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The story:

Astronomers discovered a huge star in a nearby galaxy last week.  R136a1, part of the Large Magellanic Cloud, is estimated to have a mass 265 times more than the sun and to shine around a million times more brightly.

Now, let’s clear up a bit of scientific jargon here as some people have got very upset over the fact that the star has been reported by some journalists as being the ‘biggest’ star ever to be discovered.   It is, in fact, the most ‘massive’ as many stars have been discovered that have a larger diameter (see video weblink below) but R136a1 is the star with the biggest mass.  How astronomers can calculate the mass of a star a mere 165,000 light years away though is beyond me.

Previously, astronomers didn’t think that they would find any stars more massive than the pistol star which is 150 times more massive than the Sun as it was thought that this was the upper limit of how massive stars could get. The star was discovered by using the Very Large Telescope in Chile (which can be referred to as big, massive or large without causing distress).

Teaching idea:

Most secondary school students find it difficult to comprehend just how massive objects in the Universe are (I once was asked by a 14 year-old student if the moon was bigger than the classroom).  The video in the weblinks below shows how the sizes of several planets and stars compare with each other to give them a really good idea of just how big things can get.  The biggest star shown here is VY Canis Majoris which has a radius around 1800-2100 times bigger than our Sun but it is not the most massive star.  This is because it is a red supergiant, so is near the end of its life having shed most of its mass.  (for comparison – R136a1 is thought to have a radious around 30 times bigger than the Sun).

This story will fit nicely into a lesson on stellar evolution.   The area of the galaxy that R136a1 was discovered is called the Tarantula nebula.  This could introduce the start of a star’s life cycle.

The star is thought to be middle-aged, much like our Sun.  But, unlike our Sun is not going to last very long.  Massive stars like R136a1 so not live very long lives and as they age they lose mass.  It is thought that the star is around a million years old, and at the start of its life it could have been nearer 320 times more massive than the Sun.  GCSE students who have studied how stars produce their energy could theorise why R136a1 has shrunk so significantly, and why VY Canis Majoris still holds the record for the biggest star but is not the most massive.  they could also predict how they think R136a1 will end its live:  Supernova and black hole perhaps?

Finally, the Very Large Telescope could be looked at as an example of a how telescopes can greatly improve our understanding of the universe.

Image: ESO/P. Crowther/C.J. Evans

These are some of the amazing images taken of the Tarantula nebula by the VLT.  On the left is a visible-light image along with a zoomed-in visible-light image in the centre.  The image on the right is taken with a near-infrared instrument.  The bright cluster of stars on the far-right contains R136a1.

As you can see, these high-resolution images of objects so far away mean that the VLT will surely be used to uncover yet more secrets of the Universe.

Anything to add?

Whilst writing this post, it’s always a possibility that I missed some other great information or teaching ideas. Feel free to share your thoughts.

Weblinks

News-story about the discover of R136a1.

Great video that compares the sizes of the planets in the Solar System, our Sun and then some really big stars.

Information on the Very large Telecsope (VLT).

Related posts:

1. A home from home? Solar system discovered like our own
2. The incredible shrinking Moon

Crystal structure of MOF-200 (Credit: UCLA Department of Chemistry and Biochemistry)

Many of the current science GCSE specifications require students to study nanotechnology so here are three exciting new applications to make this new area of science topical and interesting.

The stories

Carbon dioxide capture:

Capturing carbon dioxide before it reaches the atmosphere and adds to our ever-increasing blanket of greenhouse gases is not a new idea but Korean scientists working with UCLA have devised an extremely efficient way of doing this by harnessing the power of nanotechnology.

They have developed better breeds of a material known as MOFs, or metal–organic frameworks. These are sometimes known as ‘crystal sponges’ and are made of linked rods of zinc oxide which contain pores on the nanoscale which are exactly the right size to  capture and hold carbon dioxide molecules (see the image above).  The new MOFs are the most absorbent yet and researchers believe that they can’t do much better.  They work by having  a massive surface area to volume ratio.  If you take just one gram of the new MOF and unravel it, it will cover several football fields.

Smart bandages:

An international team of researchers who are working with the University of Bath have developed a bandage that has a two-fold function.  This bandage can not only tell doctors when a wound is infected but can release its own antibiotics to kill the pathogens.

Nano-capsules on the fabric of the bandage contain the dye and drug wrapped neatly up in a lipid membrane (see image). Pathogenic bacteria naturally secrete enzymes which break down the membrane, releasing the chemicals.  The dye alerts doctors to the fact that the wound has become infected, whilst the antibiotic gets to work eliminating the bacteria.

Lipid vesicles like these are used in smart bandages

Magnetic nanoparticles:

This is an exciting new area of research that has many applications in medicine.  One use is a non-surgical treatment of cancerous tumours.  Magnetic nano-particles are injected into the tumour and then an alternating magnetic field is used to heat the particles which destroys the cancerous cells.  Scientists are also developing ways of attaching monoclonal antibodies to the nanoparticles to search out and attach themselves to cancerous cells or for targeted drug delivery.

Teaching idea:

The class can be divided into groups – each group having an application of nanotechnology assigned to them.  Their challenge is to present to the rest of the class how their use works.  They could watch the videos shown on the websites below and see if they could do better (they probably could!)

Anything to add?

Whilst writing this post, it’s always a possibility that I missed some other great information or teaching ideas. Feel free to share your thoughts.

Weblinks

News story about smart bandages plus a short but informative video showing them in action.

News story on the new carbon dioxide capturing MOFs.

Applications for the magnetic nanoparticles plus an interview of a professor explaining them.

News story on the use of magnetic nanoparticles in medicine

Related posts:

1. A shining use of smart materials
2. What is the connection between custard and football?
3. Exciting new biotechnology

Over the last year there has been fevered speculation about what the world’s fastest growing internet company is really worth. $10bn, if judged by Microsoft buying a tiny stake of 1.6% in 2007. $15bn, if judged by the 2% stake bought by a Russian investment group in 2009.

But the growth in users has slowed (unless Facebook actually starts giving free smartphones away in India and China), and like any maturing business it needs to be valued on what cash it is actually generating for shareholders.

So firstly, the top line. Facebook gets around 260 bn page views per day.

By a few simple experiments with their advertising platform I reckon the average click through rate for their adverts is just below 0.01%. They serve 3 ads on each page, so that means 1 in around 3,500 pages could be revenue generating for them. But that assumes they have enough advert inventory to keep showing new ads to their users (who get bored easily); perhaps safer to assume only 1 in 5,000 pages generates click-through revenue (or the equivalent).

We’ll assume the average click-through advertising rate is 30 cents.

$0.30 x 5m clicks = $1.5m per day = $550m per year.

The costs are not insubstantial either though: 40,000 servers – which probably cost the best part of $200m to buy and set up – and storing maybe 100 petabytes of images, video and log data (80bn images alone).

There are also 250 engineers and support staff, which is about $60m of annual cost.

So we could be assume that their total operating expenses are around $200m a year. That still leaves a healthy profit of $250m.

That doesn’t account for any revenue from some of their more sophisticated cross-sell and data-mining ideas – which have caused such user outrage. Assuming they can find a non-contentious way to double the profits over a few years, and maintain their pageviews (if not their share of global traffic), the business could easily be valued at 20x EBITDA, which gets you to … $5bn.

So it looks like Facebook needs to go some way to prove it’s worth, mainly because not enough people click on ads. That’s why we haven’t served ads at Teachable so far: only one is a few thousand users actually find them useful.

The World Cup is finally over and to celebrate – one last football-related teaching idea:  What does it take to be a great goalie?

Nerves of steel, lightning-fast reactions times and perfect hand-eye coordination are top of my list. So the World’s top goalkeepers must have a great nervous system.

In this PowerPoint, students watch some of the greatest goal saves of all time and then test their knowledge of the nervous system to explain what happens in a goalie’s body as he tries to save a goal.  It can be used at the start of a GCSE topic on the nervous system or for a bit of revision before the exam.

To carry on this theme – why not get your students to find out who in the class would make the best goalie?  They can try out some online reaction-testing and hand-eye coordination tests (links below) and practice their data-collecting skills by drawing out tables and calculating averages.

Useful websites:

The four best saves of all time
Sheep dash online reaction times tester
Escapa – online hand-eye coordination test

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