Did a fragmenting comet nearly hit the Earth in 1883? Color me very skeptical

By Phil Plait | October 17, 2011 1:30 pm

A few days ago, three astronomers from Mexico posted a paper online (PDF) claiming that an observation from 1883 indicates a small comet passed within a few thousand kilometers of the Earth’s surface, and perhaps as close as 500km! Had this hit us, we would’ve been hammered by thousands of explosions as powerful as the largest nuclear explosions ever detonated.

The thing is, I’m not buying it. While superficially the interpretation fits the observations, there are way too many problems with it.

Here’s the deal. During the days of August 12 – 13, 1883, a Mexican astronomer named Jose A. y Bonilla reported seeing hundreds of objects passing directly in front of the Sun. They were small, appeared fuzzy, and left behind a misty appearance. In total, Bonilla says he saw 447 such objects!

The authors of this new work claim that what Bonilla may have seen was the remnants of a small comet that had previously fragmented. We’ve seen comets do this, and in fact it’s somewhat common. In 2006, Hubble took the picture shown above of the comet 73P/Schwassmann-Wachmann 3, which had recently disintegrated. So that part isn’t too far-fetched. However, once you make that assumption, things get pretty dicey.

The authors use the observations by Bonilla to estimate the distance and size of the comet fragments. Bonilla observed these objects at an observatory in Zacatecas, Mexico, but they were not seen transiting the Sun by any other observatories anywhere else. This can be used to narrow down their location; it means they must have been close to Earth. Had they been far away then other observatories would have seen them moving across the Sun. It’s like a bird flying by just outside your window; someone looking out a different window wouldn’t have seen it, but a bird a few hundred meters away would be visible to both.

Doing some simple math, the authors calculate the comet fragments were no closer than about 500 km (300 miles) from the Earth’s surface, and no farther than about 65,000 km (40,000 miles).

This right there is enough for me to be extremely skeptical of this idea. When a comet breaks up, it spreads out. Even when intact, the material surrounding a comet can be tens or even hundreds of thousands of kilometers across! Claiming that a comet broke apart, yet managed to constrain its pieces to volume of space less than a few thousand kilometers across strains credulity.

Mind you, Bonilla claimed to have seen these objects over the course of two days. That means they would’ve been stretched out along a path that was a million km long at least, yet so narrow that only one observatory on Earth saw them transit the Sun. That is highly unlikely.

Worse, the very fact that no one else saw anything makes this claim even less tenable. A comet, even one that’s broken up, can be very bright, and the closer it is to us the brighter it can be. I have personally seen a comet in broad daylight! Even if this purported comet couldn’t be seen during the day for some reason, at some point in the days or weeks before or after these observations, the comet should have been visible in the evening sky (or at least at dusk or dawn). Yet no one saw anything.

Worse than that, there were no meteor showers reported that day or night. Comets are basically giant snowballs peppered with dust and gravel. Every time they get near the Sun, some of that ice sublimates (turns from a solid into a gas), forming the fuzzy ball we associate with comets, but also releasing some of the embedded rocky material. When the Earth passes through this stuff, we get meteor showers as it burns up in our atmosphere.

A comet passing a few thousand klicks from the Earth would have generated a lot of meteors. It’s practically impossible for me to believe that one could get that close to us and not even be noticed, and not create a meteor shower that would have been practically biblical in size*.

It’s not like there wouldn’t have been ammo for such a meteor shower. The authors of the new study calculate the sizes of the fragments given their distance and the size Bonilla reported. They find the fragments would have been a few dozen meters across to as large as a kilometer. If there were hundreds of objects this size, there would’ve been millions as small a few centimeters across. Objects that size make brilliant fireballs as they burn up in our atmosphere, and would’ve been visible during the day, even with the Sun shining. Again, no reports of any meteor storms, despite a comet being a few thousand kilometers away and a million kilometers long.

Also, the Earth is moving, and covers a lot of ground (OK, space) in a day. Having the Earth move at least 2.5 million km during that time, and never getting closer or farther than 500 – 65,000 km is too much to ask.

Let me be clear: I’m not casting doubt on Bonilla himself; it’s perfectly reasonable to think he saw something. But there are a lot of other things he might’ve seen; flocks of birds for example, or an odd atmospheric phenomenon (there are a few volcanoes in that area, which is interesting). While on the surface the explanation of a fragmented comet appears to fit the observations, in reality there are just too many basic problems with this interpretation. It’s clever, and interesting, but there are simply too many flaws in the idea for me to think it’s correct.

Image credit: NASA, ESA, H. Weaver (APL/JHU), M. Mutchler and Z. Levay (STScI)

* I’ll note that later that year, in November, there was a huge meteor shower: the annual Leonids shower, which usually generates a few dozen to a hundred meteors per hour, stormed down thousands of meteors per hour! But that is a well-known and now well-understood phenomenon, and is known to be associated with an intact comet named Tempel-Tuttle. This purported fragmenting comet event was a full three months earlier, when the Earth was millions of kilometers away from the orbit of that comet. They are certainly unrelated.

Related posts:

Comet McNaught: daytime comet!
New meteor shower points to a future close encounter
Ten Things You Don’t Know About Comets
Leonid meteors tonight!

CATEGORIZED UNDER: Astronomy, Debunking, Science, Skepticism
MORE ABOUT: comet, doomsday, Leonids, meteors

Comments (62)

  1. Kevin

    Or maybe it was….OMG ALIENS!!!111

    Seriously, though, I found this post pretty interesting. The comet idea is neat, but very unlikely. I do wonder what it was that Bonilla saw, though. Probably just a flock of birds.

  2. chris j.

    wikipedia sez it wus geese. do the paper’s authors try to discredit the avian explanation?

  3. Krakatoa was erupting at the time (island-destroying final phase was still 2 weeks off). Ash in the tropical air?

  4. I’m amazed at just how much this story took off. It looks like I was the one to break it over at UT, but now it’s everywhere. I was careful to end my article with a skeptical analysis, also noting the distinct lack of meteors, but the vast majority of other websites I see reporting it now don’t include that. Instead, I see them reporting it as solid fact; “The day the Earth almost ended.”

  5. Christopher Jablonski

    It’s amazing when different lines of evidence converge towards the same conclusion. For example, the paper is written in Comic Sans.

  6. Christopher (4): I was wondering who’d be the first to mention that.

    I actually like comic sans. Unashamedly.

  7. Chris

    Fuzzy objects in front of the sun, sounds like a spider web in the telescope, maybe caught some bugs.

    Another thing in the paper, they also use the spreadsheet notation (“E+09”) in one table. I keep telling my students, if you put that in a paper you submit the reviewers are not going to be happy with you.

  8. Jared Schlechte

    Thanks for doing a follow up article on this! I was rather skeptical when I first read about it.

  9. Camilo Ramos

    Some postulate that maybe Bonilla mishandled a bunch of wet collodion plates and made up the report to cover the mistake.
    Anyway, the mere possibility of it gave me some chills. It reminded me of the alternate world steampunk novel ¨The Lancers of Peshawar¨, in which a meteor shower anihilates North America, Europe and Russia in 1878. The survivors of England escape to India, South Africa and Australia to rebuild the Empire.
    BTW, there was also a story in UT (Meteor Shower Points Towards Undiscovered Earthbound Comet) and I don’t think it received much attention, at least not from UT patrons.
    Oh, and about Comic Sans in research papers, well, maybe the writers forgot to put on their reading glasses when writing the final paper?’ 😉

  10. MadScientist

    At the claimed distance, imagine how quickly those comet fragments would appear to move. Maybe it was Xenu’s fleet. Come to think of it – with a claimed observed transit of the sun (approx. 0.5 degrees on a diameter), the claimed distance, and even a low estimate of the speed of a comet, the guy would have to have been a human high-speed camera to observe anything. The claims in the paper have got to be bogus (it’s no wonder it’s not in a science journal).

  11. Renee Marie Jones

    Next thing you’re gonna tell us is that Giovanni Schiaparelli didn’t really see canals on Mars! :-)

  12. QuietDesperation

    Next thing you’re gonna tell us is that Giovanni Schiaparelli didn’t really see canals on Mars!

    Or that Comet Biela didn’t cause the Great Chicago Fire.

    That’s my favorite “out there” theory of all time because there’s actually some interesting evidence. Some astronomers of the time even predicted a very near miss or even a hit based on their orbital calculations.

  13. QuietDesperation

    Fuzzy objects in front of the sun, sounds like a spider web in the telescope, maybe caught some bugs.

    Wasn’t there another astronomer who saw insectoid shapes pass in front of the Sun, and then days later there was a locust invasion somewhere. It was a famous astronomer. Maybe Herschel?

  14. peter sheehan

    Would a comet the size of Halley’s comet have been visible for months before it approached Earth?

  15. Camilo Ramos


    >> Wasn’t there another astronomer who saw insectoid shapes pass in front of the Sun

    I remember something like this from a Pink Panther episode.

  16. Tim G

    In the past few years some researchers have hypothesized that a “multi-kilometer sized icy body” caused a mass extinction in North America some 13000 years ago. I cannot remember how frequently an impact of such magnitude would occur on Earth but it could be as rare as once in about ten million years. So this is a rather audacious hypothesis.

    There is also a popular idea that a comet impacting the Indian Ocean circa 2800 BC caused a megatsunami and is the reason for dozens of flood myths. The magnitude of this purported impact is also believed to be very rare.

  17. Chrysoprace

    Hey Phil, just read an article about titanium deposits on the moon with pretty pictures, seemed like BA material.

  18. In 2006, Hubble took the picture shown above of the comet 73P/Schwassmann-Wachmann 3, which had recently disintegrated.

    I spent many mornings making detailed sketches of that comet’s journey through our neck of the woods. Then, this silly girl stole my notebook??? Why would someone do that? Anyway, the police were no help, and it was lost.

  19. Its good to see that scientist from my country are doign science, saddly, today they’re wrong.

  20. Keith Bowden

    You like Comic Sans, Phil? My opinion of you just went even higher. :)

  21. Ben H.

    The fact that the paper is written in comic sans alone makes their argument untenable, even if it would be otherwise defensible.

  22. Jim

    No – we weren’t in any danger. Nor was it aliens! After all, any dangerous comet would have been blasted to harmless bits (like the nuke warheads) specifically by the aliens that created us. [No inflammable statements there]. :) :)

  23. Randy Owens

    I think I see a Bad Font Schism in our future.

  24. Re Comic Sans, everything has its niche. It might be appropriate for, say, the large text on the more whimsical sort of birthday card, maybe. But using it for body text is indeed a heresy, and rightly so.

  25. stevesliva

    Sounds pretty close to the maximum of solar cycle 12, too.

  26. During my freshman year as a budding historian at the National Uni of Mexico I wrote a paper on the early years of modern astronomy in Mexico. Never heard of Bonilla, but I can certainly attest that astronomy in this country at the time was all but professional. It wasn’t until well after the Mexican Revolution, in the late 20s, early 30s, that professional astronomers took over from what was then a sort of quirky gentlemen’s club, who were in charge of the (then) National Observatory in Mexico City, which was located in the (then) outlying township of Tacubaya (today a major choke point for buses, metro and cars), and hence the network of provincial observatories, to which Zacatecas belonged.

    The point is, astronomical observations and measurements were anything but reliable even in the capital city. I cannot imagine what they might have been like in a far flung province like Zacatecas.

    More interestingly, perhaps, is that Bonilla also had connections to Flammarion and the Société Astronomique de France. I say also because, at the time, French connnections were seen as indispensable to upper crust types with a flair for exotica like big telescopes, and Flammarion’s wild speculations about Spiritism and alien contact had rather a large following amongst the early astronomical community in Mexico – the most notorious of whom was Joaquin Gallo, who wrote up rather less than solid papers for L’Astronomie and brandished Flammarion’s name around as proof of his authority in matters astronomical.

    All of the above might provide some relevant background context for the kind of community that Bonilla belonged to.

  27. DennyMo

    Salul, thanks for the background info. Context like this is very useful.

  28. In their paper, the authors also claim it were fragments of comet 12P/Pons-Brooks.
    Which makes no sense at all, as a (not so) close approach to the orbit of this comet does not happen at August 12, but at December 6: therefore it is impossible that a close approach of “comet fragments” on August 12, 1883 would have been fragments of Pons-Brooks as the authors propose….
    (see also diagrams at http://sattrackcam.blogspot.com/2011/10/ot-1883-zacatecas-observation-of.html )
    That December 6 approach is not particularly close either by the way: MOID 0.2 AU, the comet orbit passes closer to the orbit of Venus than to that of the Earth. So I am at a total loss as to understand how they came up with 12P/Pons-Brooks as the origin of these “comet fragments”. It really suggests, together with what Phil writes above, that these guys have no clue about orbits, celestial mechanics, and what is realistic.

  29. Ryan Rife

    Shoemaker–Levy 9 seems to go against your theory that it would have to be scattered everywhere.

  30. Related only because it involves an unexpected transit, but it was so cool I have to share it. A couple of weeks ago when the moon was in 1st quarter, I got out my little telescope (which I had not done in over a year) and was looking at the craters and mountains near the southern terminator around 11:00pm local, when a satellite transited right across the fattest part of the visible moon. By the time I realized what I was seeing, it had already passed — less than a heartbeat for the whole thing — but it was a perfectly clear silhouette with a large middle body and two solar panels. Really neat, unplanned, once in a lifetime experience.

    I can’t imaging what this astronomer must have experienced. But it must have been cool.

  31. DarkEnergy

    It is interesting to read the original paper and in particular see the image of the Sun showing the transit of one of the “corpuscules”. It is huge, about 4×2 arcminutes and, looks like a bat?


  32. DarkEnergy

    It is interesting to read the original paper and in particular see the image of the Sun showing the transit of one of the “corpuscules”. It is huge, about 4×2 arcminutes and, looks like a bat?


  33. Stevez

    Only one telescope on Earth happened to be watching the Sun.

    In daytime.

    In 1883, before the age of telephones, computers, radar, or astrophotography. Um yeah, that’s actually not unbelievable at all.

    I think the point of the theorists is that the comet broke up as a result of EARTH’S gravity as it narrowly missed the planet and was observed immediately after closest approach, which I find at least plausible.

    When objects in space spread out after breaking up, it’s true they spread out across a very long trail. EVENTUALLY. But not “instantly”.

    I’m skeptical at their conclusion that it was a previously observed comet though, which was already known not to have a closest approach to Earth until several more months after the observation took place. Seems much more likely to me that, if a comet, it may have been a previously unknown one.

  34. Torbjorn Larsson, OM

    The wet collodion process used at the time was known for its many defect sources in its many critical manual steps.

    I have seen what is claimed to be one of Bonilla’s plates, and the fuzzy streak correlates with the upper left-lower right diagonal. This is exactly the pour direction that a right handed individual would use in the standard pour back of excess collodion into the bottle as illustrated on historical sites.

    Perhaps Bonilla didn’t even take the time to observe the sun by eyeball (say through sooted glass). He may have made up an a posteriori just so story to explain his results, whether unwittingly or to cover for problems with 2 days hard and (I think) expensive work.

    This is a testable hypothesis if one has access to enough raw photos or copies, you don’t even need to know Bonilla’s handedness to invalidate it if wrong.

    The comet idea didn’t look testable, but it seems BA made a good argument for why it is invalid. But before that, I would say that it looks suspiciously like the standard fare of untestable unscientific archaeoastronomy. Comic sans suits perfectly for that!

  35. Ian S

    @14 Peter,
    Halley’s comet is now observable throughout its entire 70 odd year orbit using current large telescopes so yes it would be visible several months out.. However back in the 1800s they didn’t have continuous all sky surveys or the Hubble space telescope so it is conceivable that a comet could escape detection until much closer but a comet, even a fragmented one passing that close to the earth would be very obvious, bright and huge to the naked eye for many days if not weeks.

  36. Jason Goemaat

    I like how they mention the objects were surrounded by a mist and left a misty trace. Is that how comets would look? The solar wind normally points the tail away from the sun independent of the direction of motion, which means straight towards the observer. What would the effect be inside the Earth’s magnetic field? Wouldn’t the ionized particles that make up the coma be stripped by our magnetic field?

  37. JEFF

    FONT IS GEORGIA! not comic sans….. retards lol

  38. Old Geezer

    If they really weren’t comet fragments maybe they should have used Comet Sans.

  39. Peter B

    Stevez @ #37 said: “I think the point of the theorists is that the comet broke up as a result of EARTH’S gravity as it narrowly missed the planet and was observed immediately after closest approach, which I find at least plausible. When objects in space spread out after breaking up, it’s true they spread out across a very long trail. EVENTUALLY. But not “instantly”.”

    I think the BA’s problem is that the astronomers’ article requires the comet fragments to disperse greatly in one dimension only.

  40. Dan Arles

    Could it have been sunspots??

  41. George William Herbert

    SL9 was broken apart by a much more severe gravitational tidal environment, Jupiter’s gravity well. The Earth doesn’t have enough tidal force to do that much damage, per se.

    The more significant factor is that even if it breaks up into a linear arc, then there will be outgassing and fragments spread off to the sides. Phil’s generalizing a lot, but the basics (that even at 60k km away, you’d get hit by a lot of cm scale pebbles) are pretty hard to refute. Comets are not point sources, they’re clouds of debris around a main reservoir object. The cloud is not one-dimensional, it’s spreading out in all directions.

    There would have to have been meteor activity along with something like this…

  42. Mark Hansen

    Jeff, did you check the font settings of the document? 4 are listed, Comic Sans among them, and not one was Georgia. Care to retract your retards statement?

  43. reidh

    It didn’t hit, no one can prove anything. Its just Bull Crop.

  44. Nigel Depledge

    Jeff (43) said:

    retards lol

    Do they?

  45. Nigel Depledge

    Jeff (43) said:

    FONT IS GEORGIA! not comic sans

    Georgia is a serifed font. The paper is most certainly in a sans serif font, and Comic Sans seems at least pretty close, and certainly a far better match than Georgia.

    Perhaps you should have checked your claim before you called anyone a retard.

  46. Puppetmistress
  47. John

    Dos it have something to do with these observations that Krakatoa volcano erupted in very same year 1883? Would it be that some material was blown out from Krakatau to higher hemisphere that might explain these visual observations?

  48. Another possibility: the “transiting objects” observed could have been the early autumn seasonal migration of Monarch butterflies. The timing is about right, and the Zacatecas Observatory lies right along the migration path.

  49. Well the first thing thats fishy is its 1883 who knows what really happened? No one does, 1883 were there telescopes? Not like todays they were made out of glass lenses that magnified the image, so he could of saw a number of different things. For all we know they could of seen god and everyone would believe him. In short People are stupid and ignorant, and not to mention very closed minded but if you look at alignments of Comet elenin the earth and surronding planets, It could be just luck but damn, I hope it 2012 happens cause people need to pull their heads out of their A** and start working together to fix not the U.S (because soon China WILL own us) but the world cause it will start a domino theroy of countires going bankrupt and losing control but just a thought… Love you guys! -Jonathan Jones


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