Astronomy 101 Planetarium Lab

1. Astronomy 101 Planetarium Lab Instructor: Brian Pohl ConOps: Craig Zdanowicz www.physics.unc.edu/~bpohl/

2. Administrative Stuff • This lab is due Wednesday, April 22nd • This is the make-up lab • Final office hours on Monday and Tuesday April 20th and 21st • Final grades • Night lab evaluations

3. What is a galaxy?

6. Hubble Tuning Fork Is this a trend in evolution?

11. Redshift - objects appear redder the faster they move away from you

12. Expansion of Universe • So all objects are moving away from us • Are we at the center of the universe? • Raisin bread model • Hubble constant - rate of recession/distance • The further away galaxies are, the faster they are receding • This means the universe is expanding exponentially!

13. How Fast is the Universe Expanding? (What is the Hubble Constant?) To figure this out, you need: • Distance • You find distance by comparing apparent magnitude (or luminosity) with absolute magnitude • Standard candle gives you absolute • Velocity • You find velocity by measuring redshift • Hubble Constant – Units of: (km/s) / (Mpc)

14. And may I now present the final star show of the season!!

15. Lab Procedure • Pg. 185, data sheet pg. 191 • Measure magnitude through ‘telescope’ • (column 1) • Enter galaxy type into (column 4) • Correct the magnitude for telescope • We want to find out: • Are more distant galaxies moving faster AWAY from us??

16. START NOW

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25. What to do with all this data?? • We measured: • Brightness (Mag) in simulated telescope • We calculate: • “Actual” brightness (Mag) in ‘real’ telescope • We know: • Absolute brightness (Mag) of galaxies • Recession velocity of galaxies • We can then determine: • The distance to the galaxies • What then? • Graph Distance vs. Recession Velocity • Slope of this graph is related to expansion of Universe • Hubble Constant!!

26. 2 graphs (Do not connect dots, use best fit) Magnitude (col 2) vs. velocity (col 7) Distance (col 8) vs. velocity (col 7) Find Distance from luminosity Use absolute magnitude (col 5) and apparent (col 3) to find distance modulus Use Figure 1 to find distance Note: x-axis is “Apparent MINUS Absolute Magnitude” Which graph is Hubble’s Law? Read pages 103-104 of lab manual Determine Hubble’s constant (also from page 103) Use slope (Do not connect the dots, use best fit) And percent error can look up value online [cite source]! Put calculations on clean sheet Include all equations, calculations, explanations (also for finding slope) As for error, we have been doing this all semester, here is your time to show me what you have learned!! Lab Write Up

27. All Power Points are on my website:http://www.physics.unc.edu/~bpohlVisit office hours or email me if you have questions! bpohl@physics.unc.edu Morehead room 403 East entrance facing the arboretum. Take elevator on the right to the fourth floor. Monday 4/20: 3:00pm-5:00pm Tuesday 4/21: 5:00pm-7:00pm