space telescopes.
Spectroscopy
- Technique used to determine the composition, temperature, density, and motion of celestial bodies by analyzing their light spectrum.
Space Probes
- Unmanned spacecraft designed to collect data from other celestial bodies (e.g., Voyager, Mars rovers).

Galileo Galilei
- Pioneered the use of telescopes in astronomy and discovered Jupiter's moons.
Isaac Newton
- Developed the laws of motion and universal gravitation, foundational to celestial mechanics.
Edwin Hubble
- Observed and formulated Hubble's Law, contributing to the understanding of the expanding universe.

Observational Astronomy
- Focuses on data acquisition through celestial observations using telescopes and instruments.
Theoretical Astronomy
- Develops models and simulations to explain astronomical phenomena, employing math and physics.
Astrophysics
- Merges physics and astronomy to explore the nature of celestial bodies, investigating gravity and radiation.
Planetary Science
- Analyzes planets and moons, including their composition and geology.
Cosmology
- Investigates the universe’s origin, evolution, structure, and ultimate fate, focusing on concepts like the Big Bang.

Stars
- Luminous entities composed of plasma; undergo nuclear fusion. Example: the Sun.
Planets
- Large bodies orbiting stars, categorized into terrestrial (rocky) and gas giants. Notable examples include Earth, Mars, and Jupiter.
Moons
- Natural satellites that orbit planets, like Earth's Moon.
Galaxies
- Massive systems of stars and matter bound by gravity, categorized as spiral, elliptical, or irregular.
Nebulae
- Gas and dust clouds in space, often stellar nurseries, classified as emission, reflection, or dark nebulae.

Light Year
- A distance unit equivalent to the distance light travels in one year, approximately 9.46 trillion kilometers.
Gravity
- A fundamental force attracting objects with mass towards each other, crucial to celestial formation and orbits.
Redshift/Blueshift
- Redshift shows objects moving away, while blueshift indicates approaching objects; these help measure cosmic expansion.
Hubble's Law
- Observes that galaxies recede proportionally to their distance, supporting the theory of an expanding universe.

Telescopes
- Instruments for gathering and magnifying distant light; includes optical, radio, and space telescopes.
Spectroscopy
- Analyzes light spectra to ascertain the composition, temperature, and motion of celestial bodies.
Space Probes
- Unmanned spacecraft for data collection from celestial bodies; notable examples include Voyager and Mars rovers.

Galileo Galilei
- Innovator in telescope usage, noted for discovering Jupiter's moons.
Isaac Newton
- Formulated the laws of motion and universal gravitation, essential to celestial mechanics.
Edwin Hubble
- Established Hubble's Law, enhancing the understanding of the expanding universe.