lecture14

# lecture14 - Astronomy 3 The Nature of the Universe...

This preview shows pages 1–12. Sign up to view the full content.

Astronomy 3: The Nature of the Universe Professor Alice Shapley Lecture 14: Stellar Life Cycles (NGC 1499 Image credit: Markus Noller, Deep Sky Images)

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Logistics Quiz #7: due Monday, May 23rd, 10 pm. Available at CCLE website https://ccle.ucla.edu/course/view/11S-ASTR3-2 Structure and Motion of Spiral Galaxies.” Issue with lab #5 grading for people in Cory’s sections (2D and 2E). Please come see me or one of the other TAs.
Midterm #2 Results Exam graded out of 50 points. • Median score (i.e. halfway point): 39/50 (78%), mean=38.6 (77.2%). • Midterm scores and solutions posted on-line after class. Come to me with questions.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Midterm #2 Results 3 Hardest questions: We’ve talked about how many Suns could fit within the distance separating Earth and the Sun (i.e. within one astronomical unit). How many Earths could fit within 1 astronomical unit? a) ~10 b) ~100 c) ~1000 d) ~10,000 e) ~10 6 The radius of Earth is ~0.01 x the radius of the Sun.
Midterm #2 Results 3 Hardest questions: Which internal energy source produces heat by converting gravitational potential energy into thermal energy? a) accretion b) differentiation c) radioactivity d) both (a) and (b) e) all of the above

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Midterm #2 Results 3 Hardest questions: A sphere with a radius of 2 meters has a surface-area-to-volume that is times as large as the surface-area-to-volume of a sphere with a radius of 4 meters. a) 1 b) 2 c) 4 d) 1/2 e) 1/4 Recall: SA=4 π r 2 . V=(4/ 3) π r 3 . SA/V=3/r. So, SA/V(2)= 3/2, while SA/V(4)=3/4. So, SA/V for 2-meter radius sphere is twice as large as that for 4-meter radius sphere.
Review from Last Time Measurements of stars: Luminosity, flux, distance – Temperature Mass (use binary stars to weigh them!), masses range from 0.08 to ~100 times the mass of the Sun.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
1) Hotter objects emit more light at all wavelengths Stefan-Boltzmann Law: Luminosity per square meter = constant x T 4 2) Hotter objects emit light at shorter wavelengths (higher frequencies) Wien’s Law: T (K) = 2,900,000/ wavelength (nm) Laws of Thermal Radiation
Lines in a star’s spectrum correspond to a spectral type that reveals its temperature. Spectral type (letter/number) is shorthand for temperature. (Hottest) O B A F G K M (Coolest) STELLAR SPECTRA Hottest stars Coolest stars Letters (A-O) assigned over 100 years ago before temperatures were known. Had to be re-ordered to make sense. Still a useful aid to memory. Hottest stars: ~50,000 K Coolest stars: ~3,000 K

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Types of Binary Star Systems Visual Binary Eclipsing Binary Spectroscopic Binary NOTE : About half of all stars are in binary systems GRAVITATIONALLY BOUND STARS. • Two stars orbiting each other = BINARY. • Binary Stars yield Stellar Masses by Newton’s form of Kepler’s 3 rd Law. (Animation courtesy Richard Pogge, OSU)
Review from Last Time Measurements of stars: Luminosity, flux, distance – Temperature Mass (use binary stars to weigh them!), masses range from 0.08 to ~100 times the mass of the Sun.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern