Flashcards in Space Deck (33):
What is a light year?
The distance that light travels in 1 year (9.26 x 10^12)
What is an astronomical unit?
The distance from the Earth to the sun (1.5 x 10^8)
Which direction does the Earth rotate?
West to East
What are the 4 reasons that Earth is so perfect for life?
1. Distance - not too hot, not too cold
2. Magnetic field (magnetosphere) - stops solar wind from stripping atmosphere
3. Tilt - heat is distributed regularly over Earth
4. Atmosphere - traps heat from sun to create new greenhouse effect
How old is the milky way?
8-9 billion years
How long did it take for H and He to form?
377 000 years (after temperature cooled)
How hot was it, during the Big Bang?
10 billion K
How old is the universe believed to be? How do we know?
12.7 billion years old, and we know the rate of expansion
How do we know the universe is expanding?
1. Galaxies appear to be moving away from us (Doppler effect)
2. Remnant cosmic microwave background = radiation left over from the big bang, used to be gamma rays, now is microwave
How can we tell the latitude?
Fist = 10 degrees
Telephone = 20
Three fingers = 5
Pinky = 1
What are nebulas?
Star-forming clouds of dust (irregular grains or carbon & silicon) and gas
What is a protoplanetary disk?
Disk of gas & planetismals, forms along equatorial region
What is the nearest star forming region?
The Arion Nebula
How was our solar system formed?
1. Gravity pulls clouds of dust t/g
2. H begin gathering, as they become more concentrated = protostar
3. Powered by nuclear energy, they push aside the dust of their cocoons
4. Surrounding these new stars are left over material
5. Gravity + rotation causes dust to form flat disks which will eventually form planets
How are stars made?
- cloud of hydrogen gas
- balls of gas formed
- balls of gas expanded
How do stars die?
- stars run out of hydrogen fuel
- star cools, shrinks, collapses under weight
- star crashes inward and explodes!
- supernova creates new worlds
What is a lunar eclipse?
When the full moon passes into Earth's shadow. You can see it anyway & it is safe to watch
What is a solar eclipse?
When the shadow of the new moon falls on Earth's surface. You must be in a specific place but not safe to watch
Why don't we have a lunar eclipse every full moon?
The orbit of the moon is tilted 5 degrees to Earth's orbit about the sun. The full moon usually passes above or below Earth's shadow
On the equinoxes, all places on Earth experience equal hours because __________
During those dates, the earth is not tilted towards or away from the sun
What is the oort cloud?
Sphere of small, icy debris at the farthest reaches of the sun's gravitational pull
How are tides caused?
By the difference between the force of gravity on 1 side of the Earth nearest the moon and the side farthest
What are the 3 pieces of evidence supporting the solar nebula theory?
1. Cratered surfaces of moon +mercury (pounding of nebula?)
2. Planets revolve around sun in 1 direction (nebula spins in 1 direction)
3. LOTS of planets (planets are by-products of stars)
What is the nuclear fusion process?
1. Nuclear fusion starts when star gets hot enough (you need it to be highly pressurized)
2. Hydrogen nuclei combine to form helium nuclei
3. Protostar begins to consume fuel (core heats up which increases pressure)
4. Pressure and gravity balance out, creating a star!
5. Star continues to fuse H and He, so core grows bigger and bigger
What are sunspots?
Area of strong magnetic field on photosphere
What are solar flares?
Complex groups of sunspots. Causes solar wind
What is solar wind?
Explosively ejected streams of charged particles into space
How is the Auroras an example of solar wind?
Auroras result when solar wind are carried past Earth's magnetic field, generating electric currents that flow towards poles
How are galaxies formed?
1. Bodies of gas, dust, and protostars collide
2. Begin rotating around center of mass
3. Rotation contracts cloud to form a disk
Does a star's apparent brightness depend on just it's distance from Earth?
No, a star's brightness also depends on it's luminosity; a bright star is not necessarily closer to Earth.
List 4 properties of stars
Brightness, colour, temperature, composition
What is the fate of our Sun?
To become a red giant and explode in a supernova