NASA System Predicts Impact of a Small Asteroid over Germany | Hacker News Reader

NASA System Predicts Impact of a Small Asteroid over Germany

nasa.gov

47 pointsalex_young18 comments

I wish they would have used the term "predicted" instead of "predicts" in the title of their article (just to keep my blood pressure down).

At least they use "very small" in the title, whereas here it's just "small" (maybe NASA edited it in the meantime?).

...but fortunately the asteroid was in the news a few days ago, so I correctly predicted (ha!) that they are referring to that one.

Several videos: https://www.wionews.com/science/watch-asteroid-turns-into-fi...

> scattered small meteorites on the ground at the impact site about 37 miles (60 kilometers) west of Berlin

Do we know how fast those small meteorites are travelling when they hit the ground? Are they like bullets or more like snowflakes?

They're rocks, so at least like rock hail.

Somewhere in between, but probably closer to bullet speed. There are numerous accounts of meteorites entering people’s houses.

Here’s a recent one: https://abcnews.go.com/US/scientists-confirm-meteorite-crash...

It pierced the roof but didn’t pierce the floor.

If it can pierce a roof, then it can pierce the human body as well, so it's pretty deadly.

You can very roughly estimate the lower bound pretty easily, by assuming a meteorite to be roughly spherical and ballparking the drag coefficient. So its volume = 4/3 * pi * r^3. Its surface area = 4 * pi * r^2. We can assume half of its surface area is its cross section. So just change the 4 to a 2 above to get the cross sectional area. Meteors generally have a density up to around the 8000 kg/m^3 range. So now we have everything we need to calculate terminal velocity using a calculator. [1]

for a 1m meteorite:

mass = 4/3 * pi * 0.5^3 * 8000 = 4188 kg

area = 2 * pi * 0.5^3 = 0.78 m

The defaults for density and drag coefficient are fine enough. And we get a result of at least 500m/s, assuming air resistance is sufficient to slow it down to terminal velocity. The exact number will vary quite a lot - especially as this is for a whole meter sized meteorite that doesn't disintegrate, but this is at least a reasonable ballpark. So the tl/dr would be: more like a bullet, but with somewhere around 140,000 times the kinetic energy, for a 1m meteorite.

[1] - https://www.gigacalculator.com/calculators/terminal-velocity...

I assume that the pieces get enough time to decelerate to terminal velocity after its fragmentation and explosion in the upper atmosphere. If so, it would be like rocks falling from a great height - not supersonic, but you wouldn't want to get hit by one.

One nitpick here - meteors aren't called meteorites until they hit the surface.

Vital to note: the asteroid was detected by a guy sitting in Hungary a mere three hours prior to impact. NASAs system pulled the reported data and calculated its trajectory.

“ The asteroid 2024 BX1 was first observed less than three hours before its impact by Krisztián Sárneczky at Piszkéstető Mountain Station of the Konkoly Observatory near Budapest, Hungary.”

“(Scout) automatically fetched the new data from that page, deducing the object’s possible trajectory and chances of impacting Earth.”

Equally unsettling - it was about 1 meter in diameter and the fireball was visible from large swathes of north Germany, there are numerous videos.

Is this the state of the art asteroid detection we have?! We're doomed.

Selected quotes:

*[1] A small asteroid about 3 feet (1 meter) in size disintegrated harmlessly over Germany on Sunday, Jan. 21, at 1:32 a.m. local time (CET). At 95 minutes before it impacted Earth’s atmosphere, NASA’s Scout impact hazard assessment system, which monitors data on potential asteroid discoveries, gave advance warning as to where and when the asteroid would impact.

*[2] This is the eighth time in history that a small Earth-bound asteroid has been detected while still in space, before entering and disintegrating in our atmosphere.

*[3] The asteroid’s impact produced a bright fireball, or bolide, which was seen from as far away as the Czech Republic and may have scattered small meteorites on the ground at the impact site about 37 miles (60 kilometers) west of Berlin.

I'm not sure how I feel about 95 minutes warning [1], had it been larger would there be more warning or would that be the alert time had it been heading for (say) Berlin.

I'd be interested in knowing how many were missed during the time they had advance warning for the eight seen [2].

[3] Damascus Sky Iron!!

very probably small pebble sized and smaller pieces that mostly would be hard to find

95 mins about enough time to have a last meal while watching a movie. If you are gonna go out go out in comfort.

I can imagine tons of things I would do in my last minutes, but neither watching TV nor eating is among those.

Be honest, you'd be on HN arguing with the rest of us.

To be fair HN is less a cesspool compared to Reddit or 4chan. But for how long?

I guess if the asteroid was larger and more of a threat there would be more of a notice period.

Unless its coated in Martian stealth technology...

Beltalowda

They have some good data now. So can they calculate the likely warning times for somewhat-larger sizes of asteroid ? Then they can identify the worst case scenario and get thinking about how to address it.

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