If the star is relatively low mass, roughly M<25M⊙, it can be supported by neutron degeneracy and becomes a neutron star.
For more massive stars, the gravitational attraction overcomes neutron degeneracy, and the core collapses to form a black hole.
Supernovae remnants (SNR) can take different forms and evolve with time:
The central ring is due to ejection by a stellar wind prior to the explosion.
Lies in the plane that contains the centre of explosion:
- Glows due to [OIII] emission, excited by radiation from the explosion.
- When the shock wave from the explosion reached this ring, in 2004, it excited the gas causing it to glow brightly.
The two other rings are not in the plane of the explosion, but in front of and behind the star. The explanation of these rings is still unknown.
X-ray image of the Cassiopeia A supernova remnant. Different colors represent X-ray emission at different wavelengths which are caused by emission lines of different elements
X-ray image of the Cassiopeia A supernova remnant. Different colors represent X-ray emission at different wavelengths which are caused by emission lines of different elements
Very old (10,000s years) supernova remnants fade back into interstellar space enriching it with heavier elements
Cygnus loop: this is a ~15,000 year old remnant.
The filaments are caused by shocks encountering the interstellar medium. These shocks excite the gas which then emits emission lines.
Center filled or Crab-like SNR, or pulsar wind nebulae:
The Crab nebula is ~2 kpc away, with an angular size of 4×2 arcminutes.
The expansion velocity is measured from the Doppler shift to be 1450 km/s.
The source of the luminosity and electrons is a pulsar in the centre of the nebula.
Exercise: estimate the age of the nebula. How bright would the supernova that gave rise to the Crab nebula have been?
Plerionic composite: shell-type on the outside, Crab-like at the center.
2. Absorption and scattering processes – Part I
3. Absorption and scattering processes – Part II
4. Emission processes – Part I
5. Emission processes – Part II
6. Instruments for X-ray and γ-ray Astrophysics – Part I
7. Instruments for X-ray and γ-ray Astrophysics – Part II
8. X-rays from the solar system
9. X-rays from low-mass and PMS stars
12. Evolution of Shell-type Supernova remnants
13. X-ray binaries
14. X-ray emission in normal galaxies
15. Active Galactic Nuclei – part I
16. Active Galactic Nuclei – Part II
17. Active Galactic Nuclei – Part III
18. Clusters of Galaxies – Part I