astronomy Flashcards
What are some features of artificial satellites
They are man made
They are used for communication
They are used for weather forecasting, GPS, military surveillance and scientific research
They are orbiting telescopes
What are the three types of orbits of satellites
Geostationary orbit
Polar orbit
Low earth orbit
Explain geostationary orbit
Have an altitude of 35,786km above earth
Takes 24hrs for one orbit
The satellite appears stationary above one location on earth
Uses: Communication satellites, TV broadcasting, weather monitoring
Explain low earth orbit satellites
Altitude: From 200-2000km
Time for one orbit: 90minutes
Uses: Spy satellites, hubble space telescopes, ISS (international Space station)
Explain polar orbit satellites
They are a type of low earth orbit
Takes 90-120 min to complete orbit
Passes over the earths poles
Uses: mapping weather satellites, military surface
What are some examples of satellites
Hubble space telescope
GPS satellites
ISS (international space station)
Satellites stay in orbit it due to the balance of what two forces
Gravity
Centripetal force
What are dangers/limitations of satellites
Space Junk
high costs
limited lifespan
Re-entry hazards (fall back to earth and damage it)
What is an elliptical orbit, give an example
An orbit that isn’t a perfect circle, like the planets around the sun
Which two planets are the aestroid belt found between
Mars and Jupiter
What is an orbit
The curved path of one celestial object or spacecraft around another celestial object
What would happen if the moon was closer to the earth
It would experience a greater gravitational force towards the earth and eventually be sucked in
To avoid this, the moon needs to increase its speed so that a stable orbit is maintained
What is the correlation between the size of the orbit and the speed of the object
The smaller the objects orbit, the faster the object travels to maintain the orbit instead of collapsing in
What does red shift prove
That the space between us and distant galaxies is expanding, and proves the universe expanding
What is the big bang theory
All the matter in the universe occupied a really tiny space which was very hot and dense then it exploded and the universe started expanding
What is CMBR
the cosmic microwave background radiation from the big bang.
Over time as the universe has expanded and cooled the radiation has dropped in frequency
What is the steady state theory
It suggested that the universe has always existed and is expanding. The theory states that new galaxies formed in the spaces where older ones have moved apart
What is red shift
Where light from distant galaxies appear more red because the wavelength of light is stretched making it longer and shifting it towards the red end of the spectrum
What are the life cycles of stars like our sun
nebula
protostar
main sequence star
red giant
cloud of gas
white dwarf
What are the life cycles of stars bigger than our sun
nebula
protostar
main sequence star
red supergiant
supernova
either a neutron star or black hole
What is a nebula and what happens to it over time
A big cloud of dust and gas
Overtime the attractive force of gravity pulls the dust and gas together (collapses inwards to form a protostar)
What happens in protostar
As more and more particles collide and join the protostar it gets bigger and so its force of gravity gets even stronger attracting more dust and gas. The gravity squeezes the protostar making it more dense (particles collide more often), temp is raised.
Once temp and pressure is high enough, hydrogen nuclei start to fuse to form helium nuclei (nuclear fusion).
What happens in main sequence star
The outward pressure caused by nuclear fusion is perfectly balanced by the inward pressure caused by gravity.
This causes a long stable period that can last for billions of years.
The star will start to run out of hydrogen at one point (so fusion can no longer happen)
so the inward pressure of gravity takes over and contracts the star into a small ball, getting denser until it can start fusion again
What happens in a red giant
The red giant becomes unstable and expels its outer layer of gas and becomes a white dwarf
what happens in a white dwarf
It’s hot, dense and has a solid core, overtime the white dwarf gets cooler and darker until it emits all its energy and transitions to a black dwarf as it no longer has energy to emit light and so is dark
what happens in a red supergiant
They undergo more nuclear fusion and shine brightly
Then they explode into a supernova
what happens in a supernova
Forms elements heavier than iron that get ejected all across the universe.
If the star was very big it will condense into a very dense core called a neutron star
If the star was absolutely massive it would collapse in on itself causing a black hole
why do we call them black holes
They are so dense that their gravity can pull in any light that pass by
What are the advantages of naked eye astronomy
Low cost
can be conducted anywhere
What are the disadvantages of naked eye astronomy
cannot detect faint lights
depends on weather
What are advantages of space telescopes
can observe faint lights from distant stars and galaxies
unaffected by atmospheric distortion
Can detect all wavelengths of electromagnetic radiation
What are disadvantages of space telescopes
expensive to build
challenging to repair one in space
