The James Webb Space Telescope is just about ready and set up far far above Earth right now. You may have heard about it and how much of an upgrade it is on the Hubble Telescope. The Hubble Telescope has produced some of the most incredible images humans have ever seen. This month’s post is pushing the definition of “molecule” of the month to its limit because we’re going to talk about brilliant beryllium!
So… it’s not quite a molecule
Beryllium can form a metal. A metal is not made up of molecules the same way that a plastic is.
A plastic is made up from lots of individual molecules that then get chained together to make massive long strings. These strings all tangle around each other. This tangling is what gives the plastic its strength. Changing the individual molecules in there, how long the chains are, and how tangled and tied together those chains are, changes the properties of the plastic material.
The Mettle of Metals
A metal, on the other hand, has atoms of metals – like beryllium – all sharing their electrons to form a big sloshy soup of charge that holds together all the metal atoms into a big block.
So instead of changing the material properties by changing the molecules or chain length and linkages in plastic, in metals we could change the way the metal atoms share their electrons and how all the atoms end up lining up and arranging near each other.
The first one – changing the way the atoms share their electrons – can be done by introducing a range of different elements into a mixture. Some elements will release their electrons easily, some grab hold of them really tightly. We call a metal that is made of a mixture of elements an alloy. They can have wildly different properties to the metals made up of pure elements!
The second one – how the atoms in the metal line up – can be changed by adding all sorts of things that stop all the atoms forming nice neat orderly lines. Think about how much easier it is to walk through lines of people all queueing neatly compared with a crowd. A good example of this is carbon added to iron to make steel. Steel is much different to iron thanks to the changes to the arrangement of all those atoms.
Anyway, back to beryllium, and what it has to do with the James Webb Space Telescope.
In a Galaxy Far, Far Away
This telescope is an incredible feat of engineering. The basic gist is to have a special camera that can see infrared radiation (think heat – red glowing metal elements in the toaster for example) and a series of mirrors that can bounce lots of light from distant stars onto that camera.
The mirror has a total area of about a tennis court. It is beautifully shiny thanks to the ability of gold to reflect light (especially infrared) brilliantly! The technical term for this is lustre. But if we have an area the size of a tennis court made entirely of gold we have some massive problems…
- It would be so impossibly expensive to produce
- The mirror would be so heavy that we would need to tie together all the rockets in the world to launch the telescope into place
- It would take so much fuel to keep in place that it would only operate for a month or two
So scientists needed a material that they could make all these mirror segments out of and coat with an incredibly thin layer of gold that is cheaper and much lighter.
Tennis, Mirrors and Gold
Using this thin layer of gold means that to cover the whole of this tennis court area needs just 18 golf ball sized hunks of gold. Imagine squishing 18 golf balls and seeing how much of the tennis court they would cover. This is a very, very thin layer.
If you look at the periodic table you can see why gold is so heavy. It’s symbol (Au) is quite a few rows down and far over the the right. Generally the further down and right you go in this table the heavier things get!
Instead we want a material we can use to make the framework of this telescope’s mirror that will be light so where on the periodic table should we look? If you can’t remember the Periodic Table, you can check it out here and here!
Twinkle, Twinkle, Little Beryl…
If you said top left, well done!
That’s where beryllium is. It’s mass number is 9 atomic units versus gold’s 197. It’s more than 20 times lighter.
There are some added benefits too. Remember we said that the camera on this telescope is looking for infrared – heat – from distant stars? Well if this telescope is somewhere hot then it will never be able to detect any heat from far away! Instead this telescope is being parked just behind Earth, hiding away from our Sun in Earth’s shadow. It’s just on the edge of this shadow so that it can still charge its batteries with solar power from bits of sunlight getting around the Earth. Then there’s an enormous heat shield made of plastic with thin metal films on them to reflect heat away and keep the detector of the telescope really cold.
So to make this telescope work we’ve needed plastics and metals – the plastics are great for being folded up and stored away and being flexible. The metals are great for their ability to reflect light perfectly (gold) and being very light (beryllium).
Tell Me More About Beryllium
Beryllium takes it name from the mineral beryl. Beryls include gemstones such as aquamarine and emerald. Both of these shiny gems contain the beryllium. In fact, one way to obtain pure beryllium is from these gemstones.
Beryllium is not the most common element on Earth. However, several countries do specialize in producing lots and lots of beryllium each year. Apart from space mirrors, this element is also used in alloys. Adding beryllium improves the electrical and thermal properties of the metal.
In its pure form, beryllium is a silver-white softish metal. Like many metals, it has a high melting and boiling point.
However, beryllium and its compounds are toxic. Inhaling beryllium dust can inflame the lungs and cause a condition known as berylliosis – nasty!
118 Is a Lot of Choice
It’s fair to say that beryllium is not as famous as gold. On their own, each element has its own properties and uses. However, by bringing them together, we can create better materials, to solve very specific problems.
This is the beauty of chemistry. We can make chemicals and materials behave exactly how we want by tweaking the chemicals we add to them. There are, after all, 118 different elements to choose from! Pretty soon we’re going to see the first images from the James Webb Space Telescope! I hope you think about our friend Beryllium when you do see them.