I'm writing this post for my Mother who for years has pondered this question: "You were so good at maths at school, why didn't you become an accountant?"

There is nothing wrong with accountants. Let's get that statement out of the way now. Without my wonderful accountant my books would balance like a one legged kangaroo on a wine cruise.

But a Maths degree was not for me. A career in accountancy was not for me (and I'd like to point out here - as much for my Mum's benefit as anyone else's - that accountancy is not the only career you can get out of a Maths degree).

I always struggled to explain why Physics holds a place in my heart that Mathematics never did.

Then, I started reading a wonderful book "Fermat's Last Theorem" by Simon Singh, which is a fascinating account of an equation whose proof stumped mathematicians for the best part of 300 years. (I've put a few more details on Fermat's Last Theorem at the end of this post.)

It tells the tale of finding a proof to an equation that originates from Pythagoras' Theorem. You know, that much-taught equation you probably came across at school: the sum of the square of the longest side of a right-angled triangle equals the square of the sum of the other two sides.

With a little mathematical jiggery-pokery it's easy to prove why this equation is true for every right-angled triangle you could throw at it.

This is known as a mathematical proof. It is true everywhere and for all eternity.

​Now, a mathematical proof is a thing of beauty. To unequivocally prove a concept and sit back in the knowledge that no one will ever disprove your work is something that eludes physicists. I think that's what makes physics so much fun - and why I chose it over mathematics.

Let me explain why with a tale of neutrinos.

A neutrino is a tiny particle that's caused a massive amount of upset within the scientific community. Don't blame the neutrino though - it's actually our tiny human minds that are at fault.

First, the neutrino has a very small mass (electrons are about 500,000 times more massive). But the neutrino shouldn't have any mass at all.

Why? Because this mass doesn't fit with our best explanation of all the particles in the universe: the Standard Model. (There are actually a couple of other problems with the Standard Model - it doesn't include gravity or dark matter, for example. But I digress.)

Second, scientists found evidence that neutrinos may travel faster than light.

Why would this matter? Because if something were to travel faster than light it would pretty much break everything we know about physics.

​This excellent post describes the implications and states: "When you assume that it's possible to travel faster than the speed of light, you're taking the laws of physics and punching them in the stomach and throwing them down the stairs."

​Yikes.

Naturally, this result caused quite a stir in the science community. Particle physicist and TV presenter Professor Brian Cox claimed it would be "most profound discovery in physics for more than a century." 

Fellow physicist and TV presenter Professor Jim Al-Khalili was a little more bullish in his response and claimed that if the findings were proved to be correct, "I will eat my boxer shorts on live TV".

In the end, Jim didn't have to ingest any underwear. The findings were eventually debunked by a range of other experiments that attempted to verify the results and the cause of the anomalous results was discovered to be a loose fibre optic wire.

But what a shame - and not just because two of the scientific team's elected leaders lost a vote of no confidence and tendered their resignations (click here for a brilliant piece where one of the leaders, Antonio Ereditato, is interviewed about the case).

It's a shame because the result wasn't verified.

Can you imagine if it had been? If we had unwittingly proven that matter could travel faster than light?

What a wonderful world physics is where we don't just disregard a result because it doesn't fit. Teams of physicists swooped in and immediately tried to recreate the result. They tested it until there could be no doubt that there was an anomaly.

It is this lack of perfection and need to endlessly test and question everything that makes physics so very appealing to me.

​Maths is too tidy.

As I reach the end of the Singh's beautifully written tale of Fermat's Last Theorem, I suddenly realise that I'm wrong about maths.

You see, mathematical proofs are a thing of perfection. But they are also the pursuit of a few dedicated souls who won't rest until that perfection is found.

​​Andrew Wiles, who eventually cracked the Fermat's Last Theorem nut, announced his findings in June 1993. The proof took decades to devise - and in August 1993 it was found to contain an error.

After a breakthrough in September 1994, Wiles published the corrected proof in 1995.

So, I am wrong. Maths is not tidy. It's just as messy and open to criticism, verification and debate as physics.

​The ability of scientists of any discipline to work relentlessly, debate, discuss and open their minds to the seemingly impossible is what makes every discipline so wonderful.

Maybe it's finally time to apply for a degree in mathematics.

If you take Pythagoras' Theorem and replace the square by any number greater than two, then you will never get a solution. In other words:

It's a devilishly simple equation that anyone can understand - but finding a proof for this equation taunted mathematicians for centuries.

What didn't help was that French "amateur" mathematician Pierre de Fermat tantalisingly claimed to have found the mathematical proof to this equation but never wrote it down - an irritating quirk which he was notorious for. 

Rewind 20 years. I'm a physics and astrophysics undergraduate. When asked what I'm studying, I get two stock responses: 1. You must be really clever, 2. That's unusual for a girl.

These words, no matter how bland or inoffensive they appear on the surface, actually cut pretty deep. They knocked my confidence and made me question whether I deserved a place in the physics department. 

Now, I have a pretty thick skin. The ditty "sticks and stones may break my bones, but words will never hurt me" sums up my awkward teenage years pretty well. But these two responses formed part of a wider offensive of comments I'd received during my formative years whenever I mentioned my ambitions to study physics.

It felt like society was, at best, confused as to why a girl would want to study science and, at worst, thought STEM subjects should be left to the boys. 

Such words cause a crisis of confidence.

An inherent lack of confidence amongst aspiring women in technology is regularly cited as a core reason why girls turn away from STEM subjects. Recent research from Microsoft found girls in the UK are interested in science and tech subjects before the age of 11, but this drops sharply when they turn 16. So, what's happening in that intervening five years?

I'd like to turn to one of the 1,000 girls who took part in the Microsoft survey. Paisley Edwards, a 12-year-old from Croydon, who highlights the importance of having more positive female role models in science, like her Mum who's a pharmaceutical scientist.

​However, it is this quote from Paisley that so succinctly addresses the first comment that I 'must be clever' to do physics:

​You see, the thing that always got me with that 'you must be clever' response is the way it would be said. Immediately, a wall was put up. People bristled, put my degree subject in the "too difficult to understand or talk about" box, smiled and moved on. 

This always baffled me. Science is just my thing. I'm not sure if that makes me clever or not. It just makes sense to me. (​But ask me to bake a cake or drive a car and I'm lost, sweating and swearing  - usually in that order.)

While none of my male colleagues seemed to be told they were clever for studying physics, this is not purely a gender-specific issue. It's a science-specific issue. 

A divide between the science community and wider society still exists, despite the best efforts of many wonderful science communicators (a topic I've covered into the past - even pulling poor Brian Cox into the debate).

The stereotypical socially awkward geeks so regularly portrayed in shows like The Big Bang Theory don't help. They make science seem impenetrable and an exclusive topic of an intellectually elite few.

In fact, science is simple. Science is changing the world we live in and any good scientist will happily discuss their work or topic you take an interest in. To quote physicist extraordinaire, Richard Feymann: "If you can't explain something in simple terms, you don't understand it."

​Trust me, I talk to scientists for a living. It's a fascinating world and one that'll open your eyes to the wonder of the world around us.

OK, now let's look at the second stock response. I was one of five women studying physics out of a class of 100 back in 2000 when I started my first Masters in Physics. So, yes, it was unusual for a girl.

Just as being a male midwife still raises eyebrows with some, as only 99.6% of UK midwives are men.

A use of words, again, is to blame - and it affects both men and women. This fascinating study from Totaljobs used previous academic research from The University of Waterloo and Duke University, which outlined a series of male and female gender-coded words.

Totaljobs analysed almost 77,000 job adverts over a six week period to assess the frequency of gender-coded words in UK recruitment and found 478,175 words that carry gender bias in these ads.

​That's an average of six male-coded or female-coded words per job advert.

Looking at these words, it breaks my heart. We're ALL a wonderful mix of attributes and these words are used without thinking to pander to the stereotypes of a society where boys are clever and leaders, and girls are pretty and submissive (I'm looking at you, Clarks Shoes, for calling girls' shoes "dolly babe" and the boys' equivalent "leader").

Yes, I'm a woman who loves science. I also have a husband who is far better in the kitchen than me. What does that say about us? Bugger all.

Instead of pointing out what's different, we need to embrace our differences or we end up living in a Trump-fuelled toxic world where CERN has to launch an (albeit brilliantly worded) anti-sexual harassment campaign and even the most experienced female scientists feel they do not have a place in the world's laboratories.

Instead, we need to start using words to help women in science. Jess Wade is leading the way here and is steadily setting up Wikipedia pages for all those women in science without the recognition they deserve. 

​Let's start using the power of words to change things so science is never seen as an elusive topic, or one that's purely for the boys.

And when someone tells you they're studying physics, don't dismiss them as being too clever or unusual.

​Ask them to tell you more.

Where do I start with a post about Friday night's Space Shambles event? It's difficult to know because the night itself was such a glorious mess of laughter, science and song that there wasn't any discernible start or end. Just a constant stream of bonkers and brilliant stuff.

Hosted by Infinite Monkey Cager Robin Ince and guitar-wielding spacewalker Chris Hadfield, we saw Apollo 9 astronaut Rusty Schweickart (who flew a real Lunar Module) play the retro video game Lunar Lander (he did quite well), UK science comedy troupe Spoken Nerd calculate Pi with a pie and comedian Stewart Lee robustly declare he "hates nothing more than space people" before shooting down the entire premise of space travel in one fantastic monologue. (Little known fact: Lee has flown to space in his bin and it's not that hard. Also, don't ask him how to go to the loo in space.)

These skits were interspersed with a great selection of scientists, whose six-minute lectures gave powerful pulsar-like blasts of knowledge into the audience. 

Space scientist Monica Grady dazzled with her talk on Rosetta (leaving me with the ear worm "Rubber Ducky, you're my friend'), physicist Lucie Green showed a tiny piece of Skylab to us, physicist and oceanographer Helen Czerski was joined on stage by Kimokeo Kapahulehua, a Hawaiian native who spoke about canoes, navigation and the stars, Jim Al-Khalil somehow summed up the history and future of the universe in six minutes, and a round table answering questions from the audience ensued with the Sky at Night's Chris Lintott, planetary scientist Suzie Imber and Hadfield, who revealed that space smells of witches.

That's right. Witches. Or at least the smell they leave behind when they disappear in a puff of smoke. Which makes far more sense. Right? (Well, it's a lot more fun than Brian Cox's postulation on the smell of space during his arena tour!)

We were treated to music from Grace Petrie (one of the many goosebump-inducing moments of the night when she sang her Golden Record Song), Public Service Broadcasting, She Makes War and onstage band Steve Pretty and the Origin of Species. (Who started the show with a laser harp. Brilliant.) Chris Hadfield also got out his trusty guitar and sang a bit of Bowie, later joined by Sheila Atim, who finished the song with a powerful vocal punch.

And with actor, writer and comedian Reece Shearsmith's beautiful rendition of Carl Sagan's Pale Blue Dot and a delightful, final poem penned and performed by Robin Ince, the night couldn't have thrown a better paraphernalia of science and intrigue out into the Albert Hall, all overlooked by a mesmerising spacesuit-wearing puppet called Sam.

Space Shambles was a night of gentle chaos and science. Because, after all, science isn't ordered, it's chaotic.

Which all seems quite fitting given that a few hours before Space Shambles began its tour de force of science, one of the world's greatest scientist's, Stephen Hawking, was interred in Westminster Abbey. Hadfield paid a touching tribute to Hawking, along with Apollo astronauts Alan Bean and John Young. 

Before his death, Hawking requested a single equation should be inscribed on his grave. This equation demonstrates that black holes aren’t entirely black after all, and instead emit a glow that became known as Hawking radiation.

Even Hawking was surprised by his own work. Speaking about this equation, Hawking said: "At first, I thought this must be a mistake in my calculation. But what persuaded me that it was real, was that the emission was exactly what was required to identify the area of the horizon with the entropy of a black hole."

Entropy is an odd beast to describe (I had a bash with some Lego, here) - it's often regarded as a measure of disorder, and sometimes a measure of information. 

Well, Space Shambles was a night of disorder and information in equal value. I certainly wouldn't have changed it for the world.

Science doesn't only belong in stuffy lecture halls or cordoned off in a lab. It belongs in the Albert Hall surrounded by musicians, comedians and a 5,000-strong audience.

We all need a little more science and chaos in our lives.

​Well played, Space Shambles. 

Enjoy the journey, Professor Hawking.

A neutrino is a tiny subatomic particle.

It's also one of the most abundant particles in the universe.

In fact, there are roughly 65 billion neutrinos passing through your body right now.

Did you notice them? 

No?

That's because neutrinos barely interact with matter, which makes them really difficult to detect.

To detect anything you can't "see" like a neutrino, scientists usually use one of the four fundamental forces to "see" how a particle interacts with matter. 

These four fundamental forces are: the electromagnetic force, gravity, the weak force and the strong force.

Neutrinos have a neutral charge and a very small mass. So, you can't detect them with the electromagnetic force (because they have no charge) or easily detect them with gravity (because they are so light and tiny).

And neutrinos do not interact with the strong force (which bonds protons and neutrons together in an atom's nucleus) because they simply do not feel it.

Neutrinos are only affected by the weak force, which has a tiny range and is involved in the decay of nuclear particles. The problem is, the chances of a neutrino interacting with the weak force are incredibly small.

This post explains the (quite frankly, bonkers) process of detecting neutrinos rather well.

This year, we could see some exciting neutrino news as a huge, extraordinary machine called KATRIN (KArlsruhe TRItium Neutrino) will try to determine the mass of the neutrino once and for all. This is a lovely article all about the experiment.

In fact, there are quite a few neutrino-based experiments going on around the world: here's a list of the lot.

This is an excellent series of in-depth articles from Berkeley that give more details about neutrinos and the implications of neutrino mass.

And if you want to find out more about the experiments that hinted neutrino mass could explain why we live in a matter universe, check out this article from New Scientist.

The meteoric rise (and fall) of Bitcoin has peaked the world's interest in the technology behind it - blockchain. But the implications and applications for blockchain technology go way beyond cryptocurrencies...

For once, the word "blockchain" actually describes this technology quite well.

A "block" is simply a record of new transactions. This could be a record of a cryptocurrency purchase or medical records or any chunk of data.

Once a transaction is completed, the "block" is encrypted and added to a "chain".

The encryption process is known as "hashing" and it's carried out by lots of computers. If they all agree on the answer, each block gets a unique digital signature.

This creates a chain of encrypted blocks.

Or, a blockchain.

Each block is stored chronologically and the chain cannot be altered or tampered with, only added to. And, when a change does happen, the blockchain is updated for everyone in the network at the same time.

You can only make a change if you have a private key (aka password) to access the block.

A popular analogy is to think of blockchain as a Google doc and traditional data storage as an old-school Microsoft Word doc. 

The Google doc can be simultaneously viewed and edited by everyone with access to that document.

With a Word doc, you have to send the document to one person at a time, ask them to make a change and then send it back before you send it to the next person.

Blockchain is a completely different way to store data, compared to the traditional process of storing your data in a big central database.

Using blockchain, data is distributed across a network of computers and not in one place. Here’s another useful explanation from online forum Bitcoin Talk:

Blockchain is basically giving two people a safe way to exchange data, without the need for a third party (such as a bank) to verify the transaction. 

If you think about traditional transactions, there are three parties involved: the owner (who holds an asset), the market (everyone who is interested and/or able to buy that asset) and the regulator (who makes sure the owner and market follow the rules when a transaction happens).

With blockchain, we don't need a regulator as the network of computers validates a transaction.

​This could have wide-reaching implications for banks - and a wealth of other industries too.

While blockchain is synonymous with Bitcoin and other cryptocurrencies at the moment, there are many different ways it could be used.

​A recent UK government report on blockchain technologies provides a good overview and examples of the use of blockchain, as does this article from The Conversation.

In the last 10 days, we were treated to a Super Blue Blood Moon AND the first flight of the SpaceX Falcon Heavy rocket. If Musk's dreams are realised, we may be shuttling humans to and from the Moon in a matter of years.

It's so exciting to see space travel peaking the world's interest again. And, for most interstellar journeys, it all starts with the Moon.

Our Moon is quite unusual compared to other moons in the Solar System because it is the largest moon compared to the size of its host planet. Big Moons should orbit big planets. 

But that's assuming that our Moon formed in the same way many other moons did: when a planet is forming, some of the material is pulled together to form a moon. This is known as accretion.

But our Moon's composition is too dissimilar to the Earth for this to have happened. So, we believe the Moon was formed when a Mars-size body called Theia collided with the early Earth. Dramatic stuff.

Sadly, not cheese. It's predominantly made of rock and the dusty surface is covered with impact craters and dead volcanoes. These craters formed from asteroid collision millions of years ago but, because there's no weather, you can still see them today.

One of the goals of the Apollo 16 mission was to "pick up rocks", according to astronaut Charlie Duke. The Apollo 16 mission collected nearly 213 pounds of rock and soil samples and, despite extensive geological training, Charlie admitted they chose to "pick up one of every colour" on the lunar surface. 

Under the surface, the Moon is likely to have a small core of iron and a thick mantle of rocks rich in iron and magnesium.

Here's a final interesting fact about the Moon and its average 238,855 mile distance from the Earth. You could fit every planet in the Solar System between the Moon and Earth.

Yes. The Moon's gravity pulls the Earth and causes the tides in our oceans. The pull of the Moon is also slowing the Earth's rotation down, causing every day to increase by 2.3 milliseconds every century. And the Moon is also getting 1.5 inches further away from the Earth every year.

We also believe that the Moon's gravitational effect on the Earth caused it to tilt at just the right angle to produce  a relatively stable climate over billions of years. This effect, combined with the planet's tides, allowed life to flourish. 

So, if there was no Moon, there may be no life on Earth.

If you want to find out more about exploration of the Moon, this post from National Geographic is a great starting point. And here are some great lunar stats.

SpaceX is not the only entity interested in going to the Moon. Five missions are planned in 2018, including: a Chinese mission to land a rover on the far side and the Chandrayaan-2, which has been developed by the Indian Space Research Organisation and will include a moon orbiter and a rover.

Two of the other lunar missions will be privately-funded. These are Hakuto, a group of space professionals inspired by Google’s Lunar X Prize, and Part-Time Scientists, a group of volunteer scientists and engineers based in Germany that plan to use SpaceX rockets and deploy two rovers. Finally, NASA’s TESS will also perform a flyby of the Moon.

The colonisation of the Moon is another fascinating prospect. And one that we're getting closer to realising. And if you're wondering why we should go to the Moon in the first place, this post from NASA is a rich pool of resources. 

​There's also great fun to be had on the Moon, if this video is anything to go by:

 Wormholes are theoretical passages through space-time that could create shortcuts across the universe.

They're also a staple sci-fi phenomenon and are predicted by the theory of General Relativity.

Let's take a step back and we need to understand a few other scientific terms. General Relativity predicts the existence of Black Holes - singularities in space that are infinitely small and infinitely dense with such a strong gravitational pull that nothing (not even light) can escape there pull once you get close enough to one (past a line known as the event horizon).
 
Then, in 1916, Austrian physicist Ludwig Flamm took the concept of black holes and noticed another solution was possible - a white hole. As the name suggests, this is the opposite of a black hole and ejects matter from its event horizon.

White holes have a lot of jolly interesting consequences. Some suggest the Big Bang might have been the result of a supermassive white hole.

But (and here's where we get to wormholes) Flamm also suggested that black holes and white holes may be connected by some sort of tunnel through space-time. This tunnel provides a shortcut between two areas of space-time.

Some 20 years later, American theoretical physicist John Archibald Wheeler coined the phrase "wormhole" to describe that tunnel connecting black and white holes.

Maybe... but there are several rather large (or small) issues to overcome. The first is to do with size: wormholes are predicted to exist on microscopic levels (a thousandth of a million, million, million, million, million centimetres). However, as the universe expands, then so could the size of a wormhole.

Second, wormholes aren't very stable and, therefore, don't last very long (unless they're filled with exotic material like negative matter).

But that's not deterred some scientists. A recent article by physicist Ethan Siegel detailed how humans could travel through a wormhole.

Wormholes are a hot topic in science and NASA even dedicated $1.2 million to its "Breakthrough Propulsion Physics Project" between 1996 and 2002, which studied various proposals for revolutionary space travel theories that would require major breakthroughs in physics to be realised.

This is a more in-depth article about wormholes and this lecture from Stephen Hawking covers the possibilities of time travel using wormholes.

When a suitably massive star comes to the end of its life, it collapses in on itself in a massive supernova explosion. If that original star was between 10 and 29 solar masses it collapses to the point where the protons and electrons in its core are squashed together leaving behind a neutron star.

Neutron stars are incredibly small and incredibly dense. They cram roughly 1.3 to 2.5 solar masses into a sphere of roughly a few miles in diameter.

If we could extract just one sugar-cube sized piece of a neutron star, it would weigh more than one billion tons. That's equivalent to the weight of Mount Everest.

If the neutron star weighs more than three solar masses, it will continue to collapse in on itself to form a black hole.

Neutron stars also have very large magnetic fields (approximately one trillion times stronger than the Earth's magnetic field) and are the strongest magnets in the universe. They have a surface temperature of one million Kelvin (the Sun's surface temperature is 5,778 Kelvin).

Magnetars are another type of neutron star. The magnetic field of a neutron star is one trillion times that on Earth, but the magnetic field of a magnetar is another 1,000 times stronger.

In all neutron stars, the star's crust is linked to its magnetic field so that any change in one affects the other.

So, a small movement in the crust will cause ripples in the magnetic field. For a magnetar, such movement cause a huge burst of electromagnetic radiation. In December 2004, a massive magnetar blast blinded satellites and partially ionised the Earth's atmosphere. The cosmic blast only lasted one-tenth of a second but it released more energy than the Sun has emitted in 100,000 years.

* No Ironmen were harmed in the making of this Sunday Science.

When two neutron stars smashed into each other in August, we weren't quite sure what was left over. But it's looking increasingly likely that it could be the biggest neutron star we've ever detected. The unprecedented celestial collision produced a gamma-ray burst and astronomers at LIGO detected the resulting gravitational waves.

If you'd like to find out more about why pulsars spin so fast and so regularly, you can read more here.

The story of the discovery of pulsars is also one of my favourite astronomy anecdotes as it features a great female scientist, Jocelyn Burnell (nee Bell). I've copied and pasted this fantastic article from the American Society of Physics covering the discovery:

"In 1967, when Jocelyn Bell, then a graduate student in astronomy, noticed a strange “bit of scruff” in the data coming from her radio telescope, she and her advisor Anthony Hewish initially thought they might have detected a signal from an extraterrestrial civilization. It turned out not be aliens, but it was still quite exciting: they had discovered the first pulsar. They announced their discovery in February 1968.

Bell, who was born in Ireland in 1943, was inspired by her high school physics teacher to study science, and went to Cambridge to pursue her Ph.D. in astronomy. Bell’s project, with advisor Anthony Hewish, involved using a new technique, interplanetary scintillation, to observe quasars. Because quasars scintillate more than other objects, Hewish thought the technique would be a good way to study them, and he designed a radio telescope to do so.

Working at the Mullard Radio Astronomy Observatory, near Cambridge, starting in 1965 Bell spent about two years building the new telescope, with the help of several other students. Together they hammered over 1000 posts, strung over 2000 dipole antennas between them, and connected it all up with 120 miles of wire and cable. The finished telescope covered an area of about four and a half acres.

They started operating the telescope in July 1967, while construction was still going on. Bell had responsibility for operating the telescope and analyzing the data — nearly 100 feet of paper every day–by hand. She soon learned to recognize scintillating sources and interference.

Within a few weeks Bell noticed something odd in the data, what she called a bit of “scruff.” The signal didn’t look quite like a scintillating source or like manmade interference. She soon realized it was a regular signal, consistently coming from the same patch of sky.

No known natural sources would produce such a signal. Bell and Hewish began to rule out various sources of human interference, including other radio astronomers, radar reflected off the moon, television signals, orbiting satellites, and even possible effects from a large corrugated metal building near the telescope. None of those could explain the strange signal.

The signal, a series of sharp pulses that came every 1.3 seconds, seemed too fast to be coming from anything like a star. Bell and Hewish jokingly called the new source LGM-1, for “Little Green Men.” (It was later renamed.)

But soon they managed to rule out extraterrestrial life as the source of the signal, when Bell noticed another similar signal, this time a series of pulses arriving 1.2 seconds apart, coming from an entirely different area of the sky. It seemed quite unlikely that two separate groups of aliens were trying to communicate with them at the same time, from completely different locations. Over Christmas 1967, Bell noticed two more such bits of scruff, bringing the total to four.

By the end of January, Bell and Hewish submitted a paper to Nature describing the first pulsar. In February, a few days before the paper was published, Hewish gave a seminar in Cambridge to announce the discovery, though they still had not determined the nature of the source.

The announcement caused quite a stir. The press jumped on the story–the possible finding of extraterrestrial life was too hard to resist. They became even more excited when they learned that a woman was involved in the discovery. Bell later recalled the media attention in a speech about the discovery: “I had my photograph taken standing on a bank, sitting on a bank, standing on a bank examining bogus records, sitting on a bank examining bogus records. Meanwhile the journalists were asking relevant questions like was I taller than or not quite as tall as Princess Margaret, and how many boyfriends did I have at a time?”

Other astronomers were also energized by the finding, and joined in a race to discover more pulsars and to figure out what these strange sources were. By the end of 1968, dozens of pulsars had been detected. Soon Thomas Gold showed that pulsars are actually rapidly rotating neutron stars. Neutron stars were predicted in 1933, but not detected until the discovery of pulsars. These extremely dense stars, which form from the collapsed remnants of massive stars after a supernova, have strong magnetic fields that are not aligned with the star’s rotation axis. The strong field and rapid rotation produces a beam of radiation that sweeps around as the star spins. On Earth, we see this as a series of pulses as the neutron star rotates, like a beam of light from a lighthouse.

After discovering the first pulsars, Jocelyn Bell finished her analysis of radio sources, completed her PhD, got married and changed her name to Burnell. She left radio astronomy for gamma ray astronomy and then x-ray astronomy, though her career was hindered by her husband’s frequent moves and her decision to work part time while raising her son. Anthony Hewish won the Nobel Prize in 1974 for the discovery of the first pulsars. Over 1000 pulsars are now known.**

As for little green men, they haven’t been found yet, but projects such as the Search for Extra Terrestrial Intelligence (SETI) are still looking for them."
​
** Now, more than 2,000 pulsars have been discovered, but this figure was accurate in 2006 when the article was originally published.

If a star has enough mass, it will explode in a monumental supernova explosion at the end of its life.

When a supernova occurs, it burns brighter than an entire galaxy and radiates more energy than our Sun will in its entire lifetime, all within just over a minute. According to NASA, supernovae are “the largest explosion that takes place in space.”

​For a supernova to happen, the star must be between eight and 15 solar masses. One supernova also occurs roughly every second in our universe, but you can't see them all. In fact, a supernova occurs in our galaxy once roughly every 50 years.

Most of the universe's chemical elements are also made in a supernova thanks to the phenomenal heat and pressure in these explosions.

There are two ways a star can go supernova.

A star can pull matter from a nearby neighbour until it has sufficient mass that a runaway nuclear reaction starts and ends in a supernova explosion.

For a Type I supernovae, a White Dwarf usually pulls matter from its companion star in a binary system and builds up enough mass to go supernova.

Type 1 supernovae are thought to blaze with equal brightness at their peaks, so they are used by astronomers as "standard candles" to measure cosmic distances.

A large star runs out of nuclear fuel and collapses under its own gravity. But, instead of ballooning to a Red Giant and contracting to a White Dwarf, it explodes in a supernova. 

Before it reaches the supernova stage, heavier elements gradually build up in the centre of the star. The star forms layers, like an onion, with the heavier elements sat at the centre and the lighter ones towards the outside.

Once the star has built up enough mass (and passes something called the Chandrasekhar limit) the star implodes. The core heats up and becomes even denser before the outer layers are thrown off in a dramatic supernova explosion.

A neutron star is left behind. We'll look at neutron stars next week.

If the original star is 25 times more massive than our Sun, a black hole is left behind. And if the star is more than 100 times more massive than our Sun, nothing is left behind. The star just explodes and leaves nothing behind.

I've oversimplified here as there are three subsets of the type I supernovae: Ia, Ib and Ic. The Ia category supernovae begin as the binary systems we described earlier where the White Dwarf pulls matter from its companion.

Type Ib and Ic supernovae are caused by the implosion of massive stars that have already shed some of their outer layers. Type Ib has lost its hydrogen layer and Type Ic has lost its hydrogen and helium layers.

But supernovae don't like to conform. For example, a very bizarre supernova was recently detected that explodes again and again.

NASA also managed to catch a supernova explosion with the Kepler Space Telescope last year. This animation was produced from the telescope's data as it recorded the supernova:

The other week, I explained how a dying star balloons into a Red Giant when it runs out of fuel. The next stage in this evolution is a White Dwarf.

A Red Giant will eventually blow off the material contained in its outer layers. These expelled outer layers may go on to form planets (more on that later).

All that's left behind is a small and incredibly dense and hot core.

This is a White Dwarf. 

Sirius B (pictured above) is a White Dwarf. Its mass is 98 percent of our own Sun but it is only 12,000 kilometres in diameter, making it smaller than even the Earth and much denser. 

Because they are small and incredibly dense, the gravity on the surface of a typical White Dwarf is around 350,000 times stronger than the gravity on Earth.

No hydrogen fusion occurs to counteract the force of gravity. So, all the matter gets squashed together until all the electrons are pushed far further together than for normal matter.

When all the electrons are squashed together, the matter is now known as a "degenerate" gas. It can't be squashed any further as quantum mechanics dictates there is no more available space for the electrons.​

No. Smaller stars, such as Red Dwarfs, don't reach the Red Giant stage and just burn through all their hydrogen. They should then evolve into White Dwarfs - but Red Dwarfs take trillions of years to consume their hydrogen fuel (which is longer than the age of the universe) so none have gone through this transformation yet.

Massive stars, which are about eight times the mass of our Sun, will never be white dwarfs. Instead, they explode in a violent supernova and either leave behind a black hole or a neutron star. We'll look into the massive supernova explosions that form neutron stars next week...

Many White Dwarfs will fade and eventually become Black Dwarfs when all their energy is radiated away.

However, if a White Dwarf is part of a binary system (where two stars orbit around one another) then its gravitational pull is so large that it may start to pull material off its companion star. ​Adding more mass to the White Dwarf in this way may cause it to become a neutron star or cause a supernova explosion.

If it only pulls off a small amount of matter from the companion star, a smaller explosion called a "nova" may occur. This process can be repeated several times caused a small cosmic fireworks display.

But, if you have two White Dwarfs in a binary system then they may merge together and, again, cause a supernova explosion.

The first exoplanet to be discovered is believed to have been orbiting around a White Dwarf waaaaaay back in 1917. While White Dwarf orbiting exoplanets are highly unlikely to support life, they do provide us with a wealth of information on how to analyse potentially life-harbouring exoplanets.

White Dwarf is also a rather good magazine from British games manufacturer Games Workshop.

And here are five fascinating facts about White Dwarfs and a jolly good video about them:
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