Sunday 24 July 2011

First Planetarium show at INTECH

My first planetarium show at INTECHs massive planetarium in Winchester was a lot of fun, and also a little scary. I am used to doing shows for 30 students in a small blow up, travelling, planetarium but a show for over a 100 people wearing a microphone is another thing.

The planetarium show was written in collaboration with the planetarium manager Jenny Shipway to compliment Dr Phil Uttley's talk on Black Holes. During 18-22nd July 2011 many astronomers descended on Winchester for the Black Holes Astrophysics:Tales of power and destruction conference.

The script I wrote for the Black Hole planetarium show is below:

1. Hello my name is Sadie Jones and I am just finishing my postgraduate studies at the University of Southampton at the moment, my research is on a specific super massive black hole at the centre of a spiral galaxy much like our own milky way, but this galaxy has an active centre, which features jets. Jenny and I are going to give you a 30minute planetarium show, which should introduce you to the locations of some of the black holes within our universe.

      2. I will start by teaching you how to find the North Star. Here is the plough or the big dipper, I think it looks more like a saucepan, which is a small grouping of stars within a larger grouping of stars called a constellation. The constellation which the saucepan is in is called Ursa Major which means Great Bear, using the 2 stars at the end of the saucepan and taking the space between them as a ruler, count about 5 steps in the direction of the ruler and here you will find Polaris, the north star. This star is interesting because it just happens to be above the north pole so as the earth is spinning us around it appears as all the other stars circle around the North star yet it stays in the same position. Have you ever noticed that the stars rises in the east and sets in the west as the night goes on ? Of course the sun does this too.

      3. However, there are some stars that do not set and can be seen any time of the year above England provided there are clear skies. The great bear group of stars is an example of a group of stars which never set and this is where my favourite black hole is. It is called we called NGC4051 and lives at the centre of a galaxy Phil and I have done a lot of research on this galaxy, this is in the rump of the Great Bear, and we will talk more about this active galaxy later.

4.     Before I point out any other black holes in the night sky I am going to ask Jenny to move us around from our current position facing North, to another group of stars in the South. These grouping of stars are called the summer triangle, this is because they unlike the great bear constellation they do set, which means they can only be seen in the autumn and summer.

5.     Summer triangle, this asterism joins three of the brightest stars which can be seen in the summer, with one in constellation of Cygnus, and the others in Lyra and Aquila. One of the black holes I will talk to you about shortly , actually exists within our own galaxy the Milky Way and its location as seen from our place on earth is here, in the centre of the body of the swan group of stars , called Cygnus.
6.     Next we are going to Virgo. There are two black holes in this constellation which I will tell you about, and one is in the bowl of Virgo . Here there is a massive cluster of galaxies.

7.     Hopefully from listening to Phil’s talk you will remember that there is actually a black hole at the centre of our galaxy the Milky Way and the location of the centre of our galaxy is in the grouping of stars called Sagittarius. We know there is a super massive black hole there because as you might remember from Phil’s talk, astronomers have tracked the paths of stars moving around a very heavy object. From estimating the speeds of these stars around the object they can estimate how heavy it is. The faster the star is moving stronger the force needed to keep it in place, which means the weight of the object being orbited will be heavier. From measuring the speeds of 6 stars around this invisible heavy object astronomers estimate the weight of the black hole to be about 4 million times as heavy as our sun. And our sun is equivalent to a trillion trillion 2000kg elephants.

The orbits of 6 stars around the black hole at the centre of the milky way

8. Now the Milky Way, the galaxy we are in can be seen earth as plane of dust across the night sky. Because Sagittarius A* is at the centre of our Milky way it makes sense that its location is within the dust and gas of the milky way as we see it as a strip across the sky.
The distance from the centre of the super massive black hole at the centre of the milky way out to its edge is about the same size as the distance from the sun to the orbit of Uranus, now this might not seem very small. But the only object we know which can be so massive, 4 million times as heavy as our sun, in such a small area is a black hole.

9.     Sun So now I’ve told you the locations of the black holes we are going to visit I am going to ask Jenny to fly us out wards from a place on Earth into our solar system. First we see our nearest star which of course is the sun, and we can see the orbits of all the planets out to Neptune.
So what do you think would happen if I was to replace the sun with a BH the same size as the sun??(Phil discussed this in his talk by imagining the Earth becoming a BH?? Yes! you are right! As long as the planets don’t get within a certain distance of the sun ( which is called the event horizon and for the sun is 3km ) They will still orbit just the same as they do when the sun is there,  they will not get sucked into the black hole. Because this bh has the same mass as the sun it means the planets orbiting it will behave exactly the same. Beyond the 3km event horizon all the laws of physics breaks down.  From phils talk you have learned small black holes do exist. When I say small black holes, they are only small in comparison with the super massive black holes at the centre of galaxies! These small black holes are usually about 10 times as heavy as our sun, these actually exist within our galaxy and survive by sucking material off nearby stars, we say they are in binary systems because there are two objects, the star and the black hole. Now we are going to fly to one of the most famous binary black holes which is called Cygnus X-1 and like I mentioned earlier this is in the grouping of stars which looks like a swan as seen from earth.

10. Cygnus-X1   was the first source discovered using X-ray telescopes which was widely accepted to be a black hole and it remains one of the most studied objects by astronomers . It is now estimated to have a mass about 9 times the mass of the Sun and has been shown to be too be to dense to be any known object other than  a black hole. The radius of its event horizon is probably about 26 km. It’s known as a High Mass X-ray Binary system by astronomers. It was once two stars but the one star which was probably more than 10 times heavier than the other star could no longer carry out the process of fusion in its core so it would have swollen up into a red supergiant and then died in a supernova explosion, these explosion occur at the end of the life of star and if the star is big enough will leave a dense core which will either become a neutron star or a black hole!  As you can see the one star which is called a blue supergiant is orbiting this black hole. When material falls onto the black hole it releases large amounts of energy as jets which we can detect with our X-rays observatories in space.  There are many of these binary black hole systems in our Milky way and It is interesting that the combined mass in these black hole binary systems may actually add up to more than the super massive BH at the centre of our Milky Way galaxy, however, it is difficult to be sure of this since we can only see the black holes which are actively eating stuff.

11. Fly out to Milky Way, as we Fly out of our galaxy, you can see that the red lines which link the groupings of stars are not all at the same distances, they are just in the same region of sky as viewed from earth. The Sun is just one of 100 billion stars in our galaxy and this galaxy is just one of 100 billion galaxies in our universe, and our sun is orbiting around the centre of the Milky Way. It takes us 230 million years to orbit the centre of the galaxy once, and you can see the orbit of our sun around the centre of the MW is very circular. As I explained earlier the milky way has a super massive black hole at the centre of it , but we are not getting sucked down it as you might imagine, you can see from the orbit of the sun around the BH that we are just merrily orbiting around the centre, just as the earth merrily orbits around the sun.

M87 in the X-ray, radio and optical

12. M87 Now we are going to fly out into the universe from our galaxy to look at another galaxy, this is called M87- and is one of the galaxies in a large cluster of galaxies in the constellation of Virgo which I pointed out earlier, this cluster of galaxies is called the Virgo Cluster and you can see the galaxy is within this large bubble which marks the high density clustering of galaxies in this area. This is also a galaxy with a SMBH at centre but it is not a quiet BH like the BH in the Milky Way, it is very active and it has massive jets which are very powerful. You may think it looks more like a star than a galaxy, but it is a galaxy, it just has a  different shape to our milky way which is spiral galaxy, this galaxy is called an elliptical galaxy since it is a lot more rounded the stars are not in a disk like MW, but a sphere . It has jets like Cygnus X-1 but these are a lot more powerful and result from the black hole eating a lot more fuel. You can actually see this jet using optical telescopes, our eyes detect optical light so this means if you were flying about in the universe your eyes which also detect optical could see this massive jet. This means that the Particles released by the jets from black holes are actually going into your eye, so your eye in a way is interacting with a black hole. The jet from the black hole in this elliptical galaxy actually extends out 5,000 light years which is about the same as the typical distance between galaxies.

The beautiful and lovely bain of my life, NGC 4051

13. NGC 4051 –So now we are going to fly from the M87 in the virgo cluster to mine and phil’s favourite black hole. As we fly out ever dot in the planetarium is no longer a star but a  galaxy . This black hole called NGC 4051 is also at the centre of a galaxy,  its actually within a spiral galaxy much like our own. It looks like our milky way and is about the same size as the milky way, but this one is important, because even though it looks alot like our own MW, it is actually eating alot more fuel which means the centre of the galaxy is very bright. Astronomers call these galaxies active galaxies and some active galaxies have jets which are launched from the black hole at the centre. Phil and I have done a lot of research on this galaxy looking at both the material falling into the BH and the particles emitted by the jets of the radiation which astronomers believe are launched from close to the BH. My research has been into understanding why this galaxy has jets and the relationship between the jets and the material falling into the black hole. The jets in NGC4051 are not nearly as powerful or as far reaching as the jet from M87 I showed you earlier. Astronomers still don’t really understand why some black holes have jets of particles coming out of them, and a lot of work at the Uni of Soton is on trying to understand these jets…Just to remind you if you are looking from earth this active galaxy called NGC 4051  was in the grouping of stars called the great bear.

14. So far I have talked about spiral galaxies and elliptical galaxies both which have super massive black holes at the centre of them, and I have also shown you an example of  the smaller binary black holes exist within our own galaxy.

15. 3c273 – Now I will ask Jenny to Fly out to Quasars. Quasars are the most powerful type of black hole and they are the first large structures which formed at the beginning of the universe. 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. Now 3c273 is actually the first discovered quasar, the reason it was discovered first is because one of the two powerful jets launched from the black hole is beamed directly toward Earth !! This makes the quasar very bright and easily detectable by X-ray observatories in space.  3c273 is 187 million times the mass of the sun and is one of the most distant objects which can be seen with your telescope.

16. These 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 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!

17. (When out at 1.3Gpc distance) the light left these galaxies about 5 billion years ago when the earth was formed. Now we are going to fly out even further to the quasars at 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.

The CMB !

18. Beyond the quasars we have the light from the Cosmic Microwave Background, 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.

19. Ok now we are going to Fly back home to our Earth. Back through the quasars, and the galaxies, into the milky way and our own solar system and now here . Home sweet Home.

20. Hope you enjoyed this introduction to the black holes in our Universe. Thank you very much for listening...

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