Chapter 9 Flashcards
What happens to the Iron core?
It catastrophically collapses in a few seconds and heats up
Envelope is blown off at high speed
Brightens by a factor of 10^8 in a few days
Cools and fades as it expands over a few months
What happens to the surface of the newly formed supernovae?
Hot surface is expanding at 0.1c
Fades more slowly around 100 days
total light output over time is 10^44J
What is the GPE released during core collapse sufficient enough for?
To both power the mechanical and radiation output of a SN
How is energy transferred?
By the neutrinos that are released during the formation of the neutron star. For every proton/electron/neutron reaction, a neutrino is produced (typically in total 10^57 neutrinos)
Neutrinos don’t normally react with matter, so why do they during an SN?
Due to the sheer number and high densities involved
Do supergiants explode?
yes as shown by models
What does the ejected envelope from a supernovae form?
A supernova remnant (SNR)
What is ofter seen in an SNR?
Rapidly spinning neutron stars (pulsar)
How are increasingly heavier elements formed?
Through the r-process
Which process occurs in AGB stars?
“slowly” moving neutrons arising from 13C decay can synthesize new elements in the “s-process”
What is the result of neutron stars rotating fast?
PULSARS: strong magnetic fields produce relativistic jets of charged particles which cause periodic signals in radio, x-ray and even optical light
Period:millisecond to seconds
(often at centre of supernovae remnants)
When does a black hole form?
For the most massive stars even degenerate neutron pressure cannot hold up the stellar remnant (if M > 3M)
No known force can hold up the star against gravity
How can we find black holes?
BHs in binary systems where a a visible star orbits an invisible companion which is too massive to be a neutron starWe can estimate the mass of the optically visible star from its spectral type and then determine the mass of the companion.
What do isolated BHs contribute to?
Dark matter but this is difficult to prove
Gravitational lensing by MACHOS is used
What is the mass limit of a blackhole?
If M»_space; 3Mo then it is a blackhole
mass lower limit to true mass but if eclipsing binary then i is 90 degrees
