Astronomy Fundamentals

Study Notes

Definition: A region in space where the gravitational pull is so strong that nothing, including light, can escape.
Formation: Formed when a massive star collapses in on itself, causing a massive amount of matter to be compressed into an incredibly small space.
Characteristics:
- Singularity: A point of infinite density and zero volume at the center of the black hole.
- Event Horizon: The point of no return around a black hole, where the gravitational pull is so strong that anything that crosses it will be pulled in.
- Ergosphere: A region around a rotating black hole where the curvature of spacetime is so strong that it can extract energy from objects that enter it.

Stages of a star's life:
1. Protostar: The earliest stage of a star's life, where a cloud of gas and dust collapses to form a star.
2. Main Sequence: The longest stage of a star's life, where it fuses hydrogen into helium in its core.
3. Red Giant: A stage where a star expands to become much larger and cooler as it runs out of hydrogen fuel.
4. White Dwarf: A stage where a star has exhausted its fuel and has shrunk to a small, hot, and extremely dense state.
5. Neutron Star or Black Hole: The final stage of a star's life, where it has collapsed into a neutron star or black hole.
Factors affecting a star's life cycle:
- Mass: More massive stars live shorter lives and end in a supernova explosion.
- Metallicity: Stars with higher metal content live longer and have a more stable life cycle.

Galaxy types:
- Spiral: Galaxies with a disk shape and spiral arms, such as the Milky Way.
- Elliptical: Galaxies with an egg-like shape, often formed by the merger of smaller galaxies.
- Irregular: Galaxies with a irregular shape, often formed by the collision of galaxies.
Galaxy evolution processes:
- Star formation: The process of creating new stars within a galaxy.
- Galaxy mergers: The collision of two or more galaxies, resulting in a new, larger galaxy.
- Galaxy interactions: The gravitational interaction between galaxies, affecting their shape and structure.
Galaxy evolution timeline:
- Early universe: The first galaxies formed from the gravitational collapse of gas and dust.
- Galaxy mergers and interactions: Galaxies collided and merged, resulting in the formation of larger galaxies.
- Present day: Galaxies continue to evolve through star formation and galaxy interactions.

Definition: High-energy particles that bombard the Earth from space, originating from outside the solar system.
Sources:
- Supernovae: Explosions of stars that accelerate particles to high energies.
- Active Galactic Nuclei (AGN): Supermassive black holes at the centers of galaxies that accelerate particles.
- Gamma-Ray Bursts (GRB): Extremely powerful explosions that accelerate particles.
Effects on Earth:
- Radiation: Cosmic rays can cause radiation damage to living organisms and electronic systems.
- Particle showers: Cosmic rays can interact with the atmosphere, producing particle showers that can be detected on the ground.

Types of space missions:
- Orbiter: A spacecraft that orbits a planet or celestial body to gather data.
- Lander: A spacecraft that lands on a planet or celestial body to gather data.
- Flyby: A spacecraft that flies by a planet or celestial body to gather data.
Examples of space missions:
- Hubble Space Telescope: An orbiting telescope that has made numerous groundbreaking discoveries about the universe.
- Voyager 1: A spacecraft that has traveled further than any other human-made object, entering interstellar space.
- Curiosity Rover: A lander that has been exploring Mars since 2012, discovering evidence of water and potential habitability.

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