Space Flashcards
What is a galaxy
A cluster of stars and planets that are held together by gravity
What is a solar system
A sun and all of the objects that orbit that sun, like planets, and planetary satellites, comets and asteroids
Comet facts
They are like a dirty snowball
Have highly elliptical orbits
Some are very far away and take millions of years to complete one orbit
Other are closer and take less time like 76 years
How can you measure distances to near by stars
You can use parsecs, distance in parsecs is given by 1/parallax which is measured in arc seconds for earth 1/3600
Stellar evolution our sun
1 - nebula, cloud of dust left from super nova comes together from gravity
2 - has heats up and becomes dense called protostar
3 - temperature of protons star gets very hot at centre causing nuclear fusion to take place
4 - main sequence star is born where gas pressure and radiation force are equal to gravitational force making star stay same size until run out of hydrogen.
5 - fusion stops and so dose outward pressure, core collapses and outer layers cool and move away
6 - outer layer of core still has hydrogen and dose fusion
7 - core contracting causes enough heat for helium to fuse
8 - when this stops outer helium layer leaves and core heats more causing shell helium fusion
9 - this now causes outer layer to leave and become a planetary nebula and the core becomes a white dwarf
Stellar evolution end for more than 1.44 solar mass units
If bigger than Chandrasekhar limit then instead of red giant is a red super giant,
These have a shorter life as they burn through the hydrogen much faster than smaller stars
Then as bigger fusion continuse past helium making onoin like layers all the way up to iron if very big star.
When outer layers leave as too bid electron degeneracy pressure causes can’t stop core contracting and outer layers fall in and then rebound causing a super nova explosion leaving a neutron star or a black hole depending on its mass, if big enough black hole
Neutron star facts
Very dense
Very small
Spinning very fast
Spinning causes radio waves and we call them pulsars
Black hole facts
Infinitely dense
Emit hawking radiation
No fusion
Absobtion spectra
Cool gas removes sparts of spectrum from electrons getting exited and jumping up energy levels
Emission spectra
Exited gas electros fall back down energy levels emitting photons which accord to the fall in energy
What is luminosity
The radiant power of a star
Total energy it emits per second
Homogeneous
Every part of universe is same as other parts mass is spread uniformly
Isotropic
Universe looks the same in all directions on a large scale
Doppler effect
This shows red shift from all other stars which tells us every things is moving away from everything meaning the universe is expanding
Hubbles law shows that recessional velocity is directly proportional to distance si unit for hubbles contant is s^-1
Big bang model
The universe started off as a very hot and very dense singularity and has been expanding ever since
Before big bang there was no space and no time, space time began with the big bang, every thing is moving away from everything as space is expanding.
Evidence for the big bang model
- cosmic back ground radiation, gamma radiation produced in early universe has had wavelength stretched by red shift to be microwave radiation which can be seen all over space.
Tiny fluctuations in temperature show energy density variations in early universe which are needed to seed for stars to form
Background radiation known as doppler shift shows earths motion through space shows milky way is rushing though space at 1 million miles an hour towards an unknown mass
Evloution of universe
- 10 -46 infinatly hot and dense
• 10-43 no distinction between types of forces, one grand unified forces, the universe expands and cools the unified froce splits into graivty strong and weak nuclear force and electromagnetic forces
• Inflation happened at 10 - 34 seconds this is when the universe expanded very quickly, the universe is a sea of quarks, anti quarks leptons and photons all of this is separate due to there currently being to much energy
• 10-4 seconds temperature of 10^12 k quarks join to make particles, they will never exzist separately again anti matter and matter anhilate each other froming matter and a huge amount of photons, this is cosmic background radiation which is seen today
• 100 seconds , cooled to 10^9 k the universe was smimilar to interior of a star, photons are cool enough to fuse to form helium nucli
• 300,000 years temperature is now 3000k cool enough for electrons to combine with helium and hydrogen to make atoms the universe becomes transparent as no free chnages for photons to interact with this is called recombination
• Now 14 billions years 2.7k slight density fluctuations in the universe mean that very time clunos of matter have been condensed by graivty into galactic clusters and galaxy and individuals stars
