The Universe and Galaxies Adapted from: http://www.west-jefferson.k12.oh.us/earthandspacescience.aspx
Astronomy The study of objects and matter outside the Earth s atmosphere and of their physical and chemical properties.
What is the Universe? Universe - sum of all matter and energy that ever has, does, and ever will exist everything physical that exists in space and time Cosmology the study of how the universe began, what it is made of, and how it continues to evolve and change
The Composition of the Universe (What it is made of ) Stars, planets, rocks, comets, asteroids, dark matter, and dark energy
The Composition of the Universe (What it is made of ) Dark matter theoretical unseen and undetectable mass that adds to the gravity of a galaxy Dark energy theoretical energy that might be causing accelerated expansion of the universe
Most of What We See in Space Are Stars - huge balls of hot gases that emit (gives off) light Stars are grouped together by the millions and billions into galaxies Stars
Astronomical Distance Measured in light years Light year - the distance light travels in one year. The estimated distance that light travels in a year is ~6 trillion miles or 10 trillion kilometers
Astronomical Distance Astronomical Unit- The distance from the Earth to the Sun An estimated 150 million kilometers or 93 million miles, which is equal to 8 light minutes We use AU s as the unit of measure within our solar system and light years for the distances within the universe.
Looking into the Past Time is required for light to travel through space Light travels a little over 8 minutes from the sun to earth The farther away an object/star is, the longer it takes for light to get to us, and the older the light is when it gets to us = Light is OLD We see the past of other stars in the night sky
Looking into the Past Light from the nearest galaxy, Andromeda, was emitted 2.5 million years ago. Therefore, the images we see of these objects are how they looked at the time in the past when their light left them. The farther away an object is, the older the light is that we are receiving from it.
Galaxies Galaxy - grouping of millions or billions of stars,dust, and gas held together by gravity There are an estimated 100 billion galaxies in the universe 3 Types of Galaxies - classified by shape
Galaxies Spiral Galaxies- disk shaped with spiral arms of dust and gas Dust and gas provide a place for new stars to form Young stars are bluish in color gives spiral galaxies a blue tint Looks like a pin wheel Milky Way is a spiral galaxy
Galaxies Elliptical Galaxy most common type of galaxy Spherical and egg shaped NO spiral arms, little dust and gas Generally have older stars (reddish in color)
Galaxies Irregular Galaxy least common type of galaxy NO well defined shape or structure Some have little dust or gas Some have lots of dust and gas
Milky Way Galaxy The galaxy we live in Consists of stars and clouds of dust and gas between stars (interstellar matter) All the stars we see at night are in the Milky Way galaxy (about 400 billion stars)
Milky Way Galaxy side view A huge spiraling disk of stars and interstellar matter 1000 l.y. thick
Milky Way Galaxy Overhead View A huge bulge in the center 10,000 l.y. thick
Where Are We In The Galaxy? Our solar system is about halfway between the center and the edge of the galaxy (26,000 light years from the center)
Milky Way Galaxy The nearest galaxy to ours is the Andromeda galaxy 2.6 million l.y. away
Gravity Holds Galaxies Together Dust, gases, and stars are attracted to each other by gravity Galaxies are grouped into clusters groups of galaxies bound together by gravity
Gravity Holds Galaxies Together Milky Way and Andromeda galaxies are in a cluster of ~45 galaxies called the Local Group Superclusters - have thousands of galaxies largest structure in the universe
Universe Origins The universe is composed of matter and energy. All of the matter in the universe now was in the universe when it formed. The Big Bang Theory is currently the most widely accepted theory among scientists on the origins of the universe. Astronomers and cosmologists have evidence regarding this theory.
Big Bang Theory Basics Main Premise: The universe began with a gigantic explosion (expansion of matter) ~13.7 billion years ago Nothing existed before this No time, NO space Out of nothingness came everything in the universe and it started to expand
Big Bang Evidence Looking at the oldest stars Cosmic background radiation that astronomers have picked up from various EM wave capturing technologies By measuring the rate the Universe is expanding-astronomers what is called red shift. As the universe expands and galaxies move apart, the wavelength of light given off by those galaxies is stretched. This shifts the light toward the red end of the spectrum. The more distance or faint a galaxy the more rapidly it is moving away from Earth.