Module 5 part 3 astrophysics Flashcards
planet def and 3 characteristics
A body that orbits around a star, in our case, the Sun.
- mass large enough for its grav to give round shape
- no fusion reactions
- cleared its orbit of most objects
comet
Concentrated clusters of ice and dust that orbit star in elliptical orbit
planetary satellite
Bodies that orbit a planet. The gravitational force of the
planet’s mass provides the centripetal force of rotation.
solar system
A collection of planets that orbit a common star.
galaxy
Collections of billions of stars, planets, gases and dust, held together by
gravitational attraction
universe
The name given to all space and matter
difference between comet and astroid
- comets have ice while astroids do not
- not all comets orbit star
atroid
objects which are too small and uneven in shape to be planets, with a near circular orbit around the sun/star
Dwarf planets
planets where the orbit has not been cleared of other objects
formation of star
- gravitational attraction pulls gas and dust particles, forming clouds
- gravitational collapse accelerates, regions become denser
- gravitational energy converted to thermal
- protostar forms in cloud, very hot very dense sphere
- high temp and pressure allow hydrogen nuclei to overcome elctrostatic repulsion between nuclei and undergo nuclear fusion
- helium nuclei produced and star created
nebulae
A cloud of dust and gas in space, often hundreds of times larger then our solar system
star life and equilibrium
star remains in stable equilibrium with constant size.
radiation pressure (from photons emitted in fusion) and gas pressure (from nuclei in core) balance gravitational force compressing star. This is known as a main sequence
evolution of low mass star
- low - 0.5M☉ to 10M☉ core mass
- hydrogen supply decreases
- gravitational force overcomes gas and radiation pressure
- star collapses inward, becomes red giant
- helium fusion stops in core continues in outer shell
- helium low, evolves into white dwarf
- outer shell drifts off becomes planetary nebula
ADD MODE
low and high mass star core mass
low - 0.5M☉ to 10M☉
high - above 10M☉
smaller remain in main sequence longer
characteristics of white dwarf
- very dense
- temp of around 3000K
- no fusion, will eventually die
how does fusion in core of star prevent gravitaitonal collapse
photons emitted from fusion create outward radiation pressure. gas pressure from nuclei also causes outward force, balancing the forces
what is electron degeneracy pressure and found where
when electrons are squeezed together, but cannot exist in same energy state. results in pressure. Found in white dwarf
chandrasekhar limit
if white dwarf core mass below 1.44M☉, white dwarf is stable. If above, degeneration of electrons cannot balance gravitational force, it will collapse
evolution of massive starM☉
- high - above 10M☉
- temp high enough for helium fusion to heavier elements
- red supergiant forms with layers of increasing heavy elements, with iron core (cannot fuse further)
- iron core unstable, type 2 supernova occurs (implosion)
- if remaining core above 1.44M☉, electrons and protons combine, forming neutron star
- if core greater than 3M☉, gravitational force so strong escape velocity of core greater than speed of light, black hole is formed
characteristics of neutron star
- almost entirely made of neutrons
- just 10km in diameter
- around 2M☉
characteristics of black hole
- No light can escape gravitational field
- mass greater than 3M☉
- greatest density in the universe
solar mass def
1.99 x 10^30kg, mass of the sun
why are energy level of electrons neg
external energy is required to remove electron from atom. Neg values indiciate electron trapped within pos nuclei
what is most neg energy level known as
ground state
what happens when electron moves energy level
high to lower - energy conserved, electron makes transition with photon emitted (de excitation)
lower to higher - external energy required (e.g. electric field) results in excitation
how are emission line spectra formed
- elements in gas cloud with energy levels, electron de excited, releases photon (specific wavelength)
- wavelengths of light produced for each element different (Different energy levels)
- white light from star placed in diffraction grating, wavelengths seperate, producing emission line spectra
how is absorption line spectra formed
- light from source producing continuous spectrum passes through cooler gas
- photons absorbed by gas, raising electron energy level exciting the atom
- photons with energy equal to difference in energy between levels absorbed
- goes through diffraction grating, creates dark lines on spectrum
