Lecture 1 Flashcards
What is our place in Universe?
Earth - Solar System - Milky Way Galaxy - Local Group - Local Supercluster
A cosmic Inventory
Stars, planets, moons, Asteroids, Comets, Solar System, Nebulae, Galaxies, Galaxies Groups, Galaxy Clusters, Universe
Star
A large, glowing ball of gas that generates heat and light through nuclear fusion
Planet
A moderately large object that orbits a star, it shines by reflected light. Planets may be rocky, icy, or gaseous in composition
Moon
An object that orbits a planet
Asteroid
A relative small and rocky object that orbits a star
Comet
A relatively small and icy object that orbits a star
Solar (Star) System
A star and all the material that orbits it, including its planets and moons
Nebula
An interstellar cloud of gas and/or dust
Astronomical Unit (AU)
Average distance between the Earth and the Sun (150 million kms)
Light Year
the average distance that light can travel in 1 year
Is light year a distance measurement or a time measurement?
Distance Measurement
Where to find the Orion Nebula
The Orion Nebula is about 1350 light years away and 13 light years wide
It is a star forming region
Galaxy
A great island of stars in space, all held together by gravity and orbiting a moon center
Where to find the Andromeda Galaxy
The Andromeda galaxy is about 2.5 million light years away. It will collide with the Milky Way Galaxy in 4 billion light years
Galaxy group
A gravitationally bound group of up to a few dozen galaxies typically a few million light years across
Galaxy Cluster
A group of a few hundred to a few thousand galaxies
Abell 1689, about 2.2 billion light years away
Light Travels at
Finite speed of 300,000km/s
Light travel time to moon
1 second
Light travel time to sun
8 minutes
Light travel time to Sirius
8 years
Light travel time to Andromeda Galaxy
2,5 million years
How do we see objects as they were in the past?
The farther away we look in distance, the further back we look in Time
Can we see the Entire Universe?
No, we cannot see the entire universe, because the universe is only about 14 billion years old. Its too far away for us to see it
How did we come to be?
The Universe is expanding
All galaxies are moving away from each other
Tracing this motion backward leads to a point where the expansion began, referred to as the Big Bang
Gravities drives collapse of matter into galaxies and galaxy clusters
Most galaxies formed within a few billion years after the Big Bang.
How did Gravity play a role in “How did we come to be?”
Gravity drives collapse of clouds of gas and dust to form stars and planets
Stars go through
Life cycles
How did we come to be?
The Big Bang produced hydrogen and helium.
– All other elements were constructed from H and He in stars
and then recycled into new star systems, including our solar
system.
– We are made of elements produced in the nuclear fusion
within the cores of stars.
