Rare Things Happen All The Time

Posted on 2011/07/15


Feature Image - Guest Stars

It has been well understood for thousands of years, by some at least, that the lights in the night’s sky would move depending on the time, and date. We now know this to be due to the rotation of the Earth on its axis and the orbit of the Earth around the sun.

But, it was also noticed that some objects didn’t follow the flow of the others. We called them the wanderers – which they are still called today. The word that was once used by the Greeks, πλανήτης (pronounced planētēs), we inherit as our word ‘planet‘.

But, scientists are in search for regularities. Eventually, despite this continuous flux, some constant properties of the sky were established. It was concluded, due to the observed constant repetition, that even if the positions of these celestial objects changed, the content of the sky remained stable.

Aristotle decided, as was fashionable at the time, that this permanence was provable by means of the following explanation:

Wherefore, the sun and the stars, and the entire firmament, perpetually energizes. No apprehension, also, is there lest at any time they may come to a stand-still.

[Note] Aristotle invested the stars with divinity and therefore maintained their imperishableness.

Aristotle’s Metaphysics (c. 360BC) – the 1857 Translation (with notes) by Rev. John H. M’Mahon, M.A.

Supporters of Aristotle at least, were satisfied with this neat proof.

But, every few generations, these idea were challenged with what appeared to be a new object in the sky. The Chinese called them ‘new stars‘ and they, amongst others, made some very detailed observations for their ancestors to ponder.

Many such reported sightings of new stars have since been determined to be Halley’s Comet, due to Edmond Halley’s discovery the regularity of the comet’s orbit. In 1705, he established that many previous sightings of comets were in fact the same object. Since then, many more historical sightings of new stars from around the world have been determined to the very same comet of Halley.

Not only was Aristotle incorrect, but Halley predicted he was wrong periodically, every 76 years.

Yet, even after this discovery, many historical reports of these ‘guest stars‘, as the Chinese called them, remained unexplained. It took the technology of modern, 20th century astronomy to determine that some the reports were very likely supernova – exploded stars.

We have 9 plausible remnants of supernova which correspond with historical records. Below, I outline how each of these were linked to documents of guest stars. The people working on the Chandra Observatory have also produced a good timeline of the historical supernovae.

How Supernovae Remnants are Linked with Historical Accounts of Guest Stars.

Briefly, here is the logical thread:

  • Several reports of guest stars claimed they appeared, sometime very brightly, where previously there was darkness. This would persist sometimes for several months before gradually dimming away.
  • Some of these reports, especially the later ones, gave very specific information about the location of these guest stars.
  • Modern astronomers have located several dust clouds that correspond with what nuclear physicists predict happens to some stars as their nuclear energy depetes.
  • When astronomers pointed their telescopes at the reported locations of guests stars, they found similar supernovae remnants.
  • No only are these remnants in just the right place, but they can also be dated. By looking at the speed at which the dust clouds expands (with Doppler Effect data), astronomers can extrapolate backwards in time to determine the date of the supernovae. It is a similar method as when measuring the red-shift of galaxies to determine the time of the Big Bang.

A Note About the Images Below

The images below are unquestionably very beautiful. But many of my students have asked, ‘are they real?’ In the past, these images were always assumed to be real, because no one knew how to create them artificially. But this generation, who live in a time of high fidelity computer graphics, might be the first to raise such serious and justifiable doubts.

The images are real in the sense that they have been constructed only with light from these distant points in space. However, if you were to aim even the most capable optical telescope towards these sights, you might be disappointed in what you see. There is a glimpse of something interesting, but only a squint of an image. This isn’t the telescope’s fault, but our own. In a cosmic sense, we are all mostly blind. We only see a small fraction of the light that arrives to us from these far off objects.


But, with the help of scientific inventions, we can open wide our technological eyes and get the full story. The Chandra Observatory can look at the X-Rays, Spitzer views infrared, while the Hubble Space Telescope fills in the narrow gap of visible light. But, even though our inventions can see these sights, our feeble eyes still cannot. These images need to be translated to our realm of experience and false colour representations are made of the non-visible light. This is the limit of human perception, and the resulting images below are as real as we are able to perceive.

Each supernovae reminant is classified with ‘SN’ for ‘supernova’ followed by the date they were originally observed.

SN 185 (G315.4-2.3)


“In the second year of the Chung-phing reign period, the 10th month, on a Keui-day (December 7, AD 185), a ‘guest star’ appeared in the midst of the Southern Gate (Nanmen, an ancient Chinese asterism, near α Centauri). It seemed to be as large as half a bamboo mat, and showed five coloursin turn, now brightening, now dimming. It diminished in brightness little by little and finally disappeared in the sixth month of the hou-year (hou-nian, 24 July to 23 August AD 187)”

Astrological Annals of the Hou Han Shu (China)

Fu-Yuan Zhao, R. G. Strom, Shi-Yang Jiang (2006) ‘The Guest Star of AD185 must have been a Supernova’ Chin. J. Astron. Astrophys. Vol. 6, No. 5, 635–640

Xi Ze-xong and Bo Sh-ren (1965) ‘Ancient Novae and Supernovae Recorded in the Annals of China, Korea, and Japan and the their Significance in Radioastronomy’ Acta Astronomic& Sinica (NASA), Vol. 13, No. 1

So, this guest star was observed somewhere near Alpha Centauri in 187AD. The location of the image above, and the estimate of the supernova from studying the dust cloud suggest a strong match.

SN 386 (G11.2 -0.3)


“In the third month, in the spring of the 11th year of Thai Ho reign period of Chin dynasty (24th March – 22nd April 369AD), a guest star was seen in the Western Wall of the Purple Palace (Tzu Kung Hsi Yuan, or the intersection of Draco, Ursa Major and Lynx). In the 7th month, it disappeared (19th October – 17th September 369AD).”

Chin Sui, Thung Chi, Wen Hsien, Thung Khao (China)

Xi Ze-xong and Bo Sh-ren (1965) ‘Ancient Novae and Supernovae Recorded in the Annals of China, Korea, and Japan and the their Significance in Radioastronomy’ Acta Astronomic& Sinica (NASA), Vol. 13, No. 1

While this guest star was observed at the intersection Draco, Ursa Major and Lynx in 386AD, the above image was found in the constellation Norma. However the date estimates match very closely to the reports.

SN 393 (G347.3-0.5)


‘In the second month, the spring of the 18th year of Thai Yuan peroid, Chin dynasty’

Chin Sui, Thung Chi, Wen Hsien, Thung Khao (China)

Appeared from 7th of February to 28th of March 393AD – Dissappeared from 22nd of October to 19th of November 393AD in Scorpius

Xi Ze-xong and Bo Sh-ren (1965) ‘Ancient Novae and Supernovae Recorded in the Annals of China, Korea, and Japan and the their Significance in Radioastronomy’ Acta Astronomic& Sinica (NASA), Vol. 13, No. 1

There are fewer historical sightings of this remnant, but the location matches very well with this 393AD report.

SN 1006


On the I-ssu Day of the 3rd month, the 3rd year of the Chhin Te reign of the Sung dynasty (3rd April 1006AD), a guest star appeared in the southeast

Sung Shu (China)

In Japan during the Kan Ko period, after the Kuei Yu night of the 2nd day of the 4th month of the 3rd year (1st May 1006AD), a big guest star appeared in the Chhi Kwan (κ star of Lupus)

‘Record of the Bright Moon’ (Japan)

Xi Ze-xong and Bo Sh-ren (1965) ‘Ancient Novae and Supernovae Recorded in the Annals of China, Korea, and Japan and the their Significance in Radioastronomy’ Acta Astronomic& Sinica (NASA), Vol. 13, No. 1

“The sun on that day was 15 degrees in Taurus and the spectacle in the 15th degree of Scorpio. This spectacle was a large circular body, two and a half to three times as large as Venus. The sky was shining because of its light. The intensity of its light was a little more than a quarter of that of moonlight. It remained where it was and it moved daily with its zodiacal sign until the sun was in sextile with it in Virgo, when it disappeared at once.”

Ali ibn Ridwan (Cairo)

Goldstein, Bernard R. (1965). “Evidence for a Supernova of A.D. 1006″. The Astronomical Journal 70 (1): 105–114


The above image was found in Lupus and dates to 1006AD.

SN 1054 (Crab Nebula)


There are numerous historical accounts of this guest star. What is interesting, if you are European, is that this and all previous supernovae were either unnoticed by our predecessors, or they deemed them unnoteworthy. This guest star was observed for two years, between 4th of July 1054 AD and 6th of April 1056AD in the constellation Tarus. Data from the above remnant matches the date and time of the historical observations.

SN 1181


On the Chi Ssu Day of the 6th month, the 8th year in the Hsium Hsi reign of the Sung dynasty (6th of August 1181AD), a guest star appeared at the Hsui Khuei (Legs, Cassiopeia). It invaded the Tzwan Hse Heing, did not disappear until the Kuei Yu Day of the 1st month the next year, some 185 days later 6th of February 1182).

Xi Ze-xong and Bo Sh-ren (1965) ‘Ancient Novae and Supernovae Recorded in the Annals of China, Korea, and Japan and the their Significance in Radioastronomy’ Acta Astronomic& Sinica (NASA), Vol. 13, No. 1

This remnant was found in Casseopeia and fits the date of 6th of August 1181 to the 6th of February 1182AD.

SN 1572 (Tycho’s Supernova)


This guest star appeared around the time that European astronomers started to treat measurement of the sky seriously and as a precise science. The best measurer of the time, Tycho Brahe, published his observation, and those of others, in a book called ‘De nova et nullius aevi memoria prius visa stella, iam pridem anno à nato Christo 1572, mense Novembri primum conspecta, contemplatio mathematica’ (‘Concerning the New Star, never before seen in the life or memory of anyone…’)

You can see here the image in his book of where the new star was found, in the constellation Cassiopeia sometime between the 2nd-6th of November 1572AD, and a 1881 etching by Camille Flammarion picture of Tycho observing the new star in his book “Astronomie Populaire”:

One of the few cases in the history of physics where the discovery wasn’t named after the first person to find it, but the person who made the best measurements.

The Max Plank Institute for Astronomy, by analyzing light reflected from interstellar dust clouds, have been able to reconstruct what occurred. They measured light, although dimmer than observed from 1572AD, of the original supernovae. Think of a hearing a lightning strike from far away and then hearing it again a short while later, reflected from a distant building. Replace the lightning for the supernovae, the distant building for a dust cloud, and sound for light and you have a good idea of what they were able to do.


The resulting video (which is a computer simulation) is perhaps the first drama documentary of astronomy.


SN 1604 (Kepler’s Supernova)


The astronomer Johannes Kepler made very careful observation of this guest star, as Tycho Brahe did for the previous observation. He drew a very detailed diagram locating it at the foot of the constellation Orphiuchus (marked with “N”), appearing on the 9th of October 1604AD.

 Johannes Kepler (1604) ‘De Stella nova in pede Serpentarii’ (On the New Star in Ophiuchus’s Foot)

Data from the above remnant agrees with the location and date.

SN 1680 (G111.7-2.1) (Cassiopeia A)


This supernova remnant when discovered in the constellation Cassiopeia and dated to around 1680AD. However, there do not seem to be any reports from this time time of guest stars in the direction of Casseopeia.

It has been suggested that this star may have been recorded accidently as a fixed star by John Flamsteed, the first Astronomer Royal. He catalogued over 6000 stars, with exceptionally high fidelity. However, there is no such star ‘3 Cassiopeiae’, as recorded by Flamsteed on August 16, 1680AD in Cassiopeia. Did he perhaps witness the Supernova of the above remnant?

Hughes, DW (1980). “Did Flamsteed see the Cassiopeia A supernova?”. Nature 285 (5761): 132–133


Modern data and analysis gives an estimate that in a galaxy of around 100 billion stars such as our own, one star will explode around every 50 years. Consider this a rare event? You might, if you didn’t know how many galaxies there are. After reading this article, if you find yourself outside on a clear night, hold your hand up to the sky and make a hole the size of 5 pence coin. You have now circled a view that, with a good enough telescope, could see 100,000 galaxies. So, despite a supernova initially seeming a rare event, in that small region of sky, on any given night, around 10 stars explode. And in that small region of sky, on one single night, the same number of of stars will explode as have been observed in all of recorded human history.

The above analysis was adapted from a lecture given by the physicist Lawrence Krauss. He ends the idea with the following conclusion:

‘The universe is huge and old and rare things happen all the time.’

Lawrence Krauss – ‘A Universe From Nothing’

On the scale of the universe, we are very brief, unimaginably small and mostly visionless. It is to be expected that we will draw faulty generalizations from our limited view of things. But we can filter out our incorrect ideas. It is the curious minds that ask questions and guess answers, those minds who, with a scientific inquiry, seek to prove their answers wrong that learn something about the universe.