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: Zhixuan Li (李志炫)
l-zx24@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
these html Lectures notes

please join the WeChat group (if not already)
(please, leave the channel if you decide to drop the course)

7 Modules

Light
How light plays its role in Astronomy
distances, radiation, magnitudes, HR-diagram, atmospheres
Matter under astrophysical conditions
Evolution
Atmospheres
Birth
Exoplanets
Planet Dynamics

7 Modules

Light
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
Evolution
Atmospheres
Birth
Exoplanets
Planet Dynamics

7 Modules

Light
Matter under astrophysical conditions
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
Atmospheres
Birth
Exoplanets
Planet Dynamics

7 Modules

Light
Matter under astrophysical conditions
Evolution
Atmospheres
How do the observational properties of stars and planets come about?
Electronic/vibrational, and rotational transitions, H-atom, ionization, greenhouse
Birth
Exoplanets
Planet Dynamics

7 Modules

Light
Matter under astrophysical conditions
Evolution
Atmospheres
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
Exoplanets
Planet Dynamics

7 Modules

Light
Matter under astrophysical conditions
Evolution
Atmospheres
Birth
Exoplanets
How are the >5200 detected exoplanets found?
planet detection techiques: radial velocity method, transits, microlensing, astrometry, direct imaging
Planet Dynamics

7 Modules

Light
Matter under astrophysical conditions
Evolution
Atmospheres
Birth
Exoplanets
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

Material

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

Reference Books
- An Introduction to Modern Astrophysics
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

Reference Books
- An Introduction to Modern Astrophysics
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

Reference Books
- An Introduction to Modern Astrophysics
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

Reference Books
- An Introduction to Modern Astrophysics
Html lecture notes
- Available from my homepage
- Princeton Series in Astrophysics
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

Reference Books
- An Introduction to Modern Astrophysics
Html lecture notes
- Available from my homepage
- Princeton Series in Astrophysics
Blackboard
You need to be able to follow, understand, and derive yourself the material presented on the blackboard.
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.

grading

Grade = 0.2 PS + 0.2 Exam/quiz + 0.2 Exam/Problems )
+0.2 max( Presentation,[Report^†] )
+0.2 max( Exam/Quiz, in-class quizzes, Exam/Probl., PS, [Report^†] )

Course Elements and Grade contribution

Problem sets (20%)
In addition, the score can also be used towards the Free Area
Exam:
- Problem part (20%)
  Similar to the Problem Sets. The score can contribute towards your Free Areas
- Quiz part (20%)
  Similar to the in-class quizzes. Multiple choice questions
In-class quizzes
multiple choice questions about the 7 modules. The score can contribute towards your Free Area.
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 the Free Area (but not both!)

grading

Grade = 0.2 PS + 0.2 Exam/quiz + 0.2 Exam/Problems )
+0.2 max( Presentation,[Report^†] )
+0.2 max( Exam/Quiz, in-class quizzes, Exam/Probl., PS, [Report^†] )

More grade optimization

Best of Presentation or Report I (20%)
The report is optional.
20% of your final grade falls in the Free Area. This is the best of your score on:
- Problem sets
- Exam (Problems part)
- Exam (Quizzes)
- Report

grading

Grade = 0.2 PS + 0.2 Exam/quiz + 0.2 Exam/Problems )
+0.2 max( Presentation,[Report^†] )
+0.2 max( Exam/Quiz, in-class quizzes, Exam/Probl., PS, [Report^†] )

Examples

Name	PS	Ex/Q	Ex/Pr	in-class Q.	Present.	Report	Free Area
Ann	0.4	0.2	0.2	—	—	0.2	PS
Bart	0.2	0.2	—	—	0.2	0.4	Report
Caro	0.2	0.2	0.2	0.2	0.2	—	in-class quizzes
Donald	0.2	0.2	0.4	—	0.2	—	Exam/Problems
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
Bart writes a very impressive report
Caro excels in the conceptual quizzes during the lectures.
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, E_I) had already been given earlier (no need to repeat) or are fundamental constants (h, k, m_e).

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!

unit	cgs unit	abbrev.	SI unit
length	centimeter	cm	10^-2m
time	seconds	s	1 s
mass	gram	g	10^-3 kg
energy	erg	erg	10^-7 J
pressure		erg cm^-3	10^-1 Pa
magnetic-B	Gauss	G	10^-4 T
cgs units

fundamental and astronomical constants in cgs and SI

constant	symbol	cgs value	unit	SI value	unit
Astronomical unit	au	1.496×10¹³	cm	1.496×10¹¹	m
Atomic mass constant	m_u	1.661×10^-24	g	1.661×10^-27	kg
Boltzmann constant	k	1.381×10⁻¹⁶	erg K^-1	1.381×10⁻²³	J K^-1
Electron mass	m_e	9.109×10⁻²⁸	g	9.109×10⁻³¹	kg
Electron volt	eV	1.602×10⁻¹²	erg	1.602×10⁻¹⁹	J
Elementary charge	e	4.803×10⁻¹⁰	cm^3/2 g^1/2 s^-1	1.602×10⁻¹⁹	C
Gravitational constant	G	6.674×10⁻⁸	cm³ g^-1 s^-2	6.674×10⁻¹¹	m³ kg^-1 s^-2
Planck constant	h	6.626×10⁻²⁷	erg s	6.626×10⁻³⁴	J s
Solar luminosity	L_⊙	3.828×10³³	erg s^-1	3.828×10²⁶	W
Solar radius	R_⊙	6.957×10¹⁰	cm	6.957×10⁸	m
Solar mass	M_⊙	1.988×10³³	g	1.988×10³⁰	kg
Speed of light in vacuum	c	2.998×10¹⁰	cm s^-1	2.998×10⁸	m 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?

in oom calculations, cows are spherical

matplotlib tutorial

for dummies

—By Zhixuan Li—

TA Zhixuan Li will host 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 Zhixuan Li know when you are available
Zhixuan Li will send out a WeChat questionnaire on this

research project

You will be conducting a mini research project in the field of stellar evolution. The procedure is the following:

You complete the MESA Tutorial and its exercises.
See the MESA Project Manual in Tsinghua Cloud for further guidance. The performance must be satisfactory, as judged by TA Zhixuan Li. Note: if the performance is unsatisfactory, we will return the questions and you can only resubmit after 1 week. Submit well before the deadline.
You pick a project from the list
See the Project Manual. The deadline to complete the problems and pick a project is 25 April. Projects are distributed on a first come, first serve basis.
You report on your findings in class during the final 2 teaching weeks
You write a report about your findings
This is optional. See grading procedure.

topic	level
evolution of ... star
0.5 solar mass	☆
2 solar mass	☆
5 solar mass	☆
...	☆
advanced problems
mass loss during the RGB	☆☆
stellar variability	☆☆
Horizontal Branch and Red Clump	☆☆
Brown Dwarfs	☆☆
...	☆☆

Weekly Notes

Course Schedule

day	agenda	notes
26.02	M0/Introduction + Quiz-0 M1/Light...	Quiz-0 is not graded
05.03	M1/Light; start M2/Astromatter
TBD	matplotlib tutorial (TA Zhixuan Li)	outside regular class; optional
12.03	M2/Astromatter	deadline PS-1
19.03	end M2/Astromatter, start M3/Evolution
26.03	continue M3/Evolution
...	(4 April lectures)
25.04	deadline to finalize the topic of your mini-research project
30.04	Labor day holiday — no class
...	(4 May lectures)
04.06	project presentations
11.06	project presentations	Last teaching day
TBD	exam
upcoming schedule