It is early morning in the ancient chinese Song Dynasty capital of Kaifeng. The Director of the Imperial Astronomical Bureau, a man by the name of Yang Weide is fervently writing a message intended for the newly anointed Emperor Renzong of the Zhihe era. In it Yang tells of an auspicious celestial guest, pale red in colour,that has suddenly appeared at dawnbreak in the skies to the south. That in broad daylight is blazes as bright as venus, and has been slowly rising higher in the sky. Recently it has begun to shimmer boldly yellow, the same as the imperial colours. It could only be a divine sign that an enlightened and worthy one has just taken the throne.

Yang Weide remarks that the star Tianguan guards this visitor who has taken residence near the chinese constellations of The Five Chariots (Auriga) and the Three Stars (Orion). A clue that will become critical nearly a millennia later.

_{View of night sky and guest star as it appeared to observers at the time in Kaifeng}

The new emperor is very pleased with this news and sends congratulatory messages to the men of both his Astronomical and Historiographical Bureaus. It is believed that in commemoration of this celestial event, the new emperor in the following months changes the era from Zhehi meaning "attaining harmony" to Jaiyou "auspicious aid."

However, not all who look up and see this new guest in the skies sees it as a prosperous sign. One man, Jhao Bian the Palace Censor, sees this interloper as baleful. A sign that the corruption and malfeasance by various palace members are attracting divine rancor, and that this sign should be feared.

Jhao Bian has been assembling evidence of wrongdoing for the last year in a case against the Grand Chancellor's Office. He informs in his own series of communique to the Emperor that for a year now this trespassers brilliance has not faded. He then goes on to propound that this event is analogous to when Halley's Comet was last sighted and served as an ominous warning to the former Han Dynasty of their impending fall. He implys the same fate would stricken the Emperors reign if corruption was not rooted out. In making his case of warning to the emperor, Jhao Bians even quotes the respected former Han Dynasty Official Gu Yong who said that this was a omen of severe disorder in the palace and rebellion and disaster would spread amongst the realm.

At the same time to the north east, the chinese kingdom of the Liao Dynasty share Mr Jhao's sentiment that this new star in the sky is not a positive sign. Liu Yisou the Editorial Director of the Liao Palace Library writes a memorandum in retrospect almost two years after the arrival of the guest star stating that following a solar eclipse at mid-day a guest star had appeared. That this was considered an astral omen that their beloved emperor Xinzong might die soon. After some time shining brightly the guest gradually faded and departed forever. And true to the prediction the emperor had indeed died.

Yang Weide of the Song Kingdom also notes the celestial guests departure in a second memorandum to the Imperial Court bringing closure to the palace records on the event.

Many other cultures around the world also have records of this event. However, it eventually faded away into the annuls of obscure history for centuries as time marched on. By examining the chinese records of the Song Dynasty's Song Huiyao and Liao Dynasty's Qidan Gao Zhi western astronomers and historians were able to pinpoint the exact date of the guest stars arrival to July 4th, 1054AD. A date that would someday become relevant in connection to unraveling an growing astrological mystery.

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1758 Paris, France.

It has been a long evening and Charles Messier, a accomplished astronomer, pulls his eye away from his humble 4 inch telescope in frustration. "Not a comet!" He mutters to himself. He has been spending the last several nights on the roof of the Hotel de Cluny staring at a soft fuzzy blotch in the evening sky. Ardently searching for comets and becoming annoyed at all the time he has wasted on this let down, he decides to make a list of things hes seeing that he can confirm are not comets. Lest he wastes time on the same objects again by accident later.

He puts this faint splotch down as the first thing on his list of things to dismiss. He dubs it M1. His list of "not comets, so dont waste your time" eventually grew to be 110 items long. Little did he know in another 163 years his first entry, M1, would become much more interesting to astronomers than some lousy comet. He should have given it further study and attention.

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1844 Birr, Ireland

William Parsons the 3rd Earl of Rosse is in his castle squinting at a sketch hes just made after staring all night through his 36 inch telescope at a nebula called Messier Object 1. (M1) 'It looks sorta....like...a crab? I guess' the Earl figures and retires for the night.

_{credit; William Parsons 1844
Parsons' first sketch of the crab nebula. Personally I think it looks like a pineapple}

A few years later in 1848, Parsons got a bigger and better 72 inch telescope and decided to give viewing this crab thing another go. After studying the object he concluded that, whatever it was, it sure didnt look anything like a damned crab. But by then, the name had stuck and henceforth the nebula was to be called the Crab Nebula.

At the time nebulas were regularly observed, but were still every bit as mysterious to scientist as to what they really were. 70 years earlier William Herschel, one of the leading astronomers in studying nebulas in his day believed the nebulas he was seeing were nothing more than faint star clusters too far away to be viewed clearly. It wasn't until he noticed a star inside one of these fuzzy objects that he decided they were some sort of cloud that surrounded stars. But it would still be a while before scientists got any real good traction on the real identies and origins of nebula.

The first good clue didnt come until 1864 when William Huggins discovered that many nebulas light spectrum matched that of excited gas, and therefore these types of nebulas must really be clouds of gasses. These types of nebulas were then refered to as "emmision nebulas."

Later Visto Slipher noticed that some nebula light spectrums matched that of stars and therefore those must be reflections of starlight on some sort of particles that composed the nebulas in question. These were dubbed "reflection nebulas."

But even with these important revelations about the nature of nebulas, nobody was really sure what had caused things like the Crab Nebula to even exist in the first place. The mystery still remained. What had created the Crab Nebula?

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1921 Flagstaff Arizona, United States

Carl Otto Lampland is at the Lowell Observatory viewing the Crab Nebula. He has a nagging thought that ruminates in his head. Something doesnt look right. The Crab Nebula looks different then how he remembers it last. It seems...bigger somehow. He looks at the nebula again and is now adamant. Whatever's happened, the Crab Nebula has changed. He publicaly announces his observation seeking confirmation that he wasn't seeing things.

A few weeks later John Charles Duncan of the Mount Wilson Observatory decides to look into the matter. The observatory lays nestled high in the mountains that serve as a back drop for the city of Los Angeles. A sprawling complex of telescopes spread amongst tall cedar trees growing near the mountains peak over a mile up, the observatory had picture slides of the Crab Nebula dating back to 1909.

Switching back and forth between older and newer pictures of the nebula he did indeed see the changes. It was growing in size and as time went on it was actually growing faster!

A happy coincidence was that in the same year a man named Knut Lundmark was collecting records of chinese "guest stars" in his search of evidence for suspected novae. Novae was a term inspired by the sixteenth century works of Tycho Brahe who was looking for new stars or what he called de nova stella. Lundmark was one of the pioneers who first discovered that some nebula were really objects called galaxies located far outside our own galaxy.

Anyway, he was looking for some new source material and stumbled across details of the events in china that were figured to have taken place in the year 1054AD. He knew that the "guest star" was located near the star Tianguan. And he knew Tianguan was known in the west as Zeta Tauri in the constellation Taurus. And then it dawned on him. All this hubbub about the Crab Nebula making the rounds. It was located right where this guest star in 1054 was supposed to be located.

In 1928 the legendary Edwin Hubble decided that the Crab Nebula wasn't just in the same vicinity, it must have had something directly to do with that "guest star" that the chinese were making such a big deal of in the middle of the Song Dynasty nearly a millennia earlier. But it later took Nicholas Mayall measuring the velocities of gas radiating outwardly from the center of the nebula before the scientific community accepted what the Crab Nebula truly was. He basically said dude look at how fast that gas is expanding. It must be from a star exploding and proclaimed that the guest star of 1054 was really a supernova, a newly coined term in the early 1930s, and that the Crab Nebula was its still expanding remnants.

The Crab Nebula then became the first recognized object associated with a supernova by science. Soon thereafter many other nebulas were connected to records of guest stars and novae observed from the past and discovered to be the remains of supernova. But the chain of discoveries all started with the mystery of the Crab Nebula.

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1967 Cambridge University, England

For three months now Jocelyn Bell, a PhD student has been meticulously inspecting seemingly unending reams of data charts being produced by a 4 acre wide radio telescope array down the road called the Interplanetary Scintillation Array. The telescope is scanning stars in the sky and charting their radio emissions. But what she calls "a bit of scruff" keeps blemishing the chart at one particular location in the sky and to make things even more curious is that this radio pulse is repeating in exactly 1.33 second intervals. She hurries off to notify her professor Antony Hewish of her unexpected finding.

Together they study the readings and realise that whatever is making these signals, they know its not from human interference nor from stars. They dub the anomolous signal LGM-1. LGM standing for Little Green Men as a joke about the unatural appearance of the signal. The then thought being, if its not us and its not the stars than who? Was an extra terrestrial civilization trying to communicate by sending these pulses into the great expanses of space?

Soon another repeating signal was discovered elsewhere in deep space and they figured that this is a natural but not understood phenomena and not aliens reaching out to the universe after all. They christened the phenomena Pulsars. Professor Hewish went on to receive the Nobel Prize for this discovery even though it was actually his student Jocelyn Bell who made the discovery. Even though Bells contribution and deserving of recognition and prize was overlooked because she was merely a student, she says shes not feeling slighted. Personally I'd be pissed about it if I were her. But her career did skyrocket shortly after. So I guess it was all good.

However, nobody knew what these Pulsars really were. One guy had a great theory that Pulsars were unusual stars somewhere between white dwarfs and regular neutron stars in size. Astrophysicist Thomas Gold, who's theory it was, stated that these new novel types of neutron stars he foresaw would have intense rapidly spinning magnetic fields and produce the repeating radio signals observed in pulsars.

But the science community was fickle and thought his theory was stupid. They literally refused him from presenting his theory at the first international conference on pulsars, even though nobody else attending had any good ideas But Tommy stuck to his guns and was vindicated a year later when the Arecibo radio observatory in Puerto Rico discovered a pulsar in the heart of the Crab Nebula. After that, the community was forced to accept his theory.

Accepting Gold's neutron star pulsar theory created a revolution in astrophysics and astronomy for solid state condensed matter physics. Without this breakthrough, who knows where people like Stephen Hawking, Kip Thorne and other physicists who focused their work on the theories of wormholes and black holes would be. And again the Crab Nebula was the critical element in setting off a chain of phenomenal scientific discovery.

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Located in the constellation of Taurus 6,500 light years away and spanning some 11 light years in size the colourful Crab Nebula is still growing at a rate over 930 miles a second. Its an unusual Nebula in the sense that its not some simple emission or reflection nebula nor a typical supernova remnant. It's more of a separate nebula inside a supernova remnant.

When looking at photos of the Crab Nebula you'll see the intensely whitish yellow coloured tendrils and knots of helium and hydrogen expanding outward into a deep reddish orange delicate and lacy fringe. In the heart of the nebula, in juxtaposition, a bright blue glow from electrons traveling just below the speed of light bathe its interior.

_{Close up of the nebula's helium and hydrogen filaments. Mostly from the atmosphere of the star that went supernova leaving a collapsed neutron star in its place}

At the core, surrounding the pulsar, is whats known as a Pulsar Wind Nebulae. This sea shell shaped nebula creates a distinct and sharp boundary where the shockwave of the pulsar's shockingly ferocious solar wind impacts and batters the debris of the supernova remnant. These shock fronts are very dynamic and can be seen changing on a weekly basis. In fact the whole center of the nebula, again thanks to its pulsar, functions like a giant cosmic synchrotron as it accelerates electrons to near the speed of light emitting abundant x-rays.

_{The pulsar PSR B0531+21 in the center of the Crab Nebula. The image is a composite of both visual light (red) and x-rays (blue) emanating from the pulsar. Note the bright whitish shock fronts from the pulsar wind.}

Recently a mystery that has stunned the astrophysics community has been observed in the Nebula. The VERITAS array in Arizona has discovered gamma radiation at energy levels of 400 GeV that periodically erupt from the pulsar wind nebula inside the Crab Nebula. Years earlier, the Fermi telescope was spotting eruptions of these gamma rays at 100GeV that lasted sometimes up to six days in length. Pulsars arent supposed to be able to generate photons at that level of energy. To put things in perspective with 100GeV-400GeV and just how powerful that is. Matter/antimatter annihilation only produces gamma rays at 500KeV! And the physics being used to explain how this may be possible is staggering in its implications.

The physics of pulsars are more complex than we imagined and strange. For instance, the Crab Nebula pumps out optical light in the wavelengths we see at a steady unwavering rate. The same goes for its inner nebula pumping out gamma rays, or so they thought. These eruptions or flare ups come as a surprise in that they are 30 times stronger than average for the nebula.

Studies have shown that although the neutron star forming the pulsar in the Crab Nebula is only 12 miles in diameter, because it spins so fast at 33 times a second, its magnetosphere creates a superconducting column of plasma 620 miles in diameter in which electrons are shot up to hard to fathom power levels as they jump between gaps in the magnetic field lines. This is the source of its regular output of gamma rays.

But, scientists are a bit puzzled at the exact mechanism in which photons in the superconducting column are produced to such extreme levels during these flares. The leading theory is that the outer magnetic field lines sometime meet head on while traveling in opposite directions and reorganise casting off the unprecedented gamma flares. This will be a subject of study for some time until a concrete theory is worked out. Regardless of the physics needed to produce such phenomena, the Crab Nebula again sets a standard for being the first discovery of Ultra High Energy Cosmic Rays. The Crab Nebula also sets the record for the most powerful photons and cosmic rays ever observed by us humans anywhere. Nothing even in labs has been seen of this magnitude when it comes to the energy levels of photons.

In the meantime, the pulsar in the Crab Nebula is used by astronomers to calibrate their x-ray telescopes. Its even got a unit of measurement the "millicrab" named after it. But true to form, the Crab Nebula continues to surprise astrophysicists with the unexpected. Lately they've noticed the wavelengths of x rays eminating from its pulsar fluctuating up to 3 percent. Something its never done before. For most experiments by instruments calibrated by using the Crab Nebula, thats throws results barely perceptibly. For other more sensitive experiments it throws the results out as completely unusable altogether. It is believed the pulsar winds themselves are the source of these fluctuations.

One last yet to be solved mystery of the Crab Nebula is its mass. The weight of the nebulas mass falls far short of the mass of the star that went supernova. Nobody's sure where the bulk of the missing matter from the former star disappeared to or how.

Who knows what future mysteries, surprises and breakthroughs the Crab Nebula will gift us.

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Next time you look up to the night sky and are perhaps looking at Orion, take a moment to pan your view from Betelgeuse, the red star forming Orion's upper shoulder, towards a bright white star named Capella soaring a ways over the hunters head. About halfway in the middle will be the Crab Nebula. Although not visible with the naked eye if youre in a location dark enough and have fairly powerful binoculars or a modest telescope you might see a faint bluish grey smudge of light called M1. Hopefully whether you see M1 or not, you can still appreciate the significance and history that little piece of sky holds.

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Thank you for taking the time to read this article. Hopefully you found it intriguing and enjoyable. Until next time.

I love comments and will answer each and every one! So if you're inclined, i encourage you to do so.

Best,

Steemydave

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All photos are public domain and sourced from the following links.

https://en.m.wikipedia.org/wiki/Crab_Nebula
https://en.m.wikipedia.org/wiki/SN_1054

Final photo sourced from Pixabay.com