Lesson 1 Flashcards
Solar system
consists of the Sun, the planets and their moons, and countless smaller objects that include rocky asteroids and icy comets
Galaxy
a great island of stars in space, all held together by gravity and orbiting a common center
with a common mass equivalent to millions, billions or trillions of stars
Galaxy clusters
groups of galaxies with more large members
Local Group
Milky Way and more than 70 other smaller galaxies
Superclusters
gigantic region of space in which many groups and clusters of galaxies are packed more closely together than elsewhere in the universe
Universe
the sum total of all matter and energy, encompassing the superclusters and voids and everything within them
What unit of measurement is used with our solar system?
1 astronomical unit (AU) = 150 million Km (used for within our solar system)
What unit of measurement is used for distances between starts and galaxies?
1 light year (ly) = 10 trillion Km; distance that light can travel in 1 year (used for distance b/w stars and galaxies)
Star
large glowing ball of gas that generates heat and light through nuclear fusion in its core
Planet
1) orbits star
2) large enough for own gravity to make it round
3) has cleared most other objects from its orbital path
Dwarf planet
1) orbits star
2) large enough for own gravity to make it round
BUT HAS NOT:
3) cleared most other objects from its orbital path
Moon (satellite)
object that orbits a planet; satellite is just an object orbiting another object
Asteroid
small rocky object orbiting a star
Comet
small ice-rich object orbiting star
Small solar system body
asteroid, comet or other object that orbits a star but is too small to qualify as planet or dwarf planet
Star system
a star (or multiple stars) and any planets and other materials that orbit it
Observable universe
portion of entire universe that can be seen from Earth
avg. distance between Earth and sun & length of semi major axis of Earth’s orbit
1 AU or 150 million Km
Light year
distance light can travel in 1 year = 9.46 trillion Km
Rotation
spinning of an object around it’s axis
Orbit (revolution)
orbital motion of one object around another due to gravity
Expansion of the universe
increase in average distance between galaxies as time progresses
How “old” is the universe to us?
Earth 14billion years; distance of 14 billion ly marks the boundary of our observable universe This doesn’t mean that the entire universe is 14 billion years old; it’s just that anything further hasn’t had time to reach us yet
How long ago did our solar system and planet form?
~ 4.5 billion years ago
How long ago did dinosaurs die?
~65 million years ago
How long ago did hominids begin walking upright?
~ 60 million years ago
Describe earth’s rotation
West –> East
Rotates once each day about it’s axis at a speed of 1000km/hour
At what degree is Earth title?
23.5 degrees
How long does it take light from the moon and the sun to reach Earth?
- Moon to Earth: 1 second
- Sun to Earth: 8 minutes
How far away is the Andromeda galaxy?
2.5 million LY
Name the planets in our solar system from closest to furthest from the sun
- Mercury
- Venus
- Earth
- Mars
- Jupiter
- Saturn
- Uranus
- Neptune
What is the closest star to our solar system?
- Star system Alpha Centauri at 4.4 ly
Explain how a star is born
- gravity compresses material in a cloud to a point where the centre is dense enough and hot enough to generate energy by nuclear fusion
Supernovae
Massive star dying, blowing much of it’s content back out into space
Describe the cosmic calendar
- Compress 14 billion years onto a one year calendar
- January 1st: Big Bang
- February: Milky way formed
- Early September: our solar system and planet
- Late September: life on Earth
- Mid-December: recognizable animals
- Dec. 26th: dinosaurs
- Dec. 30: dinosaurs died
- Dec. 31st - 9pm: early hominids
- 30 seconds ago: human civilization (pyramids 11 seconds ago, galileo and kepler 1 second)
Dark matter
- matter that is invisible by our telescopes, most of the mass of the galaxy
Dark energy
- astronomers first recognized when discovered that expansion of universe is getting faster with time
Hubble’s Law
- every galaxy outside local group is moving away from us
- the more distant galaxy, the faster is moves away
- This is how we know old the universe is, by how fast other things are moving away
- Speed of recession of a galaxy is proportional to its distance from an observer
Doppler shifts
- measures speeds of galaxies by spreading light into spectra
Copernican revolution
- copernicus said sun is centre
What are the terrestrial planets and how far are each from the Sun in AU?
- Mercury (0.4 AU)
- Venus (0.7 AU)
- Earth (1 AU)
- Mars (1.5 AU)
- Terrestrial because made up of heavier materials; silicon and irons
What are the Jovian planets and how far are each from the Sun?
- Jupiter (5.2 AU)
- Saturn (9.6 AU)
- Uranus (19.2 AU)
- Neptube (30.1 AU)
- Made of gasses/ice; Jupiter and Saturn hydrogen and helium mostly; Uranus and Neptune (ice giants) water, ammonia and methane
- All have a small icy rocky core
Asteroid belt
- few million asteroids
- large volume of space, orbiting Sun
Keiper Belt
- Past Neptune
- ~30-50 AU
- Icy, containing Pluto
- 20x’s as wide and heavy as asteroid belt
Oort Cloud
- outer region
- small icy objects
- spherical shape
- trillions of objects 1km in size, and billions of slightly larger ones
Milky Way facts
- Milky way is spiral shaped
- We are 1.7 billion AU from centre in the Orion arm
- 6-10 billion AU wide, and 120 million AU is thickness of disk
Cosmology
scientific models of origin, evolution, and future of our universe
Big bang
- universe began from condensed point, expanded and cooled down
1) expansion and cooling
2) formation of atoms, clouds of atoms collapsed and form stars and planets
3) stellar nuclear fusion made heavier atoms
4) stars systems clustered together making galaxies
5) galaxies close together made local groups
6) larger clumps of galaxies = galaxy clusters
