Lecture 20 - Supernovae & the “3-Phase” Model of the ISM Flashcards
1
Q
Name the four phases of the SNRs
A
- Early Free Expansion Phase (ends when M_swept approx M_enect)
- Sedov-Taylor Phase (Ends after about 4.2E4 yr)
- Post Sedov or Radiative Phase
- Fade away phase
2
Q
What’s the ejecta velocity in the early phase?
A
Close to 10 000 km/s
3
Q
What’s the ejecta velocity in the Sedov-Taylor phase?
A
200 km/s
4
Q
When does the SNR fade away?
A
When the expansion velocity is approximately equal to the velocity dispersion in the ambient gas
5
Q
How often do supernovae occur in the Milky Way?
A
About every 50 years
6
Q
Why do we need a 3 phase model?
A
Because supernovae tend to overlap
7
Q
What are the three phases in the 3 phase model?
A
Cold HI clouds, Warm cloud envelopes, and hot ionized medium
