Transcript High Energy Observational Astrophysics

High Energy Observational
Astrophysics
High Energy Observational
Astrophysics
1 Processes that emit X-rays and Gamma rays
High Energy Observational
Astrophysics
2 Sources: ????
High Energy Observational
Astrophysics
3 Problems with Earth based observation
High Energy Observational
Astrophysics
4 Early attempts to measure X-ray and gamma ray spectra
High Energy Observational
Astrophysics
5 Interactions of photons with matter: ????
High Energy Observational
Astrophysics
6 Different kinds of detector: ????
High Energy Observational
Astrophysics
7 Imaging detectors to record path
High Energy Observational
Astrophysics
8 Satellite observatories
High Energy Observational
Astrophysics
9 Neutrinos: sources, interactions, detectors
High Energy Observational
Astrophysics
10 Gravitational waves
High Energy Observational
Astrophysics
11 Cosmic Ray Particles
1) What is black body emission?
E avge 
3
k BT
2
E photon  h f 
ch

 max T  2.898  10 3
X-rays and gamma rays
X-rays from about 0.12 keV to 12 keV are “soft” X-rays
X-rays from about 12 keV to 120 keV are classified as "hard" X-rays
Gamma rays range from about 120 keV to 30 MeV
Thermal Bremsttralung
A charged particle undergoing an acceleration radiates photons.
Bremsstrahlung radiation is emitted by a charged particle accelerating
under the influence of another charged particle, losing kinetic energy.
Rate of acceleration determines wavelength of radiation produced.
Greater acceleration produces smaller wavelength emission.
In hot plasma at temperature T the free
electrons are constantly producing
Bremsstrahlung radiation during interactions
with the ions.
Synchrotron radiation
Similar to Bremsstrahlung radiation, but charged particles are
accelerated (either in a straight line or around a circle) whereas in the
latter they deflect from other charged particles (usually ions).
Most common example: electrons in a magnetic
field spiral around the field lines emitting radiation.
The frequency of the radiation depends on the
strength of the field and the component of the
electrons motion perpendicular to it.
Who are the usual suspects?
Type II Supernovae
Emit around 1046 joules (more than the
Sun will emit in its entire lifetime)
If a main sequence star has a mass of over 8
times the mass of the Sun it is destined to be
a type II supernova
Nuclear fusion continues until Fe at centre, stops, star collapses
increasing temperature and pressure.
As the density rises protons and electrons collide to form neutrons and a
vast number of neutrinos.

p  e  n  e
Eventually a neutron star is formed if the core is less than three solar
masses. More than this and a black hole forms.
Nucleosynthesis occurs in core and advancing shockwave. H emission lines
are also produced by advancing shockwave.