APOD: M1: The Crab Nebula from Hubble (2020 Sep 06)

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APOD: M1: The Crab Nebula from Hubble (2020 Sep 06)

Post by APOD Robot » Sun Sep 06, 2020 4:05 am

Image M1: The Crab Nebula from Hubble

Explanation: This is the mess that is left when a star explodes. The Crab Nebula, the result of a supernova seen in 1054 AD, is filled with mysterious filaments. The filaments are not only tremendously complex, but appear to have less mass than expelled in the original supernova and a higher speed than expected from a free explosion. The featured image, taken by the Hubble Space Telescope, is presentedi in three colors chosen for scientific interest. The Crab Nebula spans about 10 light-years. In the nebula's very center lies a pulsar: a neutron star as massive as the Sun but with only the size of a small town. The Crab Pulsar rotates about 30 times each second.

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Re: APOD: M1: The Crab Nebula from Hubble (2020 Sep 06)

Post by heehaw » Sun Sep 06, 2020 9:30 am

It was 1969 and I was a postdoc at the US Naval Research Lab. We'd launched an Aerobee and collected X-rays from the Crab, and Herb Friedman had asked me to write a fortran program to analyze the X-rays to look for periodicity: the pulsar known to be there. I walked to the computer center to collect my printed output. There it was! For about an hour, I was the only person who knew that the X-rays (a fraction of them) also pulsed with the period of the optical pulsar...

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Re: APOD: M1: The Crab Nebula from Hubble (2020 Sep 06)

Post by BDanielMayfield » Sun Sep 06, 2020 11:50 am

The explanation's link to 1054 AD's first paragraph says this:
On July 4, 1054 A.D., Chinese astronomers noted a "guest star" in the constellation Taurus; Simon Mitton lists 5 independent preserved Far-East records of this event (one of 75 authentic guest stars - novae and supernovae, excluding comets - systematically recorded by Chinese astronomers between 532 B.C. and 1064 A.D., according to Simon Mitton). This star became about 4 times brighter than Venus in its brightest light, or about mag -6, and was visible in daylight for 23 days.
Therefore astronomers are quite confident we know exactly when the Supernova that created the Crab Nebula occurred. However, the above link also says this:
Strangely enough, it seems that at least almost no records of European or Arab observations of the supernova have survived to modern times.
Surely a "new star" so bright it could be seen during the day would have been noted in Europe, north Africa and the Middle East. I'm guessing we can thank blame the Crusades and the Dark Ages for this glaring omission from western history.
Just as zero is not equal to infinity, everything coming from nothing is illogical.

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Re: APOD: M1: The Crab Nebula from Hubble (2020 Sep 06)

Post by BDanielMayfield » Sun Sep 06, 2020 12:33 pm

APOD Robot wrote:
Sun Sep 06, 2020 4:05 am
The filaments are not only tremendously complex, but appear to have less mass than expelled in the original supernova and a higher speed than expected from a free explosion.
That sentence prompted drilling down, leading to this puzzling set of facts: The "less mass than expected" link goes to a paper whose abstract concludes:
The absence of any evidence at radio wavelengths that either the Crab Nebula or a hypothetical shell is interacting with the ambient medium leads to an interpretation that the supernova of A.D. 1054 was a peculiar low-energy event.
But the "higher speed than expected" links to an abstract saying
Published images of the Crab Nebula have been scanned and measured to derive proper motions, the age of the nebula, and its point of origin. Astrometric reductions provided rms errors ranging from 0.14" to 0.31" in both axes for a given image. Proper motions of 50 optical filaments with a 53 yr baseline projected backward indicates the mean date of the supernova event as a.d. 1130 +/- 16 yr, in good agreement with previous investigations by Trimble and Wyckoff & Murray but 76 yr after the reported outburst recorded by the Chinese astronomers in a.d. 1054. This result confirms the well-known acceleration in the Crab's expansion. The image-scanning technique demonstrates that accurate astrometric reductions can be achieved on a personal computer.
So this SN was both low-energy AND produced an ACCELERATING expansion :!: :?: Very puzzling.
Just as zero is not equal to infinity, everything coming from nothing is illogical.

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Re: APOD: M1: The Crab Nebula from Hubble (2020 Sep 06)

Post by orin stepanek » Sun Sep 06, 2020 12:47 pm

CrabNebula_Hubble_960.jpg

If there is such a thing as a happy crab; this one would probably
Qualify! 🥰 It is a cute crab anyhow! 8-)
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Re: APOD: M1: The Crab Nebula from Hubble (2020 Sep 06)

Post by neufer » Sun Sep 06, 2020 1:50 pm

heehaw wrote:
Sun Sep 06, 2020 9:30 am

It was 1969 and I was a postdoc at the US Naval Research Lab. We'd launched an Aerobee and collected X-rays from the Crab, and Herb Friedman had asked me to write a fortran program to analyze the X-rays to look for periodicity: the pulsar known to be there. I walked to the computer center to collect my printed output. There it was! For about an hour, I was the only person who knew that the X-rays (a fraction of them) also pulsed with the period of the optical pulsar...
  • Modulo 2 FFT :?:
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Re: APOD: M1: The Crab Nebula from Hubble (2020 Sep 06)

Post by E Fish » Sun Sep 06, 2020 1:51 pm

BDanielMayfield wrote:
Sun Sep 06, 2020 11:50 am
The explanation's link to 1054 AD's first paragraph says this:
On July 4, 1054 A.D., Chinese astronomers noted a "guest star" in the constellation Taurus; Simon Mitton lists 5 independent preserved Far-East records of this event (one of 75 authentic guest stars - novae and supernovae, excluding comets - systematically recorded by Chinese astronomers between 532 B.C. and 1064 A.D., according to Simon Mitton). This star became about 4 times brighter than Venus in its brightest light, or about mag -6, and was visible in daylight for 23 days.
Therefore astronomers are quite confident we know exactly when the Supernova that created the Crab Nebula occurred. However, the above link also says this:
Strangely enough, it seems that at least almost no records of European or Arab observations of the supernova have survived to modern times.
Surely a "new star" so bright it could be seen during the day would have been noted in Europe, north Africa and the Middle East. I'm guessing we can thank blame the Crusades and the Dark Ages for this glaring omission from western history.
Not the Crusades. They didn't begin until 1095. It's hard to say what the explanation is because this is the beginning of the High Middle Ages when Europe is beginning to recover, and in addition, the Muslim world was in its golden age of art and science, with some of the most famous Arab astronomers working during this time. One possibility is that, because of the scientific understanding of the time (a geocentric universe which is perfect, eternal and unchanging, thanks to Aristotle), something like that would be less likely to be noticed for what it was. This happened more than once in history. The planet Uranus was observed multiple times before William Herschel "discovered" it. However, it was marked down on earlier star charts variously as a comet (seen as a meteorological event) or simply a star that hadn't been noticed before. Why? Because they knew how many planets there were. The idea that there could be more was ludicrous.

But other supernovae were recorded in Europe. In 1006, there was a supernova that was observed around the entire planet. We have sources from nearly every continent. A few hundred years later, Tycho Brahe and Johannes Kepler were both fortunate enough to observe supernovae.

But it could also simply be the vagaries of what gets preserved. We have original texts going back thousands of years, but we also have lists of works written by famous philosophers that we've never been able to read because, for whatever reason, those didn't get preserved. For example, we actually don't have Aristotle's works. We have the equivalent of lecture notes. We know that he published works, but they didn't get preserved. That makes historians wonder if we really know what Aristotle said in his philosophy or if we have someone else's interpretation of what he said. Such are the frustrations of history. :)

There's your mini lecture for Sunday morning. :)

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Re: APOD: M1: The Crab Nebula from Hubble (2020 Sep 06)

Post by BDanielMayfield » Sun Sep 06, 2020 2:39 pm

E Fish wrote:
Sun Sep 06, 2020 1:51 pm
BDanielMayfield wrote:
Sun Sep 06, 2020 11:50 am
The explanation's link to 1054 AD's first paragraph says this:
On July 4, 1054 A.D., Chinese astronomers noted a "guest star" in the constellation Taurus; Simon Mitton lists 5 independent preserved Far-East records of this event (one of 75 authentic guest stars - novae and supernovae, excluding comets - systematically recorded by Chinese astronomers between 532 B.C. and 1064 A.D., according to Simon Mitton). This star became about 4 times brighter than Venus in its brightest light, or about mag -6, and was visible in daylight for 23 days.
Therefore astronomers are quite confident we know exactly when the Supernova that created the Crab Nebula occurred. However, the above link also says this:
Strangely enough, it seems that at least almost no records of European or Arab observations of the supernova have survived to modern times.
Surely a "new star" so bright it could be seen during the day would have been noted in Europe, north Africa and the Middle East. I'm guessing we can thank blame the Crusades and the Dark Ages for this glaring omission from western history.
Not the Crusades. They didn't begin until 1095. It's hard to say what the explanation is because this is the beginning of the High Middle Ages when Europe is beginning to recover, and in addition, the Muslim world was in its golden age of art and science, with some of the most famous Arab astronomers working during this time. One possibility is that, because of the scientific understanding of the time (a geocentric universe which is perfect, eternal and unchanging, thanks to Aristotle), something like that would be less likely to be noticed for what it was. This happened more than once in history. The planet Uranus was observed multiple times before William Herschel "discovered" it. However, it was marked down on earlier star charts variously as a comet (seen as a meteorological event) or simply a star that hadn't been noticed before. Why? Because they knew how many planets there were. The idea that there could be more was ludicrous.

But other supernovae were recorded in Europe. In 1006, there was a supernova that was observed around the entire planet. We have sources from nearly every continent. A few hundred years later, Tycho Brahe and Johannes Kepler were both fortunate enough to observe supernovae.

But it could also simply be the vagaries of what gets preserved. We have original texts going back thousands of years, but we also have lists of works written by famous philosophers that we've never been able to read because, for whatever reason, those didn't get preserved. For example, we actually don't have Aristotle's works. We have the equivalent of lecture notes. We know that he published works, but they didn't get preserved. That makes historians wonder if we really know what Aristotle said in his philosophy or if we have someone else's interpretation of what he said. Such are the frustrations of history. :)

There's your mini lecture for Sunday morning. :)
And a good lecture it was E Fish. I was hoping someone with a better knowledge of history would weigh in on this. Glad to learn when the Crusades started.

My thinking was that astronomers in the western and mid parts of the old world must have noted (written down) accounts of the new star, but with all the numerous wars, Crusades, Jihads etc. the records have been lost over time. This fits with your points about all the other writings that have been lost too.

I wonder also if superstitious fear may have limited the number of records made in the west. Just think how terror prone many must have been at the time, seeing this strange apparition in the sky for 23 days. Then, when it was over, well, that doesn't fit our world view, so let's cover it up.
Just as zero is not equal to infinity, everything coming from nothing is illogical.

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Re: APOD: M1: The Crab Nebula from Hubble (2020 Sep 06)

Post by neufer » Sun Sep 06, 2020 3:23 pm

BDanielMayfield wrote:
Sun Sep 06, 2020 2:39 pm
E Fish wrote:
Sun Sep 06, 2020 1:51 pm
Surely a "new star" so bright it could be seen during the day would have been noted in Europe, north Africa and the Middle East. I'm guessing we can thank blame the Crusades and the Dark Ages for this glaring omission from western history.
Not the Crusades. They didn't begin until 1095. It's hard to say what the explanation is because this is the beginning of the High Middle Ages when Europe is beginning to recover, and in addition, the Muslim world was in its golden age of art and science, with some of the most famous Arab astronomers working during this time. One possibility is that, because of the scientific understanding of the time (a geocentric universe which is perfect, eternal and unchanging, thanks to Aristotle), something like that would be less likely to be noticed for what it was.

But other supernovae were recorded in Europe. In 1006, there was a supernova that was observed around the entire planet. We have sources from nearly every continent. A few hundred years later, Tycho Brahe and Johannes Kepler were both fortunate enough to observe supernovae.

But it could also simply be the vagaries of what gets preserved. We have original texts going back thousands of years, but we also have lists of works written by famous philosophers that we've never been able to read because, for whatever reason, those didn't get preserved. For example, we actually don't have Aristotle's works. We have the equivalent of lecture notes. We know that he published works, but they didn't get preserved. That makes historians wonder if we really know what Aristotle said in his philosophy or if we have someone else's interpretation of what he said. Such are the frustrations of history. :)
My thinking was that astronomers in the western and mid parts of the old world must have noted (written down) accounts of the new star, but with all the numerous wars, Crusades, Jihads etc. the records have been lost over time. This fits with your points about all the other writings that have been lost too. I wonder also if superstitious fear may have limited the number of records made in the west. Just think how terror prone many must have been at the time, seeing this strange apparition in the sky for 23 days. Then, when it was over, well, that doesn't fit our world view, so let's cover it up.
Note that 4 July is NOT really the best time to be visually observing Taurus
  • ...especially at higher northern latitudes.
https://en.wikipedia.org/wiki/Crab_Nebula#Solar wrote:
<<The Sun's corona passes in front of the Crab Nebula every June. Variations in the radio waves received from the Crab Nebula at this time can be used to infer details about the corona's density and structure. Early observations established that the corona extended out to much greater distances than had previously been thought; later observations found that the corona contained substantial density variations.>>
https://en.wikipedia.org/wiki/Taurus_(constellation) wrote:
<<Several stars in the Hyades star cluster, including Kappa Tauri, were photographed during the total solar eclipse of May 29, 1919, by the expedition of Arthur Eddington in Príncipe and others in Sobral, Brazil, that confirmed Albert Einstein's prediction of the bending of light around the Sun according to his general theory of relativity which he published in 1915.>>
https://en.wikipedia.org/wiki/Crab_Nebula#Connection_to_SN_1054 wrote:
<<In the early twentieth century, the analysis of early photographs of the Crab Nebula taken several years apart revealed that it was expanding. Tracing the expansion back revealed that the nebula must have become visible on Earth about 900 years before. Historical records revealed that a new star bright enough to be seen in the daytime had been recorded in the same part of the sky by Chinese astronomers on 4 July 1054. After the original connection to the observations made by Chinese astronomers, in 1934 connections were made to a 13th-century Japanese reference to a "guest star" in Meigetsuki.>>
Art Neuendorffer

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Re: APOD: M1: The Crab Nebula from Hubble (2020 Sep 06)

Post by johnnydeep » Sun Sep 06, 2020 4:46 pm

Neutron stars are one of my favorite things. This in no small part due to the book Dragon's Egg, by Robert Forward. It's about life on a neutron star, and is considered a classic of "hard sci-fi". From https://en.wikipedia.org/wiki/Dragon's_Egg
Dragon's Egg is a 1980 hard science fiction novel by Robert L. Forward. In the story, Dragon's Egg is a neutron star with a surface gravity 67 billion times that of Earth, and inhabited by cheela, intelligent creatures the size of a sesame seed who live, think and develop a million times faster than humans. Most of the novel, from May to June 2050, chronicles the cheela civilization beginning with its discovery of agriculture to advanced technology and its first face-to-face contact with humans, who are observing the hyper-rapid evolution of the cheela civilization from orbit around Dragon's Egg.

The novel is regarded as a landmark in hard science fiction. As is typical of the genre, Dragon's Egg attempts to communicate unfamiliar ideas and imaginative scenes while giving adequate attention to the known scientific principles involved.

Plot Summary

Half a million years ago and 50 light-years from Earth, a star in the constellation Draco turns supernova, and the star's remnant becomes a neutron star. The radiation from the explosion causes mutations in many Earth organisms, including a group of hominina that become the ancestors of Homo sapiens. The star's short-lived plasma jets are lop-sided because of anomalies in its magnetic field, and set it on a course passing within 250 astronomical units of the Sun. In 2020 AD, human astronomers detect the neutron star, call it "Dragon's Egg", and in 2050 they send an expedition to explore it.

The star contains about half of a solar mass of matter, compressed into a diameter of about 20 kilometers (12 miles), making its surface gravity 67 billion times that of Earth. Its outer crust, compressed to about 7,000 kg per cubic centimeter, is mainly iron nuclei with a high concentration of neutrons,[1] overlaid with about 1 millimeter (0.039 inches) of white dwarf star material.[2] The atmosphere, mostly iron vapor, is about 5 centimeters (2.0 inches) thick. The star shrinks slightly as it cools, causes the crust to crack and produce mountains 5 to 100 millimeters (0.20 to 3.94 inches) high. Large volcanos, formed by liquid material oozing from deep cracks, can be many centimeters high and hundred meters in diameters, and will eventually collapse, causing starquakes.[1]

Around 3000 BC Dragon's Egg cools enough to allow a stable equivalent of "chemistry", in which "compounds" are constructed of nuclei bound by the strong force, rather than of Earth's atoms bound by the electromagnetic force. As the star's chemical processes are about one million times faster than Earth's, self-replicating "molecules" appear shortly and life begins on the star. As the star continues to cool, more complex life evolves, until plant-like organisms appear around 1000 BC. One lineage of these later became the first "animals", the earliest of these stealing seedpods from sessile organisms and some later lineages becoming predators.[3]

The adults of the star's most intelligent species, called cheela (no flexion for gender or number), have about the same mass as an adult human. However, the extreme gravity of Dragon's Egg compresses the cheela to the volume of a sesame seed,[2] but with a flattened shape about 0.5 millimeters (0.020 inches) high and about 5 millimeters (0.20 inches) in diameter. Their eyes are 0.1 millimeters (0.0039 inches) wide. Such minute eyes can see clearly only in ultraviolet and, in good light, the longest wavelengths of the X-ray band.[3]
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Re: APOD: M1: The Crab Nebula from Hubble (2020 Sep 06)

Post by BDanielMayfield » Sun Sep 06, 2020 6:29 pm

neufer wrote:
Sun Sep 06, 2020 3:23 pm
BDanielMayfield wrote:
Sun Sep 06, 2020 2:39 pm
My thinking was that astronomers in the western and mid parts of the old world must have noted (written down) accounts of the new star, but with all the numerous wars, Crusades, Jihads etc. the records have been lost over time. This fits with your points about all the other writings that have been lost too. I wonder also if superstitious fear may have limited the number of records made in the west. Just think how terror prone many must have been at the time, seeing this strange apparition in the sky for 23 days. Then, when it was over, well, that doesn't fit our world view, so let's cover it up.
Note that 4 July is NOT really the best time to be visually observing Taurus
  • ...especially at higher northern latitudes.
https://en.wikipedia.org/wiki/Crab_Nebula#Solar wrote:
<<The Sun's corona passes in front of the Crab Nebula every June. Variations in the radio waves received from the Crab Nebula at this time can be used to infer details about the corona's density and structure. Early observations established that the corona extended out to much greater distances than had previously been thought; later observations found that the corona contained substantial density variations.>>
https://en.wikipedia.org/wiki/Taurus_(constellation) wrote:
<<Several stars in the Hyades star cluster, including Kappa Tauri, were photographed during the total solar eclipse of May 29, 1919, by the expedition of Arthur Eddington in Príncipe and others in Sobral, Brazil, that confirmed Albert Einstein's prediction of the bending of light around the Sun according to his general theory of relativity which he published in 1915.>>
https://en.wikipedia.org/wiki/Crab_Nebula#Connection_to_SN_1054 wrote:
<<In the early twentieth century, the analysis of early photographs of the Crab Nebula taken several years apart revealed that it was expanding. Tracing the expansion back revealed that the nebula must have become visible on Earth about 900 years before. Historical records revealed that a new star bright enough to be seen in the daytime had been recorded in the same part of the sky by Chinese astronomers on 4 July 1054. After the original connection to the observations made by Chinese astronomers, in 1934 connections were made to a 13th-century Japanese reference to a "guest star" in Meigetsuki.>>
I wouldn't let our European and/or Middle Eastern ancestors off the hook so easily Art. After all, if the Chinese and Japanese could see it, so could the Europeans. And it was visible during the DAY! All you would have needed to do to notice it was glance towards the Sun. Sunrises and sunsets would have been extraordinary, with the Sun looking like it had a baby sibling nearby.
Just as zero is not equal to infinity, everything coming from nothing is illogical.

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What the Heck Happened in 1054?

Post by BDanielMayfield » Sun Sep 06, 2020 7:16 pm

This lack of reports of SN 1054 from the Western Old World made me wonder what else was happening back then. Could any of these notable events have contributed somehow?
wikipedia/1054 wrote:By place

Byzantine Empire
Sultan Tughril leads a large Seljuk army out of Azerbaijan into Armenia, possibly to consolidate his frontier, while providing an incentive to his Turkoman allies in the form of plunder. Tughril divides his army into four columns, ordering three to veer off to the north to raid into central and northern Armenia, while he takes the fourth column towards Lake Van. The Seljuk Turks capture and sack the fortress city of Artchesh, after an 8-day siege.[1]

Europe
Battle of Mortemer: The Normans, led by Duke William the Bastard, defeat a French army (near Mortemer), as it is caught pillaging and plundering. King Henry I of France withdraws his main army from Normandy as a result. Guy I (or Wido), count of Ponthieu, is captured during the course of the battle.

Scotland
July 27 – Siward, earl of Northumbria, invades Scotland, to support King Malcolm III against Macbeth, who has usurped the Scottish throne from Malcolm's father, Duncan I. Macbeth is defeated at Dunsinane.

Africa
The Almoravids retake the trading center of Aoudaghost from the Ghana Empire. Repeated Almoravid incursions, aimed at seizing control of the trans-Saharan gold trade, disrupt Ghana's dominance of the trade routes.[2]

Asia
Lý Nhật Tôn, third king of the Lý Dynasty, begins to rule in Vietnam, and changes the country's official name to Đại Việt.

By topic

Astronomy
July 4 (approx.) – SN 1054, a supernova, is first observed by the Chinese, Arabs and possibly Native Americans, near the star Zeta Tauri.[3] For 23 days it remains bright enough to be seen in daylight. Its remnants form the Crab Nebula (NGC 1952).[4]

Religion
Spring – Pope Leo IX sends a legatine mission, under Cardinal Humbert of Silva Candida, to Constantinople, to negotiate with Patriarch Michael I Cerularius, in response to his actions concerning the church in Constantinople.[5]
July 16 – Humbert of Silva Candida, representative of the newly deceased Leo IX, breaks the relations between Western and Eastern Churches, through the act of placing an invalidly-issued Papal Bull of excommunication during the celebration of the Divine Liturgy (See East-West Schism).
The East–West Schism (also the Great Schism or Schism of 1054) is the break of communion since the 11th century between the Catholic Church and Eastern Orthodox Churches.[1] The schism was the culmination of theological and political differences which had developed during the preceding centuries between Eastern and Western Christianity.
I note that the East-West Schism happened in the middle (near or even at brightest point?) of this SN's appearance :!:

I make no claim that this is anything but a cosmic coincidence, but the juxtaposition of events might have freaked people out somewhat :shock:
Just as zero is not equal to infinity, everything coming from nothing is illogical.

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Re: APOD: M1: The Crab Nebula from Hubble (2020 Sep 06)

Post by BDanielMayfield » Mon Sep 07, 2020 3:04 am

This discussion took an interesting historical side trip, but I remain intrigued by the unanswered questions re the SN itself. Specifically, how can the blast wave from this or any SN keep accelerating outwards for hundreds of years :?: Is there a known or suspected cause?
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Re: APOD: M1: The Crab Nebula from Hubble (2020 Sep 06)

Post by neufer » Mon Sep 07, 2020 3:21 am

BDanielMayfield wrote:
Sun Sep 06, 2020 6:29 pm

I wouldn't let our European and/or Middle Eastern ancestors off the hook so easily Art. After all, if the Chinese and Japanese could see it, so could the Europeans. And it was visible during the DAY! All you would have needed to do to notice it was glance towards the Sun. Sunrises and sunsets would have been extraordinary, with the Sun looking like it had a baby sibling nearby.
  • Sunrises perhaps (not sunsets).
Besides being professionals with the possibility of loosing their heads
Chinese astrologers had a reason to keep an eye on Taurus in 1054. :arrow:
http://eclipsewise.com/solar/SEprime/1001-1100/SE1054May10Tprime.html wrote:
<<The Total Solar Eclipse of 1054 May 10 is visible from the geographic regions shown on the map to the right. The instant of greatest eclipse takes place on 1054 May 10 at 07:40:20 TD (07:18:60 UT1). During the eclipse, the Sun is in the constellation Taurus. The total solar eclipse of 1054 May 10 was preceded two weeks earlier by a penumbral lunar eclipse on 1054 Apr 24.>>
Art Neuendorffer