Time to face the decider, the exam for this course where all hopes and aspirations live or die.
After getting to the exam centre in plenty of time, and finding my seat and unloading all my stuff on the desk, and then having forgotten my watch and had to go back to the bag dumping ground to fetch it, I started on the admin tasks of filling in all the ids and stuff on the answer book.
Then one of the invigilators came over to the two of us taking this exam and gave us a couple of corrections to the exam paper. Basically a couple of the multi choice answers were telling you to pencil in the wrong rows.
Then it was time to start. Eight multiple choice questions that all have to be answered. Some of them are ok, work out a value and tick the right box. Others are much more tricky given eight statements and pick out the two right ones or two wrong ones. These are tricky as sometimes it all hinges on one word. Some most of the sentence is correct, but a small word somewhere like always can make the whole thing untrue.
Then part 2 - four questions, answer 3 - mostly on the life and death of stars, and often something specific about the Sun.
Part 3 - four more questions, answer 3 - this time on galaxies and cosmology.
I got through the multi choice in about 20 minutes, the paper says to allow 50, but there were 3 of these that I wasn't very sure about and didn't have a good answer, so I left them hoping inspiration might strike.
Then I did 3 of part 2, and followed by 3 of part 3. Then back to part 1 again and this time narrowed it down to at least the right number of answers. Some of them I just couldn't get to gel, and had to guess between two possibilities. Then I still had 30 minutes time, and as they take the best marks from section 2/3 (allegedly anyway) I did the two question I hadn't done, as it filled in the time.
I got stuck on one of them, when I couldn't find the equation for rotational mass/velocity to derive the weight of a black hole. I tried first working it out in terms of an unknown which you needed for the next part, so it would end up as something like 3.4 * M (where M is the answer I couldn't work out for the previous part).
However at some point the equation more of less jumped into my head, and after working the numbers the result didn't look out of place, so I went with it and gave a figure for an answer.
So now - over to the markers - hope they can read my scrawl!
Showing posts with label S282. Show all posts
Showing posts with label S282. Show all posts
Friday, 17 October 2008
Wednesday, 1 October 2008
S282: CMA
This is the last bit of coursework for S282, and it doesn't actually matter. Its informational to give you practice in filling in a Computer Marked Assignment, which is what will have to be done in the exam.
There are 12 questions in all, each with several possible answers - typically A-H. Sometimes there is just one right answer, sometimes two or three. The questions vary across the whole spectrum of the course, and are pretty tough in places.
Some get you to do a calculation and see if there is an answer that matches. Sometimes these are a little tricky, like working out energy and some of the answers are in joules, and some in electron-volts. So you have to calculate both potentially.
Others try and catch you out - asking you which is a true statement out of the 8 given. However at first glance at least 4 of them look correct, and then its looking for detail words like all, or always. These are sometimes a giveaway like "All stars of the mass of the Sun have the same luminosity".
Anyway, it takes a while but it got there. So now - just the scary exam.
There are 12 questions in all, each with several possible answers - typically A-H. Sometimes there is just one right answer, sometimes two or three. The questions vary across the whole spectrum of the course, and are pretty tough in places.
Some get you to do a calculation and see if there is an answer that matches. Sometimes these are a little tricky, like working out energy and some of the answers are in joules, and some in electron-volts. So you have to calculate both potentially.
Others try and catch you out - asking you which is a true statement out of the 8 given. However at first glance at least 4 of them look correct, and then its looking for detail words like all, or always. These are sometimes a giveaway like "All stars of the mass of the Sun have the same luminosity".
Anyway, it takes a while but it got there. So now - just the scary exam.
Monday, 22 September 2008
S282: TMA-4
Its the last of the TMAs for this course. This is probably one of the more scary ones, as I found the first book much easier to digest in terms of concepts and ideas than book 2. Anyway, onwards...
It starts, conventionally enough, with question 1.
This consists of an image of a galaxy, and a spectral diagram of the same, and then there are a variety of questions on it. Firstly, just from the image you are asked to work out if you think this is a regular or active galaxy. Also what galaxy classification would you give to it?
Then there is a collection of data which has to be plotted as a graph to give the spectral signature of the galaxy. Again you have to discuss whether this looks like data from a normal or active galaxy.
The next part asks you to pick between a radio-loud and radio-quiet active galaxy, so rather giving the game away!
Next you have to make some more connections about a small part of the spectrum which is given to you as a graph. Looking at broadening of spectral lines and so on to work out what each shows.
Then some calculations on the broadening values to try and determine velocities.
Finally all the information has to be put together to determine what classification this galaxy is.
Question two is all about cosmology, and FRW models. It starts by getting you to define some FRW assumptions, then to imagine a universe with some given properties, and sketch out how the scale factor would change with time.
Then some algebra and stuff to work out if the curvature of space in this universe is negative.
A couple more calculations of other quantities such as the deceleration parameter and so on.
Then the last part throws in another observation and gets you to refine the model in the light of this new data.
Question 3 is only 5% and just asks you how you plan to revise for the exam. Not really any wrong answers here, although according to the tutor some interesting ideas are forthcoming!
This was a ratehr tough one for me, as cosmology is probably the weaker subject for me, and there hasn't been a lot of time for it to bed down in my mind. Still - its done now. I have a CMA to practice on - which is marked but not assessed, and then its just the exam left.
It starts, conventionally enough, with question 1.
This consists of an image of a galaxy, and a spectral diagram of the same, and then there are a variety of questions on it. Firstly, just from the image you are asked to work out if you think this is a regular or active galaxy. Also what galaxy classification would you give to it?
Then there is a collection of data which has to be plotted as a graph to give the spectral signature of the galaxy. Again you have to discuss whether this looks like data from a normal or active galaxy.
The next part asks you to pick between a radio-loud and radio-quiet active galaxy, so rather giving the game away!
Next you have to make some more connections about a small part of the spectrum which is given to you as a graph. Looking at broadening of spectral lines and so on to work out what each shows.
Then some calculations on the broadening values to try and determine velocities.
Finally all the information has to be put together to determine what classification this galaxy is.
Question two is all about cosmology, and FRW models. It starts by getting you to define some FRW assumptions, then to imagine a universe with some given properties, and sketch out how the scale factor would change with time.
Then some algebra and stuff to work out if the curvature of space in this universe is negative.
A couple more calculations of other quantities such as the deceleration parameter and so on.
Then the last part throws in another observation and gets you to refine the model in the light of this new data.
Question 3 is only 5% and just asks you how you plan to revise for the exam. Not really any wrong answers here, although according to the tutor some interesting ideas are forthcoming!
This was a ratehr tough one for me, as cosmology is probably the weaker subject for me, and there hasn't been a lot of time for it to bed down in my mind. Still - its done now. I have a CMA to practice on - which is marked but not assessed, and then its just the exam left.
Wednesday, 3 September 2008
S282: Book2 - Chapter 8
The last chapter of the book, and it is here where we are treated to some ultimate answers, although as it turns out they are not ultimate answers. However after several chapters of "this constant might be this" and "space might be flat or might not" its nice to have something a little more solid feeling.
Anyway it discusses such topics as
Anyway it discusses such topics as
- What is of dark matter
- What is dark energy
- The horizon and flatness problems
- Where did structure come from
- Why is there matter and not antimatter
- What happened at the big bang
- The anthropic Universe
Monday, 4 August 2008
S282: Book 2, Chapter 5, 6 and 7
In these chapters we get deep into cosmology, and I find it quite heavy going at times. There are the various models of the universe, based on FRW parameters. From these and some other stuff various things are calculated theoretically. This includes the echoes of the big bang, whether space is curved, how fast the universe is expanding and if it is decelerating or not.
Some of this stuff is ok, some is a bit mind blowing. Lots of calculations that you are lead through to predict things like the proportion of hydrogen to helium predicted by the big bang theories.
Then in chapter 7 it considers attempts to measure the Hubble constant, the Hubble Time, the deceleration parameter, the cosmological constant, and the various density parameters.
My head hurts!
Some of this stuff is ok, some is a bit mind blowing. Lots of calculations that you are lead through to predict things like the proportion of hydrogen to helium predicted by the big bang theories.
Then in chapter 7 it considers attempts to measure the Hubble constant, the Hubble Time, the deceleration parameter, the cosmological constant, and the various density parameters.
My head hurts!
Thursday, 10 July 2008
S282: TMA-3
It can't be put off any longer - another TMA to submit.
Question 1 (25%) looks at stellar evolution and reactions - and its in three parts.
Part a) gives you 6 nuclear reactions and then asks a number of true/false type questions. However the joke in the pack is that if you think it is false, you have to give a reason why it is false. So this means getting your reasons in order.
Part b) is similar, in that you are given 8 statements, and told to pick out two that are false, and then explain why they are false. All the questions concern binary star systems in one way or another.
Part c) is another list of 8 statements about stellar evolution, and again pick out the true ones, and explain why the false ones are incorrect.
Question 2 (20%) is split into a-c with subparts for each.
Part a) looks at the stability of stars and you need to draw a diagram showing the forces in balance in a star, then to consider what forces are important in various sized stars.
Part b), with 4 subparts, looks at the collapse of a stellar remnant to a white dwarf and a neutron star and what conditions each are formed in.
Part c) takes the part b) further and introduces black holes into the mix and you have to do some calculations on back hole radii.
Question 3 (18%) looks at supernovae, and its just 4 subparts. Its based around a given table and you need to consider what type or supernova each represents, what they can be used for, and what would happen to the remnant left over.
Question 4 (22%) is a little different in that you are given a spreadsheet of cepheid data from M81 and you have to calculate various equations and end up with a value for its distance. There are a few formulas to rearrange and some averaging to be done, and then some general questions about the results.
Question 5 (20%) is again different in that you have to read one of three recent articles published on the website and then write a short account of its significance
Its not too bad as there is a bit of variety in amongst it, although I found the first question dragged on a bit as I trawled through various pages looking for clear refutation of this point or that.
Question 1 (25%) looks at stellar evolution and reactions - and its in three parts.
Part a) gives you 6 nuclear reactions and then asks a number of true/false type questions. However the joke in the pack is that if you think it is false, you have to give a reason why it is false. So this means getting your reasons in order.
Part b) is similar, in that you are given 8 statements, and told to pick out two that are false, and then explain why they are false. All the questions concern binary star systems in one way or another.
Part c) is another list of 8 statements about stellar evolution, and again pick out the true ones, and explain why the false ones are incorrect.
Question 2 (20%) is split into a-c with subparts for each.
Part a) looks at the stability of stars and you need to draw a diagram showing the forces in balance in a star, then to consider what forces are important in various sized stars.
Part b), with 4 subparts, looks at the collapse of a stellar remnant to a white dwarf and a neutron star and what conditions each are formed in.
Part c) takes the part b) further and introduces black holes into the mix and you have to do some calculations on back hole radii.
Question 3 (18%) looks at supernovae, and its just 4 subparts. Its based around a given table and you need to consider what type or supernova each represents, what they can be used for, and what would happen to the remnant left over.
Question 4 (22%) is a little different in that you are given a spreadsheet of cepheid data from M81 and you have to calculate various equations and end up with a value for its distance. There are a few formulas to rearrange and some averaging to be done, and then some general questions about the results.
Question 5 (20%) is again different in that you have to read one of three recent articles published on the website and then write a short account of its significance
Its not too bad as there is a bit of variety in amongst it, although I found the first question dragged on a bit as I trawled through various pages looking for clear refutation of this point or that.
Tuesday, 8 July 2008
S282: Book2 - Chapter 3 & 4
Book 3 continues with some more chapters about galaxies. In chapter 3 we are considering active galaxies. This looks at all sorts of the more weird end of the galactic spectrum. It considers galaxies that have active cores - these include Seyfert galaxies, quasars and blazars - and whether they are the same thing viewed from different angles. Active galaxies appear to be associated with early galactic structure, at least in some cases. I found it all a bit dull to be honest after the first few pages. Maybe galaxies aren't my thing - or I'm missing the point!
Then chapter 4 looks at the distribution of galaxies. The fact that the milky way is just one of a local group of galaxies that includes a number of others. Then our local group is part of a supergroup of groups grouped together. Beyond that there doesn't seem to be any further discernible structure to the universe.
Then chapter 4 looks at the distribution of galaxies. The fact that the milky way is just one of a local group of galaxies that includes a number of others. Then our local group is part of a supergroup of groups grouped together. Beyond that there doesn't seem to be any further discernible structure to the universe.
Wednesday, 18 June 2008
S282: Book2 - Chapter 1 & 2
Well - another weighty tomb awaits us in the shape of Book 2, An Introduction to Galaxies and
Cosmology (435p). The first book was all about the birth, life loves and death of stars. In this book we take a step back and look at the bigger picture of how galaxies are born, live and die.
If you thought finding out details of stars which are all tiny pin pricks of light was hard, well its much simpler than galaxies. Galaxies are orders of magnitude further away than stars so the amount of light you can capture is typically smaller.
Anyway - we start the book with Chapter 1 looking at the Milky Way - our own galaxy. This allows us to explore what it is made up of (and stars are are pretty minor component!), its shape such as the halo (including the dark matter one) and the bulge, some of the oddities within it such as open cluster and globular clusters.
Then Chapter 2 looks at regular galaxies. There are a lot of different galaxies out there and naturally the first thing the early people did was to lump them together into categories. So we have spirals (with and without bars), ellipticals, lenticular and irregulars. These are classified according to the Hubble scheme (or other variants).
Then there is quite a section on how we work out the distance to these galaxies - which is pretty hard work. Many techniques are not very accurate but give a good appreciation of the order of magnitude.
Cosmology (435p). The first book was all about the birth, life loves and death of stars. In this book we take a step back and look at the bigger picture of how galaxies are born, live and die.
If you thought finding out details of stars which are all tiny pin pricks of light was hard, well its much simpler than galaxies. Galaxies are orders of magnitude further away than stars so the amount of light you can capture is typically smaller.
Anyway - we start the book with Chapter 1 looking at the Milky Way - our own galaxy. This allows us to explore what it is made up of (and stars are are pretty minor component!), its shape such as the halo (including the dark matter one) and the bulge, some of the oddities within it such as open cluster and globular clusters.
Then Chapter 2 looks at regular galaxies. There are a lot of different galaxies out there and naturally the first thing the early people did was to lump them together into categories. So we have spirals (with and without bars), ellipticals, lenticular and irregulars. These are classified according to the Hubble scheme (or other variants).
Then there is quite a section on how we work out the distance to these galaxies - which is pretty hard work. Many techniques are not very accurate but give a good appreciation of the order of magnitude.
Monday, 2 June 2008
S282: Chapter 8 and 9
The final two chapters of this tomb relate to the death of stars and what happens to them afterwards.
The death throws can result in stars doing all sorts of things. Some of them eject large rings of material called planetary nebulae. The bigger and brasher stars go out with a bang in a supernova explosion, which as a by product generates most of the common elements with atomic numbers greater than Iron. Supernovae can occur in a couple of ways, mostly its big brash stars blowing up, but occasionally its a white dwarf in a binary system given a second chance to shine.
The death of a star depends largely on how big it is. The smaller stars like our own after going through a red-giant phase tend to start to fizzle out into a white dwarf. In this stage, they are basically out of fuel, and all they can do is sit there and glow with the heat saved from their glory days. They eventually cool down to black dwarfs, but this takes so long to happen, that it probably hasn't had chance yet. However they are rather faint objects so they are difficult to see at the best of times. There is a fairly hard and fast limit (the Chandrasekhar limit) to the size of a white dwarf, and most stars sneak under this limit by blowing off much of their mass in their death throws.
Bigger stars end up as more exotic objects, including neutron stars, quark stars (possibly - the jury is still out on the existence of these) and the more famous black hole.
With that, book 1 is done, and book 2 beckons, but a TMA needs to be finished first!
The death throws can result in stars doing all sorts of things. Some of them eject large rings of material called planetary nebulae. The bigger and brasher stars go out with a bang in a supernova explosion, which as a by product generates most of the common elements with atomic numbers greater than Iron. Supernovae can occur in a couple of ways, mostly its big brash stars blowing up, but occasionally its a white dwarf in a binary system given a second chance to shine.
The death of a star depends largely on how big it is. The smaller stars like our own after going through a red-giant phase tend to start to fizzle out into a white dwarf. In this stage, they are basically out of fuel, and all they can do is sit there and glow with the heat saved from their glory days. They eventually cool down to black dwarfs, but this takes so long to happen, that it probably hasn't had chance yet. However they are rather faint objects so they are difficult to see at the best of times. There is a fairly hard and fast limit (the Chandrasekhar limit) to the size of a white dwarf, and most stars sneak under this limit by blowing off much of their mass in their death throws.
Bigger stars end up as more exotic objects, including neutron stars, quark stars (possibly - the jury is still out on the existence of these) and the more famous black hole.
With that, book 1 is done, and book 2 beckons, but a TMA needs to be finished first!
Friday, 9 May 2008
S282: TMA-2
Its time to do the second TMA on this course and this one is relatively involved.
The first question is to write up an experiment you have performed, either on calculating the luminosity of the Sun, or on the sidereal day. I chose the former. For this we had to compare on a sunny day the output of a 150W lightbulb with the sun using a piece of paper with an oil spot on it. You move the paper in between the sun and the bulb until the oil spot is not visible anymore - then you have similar luminosity values. Unfortunately 150W lightbulbs are pretty much phased out especially the clear ones that are required and 100W clear are hard to find but I did managed to find a 100W clear eventually. I ended up with about 1/3 of the accepted value for the luminosity of the Sun, which considering there was some very hazy high level cloud around, and it was early in the year (and I was using 100W bulb) I didn't think was too bad. I've learnt not to expect too much from physics experiments without doing a fearsome amount of work.
This question is worth 40% of the marks. It means of course you have to do the experiment first, and then write it up using the appropriate section headings, titles, abstracts and stuff like that. It requires analysis of data, error calculations and how the experiment could be improved and so on.
Question 2 is another relentless one. Its split into 3 sub-questions on parallax measurement, doppler measurements and some planisphere work to work out rising and setting times. Each sub question is made up of 3 to 5 parts, so that's 11 questions you have to answer, for 24% of the marks.
Question 3 is similarly made up of 3 subsections on spectral classification, spectral measurement and magnitudes. Its again 11 questions in all and is again 24%.
Question 4 is about dust clouds and collapse to form suns. Three sub parts again looking at collapse conditions, Hertzsprung-Russell diagrams for forming clouds, and finally a wild card on detection of planets orbiting other suns. Only 7 questions in total to answer here for your 12%.
The first question is to write up an experiment you have performed, either on calculating the luminosity of the Sun, or on the sidereal day. I chose the former. For this we had to compare on a sunny day the output of a 150W lightbulb with the sun using a piece of paper with an oil spot on it. You move the paper in between the sun and the bulb until the oil spot is not visible anymore - then you have similar luminosity values. Unfortunately 150W lightbulbs are pretty much phased out especially the clear ones that are required and 100W clear are hard to find but I did managed to find a 100W clear eventually. I ended up with about 1/3 of the accepted value for the luminosity of the Sun, which considering there was some very hazy high level cloud around, and it was early in the year (and I was using 100W bulb) I didn't think was too bad. I've learnt not to expect too much from physics experiments without doing a fearsome amount of work.
This question is worth 40% of the marks. It means of course you have to do the experiment first, and then write it up using the appropriate section headings, titles, abstracts and stuff like that. It requires analysis of data, error calculations and how the experiment could be improved and so on.
Question 2 is another relentless one. Its split into 3 sub-questions on parallax measurement, doppler measurements and some planisphere work to work out rising and setting times. Each sub question is made up of 3 to 5 parts, so that's 11 questions you have to answer, for 24% of the marks.
Question 3 is similarly made up of 3 subsections on spectral classification, spectral measurement and magnitudes. Its again 11 questions in all and is again 24%.
Question 4 is about dust clouds and collapse to form suns. Three sub parts again looking at collapse conditions, Hertzsprung-Russell diagrams for forming clouds, and finally a wild card on detection of planets orbiting other suns. Only 7 questions in total to answer here for your 12%.
Saturday, 26 April 2008
S282: Chapter 5-7 Formation, Main Sequence, and decay
The next three chapters are all about the main sequence for stars. This is the thick band of stars that is evident on the old Hertzsprung-Russell diagram. Most stars appear on this main sequence somewhere, hence if being the main sequence...
Chapter 5 - The formation of stars - covers how stars assemble themselves from clouds of dust, and how they first appear. It looks at some of the maths of dust clouds, first work out by James Jeans. He worked on a number of areas, but in this one he looked at the dynamics of gas clouds. He found if they were above a certain density depending on temperature, a cloud of gas would contract and depending on how much was present, form a star - sooner or later. Such stars then start life initially off the main sequence, such as the T Tauri stars, but rapidly hop on following Hayashi tracks and then spend most of their time there.
Chapter 6 - The main sequence life of stars - covers the general structure of stars as they spend their life on the main sequence. It looks at the main nuclear reactions, such as the 3 main ppi types, and the CNO cycle which kick in at different temperatures and pressures. It also considers a minimum and maximum size that stars can reach and how long such stars live for. Broadly speaking, the bigger the star, the shorter its life.
Chapter 7 - The life of stars beyond the main sequence - covers what happens towards the end of a stars life. Stars reach the end of their lives when they run out of fuel. This is basically hydrogen that is in the core of the star. Thats the hottest and densest part, and the only place fusion can take place. As it uses it up, things get increasingly desperate. If the star is big enough, it runs out, contracts, warms up a bit more, and can burn a small shell of hydrogen around the core. It can also start to burn helium if things get warm enough, using the triple alpha process, which burns 3 helium -> 1 carbon. At this stage it swell up into a much larger Red Giant star, which is the fate of our Sun. After this, things get increasingly desperate. Carbon burning is possible and will keep a large star going for 10,000 years maybe, followed by neon burning (1 year), oxygen burning (6 months) and finally silicon burning lasting a day. At this point there is nothing left to burn! What could possibly happen next.
Chapter 5 - The formation of stars - covers how stars assemble themselves from clouds of dust, and how they first appear. It looks at some of the maths of dust clouds, first work out by James Jeans. He worked on a number of areas, but in this one he looked at the dynamics of gas clouds. He found if they were above a certain density depending on temperature, a cloud of gas would contract and depending on how much was present, form a star - sooner or later. Such stars then start life initially off the main sequence, such as the T Tauri stars, but rapidly hop on following Hayashi tracks and then spend most of their time there.
Chapter 6 - The main sequence life of stars - covers the general structure of stars as they spend their life on the main sequence. It looks at the main nuclear reactions, such as the 3 main ppi types, and the CNO cycle which kick in at different temperatures and pressures. It also considers a minimum and maximum size that stars can reach and how long such stars live for. Broadly speaking, the bigger the star, the shorter its life.
Chapter 7 - The life of stars beyond the main sequence - covers what happens towards the end of a stars life. Stars reach the end of their lives when they run out of fuel. This is basically hydrogen that is in the core of the star. Thats the hottest and densest part, and the only place fusion can take place. As it uses it up, things get increasingly desperate. If the star is big enough, it runs out, contracts, warms up a bit more, and can burn a small shell of hydrogen around the core. It can also start to burn helium if things get warm enough, using the triple alpha process, which burns 3 helium -> 1 carbon. At this stage it swell up into a much larger Red Giant star, which is the fate of our Sun. After this, things get increasingly desperate. Carbon burning is possible and will keep a large star going for 10,000 years maybe, followed by neon burning (1 year), oxygen burning (6 months) and finally silicon burning lasting a day. At this point there is nothing left to burn! What could possibly happen next.
Wednesday, 23 April 2008
S282: Chapter 4 - Comparing Stars
This chapter is a major overdose on the Hertzsprung-Russell diagram. Its a popular diagram in astrophysics, and by the end of this chapter, and a few subsequent ones, you'll feel right at home with it. It looks at the location of the main sequence stars, like our Sun, which is towards the more insignificant end of the chart. Also at things like Red Giants, SuperGiants and white dwarfs which fall off the main bad somewhat.
You also pick up a few other lesser known types, such as Cephids, and T-Tauri stars, which turn out to be a bit more important later on.
After the H-R diagram has been done almost to death, the remainder of the chapter focuses on the interstellar medium and its affects on observations.
You also pick up a few other lesser known types, such as Cephids, and T-Tauri stars, which turn out to be a bit more important later on.
After the H-R diagram has been done almost to death, the remainder of the chapter focuses on the interstellar medium and its affects on observations.
Tuesday, 8 April 2008
S282: Chapter 3 - Measuring the stars
Chapter 3 is all about how the stars are analysed from the Earth. So here we meet all sorts of remote analysis techniques.
It starts with a look at how we can measure the distance to the stars, starting with measuring parallax. This allows distances to the nearer stars to be measured. It also discusses the proper motion of the stars, and also the radial and space velocity from these details.
Following that there is a look at how other things can be worked out. If you know the distance, you can work out the luminosity of the star. From this you can also work out things like radius, temperature and some other things. Spectroscopy features quite highly here, as there are a number of things that can be worked out from this. Radial velocity is one thing based on the Doppler shift. However there are a number of other things you can work out from this, including some clues to the mass and temperature.
This leads to the categorisation of stars into the stellar classes such as O,B,A,F,G,K,M etc.
It starts with a look at how we can measure the distance to the stars, starting with measuring parallax. This allows distances to the nearer stars to be measured. It also discusses the proper motion of the stars, and also the radial and space velocity from these details.
Following that there is a look at how other things can be worked out. If you know the distance, you can work out the luminosity of the star. From this you can also work out things like radius, temperature and some other things. Spectroscopy features quite highly here, as there are a number of things that can be worked out from this. Radial velocity is one thing based on the Doppler shift. However there are a number of other things you can work out from this, including some clues to the mass and temperature.
This leads to the categorisation of stars into the stellar classes such as O,B,A,F,G,K,M etc.
Friday, 14 March 2008
S282: TMA-1
Time for the first TMA. As I flip through the pages, metaphorically as its actually delivered in PDF,my first though is it looks pretty long. Its got 5 questions, which doesn't sound that much, but it is. For instance the first question, has sub parts a), b) and c). Then part a) has sub-sub parts i) and ii), b) has i), ii) and iii) as does c). So that is 8 questions to be answered for 18 marks, in the first question alone, and a number of them are in the "explain why" category requiring more than just a number.
Question 1 (18 marks) is about black body and other radiation features such as peak wavelengths. Some calculation required, with a dose of explanation. .
Question 2 (25 marks) requires you to look at a photograph of the sun taken through a number of different filters and interpret the data. 4 sub questions, and 10 sub sub questions. Its about temperatures and emissions.
Question 3 (35 marks) you need to look at a sequence of photographs and do some work based on the images of what I think is a coronal mass ejection. This one requires calculation and a drawing to illustrate some features on the sun.
Question 4 (4 marks) is an exercise in using the planisphere to predict various starts rising and setting. You have to explain how you worked it out too.
Question 5 (18 marks) is about forward planning. TMA-2 requires one of two possible experiments to be done and this question leads you through explaining how you are going to run these experiments and when you are going to do it etc. Hopefully it is easy marks but is clearly designed to get you in the groove to run the experiment so there are no surprises.
Anyway - that's the first one down, and posted. Hope for the best!
Question 1 (18 marks) is about black body and other radiation features such as peak wavelengths. Some calculation required, with a dose of explanation. .
Question 2 (25 marks) requires you to look at a photograph of the sun taken through a number of different filters and interpret the data. 4 sub questions, and 10 sub sub questions. Its about temperatures and emissions.
Question 3 (35 marks) you need to look at a sequence of photographs and do some work based on the images of what I think is a coronal mass ejection. This one requires calculation and a drawing to illustrate some features on the sun.
Question 4 (4 marks) is an exercise in using the planisphere to predict various starts rising and setting. You have to explain how you worked it out too.
Question 5 (18 marks) is about forward planning. TMA-2 requires one of two possible experiments to be done and this question leads you through explaining how you are going to run these experiments and when you are going to do it etc. Hopefully it is easy marks but is clearly designed to get you in the groove to run the experiment so there are no surprises.
Anyway - that's the first one down, and posted. Hope for the best!
Thursday, 21 February 2008
S282: Chapter 2 - The working sun
This chapter moves from observation of the sun into the inner workings and how it all is thought to work, and what we can deduce. Things like models of the interior and how well they compare with measurements. Radiative and convection zones, stellar "earthquakes" and so on all feature.
Also covered are some of the reasons for the more visible things such as prominences and mass coronal ejections - which includes some tricky magnetic field stuff.
Finally the sunspot cycle and the 22 year general cycle.
Also covered are some of the reasons for the more visible things such as prominences and mass coronal ejections - which includes some tricky magnetic field stuff.
Finally the sunspot cycle and the 22 year general cycle.
Wednesday, 23 January 2008
S282: Chapter 1 - Seeing the sun
The text book An Introduction to the Sun and Stars is a great book, although there is a lot to it. There are lots of full colour pictures, and scattered through the text are questions to check you're understanding - which is very like the S103 course.
Its very much like the S194 course, but MUCH more detailed. Also the questions you have to answer, such as how many kilograms of hydrogen does the sun consume a year (its about 5.8 × 1011 kg s−1 in case you're interested), are not handed to you on a plate. You are given some figures, but others you may have to find from earlier in the text or deduce from other information and formulae. I find this all quite invigorating at this stage - and I know that may make be a little weird.
Anyway, this first chapter considers observations of the sun and its various components (yes, I thought the sun was just a yellow thing, but its much more complicated than that!). It has pictures of the sun taken in everything from visible light to x-ray to radio waves. It looks at the theoretical structure and what is going on deep in its depths based on what can be seen on the surface.
Its very much like the S194 course, but MUCH more detailed. Also the questions you have to answer, such as how many kilograms of hydrogen does the sun consume a year (its about 5.8 × 1011 kg s−1 in case you're interested), are not handed to you on a plate. You are given some figures, but others you may have to find from earlier in the text or deduce from other information and formulae. I find this all quite invigorating at this stage - and I know that may make be a little weird.
Anyway, this first chapter considers observations of the sun and its various components (yes, I thought the sun was just a yellow thing, but its much more complicated than that!). It has pictures of the sun taken in everything from visible light to x-ray to radio waves. It looks at the theoretical structure and what is going on deep in its depths based on what can be seen on the surface.
Friday, 11 January 2008
S282: Starting
Well what a day - both the S282 and the S320 materials arrive on the same day!
The initial mailing contains the following:
The initial mailing contains the following:
- An introductory letter
- A Planisphere - the same as the S194 one.
- A study calendar
- A Large book called An Introduction to the Sun and Stars
- A rather large activity book
- A DVD with course materials on plus some video sequences.
- An applications CD ROM
- A glossy colour A4 picture of the Jewel Box cluster.
- A course guide
- 2 PT3 Forms
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