Cosmology and Celestial Objects Vocabulary

Flashcards for vocabulary review of cosmology, celestial objects, electromagnetic spectrum, stars, Earth's position, solar system, Kepler's Laws, and the Moon. Terms and definitions are drawn directly from the lecture notes provided.

Cosmology

The study of the origin and the evolution of the universe.

Big Bang Theory

The theory of how the universe came to be in existence.

Doppler Effect

The apparent change in frequency as an object moves past you.

Redshift

When we look at distant galaxies, the Electromagnetic Spectrum (light) from these galaxies is shifted towards the red end of the spectrum.

Gravitational Redshift

This type of redshift has nothing to do with the expansion of the universe and is not proof of the Big Bang. We know that massive objects create gravity.

Arno Penzias and Robert Wilson

These two radio astronomers were hired by Bell to start exploring the use of microwaves and/or radio waves for communication purposes and realized that the cause of the hiss was Microwave radiation.

Cosmic Microwave Background Radiation (CMBR)

Shows the microwave radiation present throughout the entire universe.

The Sun

The brightest object in the sky, largest object in the solar system; A star; 99.8% of the entire solar system’s mass.

The Main Sequence

When temperature and brightness are graphed, most stars exist here.

Protostars

The name we give to stars that are brand new and have quite yet ignited and started nuclear fusion.

Planets

Any object that is large enough to have rounded itself out due to its own gravity but, not so large that it triggers nuclear fusion in its core.

Moon/Natural Satellite

Any object that is large enough to be round and orbit a planet

Asteroids

Any large, irregularly shaped object that orbits around the sun.

Meteoroids

Any small irregularly shaped rocky object that orbits the sun.

Meteors

Any kind of small meteoroid that enters Earth’s atmosphere and starts glowing.

Meteorite

The chunk of rock that survives the burn through the atmosphere and lands on earth.

Comets

A small icy object (primarily water, ammonia, methane and CO2) that has part of its orbit close to the sun and can reach the outermost parts of our solar system.

The Milky Way

Our own galaxy.

Galaxies

Once thought to simply be just stars; With better telescopes, we saw that they were indeed a gravitationally bound system of stars like our own Milky Way Galaxy.

Spiral Galaxies

Look like a pinwheel from above; Has many long “arms” spiraling out from the center.

Elliptical Galaxies

Range in shape from a perfect sphere to a stretched-out ellipse; Contain some of the oldest stars in the universe; Over half of all galaxies are elliptical and they're typically the largest.

Irregular Galaxies

Made up of newly forming stars as well as old stars.

The Interstellar Medium (ISM)

All the dust, gas, atoms, particles, and cosmic rays that fill the space between planets, stars, and galaxies.

Planetary Nebulae

Were once thought to be gaseous planets like that of Neptune; With better telescopes, we realized that they were just the aftermath of an exploded star!; Hot expanding gas with a small white dwarf star in the middle.

Diffuse Nebulae

Any region of dust and gas that are extended and contain no defined boundaries; Often, so dense it will prevent light from passing through it; Usually comprised of hydrogen gas and are the home of new star birth.

Astronomical Unit (AU)

From the Sun to the Earth.

Parallax

A displacement (or difference) in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines.

Parsec

If a star ‘wobbles’ with an amplitude of one arcsec as earth moves around its orbit, then it is defined as being 1 Parsec away from our sun.

Light Year

Is how far a photon of light can travel in one year through flat, empty space.

How We See Things

When light (everything in the EM spectrum) strikes an object, some of it bounces off and makes it s way to our eyes).

Stars

Giant balls of burning gas.

Spectroscopy

A spectroscope (or spectrometer) is an instrument that is used to measure the properties of light as it is emitted (or passed through) an object.

Constellations

Are nothing more than an artistic representation of what people ‘see’ in the sky.

Asterisms

Is a any pattern of stars that we can recognize from Earth that is not a constellation.

Ecliptic

This apparent change in position of the Sun tracks a path through the sky.

Celestial Sphere

Is to imagine that the stars exist on a giant dome that is infinitely away from AND surrounding the earth.

Declination

Up and down from the celestial equator (like latitude)

Ascension

Left and right along the celestial sphere

The Sun

Composed of 75% hydrogen and 25% helium by mass, in its core, the Sun combines hydrogen into helium and energy (fusion).

Planets

To be qualified for a planet, the object must be large enough to have rounded itself out due to its own gravity – However, it cannot be so large that it triggers nuclear fusion in its core

Geocentric Model

Revolved around Earth

Heliocentric Model

Put the sun at the Center and everything else orbiting it

Geo-Heliocentric Model

Put the Earth at the Center with the Sun, the Moon and the stars going round the Earth while the rest of the planets went around the Sun

Perihelion (or Perigee)

Point closest to the Sun.

Aphelion (or Apogee)

Point furthest from the Sun

Terminology

The semi-major axis: A line that runs from the centre, through a focal point and to the perimeter.

Solar System

Encompasses everything that the Sun can influence

Solar Wind

Is composed of charged particles (mostly electrons and protons) that are ejected from the sun at speeds around 400 km/s

Transit

If a celestial body does not completely cover another

How do Eclipses Happen

he mean inclination of the lunar orbit to the ecliptic plane is 5.145°