AST-1002 Section 0459 Review for Final Exam

Please do not forget about doing the evaluation!

•Bring pencil #2 with eraser

•No use of calculator or any electronic device during the exam

• We provide the scantrons

• Formulas will be projected on the screen

•You can use the exam sheets as scrap paper if you need to do calculations .

• The exam will have 45 questions, 5 possible answers, only one valid answer.

•The exam is Thursday December 14th at 12:30 PM. Two hours are allocated for the

exam

•The exam is in this room, FLG-280

•Please do not be late. If you are late and arrive after the first person had turned in the

exam, you may not be allowed to take the exam..

• There is no time for make up exams after the scheduled time for the final. The exam has

to be graded and the final grades need to be entered during the weekend, right after the

exam.

Don’t forget to bring Gator One ID card

Exam will include material from chapters 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 14, 15 and

17 lectures ( All the material discussed in the Power Point presentation class).

Chapter 9– The Sun

• The two forces that balance in the interior of the Sun so it end up having an spherical shape

•Radius, mass of the Sun compared to Earth (radius ~100 , mass ~300,000)

•The main regions in the solar interior and atmosphere: Core, radiation zone, convection zone,

photosphere, chromosphere, transition zone, solar corona and solar wind

•Solar granulations: evidence of convection

•The solar wind: its composition and how fast it travels in the interplanetary space

•Sunspots, temperature of the sunspots, polarity of magnetic field

•Duration of the sunspot cycle. Duration of the solar cycle

•Polarity of sunspots in the north and south solar hemisphere

•Solar prominences, CME

•Solar flares. Effect of solar flares in the Earth and the Earth magnetic field

•Fusion of H into He in the core. The proton-proton chain.

•Conversion of “missing “ mass into energy. The E= mc² equation

•The neutrino problem

Questions

•What is the approximate rotational period of the Sun?

•What is the approximate mean density of the Sun (1410 kg/m³)?

•What is the approximate surface temperature of the Sun

•How do we determine the luminosity of the Sun (L=Flux* 4 π R²)?

•What is the temperature of the core of the Sun?

• What mechanism produce the energy in the core of the Sun?

•Minimum temperature needed to start fusing H into He

•What type of spectrum emits the Sun?

• How can we see the solar corona?

•How long does it take for the electromagnetic radiation to reach the Earth?

•How long does it take for the solar wind and particles ejected from the Sun to reach the Earth?

Chapter 10– Measuring the stars

Topics •Stellar parallax. Equation of stellar parallax: Distance (pc) = 1/parallax(arc sec).

•Definition of Parsec

•Stellar proper motion

•Luminosity, flux or apparent brightness of a star

•Equation of luminosity L=Flux* 4 π d² (here d is distance to the star)

•The apparent magnitude scale. Definition of absolute magnitude

•Stellar temperature and the spectrum of the stars

•The spectral classification: O, B, A, F, G, K, M . A sequence of stellar temperatures

•Direct and indirect way of determining a star radius. Steps to determine the radius R of a star in an indirect

way

•Determining the radius using radiation laws: R² = L/ T4 (in solar units)

•Understanding Stefan laws: radius and temperature dependence. Equation: L = 4R2T4

•The HR diagram. The parameters in the two axis in the HR diagram

•Locations of the main sequence in the HR diagram. Locations of red giants , blue giants and white dwarfs

•Determining the mass of stars in the case of binary stars

• The spectroscopic parallax

•The lifetime of a star: the mass /rate of energy production. Equation: Stellar lifetime 1 / Mass3

Chapter 10– Measuring the stars Questions

•What do we need to know to determine the distance to a star using the stellar parallax

•How can we determine the radial motion of a star?

•How can we determine the transverse motion of a star?

• The two axis in the HR diagram: Luminosity and temperature

•Where are the low and high temperature stars located in the HR diagram? Where are the low mass and high

mass located? Where are the high radius and low radius stars located in the HR diagram?

•The spectroscopic parallax.

• Steps to determine the distance R using spectroscopic parallax: Measure the flux, determine the surface

temperature (or spectral classification), use the HR diagram to determine the luminosity, use the equation

Flux = Luminosity/ 4d2

• How can you determine the luminosity L of a star (in solar units) respect to the Sun?

• Lstar= (Rstar/Rsun)2 * (Tstar/Tsun)

4 * Lsun

• How important is the mass of a star? Parameters of a star determined by the mass of a star: Luminosity,

radius, surface temperature, lifetime, evolutionary phases.

•A star of smaller mass lives a shorter or a longer life respect to a large mass star?

Chapter 12 and 13 – Stellar evolution, white dwarfs, neutron stars and black holes

Topics

• The balance of gravity and pressure forces: Hydrostatic equilibrium

•Minimum temperature to start the fusion process of converting H into He

•The structure of a star like the Sun

• The chemical element is left in the core (“ashes’) after is burn the helium in a star with the mass of the

Sun

•The structure of a star more massive than the Sun

• Star evolution in the HR diagram after they burn the hydrogen

• Important role of iron at the end of the life of a massive star

• The role of the electron degeneracy pressure and the neutron degeneracy pressure in massive stars.

• The final bodies resulting from the evolution of a star: white dwarf, neutron star and black hole.

• The final bodies from the evolution of a star of the mass of the Sun, from a mass >1.4 solar mass but <

3 solar mass, from a star > 3 solar mass

• The Schwarzschild radius and event horizon of a black hole

Chapter 12 and 13 – Stellar evolution, white dwarfs, neutron stars and black holes

Questions •How long will take for the Sun to convert all the H into He until all the H is used up?

•Temperature necessary to fuse He?

•Temperature necessary to fuse Carbon?

•How long will the Sun stay in the main sequence?

• At what point a star will move off the main sequence?

•To what region in the HR diagram will be Sun move once it has used all the H?

• When the Sun moves off the main sequence, does surface temperature increases or decreases? What

happens to the diameter ?

•Why the Sun cannot fuse carbon?

•What happens to the Sun once it use all the H and He and end up with a core of carbon?

•What is a planetary nebula?

•What is a white dwarf? What is the chemical element that compose a white dwarf?

•Why a star more massive than the Sun can fuse heavier elements such as carbon, oxygen, neon?

•What happens when a massive star try to fuse iron?

•What is the final object resulting from the collapse of a star of one solar mass? Final object of a star

with more than 1.4 solar masses but less than 3 solar masses? Final object for a star with more than 3

solar masses?

•Size of a white dwarf? Size of a neutron star? Size of a black hole?

•What basic principle can be applied to understand why a neutron star rotates fast? Why a neutron star

may have a strong magnetic field? What is a pulsar?

•What would happens to the Earth’s orbit if the Sun could collapse into a black hole?

•Why light emitted at the event horizon or inside the event horizon cannot escape a black hole?

•How it is possible to estimate the mass of the supermassive black hole in the center of the Milky Way?

Chapters 14-15 Milky Way, Hubble law and Dark matter

Topics

•Structure of the Milky Way galaxy: The halo, the disk and the bulge of the MW regarding

composition of gas, dust and star formation

• Location and orbits of globular clusters in the MW

•Characteristic of the variable stars RR Lyrae and Cepheids

•Luminosity vs period relationship for both variable stars

•Linear relationship between recession velocity and distance to galaxies: the Hubble law. V = Ho D

•The rotation velocity of the MW as function of distance.

•Does the velocity follows a Keplerian curve beyond the 15 kpc distance?

Questions

•What are the relationship between the two parameters that makes the Cepheids and RR Lyrae useful

to measure distances?

•How Hubble was able to determine the distance to the Andromeda galaxy?

• What did Hubble was able to deduce by studying the relationship between the distance and the

Doppler shift of galaxies (and the radial velocity?

• Do this relationship apply to the Local Group of galaxies?

•What should happen to the rotational curve of the MW beyond the visible disk?

•What is the evidence of dark matter in the outer part (beyond 15 kpc) of the MW?

•Do we know what is dark matter?

•What are the possible candidates to explain the existence of dark matter?

•How do we know that there is a black hole in the center of our galaxy?

• What method can be used to determine the mass of the black hole in the center of the MW? • How many solar masses is estimated to have the supermassive black hole in the center of the MW?

Chapter 15 – Normal and active galaxies, extending the distance scale, Hubble Law and Quasars

Topics

• Hubble classifications of galaxies: spirals, barred spirals, ellipticals, irregulars

• Hubble classification: The “tuning fork”

Increasing the distance ladder:

•Cepheids variable. Good to determine distances out to 25 Mpc

• Tully-Fisher relationship: Correlation between luminosity and rotation speed. Good out to 200 Mpc

•Type-I supernovae. Light curve good determine distances to 1 Gpc

•Cosmological redshift z = v/c = Δλ/λ

•Linear relationship between recession velocity and distance: the Hubble law

•V = Ho D

•Hubble law allow to extend the distance scale to the “end of the visible universe”

•Quasars: High redshift, large distance extremely large luminosities

•Source of power for quasars: Infalling gas is accelerated in the accretion disk around a supermassive

black hole and emit in the range of X-ray to IR

Questions

• Which type of galaxies are more massive?

• Is there dust and gas in an elliptical galaxy? Is there dust and gas in a spiral galaxy?

•Where can we find formation of new stars? In an elliptical galaxy? In a spiral galaxy?

•Is the “tuning fork” an evolutionary sequence in galaxies?

•How can we use the Hubble law to determine distances to far away galaxies? What do we need to

measure in those galaxies to determine their distance and apply Hubble law?

•How can we explain the large luminosity of a quasar?

• What were those unknown emission lines in the spectrum of a quasar? Why they could not be identified?

•If a quasar has a cosmological redshift of z = Δλ/λ = 2 = v/c, does it imply that its velocity is 2c? (15.1)

•What method can be used to determine the mass of the black hole in a quasar?

Chapter 17 – Cosmology Topics

• Hubble Law and the expansion of the Universe

• The age of the Universe

• The Big Bang

• Cosmological redshift, the expansion of space

• The wavelength of light emitted by galaxies, the expansion of space

• The effect of the expansion of space and the gravitational attraction

• The Cosmic Microwave Background (CMB) radiation

• Temperature of the cosmic blackbody emission from the CMB

•The acceleration of the expansion of the Universe: Dark Energy

Questions

• How can we estimate the age of the Universe?

• Does the Universe has a center?

• How is the wavelength of light emitted by galaxies affected by the expansion of space?

• On a small scale, such as the Local Group, are galaxies flying apart? What force is

involved?

• What is the temperature of the CMB? In which part of the spectrum peaks the CMB

emission?

• The radiation that originated the CMB was emitted when the Universe was hot, in the

Gamma ray part of the spectrum. What happened to the radiation that now is in the

microwave range?

•What is Dark energy? Why it has been necessary to postulate the presence of Dark

Energy?