Astronomy Fundamentals: Celestial Bodies and Space Travel
Astronomy Fundamentals and Timekeeping
Ancient people used the Sun, Moon, stars, and tools like sundials to track time and seasons.
- A solstice is the longest or shortest day of the year.
- An equinox is when day and night are equal in length.
Models of the Universe
Understanding the structure of the cosmos evolved over time:
- The geocentric model states Earth is at the center of the universe.
- The heliocentric model states the Sun is at the center and planets orbit it.
- Elliptical orbits mean planets move in oval-shaped paths instead of perfect circles.
Stars and Stellar Evolution
Star Definitions
- A star is a massive ball of hot gas that produces energy through nuclear fusion.
- A nebula is a cloud of gas and dust where stars are formed.
Stellar Life Cycles
During the main sequence, stars fuse hydrogen into helium to release energy.
The Hertzsprung–Russell diagram shows a star’s brightness, temperature, size, and life stage.
Sun-like Star Path
A sun-like star forms in a nebula, becomes a main sequence star, expands into a red giant, and ends as a white dwarf.
Massive Star Path
A massive star forms in a nebula, becomes a main sequence star, expands into a red supergiant, and explodes as a supernova, forming a neutron star or black hole.
Mapping the Sky
- A constellation is an officially recognized pattern of stars used for mapping the sky.
- An asterism is an unofficial star pattern made from parts of constellations.
Solar System Objects
Galaxies and Planets
A galaxy is a massive system of stars, gas, and dust held together by gravity.
The planets in order are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
Planet Types
- Terrestrial planets are small, rocky planets located close to the Sun.
- Jovian planets are large gas giants located far from the Sun.
Small Solar System Bodies
- Asteroids are rocky objects mostly found in the asteroid belt between Mars and Jupiter.
- Comets are icy objects that develop glowing tails when they approach the Sun.
- A meteor is a space rock that burns up in Earth’s atmosphere.
- A meteorite is a meteor that survives and hits Earth’s surface.
Measuring Space and Distance
A telescope allows scientists to observe distant objects in space.
- An astronomical unit (AU) is the average distance between Earth and the Sun.
- A light-year is the distance light travels in one year and is used for very large distances.
Locating Objects in the Sky
Two coordinates are required to precisely locate an object in the sky:
- Altitude measures how high an object is above the horizon.
- Azimuth measures the direction of an object clockwise from north.
Distance Calculation Methods
- Triangulation calculates distance by measuring from two known locations.
- Parallax is the apparent shift of an object when viewed from different positions.
- The Doppler effect shows whether a star is moving toward or away from Earth using color changes.
Space Travel and Technology
The Vacuum of Space
Space is a vacuum with no air pressure or atmosphere.
Rocket Propulsion
A rocket is a vehicle that moves by pushing gases downward to move upward.
Rockets work because of Newton’s Third Law, where every action has an equal and opposite reaction.
Rockets have three main parts: structure, fuel, and payload.
The Space Shuttle System
The Space Shuttle was a reusable spacecraft used to transport astronauts and equipment.
It had three main components: the orbiter, external fuel tank, and rocket boosters.
Dangers of Launch and Re-entry
- Launch is dangerous due to explosions and mechanical failure.
- Re-entry is dangerous because of extreme heat and friction.
Advanced Propulsion Methods
- Ion drives use charged particles for slow but efficient long-distance travel.
- Solar sails use pressure from sunlight to move spacecraft without fuel.
Life in Space for Astronauts
In space, astronauts face radiation, microgravity, and equipment failure.
Physical Challenges
- Microgravity weakens muscles and bones over time.
- The lack of up or down in space causes disorientation.
Psychological and Survival Needs
- Astronauts experience psychological stress due to isolation and confinement.
- Astronauts use special systems to get oxygen, food, and water.
- Food is packaged, water is recycled, and oxygen is produced onboard spacecraft.
- Astronauts sleep while floating and secure themselves to stay in place.
Space Suits
Space suits protect astronauts from vacuum, extreme temperatures, and radiation.
Space suits also provide oxygen and maintain proper body pressure.
Telescope Types and Observation
- An optical telescope collects visible light to observe space objects.
- A refracting telescope uses lenses to bend light.
- A reflecting telescope uses mirrors and is more powerful and commonly used.
- A radio telescope detects radio waves from space.
Interferometry combines data from multiple telescopes to create clearer images.
Spacecraft Missions
Satellites
A satellite is an object that orbits a larger body.
- Natural satellites include moons.
- Artificial satellites are human-made objects launched into orbit.
Satellites are used for communication, GPS, weather forecasting, and Earth observation.
Probes
A probe is an unmanned spacecraft sent to explore space.
Probes have traveled to planets such as Mars, Venus, and Jupiter.
Probes have discovered evidence of water and past conditions that could support life on Mars.