Transcript Introduction to Astronomy

Introduction to Astronomy
 Instructor: Dr. Elizabeth Charlton
 Meeting times: Thursdays, 7:00pm-9:00pm for 10 weeks beginning
October 6, 2016
 Meeting place: Ewert House (HERE)
 Contact information
direct email: [email protected]
weekly class office: [email protected]
Course details can also be found at the Oxford
University Department for Continuing Education
website:
https://www.conted.ox.ac.uk/
Elizabeth Charlton 2016
Introduction to Astronomy
Formal Assessment
Formative coursework – the instructor will give
written comments in order to provide guidance to
students on how to approach their formally
assessed coursework.
Summative coursework – The assessment
method for this course will be Option A, a
portfolio of four exercises designed to reinforce
the concepts presented in class.
Elizabeth Charlton 2016
Introduction to Astronomy
Libraries and Reading List
 All weekly class students may become borrowing members of the
Rewley House Continuing Education Library for the duration of their
course. Prospective students whose courses have not yet started
are welcome to use the Library for reference.
 Background Reading:
Tyson, N., Liu, C., Irion, R. - Our Universe: At Home in the Cosmos
Hartmann, W.K. - Moons and Planets
Green, S.F., Jones, M.H. - An Introduction to the Sun and Stars
Freedman, R. Geller, R. Kaufmann, W.J. - Universe
Elizabeth Charlton 2016
Course News Letter
 Each week I will send a course news letter to your
provided email address.
 The news letter will provide course reminders, links to
the lecture slides, astronomical observing
opportunities, answers to questions we didn’t get to in
class, etc.
 If you do not wish to provide an email address I can
give you a hard copy of the news letter in class.
Elizabeth Charlton 2016
Introduction to Astronomy
Lecture 1
Introduction: A Brief History and
Constellations, Size Scales of the
Universe
Elizabeth Charlton 2016
What is Astronomy?
Your thoughts?
Astronomy is the study of the universe.
What does this include?
“No, but that’s what
you do. The human
race. Making sense
out of chaos.”
- The 10th Doctor
Dr. Who
Elizabeth Charlton 2016
Credit: STS-82 Crew, STScI, NASA
Research in Astronomy
Many research areas:
Earth
Planets
Solar System Objects
Stars
Galaxies
The Universe as a Whole
… and many more
Credit: Apollo 17 Crew, NASA
Credit: VLA, NRAO
Credit: NASA
Credit: NASA, ESA, HEIC, and The Hubble Heritage Team
(STScI/AURA)
Credit: NASA, ESA, S. Beckwith (STScI), and The
Hubble Heritage Team (STScI/AURA)
Credit: R. Williams, The HDF Team (STScI), NASA
Elizabeth Charlton 2016
"FullMoon2010" by Gregory H. Revera - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0 via
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apod.nasa.go
A Brief History…
Elizabeth Charlton 2016
"Cosmic Calendar" by User:Efbrazil - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0 via
Wikimedia Commons http://commons.wikimedia.org/wiki/File:Cosmic_Calendar.png#mediaviewer/File:Cosmic_Calendar.png
31 DEC, 23:59:48
The Immergence of Astronomy
 Ancient cultures from around
the world develop the
fundamentals of Astronomy
through naked-eye
observation
 Early Observatories
 Mapping the positions of the
Sun, planets, stars, moon, etc.
and observing daily and annual
motion
 Observations of Eclipses
 Moon Phases
 Constellations (for example:
the Zodiac)
 Often associated with religious
observation
Arny, 3rd Edition,
Chapter 1
Elizabeth Charlton 2016
Constellations

What are they? (definition)
Recognized grouping of stars
 Officially recognized grouping of stars

Elizabeth Charlton 2016
Official Constellations

Who is responsible?


IAU (International Astronomical Union)
How many are there?
88
 Recognized since 1922
 Based on the 48 listed in Ptolemy’s Almagest

Elizabeth Charlton 2016
Asterisms

Unofficial groupings of stars

Examples:
Big dipper
 Pleiades
 ...

Elizabeth Charlton 2016
Cultural History
Many stories from many cultures
 Many names come from Greek and Roman
myths
 Many star names from Arabic

Elizabeth Charlton 2016
Representations

In the night sky it
can be hard to see
patterns
Artistic

Helps to see pictures
Stick figures

Shows basic picture

Takes some
imagination
Boundaries
Official regions for each constellation
 Includes whole sky

Naming

Official name


Orion
Abbreviation(3 letters)


Canis Major
CMa
Ori
Common name

Big Dog
Hunter
Elizabeth Charlton 2016
31 DEC, 23:59:55
Ptolemaic Astronomy
 Claudius Ptolemaeus or
Ptolemy of Alexandria
 Work described in
Almagest (c. AD140)
 Developed geocentric
model of the universe
based on the teachings of
Aristotle
 Earth at center
 Heavenly bodies move in
perfect uniform motion
with the perfect curve
being a circle
"Ptolemaeus" by This file is lacking author information. - This file is lacking source information.Please edit this
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Elizabeth Charlton 2016
31 DEC, 23:59:55
Ptolemaic Astronomy
Problems with the Ptolemaic Geocentric
Model:
Simple circular paths centered on the Earth did
not correctly predict the positions of the planets.
Did not explain retrograde motion of planets.
Elizabeth Charlton 2016
Arny, 3rd Edition, Chapter 1
31 DEC, 23:59:55
Ptolemaic Astronomy
Epicycles
Preserved uniform motion in the geocentric
model
Predicted positions of the planets with fair
accuracy
Over centuries the many errors accumulated
Elizabeth Charlton 2016
31 DEC, 23:59:58
Astronomy During the Renaissance
Nicolaus Copernicus
(1473-1543) proposed
heliocentric model of
the universe
 Sun at the centre
 Earth rotated on its
axis
 Explained
retrograde motion
and provided
symmetry
 Published work in De
Revolutionibus Orbium
Coelestium
"Nikolaus Kopernikus" by Unknown - http://www.frombork.art.pl/Ang10.htm. Licensed under Public
domain via Wikimedia Commons http://commons.wikimedia.org/wiki/File:Nikolaus_Kopernikus.jpg#mediaviewer/File:Nikolaus_Koperniku
s.jpg
Elizabeth Charlton 2016
31 DEC, 23:59:58
Astronomy During the Renaissance
Copernican model better
explained the retrograde
motion of the planets.
It is a natural consequence of
one
planet passing another.
Elizabeth Charlton 2016
Arny, 3rd
Edition,
Chapter 1
31 DEC, 23:59:58
Astronomy During the Renaissance
 Problems with Copernican model:
Preserved the concept of uniform circular motion.
Did not predict the positions of the planets any better.
Did not explain lack of parallax motion of the stars.
Elizabeth Charlton 2016
Arny, 3rd Edition, Chapter 1
31 DEC, 23:59:58
Astronomy During the Renaissance
 Tycho Brahe (1546-1601)
 Built extremely accurate
instruments for
astronomical observation
Naked-eye observations
along sights on large
instruments
Proposed compromise
“geo-heliocentric” model
because he also could not
detect star parallax
Hired Johannes Kepler as
his assistant
"Tycho Brahe" by Eduard Ender († 1883) - http://cache.eb.com/eb/image?id=83677&rendTypeId=4.
Licensed under Public domain via Wikimedia Commons http://commons.wikimedia.org/wiki/File:Tycho_Brahe.JPG#mediaviewer/File:Tycho_Brahe.JPG
Elizabeth Charlton 2016
31 DEC, 23:59:58
Astronomy During the Renaissance
Johannes Kepler (15711630)
Received Tycho Brahe’s
data after his death
Studied the motions of
Mars
Formulated Kepler’s Laws
of planetary motion
Published work in
Astronomia Nova
"Johannes Kepler 1610" by Unknown - Kopie eines verlorengegangenen Originals von 1610 im
Benediktinerkloster in Kremsmünster. Licensed under Public domain via Wikimedia Commons http://commons.wikimedia.org/wiki/File:Johannes_Kepler_1610.jpg#mediaviewer/File:Johannes_Kepler_
1610.jpg
Elizabeth Charlton 2016
31 DEC, 23:59:58
Kepler’s Laws
Observed that when the positions
of the planets were converted
from positions relative to the
background stars to positions
relative to the Sun that they did
not exhibit uniform circular
motion.
1st Law
Planets move in elliptical orbits with
the Sun at one focus of the ellipse
Elizabeth Charlton 2016
Arny, 3rd
Edition,
Chapter 1
31 DEC, 23:59:58
Kepler’s Laws
Observed that planets move faster when
closer to the sun and slower when further
away.
2nd Law
The orbital speed of a planet varies so that a line
joining the Sun and the planet will sweep out
equal areas in equal time intervals
Elizabeth Charlton 2016
Arny, 3rd Edition, Chapter 1
31 DEC, 23:59:58
Kepler’s Laws
Observed that the individual planets
did not orbit the sun at the same
speed. The closer orbited faster and
the further planets orbited slower.
3nd Law
 The amount of time a planet takes to orbit the Sun is related
to its orbit’s size, such that the period, P, squared is
proportional to the semimajor axis, a, cubed:
P2 ∝ a3
where P is measured in years and a is measured in AU
Elizabeth Charlton 2016
Arny, 3rd
Edition,
Chapter 1
31 DEC, 23:59:58
Astronomy during the Renaissance
Galileo Galilei (15641642)
Made observations
using the telescope
Did not invent the
telescope
Observations seemed to
confirm Copernican
model
"Justus Sustermans - Portrait of Galileo Galilei, 1636" by Justus Sustermans http://www.nmm.ac.uk/mag/pages/mnuExplore/PaintingDetail.cfm?ID=BHC2700. Licensed under Public
domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Justus_Sustermans__Portrait_of_Galileo_Galilei,_1636.jpg#mediaviewer/File:Justus_Sustermans__Portrait_of_Galileo_Galilei,_1636.jpg
Elizabeth Charlton 2016
31 DEC, 23:59:58
Astronomy during the Renaissance
 Galileo’s Observations
 An imperfect Moon
 Phases of Venus
 An imperfect Sun (Sunspots)
 Moons of Jupiter
 Multitude of stars in the Milky Way
Arny, 3rd Edition,
Chapter 1
Elizabeth Charlton 2016
31 DEC, 23:59:59
The Advent of Modern Astronomy
 Isaac Newton (16421727)
 Made major advances in
the subjects of physics,
mathematics, and
astronomy
 Formulated Calculus
 Developed the Laws of
Motion
 Developed the theory of
Gravity
 Published work in
Philosophiæ Naturalis
Principia Mathematica
"GodfreyKneller-IsaacNewton-1689" by Sir Godfrey Kneller http://www.newton.cam.ac.uk/art/portrait.html. Licensed under Public domain via Wikimedia Commons
- http://commons.wikimedia.org/wiki/File:GodfreyKneller-IsaacNewton1689.jpg#mediaviewer/File:GodfreyKneller-IsaacNewton-1689.jpg
Elizabeth Charlton 2016
31 DEC, 23:59:59
The Advent of Modern Astronomy
 Newton’s Theory of Gravity
 Gravity is the force of attraction between two masses.
 The mass of an object is the fundamental measure of the amount of
matter in an object (usually given in kg).
 The force of gravity is directly proportional to the product of the
masses of the two objects and indirectly. proportional to the square of
the distance between them.
G = 6.7 x10 11 Nm2/kg2 is
the gravitational
constant
"NewtonsLawOfUniversalGravitation". Licensed under Creative Commons Attribution 3.0 via Wikimedia
Commons Elizabeth Charlton 2016
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onsLawOfUniversalGravitation.svg
Our Place in the Universe
Elizabeth Charlton 2016
Earth Statistics
Mean Radius = 6.4x103 km = 1R⊕
Volume = 1.1x1012 km3 = 1V⊕
Mass = 6.0x1024 kg = 1M⊕
Density = 5.5 kg/m3
Distance from Sun = 1.5x108 km = 1AU
Elizabeth Charlton 2016
Image Credit: NASA/JPL
Size Scales
3.8x10-1
R⊕
5.6x10-2 V
⊕
5.5x10-2 M⊕
Elizabeth Charlton
2016
5.3x10-1R⊕
1.5x10-1V⊕
1.1x10-1M⊕
9.5x10-1R⊕
8.6x10-1V⊕
8.1x101M
⊕
1R⊕
1V⊕
1M⊕
"Star-sizes" by Dave Jarvis (http://www.davidjarvis.ca/) - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0 via
Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Star-sizes.jpg#mediaviewer/File:Star-sizes.jpg
Size Scales
1
3.9R⊕
58V⊕
17M⊕
Elizabeth Charlton
2016
4.0R⊕
63V⊕
14M⊕
9.1R⊕
7.6x102V⊕
95M⊕
11R⊕
1.3x103V⊕
3.1x102M⊕
"Star-sizes" by Dave Jarvis (http://www.davidjarvis.ca/) - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0 via
Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Star-sizes.jpg#mediaviewer/File:Star-sizes.jpg
Sun Statistics
Mean Radius = 7.0x105km =
1.1x102R⊕ = 1R⦿
Volume = 1.4x1018km3 =
1.3x106R⊕ = 1V⦿
Mass = 2x1030kg = 3.3x105M⊕
= 1M⦿
Elizabeth Charlton 2016
0.16R⦿
1.7x10-2V⦿
0.09M⦿
Elizabeth Charlton 2016
1R⦿
1V⦿
1M⦿
1.7R⦿
21V⦿
2.2M⦿
"Star-sizes" by Dave Jarvis (http://www.davidjarvis.ca/) - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0 via
Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Star-sizes.jpg#mediaviewer/File:Star-sizes.jpg
1.7R⦿
21V⦿
2.2M⦿
Elizabeth Charlton 2016
8.8R⦿
2.8x103V⦿
2.0M⦿
26R⦿
7.4x104V⦿
1.1M⦿
44R⦿
3.6x105V⦿
1.7M⦿
"Star-sizes" by Dave Jarvis (http://www.davidjarvis.ca/) - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0 via
Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Star-sizes.jpg#mediaviewer/File:Star-sizes.jpg
44R⦿
3.6x105V⦿
1.7M⦿
Elizabeth Charlton 2016
79R⦿
2.1x106V⦿
21M⦿
8.8x102R⦿
2.9x109V⦿
12M⦿
Range: 9.5x102 – 1.2x103R⦿
Range: 3.6x109 – 7.2x109V⦿
Range: 7.7 – 20M⦿
"Star-sizes" by Dave Jarvis (http://www.davidjarvis.ca/) - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0 via
Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Star-sizes.jpg#mediaviewer/File:Star-sizes.jpg
Range: 9.5x102 –
1.2x103R⦿
Range: 3.6x109 –
7.2x109V⦿
Range: 7.7 –
20M⦿
Elizabeth Charlton 2016
Radii and Masses for the Red Supergiant and Hypergiant stars above are
difficult to constrain due to considerations such as mass loss. Estimates range
from R=6.5x102 – 1.9x103R⦿, V=1.1x109 – 2.9x1010V⦿, and M=17 – 25M⦿
"Star-sizes" by Dave Jarvis (http://www.davidjarvis.ca/) - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0 via
Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Star-sizes.jpg#mediaviewer/File:Star-sizes.jpg
Size Scales
Elizabeth Charlton 2016
"Sun and VY Canis Majoris" by User:Mysid - Self-made in Inkscape.. Licensed under Public domain via Wikimedia Commons http://commons.wikimedia.org/wiki/File:Sun_and_VY_Canis_Majoris.svg#mediaviewer/File:Sun_and_VY_Canis_Majoris.svg
Our Place in the Universe
Looking into the past:
Speed of Light = c = 3x105km/s
(1.86x105 miles/s)
1 light-year = 9.5x1012km
(5.9x1012miles) = the distance light travels
in 1 year
Video: Powers of Ten
Elizabeth Charlton 2016
http://yalebooks.files.wordpress.com/2012/05/universe© YALE UNIVERSITY PRESS 2014
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