Galaxies and the Universe

1. Galaxies and the Universe Spectra of Science Amole 2013

2. The Hierarchy

3. The Universe • The sum of all space, matter, and energy that exists, has existed, or will exist • There is only one • You are part of it too! • We see it as it was in the past • Contains many other galaxies • Most of it is empty space

4. The Hubble Telescope • A reflecting telescope that was placed into orbit in 1990 • Sends images and measurements back to Earth electronically • A deep image of an “empty” portion of the sky reveals that the universe is filled with galaxies • The light we see from the most distant galaxies has traveled approximately 10 billion years to reach us

5. Galaxies Fun Fact: If you counted 1,000 galaxies a night, it would take 275, 000 years! • A collection of stars, dust, and gas bound together by gravity • We live in the Milky Way galaxy • There may be more than 100 billion galaxies • Not spread out evenly through space; exist in clusters • Clusters can join and form superclusters Fun Fact: The Milky Way is part of a cluster called the Local Group.

6. The Milky Way Galaxy

7. Galaxy Types Elliptical shaped like spheres or eggs; have almost no dust or gas between stars; contain old stars Spiral have arms of stars, gas , and dust that curve away from the center of the galaxy in a spiral pattern Ex. – Milky Way Irregular faint galaxies without a definite shape; smaller than the other types of galaxies; contain fewer stars

8. The Big Bang Theory • Occurred 10-20 billion years ago • Before there was nothing • No space; No time • Out of nothingness came an explosion of energy in all directions • This energy gave rise to all the matter we know today • Thought to have expanded within a second from something the size of a spec of dust to the size of our solar system Misconception Alert: Describing this theory as the “Big Bang” is a misnomer because there really was not an explosion, just a release of energy

9. The Big Bang • After 3 minutes, protons and neutrons began to fuse to form the nuclei of hydrogen and helium atoms • About 300,000 years later, temperatures were cool enough for complete hydrogen and helium atoms to form • Photons escaped from matter about the same time, and light existed for the first time

10. The Big Bang • After under a billion years the first stars form • They live and die slowly creating heavier elements • Galaxies and clusters also begin to slowly follow

11. The Evidence • Edwin Hubble determined that other galaxies exist, besides the Milky Way • He observed that galaxies were moving away from each other • Hubble Law – the farther away a galaxy is, the faster it is moving away from us; supports the Big Bang Theory

12. The Evidence • Hubble found spectral lines shifted towards red

13. The Evidence • Explained by the Doppler Effect • Objects that are moving away from us emit longer wavelengths • Toward the red end of the spectrum

14. The Evidence • Arno Penzias & Robert Wilson accidentally detected faint radiation on a radio telescope in 1965 • Determined that the radiation was leftover thermal energy from the “big bang”

15. The Fate of the Universe • The universe will keep expanding forever • The expansion of the universe will gradually slow down, and approach a limit in space • The universe will stop expanding and start to fall back in on itself The fate will depend on mass!

16. The Fate of the Universe • Too much = gravity will cause everything to collapse on itself • Too little = not enough gravity to stop expansion • Just right = it will slow down, but never really stop

17. Einstein’s Theory of Relativity • Mass curves space • Think about how a mattress reacts when you sit on it • During a solar eclipse scientists noticed stars were in different positions than expected

18. Interstellar Matter • The gas and dust located between stars and galaxies

19. Quasar • The most distant and radiant objects in space • Discovered by the radio waves that they emit • May be infant galaxies • May have huge central black holes

20. Dark Matter • Highly debated • Scientists have evidence that there may be more matter than just that that is visible • As much as 90% of universe may be dark matter • Could be planets, black holes, or brown dwarfs (stars that never start fusion)

21. Astronomical Unit (AU) • unit of distance equal to the average spacing between the Earth and the Sun • equal to about 150 million kilometers (93 million miles) • light takes about eight minutes to cover this distance The Earth animation is not rotating in the correct direction; it should be rotating from west to east 150 million km (93 million mi.)

22. Light Year • the distance that light travels in one year in a vacuum, which is about 9.5 trillion kilometers (6 trillion miles) • The Milky Way Galaxy is about 100,000 light years in diameter • the speed at which light travels this distance is about 300,000 km/sec (186,000 mi/sec) Fun Fact: The second closest star to the Earth is a little over four light years away.

23. Parsec • unit of distance equal to about 3.26 light years (or 206,265 AU)

24. Parallax • the apparent shift in position of an object when viewed from different locations • used by astronomers to measure distance Try This: Focus on the star to the left. Open and close your eyes in an alternating manner. What do you notice about the star’s position?