Adrian: Girls, come on. I will start Hadrian’s time-ship shortly. I’ve made a few changes to the original design. Now it can work as a time-ship and a space-ship.
98 Ianthi: What will we do this time Adrian?
Adrian: I have also fitted two different glasses to the two front windows: in the right window, I put a special glass that allows you to see only visual light. In the left window, you can only see X-rays.
431 Nefeli: Speak slowly Adrian so I can understand. If 98 Ianthi goes in front of the right window and I sit behind it, I will see her ‘normally’, with her skin and her clothes.
98 Ianthi: Whereas if we do the same experiment, but with the left glass, you will see me as you see an X-ray. You will see 431 Nepheli, only my bones.
Adrian: Very correct girls. So you can easily understand now that many things look different when you look at them in another light (blue, red, X-rays, radio, or microwaves). They look different because you see other hidden objects that you wouldn’t otherwise see, like your bones on X-rays. I wanted to go see a galaxy cluster with the two different glasses. It must look different. Only the galaxies inside the cluster are visible in visible light. X-rays show the hot gas which is also exactly in the same space as the galaxies.
98 Ianthi: I know, I know what the ‘cluster of galaxies’ is.
431 Nefeli: Me too! Can I say?
98 Ianthi: Let’s first see what the beautiful photo with all these colored balls is.
431 Nefeli: ‘Galaxy cluster’ are many galaxies together in a small area of the universe.
98 Ianthi: A ‘rich’ cluster can have 1000 galaxies.
431 Nefeli: The galaxies contained in the cluster can be seen very clearly in visible light.
98 Ianthi: The cluster also contains hot gas visible only in X-rays.
431 Nefeli: Intracluster medium is called 98 Ianthi. Be more careful.
Adrian: So, within the galaxy cluster there are the galaxies and the intracluster medium.
It is just like the next bowl of water and colored stones. The colored stones are the galaxies. The bowl is the galaxy cluster. The water inside the bowl is just like this intracluster medium. The water takes exactly the shape of the container.
Adrian: Now that I see the photo better, I don’t think it has water in it. But I’m sure you can imagine.
98 Ianthi: When will we go to Koma? I look forward.
431 Nefeli: Let’s finally go. It’s next to here. It is only 3000…000 (21 zero) kilometers away.
Adrian: Let’s go.
431 Nefeli: I will sit behind the right window to see the galaxies.
98 Ianthi: I will sit behind the left window to see the intracluster medium.
431 Nefeli: Aaaah, come quickly and see how wonderful the Coma cluster looks with all its galaxies.
98 Ianthi: Aaaah, look what I see! Did you know that these two massive galaxies emit X-rays? They both look like white dots! The intracluster medium that fills the entire cluster space appears as a purple cloud. And I love the color purple so much!
431 Nefeli: What wonderful experiences you give us Adrian! Thank you.
98 Ianthi: What did we learn today?
431 Nefeli: We learned that the shape of all things around us depends on how we look at them. For example, if I look at you 98 Ianthi in the optical I will see your skin and clothes. If I look at you in the X-ray I will see your bones.
Adrian: 98 Ianthi is always the same asteroid. But, in the different lights, other, initially invisible sides of herself are seen. For example, to X-ray her bones.
Adrian: Girls, it was very nice for me too. We have much more to learn if we sit here for a while near Coma cluster.
NOTES:
The Coma cluster of galaxies (left image): in X-rays, (right image): in the optical. The galaxies belonging to the cluster are visible in the optical. X-rays show the hot gas belonging to the cluster. Comparing the two images reveals that the shape of the cluster in X-rays is very different from that in the optical.
The nearly circular, concentric curves show the extent and shape of the intergalactic gas that fills all the space inside the cluster and emits the X-rays. These curves are plotted in both images to make it easier to compare the distribution of the intergalactic gas with the distribution of cluster galaxies. The colors in the left photo show the intensity of the radiation: areas of high intensity are shown in red. Areas of lower buoyancy are marked in blue.