An Unexpected Guest

The year 1054 was quite a year!

Something exploded! Except of course, it didn't! Well not actually then anyway. Who saw it? the Chinese, the Koreans, The Arabians, and the Japanese to name but a few.

A new star suddenly and dramatically appeared in the night sky that hadn't been there before. Then gradually it faded. So, they recorded it as 'a guest star'. What a lovely welcoming name for an unexpected visitor.

In the night sky today is the remnant of an exploding star called a supernova. IAn amateur astronomer, John Bevis discovered it in 1731. This photo on the right taken by the Hubble Space Telescope, is how it appears to us now.

A team of astronomers have researched in meticulous detail the likelihood of what we see today being the remnant of the explosion or 'guest star' that was witnessed in 1054. There is an extremely close match in ages, position, velocities of the filaments of gas speeding away from and towards us with the time of the new star seen in 1054. The research paper is in the following link and the pdf can be downloaded for free for those of you who like to know the detail. https://arxiv.org/abs/0801.0893

When exactly did this star explode? Well, it takes the light from the remnant called the Crab Nebular also Messier 1 (M1) , around 6500 years to reach us, so take that number from 1054 and you get... 5446 BC. It makes for interesting reading to find out what was happening on Earth around then.

In the centre of this remnant is a pulsar, also known as a neutron star. This is about the size of whatever town you happen to live in (much smaller than a city) and yet contains as much actual matter as our own star the Sun. It is rotating on its axis about 30 times every single second and emitting vasts amount of radiation. You can read more about the Crab Nebula in this link, https://www.nasa.gov/multimedia/imagegallery/image_feature_1604.html

Something to ponder: what does it actually look like now, the image given above is what we see after about 6500 years of its light speeding across the Galaxy to the HST - our great camera in the sky, yet, we actually have no idea other than what can be mathematically modelled as to how it looks now.
Enjoy finding out more about this extraordinary nebula.

Image credit: https://www.nasa.gov/multimedia/imagegallery/image_feature_1604.html

Cool Blue Planet

On August 25th, 1989 the 8th planet of our Solar System was visited for the first and only time so far by any spacecraft from Earth. At this time, Alan Stern, now Principle Investigator of the New Horizons mission, was a graduate student at the University of Colorado, Boulder. 

Voyager 2, passed by Neptune, on its way to Interstellar Space. 

Nearly five days before its closest encounter it captured this image (left). At this point Voyager was 4.4 million miles away from Neptune. It was the final time Voyager's narrow angle camera was able to take a photo of the whole planet on approach before the planet became too large to fit in the frame. 

Photos of Neptune showing the height of clouds above the rest of the 'normal' atmosphere, revealed them to be about 30 miles higher and more in some places. The typical width of each raised cloud in this photo (right) is around 24 miles across with the exception of the wide stretch of cloud at around 124 miles wide.
                                                              

Neptune is six times further out from the Sun than Jupiter. That's just over thirty times as far from the Sun as we are.

There is a great deal we do not know about this planet. It is about seventeen times more massive than Earth yet nearly sixty Earths could fit into Neptune. There may or may not be a solid central core.
Neptune is the first outer planet not to be visible with the naked eye. A telescope or binoculars are necessary.

It has thirteen known moons, the largest of which is Triton which is just a little smaller than our own Moon. Voyager 2 discovered active geysers on Triton. A moon this far out, and still found to be active was not expected. In fact very little of what was discovered as Voyager 2 flew past Neptune and Triton was expected.

Even in the world of Astronomy, the old rivalry between Britain and France continues to this day over who discovered Neptune first.

After Herschel discovered the planet Uranus, or, as he himself named it, George's planet after King George (which I personally favour over Uranus ha!) there were seen to be anomalies in the planet's orbit. John Couch Adams (British) and Urbain Le Verrier (French) both began to do the maths and  each calculated that there must be another planet even further out than Uranus.

Both predicted positions for this eighth possible planet but it was the Frenchman Le Verrier who finally managed to persuade Germans Heinrich Louis d'Arrest (student of Galle) and Johann Gottfried Galle at the Berlin Observatory to take a series of observations where he predicted it should be. Galle found it to within one degree of where Le Verrier predicted it. The year was 1846.

A verbal and written battle over who knew it was there first and who discovered it first was eventually declared a draw, and the International Astronomical Union gave credit to both  Le Verrier and Adams. However both countries still declare being the first!

Twenty five years later to the day, New Horizons spacecraft cross the orbit of Neptune on its way to Pluto. It was a long way from Neptune but took a snapshot of the lonely blue planet that only Voyager 2 has ever visited. When will we go back I wonder.

NASA's Pluto-bound New Horizons spacecraft captured this view of the giant planet Neptune and its large moon Triton on July 10, 2014, from a distance of about 2.45 billion miles (3.96 billion kilometres) - more than 26 times the distance between the Earth and sun.

Credits: NASA/Johns Hopkins University Applied Physics Laboratory

References used in this article
Images of Neptune credits NASA.
http://www.britannica.com/biography/Heinrich-Louis-dArrest
www.nasa.gov
http://sci.esa.int/solar-system/35654-neptune/

The Great Moon Hoax

It is a curious thing, that well-known people are usually famous for one particular thing, or for one area of research or notable life achievement. One man however, became famous for something that he did not discover, but was attributed to him, as a practical joke!

John Herschel had an unassuming beginning, born in Slough, England on 7th March 1792. His parents William and Mary rather more well-known for their pioneering work and especially for William's discovery of the planet which he called the Georgian Planet after king George. Later it was renamed Uranus by the Astronomical Community, the name we are all more familiar with. Both William and Mary were exceptional astronomers and I will write a blog on each in due course. What

John perhaps has been a little overshadowed by the fame of his parents, when in fact, he too was an most extraordinary scientist.

John grew up in the family home called Observatory House. William and Mary owned a 40 ft telescope, and William's sister Caroline played a full part in helping them make sense of their data from their observations. She also tutored the young John in physics, chemistry and  mathematicss. William and Caroline Herschel were also gifted musicians, and they made a small income from their music.

In 1829 John married Margaret Brodie Stewart, and four years later they set off for the Cape of Good Hope. John had gone a circuitous route away from and then back to the world of astronomy, and during his father's ailing health decided to carry on his father's work. By the age of 41 he was a well-known and extremely well respected astronomer and scientist. He wanted to go and make observations of stars which could not be seen from the northern hemisphere, so, with his family,he travelled to the Cape of Good Hope, arriving in the January of 1834. He was there for the next five years.

On Tuesday 25th August in 1835, the following headline appeared on the front page of the New York Sun;

GREAT ASTRONOMICAL DISCOVERIES
LATELY MADE
BY SIR JOHN HERSCHEL, L.L.D. F.R.S. &c.
At the Cape of Good Hope
[From Supplement to the Edinburgh Journal of Science]

At the end of the long article which followed the headline, came the declaration that Herschel had found life on the Moon! The article declared that Herschel had built an enormous telescope while in South Africa. This telescope was apparently 24 feet in diameter, weighing over 7 tons, and was able to project onto a screen or wall via a hydro-oxygen  microscope, images of the Moon and the plant life he had apparently discovered on it, objects as small as 18 inches across. The article also declared that he had seen man like creatures on the Moon, illustrated here:

Six articles were published in total in the New York Sun after first being advertised on 21st August.
No one ever actually admitted to being the author, but evidence pointed to journalist Richard Adams Locke, who was working for the Sun at the time. It has been suggested that the purpose for the series of articles was mainly satire (as well as increasing the sales of the New York Sun). The objects of Locke's satire were those who wrote articles proposing  life on the Moon and other planets in our Solar System  and beyond. It also seems that Locke wrote it thinking that readers would catch on immediately to it being satire, but they didn't. They thought it was real, or at least a great number of readers did. It took several weeks before it was known to be a hoax.

John Herschel was amused at first, but grew increasingly annoyed as so much of his time became taken up with questions about it. The Sun apparently never admitted it being a hoax.

An interesting note to add here is that Edgar Allen Poe had also written a Moon hoax article, in June of the same year. However it was not taken seriously because the satire and humour in it was so much more obvious than Locke's. Locke was Poe's editor at the time. Poe was not impressed!

John Herschel's name would have been a household name after this and hopefully this helped him to be recognised as the great astronomer that he was, albeit by means other than he would have wanted.

There is something else to ponder here though. The fact that Locke wrote something satirical aiming pointedly at those who thought and wrote about the possibility of life on the Moon and planets, shows us that the debate was raging even then. Yet it seems that it was acceptable, at least by the press, to poke fun at those who suggested that there is life elsewhere in the Cosmos.

Just this week, NASA have reported evidence for possible flowing liquid water on Mars. Immediately, this was in all the papers. Water of course, as far as we know, is necessary for any sort of life.

We could look back at the Great Moon Hoax and miss the point that it was satire, poking fun at the suggestion of life elsewhere. History has many lenses and the most powerful one is the current time, with all our prejudices, ideas, assumptions and theories. Let us tread carefully as we walk back through the ages and remember to use a variety of lenses lest we miss the point due to our short-sightedness.

To the edge

The recent success of New Horizons on reaching Pluto and sending back extraordinary images of the little planet or more correctly, dwarf planet, has given us a fresh focus on the edge of our Solar System. New Horizons was launched back in 2006 and has mostly been in hibernation as it made its long journey to the last traditional planet. Yet when this grand piano sized spacecraft finally sends its last signal home, after we hope, viewing a Kuiper Belt object in a year or so's time, it will still never catch up with two other spacecraft, launched back in the late 70s, the Voyager spacecraft. Both of these craft are currently over three times further from us than New Horizons is, having been travelling for around 38 years. A marathon mission making New Horizons look like a mere sprint in comparison.


On 25 August 2012, Voyager 1 said goodbye to our planetary system we know of as the Solar System and stepped out into interstellar space, the space between the stars. Voyager 2 is has either now followed or is in the process of doing so. It is a process to clarify where both these spacecraft are in relation to interstellar space.



The journey to the edge of the Solar System has been a long one.



Voyager 1 was launched on 5th September 1977. Think about that! That's a whole generation ago!



One interesting detail that is perhaps surprising to learn is that Voyager 2 was launched 16 days before Voyager 1, on the 20th August 1977.  Voyager 1 however was faster and took the more direct route and so reached Jupiter first.



The mission was to explore the outer Solar System and the gas giants (though as an earlier blog recorded - these really should be renamed the liquid giants) their magnetospheres, atmospheres, structures, geology and 48 of their moons. Quite a mission for two spacecraft each the size of a small office about 4 metres by 4 metres by 4 metres, though there are various antennae attached too which are about 10 - 13 metres long. Each vehicle is considerably larger than the Pioneer spacecraft, yet they are nevertheless pretty small vehicles to navigate the then still relatively unchartered Asteroid Belt and beyond.



Volumes could be written on the incredible technology that is in each of these little crafts; technology that has been built on the success of the Pioneer spacecraft. For example, if Voyager 1 were to be above your head as you are reading your newspaper, it could read the headlines from one km away. Even more strange to think about is that we're talking about technology that is now around 38 years old! Think of how far even our computers have changed over that time and that gives us an idea of what NASA's Voyager teams are having to work with in still continuing to communicate with these spacecraft. Some of the computers that I used 35 years ago are now in a museum in Glasgow!


One of the first discoveries as mentioned in the previous blog is the unexpected shock to find that one of Jupiter's moons, Io, is actively volcanic and one such volcano is throwing sulpher and related material about 300km up which is roughly 30 times higher than Everest! When this comes down it covers an area of about the size of France!  This of course has a lot to do with the fact that Io has a much weaker gravity than Earth so when it belches stuff out, it goes further. The fact that it is still active threw up as many questions as the volcanic material spewed out of Io's volcanoes.



The most memorable of the Voyager spacecraft moments though, was the pale blue dot photo. Voyager 1 turned around one last time to take a 'family photo' of all or as many of the planets in our Solar System as could fit into the camera view. On the 14th Feb 1990 it sent back (photo credit NASA) the following photo.

This one photo captured the imagination of the world. The photo turned 25 years old this year, but its truth will never grow old.


The Voyager Insterstellar Mission (VIM) is to explore the interstellar medium and the outer limits of the Sun's sphere of influence. VIM began when Voyager 1 was about 40 AU (40 times the Earth-Sun distance) and Voyager 2 was 31 AU from the Sun. They had both been travelling for 12 years.


The heliosphere, is what could be loosely described as the 'bubble' that the Solar System is in, which the solar wind creates. As the Sun and our whole Solar System moves through space, the front of the heliosphere is smaller than the rear. Voyager 1 was first to break through the heliosphere and the reason - or one of the reasons we know this is because of the

Sun's  solar wind meeting the interstellar medium causing the solar wind to slow down dramatically because of what is known as the interstellar wind (illustrated in the following diagram - credit NASA). This shows the approximate positions of both spacecraft when Voyager 1 had just left the heliosphere in December 2004, then 94 AU from the Sun. Voyager 2 broke through the heliosphere on 30th August 2007  at 84 AU from the Sun which has shown us that in fact the heliosphere is not a perfect sphere but is dented, or at least has one dent we now know of.


On the 25th August 2012, came the day when it is largely agreed Voyager 1 left the heliopause having travelled through the heliosheath to the interstellar medium, the space between the stars.


To have data sent back from interstellar space, is both stunning and remarkable. Both Voyager spacecraft will continue exploring and sending data back to Earth until possibly and hopefully around 2025 if nothing untoward happens to either of them along the way. Then, after their last signals 'home' they will continue to travel towards the stars, Voyager 1 passing the first one in about 40,000 years from now though passing at around 1.6 light years away from it, and Voyager 2 bound for the star Sirius, reaching it in about 296,000 years time (and that's even with the spacecraft travelling at around 40,000 mph!)


When, by 2025, the spacecraft will not have enough power left to operate any of its instruments or send signals back home, it will have been nearly 50 years since their launch! If they do continue to be in communication with Earth for this long, it will be with the children and grandchildren of the generation of those who engineered and steered its launch and first three year mission all those years ago. That's quite a thought isn't it!


Follow their progress with this http://voyager.jpl.nasa.gov/where/index.html link,
and on twitter using @NASAVoyager

Io - Land of ice and fire

On January 7th 1610 Galileo Galilei gazed through his newly improved telescope and observed what he thought were three stars next to Jupiter. He thought they were really quite strange though because they were all lined up in a straight line around the great planet. He commented on this in his journal. The next night he looked again. He wrote down his astonishment that they were in different positions, and again around Jupiter. By 13th January, he wrote in his journal that they must be not stars, but little planets moving around Jupiter itself and following the giant planet as it travelled through the heavens.

The very first of these moons he named Jupiter 1, and went on to name them after Cosimo II, the son of Ferdinand and Christina (Ferdinand became Grand Duke of Tuscany in 1587), but as were the other three he discovered renamed in the mid 1800s, this, the first, was renamed Io. The other 3 moons which Galileo discovered are Europa, Ganymede and Callisto after the lovers of Zeus. 

An astronomer called Simon Marius also independently discovered these same moons of Jupiter, and did so apparently just over one month before Galileo did. However he did not publish his observations as quickly as Galileo did, and so it was Galileo who was given the credit for the discovery. Marius had the last word though because he chose the names which Kepler had suggested in 1614 and these were the finally accepted ones. Perhaps a future spacecraft will be called Marius!

The discovery of these 4 moons of course was one of the great discoveries that provided the evidence for the heliocentric theory (the Earth orbiting the Sun) which later landed Galileo in a tricky situation, but that's an interesting story in itself and not quite as it is often told, another blog perhaps.

There was another Galileo, one that was launched on Friday 13th October 1989. It spent 14 years in space. it reached Jupiter in 1995 and spent the next 8 years in orbit around Jupiter. The story of  this Galileo is amazing in itself. The NASA historian has written the following book which is free to 

download, http://history.nasa.gov/sp4321.pdf 

Galileo spent those 8 years in orbit around Jupiter studying Jupiter and its moons and especially the 4 Galilean moons. 

The Voyager missions had already discovered that Io is actively volcanic, but Galileo sent us the close - ups.

Voyager went to find the story and Galileo stunned the world!

Io is one hundred times more actively volcanic than Earth. 

It has mountains that are higher than Everest.

Its average surface temperature is around minus 130 degrees C

The temperature of its volcanoes can be around 1650 degrees C

It truly is ice and fire.

The above photo was taken by Galileo (credit NASA) in 1997.  

The plume you can see on the left rim is 86 miles high!

The inset bottom right is of the shadow of the airborne plume just to the left of the terminator line (separating light and dark areas of Io). You can see the volcano structure in the inset. This plume is on every Voyager photo from 1979 and is thought was active for at least 18 years up to the day this photo was taken! The volcano has been named 'Prometheus'. 

Io is five times the distance of Earth to the Sun, how is possible for anything on it to reach those temperatures? 

Well, it is about the same distance from Jupiter as our Moon is from us. Next time you look at the Moon imagine you are looking at Io, it's a little big bigger than our Moon. The difference, is that Jupiter is a giant!

Earth's gravity allows our Moon to orbit Earth about every 27.2 days. For Io to keep a quarter of a million miles away from its parent planet it has to whizz around Jupiter in just under 2 days. (1.77 days) Bear in mind that the distance it travels around its orbit is about 12 times the distance our Moon travels around Earth! The gravitational forces are huge on Io, it is pulled this way and that like a rope in a tug of war being pulled by Jupiter on one side and the moons Europa, Callisto and Ganymede on the other (Ganymede is the largest moon in the entire Solar System).

This continuous pulling on Io causes friction within, and causes it to heat up. In the same the way, continuously bending a wire this way and that causes it to grow hot. This is the cause of the intense geological activity on Io, with over 400 active volcanoes with plumes that can reach 300 miles above its surface.

Here's a question: Is what we have discovered in the moons of Jupiter and the moons of the other outer planets, something like a micro 'Solar System' within a Solar System? Jupiter has its own heat source, it gives out more heat than it receives from the Sun. It is orbited by some extraordinary moons, a growing number of which are thought to have subsurface oceans. Does the definition of planet need to be stretched to include moons around the giant planets. The next generation of exploration will, I think, prove that we need to look again at what we mean by the word planet!

One thing to ponder, the yellow moon Io is largely yellow due to all the sulphuric gases erupting from its volcanoes. It is often affectionately referred to as the 'Pizza Moon' or even 'Pizza Planet', but the similarity with a pizza ends with the name.

It actually smells like rotten eggs!

A peculiar fact  

It's a peculiar fact that if a particular building had not collapsed on 21st July 1801, we may not know as much as we do today about the chemical composition of stars. It all began with glass, and a small boy whose father was a glass maker. The boy's name was Joseph Von Fraunhofer, and and he worked with his father after only a very limited school education. His father was very poor.

Glass making was a skilled but not profitable business, and education cost money. When Joseph was  ten years old he began to work with his father.

When he was about 14 years old, and his father had sadly died, he was badly treated by a company he worked for and it was during this time that the building he had found for a roof over his head actually collapsed when he was in it. A compensatory gift of money enabled him to escape his life of poverty and work eventually for a much better and reputable company for whom he made lenses of the most excellent quality.

All lenses act to lesser and greater degrees like prisms. Sir Isaac Newton had in 1666, just over a hundred years prior to Joseph's birth, discovered that prisms split light into the colours of a rainbow. Astronomers found lenses which acted like prisms to be a great nuisance as it distorted the clarity of the image. Joseph devised a way to reduce this nuisance.

Joseph placed each lens between himself and a candle to check and measure the prism effect of each lens he made.

Except one day he didn't.

He used the Sun instead.

What he saw, is how we know what a star is made of. Joseph didn't know that at the time. In fact he never knew this. He died before anyone knew this. Yet his work paved the way to one of the most outstanding discoveries. What did he see? He saw a series of dark lines.

This was Joseph  Fraunhofer's original drawing of what he saw when he placed one of his lenses in between him and the Sun for the first time (Credit NASA).

A series of dark lines appeared to be imposed on the continuous spectrum of colours. The famous German stamp that showed Fraunhofer's orginal
drawing is shown on the right. (credit NASA)

Fraunhofer managed to resolve 574 of these lines which appeared in the spectrum of the Sun. The question was, what were they? 

This was one jigsaw puzzle that would take another 30 to 40 years to complete.

Here are some of the pieces that young Fraunhofer now in his early 20s discovered;
(remember he never looked directly AT the Sun because to do so is dangerous and would cause instant blindness for life)

1) When viewing the light from the Moon and planets, he found the same pattern of dark lines as he found when viewing the Sun.

2) When viewing the light from the star Sirius he found there was a different pattern of dark lines.

3) When heating up certain gases and viewing light through these gases when the gas reached a certain temperature, a dark line pattern appeared similar to some of the dark line patterns he observed in the Sun's and Sirius's spectrum.

Fraunhofer worked out an estimate of the wavelengths at which all these dark lines appeared in the spectrum of the Sun. He didn't know what they were, or what caused them, but he determined to observe in as much detail as he possibly could.

38 years later, in 1859,  Gustaf Kirchhoff realised the extraordinary truth: that these dark lines were what we now know of as 'absorption lines' The light of the Sun has to pass through the 'atmosphere' of the Sun and as it passes through the gases which make up the atmosphere, some of the light is absorbed by these gases. Each gas absorbs light at very specific wavelengths. So each gas can be identified by its position in the spectrum.

The light emitted is emitted from the photosphere part of the Sun through the rest of the photosphere and then through the chromosphere. These are parts of the Sun which could loosely be called the surface of the Sun, but in fact it isn't really a surface at all, but more a continual plasma of gaseous material which light is emitted from and passes through.

The elements identified in the photosphere and chromosphere are thought (by a complex series of physics equations) to be pretty similar to the make up of the rest of the Sun except for the core (that's for another blog).

(A note on wavelengths; the longer wavelengths of light correspond to the red end of the spectrum. The shorter wavelengths of light correspond to the bluer end of the spectrum.)

This truth was mind blowing, as mind blowing as the realisation 300 years previously, that the Earth went around the Sun.

This astonishing truth as to the cause of absorption lines opened the door for a whole new scientific study, the physics of the stars, which we now know as Astrophysics. This meant that for every star a spectrum could be produced which would tell us exactly what elements are in the star.

Helium
In 1870 a man called Lockyer found an absorbtion line that he could not identify with any known element on Earth. So he concluded that it was an element and a gas that was only found in the Sun's composition. He named it Helium, (Helios was the Greek for Sun, hence the heliocentric theory) 50 years later the same element was discovered on Earth.

Doppler effect
Not only was this a revolutionary discovery, but there was more to come to astound. Astronomers noticed that when viewing the spectrum of the edge or limbs of the Sun the spectrum lines were shifted along either to the left of right of their original positions when viewing the centre of the Sun.

Realisation dawned that what was happening was the same thing that happened to sound waves when a vehicle passes by; the wave is shortened when it is coming towards you and stretched when going away from you. The same is true of light waves, and what the shift in absorption lines meant was that the one limb of the Sun was travelling away and the other towards the observer. This meant that the rotation of the Sun could be measured. Another whole new vista had opened to astronomers.

Radial velocities
In the early 1900s Edwin Hubble studied the spectra of distance galaxies as part of the ongoing debate as to what galaxies were. He noticed that some of them had huge (compared with the Sun's shifted spectra) shifts of their spectra, which he called redshifts because the shifts were towards the red part of the spectrum. He suggested that the interpretation was that these galaxies were speeding away from us at enormous speeds and some as large as one tenth the speed of light.

The day the building collapsed started a chain reaction of discovery leading to,

1. Each absorption line corresponded with specific elements
2. The ability to be able to identify what the Sun's composition was.
3. A new element helium being discovered first in the Sun.
4. To be able to determine the rotation speed of the Sun.
5. To be able to determine the rotation speeds of nearby galaxies and the speed at which distant galaxies were travelling away from us, and therefor the distance of them.
6. The main elements in the composition of galaxies
7. That our Galaxy is an island universe and that there are at least 100 billion other galaxies each with an avarage of between 100 - 300 billion stars.

Joseph Fraunhofer did not live long enough to know all these consequences of his work, yet he took the skill that was in his hand and worked as hard as he could, producing such accurate results that others could build on and work with.

A young lad, with such unassuming beginnings as he had, in poverty with virtually no official education eventually led to tremendous discoveries which began with his very specific glass making skills, an unstable old building, and his decision one day to use the Sun instead of a candle to produce a spectrum.
















http://www.astronomygcse.co.uk/AstroGCSE/Unit2/Fraunhofer.htm

http://www.madehow.com/inventorbios/43/Joseph-von-Fraunhofer.html

Space, the final frontier

March 3rd 1972 was a day that passed by like any other for most people. yet it was a day that changed space exploration forever, altered our world view and shaped all future space missions more than any other day in history has so far ever done.


It was though, a day that was overshadowed by the Apollo missions, because Apollo 15 (launched 26th July 1971) was the first mission to take a lunar rover to the Moon with them, and the glow of that outstanding achievement outshone all others especially with Apollo 16 being eagerly anticipated and gearing up for launch on 16th April 1972. Not surprising then that the associated media overlooked the plucky little Pioneer 10 craft, whose launch date was nestled quietly and inconspicuously between those two missions just 6 weeks before Apollo 16 was due to launch.


That day, on the 3rd March, something the size of an old fashioned widescreen tv (well if you count all the booms and antennae the length would be about the length of a family sized car) was launched from Cape Canaveral on an Atlas-Centaur vehicle. It reached a speed of more than 30,000mph pretty soon after launch. This was the fastest speed that any spacecraft had ever attained.


11 hours later it reached the Moon.


12 weeks later it flew past Mars.


3 months later it reached the Asteroid Belt and began it's journey through the most populated with rocks place in the entire Solar System. Yet just to put that in perspective, over populated with its fair share of rocks it may be but the course that NASA had given the little Pioneer was to get no closer than five and a half million miles to one of those rocky bodies to ensure its safety as it passed through.


Pioneer 10 was the very first spacecraft to fly through the Asteroid Belt and through this 'gate to the outer planets'. It was the fastest vehicle that had at that time ever been made and it was speeding up. It was speeding up because the planet it was first heading for was giving it a huge gravitational welcome like no other planet in our Solar System can. Jupiter, its first destination after the Asteroid Belt, was pulling it in until little Pioneer was flying at around 80,000 mph.


It finally reached Jupiter or, as is more technically described, reached its closest approach on the 4th December 1973. Travelling at around just over 81,000 mph it passed by Jupiter around 81,000 miles above the top layer of clouds. Here is the first series of photos taken from Pioneer as it approached Jupiter. It actually began taking photos of Jupiter from the 6th November 1973, the first ever taken from so far out in space.

As it travelled 'behind' Jupiter, the planet became a crescent which gradually faded away back into the inky backcloth of sky as Pioneer left it behind forever.


In amongst all the many and varied sets of data Pioneer sent back to Earth was something extremely surprising. Even more surprising is that the vast majority of people still don't know.


Pioneer told us, that all the evidence from studying its magnetosphere leads to one conclusion, that Jupiter is not so much a gas giant, as a liquid giant! This was a totally unexpected and extraordinary discovery. Even more shocking is that this liquid is a type of liquid that does not exist on Earth, and we have no idea what it might look like! Astronomers are still getting their heads around that one! Perhaps that's why they are still referred to as the gas giants and not the liquid giants.


Pioneer achieved many firsts, first to go as fast as it did, first to pass through the Asteroid Belt, first to reach Jupiter, first to detect atoms of helium in the space between the planets, first to detect sodium and aluminium ions in the solar wind, first to confirm a long held theory that Jupiter had a heat source that was and is causing the great planet to emit more heat than it receives from the Sun, first to pass and travel further than the orbits of all the planets in our Solar System, and there were many more firsts which you can read up about on the NASA website, http://www.nasa.gov/centers/ames/missions/archive/pioneer.html


It  passed Jupiter, after taking hundreds of photos, and then went on to pass by the orbits of Saturn, Uranus, Neptune and Pluto (at that time still regarded as a planet) and became the first human made machine to head out into the great outdoors of the Solar System and reach for the Interstellar medium. Pioneer 10's mission officially came to a close on the 31st March 1997,  but NASA followed its progress for another 6 years as part of researching the technology for communicating with spacecraft and probes at great distances in preparation for future missions.


On 23rd January 2003, Pioneer metaphorically waved goodbye to us as NASA received its final detectable signal. We may not hear from it any more, but as far as we know it continues on it's way towards the Interstellar medium and then on towards the star Aldebaran, the eye of Taurus the Bull. It should only take a couple of million years or so to get there.


One more thing, when it does reach the Aldebaranians they'll know we sent it because bolted on to the Pioneer 10 (and 11)'s small frame is a small gold-coloured plaque with a nice picture of a man and a woman and of course a map of how to get to Earth in case, I imagine, they fancy a nice cuppa and a sandwich one day if they happen to be passing.