ASTR 1102 Lecture : Lecture20
Document Summary
Open clusters h and x persei image credit: n. a. sharp/noao/aura/nsf. Turnoff" tells us age h and persei n. a. sharp/noao/aura/nsf. Older clusters are missing more massive stars. Turnoff" tells us age h and x persei n. a. sharp/noao/aura/nsf. Some helium burning stars ( horizontal branch stars") Up to 1,000,000 stars in less than 100 lightyear diameter. The other difference between open and globular clusters. 1% metals ( other stuff" - carbon, nitrogen, oxygen, etc) Universe began with just hydrogen and helium - no metals. These were formed by fusion in stars. Old stars have less metals: lower metallicity". Young, metal rich stars - e. g. the sun, open clusters. Old, metal poor stars - e. g. globular clusters. Eclipsing binaries are dim when one star eclipses the other (e. g. algol) Eta carinae became brighter during eruption in. Brightness varies by factor 100 over 332 days! Mira is red giant, pulsating in an out - a long period variable .
