Let's talk about explosions.
[explosions]
Nope, none of those. I'm thinking of the biggest explosions in the modern universe
star explosions, or supernovae.
Supernovae release an unfathomable amount of energy.
A supernova can outshine an entire galaxy
And if one was to happen in our galaxy it would be visible even during the day.
But all of that light is only a fraction of a percent of the energy from the explosion
Almost 99% of the energy from a supernova is carried off by my favorite particles, neutrinos.
Today, on Even Bananas,
we're going to talk about what these tiny, hard-to-spot particles can teach us
About the biggest explosions in the universe.
[music]
You might have heard the phrase: "we are all star stuff." And it's true.
Stars make almost all the elements that are vital for life.
And supernovae are a really important part of that process.
When a star explodes in a supernova, that's when it makes the heavy elements.
And, the explosion flings matter in all directions
allowing the future creation of planets, and on at least one planet, bananas.
If stars are the kitchens where the ingredients for life get cooked up
supernovae are the delivery trucks bringing those ingredients to your neighborhood.
But supernovae also produce neutrinos.
We're talking a lot of neutrinos, like, a disturbing amount.
A supernova will release more neutrinos in the span of a few seconds
than over the star's entire life.
And it's not exactly like stars are slacking on the neutrino production front before they explode.
Hold out your hand.
Don't be shy.
In the time it takes me to say this sentence,
several trillion neutrinos from the sun will pass through your hand.
Almost none of those neutrinos will interact with your hand, though because
neutrinos barely notice we exist.
But if we can spot these explosions
neutrinos can teach us a lot about the end of a star's life.
Stars that go kaboom
could end up as a neutron star or a black hole.
But we don't fully understand how that whole process works.
One way to figure some of that out is by watching a supernova happen
from beginning to end.
And we can do that with the help of something called SNEWS.
[loud snoring]
No, not that 'snooze'.
I'm talking about the SuperNova Early Warning System.
And I know, it kind of sounds like some sort of natural disaster alert.
But fortunately for us,
the stars in the Milky Way that could go supernova soon are a nice, safe distance away.
So, they don't pose any danger to us on earth.
To tell us more about SNEWS
what it is and how it works
let's talk with Fermilab scientist Anne Schukraft.
Anne studies neutrinos from space and from neutrino beams we make at Fermilab
and she works with me on the MicroBooNE and DUNE experiments
> Hi, everyone!
SNEWS began in the early 2000s.
It's a group of seven neutrino detectors around the world
feeding into a central system.
If they see a spike in neutrinos simultaneously
SNEWS can say "look, a supernova!"
SNEWS is exciting for astronomers because
when a star does go supernova
the neutrinos arrive at earth several hours before the light arrives.
Giving them a big heads up.
Now I know that sounds like neutrinos are going faster than light
but stay with me because they're not.
Remember, neutrinos only interact through gravity and the weak force
which is... weak.
Photons, or particles of light, on the other hand
interact through gravity, the weak force, and the electromagnetic force.
So neutrinos leave the core of a supernova barely disturbed
while photons get jostled and bumped around on the way.
Anne has a really great way to describe what's happening.
I like to think of it this way.
Usain Bolt and I both go shopping
and when finished, try to exit the shop at the same time.
We can all agree, Usain Bolt is faster than me
but as people stop him to ask for an autograph
I'll sail right through the exit.
That's what happens in a supernova.
Neutrinos travel just slightly slower than the speed of light
but they still arrive before the light does because the light got interrupted.
So, back to SNEWS.
Remember, it's a network of seven neutrino detectors across the world.
If any experiment detects a potential burst of supernova neutrinos
it sends data to a central computer.
If two or more detectors spot a burst within 10 seconds of each other,
the computer automatically alerts its mailing list.
And of course, there are lots of checks built into the system to avoid false alerts.
In fact, SNEWS has never actually sent out a supernova alert
So, it's not the most busy computer.
Two experiments at Fermilab are signed up to get the alerts if one is sent:
MicroBooNE and NOvA.
And NOvA is actually working towards
becoming one of the experiments feeding into the network too.
So the next question you're asking might be
"Have we ever spotted the neutrinos from a supernova before?"
Let's hear more from Anne.
We have successfully spotted supernova neutrinos once
from supernova 1987-A, in 1987.
We saw a total of about two dozen neutrinos
across three neutrino detectors worldwide.
Astronomers see hundreds of supernova each year
but only ones in our galaxy are close enough for us to spot the neutrinos from them.
We expect two or three supernova in our galaxy per century
and there hasn't been one since 1987.
If one happened tomorrow, we would expect to spot tens of neutrinos in NOvA.
That doesn't sound like much
but our accelerator normally fires trillions of neutrinos at it each day
and we only see a couple of neutrino interactions.
DUNE, an experiment we're building over the next 10 years
would see thousands of neutrinos from a nearby supernova.
That would generate up to 100 terabytes of data in a minute
which obviously presents a big computing challenge.
So, what would we learn?
If we could see all the neutrinos from a supernova over the whole explosion
that would really help us understand how core-collapse supernovae happen
because we could watch it happen in neutrinos.
Of course, it would also be a great source of neutrinos in our detector
and we could study those to learn more about the properties of neutrinos themselves.
All in all, it's pretty exciting stuff.
As we keep building better neutrino detectors
we'll have even more opportunities to spot neutrinos
that have traveled from space to share their secrets with us.
And if we're lucky enough to witness a supernova in our galaxy
SNEWS will be ready to share the news.
That's it for this episode of Even Bananas.
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Fun fact!
One of my favorite parts of SNEWS is the name.
Scientists had fun proposing catchy acronyms for the alert system
Things like 'POTATOES'
and NBCNEWS
and PANIC
But in the end, SNEWS won out
and it was suggested by three people independently.
I think it's pretty good.
But why don't you join in the name game?
Leave a message in the comments
and let us know what clever supernova alert acronym you would've proposed.
Here's mine:
Early neutrino (V) Event Network using Big and New Apparatuses Near A Supernova