Comet Nearly Hit Earth? Not So Fast

Phil Plait ("The Bad Astronomer") writes with a skeptical take on the recent report that a comet may have narrowly missed earth. According to the linked post from Plait, "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."

Comments

I want a Good Astronomer

[ArcherB]

Why would I trust the opinion of someone who calls himself "The Bad Astronomer". I want the opinion of a GOOD Astronomer!

It's like wine. How about some fresh wine. And bring me those finger sandwiches you talked me out of!

Re:I want a Good Astronomer

[fph il quozientatore]

It's like wine. How about some fresh wine. And bring me those finger sandwiches you talked me out of!

Hey, we said astronomy, not gastronomy!

Re:I want a Good Astronomer

[Whalou]

Somewhat funny after Google translate:

Astronomy is about comets, gastronomy is about to eat.

Re:I want a Good Astronomer

[delt0r]

I assumed people would get the Joke. Apparently not. The blog is well respected in Astronomy circles and he publishes peer review papers in the field. He is in fact a good Astronomer.

I assume parent knows this... hence the quip about fresh wine.

Re:I want a Good Astronomer

[Anonymous Coward]

The humor part is that in Dutch: "kometen" (comets) sounds the same as "kom eten" (come eat).

A loose translation of the wrong interpretation would be: Astronomy is about coming in to eat, gastronomy is about going out to eat.

That's what I said! (sort of)

[wisebabo]

Ok I wondered why we didn't get HIT by some of the pieces of the comet instead of more people seeing it but then again I'm not an astronomer (good or bad).

Here's my previous post:

While it is not impossible that an extinction level event almost happened, I'd like to see a bit more evidence before panicking.

If this comet was so close, so much so that no other observatory on earth was able to see it due to "parallax", how come not one of the 450 or so pieces impacted the earth? (There are no reports of Tunguska sized impacts).

Also, wouldn't it be relatively easy to figure out where this thing was headed and find out where it is now? Unless it was a (very) long period comet or ended up in the sun, we should be able to track it down. In fact, if it exists, shouldn't it be easy to find as it will likely have an orbit that repeatedly intersects earth's orbit? (Ulp!)

Anyway, some slashdotters who read this post commented that it could be very hard to tell where the pieces could have ended up due to the chaotic influence of the earth's gravity. True but we're talking about something pretty big (a billion tons) that came within a hairs breadth of hitting the earth, you'd think there would be enough information in the observation to plot some of these large objects spewing gas and plumes. Likewise, the very fact that it came within (I think the article said a few hundred kilometers) means that, regardless of orbital inclination, it's orbit DID intersect that of the earth's orbit and presumably sone of the pieces would continue to do so in a very visible fashion (unless it is a long period comet or plunged into the sun!).

But then again I'm not an astronomer so who knows?

Re:That's what I said! (sort of)

[onepoint]

While what you say makes solid sense, I would like to interject that this was a past event during a way different time, when communication were slow.
What might now be occurring is that other observatories are going back to those dates to see if anything was documented. I think people in those days kept log books. OR it could be just that someone played a real good joke on the guy OR maybe validation will come around over the next 20 years or so.

Re:That's what I said! (sort of)

[Pharmboy]

If this comet was so close, so much so that no other observatory on earth was able to see it due to "parallax", how come not one of the 450 or so pieces impacted the earth? (There are no reports of Tunguska sized impacts).

While I agree with your skepticism, considering this was pre-radio era, and that we might have had some impacts on water and just didn't know it. The earth is over 2/3rds water, after all, so odds are always that a meteorite will hit water, not land. There is also the possibility that we were hit with many, many smaller meteorites (smaller than a Hyundai) over mainly water. Or the fact that comets are often made of water ice, so most of what hit the atmosphere either evaporated on the way down or shortly thereafter. If a chunk of water ice had hit the planet anywhere over 100 years ago, odds were certainly in the favor of it hitting either water or uninhabited land.

Yes, we need more evidence, but it does seem worth the time and effort for someone more knowledgeable than you and I to research a bit more. As for the question "Will Earth experience near misses?", the answer is an obvious "yes", since we also get major hits every 130 million years or so, so the idea that this did happen is at least plausible.

Re:That's what I said! (sort of)

[JSBiff]

"While it is not impossible that an extinction level event almost happened, I'd like to see a bit more evidence before panicking."

Why would anybody panic about something which didn't happen in the past? Little bit late for panicking now, wouldn't you say?

meteorites impacting earth daily

[IAR80]

The number of meteorites impacting the earth daily is in the hundreds if not thousands. Most of them are so small that they bun up in the upper atmosphere. On average 2 every day are big enough to make it through the atmosphere and reach earth. If the comet was fragmented into tiny pieces it would not matter.

Phil Plait is not a bad astronomer

[Walter White]

He writes a column debunking "Bad Astronomy."

Re:Shoemaker–Levy 9

[Chris Burke]

Shoemakerâ"Levy 9 didn't look scattered all over the place, pretty much looked like a straight line.

The pieces large enough to be visible from Earth, and where "pretty much" is relative to the size of Jupiter.

If the major remnants of a broken comet had passed that close to earth, then the millions of tiny remnants would have created a meteor shower on earth that would put the Leonids to shame.

Unlikely != Impossible

[mveloso]

Life is apparently extremely unlikely, yet here we are.

How many astronomers do observations during the day today? Roll back 100+ years and the number likely drops tremendously. The guy is staring at the sun! Who does that on a daily basis?