Thursday 15 March 2012

Cosmology Planetarium Shows with ICG

Script for the A-level Cosmology show made in collaboration with Karen Masters at ICG.

Start outside dome

After safety briefing introduce yourself and your research. Introduce WAA and the Stellarium software/ apps. Introduce Cosmology ‘ trying understand the nature of the Universe as a whole’ Cosmologists seek to understand the origin, evolution, structure, and ultimate fate of the Universe at large, as well as the natural laws that keep it in order. I actually studied an individual supermassive black hole in a galaxy as part of my research, a cosmologist might also study supermassive black holes but they would think about them in terms of ‘the part they have played in Galaxy evolution in the universe as a whole’5 mins

In dome

Play WAA  25 mins Play ‘Zoom through telescope’ Movie 1 min 17sec
Go into Stellarium

Finding North

Starting with Big dipper, which is an asterism, part of the constellation ursa major, which means the Great Bear.  And Ursa Minor, which means small bear. The lowest too stars in the saucepan point to North Star.

It looks like a saucepan, with a handle and a place to put your beans, counting from the 2 stars at the end of the pan, count in a straight line about 5/6 steps (at a step distance of the gap between those 2 stars). There you will find Polaris aka the North star.  Many people think North Star is the brightest in the sky! It isn’t! it is only important because it is directly above the North Pole, and stays above the north pole as the earth spins on its axis causing all the other stars to spin around! Think about spinning top (from Christmas cracker) the top part, which you spin around with your fingers, doesn’t appear to move while the sides of the top are whizzing around. The middle of the top represents the North Pole with the North Star is right above it. Make sure they realise none of the stars actually move, and it’s us that are moving?

(speed up time L in Stellarium so they can see stars going around in arcs)
Mentioned Axis of Earth ( if time mention Southern Hemisphere doesn’t have a star above south pole :( They use Southern Cross and point to an area which is above/below the South Pole)

Constellations      Make sure can see both Cass and big dipper

Ask ‘what is a constellation? ‘     Explain these are 48 constellations in total.
Turn on constellation art press ‘r’ key
Patterns of stars in sky, imagine the ancient Greeks without TVs very bored so used to join the stars together like a dot to dot, Mention that the Saucepan/Big Dipper is an Asterism not constellation, as it is part of the great bear. Turn off constellation art  r

Circumpolar stars 

Explain that the constellations of Cassiopeia and Andromeda and Ursa Major etc are Circumpolar constellations and never set.

Cass looks like a W or an M for McDonalds, find her from the Big Dipper by drawing a line through North Star. Cass is a queen married to King Cepheus (he is in sky near by looks like a house drawn by a child). Andromeda is Cass’s daughter. Mention film ‘Clash of Titans’ and Greek Mythology but don’t talk about it any further.

Zoom to Andromeda

Locate Andromeda.. go along same line from Polaris, to Cass, and thru to Andromeda.. (Search Fn-F3 for M31, and zoom in using / in stellarium)
When in Andromeda constellation, say it is our nearest spiral galaxy Andromeda (in local group.) It is 2.6 million light-years (2.5×1019 km) away. And it is the most distant object you can see with the ‘naked eye’.

 Andromeda looks a lot like our own galaxy and you can imagine if you were flying in space outside our Milky Way it would like very similar to Andromeda.
Andromeda is actually has double the amount of stars that the MW has.

Dark matter in Andromeda 

 So I just mentioned that Andromeda has more stars than the Milky Way. But astronomers think that the Milky way is actually more massive, as it has more Dark Matter. Can anyone tell me what dark matter is?
Vera Rubin is a scientist from the USA who studied the variation of the velocities of the gas in between stars (interstellar medium) with distance from the center of the galaxy. She found that …

Black hole in Andromeda. 

Now it might shock you to know that our Solar System is orbiting in our galaxy around a Supermassive black hole

And there is also a supermassive black hole at the centre of Andromeda galaxy.

These supermassive BH were predicted by Einstein’s theory of general relativity. They exist at the centre of all galaxies, a million times that of sun. The BH in our MW is actually 4 million times mass of sun! Ask ‘how do you think astronomers know the mass? Cos they can’t just weigh it with a scales?’ Using Keplers Third Law which hopefully you have heard of this equation which relates the speed of stars which are orbiting the Mass, to the mass of the thing they are orbiting. This is exactly how we measure the mass of the Sun.

Astronomer measured high speeds of stars orbiting around an object known as Sagittarius A* which is at the centre of our galaxy the MW.

Can zoom / into Sagittarius A*/ search for Sagittarius using Fn-F3. Can’t see much there, turn off the constellations , c and search fnF3 for M25 this is a near by cluster of stars
Explain that at the centre of our galaxy astronomers measure the speeds and orbits of stars just like that’s how they know there is a supermassive black hole there!

Ending thought about black holes.

Most people think of black holes as monsters but Astronomers now think they play a large part in the early formation of galaxies. As we learn more about how galaxies were formed in early universe it seems that the BH at the centre plays a large part in forming galaxies, remember that the jet from the centre of the galaxy can reach into other galaxies, these jets of particles might start star formation to occur in galaxies where it might otherwise not have occurred. This means that without our blackholes the universe might of not formed galaxies. And without galaxies there wouldn’t be stars, without the stars, no solar systems of planets and with out planets, no humans, so black holes may not something to be afraid of.
The massive Jets from galaxies like M87 and 3c273 are so far reaching that they can actually reach into nearby galaxies.  Astronomers think that these jets can affect the surrounding galaxy giving the surrounding galaxies more energy. This might mean that idea that black holes are monsters is wrong; they actually might be responsible for the formation of galaxies like our own. And of course without the galaxy there is no solar system and without the solar system no place for us to live!

For example if our Sun turned into a black hole we wouldn’t all get sucked in, the Earth would actually orbit around quite happily. Obviously, without the energy from fusion humans would not exist though.
Gravity works for black holes just like it does for everything else. Black holes don’t suck – they just have very strong gravity, so it’s dangerous to get very close. But far from a black hole things orbit them normally.

Blueshift and redshift 

Ask if they have heard of red shift or doppler shift? Remind them that that it is to do with the wavelength of electromagnetic radiation. When an object is moving away from you (like most galaxies are moving away from us) the radiation or light we detect is shifted to longer wavelengths because of the motion of the object away from us means the light waves get stretched out, i.e. the energy of light measured by an astronomer is nearer the lower energy red end of the spectrum , hence the name ‘red shift’ – compare with the pitch of the ambulance siren as it goes past you with the wavelets bunching up in front of the ambulance when it is moving towards you, and spreading out behind. Sound wave compressed as it came toward you, and stretched as it went away. Same is seen in stars, and used to observed the motion of galaxies.

 Say that the light from Andromeda is actually blue shifted! Ask them what this means? So MW and Andromeda are actually moving toward each other in space at about 100km per sec which seems very fast and might scare you but this is actually equivalent to  400 lightyears every million years (and remember Andromeda is 2.6 million light years away) attracted to each other by gravitational forces due to their large masses, in 4.5 billion years they will collide making a much larger galaxy.
Out of Stellarium
Play ‘Redshift blueshift’ movie 12.27-12:37 10 secs
You can see the light is redder or stretched because the galaxy is moving away from us.
Galaxies come in different types. We’ve seen the Milky Way and Andromeda which are both spiral galaxies, but we think after they merge together they might form an elliptical galaxy which are the other kind.
Play ‘highresgalaxycollision’ movie 53secs
Lots of astronomers work to try to understand how the different kinds of galaxies formed and how they got the shapes they have.
Now hopefully some of you have heard of the Galaxy Zoo project. This is an site where members of the public, like yourselves can help the astronomers by classifying galaxies. You do this by going on the website and just looking at the shape of the galaxy to decide which type you think it is.

Our view of the universe has changed. 

It is only since the 1500’s that we have really started to understand the solar system and our universe.

Play ‘Solar system’ 1 min 05:15-06.09
Before telescopes were invented everyone believed the earth was the centre, we thought the sun, moon and planets orbited around it.
Then in 1543 Nicholas Copernicus proposed a different model with the Sun at the centre, it was a radical idea and he didn’t have any evidence to prove it. Nearly 65 years later, Hans Lippershey fixed 2 small pieces of glass into a tube and made an Eyeglass. Galileo saw these designs and made his own telescope and observed Jupiter, and noticed some points of light either side of Jupiter which appeared to move around it. He soon discovered these were moons orbiting around Jupiter, and this made people realize that the Earth wasn’t actually so important, since objects could clearly orbit around other planets like Jupiter. The telescope was then used to prove Copernicus’ new theory that the earth was not the center of the Universe. It was also used to learn more about our Galaxy
Play ‘’ 1 min 48  12.37-14.33

Our Galaxy and Other Galaxies

We have only known that we have lived in a galaxy for the last 100 years. Before the 20th century thought the universe consisted of a flat disk of stars with the earth and the solar system at the centre.
Caroline Herschel made a map of this disk, but because telescopes did not have the resolving power of todays telescopes. They thought the other galaxies were part of this disk. An astronomer named Edwin Hubble observed Cephid Variables and was able to determine that these galaxies were extremely far away.
There was a massive public debate in 1920 between two astronomers about if “spiral nebula” were external, or in our own Galaxy. Harlow Shapley thought they were in our Galaxy because it was really huge. Heber Curtis thought our Galaxy was smaller and the others were all external. Turned out they were both right as the universe is much bigger than they could imagine. Our Galaxy is as big as Shapley thought it was and the others are all outside it!

An astronomer named Edwin Hubble observed Cephid Variables in the mid 1920s and was able to determine that these galaxies were extremely far away. He also used these measurements to show that the further galaxies get from us the faster they are moving away from us (using measurements of their redshift). This demonstrated that our Universe is not only vast, but also expanding!

Play ‘Fly through HST galaxies’ 1 min 20.48-21:33 
We now have such good telescopes (like the HST) that we can see galaxies that are so far away that the light from them has taken almost half of the age of the universe to reach us.
Light travels very fast – about 1 metre in 3ns, but it still takes 8 minutes to reach us from the Sun, 3 years from the nearest star, and millions or billions of years from the external galaxies.
These galaxies show an incredible variety of different types of galaxies even very early on in the Universe.

Sloan Digital Sky Survey

Play Journey_3D_HD (on desktop) 1min 23sec
This visualization presents a 3-D view of the largest structures in the Universe via data from the Sloan Digital Sky Survey. The SDSS is the most ambitious astronomical survey ever undertaken. It provides a 3-dimensional map of about a million galaxies and quasars. As the survey progresses, the data are released to the scientific community and the general public in annual increments.

We also have massive surveys of galaxies in the Universe. This movies shows 1 million galaxies which have been mapped by the Sloan Digital Sky survey.
We can’t see galaxies everywhere. These black areas are the modern equivalent of “here be dragons” anything there is hidden from our view by our own galaxy.
But the web like structure is real. This is showing how galaxies formed where there were clumps of dark matter in a filamentary web. We can understand things about cosmology from carefully mapping the shapes seen in this structure.
When we look at the most distance galaxies, we are looking further back into time. This is because the light from the most distant galaxies has taken such a long time to get to us. Therefore, the furthest point we want to look back to is the creation of the Universe, the time of the ‘Big Bang’.
Each marker here is actually real data , which is why there is a big gap in this data. It doesn’t mean there aren’t galaxies there; we just haven’t looked there yet.

Quasars are thought to be the first massive structures which formed in the beginning of the universe, half a billion years after big bang. In this data you can see a clustering of the galaxies in certain areas. Astronomers think the reasons why quasars seem to be surrounded by dense clusters of galaxies is because the jets from these early quasars actually played a part in fuelling the formation of galaxies.

The CMB represents the edge of observable universe. When I say observable universe what I mean is there are galaxies and quasars out beyond this boundary it is just that we cannot see them, remember this is real data taken by telescopes and they can only observed the light from galaxies out to a certain distance. Just like when you are in power cut with a candle and can only see things right in front of you.


End with CMB on sky from movie
Beyond the quasars we have the light from the Cosmic Microwave Background or CMB , this light marks the edge of observable universe. This is not really the edge of the Universe but it is the light from the very beginning of the universe 380,000 years after the Big Bang when electron and protons started to form into hydrogen atoms...and we can’t see the light from back any further than this

The CMB fills the universe almost uniformly. It may not look like it from this image of the CMB but Astronomers say that the CMB shows us that the Universe is Isotropic and Homogeneous Isotropric means the same in all directions, and Homogeneous means the universe will look the same from whatever position you stand in.
The CMB is at a temperature of 3 degrees above absolute zero(or 3K)
And has a wavelength between the mm-cm regime, which is comparable to radio and TV Wavelengths.
This means you can use your TV to detect radiation from the big bang, if you tune a TV between channels about 1% of the static is from the CMB.
These spots of different colour represent very small fluctuations in the density of the CMB and it is in these most dense regions where galaxies would have formed.


Take questions outside of dome for 5 mins….

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