1. Astronomy 101 Planetarium Lab Instructor: Brian Pohl ConOps: Craig Zdanowicz www.physics.unc.edu/~bpohl/ YOU MAY SIT WHERE YOU WISH (except for the front row and the south section)

2. Administrative Stuff • This is the last required lab • Due next Wednesday (Apr .1st), no foolin! • Next lab is the Make-up Lab (optional) • 2 weeks hence: ( Apr. 13th, 14th ) • I will have my last office hours on Monday and Tuesday Apr. 20th and 21st (see last slide for details) • Makeup lab due Wednesday Apr. 22nd • Evaluations at end of lab today

3. Measurement in Astronomy

4. Angles in the Sky & Time

5. Size of the Earth & Location on the Earth

6. Motions of the Planets

7. Night Lab Measurements • Coordinates and the Motion of Stars, quantitatively • Relative brightness of the stars • Size of planets • Structure of the surface of the Moon • The Spectrum of Hydrogen • Perhaps the Doppler shift, again from the Spectrum • Possibly the physics of craters and meteors

8. Variable Brightness

9. May I present the Zeiss show!!

10. Intrinsic variables • Changes in brightness caused by physical changes inside stars themselves • Two types • Pulsating (what we’ll deal with today) • Eruptive

11. Pulsating stars Expansion and contraction of surface Pressure and gravity are not in equilibrium Smooth change in light curve Note: The smaller a single star is physically, the brighter

16. Extrinsic variables • Changes in brightness are apparent • Two types • Eclipsing binaries (what we’ll deal with today) • Rotating stars • Eclipsing binary • Changes in brightness caused from eclipses of two stars as they orbit each other

17. Primary eclipse happens when hottest star goes behind Note: a higher mass star is smaller in size

19. Magnitude Magnitude system - use certain stars as brightness standards a higher magnitude is a fainter object Apparent magnitude - measure of how bright a star appears at earth, regardless of distance Absolute magnitude - apparent magnitude it would have if star were placed at distance of 10 parsecs Bright Less Bright Dim Dimmer Dimmest 1 2 3 4 5

20. Lab Write Up • No percent errors • Still need 2 sources of error! • “Skill” of mag. Meas. • Only rewrite data or calculations if neatness is an issue • Graphs - label period, axes, connect points • Make sure magnitude goes in correct direction! • Answer questions on pages 59&60 • Incorporate these into your conclusion section

21. Some physical considerations • What are we trying to measure? • Magnitudes? Yes • But! The physical cause of the variability is the MOST important thing we are trying to measure • What interferes with our ability to determine the physical cause of the variability??

22. All Power Points are on my website:http://www.physics.unc.edu/~bpohl Visit office hours or email me if you have questions! bpohl@physics.unc.edu Morehead room 403 Monday (week-after-lab) 3:00pm-5:00pm Tuesday (week-after-lab) 5:00pm – 7:00pm

23. Evaluations • Please turn in evaluations to Craig • You are evaluating the planetarium portion of the lab. Night labs evaluated separately • Comments are appreciated, Please be constructive • Something I did well • Something that needs improvement