Astronomy Flashcards
Solar System definition
Everything that orbits the Sun
Planet definition
Large objects that orbit a star
Solar system planets in order
Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune
Dwarf planet definition
Objects that orbit the Sun but not big enough to be a planet
Moon definition
Objects that orbit a planet in almost-circular orbits
Type of natural satellite
Artificial satellite definition
Man-made objects that orbit planets in fairly circular orbits
Asteroid definition
Lumps of rock and metal that orbit the Sun
Usually found in asteroid belt
Comet definition
Lumps of ice and dust that orbit the Sun in highly-elliptical orbits
Centripetal force definition
Force needed to keep something moving in a circle
How something keeps its orbit
Object moves in one direction
Centripetal force attempts to drag objects towards centre of planet
Object instead changes direction as it is already moving in one direction (instantaneous velocity)
This keeps it moving in its orbit
Factors of gravitational field strength
Mass of object creating field
Distance from centre of object creating field
What orbit’s distance from centre of planet means
Closer to planet, stronger the gravity so stronger centripetal force
Faster the object has to move to keep moving in stable orbit
Geocentric model
Earth is centre of Solar System
Everything orbited the Earth in perfect circles
There were no telescopes and saw just the Sun and Moon moving across the sky in same way
Accepted model since Ancient Greeks to 1500s
Heliocentric model
Earth and other planets orbited the Sun in perfect circles
Galileo saw “stars” (moons) following Jupiter instead of orbiting the Earth through his telescope
Current model of Solar System
Similar to heliocentric model (planets orbited Sun)
Planets orbited Sun elliptically
Sun isn’t centre of the universe
Steady State theory
Universe has no beginning or end
As Universe expands, new matter is created
Density of the Universe stays the same
Big Bang theory
All matter initially occupied a very small space Tiny space was very hot and dense It “exploded” and rapidly expanded No new matter is being created Universe has a finite age
How red-shift proved Universe’s expansion
Different elements absorb different wavelengths of light
Elements produce specific patterns of dark lines of frequencies it absorbs in visible light spectrum
Light at other galaxies produces same patterns but shifted towards lower frequencies (red side)
Further the galaxy = greater the red-shift
CMB radiation definition
Low frequency electromagnetic radiation coming from all parts of the Universe
How CMB radiation proved Big Bang theory
CMB radiation shows there is a beginning of the Universe
Supports Big Bang theory
How stars are born
Clouds of dust and gas (nebula) come together due to gravity to form protostar
Temperature rises as star gets denser and more particles collide with each other
When hot enough, hydrogen nuclei undergo nuclear fusion to form helium nuclei
Huge amounts of energy are given out, keeping core hot
Star is born
Main sequence star
Long stable period (several billion years)
Outward pressure from thermal expansion balances force of gravity
Heavier the star, shorter its time on main sequence
Red (super)giant
Hydrogen in core runs out
Force of gravity becomes greater than outward force from expansion
Star is compressed so it is dense and hot enough so energy creates makes outer layers of star expand
Becomes red because the surface cools
Small star = red giant
Big star = red supergiant
White dwarf
Small/medium size stars (from red giant phase) become unstable and eject outer layers of dust and gas
Hot, dense solid core is left behind
Supernova
Big stars (from red giant phase) flow brightly again as fusion of heavier elements takes place
They expand and contract multiple times as balance between gravity and thermal expansion shifts
Eventually explode in a supernova
After a supernova
Supernova throws outer layers of dust and gas into space
Leaves very dense core (neutron star)
If star was massive enough, it will collapse and become a black hole
How optical telescopes work
Uses reflection and refraction to help see distant objects clearly
How to improve image quality of optical telescopes
Increase aperture (diameter) of objective lens Use a higher quality objective lens
Best conditions for telescopes
Light pollution makes it difficult to see dim objects
Earth’s atmosphere and air pollution reflect and absorb light from space
Best view from earth is on top of a mountain in dark place
Best view is in space above Earth’s atmosphere
What X-ray telescopes see
Violent, high-temperature events in space e.g. supernovas
What radio telescopes see
CMB radiation
Improvements of telescopes
Computers help create clearer and sharper images and make it easy to capture images
Computers can collect huge amounts of data without human work and analyse them quicker
Bigger telescopes give better resolution and gather more light, so fainter objects can be detected
Also improved magnification so can see deeper into space
