chapter 25: our galaxy physics of astronomy – week 6 – may 2006
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Chapter 25:Our Galaxy
Physics of Astronomy – week 6 – May 2006
RR Lyrae variables
Q: Why are they all about 100 Lsun?
A: Horizontal branch pulsators:
heating and compressing at roughly
constant luminosity (T↑ and R↓)
The winding dilemma – if star motion caused spiral arms, structures would disappear in just a few hundred million years
Galactic density wave causes traffic jams in interstellar medium
Black hole at the center of MW
Orbits of nearby stars show that SagA* has about 3.7 million Msun – very massive
X-ray flares detected by Chandra last only 10 minutes, indicating a size of only 1.2 AU – very compact
Looking ahead• Monday: no HW due, no presentations
• Tuesday: Bring your finished PowerPoint pages
• 3:00 workshop Tues: PowerPoint → Posters
• Thursday: bring everything to class - we’ll walk to the van together and leave at 3:00
• Summary: Maxwell’s equations → speed of light “greatest synthesis …more important than the civil war”
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