Chapter 15 – Stars, Galaxies and the Universe

● Section 5 – History of the Universe

Standards ● 2.g – Students know the role of gravity in

forming and maintaining the shapes of planets, stars and the solar system

● 4.a – Students know galaxies are clusters of billions of stars and may have different shapes

Chapter 15 – Stars, Galaxies and the Universe

Big Bang Theory● Big Bang Theory – initial

explosion that resulted in the formation and expansion of the universe

● Big Bang Theory states that the universe formed in an explosion about 10 to 15 billion years ago – Universe has been growing ever since the big bang

Moving Galaxies● Scientists can tell if galaxies are moving

toward or away from earth based on a light spectrum of that galaxy

● Hubble’s Law – states that the farther a galaxy is, the faster it is moving away from us – like the balloon

Expanding Universe

● Each little piece on the balloon is like a galaxy and as the balloon grows (universe expands) the galaxies move apart

Formation of the Solar System

● About 5 billion years ago, a giant cloud of gas and dust, or nebula, collapsed to form the solar system

Formation of the Solar System

● The nebula shrank to form a spinning disk and as gravity pulled some of the gas into the center of the disk, the gas became hot and dense enough for nuclear fusion to begin and created the sun

Solar Nebula● Solar Nebula – a large

cloud of gas and dust that formed our solar system

● Gravity pulled the nebula together, it shrank and spun faster

● Elsewhere in the disk, gas and dust formed solid spheres smaller than the sun and the planets were created Formation of solar system video

The Future of the Universe● New observations lead many astronomers

to conclude that the universe will likely expand forever

● Dark Matter – matter that does not give off electromagnetic radiation (possibly 90% of all matter in the universe)

● Dark Energy – mysterious force that appears to be causing the expansion of the universe to accelerate

Speeding Galaxies

Use the graph to answer the questions about moving clusters of galaxies.

● Reading Graphs:

● How far away is the Bootes cluster? How fast is it moving?

● About 2.5 billion light-years

● About 39,000 km/sec

Speeding Galaxies

Speeding Galaxies

● Reading Graphs:

● Which galaxy is moving away the fastest? Which galaxy is closest to Earth?

● Hydra● Virgo

Speeding Galaxies

● Drawing Conclusions:

● How are the distance and speed of a galaxy related?

● The greater the distance from Earth, the greater the speed of the galaxy.

Speeding Galaxies

● Predicting:

● Predict the speed of a galaxy that is 5 billion light-years from Earth

● Its speed would be about 80,000 km/s