You didn't see that big fireball in December? Neither did astronomers.
March 19, 2019 1:27 AM   Subscribe

It was only the third biggest bolide to enter Earth’s atmosphere on record, so astronomers can be forgiven for missing it at the time. Now, after sifting through data obtained from monitors meant to detect illicit nuclear detonations, a Canadian scientist has determined that a meteor approximately 10-14 meters (33-46 feet) in diameter streaking over Kamchatka, Siberia on the 18th of December 2018 at about 11:48 AM local time exploded over the Bering Sea with the energy of about 173 kilotons of TNT. And it turns out we also have pictures.

Because the object approached Earth from the sunward side, ground-based telescopes didn't see it coming -- and wouldn't have spotted it even if it had been much larger. Months later Peter Brown, professor of astronomy and physics at Western University in Ontario, was examining low-frequency sound data collected by a world-wide network of infrasound monitors deployed by the Comprehensive Test-Ban-Treaty Organization, an international body that verifies compliance with the ban on nuclear tests. The data showed an unusually large explosion had occurred over the Bering Sea in December. The CTBTO hadn't announced it because they'd quickly determined it wasn't nuclear.

To be fair, NASA's Planetary Defense Officer Lindley Johnson (that is his real title) was informed about the fireball a few weeks ago by the US military. But even he was late in hearing about it. Because of its sensitive location, relatively close to both Russia and North Korea, information about the explosion was slow to come out until it had been determined to be a natural occurrence.

After Professor Brown publicized his findings, researchers were able to go back and look for satellite images that may have captured the event. It turned out Himawari 8, a Japanese weather satellite, had the goods, capturing images of a smoke trail and the track of the fireball.

Now that the airburst has been verified, it's been listed in official databases of fireball events and entered into the record books as the the largest in history behind the Tunguska event of 1908 and the Chelyabinsk meteor of 2013 [previously on Metafilter]. Given the number of such objects in our solar system, airbursts of the magnitude of the Bering Sea event can be expected roughly once per decade. It's only recently that we have the means to detect them when they occur over such unpopulated regions.
posted by theory (23 comments total) 33 users marked this as a favorite
The fact that an explosion eight times as energetic as that of the most devastating bomb ever deployed in wartime barely registers on those satellite images really puts the scale of our planetary home into perspective.
posted by flabdablet at 4:06 AM on March 19, 2019 [10 favorites]

So what kind of snacks does one bring to a superbolide party?
posted by escape from the potato planet at 4:12 AM on March 19, 2019 [2 favorites]

Pop Rocks.
posted by seanmpuckett at 4:56 AM on March 19, 2019 [33 favorites]

We actually have the technology to properly watch for these kinds of objects, but doing it in practice is a bit of a logistical nightmare. A constellation of hundreds of cheap, tiny cubesats in orbit armed with commercial IR/Visual sensors could stare continuously at the entire sky to spot the occasional glint of light or the telltale wink of a star as a rock floats past, and it would be reasonably cheap to make. The problem is the unsexy parts of the operation, the vast amount of video data that fleet of satellites would create, possibly dwarfing everything else in orbit. It can't use conventional video compression like Youtube because the image artefacts those techniques introduce would hide the tiny signal of a faint asteroid. And then you have the small issue of simultaneously processing hundreds of real time video feeds, with low enough latency to give people a half-hour warning to hide in their basement and away from any windows. Oh, and who's going to pay for it?

So yeah, we're probably waiting until one of these bolts from the blue eventually hits a populated area, and it's kind of frustrating. The technology problems are probably solvable with enough funding, but no-one is likely to be interested in lumps of rock millions of kilometers away until they literally fall on their heads.
posted by Eleven at 6:37 AM on March 19, 2019 [3 favorites]

Minor point of order: It's second largest if you go by NASA's list, which starts in 1988 or fourth/fifth if you include the much patchier records for the rest of the 20th Century. Besides Tunguska and Chelyabinsk, there was a 190kt bolide over Spain December 8th, 1932 and one in the extreme southern Indian Ocean of 170-350kt August 3rd, 1963.

Which only emphasizes the point that these things are not rare and so correspondingly more dangerous. One every 30-40 years should be expected, probably more now that we're really looking for them. I do wonder how many times one went off over some populated area in Antiquity. There's a suspicion of one over Gansu Province in China in 1490.

(This is also a good time to link to my favorite YouTube video, the footage over the Great Daylight Fireball of 1972 over Wyoming. These things fascinate me.)
posted by Quindar Beep at 6:48 AM on March 19, 2019 [4 favorites]

Why do all the big ones head for Russia? It just seems...weird.
posted by Morpeth at 6:57 AM on March 19, 2019 [1 favorite]

No military, fishing or shipping vessels in the area?
posted by sammyo at 6:58 AM on March 19, 2019 [1 favorite]

Why do all the big ones head for Russia? It just seems...weird.

There’s a whole bunch of there there.
posted by Celsius1414 at 7:07 AM on March 19, 2019 [23 favorites]

No military, fishing or shipping vessels in the area?
I was thinking that too, but there probably aren't a ton of shipping vessels in that part of the ocean, fishing vessels (save for the Deadliest Catch, who may or may not still be filming up there) probably don't have much in the way of cameras on board, and any military units in the area probably aren't inclined to share footage if they have it. Also, looks from those images like there was a big storm in the area, so visibility was probably bad anyway. The Bering Sea and Siberia are remarkably remote.

This is very cool and I'm sad that it's probably going to go unnoticed by mainstream news because of everything terrible in the world. Those satellite images look so much like BSG CGI and I love it.
posted by neonrev at 7:25 AM on March 19, 2019

Why do all the big ones head for Russia? It just seems...weird.

Do you know how many time zones there are in the Soviet Union?


It's ridiculous.
posted by escape from the potato planet at 8:34 AM on March 19, 2019 [6 favorites]

A constellation of hundreds of cheap, tiny cubesats in orbit armed with commercial IR/Visual sensors could stare continuously at the entire sky to spot the occasional glint of light or the telltale wink of a star as a rock floats past

The GPS constellation (Navstar) does this; in addition to providing navigation services, each GPS satellite also has a nuclear detonation sensor. They're called, humorously, bhangmeters. They're designed to look for a very distinct double-flash produced by atmospheric nuclear detonations. My guess is there are other sensors designed to look for exoatmospheric detonations as well, although there's not a lot of information published on their exact capabilities (imagine that).

The predecessor system, Vela, had a variety of sensors and gets credited with (accidentally) observing the first gamma-ray burst. They are also the subject of an intriguing conspiracy theory, if you're into such things.
posted by Kadin2048 at 8:43 AM on March 19, 2019 [4 favorites]

Russia is really really big.
posted by dazed_one at 9:44 AM on March 19, 2019 [1 favorite]

This is awesome. I'm going to get hold of this Peter Brown person and make him tell me everything.
posted by BlackLeotardFront at 9:45 AM on March 19, 2019 [1 favorite]

Don't you all have an HSN-1000 in your parts bin somewhere?
posted by JoeZydeco at 12:26 PM on March 19, 2019 [3 favorites]

I wonder how many city destroying sized impacts have occurred in the southern ocean and emptier stretches of the pacific?
posted by sammyo at 12:30 PM on March 19, 2019

Well, something took out Lemuria.
posted by Rumple at 12:49 PM on March 19, 2019 [3 favorites]

The delay in informing Planetary Defense Officer Lindley Johnson is... disturbing.
Also, a good kernel for a story.
posted by doctornemo at 4:14 PM on March 19, 2019 [1 favorite]

"Goodness gracious, great balls of fire!"
Jerry Lee Lewis
I always thought of him more as a musician, than an astronomer.
posted by Oyéah at 5:16 PM on March 19, 2019 [1 favorite]

> Don't you all have an HSN-1000

From the datasheet: "Maxwell Technologies’ liability shall be limited to replacement of defective parts."

Good luck claiming the free replacement if it doesn't work right when it's needed.
posted by Kadin2048 at 6:11 PM on March 19, 2019 [1 favorite]

As a professional astronomer, it is humbling and terrifying how little of the sky we observe at any given time.

On the optical side, the LSST will eventually cover a good chunk of sky every night - but only the night side. For a lot of science, that's fine, but when we're talking about identifying extreme (city-killing) hazards, it seems so ... inadequate?

Radio astronomers don't even have daylight as an excuse, but we are tremendously limited by technology and computation resources - for example, identifying where a "fast radio burst" was coming from required imaging a ~1/4 square degree patch of the sky with high angular resolution at 200 frames per second for about 90 hours in total - and we acquired 90 Terabytes of data. The archive managers were really not thrilled about that. For comparison, there are 40,000 square degrees in the sky.
posted by RedOrGreen at 8:59 AM on March 21, 2019 [2 favorites]

Are square degrees in RA just kind of "square" by convention, or how do y'all handle the dimensional changes at polar latitudes? Maybe they're only square-ish, and there are just 40K roughly equal sized patches of the sky subdivided by convention... hmm... what about hexagons...
posted by seanmpuckett at 1:35 PM on March 22, 2019

seanmpuckett: That's a feature of all spherical polar coordinate systems. Area in spherical coordinates isn't as simple as in Cartesian; as you correctly intuited, a "square degree" isn't really a geometric square.

However, Lagrange's Identity provides us a convenient shortcut through what is otherwise a rather obnoxious (IMO) series of calculations. Here's a nicely worked-out example. Note that the end result has both 𝜃 and 𝜙 terms left in it, which would be latitude and longitude, or altitude and azimuth. (The only time I've actually worked with this was doing flux calculations, so I don't know what notation astronomers use, but I assume the principles are the same.)

I'll leave hexagons as an exercise for the reader. :)
posted by Kadin2048 at 2:17 PM on March 22, 2019 [3 favorites]

A decade ago I saw a fireball while I was out walking my dog. It was about half an hour before sunset. Even in the daylight it was the brightest one I've ever seen and it had a greenish tint. It lasted for about a second and then broke into three pieces before disappearing. It was an amazing thing to witness.
posted by Tenuki at 8:05 PM on March 22, 2019

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