Primary Text: Cosmic Perspective, 4rd edition, Bennett et al. (2006)
COPIES OF LECTURE SLIDES ARE POSTED AFTER EACH LECTURE (click on underlined links
that get you to Acrobat-readable pdf files -- slides here are in black & white,
and six to a page for economy)
Reading prior to class: Chap 1 (Our place in the universe) and `How to succeed
in your astronomy course' (preface). Detailed course syllabus distributed (also
posted on website here). Homework Set #1 passed out (due Thur 24 Jan).
- Introduction to topics to be covered
- Challenge of vast range of scales, in space and time
- We are but one star of several hundred billion in our galaxy
- And there are billions of galaxies.....
- Scientific method: what it is all about
- Nature of astronomy as a science
Reading prior to class: Chap 2 (briefly), Chap 3 (especially 3.4), Chap 4 (briefly)
and then read carefully all of Chap 5 (Light and Matter). Respond on CULearn course
site by Thur Jan 24 to discussion question on `Why are most big telescopes reflectors?'.
In-class registration of i-clickers.
- Light as waves
- Interaction of light and atoms, yielding spectral lines unique to each atom
- Emission and absorption of light, and resulting spectra
- Opening comments on Kirchoff's laws
Reading prior to class: Read Chap 6 (Telescopes) thoroughly, survey read
Chap 14 (Our Star). Homework Set #2 passed out.
- Kirchoff's laws about emission and absorption features
- Black-body spectrum (Plank's law), peak energy and overall emission vary
in important ways with temperature (Wien and Stefan-Boltzmann laws)
- Doppler effect (redshifts and blueshifts of spectral lines))
- Doppler broadening by rotation of star
- And just what is the wavelength/frequency of your cell phone?
- Principles common to our eyes, cameras, telescopes
Reading prior to class: Read Chap 6 (Telescopes) thoroughly, survey read
Chap 14 (Our Star). Homework Set #1 due in class. Respond to discussion question
for next Thur Jan 31 on 'Pros/cons of lunar observatory'.
- Examine range of big telescopes used in astronomy
- Reflectors prevail over refractors for astronomy (discussion)
- Nature of instruments on telescopes for real analysis
- Effects of our atmosphere on light; what light gets through, what does not
- Light pollution, twinkling by turbulence, absorption by atmosphere
- Adaptive optics
- Nature of radio observatories (aperture synthesis from arrays)
- How and what do we observe from space
- Conserving angular momentum, useful to point space telescopes
Reading prior to class: Complete reading Chap 14 (Our Star). New Homework Set #3
passed out, Homework Set #2 due in class.
- X-ray telescopes (grazing reflections) and radio telescopes (often arrays
of dishes, and `aperture synthesis')
- Overview of our nearest star, the Sun
- Regions of the Sun and their function: core, radiative zone,
convective envelope, atmosphere
- Why is a star round?
- Equilibrium between pull of gravity and push of pressure
- Why does the Sun shine?
- Fusion reactions convert H to He, keep the center very hot
Reading prior to class: Second reading of Chap 14 (Our Star).
Start reading S4 `Building blocks of universe', to be discussed in Mon Feb 4
recitation (especially S4.1 and S4.2). Respond to discussion question on 'How
do we test/deduce what is deep within the Sun' by Tues Feb 5 (this timing
different since planetarium on Thur).
- Fusion reactions (p-p chain) convert H to He, center very hot
- Examine details of p-p fusion, including making neutrinos and gamma-ray photons
- Energy yield from H fusion is vastly greater than from chemical burning!
- Fusion burning of 1 kg of H into He (7 grams turned into energy) is equivalent
to chemical burning of two units trains of coal (200,000 Tons)!
- Workings of the solar thermostat to maintain stable energy production in core
- Discussion of pros/cons of an astronomical observatory on the Moon
New Homework Set #4 passed out, Homework Set #3 due in class. Respond to discussion
on `Effects of solar activity on our technological society' by next Tues Feb 12.
Review Set #1 passed out to help prepare for Mid-Term Exam 1 on Mon Feb 18 (in
recitation).
- Puzzle of the solar neutrinos
- How temperature and density varies with radius inside the Sun
- How sampling of sound waves at the solar surface yields probes of the interior
- What helioseismology reveals about interior flows and structures
- Striking solar differential rotation, flows of solar subsurface weather (SSW)
- Discussion: How do we test/deduce what is deep within the Sun?
Class meets in Fiske Planetarium, please proceed there directly, try not to
be late. Survey read Chap 16 (Star Birth) in advance of this program. Bring along
your i-clickers. Observatory Night #2 this Thurs evening at 7pm (by prior signup).
Reading prior to class: Read Chap 15 on properties of stars in detail. Review
Set #1 still available, to prepare for Mid-Term Exam 1 in recitation on Mon Feb 18.
Tesla coil demo of plasmas.
- Revisit results from helioseismology about internal flows
- Solar granulation and surface convection
- The solar magnetic cycle involving sunspots and variable activity
- Solar magnetic fields and their 11-year cycles
- Coronal mass ejections and flares from magnetic field reconnections
Reading prior to class: Review Chap 15 (Surveying the Stars). Evening review
session by Kyle Augustson this Thurs evening, Duane G-125 (7pm-9pm), to help prepare
for Mid-Term Exam 1 in recitation on Mon Feb 18.
- Discussion: Effects of solar activity on our technological society
- Solar magnetism, solar wind and northern lights
- Effects of solar activity on our planet
- What can we measure in other stars: brightness, position, spectrum
- Stellar luminosity and apparent brightness
- Distance from stellar parallax
- Devising a classification for stars based on absorption
features in spectra (O,B,A,F,G,K,M) [Annie Cannon]
Reading prior to class: Review Chap 15 (Surveying the Stars). New Homework #5
passed out. Respond to discussion on "City of Stars" by next Tues Feb 26.
- Why surface temperature of star and spectral classification (O,B,A ..)
are closely linked [Cecelia Payne-Gaposchkin]
- Saha equation used to predict spectral line strengths with temperature
- Luminosity classes by width of spectral lines (I to V)
- Where different stars lie on H-R diagram in overview
- Measuring brightness of stars: strange system of magnitudes, originally
from Greeks!
- Apparent vs absolute magnitude (luminosity) requires knowing distance
Reading prior to class: Focus on binary stars, including mathematical
insight 15.4 on `Newton's version of Kepler's 3rd law' to measure stellar
masses. Overview read Chap 16 (Birth of Stars) by next Tues. Graded Mid-Term Exam
1 returned, with answers. Observatory Night #3 this coming Mon
- Discussed Kepler's laws and how derived
- Determine radii of stars, if know luminosity and temperature
- Four varieties of binary stars (based on detection)
- Estimating stellar masses from binary star data
- C-N-O fusion cycle powers the more massive stars
- Nuclear fusion reactions increase very rapidly with temperature: thus
massive stars really pour out the energy!
Reading prior to class: Read 15.3 `Star Clusters' carefully, and first detail read
of Chap 16 `Star Birth'. Homework #5 due in class, new HW #6 passed out. Mid-Term
project Planet Finder passed out and discussed in recitation,
- "Observed" mass-luminosity relation for main sequence stars
- Estimate how lifetimes on main sequence vary with stellar mass
- Massive stars have very short lifetimes on main sequence
- Cities of stars come in two varieties: open clusters (small) and globular clusters (big)
- Test ideas about evolution by looking at H-R diagrams of star clusters
- Peel-off from main sequence helps estimate age of cluster
- Overview of spiral galaxy: stars and gas in disk rotate faster than spiral
pattern, with gas compressed as they enter these `traffic jams', leading to vigorous
star birth in molecular clouds
Lecture 14: `City of Stars', Planetarium presentation. (Thur, Feb 28)
Class meets in Fiske Planetarium, please proceed there directly, try not to
be late. Survey read Chap 17 (Star Stuff) in advance of this program. Bring along
your i-clickers. Note that recitations on Mon March 3 meet in computer lab Duane
G116 (east of standard room E126) to look at Planet Finder in detail.
Reading prior to class: Overview read all of Chap 17 `Star Stuff' to
get a sense of evolution of stars. Read 17.2 `Life as a low-mass star'
carefully. Stellar evolution overview sheet provided. Homework Set #6 due in
class, new HW #7 passed out. Respond to discussion question on shapes of planetary
nebulae by Thurs.
- How large clouds of gas and dust (recycled from previous generations in spiral
galaxy) may begin to collapse and form new stars
- Tyranny of too much angular momentum as star is being assembled
- Seeing into the `dusty cocoons' with near infrared wavelengths
- Nuclear furnaces slowly turn on and protostar approaches the main sequence
- Life after main sequence for low-mass stars -- becoming a red giant
- Red giant star, with H shell burning, has shrinking inert He core
- Degenerate matter has no thermostat, such as in red giant's core
- Helium flash in core (triple-alpha burning of He) removes degeneracy
- Burning He in core (horizontal branch)
- Red supergiant phase (with double-shell burning of H and He)
Reading prior to class: Read 17.3 `Life as a high-mass star' carefully,
and also 17.4 `Roles of mass and mass exchange'. Overview read Chap 18 `The
Bizarre Stellar Graveyard', and study 18.1 `White dwarfs' in detail.
- Revisit subtleties of red giant, horizontal branch, and supergiant evolution
- Planetary nebula involves shells `puffed off' from supergiant
- Discuss remarkable shapes of planetary nebulae (PN): what may cause these?
- Likely answer: rotation and magnetism likely influences shape of PN
- Properties of white dwarf star, as end of line for a low-mass star (unless
it has a companion!)
- Why electron degeneracy pressure can only support a white dwarf up to
1.4 solar masses
- White dwarf of one solar mass is roughly Earth-size; more massive are smaller!
- Brief overview of massive star evolution
Reading prior to class: Read 18.2 `Neutron stars' with care. Observatory Night
#4 is Wed Mar 12, 8 pm+. Evening review for Second Mid-Term Exam by Kyle Augustson
is on Thur Mar 13 at 7 pm+. Homework Set #7 due in class, new HW #8 passed out.
- Mass exchange by Roche lobe overflow in binary system: Algol paradox
- Evolution of massive stars through giant and supergiant phases
- Strong winds from massive stars, even big ejecta (Eta Carinae)
- Fusion burning by He-capture of C, N, O .. in core and surrounding shells,
like layers of onion: iron is the end of line!
- With enough core mass of iron, electron degeneracy can no longer support
the star: `core collapse' supernova explosion
- Supernovae (SN) can create neutron stars, formed from their collapsed
iron cores
- SN explosion leads to nucleosynthesis, making all elements in universe
heavier than iron
- Remnant left behind could be a neutron star, supported by neutron degeneracy
pressure
- Pulsars: rapidly rotating neutron stars with fierce magnetic fields
Reading prior to class: Review 18.2 `Neutron stars' and 18.3 `Black holes'
with some care. Evening review for Second Mid-Term Exam by Kyle Augustson
is tonight Thur Mar 13 at 7 pm+ (Exam is in recitation, Mon Mar 17).
- Discovery of radio pulses from unknown source, with very steady beat!
- Detailed look at pulsars: rapidly rotating neutron stars with fierce
magnetic fields
- Synchrotron radiation is source of intense light beamed by pulsars
- Listen to radio emission from several pulsars (some go with heavy metal
beat, others like bongo drums, some are a fast buzz!)
- These `lighthouses in the sky' gradually slow down, using rotational energy
to power the beams
- How mass transfer onto a neutron star in a binary system can spin it up
- Crab nebula supernova (4 July 1054) and pulsar show stunning behavior
in Chandra and Hubble movies
- Supernova 1987A as an explosion of a star in the nearby Large Magellanic Cloud
observed 150,000 years later by us with modern equipment and satellites
- Evolving structure, shocks and emission from SN 1987A -- seeing changes
in `real time'
Reading prior to class: Review 18.3 `Black holes'. Overview read S.3 `Spacetime &
Gravity' and Chap 19 `Our Galaxy'. Respond to discussion question on `We are made
of star stuff' by Thur March 20 class. Planet Finder and HW #8 due by Thur also (pre-SB).
- Binary mass transfer onto white dwarfs can yield recurrent novae, or even
detonate entire star (fusion of carbon) in supernova explosion
- Such `white dwarf supernovae' are superb bright reference `candles'
- Hot accretion disks always formed around objects on receiving end of
binary mass transfer
- Similar mass transfer onto neutron stars, with helium flash burning,
may explain x-ray bursters
- Einstein argued space and time are not distinct if speed of light is
constant for all observers: thus need 4-dimensional `spacetime'
- Time slowed down by moving fast or experiencing strong gravity
- Strong gravity can seemingly bend light and redshift its frequency:
warping of space and time by gravity
- Escape cones for light close at the `event horizon' around black holes,
at a `Schwarzschild radius'
- Just three numbers describe a black hole: mass, electric charge, angular
momentum
- Ergosphere: a spinning black hole drags nearby spacetime along
Reading prior to class: Read 19.1 and 19.2 carefully, helping you also prepare
your response to the discussion question on "Cycle of gas and stars" due Apr 3
after Spring Break. Graded Second Mid-Term Exam returned. Note that Planet Finder
term project and HW #8 are due this Thur prior to SB.
- How to detect a black hole
- Cygnus X-1 fine candidate for revealing a black hole in binary system
- The very strange object SS433, likely binary mass flow onto black hole
that sends out precessing relativistic beams
- Overview of Milky Way: spiral galaxy with thin disk, bulge and halo
- Since stars and gas are always moving, inspires the galaxy song
`The Galaxy / Lighten Up'
- Motion of stars in galaxy: disk stars in nearly circular motion, halo
and bulge stars in swooping orbits that dive through disk
- Spiral patterns outlined by bright O & B star associations
- Interstellar medium (ISM), or stuff between the stars: its various
components visited
Reading prior to class: Focus on 19.2 `Galactic Recycling'. Observatory Night
#5 is on Thur Apr 3. New Homework Set #9 passed out.
- Look at how spiral patterns are made in the disks of galaxies,
including our own: gas and stellar traffic jams
- Spiral patterns outlined by bright O & B star associations, with
vigorous star birth occurring in spiral arms
- Interstellar medium (ISM), or stuff between the stars: its various
components visited
- Discuss significance of "We are made of star stuff"
- Continue with ISM inventory
- Superbubbles blown by multiple supernovae, can even burst out of galactic
disk
Reading prior to class: Focus on 19.3 `History of Milky Way' and 19.4
`Mysterious Galactic Center'. Start overview reading Chap 20 `Galaxies' to be
discussed next week. Observatory Night #5 tonight, 8:30pm.
- Some of the gas in ISM is very hot (from supernovae bubbles)
- Some of the gas is warm (emission nebulae near hot stars)
- Some is cold (molecular clouds), sites of star birth
- Dust is semi-warm, and can both absorb light and redden it, confusing
distance estimates and blocking objects from view at visible wavelengths
- Discuss whether "star-gas-star cycle" in Milky Way will continue forever
- Radio observations with 21 cm line of neutral hydrogen help reveal
spiral structure in MW disk
- Big mystery resolved: center of our galaxy contains 3.7 million solar
mass black hole
Reading prior to class: Overview read Chap 20 `Galaxies', then focus on
20.1 `Galaxy Types'. New Homework Set #10 passed out.
- Revisit evidence for supermassive black hole (SagA*) at center of Milky Way
- Edwin Hubble shows in 1924, using Cepheid variables, that Andromeda lies
way outside of Milky Way -- there are other island universes!
- Great surprises from Spitzer space telescope imaging Andromeda in infra-red
- Classifying galaxies by appearance and shape: spirals, barred spirals,
ellipticals, irregulars (Hubble's `tuning fork')
- What sample galaxies look like, and where found
- Big picture of universe: network of galaxy clusters and superclusters,
with about 100 billion galaxies in all
- Our local group of galaxies: Andromeda, Triangulum and Milky Way are
the heavyweights, then LMC and SMC, plus small ones, about 21 in all
Reading prior to class: Read with some care 20.2 `Measuring Cosmic
Distances'. and 20.3 `Hubble's Law'. Then proceed to overview read Chap 21,
`Galaxy Evolution'. Review Set 3 passed out for Third Mid-Term Exam on
Mon Apr 21 (with review on Thurs Apr 17 evening).
- Hubble busily measures redshifts of many galaxies, announcing in
1929 that redshifts of galaxies appear to increase with distance from us
- Hubble's Law and what it means: we are in an expanding universe!
- Measuring cosmic distances is a big challenge: identify `standard candles'
- Parallax, main-sequence fitting, Cepheid variables, Tully-Fisher relation
and white dwarf each provide ways to estimate increasingly greater distances
- Distance ladder using overlapping standard candles
- Knowing the redshift of an object, can use Hubble's Law itself,
once calibrated, for estimating biggest distances (or `lookback time')
Reading prior to class: Complete reading galaxy formation story with care in
Chap 21 `Galaxy Evolution'. New Homework Set #11 passed out.
- Revisit `distance ladder' using overlapping standard candles
- Most mapping of 3-D structure of galaxy clusters and superclusters
thus accomplished using Hubble's Law
- Steps in forming a spiral galaxy, and in making ellipticals
- Birth of galaxies in clusters (few if any are born alone)
- Collisions or `interactions' between galaxies must be common
- Simulations of colliding galaxies yield bridges and
tails, many of which are observed
- Modelling the `Mice' and the `Antennae' as interacting galaxies, and
even of future crash of Andromeda with our Milky Way
Reading prior to class: Read 21.3 `Quasars and Active Galactic Nuclei' in
detail. Start overview reading of Chap 22 `Dark Matter and Fate of Universe'.
Evening review for Third Mid-Term Exam tonight.
- Messages from galaxy interactions (collisions): must be common early
in dense clusters; spiral galaxies can tumble together to form elliptical
galaxy; vastly increased star birth (starburst); rapid feeding of massive
black hole (quasars and radio galaxies)
- Quasars - how discovered at large redshifts through bright emission lines
of hydrogen
- Lyman alpha forest of absorption lines seen in spectra of quasars
- Model of `active galaxies': accretion disk around supermassive black
hole, particle beams on axis of spinning disk form jets
- Synchrotron emission from jets can explain beams, seen also as great
`radio tails'
Reading prior to class: Read 22.2 `Evidence for Dark Matter' carefully.
New Homework Set #12 passed out. Last Observatory Night #6 on Wed Apr 23.
- Visit giant elliptical galaxy M81 with jet and
central supermassive black hole (SBH)
- Remarkable scaling of SBH in many galaxies with their halo masses
- Case for dark matter as huge surrounding halo to spiral galaxy: flat
rotation curves
- Galaxy clusters reveal presence of dark matter in three ways: large random
velocities of member galaxies, hot x-ray emitting gas in cluster, gravitational
lensing
- Many examples now of gravitational lensing by clusters
- Ten times more dark matter than ordinary `baryonic' matter
- Dark matter: MACHOs or WIMPs, or neither?
- Cosmological models of universe, first look
Reading prior to class: Read 22.4 `Universe's Fate'. Overview read
Chap 23 `Beginning of Time'. Third Mid-Term
Exam returned with answer sheet.
- Brief history of how Einstein's General Theory of Relativity (GTR) was
quickly used by Friedman and Lemaitre
- Cosmic microwave background (CMB) and its many implications
- Dark matter and fates of universe
- Three choices for fate of universe: coasting (open), critical (flat),
recollapsing (closed)
- A new ingredient added to probing expansion rate of universe:
white dwarf supernovae
Reading prior to class: Complete reading Chap 23 `Beginning of Time'
carefully. Note that comprehensive Final Exam is on Mon 5 May,
1:30pm-4:00pm, in usual lecture classroom Duane G131. Review Sheet #4 (for final)
passed out.
- New twist on expansion: white dwarf supernovae suggest acceleration
of universe from its earlier slowing down
- `Dark energy' invented to give outward push to expansion of universe, to
counteract the inward pull of gravity slowing it down
- Very early `inflation' invoked to explain uniformity of CMB and 1 degree
scale of variation as observed with Boomerang and WMAP
- Dark energy 73%, cold dark matter 23%, ordinary (baryonic) matter 4%
Reading prior to class: Re-read 23.2 'Evidence for the Big Bang', and
return to 22.3 `Structure Formation'.
- Gamow led the way with calculating nucleosynthesis within the
big bang and which elements would be produced - looking at first 3 minutes
in the `fires of creation'
- Discuss rapid eras of particles, nucleosynthesis, and nuclei
- Recombination: after 380,000 years, universe cooled to about 3000K,
atoms can form and photons can begin to travel freely -- now viewed as CMB
- Era of galaxies and stars started after about 1 billion years
- Simulations reveal large-scale structure formation in universe, leading
to voids and sheets and galaxy clusters
- The current big mysteries about our universe
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