Astrophysics Terminology HL Flashcards
Jean’s mass
method to discover if an interstellar cloud of gas in space will collapse and form stars.
If the mass of the cloud is > Jean’s mass – will collapse and form a star
If the mass of the cloud is < Jean’s mass – will not collapse or form a star
how does nuclear fusion work for stars like the sun? Describe the stages through chemical equations
proton-proton chain.
1) hydrogen-1 + hydrogen-1 –> hydrogen-2 + positron+neutrino
2) hydrogen-1 + hydrogen-2 –> helium-3 + gamma-ray photon
3) helium-3 + helium-3 –> helium-4 + hydrogen-1 + hydrogen-1
how does nuclear fusion work for bigger stars? Describe the stages through chemical equations
CNO process
1) hydrogen-1 + carbon-12 –> nitrogen-13 + gamma ray photon
2) nitrogen-13 –> carbon-13 + positron + neutrino
3) hydrogen-1 + carbon-13 –> nitrogen-14 + gamma ray photon
4) nitrogen-14 + hydrogen-1 –> oxygen-15 + gamma ray photon
5) oxygen-15 –> nitrogen-15 + positron + neutrino
6) hydrogen-1 + nitrogen-15 –> carbon-12 + helium-4
what is the nuclear fusion that occurs after the main sequence
1) helium-4 + helium-4 –> beryllium-8
2) helium-4 + beryllium-8 –> carbon-12
3) helium-4 + carbon-12 –> oxygen-16
nucleosynthesis
production of different nuclides by fusion
s-process
slow neutron capture to create heavy nuclides, has time to decay before capturing a neutron
r-process
rapid neutron capture to create heavy isotopes
supernovae
events in space that often appear as extremely bright stars
type 1 supernovae
event when material from a star falls into a white dwarf. A white dwarf gains too much mass from a red giant star in a binary star system – collapsing and exploding. New generations of stars may form afterward. Utilized as a standard candle since it always has the same peak of luminosity. Luminosity is brighter than type 2 but falls sharply. Does not have hydrogen lines in their spectra
type 2 supernovae
event when massive stars reach the end of their life cycle. A star’s core collapses due to gravity when it reaches critical mass (Chandrasekhar limit) and implodes producing neutrons and neutrinos. This produces a shock wave causing the explosion of a supernova. Not used as a standard candle since it has different peaks of luminosity. Luminosity is less than type 1 but falls of gently. Has hydrogen lines in its spectra
cosmological principle
that the universe is homogeneous and isotropic (the same and uniform) — that it has no edge and no center
critical density
the density that determines the shape of the universe
density < critical density – universe is open and infinite
density > critical density – universe is closed and finite
density = critical density – universe is flat expanding at a decreasing rate
MACHOS
Massive compact halo objects – a nature of dark matter theory. Black holes and neutron stars produce dark matter which could be too distant for luminous objects to detect easily
WIMPS
weakly interacting massive particles – a nature of dark matter theory. Subatomic particles that interact weakly with ordinary matter, possibly making up dark matter
Neutrinos – a nature of dark matter theory
that neutrinos with very small masses contribute to dark matter
Dark matter
matter that does not interact with electromagnetic force. Does not absorb, reflect, or emit light.
Dark energy
the energy that causes the universe to expand at a faster rate than it did in the past
cosmic microwave background (CMB)
the cooled remnant of the first light that could ever travel freely throughout the Universe. Echo or shockwave of the Big Bang
What is the experimental evidence for dark matter?
Galaxies’ rotation curves stay flat even at far distances from their centers, suggesting the presence of unseen matter spread evenly throughout the galaxy.
What is the nature of anisotropies in cosmic microwave background radiation?
the small variations in temperature of CMB across the sky
What are the possible causes of anisotropies in cosmic microwave background radiation?
quantum fluctuations, dipole distortion due to the motion of the earth, density perturbations
