ASTRONOMY CHEAT SHEET
Introduction
Astronomy is the study of celestial objects, such as stars, planets, galaxies, and black holes. It involves observations and theoretical models to understand the properties and evolution of the universe.
Key Concepts
- Celestial objects: any natural object in space, including stars, planets, asteroids, comets, and more.
- Light years: the distance light travels in one year, which is approximately 9.46 trillion kilometers or 5.88 trillion miles.
- Redshift and blueshift: changes in the wavelength of light due to the relative motion between the observer and the object being observed. Redshift indicates that the object is moving away from the observer, while blueshift indicates that it is moving closer.
- Cosmic microwave background radiation: the leftover radiation from the Big Bang, which provides evidence for the universe’s expansion and early history.
- Kepler’s Laws of Planetary Motion: three laws that describe the motion of planets around the sun. They are:
- Law 1: Planets move in elliptical orbits with the sun at one focus.
- Law 2: A line connecting a planet to the sun sweeps out equal areas in equal times.
- Law 3: The square of the orbital period of a planet is proportional to the cube of its average distance from the sun.
- Newton’s Laws of Motion: three laws that describe the behavior of objects in motion. They are:
- Law 1: An object at rest tends to stay at rest, while an object in motion tends to stay in motion with a constant velocity, unless acted upon by a net external force.
- Law 2: The net force on an object is equal to its mass times its acceleration.
- Law 3: For every action, there is an equal and opposite reaction.
- Hubble’s Law: a law that describes the expansion of the universe. It states that the velocity of a galaxy is proportional to its distance from us.
- Black hole formula: the radius of a non-rotating black hole is given by the formula R = 2GM/c^2, where R is the radius, G is the gravitational constant, M is the mass of the black hole, and c is the speed of light.
Astronomical Units
- Astronomical Unit (AU): the average distance from the Earth to the Sun, which is approximately 149.6 million kilometers or 93 million miles.
- Parsec: a unit of distance used in astronomy, which is equivalent to 3.26 light years or 30.9 trillion kilometers or 19.2 trillion miles.
Resources