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Dive into the world of astronomy with a look into geocentric vs. heliocentric theories, types of galaxies, celestial bodies, and space objects like comets and asteroids. Learn about the wonders of the universe and the discoveries that shaped our understanding of space.
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SHOW ME! 10 volunteers 1 sun 9 planets
“Geo” means Earth “Helio” means sun Geocentric vs Heliocentric
The ancient Greeks observed the sky and noticed that the moon, sun, and stars seemed to move in a circle around the Earth. It seemed that the Earth was not moving and everything in the heavens revolved around the Earth. As it turned out, it was very difficult to prove that the planets did not revolve around the Earth without leaving the planet. Ancient Observations
Ancient Greeks such as Aristotle believed that the universe was perfect and finite, with the Earth at the exact center. This is the geocentric theory, which stated, the planets, moon, sun, and stars revolve around the Earth. Geocentric Theory
In AD 140 the Greek astronomer Ptolemy revised the geocentric model to explain all the planetary motions. His model had the planets move in little circles that also moved in bigger circles. This belief persisted for about 1500 years. Ptolemy(85-165 AD)
Copernicus(1473-1543) • In the early 1500’s the polish astronomer Copernicus suggested that the Sun, not Earth, was the center of the solar system and the planets revolved around it. • This is the Heliocentric Theory. • Helios means “sun” in Greek.
Galileo (year 1609) • One of the first to use a telescope to see objects in space
Isaac Newton (1687) • Showed that all objects in the universe attract each other by gravity
What is a galaxy? • A galaxy is a large grouping of stars, gas, and dust in space that are held together by gravity.
3Types of Galaxies 1. Spiral 3. Irregular 2. Elliptical
Spiral Galaxies • Shaped like flattened disks with one or more spiral arms. • Our galaxy, Milky Way, is a spiral galaxy. • Our solar system is located in one of the spiral arms.
Elliptical Galaxies • About 1/3 of all galaxies. • massive, round blobs of stars. • Round or elliptical in shape. • Contain very little gas or dust. • Because of little gas, no new stars are forming. • The largest and smallest galaxies are elliptical galaxies.
Irregular Galaxies • No defined shape • Do not fit into any other category. • Chaotic mix of stars, gas and dust • Usually found near large spiral galaxies who may be distorting their shape.
THINGS IN OUR SKY!!! • A natural satellite is any celestial body in space that orbits around a larger body.
Meteorite vs. Meteoroid • Meteoroid = while in space a meteorite is called a meteoroid • Meteorite = a small rock or rocky grain that strikes Earth’s surface • So the difference is just based on where the rock is when you are describing it
Meteor • Sometimes called a “Shooting Star” • When a meteorite enters Earth’s atmosphere, friction causes them to burn up, producing a streak of light
Comets • Bodies in space made up of ice, dust, small gritty particles • Sometimes called “dirty snowballs” • When close to the sun, ice vaporizes, producing a spectacular streak of gas, referred to as a “tail” • Many in a regular orbit around the sun
Famous Comets • Comet Hale-Bopp • Halley’s Comet • Comet Kohoutek
Asteroids • An irregularly shaped rocky object in space (like a space potato) • May be the shattered remains of objects left over from the time when the planets were formed
How big are asteroids? • Larger than meteoroids • (In fact, the main difference between meteoroids and asteroids is their size.) • Size ranges from 10 feet across to bigger than a mountain
Asteroids • Approx. 150,000 asteroids in the Solar System • Most are in a band that orbit the sun between Mars and Jupiter (Asteroid Belt) • Why are there all of those asteroids between Mars and Jupiter and not another planet?
