The end result looks a little something like this:

This photo was taken as part of a joint effort by NASA, the ESA and SLACS service team.* The “halo” is actually a solid non disc shaped object, many billions of miles away behind the bright object in front.

*Credits for all photographs at the bottom of this article. Read them, you can use them to get more pictures!

So how does this work? When where they discovered? Why should we care? Read on dear reader, read on!

How a Normal Lens Works

In order to understand the importance that Einstein rings have, and how they work, we first need to understand the principle of a lens. As you probably well know, a lens works by bending light. If you need eye glasses, the lens on your eye does not bend the light properly and so your vision is blurred. Eye glasses compensate for this by bending the light a little extra one way or the other to compensate for the eye.

They do this using a simple method, and anyone who’s ever driven a car can relate to this. Imagine you’re driving after wet weather. The roads are mostly dry, but there are a few big puddles here and there (What’s your road tax paying for anyway!?). Suddenly, the right hand side wheels of your car hit a puddle, while the left ones stay on dry land. What happens? Your car is pulled to the right, and if you’re driving in Britain, you’re on the wrong side of the road. If you’re driving anywhere else, You’re on the pavement! The sudden extra resistance means one side of your car is moving faster than the other, so it turns, just like a tank!

The exact same thing happens when light hits a lens. As a lens is curved, one “bit” of the beam of light hits it a moment before the other, and so slows down. As the light is travelling in a beam (At this point we get into wave-particle duality, but let’s not worry about that now), the other side must curve towards the lens to keep the beam straight.

Oh and when your science teacher told you that the speed of light was constant, he didn’t add the clause ‘in a vacuum’ – light can be slowed down by passing through differing densities of matter.

Thus, the light is distorted and starts to travel at a new angle! It changes again when it leaves the glass of the lens (It’s transferring to a new density of matter), and is now travelling in a different direction. In the above example, the light is bent TWICE. Going in, it curves inwards towards the lens, and then again on the way out. If you used this lens, and looked at it from behind where the light beams cross into a “funnel” the image would be either upside down or back to front at the edges have swapped over!

Because God Needs a Prescription…

So, all very interesting, but what does this have to do with giant halos in space? Well, it’s very straightforward. The object between you and the halo in an Einstein ring is basically acting like a lens. But, it has a few very important differences:

• It uses gravity to bend the light and change the direction it’s travelling
• It’s likely if you put it in front of your eye, you won’t see anything (Except your own death)

I got this nice little diagram from the kind folks at wikipedia. Using the ultimate power of modern computing*, I have altered the diagram to turn it into a full 3D* representation of the Einstein ring system!

*Full power of modern computing may or may not be MS paint. Full 3D may or may not have just been a complete lie. Spell checker may or may not have been used.

Now the problem is that unless the observer (you), the object being distorted and the massive object are all in almost perfect alignment, we won’t see a ring. However, we may see a sort of bowl shaped image or a broken halo like these:

So are they just pretty, or do they tell us something?

Well, scientist are currently hunting for a thing called dark matter. According to the laws of gravity, the inside of our galaxy should spin faster than the outside, so stars close to the middle complete rotations faster that ones outside, just like our solar system.

But what’s actually been observed is that stars on the outside will complete their rotations at the same time starts in the middle complete theirs, like the spokes on a bicycle wheel. The only explanation as to why the galaxy isn’t shearing itself apart is that there must be more gravity in the outside of the galaxy that’s holding everything together. But no one can find anything that could be producing that gravity! So, therefore by observing Einstein rings, astronomers hope to identify some properties of this elusive “dark matter”. Dark matter and it’s twin dark energy will be explored by myself in an upcoming article, to keep an eye open for it, bookmark my research page “The blog of many things (Bonus points if you get the reference)!

In Closing

I”m going to finish off with some more pictures of Einstein rings. Interestingly, Einstein himself thought we’d never actually see this effect, though he did predict it would exist under his theory of relativity. He reasoned that the distance required for this effect to take place was so great that we would never have telescopes that could actually see them. I wonder what else he thought we’d never see eh?

How many Einstein rings can you spot in this picture?

Credits, where credit is due!

All images where provided by the ESA and NASA. These Hubble images are free of copyright and can be enjoyed and spread by everyone.

The (Edited) diagrams of a lens, and how an Einstein ring is formed where based on a diagrams in the public domain, copied from wikipedia.

• Research was carried out using the ESA NASA Hubble page, (Linked above)
• The Book BANG! By Patrick Moore (A personal hero who I heard lecture in person many years ago), Brian May and Chris Lintott
• www.theuniversetoday.com
• Harvard Science.
• There are many places to research astronomy, try your local library, the internet and even your local college or university for open lectures

Why not check out this article in science fiction concepts about to become a reality!