The Universe

Chapter 16

Our Universe

• Only one that exists• Includes everything

– Stars, planets, galaxies, etc.

• Commonly accepted to be created by the Big Bang– A giant explosion of a very tiny dot of

matter– Happened 15 billion years ago

Evidence of Big Bang Theory

• Red shift– As objects move away, wavelength gets

longer– Appears red or moves to the red end of the

spectrum

– When observing objects over time, their wavelengths are getting longer

Evidence of Big Bang Theory

• Cosmic Background Radiation– Faint energy waves coming from every

direction in the universe– Leftover from the Big Bang

What Will Happen?

• Fate of the Universe depends on the mass

Within the Universe…..

• Many galaxies grouped together in clusters– Held near

each other by gravity

Galaxies

• Three main types– Spiral– Elliptical– Irregular

• Classified by shape and age of stars

• Made of interstellar matter– Dust, gasses, stars, masses of rock

Spiral Galaxy

• 30% of all galaxies in the universe

• Have stars of all ages

Elliptical Galaxy

• 60% of all galaxies in the universe

• Have mostly old stars

Irregular Galaxy

• Only 10% of all galaxies in the universe

• All young stars

Our Galaxy - Milky Way

• A spiral galaxy

Within the Milky Way…..

• All stars we see are in our galaxy

• Appear to make patterns in our sky– We call these constellations– Patterns don’t really exist– Really are light years apart

• Light year measures distance• 1 light year = 9.5 x 1015 m

Stars

• Brightness in the sky depends on….– Size

• Larger = brighter

– Distance for Earth• Closer = brighter

– Temperature • Hotter = brighter

Stars

• Use color of stars to study them– Color tells us make up of stars

• Mostly hydrogen and helium

– Color can tell us temperature• Hot = blue• Cool = red

Stars

• Powered by nuclear fusion– Burn at a temperature of 15 million K– Energy takes 8 minutes to reach Earth

• Have a life cycle like living organisms– How long a star lives depends on its mass

Star Life Cycle

• Start as a nebula– Cloud of dust and gas

Star Life Cycle

• Nebula comes together in a large mass– Forms a protostar

• Nuclear fusion starts – Becomes a main sequence star– This is the true star– Lives most of its life here

Star Life Cycle

• Death of star depends on mass– Very small stars become white dwarf– Medium mass stars become a red giant,

then planetary nebula, then white dwarf– Large stars become a supergiant, then a

supernova, then a black hole or neutron star

Planetary Nebula

Supernova

Our Star - The Sun

• A typical, average, medium mass star– Right now is a main sequence star– Is in the middle of its life

• Like most of the stars in the Milky Way

• Next closest star is 4.3 light years away

Our Solar System

• Formed when a nebula started to spin– Pieces of rock and dust came together to

form planets

• Our sun and everything that orbits around it– Nine planets, Asteroids, Comets, Meteors

Our Solar System

• We can see some– Reflect the light of the sun– Appear to wonder across the sky because

they are orbiting

• We can see 5 planets – Mercury, Venus, Mars, Jupiter, and Saturn– Besides the sun and moon, Venus is the

the brightest in our sky

Division of Solar System

• Inner Planets– Mercury, Venus, Earth, Mars– Small and mostly rock

• Asteroid belt– Asteroid = small rocky object that orbits the sun– Usually found in this belt

• Outer Planets– Jupiter, Saturn, Uranus, Neptune– Very large and mostly thick gas atmosphere

Our Moon

• Rock that orbits Earth

• Reflects light of the Sun so we see it in the night sky– Depending on where it is, different

amounts of sunlight hit the moon– Makes phases of the moon

Phases of the Moon

One cycletakes

4 weeks

Eclipses

• When a shadow is cast over the sun or the moon

• Don’t happen all the time because moon’s orbit is at an angle

Solar Eclipse

You can only see a total solar eclipse when in the umbra.Total solar eclipses are very rare.

These can only occur in the new moon phase.

Lunar Eclipse

You can only see a total lunar eclipse when in the umbra.Total lunar eclipses are the most likely to be seen.

These can only occur in the full moon phase.