Astronomy Review Session

Fasten Your Seat Belts And get ready for the ride!

Axis of Rotation Period of Rotation

an imaginary line that runs through the center of the earth. (The earth rotates around this line.)

The time it takes for one rotation around the axis to occur. (one day)

Period of Revolution Ellipse The time it takes a planet

to move completely around the sun. (one year)

Oval shaped. (example: Earth’s orbit around the sun is an oval or ellipse.)

ALL planets have elliptical orbits around the sun (Kepler’s first law)

Astronomical Unit The average distance

from Earth to the Sun. 1 AU = 149,600,000km

Planet Classification

Terrestrial Planets:

Gas Giants: Mercury Venus Earth Mars

Jupiter Saturn Uranus Neptune

Dwarf Planets:

Ceres Pluto Haumea Makemake Eris

** ICE Giants are: Uranus & Neptune

Earth, Moon, SunWho’s orbiting who?

Satellites? Moons? What’s the difference?

The Moon is the Earth’s satellite and technically, Earth is one of the Sun’s Satellite.

A Satellite is an object that revolves around a planet.

Lunar Vs. Solar EclipseLunar Eclipse Solar Eclipse

when the Moon passes between the Sun and the Earth, and fully or partially covers the Sun (specific viewing point).

when the moon passes behind the earth such that the earth blocks the sun’s rays from reflecting off of the moon.

Cosmic Vagabonds

Asteroids:

Comets:

A rocky object revolving around the sun, smaller than a planet, that are found between the orbits of Mars and Jupiter. A small clump of ice and

dust with an elliptical orbit around the Sun.

As it nears the sun on it’s orbit, the ice sublimes and forms the coma and tail. (please draw a picture)

Meteoroids: Are solid, interplanetary

particles passing through Earth’s atmosphere.

Meteors? Meteorites? Meteoroids? What’s the difference?!?!

The Quick Trick: - “oids” are outside the

atmosphere, - “ites” are inside it, and – “ors” are in between.

Meteoroids outside atmosphere Meteorites inside atmosphere Meteors in-between

Meteoroids Meteors Meteorites

What IS a star anyway?!?!STARS:A star is a large ball of gas, held together by gravity, that emits energy produced by nuclear reactions in it’s interior.

Types of stars: Stars are classified by their

size, temperature, and brightness!

Classifying Stars

SIZE!!!! Temperature!!! Super Giant Red Giant Main Sequence White Dwarf Neutron Star

Hot = Red Hotter = White Hottest = Blue/White

Brightness! How bright it appears depends

on it’s distance from us How bright it actually is

depends on it’s size and temp.

3,500 K 5,000 K 7,000 K 25,000 K

Relationship between surface temperature and color of stars:

Just like cars headlights look small and dim when they are far away and then BLIND you as they get closer, Stars are similar.

You may notice at night when you look up at the stars that some seem to be slightly different colors, that has to do with their temperature!

Apparent vs. Absolute

Apparent Magnitude Absolute Magnitude The observed luminosity

of a celestial body, such as a star, as observed from earth.

The apparent magnitude of a star depends on it’s luminosity and distance.

The apparent magnitude a star would have if it were 32.6 ly away from Earth.

Apparent vs. Absolute

Apparent Magnitude Absolute Magnitude The observed luminosity

of a celestial body, such as a star, as observed from earth.

The apparent magnitude of a star depends on it’s luminosity and distance.

The apparent magnitude a star would have if it were 32.6 ly away from Earth.

The Life of a Star…

1. Protostar- born in a nebula, gases come together and begin nuclear fusion.

2. Star- the phase where the star burns fuel. The more massive the star, the shorter it’s lifespan!

3. Red giant/supergiant- when stars run out of fuel, the outside expands and the inside contracts.

4. White Dwarf-One possible outcome. The remainder of a star, after the outer layer expands away.

5. Super Nova- If a star doesn’t become a white dwarf, it will supernova (aka- explode!)

6. Neutron Star- What’s left after a supernova (suuuuper dense core)

7. Black Hole- The most massive pre-supernova stars may become black holes after they supernova. The density reaches extreme highs and pulls everything inward to the point where light cannot even escape!

The Life of a Star…

How do stars produce light?? Stars produce light by Nuclear FUSION.

This is when two atomic nuclei combine to form a larger nucleus with a higher mass.

(ex: hydrogen becomes helium)

Galaxies are…

Massive systems of stars, dust and gas held together by gravity.

Spiral Galaxies… Distinct central

concentration of stars (bulge) at center with spiral arms radiating outward.

Spiral galaxies make up approximately 60% of the galaxies in the Universe.

Barred Spiral Galaxies…

Similar to a regular spiral galaxy but with a cross bar cutting through the center with arms swirling at the ends

Elliptical Galaxies…

You guessed it! They are elliptical in shape!! (I know you know what that means…)

Irregular Galaxies…

These are the galaxies that are neither elliptical nor spiral; they are a variety of shapes.

The Milky Way Galaxy- Our Galaxy!

Barred spiral galaxy 90,000 Light years in

Diameter Every star we see in

the night sky Rotates Clockwise

Milky Way

Let’s go back in time…

Before the Big Bang, all of the matter in the universe was together at one point, creating a small, hot and very dense Universe.

After the Big Bang, matter in the Universe separated into galaxies containing gas and dust.

Ok, so how did our solar system start?

1. About 5 mya a giant cloud of gas and dust (nebula) collapsed to form the solar system

2. It slowly shrank (compressed) to form a spinning disk.

3. It became hot enough for the sun to form through nuclear fusion.

4. Gas and dust formed solid spheres smaller than the sun which became planets.