Billion-Ton Comet May Have Missed Earth by a Few Hundred Kilometers in 1883

http://www.technologyreview.com/view/425780/billion-ton-comet-may-have-missed-earth-by-a-few-hundred-kilometers-in-1883/

by gnosis • 14 years ago

109 60 14 years ago

technologyreview.com

dmix• 14 years ago

> They point out that nobody else on the planet seems to have seen this comet passing in front of the Sun, even though the nearest observatories in those days were just a few hundred kilometers away.

This is 1883 and noone else recorded seeing it? Even in all of mexico?

Gustomaximus• 14 years ago

The do say in the article about no-one seeing it;

"That can be explained using parallax. If the fragments were close to Earth, parallax would have ensured that they would not have been in line with the Sun even for observers nearby. And since Mexico is at the same latitude as the Sahara, northern India and south-east Asia, it's not hard to imagine that nobody else was looking."

Is this realistic? Also would the time of day matter? If the sun was low to the horizon etc.

lutusp3• 14 years ago

> The do say in the article about no-one seeing it; "That can be explained using parallax ..."

> Is this realistic?

No. Even today not many observatories specialize in sun observations. It's not at all surprising that only one astronomer witnessed this, and it's a stretch to suggest the explanation that the observed object was therefore very close -- there are many more plausible explanations.

> Also would the time of day matter?

No, not for an object silhouetted against the sun. Consider this year's Venus transit -- everyone who could see the sun at the appointed time, also could see the transit.

venus• 14 years ago

> A sobering thought.

An even more sobering thought is that even in the present day, if we detected something like that heading our way, there'd be absolutely nothing we could but sit and wait for it to arrive.

Shank• 14 years ago

This is slightly true, though notably the Torino Scale mentions that once an object is classed at level 5, governments may begin to take action to counteract such a collision before it arrives at earth, if the encounter is set to be less than a decade away.

http://en.wikipedia.org/wiki/Torino_Scale

Edit: NASA's JPL maintains the Sentry Risk Table, which tracks all objects that may impact the Earth, with various data points about said objects.

http://neo.jpl.nasa.gov/risk/

gnosis2• 14 years ago

The time to initiate an asteroid defense project is long before a threat is even detected.

There needs to be time for technology development, deployment, and testing. Tackling an extinction-level event is not something we want to scramble for at the last possible minute, using untried technology.

rorrr2• 14 years ago

That's not true. If we knew for a fact that it would cause global extinction, we would throw everything at it.

We could blow it up with nukes.

We could put a relatively heavy space probe next to it and deflect its course.

jacquesm3• 14 years ago

It's not Hollywood, it's ballistics.

rizzom50003• 14 years ago

When faced with impending doom, optimism and pessimism are both equally fine sentiments. The caveat is that only one of them accurately reflects reality, not that it matters at that point.

I also suppose that industriousness would be helpful for taking one's mind away from the reality of that impending doom.

But hell, nukes to deflect a comet? Sure, we may as well try it -- but I only suggest doing this if we are 100% certain that the comet will both hit us and destroy us. We could conceivably cause our own extinction via a false positive provided by some faulty monitoring device - wait, did that already happen? Nevermind.

JoeAltmaier• 14 years ago

Um, global melting is happening, and squat is being done about it. I wish I could be as optimistic as you. Maybe because a comet is a thing, a tangible menace, we would emotionally respond.

StuieK• 14 years ago

Here is a very early draft of a list of options I've been working on for deflecting asteroids.

http://slant.co/topics/what-is-the-best-way-to-stop-an-aster...

mserdarsanli• 14 years ago

Well, there are actually people working to save the Earth literally. http://b612foundation.org/

mapt• 14 years ago

The big stuff? Sure.

Smaller stuff, from maybe 10kt up to 1Gt (Tunguska was ~15 Mt), though, we can reliably predict its course and evacuate the affected area.

To detect the small stuff at close range, of course, you need to be able to detect the big stuff a ways off. The problem is that massive star surveys are essentially a brand-new thing now that we have Big Data capabilities (we still get a substantial amount of info from scanner photographic plates of the last century). The astronomical community has mostly been focused on producing expensive 1-2 unit runs of a brand new design every decade, each much bigger and better than the last. Survey telescopy, however, is perfectly amenable to economies of scale in large numbers of small scopes, and to the data from a single-purpose survey being used for dozens of different scientific goals.

http://www.fallingstar.com/ , the ATLAS project, is a minimum viable project for this purpose, using small COTS telescopes & sensors to scan the sky rapidly & systematically for objects that have photometric characteristics of something that is headed our way, a few days or a few weeks from Earth.

I see no reason why we shouldn't build twenty of those, scattered around the world, just for immediate situational awareness. We could initiate the project and have it done in six months.

On a longer-term basis, I think rather than constructing things like LSST under the old paradigm, we should be focusing on smaller, 1-2m telescopes (like PAN-STARRS, albeit perhaps without the extraordinary sensors) in very large, economical quantities. Mechanizing the production line is something that's only really been done for much smaller telescopes.

When you have a large, distributed array of automated telescopes, you can sweep the sky quickly and resiliently to weather conditions, or you can turn a portion on a single target that needs a higher signal to noise ratio, for confirming observations, and perform like a much larger telescope's light-gathering ability.

Lastly, there are projects like the Gaia mission that are doing space photometry. While extremely data-starved (better space communications via radio relays & lasers really needs to get here), Gaia would be in an ideal position to detect all the Earth-crossing NEOs that we can't realistically see from the ground due to the sun's glare... if it was at Venus L2 rather than Earth L2, and ideally if there were half a dozen of them instead of one.

The longer out we see it, the better we can deflect it - and our predictive abilities are in the hundreds of years range if we actually bother to spend the money on detection as if it were as important as space toilets on the ISS. The tech is here.

temphn• 14 years ago

No photographic evidence. No corresponding accounts. No raw data.

  Bonilla published his account of this event in a French 
  journal called L'Astronomie in 1886. Unable to account for 
  the phenomenon, the editor of the journal suggested, 
  rather incredulously, that it must have been caused by 
  birds, insects or dust passing front of the Bonilla's 
  telescope.

As the saying goes: when you hear hoof-steps, think horses, not zebras.

mistercow2• 14 years ago

Yeah the prior probability of "fragmenting comet within 8000 km of Earth" seems kind of a lot lower than that of "dust in front of the telescope".

quarterto• 14 years ago

http://rationalwiki.org/wiki/Improbable_things_happen

danso• 14 years ago

I had never heard that saying before but I fear I will use it much too often in the future

ars• 14 years ago

It's from this: http://en.wikipedia.org/wiki/Zebra_%28medicine%29

apaprocki2• 14 years ago

The original article has all of the exact observations as well as a diagram and photograph.

mchouza• 14 years ago

A more skeptical analysis by Phil Plait: http://blogs.discovermagazine.com/badastronomy/2011/10/17/di...

ChuckMcM2• 14 years ago

Was going to add this one as well. A comet of that size, that close, would have raised questions in other places. The point that we didn't have nearly the observational capacity a couple of hundred years ago that we have today is well made, we certainly might have dodged a bullet, we have seen two comments hit the bigger planets (Jupiter and Saturn) but we only noticed because we were looking.

So I share the skepticism that this was a Comet in 1883 but I don't doubt for a moment comets have come that close to the planet.

jacquesm3• 14 years ago

They got a lot closer than that in recent times, but not quite as massive:

http://en.wikipedia.org/wiki/Tunguska_event

In the long run cometary impact is pretty much a certainty and close passes are a lot more likely than impact.

So even if this particular observation is probably attributable to something else there is a good chance that something like it did happen at another point in time in the last 2,000 years or so.

http://en.wikipedia.org/wiki/Chicxulub_crater was 65M years ago, http://en.wikipedia.org/wiki/Sudbury_Basin 1.9B years ago, http://en.wikipedia.org/wiki/Vredefort_crater 2B years and so on. The http://www.passc.net/EarthImpactDatabase/index.html Earth Impact Database holds currently 183 recorded impacts over a period of about 2.4 billion years.

2400M / 183 gives a probability of 7.6x10-8, but that's for impacts, and near misses don't leave any evidence other than people that happened to be looking in that direction. The question then is how many near misses before you get a 'hit', probably a fairly large number depending on how you classify a near miss. Anything closer than the earth moon orbit would be fine with me as a 'near miss' (according to George Carlin an accident is a near miss, but never mind that). The exposed target of the earth-moon bounded sphere is substantially larger (~2000 times or so?) and would increase the chance of a near miss from the impact figure to about 0.000167 for any given year, or about once every 6,000 years. And the base figure here is craters that we know about, which means they're likely on the land, that misses 2/3rd of the planet.

I'm sceptical about this but I would not rule it out entirely.

TimJRobinson• 14 years ago

I'm confused as to why this is coming up now, did they find some new evidence or residual rock from this comet? If not how do they now know that it was actually a comet and not simply a mistake on the astronomers part as they previously thought it was?

lutusp3• 14 years ago

> ... how do they now know that it was actually a comet and not simply a mistake on the astronomers part as they previously thought it was?

They don't. The linked article assumes the veracity of the original account, it doesn't introduce anything new.

polarcuke• 14 years ago

Well if this is true I guess there is one more thing for us to be thankful for today!

Geee2• 14 years ago

It doesn't matter because we wouldn't be here thinking about it. On the other hand, the extinction event would have been a gold mine for the future archaeologists that would have evolved on Earth in the next 100 million years.

monochromatic3• 14 years ago

You're right, let's NOT be thankful that we're still here.

lutusp3• 14 years ago

A quote: "They point out that nobody else on the planet seems to have seen this comet passing in front of the Sun, even though the nearest observatories in those days were just a few hundred kilometers away. That can be explained using parallax."

It can also be explained by the simple fact that (a) not many observatories specialize in observing the sun even now, and (b) the observation may only have lasted a few hours (as with this year's Venus transit). Remember Occam's razor -- the simplest explanation is to be preferred.

pgsandstrom• 14 years ago

The paper in question: http://arxiv.org/ftp/arxiv/papers/1110/1110.2798.pdf

It is written in comic sans and one of the authors is using a yahoo mail. Maybe I'm just being an elitist nerd, but really...

monochromatic3• 14 years ago

That does not look like Comic Sans. Maybe just some weirdness with font rendering on an iPad though...

tolos• 14 years ago

Hector Javier Durand-Manterola is the author with the yahoo address. It looks like he did work at Universidad Nacional Autónoma de México (UNAM), where the other two authors are from, at one point [1]. He's authored a few other astronomy papers at arxiv [2] even though he doesn't seem to be in the database. Perhaps he has retired from academic life.

[1] http://www.researchgate.net/profile/Hector_Durand-Manterola/

[2] https://www.google.com/#q=site:arxiv.org+hdurand_manterola%4...

VMG• 14 years ago

Anthropic principle? If it had hit we wouldn't be talking about it.

apaprocki2• 14 years ago

The link to the original L'Astronomie journal article, which contains a diagram and photograph is here:

http://books.google.com/books?id=Vt1NAAAAMAAJ&pg=PA347#v...

"PASSAGE SUR LE DISQUE SOLAIRE" p. 347, L'Astronomie Vol. IV

Transcript (French) https://gist.github.com/4136038

Transcript (English, Google Translated) https://gist.github.com/4136045

Also, it appears there are letters to the journal regarding the original article in the subsequent Vol. V, which can be viewed here: http://hdl.handle.net/2027/mdp.39015069401779?urlappend=%3Bs...

SpikeDad• 14 years ago

Is there a remedial school for headline writers? Naturally it missed the Earth or we wouldn't be here. Perhaps the headline writer meant - "Billion-Ton commet MISSED Earth by perhaps a few hundred kilometers in 1883".

To quote George Carlin - "It's not a near miss. A collision is a near miss. It's a near HIT!"

Billion-Ton Comet May Have Missed Earth by a Few Hundred Kilometers in 1883

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