King and Queen

King and Queen 1952-3, cast 1957 Henry Moore OM, CH 1898-1986 Presented by the Friends of the Tate Gallery with funds provided by Associated Rediffusion Ltd 1959

Moore, King and Queen (1957). Bronze, 1640 x 1390 x 910 mm. Tate Britain, London

Who they really are

This sculpture depicts two figures (male and female) seated on a bench and focuses on the ancient conception of monarchy with divine blessing!

It combines naturalistic elements with abstract and blends the human celestial with kingship, reflecting the image of stable and benevolent authority that resonated widely in the post-war climate of uncertainty.

Rubens, The Adoration of the Magi, 1616-17. Oil on canvas, 251 x 338 cm. Musee des Beaux-Arts, Lyon
Why Counter-Reformation artist, Peter Paul Rubens painted The Adoration of the Magi more often than any other part of the life of Christ


Adoration of the Magi is the name traditionally given to the Christian subject of the “Nativity of Jesus” in art. The three Magi are represented as kings (or wise men) and have found Jesus by following a star bringing gifts of gold, frankincense and myrrh; this is commemorated as the ‘Feast of the Epiphany’ every year – the last day of Christmas.

Christian art has based many depictions of the birth of Jesus Christ celebrated at Christmas, from the narratives in the Bible. This story has been portrayed in many different forms, such as: murals, panel paintings, stained glass windows, oil paintings, manuscript illuminations, ivory miniatures, carved stone, sarcophagi, architectural features, free standing sculptures and of course altarpieces. Altarpieces are interesting because the figures almost come alive, combining both painted and sculptural elements of this popular and eternal Christian theme.

Rich textiles and exotic turbans can be seen as the eye wanders across the canvas packed with full-length figures. This dim stable is lit up by shafts of light, and no image permeates Christian art quite like Madonna and child with such frequency, that Rubens has provided arguably the best version still in existence.

Flemish Baroque painter, Sir Peter Paul Rubens, was a proponent of an extravagant style. He emphasized movement, color and sensuality which is quite evident in this wonderful artwork.

Rubens worked as a diplomat, thus being knighted in both Spain and England also receiving an honorary master’s degree from Cambridge University in 1629.

Antwerp City Hall required a large version of the Adoration of the Magi which was a painting that made its way to the King of Spain in 1628 with alterations.

This artist refashioned much of the picture before moving it on: for example, he incorporated a self-portrait.

The Antwerp version is different, hence the Magi is offering the infant Christ some gold coins and the brush used has been heavily charged with pigment: the highlights around the eye and hair for instance!

Rubens uses both other end of the brush to make his marks in the still wet paint and this reinforces the nature of the curls, almost giving them more movement!

Prado’s permanent collection houses the Antwerp Adoration today, where the chief curator and conservation department are investigating the changes Rubens made for its journey to Iberia, by using new analysis and archived documentation – histiographically – to discover the original intentions of Sir Peter Paul and his use of iconography, from the original commission.

A Bigger Splash


Hockney, A Bigger Splash (1967). 242.5 x 243.9 cm. Tate Britain, London

Where this picture was painted

A Bigger Splash is a large pop-art painting by British artist David Hockney.

This picture was painted when Hockney was teaching at Berkeley and the movie with the same name shortly followed! It depicts a swimming-pool beside a modern bungalow, disturbed by a large splash of water due to an unseen person who has apparently jumped in from a yellow diving board.

Showing a warm / sunny California day, with a cloudless blue sky, there are two palm trees in the background and a flat roofed building with large glass windows; there is a movie director’s chair on the patio. The shadow directly under the chair means the Sun is high up around noon.

Someone has just dived in and the water has fountained up into the air but the diver is still beneath the surface and the directors chair follows the same diagonal line. The outer calmness contrasts with the huge – central – splash in the water, thus it took two weeks to paint something that would have lasted two seconds!

Johannes Vermeer, The Concert (1664). Oil on canvas, 69 x 63 cm. Isabella Museum, Boston
What the enigma about this painting really is

Neutron Stars


When pulsars appear 

Like white dwarfs, neutron stars don’t have any internal source of energy and so they are relentlessly cooling. These temperatures imply that most of the energy will be radiating away as X-rays.

Another extreme property of neutron stars is the rate at which they rotate. Typically they complete several full rotations every second a bit like a skater spinning as they pull their arms in the rate at which they spin increases. Exactly the same phenomenon takes place during the collapse, which leads to the formation of neutron stars. The comparatively slow rotation of the star rapidly increases as the star contracts.

At both X-ray and radio wavelengths the emission from neutron stars arises from hot spots on its surface.

This makes it possible to measure the rotation rate of neutron stars directly. Every time an X-ray region of a neutron star rotates in our line of sight, astronomers see a bright flash at X- ray or radio wavelengths.

The result is a regular series of pulses that make it possible to measure their rotation rates. They also give neutron stars their alternative names: pulsars.

Like the skater spinning more rapidly when they bring arms and legs into their body the same physical effect takes places as when a pulsar is born.

This is an artists impression of a pulsar.

……             …….       …….


In reality the doughnut shaped view is a cutaway. Gas would extend further, the way we see radio pulses from pulsars.

To understand pulsing of a pulsar, all you need is a pair of scissors with bluetak.

You can only see the radio beam when it is directed towards you, so in effect you observe a series of short flashes as the pulsar rotates.

Above the Chandrasekhar limit, the force of gravity overwhelms electron degeneracy pressure in white dwarfs.

Its similarly an upper limit of the mass of neutron stars above which neutron degeneracy pressure is unable to support them.

It is not yet understood how material at such extremely high densities behaves. There are no current experiments that can produce such extreme conditions.

It is strongly suspected that neutron stars can’t be more massive and the the real limit is probably somewhere between 2 and 3 times the mass of the Sun.

Some scientists turn the problem round and use the mass of neutron stars as a way of improving understanding of dense matter.

Neutron star masses can be measured in binary systems in the same way as stars powered by nuclear fusion; and, white dwarfs are measured by the faster they orbit around one another, the more massive they are.

Black holes suppose the force of gravity causes gas to fall on to the neutron star pushing it over the limit. Once the force of gravity overwhelms the ability of neutron degeneracy pressure to support it, neutron star is another similar force that will act to support it and prevent further collapse.

There is no further physical force that can prevent the further final collapse of the neutron star under its own mass.

There seems to be nothing to stop it shrinking to zero size and infinite density. What happens then is somewhat uncertain because all current theories break down to the point of the most extreme densities.

This requires a combination of Einstein’s theory of gravity general relativity, and the theory that governs the behavior of the universe on very small scales.

Quantum mechanics so far no one has been able to make a working version of such a theory. There is one thing all the current theories are clear on and that is the collapse continues and the core will become so dense that the escape velocity from the surface will exceed the speed of light.

The speed of light appears to be the ultimate speed limit of the Universe so that means nothing, not even light can escape the gravitational pull of the core.

At this point, a black hole will have formed. The distance from the center at which the escape velocity is the speed of light is called the event horizon, and its size depends on the mass of the collapsing core.

Once an object crosses the event horizon, it is forever trapped within the black hole. The event horizon doesn’t describe a solid surface anymore than the horizon you see from a ship is a solid line.

An unlucky astronaut could pass over the event horizon of a sufficiently massive black hole without noticing any ill effects and yet be trapped inside forever by the gravitational field of the black hole.

How can anyone find black holes if no light can escape from them? Because they have a detectable influence on nearby objects.

For example, in a binary system where normal stars orbit around a black hole the intense gravitational field tears material from the surface of the star which then falls into the black hole.

Gravitational potential energy is then converted to heat energy at very high temperatures. This occurs outside the event horizon so this energy can be radiated away as X-rays even though the material subsequently falls inside the black hole.

The way to find binary star systems containing black holes is to identify very bright X-ray sources.

Astronomers then measure the motion of the normal star as it is thrown around its orbit by the invisible black hole to determine its mass. Neutron stars cannot be more massive than 5 M so if the invisible companions is more massive it must be a black hole.

In the very center of our galaxy is a black hole. Astronomers have noticed stars orbiting a central object with no luminous object to be found there. It is very small and massive because the stars move very quickly around it.

Because it is so dense it has to rely be a black hole. How black holes are produced in the first place is when enough material falls into a neutron star or is accredited from a companion star it could exceed the maximum mass for a neutron star, so it would then collapse to form a black hole.

It is also possible for very massive single stars to form a black hole. If the star is massive enough the supernova explosion that forms the neutron star might not be able to release enough energy to eject all the outer layers of he star.

The materials will then fall back on to the newly born neutron star causing it to collapse to form black hole. Supernova explosions are not yet well understood, so it isn’t possible to give a hard and fast value for the mass of a star above which this would occur, but the best estimate at the moment is that a star above 25 times the mass of the Sun will form black holes via this route.

Alternatively the mass of the supernova could be so high it may collapse directly to form a black hole without forming a neutron star.

Robotic telescopes might soon be able to identify extremely massive stars with hundreds of times the mass of the sun, and identify vanishing massive stars.

The cosmic cycle and the next generation of stars is this evolutionary process and nuclear fusion plays its part in powering stars and creating new heavy elements nucleosynthesis.

These elements are returned to the interstellar environments when the stars die, known as the interstellar medium!

The origin and composition of the interstellar medium has an abundance of hydrogen. Formed primordial nucleosynthesis in the early universe.

The remaining elements are all products of nuclear fusion reaching within stars and supernovae. These elements come recycled and incorporated into the next generation of star and this is the cosmic cycle. Outer space is not a pure vacuum. The dark lines on images of the antennae galaxies show some of the contents of the interstellar medium.

The dark lanes are regions obscured by dust which is composed of carbon rich molecules and tiny mineral rich grains.

The interstellar medium has a surprisingly wide range of temperatures and densities. Gas isolated materiel is of a lower temperature than that near massive stars. Regions of the interstellar medium contain both gas and dust of comparatively low temperatures.

Dust will melt and vaporize at certain temperatures. The temperature is much cooler at the dense closure where dust and gas form. These regions are known as giant molecular cloud comps GMCs.

They are large and massive. They contain so much dust that they can completely absorb all the optical light from stars behind them.

The presence of young star near GMCs strongly suggest that they are involved in the star formation. But how are massive clouds converted into stars?

Three key ingredients seem to be needed for star formation to occur. Firstly the GMC is highly structured with lots of clumps and filaments having much higher densities than other regions of the cloud. These are the locations where star formation will occur.

The second ingredient is gravity, which will cause the clump’s to collapse in on themselves. These clumps are initially supported by their thermal energy in exactly the same way the stars are supported against gravity.

The ingredient is something to disturb this equilibrium and trigger a collapse. The trigger is an external event that compresses the clump so that gravity can take over and cause them to begin their contraction.

This can be something like a nearby supernovae where the shockwave from the explosion hits the GMC or perhaps the collision of two GmCs. Once a clump within a GMC is sufficiently dense it will start to contract under its own gravity.

As it contracts the conversion of gravitational potential energy to heat energy causes the temperature of the molecule clump to rise again in exactly the same way as the core temperature of a star rises as it contracts.

Constellation Carina. Right hand panel shows the region at optical wavelengths where the cold dust absorbs background light causing the dark V shaped absorption feature across the bright nebula.

At infrared wavelengths the thermal emission formed is cold dust and can be detected. The infrared image shows the true extent of the GMC. There is bright infrared emission from cold material that corresponds to the dark V shaped lane in the optical.

The bright materials picture of dense molecular cloud is called a black globule.

The density of dust and gas is sufficiently high that it absorbs light from stars located behind it. Visible in the optical image is gas being heated by newly born stars outside the GMC.

Giant molecular clouds compared and associated with vigorous recent star formation in the constellation. Carin at an infrared at b and optical wavelengths.

Note the dark V shaped lane in the optical due to cold dusty material is observed to strongly emit infrared IR radiated due to form the massive stars embedded within.

The contraction of the clump is expected to be remarkably rapid. Computer simulation of this process suggests that after only a few thousand years the surface temperature of the contraction clump or protostra will have risen to 3000K.

This is beautifully illustrated by the observation of a small region of the Carina GMC where a hot young protostar is clearly picked out by the light it is radiating at infrared wavelengths.

In addition to heating up as they collapse the cloud clumps also begin to spin more rapidly. This happens for exactly the same physical reason that was seen in the formation of neutron stars.

As they spin more rapidly they change their shape becoming flatter and more disc like.

Material falling onto the central protostar now passes through a flattened region surrounding it, called accretion disc.

At the same time as material is falling onto the equatorial regions of the protostars, powerful jets of material are ejected from the poles of the star.

This simultaneous in fall and outflow geometry is shown schematically and observations of this are shown.

Astronomers are currently unsure of the detailed process that launches these jets but either effect is to remove the material and energy from the protostar.

Eventually the core of the protostar will become so hot that nuclear fusion reactions can begin and a new star is born. The whole process is surprisingly rapid and is thought to be complete within 10 years of the weakest mass stars.

More massive protostars have greater gravitational pull so material is pulled onto them at a much higher rate which makes more massive stars form more quickly.

Stars of about  15M form in 105 years. In any circumstances the pre main sequence phase of a star is expected to be much shorter than its lifetime on the main sequence.

A close up of a region of the Carin GMC.

In the optical image we can see the opaque molecular cloud, while in the near image we can clearly see the protostar which is in the process of formation.

Note the bright linear jets of material associated with protostars. Astronomers are increasingly confident of this picture of star formation for stars of mass comparable to the Sun.

By contrast, the formation of very massive stars is still not fully understood. Stars like these are found in clusters such as the Arches in the center of our Galaxy.

The formation is quick and the stars are rare both of which make the observations difficult.

Also, the GMCs they form in are expected to be so dense that little light can escape from them during their formations.

Perhaps they form in essentially the same way as lower mass stars.

But there is an alternative theory for stellar cannibalism.

In this theory smaller protostars collide and merge to rapidly build up a massive protostar.

This merger process would become more and more efficient as the central mass and gravitational pull increase with every merger.

Schematic representations of a protostar surrounded by an accretion disc which supplies in-falling gas on its equatorial regions.

Also shown are the out-flowing jets from the polar regions which remove both energy and a proportion of the in flowing material.

Sequential image of the protostellar object HH30 taken in 1995, 1998 and 2000, illustrating the features shown in the schematic finish.

The dense regions of the horizontal edge on the disc hide the protostars itself the light from which illuminates to the outer surfaces of the disc.

The motion of blobs of gas within the heretics can clearly be seen.

Stars of all masses are born live and die and are intimately connected: nuclear fusion creates new elements in stars which are subsequently returned to the interstellar medium as the stars die ready to be incorporated into the next generation of star formation.

This continuous cosmic cycle is shown schematically and is dramatically in evidence in the beautiful Hubble Space Telescope image of the young stellar cluster NGC 3603.

However, this is not quite the end of the story because the accretion discs around the protostars hide one final secret. Accretion discs are the sites where new planetary systems are born. The most massive stars in this region are already beginning to die.

The material ejected from the blue super giant in the upper left – product of nucleosyntheses to the cosmos – there is a black patch in the top left corner of the image. Young stars in the cluster are compressing the surface of the GMBC from which it was born, leading to a further burst of star formation and the bright head of the pillars within it.

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White Dwarfs


Why white dwarfs are less luminous than the Sun?

Again this process requires an input of energy so it deprives the star of the energy needed to support its own weight, and this helps accelerate the collapse.

The core density increases and so does the electron degeneracy pressure that resists the contraction; the negatively charged electrons and positively charged protons combine to form neutral neutrons.

This removes electron degeneracy pressure as the core collapse gains speed. Core collapse suddenly stops at a staggeringly light temperature.

Then a new form of pressure – neutron degeneracy pressure – comes into play. This works on exactly the same quantum principles as electron degeneracy pressure, except neutrons are the particles involved instead of electrons.

The pressure provided by the neutrons is enough to halt the collapse of the core, but the remaining outer layers of the stars are still falling inwards at the speed of light.

What happened next is uncertain. Even the most advanced computer simulation cannot accurately reproduce the process but the energy of the falling material is redirected outwards as the outer layer hits the core and rebounded expelling them in  titanic explosion called a supernova.

Supernova SN 1987A occurred in the nearby Large Magellan Cloud. The supernova is thought to be  a blue duper giant star roughly twenty times as massive as the Sun!

Whatever the cause of the explosion, the high temperatures present and an abundant supply of neutrons, allows the star to undergo one final round of nucleosynthesis. In only a few seconds, the neutrons are rapidly absorbed by nuclei in the outer layers of the stars.

This produces a wealth of new heavy elements including gold and plutonium.  These are called R-process reactions with ‘r’ standing for rapid. Stars have spent millions of years evolving to the point at which they have massive iron core, but the final death is over in a matter of seconds. So much energy is released in the final explosion, that the star brightens by a factor of about a hundred million.

For a while it might outshine the entire galaxy in which it is located. If one were located in our Galaxy it would be visible during the day for a few weeks.

The star has a final gift for the cosmos, the explosion returns all the elements that were formed within it by nucleosynthesis back into the galaxy, in to the interstellar gas, and dust locates between the stars.

The next generation of stars will then form from this material. Supernova are the most important source of element heavier than neon in the Universe. The iron found in our blood and in the molten core of the Earth is the direct result of the explosive death of massive stars.

The X-ray image of the Cassiopeia A supernova highlights the hot chemically enriched material returned to the Galaxy. The final remnants of stars are similar in the final life stage, as to the Sun, and different with stars much larger than the Sun.

They differ because of the different physical properties of their cores and the nuclear reactions that occur there.

However, they also share similarities in both cases they eject large quantities of material enriched with the products of stellar nucleosyntheseis back to the rest of the galaxy.

This process doesn’t last to the complete destruction of the star, because a dead remnant of the star is left behind.

The properties of such stellar corpses are interesting. White dwarfs are the remains of stars such as the Sun after the outer layers of the stars are ejected the hot stellar core is exposed.

This core is composed of the carbon and oxygen of previous episodes of nuclear burning. The last of the current energy source means that these stars are now entirely supported against gravity by electron degeneracy pressure.

New born white dwarfs are still very hot because nuclear reactions have only recently ceased. The surface temperature of the most extreme examples are 150 000 K, though most are considerably cooler.

It is thus surprising, that White Dwarfs are so faint. Their location on the HR diagram shows that they are typically less luminous than the sun.

The combination of high temperatures and low luminosity must mean they are physically rather small and it turns out they are typically about the same size as the Earth, actually.

Despite this they still contain a large amount of matter from the original stars. Measurement of the masses of white dwarfs indicate that they range right up to the size of the Sun.

They must therefore be extremely dense objects with average densities higher than that of the sun. The result of a search for white dwarf stars in the globular cluster M$ is located about a distance from the Sun and contains more than 10 stars.

The left hand panel shows the entire cluster as viewed from ground based telescopes. The areas seen by the Hubble are marked. The right hand image shows the 8 isolated white dwarf stars (circles) that were found.

The outer object present is the main sequence star and red giants. The fate of these objects is such that with no more sources of internal energy available to them they will gradually radiate their residual heat away into space cooling and becoming progressively dimmer as they do so.

White dwarfs have much smaller surface areas than other stars so it takes a long time for all the energy of such a star to be radiated. This would take about as long as the current age of the Universe.

The unavoidable fate of stars like the sun is that they will end their days as cold, dark spheres rich in carbon and oxygen, but lost to the cosmic cycle.

Neutron stars show that electron degeneracy pressure is overwhelmed by the force of gravity, and the stars collapse in upon itself again.

This boundary is called the Chandrasekhar Limit in honor of an Indian astronomer. His prediction supports, from a simple observational fact, that in almost a century we have yet to find a white dwarf with a mass over this value.

During the collapse, the electrons and protons combine to form neutrons. The collapse is only halted once the neutrons themselves are so close together, that neutron degeneracy pressure halts the contraction.

By this stage the stars have shrunk to a radius of only about 10km and it is made predominantly of neutrons, hence the name neutron star.

These mindbogglingly high densities are similar to those found at the center of atomic nuclei and are a factor of a hundred million times greater than those found in white dwarf stars.

A single thimble full of neutron star matter would have a mass of seven hundred million tons. These huge densities mean that neutron stars also have powerful gravitational fields. For any astronomical object it is possible to define an escape velocity.

This is the speed at which something must be moving away from it to completely escape the objects gravitational field. For neutron stars the escape velocity is 30 times the speed of light.

After the formation of the neutron star the surface temperature is more than 10K.

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Electron Degeneracy Pressure


What happens when pressure builds up?

Unlike the thermal gas pressure that has supported the stars so far, this force is a peculiar result of the quantum behavior of electrons.

It can be understood as the inability of identical particles – in this case electrons – to occupy the same space at the same time.

This leads to pressure when electrons are pressed too closely together – electron degeneracy pressure – and this force arises from the close proximity of electrons so it depends on density of the core rather than temperature but nevertheless supports the core against further gravitational collapse.

The carbon / oxygen core, will eventually be revealed as a white dwarf star.

In the main sequence life of massive stars, lower mass stars are up to 8 times the mass of the Sun; however, the life cycle of stars 100 times the mass are different.

How do they end their lives?

Well, lower mass stars run out of fuel in the core and the core contracts. The overlying materiel then falls in and heats up until nuclear reactions start in a shell around the core.

While this happens the core continues to contract and heat up until it reaches a point when it is hot enough to burn the nuclear ash off the preceding fusion reaction.

This then carries on until the supply of fuel of the new set of reactions is exhausted at which point the core contracts again until the region surrounding it can maintain fusion reactions.

The end result is a shell structure within the stars. With the increasing temperatures encountered as you move towards the core, it’s supporting the fusion of progressively more massive nuclei.

Fusion of more massive nuclei needs higher temperatures because they have a larger number of protons so they have a larger total positive charge.

This results in greater mutual electrical repulsion which the nuclei need to overcome in order to achieve nuclear fusion. They therefore need to be moving more quickly which means they need to have a higher temperature.

The core temperatures of massive stars are systematically higher than those of their less massive relatives. The cores of stars with high masses and high temperatures become carbon burning stars.

This fusion of two carbon nuclei to make one neon (with a helium nucleus created in the process) is important.

Once the carbon runs out the core contracts again raising its temperature until neon burning is possible. This fuses a neon nucleus with a helium nucleus to make magnesium.

After the neon fuel runs out a further bout of contraction raises the core temperature at which point oxygen burning creates silicon.

Finally, the process of core contraction is repeated and silicon burning begins at core temperatures creating sulfur and calcium.

This sequence of nuclear reactions continues and ultimately leads to the  production of a number of heaver elements in the so called iron group of elements such as iron, chromium, manganese, cobalt, and nickel.

This is where some of the elopements that make up the human body come from.

At the end of the sequence of nuclear reactions the star is like a cosmic union and has a predominately iron core at a huge temperature surrounded by concentric shells of silicon and sulfur and oxygen and carbon, helium and possibly an outer layer of hydrogen; each at a lower temperature than the shell within.

The effects these nuclear reactions have on the outwardly visible properties of such stars are the same in low mass stars.

The extra source of energy, causes the star to expand and then cool, altering the higher temperature, meaning it becomes typical hot blue super giant, before evolving to even greater sizes and cooler temperatures, passing through both yellow and red super-giant phases.

The largest known stars are the red super-giants. Thus, if one were placed in the center of the Solar System it would engulf Jupiter.

The evolutionary track of a high mass star across the HR diagram is interesting.

Unlike the Sun, astronomers are far less certain about he details of the post main sequence of the life of very massive stars.

The huge quantities of the energy they release can be almost enough to overcome gravity. This makes the star unstable and the effects of this instability are difficult to predict.

Broad thinking believes they are expected to be constantly ejecting large amounts of gas from their surfaces. This profoundly influences their evolution.

A famous example is one of the most massive stars known in our galaxy – Eta Carinae – that is believed to have been born with a mass well over a hundred times that of the Sun and is now more than four million times brighter than the Sun. In the nineteenth-century it underwent an explosive outburst and became even more luminous. In the process it formed a compact nebula around itself.

This nebula appears to have reformed in only 30 years yet the amount of gas it contains is at least 15 times that mass of the Sun. Eta Carinae is one of the most massive stars known and can be seen surrounded by material ejected in the nineteenth-century eruption. The physical cause of the event is still unknown.

We know that the post main sequence evolution of low mass and high mass stars is similar: when fuel runs out, the core contracts and heats up and this makes it possible for new nuclear reactions to burn new source of fuel.

For the stars similar to the Sun this ends with the slow ejection of the route layer to leave behind a hot but inert core made of carbon and oxygen.

However, the death of massive stars is much more rapid and violent. We have seen the nuclear process after the fusion of helium that supplies the energy to support a star against gravity. In other words the supply energy prevents such a star collapsing inward under its own weight.

But these reactions aren’t all equally efficient. Each successive chain of reactions involve progressively heavier elements: carbon, neon, oxygen, and silicon. Burning is less efficient at releasing energy than the preceding one!

This means that each reaction chain must consume more fuel per second than the previous one, to produce the same amount of energy to support the star against gravity.

This means that each phase of burning will be of shorter duration than the one before it.

For example, a star 25 times as massive as the Sun has the hydrogen burning phase lasting the longest; subsequently the carbon burning phase only lasts less; and the neon burning lasts even less and oxygen burning just 6 months.

Finally silicon burning takes only about 1 day until the star runs out of this fuel source.

The absence of an energy source means the core collapses under gravity with a resultant rise in temperature to the point at which iron nuclei can undergo nuclear fusion.

This is where things change. The fusion of iron to form heavier elements is different from that of lighter elements in one vital respect: rather than releasing energy, it absorbs it.

The effect of this is dramatic. Thus, nuclear fusion can no longer supply the energy, to support the stars against gravity.

The core continues to collapse in upon itself. Soon it reaches the densities at which electron degeneracy pressure, stops the contraction, in lower mass stars.

In more massive stars the force of gravity quickly overwhelms the resistance of electron degeneracy pressure. It is predicted that electron degeneracy pressure can only fully support cores of stars with masses bigger than that of the sun, but some stars have much more massive iron cores than this.

The collapsing core continues to rise in temperature until it reaches the point at which the iron nuclei begins to break apart into the constituent protons and neutrons.

Correggio is best-known for his lively, iconographical illusionism in some of the most inventive fresco cycles of Renaissance art history

Highly influenced by da Vinci, The Mystic Marriage of Saint Catherine is dated around 1520 and housed in the Louvre; thus, the soft, graceful effect conveyed by Catherine’s lips and hands reflect the Correggio original in Naples. The scene depicts Virgin Saints as they go through a wedding ceremony with Christ in the presence of his mother.

Placidus and his sister Flavia in Martyrdom of Four Saints have two Roman siblings behind them. Completed in 1524, Eutychius and Victorinus have already been beheaded, thus, an angel flies above them holding the martyrdom’s palm leaf.

Commissioned by the Duke of Mantua, Venus and Cupid with a Satyr was finished in approximately 1528. Correggio depicts Venus sleeping with her son, Eros, and there is a pipe player behind them who is caught while discovering this Roman goddess of love.

Correggio’s most epic piece, Assumption of the Virgin is a fresco that decorates the dome of Parma Cathedral. The dome base represents the four protector saints of Parma; St John the Baptist with a lamb, St Hilary with a yellow mantle, St Thomas with an angel carrying the martyrdom palm leaf and St Bernard, the sole figure looking upwards. The Virgin Mary in red and blue is lofted up by angels.

Inspired by Ovid’s “Metamorphoses” Jupiter and Io is among Correggio’s best work. Painted in the early 1530s, with such radiant, cool, colour Io is seduced by Jupiter who hides behind the dunes to avoid hurting the jealous Juno (his sister and wife).

Renaissance biographer Georgio Vasari said: “Great Mother Nature gave to the world extraordinary men that for many a year adorned Tuscany, among whom was one endowed with an excellent and very beautiful genius, by name Antonio da Correggio, a most rare painter, who acquired the modern manner so perfectly and became a most excellent and marvellous craftsman.”

Hanging in the Gemaldegalerie in Dresden, Nativity has a truly outstanding treatment of light with Jesus in Mary’s arms and the angels are reminiscent of those angels on Correggio’s Dome in Parma Cathedral all displaying his luministic effect.

Oil on canvas, Ganymede Abducted by the Eagle is part of a series of four and according to Vasari was destined for King Charles V of Spain. Ganymede is from Homer’s “Iliad” and he is the divine hero from Troy, the most beautiful of all mortals and abducted by Zeus in the form of an eagle.

Antonio Allegri da Correggio, from the Parma School of Italian Art, prefigured many elements of the Baroque, Rococo and Mannerist styles with his vigorous and sensuous High Renaissance elegance; something so few could emulate!

The Cosmic Cycle


What the death and birth of stars means

Stars have a finite amount of fuel, meaning they have a limited lifespan and this follows a pattern.

Stars have extreme mass, high luminosity and huge temperature by Earthly standards, thus, nucleosynthesis has continued right from when the very first star was born.

Nuclear activity powers these stars which is dependent upon the core temperature and mass. Energy is released with the fusing together of nuclei to form heavier ones, and this is part of the lives of stars; living and possibly breathing from one day to the next!

The tiniest stars will live more than a trillion years and far longer than the current age of the Universe; while the biggest stars will live around three million years because they burn their fuel at an exponential rate.

When a stars dies, it leaves behind remnants in the aftermath, that help to generate the next lot.

The best examples of this new generation are Antennae Galaxies; often a brilliant burst of new stars form in massive stellar clusters, thus, the blue color represents very high temperatures.

Gas clouds are where stars are formed. They are identifiable by the red and pink hydrogen characteristics; the dark lanes separate the dense gas clouds, from the dust clouds, and this is the raw material for the following generation!

Astronomers now use X-ray telescopes to see the corpses from earlier generations of stars. Their heat is being radiated away during the cooling period and tears material from companion stars, which generates more energy after the main sequence.

Our Sun is in midlife. By using optical and X-ray images – of antennae galaxies interacting – we can see stars forming; we can see gas clouds and dust clouds waiting to be stars; and we can see remnants of the generation before, being indicated by bright spots on the X-ray.

Not all of the Sun is made from hydrogen. So not all of the mass converts to energy, meaning the life expectancy has to be shortened. Only the difference in mass between hydrogen and helium atoms convert to energy.

The pristine hydrogen in the Sun’s outer layers won’t transport towards the core and this is the only place where temperatures are highest for fusion to occur.

The convective zone doesn’t extend right to the core. The convective zone is where hydrogen is transported to, in order to fuel nuclear reactions; thus, there are no flows of matter because it is separated from the radio active zone. The fuel available to the core is the fuel it was born with and just 10% of the total mass!

This explains the difference between potential lifespan and the greatest age possible.

Energy production clearly decreases as a star runs out of fuel.

When this happens, the balance of outward pressure (of hot gas) and the inward force (of gravity) then breaks down, meaning the core will collapse under its own weight!

When the core collapses, it heats up, and gravitational potential energy, is then converted to thermal energy.

Star forming antennae galaxies give the best results for optical and X-ray images. We can see – often quite clearly – dust clouds waiting to form stars from the dead remnants of the preceding generation. Bright points will show up nicely with the X-ray image.

Actually, lifespan is usually shorter than the estimation, because not all of the Sun is hydrogen and not all is converted to energy.

The assumption in physics that energy cannot be created or destroyed, but converted from one form to another is known as energy conservation and recognizable by e=mc2. A good example is a light bulb which converts electrical energy into heat and light energy.

Chemical energy triggered from the brain is converted all the time by the muscles in our bodies to kinetic movement energy.

Energy in space is stored in an object by virtue of its position in a gravitational field. Thus, when you pick a cup up off a table and put it on a shelf, it represents the conversion of chemical energy to kinetic energy with the muscles moving the cup. But you have to work against gravity to do this. There for some of the muscle / energy is stored in the cup. If it were to fall, it would smash and the gravitational potential energy is converted to kine-synthetic energy, followed by heat and sound energy.

The transfer of energy in these ways as gravity acts upon objects, is fundamental to the field of astronomy. The weight on the core of the Sun causes it to contract, while layers above heat up and once hot enough nuclear fusion occurs in this outer shell of unprocessed hydrogen, as it once did in the core.

This hydrogen shell burning, means when the core continues to contract, it heats up, as gravitational potential energy and is converted into thermal energy, and reaches the point where nuclear reactions become possible.

Helium fuses into heavier elements, while helium nuclei converts to carbon nuclei and helium burns in the reaction chain.

Alpha is the symbol for the helium nucleus, and part of the triple alpha process release of energy, which stops the contraction of the star and stabilizes the star. This process makes up a small percentage of the energy release by the fusion of hydrogen fuel to helium; and it does so at a much higher rate; this, is to support itself against the gravity, and the slide is shorter than the main sequence hydrogen burning phase.

It is the core of the star that triggers the first hydrogen shell to burn. Then the helium core where the burning properties of the surface is different.

As the hydrogen shell burns the rate of energy rises. Energy released is then carried to the surface by convection as a product of nuclear burning, and the radius of the star increases along with the surface area.

This means there is now a bigger supply of energy, but not enough to keep the outer layers of the star at their previous temperature.

The photosphere temperature decreases as well and appears an orangy / red color – A Red Giant – the star has moved according to the HR Diagram, to regions of higher luminosity, but cooler temperatures.

This is a process called ascending the red-giant branch. During the lifetime of a White Dwarf (for a very brief period) it evolves to a very high surface temperature before cooling and fading and on the HR Diagram follows the evolutionary track of a star like our Sun.

The region of the HR Diagram occupied by red giants is the more sparsely populated place on the main sequence; this is because of the much shorter lifetime of this phase, and we now appreciate the relative inefficiency of helium burning, compared to hydrogen burning.

Stars respond to exhaustion of original hydrogen fuel, by fusing helium into heavier elements and this continues the process of nucleosynthesis, fusing lighter elements to make heavier ones.

Also, each carbon nucleus in the core can react with a helium nucleus to make an oxygen nucleus: this triple alpha process is thought to be the main source of oxygen and carbon in the rivers.

There is a final stage to the life of the Sun called starboms and the process of fusing light elements to heavier ones cannot continue indefinitely. The core runs out of helium and contracts under its own gravity, thus heating the core up.

Helium burning starts in the shell around the core. This inert core consists of carbon and oxygen surrounded by concentric helium and hydrogen burning shells. This causes further expansion and cooling of the photosphere at which point the stars radius will be comparable to the radius of the orbit of Mars.

However, when the helium shell burns it doesn’t lead to thermal pulses which would involve expansion and contraction of the shell, and vary the energy output.

A pulse might only last a few thousand years. Further nuclear reactions may occur in the shells which may lead to production of elements as heavy as protons!

These reactions are called S Process Reactions where the ‘S’ implies slow. Thermal pulses alter the pattern of convection within the stars which transport the newly synthesized elements to the stellar surface.

Technetium is unstable and quickly decays to form lighter elements. Nevertheless, it is seen at the surface of a star which means it must continually replenish at the surface.

This processes of convection is what astronomers always thought about evolving stars.

It is with the technetium build up within the star via the S Process, and being brought to the surface via convection, that astronomers can see the interstellar spectators.

The thermal pulses can be so strong that they even push the outer layers of the star in a series of dramatic events.

Through to the origin of the planetary nebulae, beautiful shells of gas were ejected from the central dying star.

When first discovered and observed through small telescopes they looked like the gas giant planets which gave rise to their name. However, they are not directly connected to planets or planet formation.

The only link is that they have taken heavy elements produced by nucleosysnthes with the star and injected them back into space and these heavy elements are raw materials from which planets can one day form.

Planet nebulae come in a bewildering range of shapes and sizes because of rapid rotation of the stars and interaction with a binary companion. The Cat’s Eye Nebula or NGC 654 with a central white dwarf is one example!

Dutch Golden Age Reinvented itself when Jan Vermeer was Rediscovered


This Dutch painter specialised in exquisite, domestic interior scenes of middle class life. Producing relatively few paintings, he left his wife and children in debt at his death.

Vermeer worked slowly with great care using bright colours (usually blue and yellow) and expensive pigments. Mastering the use of light, he painted mainly domestic small rooms of his house with the same furniture and people, depicting mostly women.

With only 34 paintings attributed to him, Vermeer was rediscovered in the 19th century and has since become acknowledged as one of the greatest painters of the Dutch Golden Age.

Little is known about Jan Vermeer, thus his nickname was “The Sphinx of Delft”. We do know that he inherited his family art business when his father died.

Painting from his apartment he married Catherine who gave birth 14 times. His paintings-within-paintings have a unique style, which it is believed was self-taught.

Several factors contributed to Vermeer’s limited oeuvre, such as the fact that he had no pupils, plus he had an enormous number of children and had to run the family inn-keeping and art dealing businesses. Being head of the guild and using such precision in his work must also have contributed.

Vermeer used, in the most lavish way, exorbitantly expensive pigments and natural ultramarine. The earth colours umber and ochre should be understood as warm light within a painting’s strongly-lit interior, which reflects its multiple colours on to the wall creating a world more perfect than he had ever witnessed. He was largely inspired by Leonardo’s observation that the surface of every object takes some of the colour of adjacent objects and therefore no object is ever seen entirely in its natural colour.

Upon his rediscovery, many artists modelled their style on Vermeer’s work and Salvador Dali, being a great admirer, painted his own version of The Lacemaker alongside a rhinoceros. Dali also immortalised the Dutch Masters in The Ghost of Vermeer of Delft Which Can Be Used As a Table.

Vermeer’s Astronomer and Geographer were part of the scientific topic area, once a favourite of Dutch artists. The globe in Astronomer represents his profession and the painting on the wall shows the finding of Moses perhaps representing wisdom and science learned from the Egyptians.

There is a swastika stamped on the back of Astronomer, because it was once confiscated by the Nazis, and is now in the Louvre in Paris having been eventually acquired by the French state in 1983, for inheritance tax purposes, from the Rothschild family.



Hepworth, Pelagos (1946). Elm and strings on oak base, 430 x 460 x 385 mm. Tate Britain, London

Where this interesting name came from

Barbara Hepworth’s work is epitomised by Pelagos. This sculpture combines organic form, natural material and the constructive technique of stringing; thus, synthesizing all of Hepworth’s different earlier works, together.

This is clearly an important piece, having appeared on the front cover of “Studio” and various “Tate Magazine” catalogs in the past.

The form of this sculpture is hollowed out wood to make two spiraling arms; the interior space has been painted pale-blue with a mat finish and she shows her continuity from previous work here, with the preoccupation between light and space.

Though apparently spherical when seen in reproduction, the sculpture’s shape is in fact ovoid, thus the form allows sufficient movement, although there are considerably fewer radial splits than in many of Hepworth’s other wooden pieces.

Art is ever Changing and Evolving which Means its Definition becomes Increasingly more Complicated
To look for a common denominator in art is a mistake since there is just too much variety among works to use a definition, which applies to them all.


With the family resemblance view there may be overlapping similarity between different relatives but no single feature that they all share. Games often resemble each other but what does shove halfpenny and rugby really have in common?

Different masterpieces may have some likeness but no unifying feature which they all share and this makes it difficult for us to provide a definition of art.

Families are all genetically related and all games are pastimes for enjoyment, so we do have a unifying factor but this is unsatisfactory because it needs more precision and something bigger to get at the true meaning – bring on the philosophy of art!

Clive Bell’s significant form theory recognizes an emotion when viewing art that is different from every day life and our practical concerns. This emotion is described by Bell as significant form and refers to its structure rather than its subject matter. In a painting it is the combination of colours and textures.

Sensitive form is a property seen intuitively in a work of art. It must have significant status or value. Some people however have better ability to detect significant form and compare art from completely different cultures and era to the present day.

So what is this aesthetic emotion? Is it produced by a property within a masterpiece? And is it just one emotion for all works of art? What if we don’t get this emotion when experiencing an undeniable work of art?

The idealist theory by Collingwood represents a non-physical element saying it is part of the artists mind. It is given physical expression as a picture but the evaluative element is the emotion being expressed by the artist.

Art and craft are different. Art comes from the imagination ending in the form of a painting, and craft – for example a table – comes from a design and serves a function at the end.

Genuine art has no purpose because it is an end in itself. Entertainment art is inferior as is religious art because it tells a story and lacks that innate concept we are looking for – the essence in a masterpiece.

However, I personally believe it is well down the road to finding the true essence especially with High Renaissance and some of those priceless paintings which reflect so many factors within that artist’s mind with regards to time and place and peer group pressure and materials and budget and politics of that time period and so on. These are all relevant factors and I believe this “thing” we are looking for is a combination of all the features. It is multi-factorial and not just this abstract meaning.

It is strange trying to get inside the artists mind. What we see in the end game is a symptom of what’s gone on in his or her brain, rather than a physical object – oil, canvas, and frame.

Architecture is art and has a specific purpose usually. Shakespeare is art and is designed to entertain which criticises idealist theory, but once again there is something about near perfection in both these examples.

We are moving towards this identifying nature within something that unifies all these examples, with a work of art such as the most beautiful building in the world, or the most original play on stage.

Perhaps Gaudi’s Sagrada Familia in Barcelona or Midsummer Nights Dream – neither of which were plagiarised and were pure figments of their designer’s imagination – possesses this concept of what we really call art.

George Dickie’s institutional theory reckons there are two things Macbeth, Beethoven, a pile of bricks, Eliot’s “Waste Land” and Jonathan Swift’s “Gulliver’s Travels”, all have in common. They have all been worked on by humans and they have all been given status of “masterpiece” or “work of art” by the powers that be, and that would be not just one, subjective individual but a whole group of people in authority on the subject.

However, with institutional theory virtually everything could be seen as art, which means we have to verify these puppeteers who classify something as art before we proceed.

Richard Wollheim said these members of the art world that have the power to make an artefact a work of art must have reasons. There must be logic behind giving something the category of art. Institutional theory reminds us that art is cultural, dependant on social institutions at a particular time rather than some timeless canon.

The artists stated intentions are critical to analysing a work of art, rather than how everybody else interprets their ideas.

Anti-intentionalist theory insists we pay attention only to intentions of the work of art itself. Information from interviews with the artists and their diaries are not relevant. This is psychology and not needed for the meaning of the piece of art the way we are looking it philosophically, but is just one theory – anti-intentionalist.

Internal factors are what we are concerned with. It is the Intentional Fallacy to rely on external factors and a mistake according to Wimsatt and Beardsley. It is based on the idea that once an artist has painted an artwork he has no more control over interpretation of it than anyone else. The artwork is more important than the artist who created it.

The anti-intentionalist claim is about which aspects of a work are relevant to a critical assessment of it. They are happy to include intentions, which are embodied in the work; they just exclude external factors like the psychology of the artist and origin of the piece.

Irony is saying one thing and meaning the opposite. Irony in art is external and can be useful in deciding meaning. Irony is not easily understandable from close analysis but can depict artist’s intentions.

Good art criticism should make use of any available evidence and weight it accordingly, so for example let’s say irony is of limited use for external parts contributing to meaning of an art piece, it should nevertheless be recognized and included.

Performance, interpretation, authenticity when we talk about music, often we mean to suggest that when played on old fashioned instruments it sounds better. This would of course reproduce as closely as possible the sound in the day of say Bach and what his first audiences would have heard. This is of great interest to a historian. It is more authentic but completely different in significance to modern day listeners. Of course the instruments come close to recreating that historical performance, but the atmosphere and musicians can never really extinguish what we have learned since and this will interfere with the performance in a way a truly authentic one – if we could travel back in time – would have appeared back then, experienced by people who were ignorant to modern day productions and couldn’t compare and were listening to what seemed like perfection to them and probably almost was for the time. It is a museum of musical performance though and doesn’t offer the new interpretation of the musicians work, taking it to the next level.

In order to capture the spirit of the composer’s work isn’t necessarily to reproduce the sounds the way they were. If history for history’s sake is the main concern surely we have missed part of the essence. I think a true genius has seen things last the test of time and wishes his or her work to do the same, knowing full well it will change over time – in many cases for the better, but perhaps also for the worse – however the sheer fact that people are still playing the music or acting the play five hundred years later says something about the piece of art and the intention of the artist.

I believe the historical argument provides a good benchmark, is fascinating but like reading Chaucer in Old English or Shakespeare in Middle English, it is just to get a feel for it, when really we use the modern day translation for the bulk of it, for a great many reasons.

Forgeries can have artistic value. There are two types. One is a perfect copy and the other is a painting in the style of a famous artist. The second could easily not have an original from; it was copied, just in someone else’s style and so good it is thought to be by that someone else. This type of forger requires such amazing talent and should the fraud not be treated with high esteem? If he is this good why commit the crime and not be a fantastic artist in his own right? It did and still does happen, whatever the reasoning behind it – criminals appear in all realms of life and there is always a bad egg in every basket, though this bad egg is quite intriguing to me.

The Sotheby Effect puts a single priceless painting at a very high value. The more it is copied, the lower the value, eventually being akin to prints. It is this obsession with the price of a painting that separates it from good fakes. There is the snob value as well, clearly having an original over a perfect copy is desirable even if there is no regard for its artistic value.

Originals are appealing for their relic value as well. The idea that Leonardo da Vinci himself, actually touched the Mona Lisa and paid attention to it, adds something to the picture, thus it is 500 years old and was owned by the King of France – few fakes can claim this.

These reasons for owning a work of art have little to do with artistic merit; so good forgeries should then be as significant as the originals in relation to the artistic value. Or so you might think.

There is no such thing as a perfect fake or forgery. It may fool you and I, and a trained expert, as has happened in the past for that matter, but when the truth be out, it still isn’t quite the same as the original and therefore not as good.

However, the difference is possibly so minor there is no difference in the actual artistic worth of the piece from the point of view of its form, technically.

A top quality artist like Cézanne developed his own style and this originality is part of his achievement and not part of the forgers. The forger’s skill is almost, if not as good, as Paul Cézanne, but Cézanne’s talent is not just as a craftsman but someone with great ideas, innovation, novelty, uniqueness, inventiveness, creativity, freshness and imagination. All of these things do not apply to the fake or the forger!

Forging Cézanne in style but not one of his paintings, on the other hand, does lend itself to a little more artistic merit, but again the forger didn’t create this style even if the iconology is different and creativity is an important aspect of artistic merit, thus belonging to the original and reinforces genuine artwork over copies.

Therefore, we cannot say the forger is equal to Cézanne even if the forger happens to be a genius himself and I think this reinforces the depth of genius of the original artist because if we can see Cézanne in someone else’s work, the plagiarised piece is adding value to the original by emulation.

Morally, a forgery involves an attempt to deceive viewers and this “lie” makes it inferior to original work – even if it were actually better. It may still be an impressive work of art but there is something about honesty and truth in philosophy.

There is no guarantee that a clear, reasoned argument like that attempted above gives convincing answers to these difficult questions, but it does increase the chances of this happening – even in the history of art.