Extragalactic Astronomy & Cosmology

Lecture 1Jane Turner

Joint Center for AstrophysicsUMBC & NASA/GSFC

2003 Spring

[4246] Physics 316

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Course Information (PHY 316)

Extragalactic Astronomy & Cosmology (3 Credits)Requisite: PHY 122

Lectures: Tues and Thurs @ 11:30am-12:45pm Jan 28 - May 13 in PHYS 107 (unless pre-warned) Course WWW Pages www.jca.umbc.edu/~turner/2003_phys316.html

…. logistics, course outline, lecture plan

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Personal Introduction

Jane Turner 1984 BSc Mathematics with Astronomy, Univ. Leicester (UK) 1988 PhD X-ray Astronomy, Univ. Leicester (UK) 1988-1998 Various positions in the LHEA at NASA/GSFC 1998- Associate Research Professor at UMBC

Main Research Field: Observations & Interpretation of the X-ray emission from Active Galactic Nuclei

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Contact Information

E-mail is by far the best turner@lucretia.gsfc.nasa.gov

Emergencies (only) UMBC 410-455-1958 (leave mssg w/ Rose Ray) GSFC Office 301-286-5190

Office Hours By appointment only (office at NASA/GSFC), also rm 314

NOTE - I spend most of my time at NASA/GSFC (don’t just assume I’ll be at UMBC !)

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Check your E-mail (if you don’t already)

Whenever possible all important messages/dates etc associated with this course will be announced in class.

However, on occasion urgent messages will be communicated via e-mail.

I will always/only use the e-mail address UMBC have on record for you. So if your primary e-mail account is elsewhere, please make sure you have forwarding set up (you should do this anyhow !)

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Quick Course Overview - Rationale

From Roos Chapt1, p1:

Cosmology aims to explain the origin and evolution of all the contents of the universe, the underlying physical processes, and thereby to obtain a deeper understanding of the laws of physics

assumed to hold throughout the universe.

... that about covers it ...!!

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Quick Course Overview - Actually

The course will provide an overview of the History of Ideas about the Universe.

Then we’ll go on to an introduction to modern cosmology including the basics of special and general relativity; black hole basics; evidence for the big bang and the expanding universe; the formation of light elements in the early universe; the effect of dark matter on the formation of large-scale structure in the universe and galaxy motions, gravitational lenses, observations of quasars, the intergalactic medium, and measurement of cosmological parameters.

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Course Text

Required Text: Hawley and Holcomb Foundations of Modern CosmologyOxford University Press; ISBN: 0195104978; (January 1998) hardcover; ~$67 new ...access to a copy strongly suggestedAlso see web notes on

http://astsun.astro.virginia.edu/~jh8h/Foundations/contents.html

But … I won’t always be following it in order, page by page Other sources will be used (but will be supplied via handouts or WWW) Some (guided) independent research is required

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Grading - Summary

Final Exam - 35%Mid-Term Exam - 25%Student Presentation - 20%Quizzes - 20%

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Grading - More details Exams- These will be closed-book. Calculators will be allowed (any necessary numerical values & complex eqns will be provided)If an emergency prevents you taking the exam, call me and also document the emergency

Report- Each student will be given an assignment 2+ weeks to research this topic Write a report (~4-5 pages) Short presentation to class (5 mins)

Quizzes- These will be occasional (with prior warning) & closed-book Average score contributes to the grade

Homework- Will be “suggested”, but not marked. (There will be time in class to discuss any questions or problems)Some homework questions will appear on the final exam, so advantageous to work throughthese

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

What I Expect from YOU Attendance: Attendance is strongly encouraged: - I will not always stick to the text -These are where you: - get the “official” course - can/should raise questions

Academic Integrity: Standard UMBC rules apply - Don’t “cheat” in tests - Give due credit where credit is due (cite references) (don’t try and pass off stuff you have pulled from the internet as your own) Guidelines are provided at http://www.jca.umbc.edu/~george/html/courses/rules.html

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Academic Misconduct

DEFINITIONS OF ACADEMIC MISCONDUCT Academic misconduct may include but is not limited to the following:

Cheating: knowingly using or attempting to use unauthorized material, information, or study aids in any academic exercise. Fabrication: Intentional and unauthorized falsification or invention of any information or citation in an academic exercise. Facilitating Academic Dishonesty: Intentionally or knowingly helping or attempting to help another commit an act of academic dishonesty. Plagiarism: Knowingly representing the words or ideas of another as one's own in any academic exercise, including works of art and computer-generated information/images.

from http://www.umbc.edu/provost/AcademicIntegrity/StudentAcadConductPolicy.htm

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Rules on “Consultation”

In Class discouraged Ask me instead !

Homework allowed …but make sure YOUunderstand the solution

Report allowed …but handed in reportMUST be YOUR own work

Quizzes f orbidden - will be heavily penalized

Exams f orbidden - will be heavily penalized

“allowed” means that you are free to ask advice or opinions when doing problems & planning your report. However the final work must be all your own (& fully understood by you)

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

My “Rules” - Plagiarism/Citations

I n Class Citations not required

Homework Correct/honest citations requiredfor marked homework only

Report Correct/honest citations absolutelyrequired

Quizzes Citations not required(unless specifically asked)

Exams Citations not required(unless specifically asked)

UMBC does have the facilities to check for plagiarism and I will use them !

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

What YOU can Expect from meMy presentation will be via a combination of overheads, web-based info & some video PLEASE - tell me if I go too fast - ask me if I am not clear

Course background info & notes will be accessible in the WWW:

http://astsun.astro.virginia.edu/~jh8h/Foundations/contents.html However these notes are NOT guaranteed to be be complete, and in fact often contain background information not directly examinable

Accessibility - I am happy to discuss any problems or uncertainties You may have - however E-mail is by far the best means of contact turner@lucretia.gsfc.nasa.gov (remember I spend a fraction of my time at NASA/GSFC)

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Web Based TutorialsThis class has an account for some online tutorials at-

http://www.aw.com/astronomyplace

Login name - tjturnerPassword - physics316 First tutorial: Chapter 1, section 1.2 “Scales of the Universe”

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

START OF THE COURSE…

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Course Overview - Topics

Part 1: A Review of Early Cosmological Ideas also - a recap of some basic astronomy stuff

Part 2: Galaxies. Cosmic Distance Ladder

Part 4: Dark Matter

Part 5: Review of the current (Big Bang) paradigm

Part 6: Nucleosynthesis & Alternatives to the Big Bang

Part 7: The Early Universe, and its Evolution

Part 3: Special and General Relativity, Black Holes

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Part 1: Early Cosmological Ideas

Topics:

Introduction The Birth of "Scientific" Cosmology Aristotle & Ptolemy The "State of the Universe" for the Greeks The "Dark" Millennium The Recovery of W. European Science

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

IntroductionThe word Cosmology is from the Greek kosmos (world) and logia (from legein: to speak).

All civilizations (probably) developed some form of "cosmology". Indeed all civilizations (we know about) seem to have "Creation myths" of some sorts.

In the earliest civilizations (& up to very recent times) cosmology was primarily (often totally) a branch of religion/myth.

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Astronomy-the 2nd Profession ?

Certainly many (all ?) ancient civilizations performed astronomical observations of various levels of sophistication - from the neolithic observatories (eg.Stonehenge), to written reports

(eg. The Chinese, Egyptians, etc).

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

..a little humility required ?

AND we should not underestimate the struggles/difficulties early thinkers had attempting to explain the universe within their various cultural, religious & technological environments….

Many earlier beliefs & models may seem "silly" or "absurd" now. Our beliefs and our scientific methods are "clearly far superior" - aren't they ?

However it worth reminding ourselves from the very start that we have not figured everything out yet !! (dark matter, cosmic acceln, WHIMPs, MACHOS etc)

Many variations on Mythological/Cosmological Ideas, but many with themes not so different from our own:

Cosmic Birth Myths Big Bang

Sages, Shamen… Newton, Einstein, Hawking

Unseen Forces/laws Gravity, Weak, Strong etc

Unchangeable destiny Unchangeable destiny

Whims of the Gods Ultimately understandable

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

..a little humility required ?

Imagine life before telescopes…

Earth seems flat and motionlessSun, Moon, planets, stars move in sky (East to West)Strange things appear (comets, meteors)

The Greeks are generally credited with promoting the idea that the universe was understandable using logic, and could be described by mathematics. This is a huge leap forward, and the basis of all science today

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Birth of "Scientific" Cosmology

By ~400BCE, generally thought that the universe worked & evolved through "natural" processes that can be observed on Earth....Divine intervention is not required (at least in the "running" of the universe).

Cosmology was really a branch of philosophy at the time, but the Empirical Scientific Method was developing.

Consensus - there are no limits to what can be observed & understood (again, at least not concerning the "running" of the universe), theories could be postulated, predictions made, theories revised as necessary

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Birth of "Scientific" Cosmology

The Greeks understood that the Earth is a sphere:- Observation of ships sailing over the horizonObservation of Earths shadow on the moon during lunar eclipses

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Geocentric Spheres

Only five planets were known to the Early Greeks (Mercury, Venus, Mars,Saturn, Jupiter). Thus early Greek cosmologists believed they had to account for 8 celestial entities -the 5 planets, the Sun, the Moon, and the "Stars".

Cosmologies were all "naturally"

Geocentric (centered on the Earth)

Cosmologies generally included

perfect spheres

(Sphere count: Pythagoras of Samos,(c.530BCE) 8)

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Aristotle (c.350BCE)

The physical universe was finite - beyond the outer sphere of the stars was the (non-material) spiritual realm.

Reasoned that that this "universe" must be unique (& have a single center), and have existed for

eternity (& in a steady-state).

(Sphere count: Aristotle,(c.350BCE) 55)

Believed celestial bodies move in perfect circles

Forced to increase the number of spheres due to refined observations of planetary motion

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Hipparchus (c.125BCE)

Refined distances to (& hence size of) the Moon (via Parallax) ...made the first step determining the scale of the "cosmos"

Suggested that the Sun appeared to be much larger than the Earth....some aesthetic concerns for a geocentric universe … but these are generally ignored (incl by Hipparchus himself).

Constructed a catalog of close to 1000 stars.

Discovered precession (1 degree/century) - the change of the position of the stars with time (now known to be due to the precession of the Earth's axis).

In 134BCE he discovered a new star (a nova), ...in direct contradiction to the paradigm that the "heavens" were unchanging.

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Parallax

Larger parallax = smaller distance

TUTORIAL: MEASURING COSMIC DISTANCESCosmic Perspective Tutorial, Measuring Cosmic Distances

...the apparent change of position of a (closer) object as measured against the positions of more distant object(s) due to the movement of the observer.

A Parsec is defined as the distance of an object that exhibits parallax of 1 arcsec (Easy to remember since the word parsec is a

construction from parallax and arcsec)

1 parsec = 3.085678 x 1016 m = 3.26 light years

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Hipparchus,Parallax & the Moon

Since 20% of the Sun's disk corresponds to 6 arcmins, then by estimating the distance between the citiesone can derive the distance of the Moon.

Hipparchus of Rhodes estimated the distance to the Moon from measurements taken during a solar eclipse in189BCE.

eclipse was "full" in Hellespont (NW. Turkey), partial in Alexandria (Egypt)

20% of the Sun's disk remained visible in Alexandria

Hipparchus estimated distance (4.5 to 5.2) x 108 m (c.f. modern value of 3.8 x 108 m)

First attempt to scale the cosmos

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

So Far…

We very briefly reviewed the development of cosmological ideas culminating with early Greek thinkers, who

reasoned the Universe was formed by natural processes which could be observed, understood/explained by mathematics (Pythagoras of Samos, c.550BCE). Developed the Empirical Scientific Method Developed a geocentric cosmological system (Aristotle,c.350BCE) - the birth of "scientific" cosmology.

We also reviewed the concept of Parallax

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Ptolemy (c.150)

His (13 volume) master work Megale Syntaxis ("Great Compilation") Is usually known as by the arab translation Almagest ("The Greatest")

Extended the system of Aristotle, sticking "religiously" to the ideas of a geocentric cosmology, the perfection of spheres a finite universe.

(There is an on-going debate whether he stole/plagiarized Hipparachus' data !) [e.g. see Schaefer, Sky & Telescope 2002 Feb issue, p39]

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Ptolemy & Epicycles

The key elements are the epicycle to account for the retrograde motion of the planets the deferent (main circle) to account for the brightening & speeding-up of the planets at some times. relative tilts between the various planes,

Large number of parameters (for 8 celestial objects) The “equant” is the point from which ang. vel of epicycle ~const)

(Bothun, Fig1.2)

The model was able to make accurate predictions

Remained the "standard" cosmological model for 1400 years

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Math as a Parameterization

Contrary to the Greek ideas that Nature is simple, perfect, beautiful

In the middle ages some thinkers started suggesting that the Ptolemaic system of eccentrics/epicycles do not actually exist,

...but are merely convenient mathematical descriptions of celestial motion & reality (not reality itself)

Note: The concept of Nature being simple, perfect, beautiful can be argued to be back with some modern theories (!)

eg Ibn Rushd alHafid, (aka Averroes, c.1150) Roger Bacon (c.1250)

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

The Ptolemy Monopoloy

Alan W. Hirshfeld, in "Parallax - The Race to Measure the Cosmos"

“In a sense, Ptolemy was the Bill Gates of his day. His Ptolemaic "operating system", despite its known deficiencies, grew to dominate - in fact, monopolize - the astronomical market place."

Lecture 1Jane Turner [4246] PHY 316 (2003 Spring)

Rise of the Scientific Method

The modern Scientific Method

observations, theory, predictions, tests/revisions...

is (re)invented & developed (Ibn al-Haytham, aka Al-Hazen, c.1000).

William of Ockham (or Occam; c.1300) suggests entities should not be “multiplied unneccessarily”, leading to (interpreted as) Ockham's Razor: the simplest (most succinct) theory is more likely to be correct, and certainly a better working model (to attempt) to disprove first.

Roger Bacon (c.1250) helps popularize the scientific method in W.Europe,