Galaxies and the Universe Spectra of Science Amole 2013

The Hierarchy Universe Galaxy Stars Solar System Planet World Continent Country State City

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

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

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.

The Milky Way Galaxy

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

The Big Bang Theory Misconception Alert: Describing this theory as 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

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

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

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

The Evidence Hubble found spectral lines shifted towards red

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

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”

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!

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

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

Interstellar Matter The gas and dust located between stars and galaxies

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

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)

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.)

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.

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

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?