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Stellar Explosion in Earth's Proximity (phys.org)
235 points by dnetesn 25 days ago | hide | past | favorite | 83 comments

They did it, they finally did it!

Context: I did my diploma thesis work at that lab, and shared the office with those guys. This is a result almost 10 years in the making.


So stupid question, what was the slow part of this? Was the spectrometry process developed just for this?

They were using a so called accelerator mass spectrometer (AMS). The main challenge, as I understood it from talking with them, was in the chemistry required to prepare the samples for injection into the AMS. Specifically ensuring that there's no background signal created from the preparation itself. So there was a lot of work done just to get the process right (the less steps to prepare the sample, the less steps that might contaminate it). Then a lot of verification, calibration on the AMS and optimizing the beam transport to reduce losses as far as possible.

EDIT: The AMS was built and used in a lot of experiments before that. Among other things done with that instrument was measuring the neutron flux of the nuclear blast at various locations in Hiroshima, by determining the isotopic composition of the copper on building facade elements. Neutron capture produces some radioactive as well as "unnatural" stable isotopes and by determining their ratio, one can determine the neutron flux and energies.


It saddens me, that the accelerator they (and I for that matter) used for their research, has been decommissioned as of last year and is being dismantled right now :( – I could start a major rant about it, that would touch the subjects of funding, some people's personal pride and good science vs. fashionable science.

Please, rant away! I'm interested in your opinion and the context of the decommissioned machine

I left academia not long after our satellite got de-funded (it's still in orbit, operating and sending telemetry, just the Navy's side of the satellite that is.)

Recessions will also hit even harder - when the next grant cycle hits in the winter/fall, a lot of good teams are going to get screwed. I really hate the inconsistency and the waxing and waning - fwiw, there were times my team just grabbed grant money and spun wheels on old research, so it's not just that the money dries up easily, I don't think there's good accountability when the money is flowing either.

https://news.ycombinator.com/item?id=24650325 asks whether this was caused by the same supernova that created the Local Bubble.

As someone with inside knowledge, can you review my reasoning that it fits, and it probably was?

> As someone with inside knowledge, can you review my reasoning that it fits, and it probably was?

No idea. I left that particular lab a few months after I graduated which was 8 years ago.

yaaay i dont know anything about the subject but its something about science and somebody made progress so i will be happy just like a golden retriever is anytime you start dancing out of joy! im happy because you are happy!

Should have added a [2.5 million years ago], I was worried for a second there

It's 2020, my first instinct was to look at the sky to try and spot the impending supernova.

How good is our supernova detection technology?

Would we be able to predict one with reasonable precision [1] before it wipes off the face of the Earth, or would we fry with gamma rays before we knew what was going on?

1: "by this time next year we'll all be dead with 99% certainty"

Betelgeuse, the only star that I know of within the range to produce a supernova dangerous to us, has scientists looking at it closely. Mostly because it's a closeby giant and those are interesting.

I think most estimates range between 40'000 and 140'000 years until core hydrogen is exhausted. It's ejecta are unlikely to reach earth or cause harm (either radiation or otherwise). So while it lasts, you can enjoy reading a book under the light of a dying star at night for a few days.

Eta Carinae is another candidate but it's too far away and unlikely to outshine Venus significantly. It's also not due for some due. There is also the possibility it'll just collapse into a black hole with no fanfare or extra light emission, it'll just be gone one day.

Supernovae usually come from very bright stars, those are easily detectable and visible. From what I remember, there aren't any candidates even close to us that are about to expire minus Betelgeuse, which isn't aiming it's poles at us and won't do much harm.

I would like to add that in the even we could predict that a supernova is about to wipe us out, there isn't anything we could do. Any nearby object we could use as shelter, such as Venus, Mars, the Jupiter Moons etc would likely be just as affected if not more (Jupiter's magnetic field will likely make a Supernova hit more deadly IMO). It would be over within the span of a few days and nobody will survive. Just lean back and enjoy the show, tbh.

I wonder if there are any sci-fi books with a doomed planet along these lines. Pick up 10 years before the planet gets destroyed. People of the past lived with the futility of trying to escape, doing almost nothing, and now people are desperate and taking insane scientific risks to try to save the species.

If you're talking about a massive gamma burst sterilizing life on the surface of the planet there are some continuation of the planet options with a 10 year timescale. Ark submarines full of embryos that are mass produced by a world that somehow puts aside their differences and comes together for the singular goal of saving life.

Restarting the carbon cycle would require a massive effort, but with planning and lots of hard work it might be possible. The post apocalyptic world would be a strange place full of dead plants and animals that take a long time to start decaying because all of the microbiota that normally cause decay were also killed off. It would be interesting to see how fast they would spread afterward. It would give humanity a small buffer before they start releasing gigatons of CO2 into the atmosphere at least. It really depends on how well the oceans survive. If algae can come back reasonably quick the planet can be saved.

I think there is also the issue that that level of gamma will mess up atmospheric chemistry. Something like

N2+O2 -> dissociated N and O plasmas -> NO2

Which means the air might become not breathable.

I don’t think there would be much in the way of dead plants and animals lying around. In an oxygen atmosphere any organic material would ignite, and a sufficiently intense burst would melt anything on the surface of the crust that doesn’t burn.

Neal Stephenson's Seveneves is a great read kinda along these lines.

I loved Seveneves but I disagree that it provides an indication of how one would face this kind of emergency. For sure one would not venture into space if one fears an onslaught of harsh gamma-ray radiation. It’s an entirely different kind of disaster.

(SPOILER: Admittedly, the underground and underwater subplots might be more applicable but... they’re side-shows at best.)


There's a trilogy starting with The Last Policeman with a similar scenario: kilometer-scale asteroid projected to hit in about a year. To a first approximation everyone just says "Well, fuck, guess we're going to die." Thinking about the ways that seemed unrealistic and how I thought it would go instead, Seveneves turned out a lot more like it (though with exciting-story elements injected, and also in Seveneves they're starting from maybe a decade ahead of us in space tech). (The Last Policeman is still interesting in other ways.)

Egan's Diaspora is another good match, with an astrophysical cataclysm instead of a merely planetary one. It happens to a much more advanced future society, though.

Larry Niven has a short inconstant moon where the main character looks up at the moon which brightens to 1000 times normal brightness, what that means dawns on him shortly later.

It was the plot of a Star Trek: The Next Generation episode, and a pretty good one.


Years ago, and it might have stolen the story from somewhere else, there was a Twilight Zone/Outer Limits/Tales from the Darkside type show and in one episode space explorers are visiting the remains of a charred planet ~2,000 light years away. They learn the star that went supernovae and that it is the star the three wise men followed to Bethlehem.

>Years ago, and it might have stolen the story from somewhere else,

Yes they did. It was Arthur C. Clarke's "The Star"[0]. And it was "The Twilight Zone" (1980s version).

While the TV episode was interesting, the short story itself is much better. I highly recommend it.

The story was in the "The Nine Billion Names of God" collection[1]. The title story is also interesting in its religious focus.

[0] https://web.archive.org/web/20080718084442/http://lucis.net/...

[1] https://en.wikipedia.org/wiki/The_Nine_Billion_Names_of_God_...

See the classic Larry Niven short story Inconstant Moon, collected in All the Myriad Ways.

In Ring World there is a massive burst in the galaxy center and there is a race that, instead, puts its planets in formation and moves them to the edge of the galaxy.

There's Outer Wilds, a video game where you're 22 minutes away from your star going supernova. It's pretty good.

Three Body Problem has this as one of the premises.

Core hydrogen is already gone in Betelgeuse case.

It's a matter of when it gets to Fe56 and exceed Chandrasakhar limit

> Jupiter's magnetic field will likely make a Supernova hit more deadly IMO

Why is that?

I imagine that it could channel radiation rather than divert it. Or channel ejecta.

I am irrationally frustrated that I won't live to experience this. I mean there are so many more important things to live for, but...

We could go underground like the Morlocks.

Ultimately I'm not sure it matters if we detect a supernova that will kill us within a year. That's not enough time to do anything about it, but enough time for worldwide panic and massive suffering before we all die anyway.

We'd really need to know at least 10-20 years out. Enough time to rally the world to find a solution but not enough time that it ceases to be a concern (like thousands of years).

That's an interesting thought. Severe consequences of climate change can be expected within decades, but apparently that is still to far off and hard to imagine for many people, and hard to sell for politicians. This leaves me wondering if people would accept decades of worsening quality of life (moving into caves etc.) even if the alternative was certain death by gamma rays.

I think the climate change thing has little to do with how far off it is. It's just that the people who stand to benefit from not mitigating climate change are both powerful politically and wealthy enough that the effects, even if they happened much sooner than predicted, wouldn't likely effect them. Sure, they may lose one of their homes on the coastline. The mass migration away from coastlines will be devastating to humanity, but not to those people or their children. Heck, even worst case scenarios like massive social unrest or resource wars aren't likely to effect these people. Their kids certainly won't be going off to war!

In other words, it's not a problem of being able to imagine the effects. I suspect the powerful people resisting climate change mitigation can imagine the effects, they just know those effects won't touch them.

I presume that if the astronomers did spot an imminent supernova that threatens to extinguish life on earth, we’d collectively respond by lowering interest rates to stimulate the economy...

I think right now “reasonable precision” means “within the next few ten thousand years”.

After Betelgeuze blows, we should know more about what to look for.

I think that’s the real problem. We have no first hand observations of the processes around a supernova before it blows up. It may take a very long time until we will get these observations.

Wild that this throwaway “haha 2020 amirite?” comment got at least 22 karma. HN comment SnR has really nosedived in the past year (yeah I know, I’m not supposed to say anything because guidelines, but it’s true).

Well that would be against the anti click bait journalism ethics guidelines.

Here let me fix it: "...in 2.5 million year cycles"

Me too. But thinking about it more, the good thing about astronomy is that everything is in slow motion. We'd probably have a long time to react.

We would probably cause our own mini stellar explosion on Earth before anything hit us from somewhere else.

seriously, my heart was pounding for a sec. the subject line should really be changed.

> When the brightness of the star Betelgeuse dropped dramatically a few months ago, some observers suspected an impending supernova—a stellar explosion that could also cause damage on Earth.

Why do people keep fretting about Betelgeuse?? No, it's extremely unlikely it will harm earth when it goes nova: https://arxiv.org/pdf/1406.3143v2.pdf

But it will look amazing.

> When this supernova explodes it will be closer than any known supernova observed to date, and about 19 times closer than Kepler’s supernova. Assuming it explodes as an average Type II super-nova, the optical luminosity will be approximately -12.4, becoming brighter than the full moon.

Do we have any idea how long that light would last, and how long it would take to get to full brightness?

Typically 3-5 months I think. It's not like it just turns on and off either, it flares up then slowly fades over time.

Heh remember the panic about CERN creating mini black holes?

Science reporting is so very bad.

I'm not saying the LHC did create a mini black hole and suck the Earth into a parallel pocket universe on a dark dystopian timeline, but... gestures vaguely at everything

I mean, that's a good philosophical premise for a book, I think.

Would we know if we were sucked into an alternate timeline via that kind of science? Would it matter to us? Could we change it?

I'm sure there's a YA novel in there somewhere.

Every single SciFi show uses a shimmering effect when that happens, and I never saw that effect. So, it either happened when I was sleeping or otherwise wasn't looking, or it didn't happen. Or maybe it happened the night I took all of those mushrooms. Never can tell if I'm seeing something or just seeing something.

I'm pretty sure going through a micro black hole involves everything being spaghettified and... waaait a minute, now that you mention it I've been eating a LOT of spaghetti these last few months.

In the good timeline, KitKat had a dash in its name, Fruit of the Loom had a cornucopia in its logo, Pikachu had black on the end of its tail, C3PO didn't have a silver leg, and you could go up in the torch of the Statue of Liberty.

And since then we are all trapped in... the Twilight Zone! (cue spooky music)

And don’t even get me started on Project Z!

It ain't just science reporting.

> Briefly stated, the Gell-Mann Amnesia effect is as follows. You open the newspaper to an article on some subject you know well. In Murray’s case, physics. In mine, show business. You read the article and see the journalist has absolutely no understanding of either the facts or the issues. Often, the article is so wrong it actually presents the story backward—reversing cause and effect. I call these the “wet streets cause rain” stories. Paper’s full of them.

> In any case, you read with exasperation or amusement the multiple errors in a story, and then turn the page to national or international affairs, and read as if the rest of the newspaper was somehow more accurate about Palestine than the baloney you just read. You turn the page, and forget what you know. – Michael Crichton (1942-2008)


Actually, I remember reading at the time that the "We promise it won't create black-holes" narrative came from the PR department of the lab itself to draw attention to their work. It was very successful.

1. Sensationalism sells advertising. Don't overlook media dynamics.

2. Reasonably solid understanding and low risk notwithstanding (Beteleuse, at 300 light years, is well outside the 50 l.y. danger zone), some people will harbour some uncertainty, warranted or not.

3. It'll still be the biggest pop in the neighbourhood for a while.

Another quote from later in the article:

> a very close supernova could inflict massive harm to life on Earth

...but they fail to mention how close this "very close" is. I assume 700 light years (Betelgeuse) is a little bit far away to qualify? As a total amateur in astronomy/astrophysics, I would assume that if there were any "very close" stars that are massive enough to go supernova, they would already be known?!

50 light years is the generally accepted distance that would cause problems. There are no candidates this close that could cause a type II supernova (this is when a massive old star, like Betelgeuse, collapses), but there could be potential type I supernovae lurking closer. These are binary pairs of a white dwarf and another star where the white dwarf is accreting mass from the companion and reaches a limit (the Chandrasekhar mass) where runaway nuclear fusion spontaneously occurs.

Side question do we know why it dipped in brightness?

Was the "could also cause damage on Earth" theory a widespread worry? I never heard that in any of the reporting of the issue.

My "worry" was based only on losing one of the nicest stars in the Heavens, although a certain excitement of the idea at the same time.

If anyone is not familiar with Anton Petrov, he churns out YouTube videos on new astronomy and astrophysics papers. He does a wonderful ELI5 job of explaining the evidence and what it all means in the grand scheme of things. He did one on this paper earlier this week.


He’s a truly wonderful person. ;)

Is this the cause of the Local Bubble? Phil Plait's Death From The Skies book mentions a 'smoking gun'.

It seems to line up well enough. And it is hard to imagine another explanation.

The gas arrived here 2.5 million years ago. According to https://en.wikipedia.org/wiki/Local_Bubble it seems that the Local Bubble was created 10-20 million years ago by a supernova, and we've been traveling through an area currently occupied it for the last 5-10 million years.

If we've been traveling through that region for 5 million years, and the bubble is expanding as fast as we are moving (and we are moving at a pretty good clip), then we would have encountered the edge of the bubble 2.5 million years ago. Which would be exactly right for that to be this.

And it is hard to imagine that there has been another supernova near us that it could have been, without it having left obvious signs of its existence. So Occam's razor says that this has to be right. The supernova that we know from astronomy had to happen near where we are now is the one that dumped detectable amounts of material on us 2.5 million years ago.

The Local Bubble is thought to have been caused my multiple supernovae. See e.g. this 2002 paper: https://arxiv.org/abs/astro-ph/0205128v2

Edit: Here's a more recent paper - https://link.springer.com/referenceworkentry/10.1007%2F978-3... :

> "More detailed models for the origins of the Local Bubble have found that it requires anywhere from 3 (Smith and Cox 2001) to 20 (Fuchs et al. 2006) SNe to create a bubble with the correct characteristics in terms of size, pressure, and emission characteristics."

Surely (even) if it was deposited here 2.5 million years ago, it would have taken an insanely long time to get here.

Considering that a supernova jettisons material 15,000 to 40,000 kilometers per second [0], it would only take a few decades for the material to reach earth from a star in earth's proximity, which I interpret as a few light years away.

[0] https://www.nationalgeographic.com/science/space/universe/su...

Also, the material swept up from the supernova, by the Earth is of the order of hundreds of tons (https://en.wikipedia.org/wiki/Death_from_the_Skies!)

That would be 400--1,000 years for a supernova 50 light years distant, and clearly less for a closer event.

Astronomically and geologically an eyeblink.

There's thought that it was so close, we're still flying through the remnants.

Always fascinated by historical observations of super novae: https://en.wikipedia.org/wiki/History_of_supernova_observati...

I wonder if the The Permian Extinction (250 mil years ago) was caused by something like that?

Astrophysics just seems soooo speculative. Even with margins of error in the millions of years and light years, it just seems that most of it is assumptions supported not by evidence (because we can't get direct evidence) but by previous assumtions which have over time fossilised into accepted theories.

Not saying this paper isn't good or anything, just that extrapolating a supernova from a few atoms of an isotope of a metal seems... a long fetch. Though probably better than nothing.

Well, they have to come from somewhere and supernovae are the only process that makes them. If you find them consistently in a layer of a certain age all over the Earth, that points to a single source. Two different isotopes too, but only created by the same process so far as we know. It’s pretty decent evidence.

As for direct evidence, I know what you mean. There so way to observe the supernova, but how often do the jury get to watch a murder happen on film? Yet we still convict murderers.

Given how flawed jury based systems are I’m not sure that’s a good analogy :p

As against all the other better systems?

'Speculative' is an interesting word choice.

There are assumptions in play, but I doubt they are the ones you are thinking of.

The two main ones are that physics is the same everywhere, and physics is the same all the time. We have no way to say if these assumptions are correct, but we don't have evidence that they are wrong and we do have observations that are consistent with them being correct.

If we take those two assumptions as true, then astrophyiscs is squarely in the middle of the model and measure of hard sciences.

Modelling in particular is wide open for speculation, but there is no reason to think speculative models will be maintained if they are not consistent with measurement. Even the simplest speculative models necessarily have falsifiable and testable claims - if they don't then they don't say much about how the world is.

The nature of astrophysics means that we are able to test and measure in so many ways: near and far, in the present and in the past, atomic scale and galaxy scale. As long as we hold those two assumptions above, we have a lot of evidence and reason to believe our current astrophysical models of the universe.

How do you define evidence?

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