Fifth Test Flashcards Preview

Astronomy > Fifth Test > Flashcards

Flashcards in Fifth Test Deck (11)
Loading flashcards...
1

33- a) Draw an H-R diagram, showing the major domains where stars are found. Label the axes as completely as you can.

a) Draw the curve of stellar heat vs stellar brightness, I think, and the L->R line going down. Draw the white dwarfs down below and the "red giants" up above. Brigher (lower) abs mag on Y going up, going right on X from cooler to hotter.

2

34- a) Who discovered the temperature sequence of the Draper spectral types, and at what University?

a) Annie Cannon at Harvard.

3

34b) Who discovered the period-luminosity relationship for Cepheid variable stars, and in what decade?

b) Henrietta Leavitt in 1900s or 1910s- GET THIS

4

35- a) Use a diagram and a few sentences to describe the basic method of constructing a mathematical stellar model. (Assume no rotation so that it is spherically symmetric.)

a) Divide star into concentric circles. observe spectral properties of outermost layer (chromosphere). assuming perfectly spherical, same all throughout layer. Use laws of physics to calculate properties for each layer going down. Properties are: temperature, density, pressure, composition, with 1 2 etc subscripts.

5

36- a) Draw an H-R diagram showing the early evolutionary tracks of 1/10, 1 and 100 solar mass stars. Label the axes as completely as you can.

a) Start near red giants, curve downleft, then just left over two main sequence.

6

36b) Label the 3 major stages on the diagram, and state in a sentence for each why the track moves (or does not move) in the direction it does.

b) 1. Temperature stays the same as cloud shrinks, convection moves heat around. Brightness shrinks as cloud gets smaller+no less hot.
2. Further shrinking of cloud (increased density) results in end of convection, thus heating up. Brightness stays roughly the same as shrinking+more heat balance out.
3. cloud of gas gets hot+pressure enough and ignites, joining the main sequence of stars.

7

38- a) Draw diagrams showing the main sequences of young and old star clusters.

a) Old star clusters: main sequence huge at low T low M bottom right. curves up towards giants suddenly.
Young star clusters: more concentrated at top, higher mass stars have not yet died, lower mass have not yet formed!

8

39- Discuss white dwarf stars.
a) In what decade was the first one discovered, in what decade was it found to be unusual, what is its name, and why was it thought to be unusual?

a) The first white dwarf star to be discovered was Sirius B, discovered in 1862, found to be unusual from spectral diagram in 1915, unusual because it was hugely massive but small: way too dense to be real.

9

39b) What was the stability problem, who explained it and in what decade?

b) The density problem stated that white dwarfs such as Sirius B should not be stable, as they were so dense that they should collapse under their own gravity. It was solved by S. Chandrasekar in 1930.

10

40- a) Discuss pulsars. Who discovered the first one, when, using what kind of instrument, and what was he or she trying to do?

a) Jocelyn Bell discovered the first pulsar in 1967, using radio antennas she set up in a field. She was trying to see scintillating (random twinkling) quasars.

11

40b) Draw a diagram illustrating what we think a pulsar is. Be sure to label all the important parts of the diagram.

b) Parts of pulsar: neutron star, axis of rotation, magnetic axis slightly off, atmosphere of p+ and e-, jet coming from magnetic axis, strong magnetic field.