Transcript Introduction

Introduction
Dr Ken Rice
Astronomy 1G
Welcome
Dr Avery Meiksin
Dr Ken Rice
Dr Mike Hawkins
[email protected]
(Course Organiser)
[email protected]
[email protected]
Astronomy 1G
Astronomy 1G : Galactic and Cosmological Science
This is an introductory Astrophysics course in which you will apply basic physics
technique to astrophysical situations. This course will focus on the large scale
universe and will discuss, amongst other things, black holes, galaxies and
cosmology.
The Astronomy 1S course does not follow
a single textbook closely. Some suitable
books are ”Introductory Astronomy and
Astrophysics” by M. Zeilik and S.A.
Gregory. Some material may come from
“The Cosmic Perspective” by Bennett,
Donahue, Schneider and Voit.
Astronomy 1G
Online course material
The course homepage can be accessed by registered students through the
MyEd portal https://www.myed.ed.ac.uk/. The website will include course
material and copies of the lecture notes. All notices, announcements, and
assessment grades will also be posted on this website, and there will be a
discussion board allowing students to ask questions about the course or
provide feedback.
The website also contains a link to the registration form that must be completed
so that tutorial groups can be arranged.
Astronomy 1G
Tutorials
Each student will attend a total of 5 tutorials, 1 every 2 weeks. Tutorials
will be held on Mondays and Fridays from 15.00 to 15.50, and students
will be divided into groups during the first week. You must fill out a
registration form to be assigned to a tutorial group.
During these tutorial sessions, you will work in groups to answer
questions that will be similar to those that you will see in the exam. At the
end of each two week period you will hand in your solutions and two of
these solutions will be assessed. The best 4 tutorial marks out of 5 will
count towards your final degree mark. You are encouraged to hand in all 5
sets of tutorial solutions, but by using the best 4 out of 5 means that
students can miss one tutorial, if necessary, without being penalised. The
tutorial deadlines will generally be the first lecture on the Monday after the
final tutorial of each two week period. The exact dates of these lectures
are shown in the timetables at the end of this booklet. We will not
accept work that is handed in after these deadlines.
Astronomy 1G
Assessed Coursework
In addition to the tutorials, you will be asked to do one piece of coursework that will
be assessed. Details of the assignment (which may be essay, poster or numerical
work) will be given several weeks in advance. You will have a choice of options for
each assignment.
You must complete the coursework and hand it in on time. It will be marked and
returned to you; there is a marking penalty of 5% per working day, for five days,
with a mark of zero thereafter, for late work. The assessed coursework is
included in the final mark for the course. This means that any marks lost for
late coursework make it harder to pass the course.
You must include a “Own Work Declaration” when handing in the coursework. A
mark will not be given if this form is not signed and returned with your work. The
form is available from the course webpage on WebCT or can be downloaded from
the School’s website.
Astronomy 1G
Observing
Free tickets for the Visitor Centre’s public observing sessions on Friday
nights will be able for first-year students interested in some stargazing
and perhaps thinking about getting involved in outreach work. These
tickets are limited and booking is essential. Contact the Visitor Centre
(0131-6688404, 2-4pm, [email protected]).
Astronomy 1G
What is required to pass the course
At the end of the course there will be a two-hour exam consisting of a multiple
choice section, a short questions sections, and a problem-solving/long questions
section.
The course grade will depend on the degree exam, the coursework mark, and the
tutorial marks. To the pass the course you will need an overall pass mark (40%
on the University Common Marking scale) and you must score a minimum of 35%
on the Degree Examination itself. The overall pass mark is calculated from:
2/3 examination
1/6 coursework assignment
1/6 assessed tutorial problems
Astronomy 1G
Astronomy 1G: Galactic and Cosmological Science
7 January to 21 March
Monday 14.00 Appleton Tower, Theatre 1
Monday 16.10 Appleton Tower, Theatre 1
Friday 14.00 Appleton Tower, Theatre 1
Week
1
2
3
4
5
6
7
8
9
10
Date
7 Jan
11 Jan
14 Jan
18 Jan
21 Jan
25 Jan
Day/Time
M2, M4
F2
M2, M4
F2
M2, M4
F2
28 Jan
M2*, M4
1 Feb
4 Feb
8 Feb
11 Feb
F2
M2, M4
F2
M2*, M4
15 Feb
18 Feb
22 Feb
25 Feb
F2
M2, M4
F2
M2*, M4
29 Feb
3 Mar
7 Mar
10 Mar
F2
M2, M4
F2
M2*, M4
14 Mar
17 Mar
21 Mar
14-23 Apr
F2
M2, M4
F2
Module
Science of Astronomy
Science of Astronomy
Science of Astronomy
Science of Astronomy
The Milky Way and Galaxies
The Milky Way and Galaxies
Coursework assignment set: Monday 28 Jan.
The Milky Way and Galaxies
*28 Jan, M2: Tutorial 1 deadline.
The Milky Way and Galaxies
Active Galaxies and Black Holes
Active Galaxies and Black Holes
Active Galaxies and Black Holes
*11 Feb, M2: Tutorial 2 deadline.
Active Galaxies and Black Holes
The Distribution of Galaxies
The Distribution of Galaxies
The Distribution of Galaxies
*25 Feb, M2: Tutorial 3 deadline.
Coursework deadline: Friday 29 Feb.
The Distribution of Galaxies
Cosmology
Cosmology
Cosmology
*10 Mar, M2: Tutorial 4 deadline.
Cosmology
Short practice exam in M2, feedback in M4.
21 Mar, F2: Tutorial 5 deadline.
Exams.
Astronomy 1G
Lecturer
Dr WKM Rice
Dr M Hawkins
Dr A Meiksin
Dr M Hawkins
Course Modules
• The Science of Astronomy
• The Milky Way and other Galaxies
• Active Galactic Nuclei
• The Distribution of Galaxies
• Cosmology
EXAMS !
Astronomy 1G
The Science of Astronomy
Astronomy 1G
Ancient Observations
•
Not much light pollution
– Ancient civilisations were probably much more aware of the night sky than we are
today.
•
Middle Eastern Astronomers had watched the night sky for thousands of years
– Eclipses
– The motion of the planets
– Patterns in the night sky and how they changed during the year
Astronomy 1G
Ancient Astronomy
•
Nearly all ancient civilisations practised astronomy at some level
– Time of day or night
– Seasons
•
Lunar calenders
– Origin of months
– Lunar year 11 days shorter than a solar year.
– Metonic cycle (discovered by Meton in 432 B.C.)
• On a solar calender, the lunar phases repeat every 19 years
Astronomy 1G
Using the Moon
•
The orientation of the crescent moon varies with season.
– We know today that this is caused by the relative position of the Sun and moon at
different times of the year.
•
Central Africans would use this to predict rainfall.
– They did not need to know why, they simply had observed for long enough to notice
the pattern.
Astronomy 1G
Scientific Method
•
What is science?
– science is the process by which we try to understand the world around us
• Science is quantitative
– definitive not vague
– criteria for testing
•
This is, surprisingly, a recent activity
– Many Ancients civilisations believed the world worked “through the actions of the
Gods”
– Ancient Greeks were the first people who tried to explain the motions of astronomical
objects without resorting to the supernatural.
•
Theory
– is the endpoint of science – provides an explanation
– it must be consist with existing observations
– and, be able to predict testable results
•
Experimentation
– explore and discover
– test theories
Astronomy 1G
Ancient Greek Astronomy
•
•
Thales (624 – 546 B.C.) and Anaximander (610 – 546 B.C.) 2 of the earliest
Greek Astronomers.
Pythagoras (560 – 480 B.C.)
– Earth is a sphere floating at the centre of the celestial sphere.
– Spheres were perfect and therefore were the basic shape of the heavens.
• Geocentric model
–
Plato – all heavenly bodies move in perfect
circles at constant speeds.
–
Even in Plato’s day, Greek observers knew
this was wrong.
– Retrograde motion.
– Why did Mercury and Venus remain so
close to the Sun.
Astronomy 1G
Ptolemy (100 -170 B.C.)
•
•
Based his models on that of
Hipparchus (190-120 B.C.)
Still placed the Earth at the centre
– Introduced small circles (epicycles)
upon a larger circle (deferent).
– Moved the centre of the deferent
away from the Earth.
– Introduced equants – centre of
epcicyle moved with constant
speed relative to the equant.
•
Ptolemy’s work was remarkably
accurate.
Centre of deferent
x
Equant
– Could predict planetary positions to
within a few degrees.
– Remained in use for 1500 years
until Copernicus (1473-1543)
suggested a Heliocentric model for
the Universe.
Astronomy 1G
Geocentric model
• Ptolemy (1st century AD) supported the
geocentric (earth centred) model of the
universe.
• This could explain a number of
observations
- The nightly rotation of the stars
- The simple motion of the planets
- The lack of motion of the stars relative
to each other
- Phases of the moon
- Eclipses
• Could not explain
- Why Venus and Mercury stayed so
close to the Sun.
Astronomy 1G
Renaissance
•
Despite the advances of Greek science, it had some shortcomings
– A theory was right if it produced the correct answer.
– Very little or no experimentation
• Arostotle assumed that heavy objects had to fall faster than light objects.
• Galileo (1564 – 1642) revolutionised science
– Developed mechanics and studied how objects
moved
– His approach is at heart of modern science.
– Also invented the telescope and made
observations that supported the Heliocentric model
of the Universe.
Astronomy 1G
The Heliocentric model
•
•
Although not supported in Galileo’s days, Galileo’s observations provided
evidence for a Heliocentric rather than Geocentric model
Invented the telescope in 1608
– Sunspots - Sun not perfect
– Mountains and craters on the moon – not a perfect sphere
– Moons of Jupiter – not everything orbits the Earth.
Astronomy 1G
The Heliocentric Model
• Nicholas Copernicus (1473 – 1543)
proposed a Heliocentric (Sun
centred) model for the universe.
- The centre of the universe is near
the Sun.
- The distance from the Earth to the
sun is tiny compared with the
distance to the stars.
- The rotation of the Earth accounts
for the apparent daily rotation of the
stars.
- The apparent annual cycle of
movements of the sun is caused by
the Earth revolving round it.
- The apparent retrograde motion of
the planets is caused by the motion
of the Earth from which one
observes.
Astronomy 1G
Retrograde motion
• Copernicus correctly stated that the
farther a planet lies from the Sun, the
slower it moves around the Sun.
• The Earth can therefore pass an outer
planet during its orbit.
• When this occurs, the outer planet will
appear to reverse its motion for a short
time
- The retrograde loop.
Astronomy 1G
Newton (1642-1727)
•
One of greatest scientist ever
– Studied light and built telescopes
•
His greatest contribution was the Principia Mathematica
– Laws of Motion and the Theory of Gravity
Astronomy 1G
Astrophysics
•
Generally can’t do experiments in the traditional sense
•
Primarily relies on observations
– Still requires a measurement
• Probes to planets, moons and comets
• Direct measurements of interplanetary space
• Collect radiation from galactic and extra-galactic sources
– Experimentation, but not controlled.
– Requires an understanding of the underlying physics
• Mechanics
• Radiation and matter
•
Astrophysics is not a fundamental science
– Application of physics to understand objects in the Universe.
Astronomy 1G
What Science do we need to know
•
Gravitational dynamics
– Planetary orbits
– Binary stars
– Galaxy rotation
•
Doppler effect
– Determine velocities and together with gravitational dynamics determines masses
– Expansion of the Universe
•
Blackbody radiation
– Temperatures
•
Spectra
– Temperatures and composition
– Type of star/galaxy
– Can be then used to determine distances
Astronomy 1G
Some useful numbers
Astronomical unit (pc) :
1 parsec (pc) :
Speed of light (c) :
1.5 x 1011 m (Sun Earth distance)
3 x 1016 m
3 x 108 m
distance light travels in a year (nearest star – apart from
Sun)
1 light second :
distance to the moon
8 light minutes :
distance to the Sun
1 light hour :
distance across solar system
25 thousand light years : distance across the galaxy
150 thousand light years : distance to the Magellanic galaxies
1 million light years :
distance to M31 (nearest big galaxy)
1000 million light years : “size” of universe
1 light year :
Astronomy 1G