Stars and Planets

Module 0 > >

— Course description —

Chris Ormel

Stars and Planets

Instructor: Prof. Chris Ormel
New Physics Building, 2nd floor, E223
chrisormel@tsinghua.edu.cn

Teaching Assistant: Tian Yi (易天)
yit23@mails.tsinghua.edu.cn

Time: Thursday 19:20—21:45

Course layout

  • Lectures
  • Problem sets discussion
  • Student presentations on special topic (final weeks)
  • (Student reports)
  • Exam

communication

  • Tsinghua Cloud
    • course announcement (e.g., homework deadlines)
    • course material (problem sets, pdf printouts, data files)
    • do bookmark this site!
  • WeChat group
    • use for notifications and questions
    • use English; we will ignore any messages in Chinese
  • WebLearning (https://learn.tsinghua.edu.cn/)
    • for homework returns

      course number is 40920013-90

  • Email
    • homework return (if system is offline)
    • for office hour appointments
  • html Lectures notes
please join the WeChat group (if not already)

6 Modules

  1. Exoplanets
    How are the >5200 detected exoplanets found?

    planet detection techiques: radial velocity method, transits, microlensing, astrometry, direct imaging

  2. Planet Dynamics
  3. Light
  4. Matter under astrophysical conditions
  5. Birth
  6. Evolution

 

6 Modules

  1. Exoplanets
  2. Planet Dynamics
    How do planets move around stars?

    The two body problem, orbital elements, resonances, numerical integration techniques; three body problem, Lagrange points, tides, Earth-Moon system

  3. Light
  4. Matter under astrophysical conditions
  5. Birth
  6. Evolution

 

6 Modules

  1. Exoplanets
  2. Planet Dynamics
  3. Light
    How light plays its role in Astronomy

    distances, radiation, magnitudes, HR-diagram, atmospheres

  4. Matter under astrophysical conditions
  5. Birth
  6. Evolution

 

6 Modules

  1. Exoplanets
  2. Planet Dynamics
  3. Light
  4. Matter under astrophysical conditions
    How does material behave in stars?

    Equations of States: degenerate matter, hydrostatic balance, polytropes
    Nuclear fusion: energy reservoirs, proton-proton & CNO cycle, nucleosynthesis

  5. Birth
  6. Evolution

 

6 Modules

  1. Exoplanets
  2. Planet Dynamics
  3. Light
  4. Matter under astrophysical conditions
  5. Birth
    How do stars and planets form?

    Star formation: virial theorem, Jeans mass, initial mass function, Eddington Luminosity, Dispersion relationship, gravitational instability
    Planet formation: protoplanetary disks, disk instability and core accretion, gravitational focusing and runaway growth

  6. Evolution

 

6 Modules

  1. Exoplanets
  2. Planet Dynamics
  3. Light
  4. Matter under astrophysical conditions
  5. Birth
  6. Evolution
    How do stars evolve and meet their end?

    mean free path and opacity, energy transport, stellar structure equations, stellar evolution, features in HR-diagram, homology, burning sequences, nucleosynthesis

 

Material

 

  1. Reference Books
    • An Introduction to Modern Astrophysics

      2nd edition; Carroll & Ostlie (2006); Main reference book for this course (but not all chapters will be discussed!) [jd.com]

    • Stellar Structure and Evolution

      (Astronomy and Astrophysics Library) 3 STG Edition by Kippenhahn, Rudolf, Weigert, Alfred published by Springer (1996)

    • Solar System Dynamics

      by Murray & Dermott, Cambridge University Press (1999)

    • The Astrophysics of Planet Formation

      by Armitage, Cambridge University Press (2009)

    • Dynamics of Planetary Systems

      by Tremaine, Cambridge University Press (2009)

The B.O.B.

Material

 

  1. Reference Books
    • An Introduction to Modern Astrophysics
  2. Html lecture notes
    • Available from my homepage
    • Tested with Firefox, Chrome/Chromium, and MS Edge browsers. Download them if necessary

      MS Internet Explorer is not supported!

Material

 

  1. Reference Books
    • An Introduction to Modern Astrophysics
  2. Html lecture notes
    • Available from my homepage
    • Princeton Series in Astrophysics Mind nested pages !!
    • hint: press o for slide overview
nested page. Press <down> button to continue with the nest!
nested pages have ended. Press <right> to continue with the next topic

Material

 

  1. Reference Books
    • An Introduction to Modern Astrophysics
  2. Html lecture notes
    • Available from my homepage
    • Princeton Series in Astrophysics
    • read all the text. You should for sure learn all magenta-highlighted terms!

      Don't forget to read the small fonts. I may skip some details in class, but it may help you to comprehend the material when you reviewing it.

Material

 

  1. Reference Books
    • An Introduction to Modern Astrophysics
  2. Html lecture notes
    • Available from my homepage
    • Princeton Series in Astrophysics
  3. Blackboard

    You need to be able to follow, understand, and derive yourself the material presented on the blackboard.

    Some material may not be covered in the book! So, do attend the lectures!

E = mc2

Material

 

  1. Reference Books
    • An Introduction to Modern Astrophysics
  2. Html lecture notes
    • Available from my homepage
    • Princeton Series in Astrophysics
  3. Blackboard

    You need to be able to follow, understand, and derive yourself the material presented on the blackboard.

  4. Online resources (www) and (especially) Wikipedia

    Wikipedia is today's Library of Alexandria. A true gem, indispensable to the modern scientist.
    I have tried to place references (links) as much as possible. You should do the same in your reporting.

Units in Astronomy


Like most astronomers, I will use the cgs (centimeter-gram-seconds) or Gaussian unit system.

The most radical difference with SI units is that the Gauss unit system omits proportionality constants in the electromagnetic laws. For example, the Coulomb law becomes

That is, without the proportionality constant of . The drawback of this choice is that other electromagnetic laws — notably Maxwell's equations — also look different. But we won't use them in this course

In your problem sets, you are welcome to use SI units. But take care and be consistent!

unitcgs unitabbrev.SI unit
lengthcentimetercm10-2m
timesecondss1 s
massgramg10-3 kg
energyergerg10-7 J
pressureerg cm-310-1 Pa
magnetic-BGaussG10-4 T
cgs units

fundamental and astronomical constants in cgs and SI


constantsymbolcgs valueunitSI valueunit
Astronomical unitau1.496×1013cm1.496×1011m
Atomic mass constantmu1.661×10-24g1.661×10-27kg
Boltzmann constantk1.381×10−16erg K-11.381×10−23J K-1
Electron massme9.109×10−28g9.109×10−31kg
Electron volteV1.602×10−12erg1.602×10−19J
Elementary chargee4.803×10−10cm3/2 g1/2 s-11.602×10−19C
Gravitational constantG6.674×10−8cm3 g-1 s-26.674×10−11m3 kg-1 s-2
Planck constanth6.626×10−27erg s6.626×10−34J s
Solar luminosityL⊙3.828×1033erg s-13.828×1026W
Solar radiusR⊙6.957×1010cm6.957×108m
Solar massM⊙1.988×1033g1.988×1030kg
Speed of light in vacuumc2.998×1010cm s-12.998×108m s-1
Some (fundamental) constants in cgs and SI units

Dimensional analysis

Dimensional analysis:

  • to check the equations
  • to predict the form of the expression

    you will not get the numerical prefactor right

  • Example of dimensional analysis problems:
    • what is the free-fall time of a collapsing (spherical) cloud?

Order-of-magnitude physics

Order-of-magnitude (OOM) calculations

to estimate the significance of an effect without performing a "lengthy" derivation

  • answer can be off by factor 10 (or more...) but likely not by much more
  • use the "~" symbol

Example of OOM problems

  • what is the mass of a cow?
  • what is the distance to the Moon; its radius; and its surface gravity?
1m
in oom calculations, cows are spherical

grading

grading

Grade = 0.2 PS + 0.2 Exam/quiz
               +0.1 max( Exam/quiz , in-class quizzes )
               +0.2 max( Presentation,[Report†] )
               +0.2 max( Exam/problems, PS, [Report†] ) )
               +0.1 max2( Exam/problems, PS, [Report†] )

Course Elements and Grade contribution

  • Problem sets (20%)

    In addition, the score can also be used towards one of the Free Areas

  • Exam:
    • Problem part

      Similar to the Problem Sets. The score can contribute towards one of the Free Areas (below)

    • Quiz part (20%)

      Similar to the in-class quizzes. Multiple choice questions

  • In-class quizzes (10%)

    you may substitute your score for the Exam (Quiz part) here

  • Research Project
    • Presentation (20%)

      Every students gives a presentation about their project. Scheduled for the final 2 weeks. The score on the presentation can be replaced by the report.

    • Report†

      This is optional. You can replace the score of the Presentation with it OR count it towards one of the Free space (but not both!)

grading

Grade = 0.2 PS + 0.2 Exam/quiz
               +0.1 max( Exam/quiz , in-class quizzes )
               +0.2 max( Presentation,[Report†] )
               +0.2 max( Exam/problems, PS, [Report†] ) )
               +0.1 max2( Exam/problems, PS, [Report†] )

More grade optimization

  • 30% of your final grade falls in the Free Area, which counts the best of your score on:
    • Problem sets
    • Exam (Problems part)
    • Report
  • Area I (20%)

    The best of the above three elements

  • Area II (10%)

    Like the above, where we take the 2nd-best score

grading

Grade = 0.2 PS + 0.2 Exam/quiz
               +0.1 max( Exam/quiz , in-class quizzes )
               +0.2 max( Presentation,[Report†] )
               +0.2 max( Exam/problems, PS, [Report†] ) )
               +0.1 max2( Exam/problems, PS, [Report†] )

Examples

NamePSEx/QEx/Prin-class Q.Present.ReportFree Area
Ann0.40.30.1——0.2I=PS; II=Ex/Pr
Ben0.40.2—0.10.20.1I=PS; II=Report
Caro0.20.20.10.10.20.2I=Report; II=Ex/Pr
Donald0.30.30.2—0.2—I=Ex/Pr; II=PS
contribution of various components to the final grade

  • Ann struggles with her presentation and the in-class quizzes. She performs very well on her PS
  • Ben performs very well in class, but has a blackout during the exam. His final score minimizes the exam components.
  • Because of late returns, Caro got lower grades on some problem sets. So she minimizes this component.
  • Donald does not want to write a report. He performs extremely well on the exam day.

historical grade distribution

for the Stars and Planets course

Problem sets

  • About 6 in total. Typically 1 per module.

    PS will be distributed on the day when the module is first discussed in class. They must be returned one week after the last day the module has been covered in class

  • Collaboration is allowed, but hand in by yourself

    you should be able to motivate and reproduce your solution independently. We will be very strict on academic misconduct. Do NOT blindly copy homework from others. Do NOT conduct in plagiarism when writing reports. Always state references.

  • Go easy on chatGPT/DeepSeek or other AI-tools

    you do not learn anything when asking chatGPT to solve the problems for you, it will lead to lower grades, and it will take the TA much more effort to grade. Same rules as under collaboration apply. If you cannot reproduce your own solution or you cannot explain your methodology, you will get 0 points for the entire PS.

  • Hand in solutions as pdf or hand-written.
    • Scans/photos/MS-word docs are not allowed! Write in English.
    • Those that typeset their PS beautifully (text, equations, and figures) will be awarded a +10pt bonus;
    • Our strong suggestion: use Latex/Overleaf
    • Upload pdf solutions to WebLearning
    • Strict deadlines. Late returns are subject to a   —10pt penalty/day

problem sets tips and examples

  • Label figures (axes!) appropriately
  • When using LaTeX, use equation environment

    \begin{equation} E=mc^2 \end{equation}

  • Do not insert screenshots of source code into your answer
  • Write down the symbolic expression first, then fill in numbers.

    No need to write down the numerical values if these have already been stated.

    When asked ("What is", "Give the value", etc...) do give the numerical value at the end!

  • State the units
  • Give only 1 answer!

    Suggestion: start with your primary answer and state additional arguments in brackets. (We will ignore them when they are wrong)

(anonymous) — This figure is a screenshot (resolution too low!), there are no axis labels (and units!), the aspect ratio is also unnatural.

problem sets tips and examples

  • Label figures (axes!) appropriately
  • When using LaTeX, use equation environment

    \begin{equation} E=mc^2 \end{equation}

  • Do not insert screenshots of source code into your answer
  • Write down the symbolic expression first, then fill in numbers.

    No need to write down the numerical values if these have already been stated.

    When asked ("What is", "Give the value", etc...) do give the numerical value at the end!

  • State the units
  • Give only 1 answer!

    Suggestion: start with your primary answer and state additional arguments in brackets. (We will ignore them when they are wrong)

(anonymous) — Axis are appropriately labeled, apt choice of logarithmic y-scale, multiple lines in single plot.

problem sets tips and examples

  • Label figures (axes!) appropriately
  • When using LaTeX, use equation environment

    \begin{equation} E=mc^2 \end{equation}

  • Do not insert screenshots of source code into your answer
  • Write down the symbolic expression first, then fill in numbers.

    No need to write down the numerical values if these have already been stated.

    When asked ("What is", "Give the value", etc...) do give the numerical value at the end!

  • State the units
  • Give only 1 answer!

    Suggestion: start with your primary answer and state additional arguments in brackets. (We will ignore them when they are wrong)

(anonymous) — font sizes are not in proportion! Super ugly. No bonus points!
(anonymous) — equation runs off the page. No bonus points!

problem sets tips and examples

  • Label figures (axes!) appropriately
  • When using LaTeX, use equation environment

    \begin{equation} E=mc^2 \end{equation}

  • Do not insert screenshots of source code into your answer
  • Write down the symbolic expression first, then fill in numbers.

    No need to write down the numerical values if these have already been stated.

    When asked ("What is", "Give the value", etc...) do give the numerical value at the end!

  • State the units
  • Give only 1 answer!

    Suggestion: start with your primary answer and state additional arguments in brackets. (We will ignore them when they are wrong)

(anonymous) — We will ignore mathematica screenshots. So do not add them to your homework. Just say "the integral numerically evaluates to XXX" is enough.

problem sets tips and examples

  • Label figures (axes!) appropriately
  • When using LaTeX, use equation environment

    \begin{equation} E=mc^2 \end{equation}

  • Do not insert screenshots of source code into your answer
  • Write down the symbolic expression first, then fill in numbers.

    No need to write down the numerical values if these have already been stated.

    When asked ("What is", "Give the value", etc...) do give the numerical value at the end!

  • State the units
  • Give only 1 answer!

    Suggestion: start with your primary answer and state additional arguments in brackets. (We will ignore them when they are wrong)

"
first give the symbolic expression, then fill in numbers (like done here)
.. no need to write down value of Planck constant
.. not necessary to state value of I if previously stated, or say:
where I=... has been used
where the above value of I has been adopted, etc.
(anonymous) — Clear and to the point. Values of variable (T, EI) had already been given earlier (no need to repeat) or are fundamental constants (h, k, me).

matplotlib tutorial

for dummies

—By Tian Yi—

TA Tian Yi will provide a tutorial how to use python/matplotlib and related packages. In this tutorial you will learn:

  • how to install relevant packages onto your laptop

    python3, matplotlib, jupyter lab, rebound

  • how to create publication-quality ready plots


The tutorial is voluntarily but strongly recommended, especially if you do not know how to make plots. I suggest:

  • See if you can install the packages and do the assignments yourself
  • Let Tian Yi know when you are available

    Tian Yi will send out a WeChat questionnaire on this

research project

You will be conducting a research project in the area of numerical gravitational dynamics. The procedure is the following:

  1. You complete the PS on numerical gravitational dynamics.

    See Tsinghua Cloud. The performance must be satisfactory, as judged by TA Tian Yi.

  2. You pick a project from the list

    A fuller description on each of these topcis will be provided. The deadline to complete the problems and pick a project is 30 April. Projects are distributed on a first come, first serve basis. More challenging projects (two stars) may take more effort, but can achieve higher scores. If you miss the deadline, you will be assigned a standard project.

  3. You work in teams of 2

    You are expected to address the questions raised in the description. But you are free to widen the scope of the research.

  4. You present your findings
  5. You write a report about your findings

    This is optional. See grading procedure.

topiclevel
standard problems
Hill sphere interactions
disintegrating exoplanets
particle settling in disks
particle orbital decay in disks
advanced problems
pebble accretion☆
the Earth-Moon system☆
stability in αCentauri☆
resonance trapping☆
planet orbit crossing☆
Kozai-Lidov oscillations☆
challenging problems
viscous stirring☆☆
planetesimal scattering & accretion☆☆
the solar system back in time☆☆

Weekly Notes

Notes 27.02

dayagendanotes
27.02Quiz-1
start M2/Dynamics
02.03 10:00matplotlib tutorial (TA Tian Yi)outside regular class; optional
06.03continue M2/Dynamics
Project Introduction		deadline PS-1
13.03finish? M2/Dynamics
Discuss PS-1
....(2 other March lectures)
....(4 April lectures)
end Aprildeadline to finalize the topic of your mini-research
01.05Labor day — no class
...(3 other May lectures)
29.05project presentations
05.06project presentationsLast teaching day
TBD exam
  upcoming schedule

Course Schedule

dayagendanotes
20.02M0/Introduction + Quiz-0
M1/Exoplanets... M2/Dynamics		Quiz-0 is not graded
27.02start/continue M2/Dynamics
TBD matplotlib tutorial (TA Tian Yi)outside regular class; optional
05.03continue M2/Dynamics
Project Introduction		deadline PS-1
....(3 other March lectures)
....(4 April lectures)
end Aprildeadline to finalize the topic of your mini-research
01.05Labor day — no class
...(3 other May lectures)
29.05project presentations
05.06project presentationsLast teaching day
TBD exam
  upcoming schedule