All matter and energy, including the earth, the galaxies, and the contents of intergalactic space, regarded as a whole.

A component of our universe made up of gas and a large number (usually more than a million) of stars held together by gravity. When capitalized, Galaxy refers to our own Milky Way Galaxy.

Three types of galaxies: Elliptical Spiral Irregular

Have a round Oval Shape

Pinwheel Shape

No predictable shape

Spiral Are huge Contain

stars, gas, & dust

Are held together by gravity

A halo is present

Elliptical

Are huge Contain

stars, gas, & dust

Are held together by gravity

A halo is present

Irregular

Are huge Contain

stars, gas, & dust

Are held together by gravity

A halo is present

Spiral Round to

oval shape

Bulge, but no disk

Small amount of cool gas & dust

Mainly old stars

Elliptical

Pinwheel shape

Bulge & a thin disk

Rich in gas & dust

Young & old stars

Irregular No

predictable shape

May show signs of a disk &/or a bulge

Usually rich in gas & dust

Young & old stars

Our place in the universe. This figure illustrates our cosmic address. The Earth is one of the nine planets in our solar systems, our solar system is one among 200 billion star systems in the Milky Way Galaxy; the Milky Way is one of the two largest of about 30 galaxies

Ask an Astrophysicist  Size: The disk of the Milky Way galaxy is

about 100,000 light years in diameter (one light year is about 9.5 x 1015 meters), but only about 1000 light years thick.

Our Galaxy contains about 200 billion stars. Most of the stars are located in the disk of our galaxy, which is the site of most of the star formation because it contains lots of gas and dust.

Solar System's orbit within Milky Way Galaxy. The sun is ONE of the estimated 200 billion stars in this galaxy.

Our solar system consists of:

the sun, eight planets, moons, many dwarf planets (or plutoids), an asteroid belt, comets, meteors, and others.

The sun is the center of our solar system; the planets, their moons, a belt of asteroids, comets, and other rocks and gas orbit the sun.

A Globule of Gas:Our solar system formed about 4.6 billion years ago, from an enormous cloud of dust and gas, a nebula.

The Sun, like other stars, was formed in a nebula, an interstellar cloud of dust and gas (mostly hydrogen).

These stellar nurseries are abundant in the arms of spiral galaxies (like our galaxy, the Milky Way).

Later, the Sun stabilizes and becomes a yellow dwarf, a main sequence star which will remain in this state for about 10 billion years. After that, the hydrogen fuel is depleted and the Sun begins to die.

Inner- Terrestrial (Land)

Mercury, Venus, Earth, & Mars

Closer to the Sun Are rocky & have

craters Atmosphere: Mercury-

N/A; other planets have CO2 in common. Earth only one w/O2

http://lasp.colorado.edu/education/outerplanets/solsys_planets.php

Outer- Gas Giants

Jupiter, Saturn, Uranus, Neptune, & Pluto (a dwarf planet)

Farther from the Sun (cooler)

Farther apart from one another

Are made of gas Atmosphere:

mostly Helium & Hydrogen

Jupiter: Strongest gravitational attraction

Although Saturn, Uranus, and Neptune are also very massive planets, their gravitational forces are about the same as Earth.

This is because the gravitational force a planet exerts upon an object at the planet's surface is proportional to its mass and the planet's radius squared.

Inner- Terrestrial Mercury, Venus,

Earth, & Mars Few moons Mercury & Venus no

moons

Outer- Gas Giants Jupiter, Saturn,

Uranus, Neptune, & Pluto (a dwarf planet)

Many moons Jovian Planets collapsed,

smaller particles in the surrounding disk formed into some of the moons that now orbit the individual outer planets. This makes sense, since the outer planets all have many moons and rings.

Inner- Terrestrial Mercury, Venus,

Earth, & Mars No rings

Outer- Gas Giants Jupiter, Saturn,

Uranus, Neptune, & Pluto (a dwarf planet)

Rings The rings are thin discs

of dust and rocks possibly caused by moons being broken up or not being completely formed while orbiting the planet.

An asteroid is a bit of rock. "left overs" after the Sunand all the planets were formed. Most of the asteroids in our solar system can

be found orbiting the Sun between the orbits of Mars and Jupiter.

This area is sometimes called the "asteroid belt“.

Think about it this way: the asteroid belt is a big highway in a circle around the Sun. Think about the asteroids as cars on the highway.

The asteroid belt lies between the orbits of Mars & Jupiter. Jupiter is the most massive body in our solar system after the Sun, and it therefore exerts a

substantial amount of gravity on the objects around it.

The competing gravitational influence of Jupiter and the Sun did not allow the bits and pieces of the asteroid belt to accrete into a larger planet.

Probably a rocky planet similar to Mars, except smaller. All the asteroids combined are not as much mass as Mars is.

A meteor is a bright streak of light that appears briefly in the sky.

Observers often call meteors shooting stars or falling stars because they look like stars falling from the sky.

A meteor appears when a particle or chunk of metallic or stony matter called a meteoroid enters the earth's atmosphere from outer space.

Why was early Earth hit with so many meteors than the current Earth?

They delivered enough carbon dioxide and water vapor to turn the atmosphere of planets into warmer and wetter environments that were more habitable for life.

Also, increased Earths size and caused thermal energy.

(1) the Earth has the right conditions (such as carbon and a temperature that allows liquid water)

It is at a perfect distance from the Sun; not too hot, not too cold. A temperate climate.

Earth is 94 million miles (150 million km) from the Sun.

Ideal gravity which makes moving about easy without the difficulty of heavy gravity and low gravity. Earth's diameter is 7,926 miles (12,756 km).

Stars are born in nebulae. Huge

clouds of dust and gas collapse under gravitational forces, forming protostars. These young stars undergo further collapse, forming

main sequence stars.

Stars expand as theygrow old. -As the core runs out of hydrogen & then helium, the core contacts & the outer layers expand, cool, & become less bright. - This is a red giant - or a red super giant - (depending on the initial

mass of the star). It will eventually collapse and explode.

- Its fate is determined by the original mass of the star; it will become either a black dwarf, neutron star, or black hole.

H-RDiagram- O and B

stars are uncommon but very bright

- M stars are common but dim..

The Hertzsprung -Russell (H-R) Diagram is a graph that plots stars color (spectral type or surface temperature) vs. its luminosity (intrinsic brightness or absolute magnitude). On it, astronomers plot stars' color, temperature, luminosity, spectral type, and evolutionary stage.

This diagram shows that there are 3 very different types of stars:

Most stars, including the sun, are "main sequence stars," fueled by nuclear fusion converting hydrogen into helium.

For these stars, the hotter they are, the brighter.

As stars begin to die, they become giants and supergiants (above the main sequence).

These stars have depleted their hydrogen supply and are very old.

The core contracts as the outer layers expand. These stars will eventually explode (becoming a planetary nebula or supernova, depending on their mass) and then become

white dwarfs, neutron stars, or black holes (again depending on their mass).

Smaller stars (like our Sun) eventually become faint white dwarfs (hot, white, dim stars) that are below the main sequence.

These hot, shrinking stars have depleted their nuclear fuels and will eventually become cold, dark, black dwarfs.

is the apparent change in the position of a star that is caused only by the motion of the Earth as it orbits the Sun.

Earth only planet currently suitable for Ag As of the year 2000, about 37 percent of

Earth's land area was agricultural land. Characterizes land's suitability for agriculture

based on physical parameters like climate, soil, and topography.

Unsuitable land surfaces for growing is subject to some soil, terrain, and/or climate limitations.

How is animal breeding cycles impacted by the rotation of Earth? Sheep are seasonal breeders, with the

majority being short-day breeders that cycle in the fall and lamb in the spring of the year.

However, some breeds of sheep will cycle in the spring and have lambs in the fall.

Through the eye of the sheep, its brain perceives day length and sends appropriate signals (hormones) to the reproductive system to begin the breeding season.