VOICEOVER: In the early hours of the 24th of February, 1987,
astronomers at the Las Campanas observatory in Chile spotted something astonishing.
A new bright dot in the sky.
170 000 years after exploding in the Large Magellanic Cloud
just past the edge of our galaxy, the light from the supernova later named SN1987A reached earth
The chance sighting was soon confirmed by other astronomers and made news world wide.
The brightest supernova recorded in nearly 400 years,
and the closest to be captured by modern instruments.
Finally scientists had a chance to observe a supernova at relatively close range,
from almost the first moment it appeared,
testing years of theorising and fueling hundreds of papers worth of research.
SN1987A taught scientists more about these cosmic events than any other supernova - but there is
still so much more to learn - and capturing the first moments as a new supernova appears
in the sky could be key,
which begs the question -
how will astronomers know where to look?
And critically,
make sure they don’t miss the next one?
SN 1987 A was a type 2, core collapse supernova.
when a star at the end of its life, in this case a blue supergiant called Sanduleak 69 202,
is unable to produce enough energy to push back against its own enormous gravity.
It starts to contract, and an iron core forms at its center.
Matter from the core then collapses inwards even further. In mere milliseconds a burst of
neutrinos is released as protons and electrons are compressed so tightly
that they combine to form a proto-neutron star as dense as the nucleus of an atom.
Meanwhile the intense gravity pulls the remains of the star onto this core,
releasing a shockwave that rebounds outwards, with such force that new
heavy elements are produced and expelled as the star disintegrates in the supernova explosion.
The light from a single supernova can be as bright as entire galaxies, but this represents
only a small fraction of the total energy emitted - the rest was carried away by
the near massless, barely interacting neutrinos. And that provides scientists with an opportunity.
KATE SCHOLBERG: The neutrinos actually get out of the supernova before the light does and that
doesn't mean neutrinos travel faster than light the reason is that it takes quite a while for the
photons to beat their way out of the envelope because photons interact a lot neutrinos don't
they just sail out and so the neutrinos will come out promptly and we will get a burst and observe
the burst on Earth before the the light would give us a first, a first signal of the supernova.
VO: This is Kate Scholberg, she is part of a group that set
up the Supernova Early Warning System or SNEWS,
an international collaboration aimed at catching the next big supernova in unprecedented detail.
KATE: That's the name Supernova Early Warning System the neutrinos give us
an early warning that a supernova may be about to appear somewhere in the galaxy
VO: SNEWS links together the world’s neutrino detector experiments,
so that bursts of supernova neutrinos can be quickly identified and reported.
KATE: If any two or more of those detectors send a message that's time
tagged within 10 seconds then snooze will send out an alert to the to the astronomical community.
VO: And that gives astronomers a vital head start.
Telling them to search the skies in the hopes that they will detect the moment that light
from a supernova first reaches earth, hot on the heels of the neutrino burst and rich with data.
SNEWS has been online for decades and has never triggered an alert, and now it's due an upgrade,
KATE: I mean it is very simple and robust and actually that's an advantage it's basically just
run perfectly well almost no downtime over more than decades so that's the advantage of
being simple but being simple means also you don't have potentially full capacity
VO: The SNEWS team wants to make the network more sensitive. To avoid false alarms the
threshold for an alert has always been set very high, but as the years have gone on,
astronomers have become accustomed to receiving alerts from networks like SNEWS
and investigating them even if they turn out to be nothing, and that offers new opportunities.
ALEC HABIG: One of the big things we would like to do with a revamp a SNEWS 2.0 is
be able to have less, less gold-plated input to to the to the network
if we'd be okay chasing after something that might, might be supernova neutrinos might not be
and people aren't upset about it we'd like to do that from our own perspective
then we get to practice we get to get good at it we get to make sure there aren't any bugs lurking
from the science perspective maybe there are things that make bursts of neutrinos
that aren't quite as blindingly obvious as a whole star going kaboom in our galaxy.
VO: And that isn’t all - neutrino detectors have come a long way since SNEWS was first launched
ALEC: They're bigger, their signal is stronger, they would see more neutrinos because they're
just physically larger and in the next few years even larger experiments are coming online and so
possibly now and certainly within the next decade each individual's experiment detection of that
supernova wavefront of neutrinos sloshing across their detector they'll be able to get a really
good time of that wave past my detector to within a millisecond and be able to report that time
and so by getting measurements of individual times that experiments down precisely enough
with today's experiments you could reconstruct the fact that oh that it went it first went
through Italy and then, and then that's Antarctica and then Japan and use the fact
that you know how fast they're going nearly the speed of light and the distances between
those detectors to be able to say so therefore it, it came from over there and again get a
direction on it which of course is very useful if you want people to go chase after it right.
VO: If SNEWS can identify an area of sky to look at, the world’s telescopes will have
a better chance of catching the Supernova - and that doesn’t only include multi-million
dollar observatories. They want all the world’s astronomers to join the search.
ARTO OKSANEN: I'm Arto Oksanen from Finland amateur astronomer
interested about transient events.
VO: Amateur astronomers like Arto are a key part of the search.
Their excellent knowledge of the night sky and flexibility to react quickly to alerts
make them the perfect resource to pinpoint a new object, and they have the advantage of numbers.
ARTO: We amateur astronomers we are worldwide everywhere we can we can jump to any, any object
or target at any time so I, if I get the email from, from some professional astronomers
midnight when i'm observing I can stop what i'm doing at that time and jump on on the new targets.
VO: Alerts from SNEWS bring them into the heart of an international astronomy collaboration.
ARTO: It's the most interesting and gratifying thing to do so
I have been kind of wishing to be a a professional astronomer myself or scientist but now I can, I can be a scientist on my free time.
VO: Observing the next supernova in our galaxy will involve a global collective effort,
huge neutrino experiments and networks of astronomers will point the way,
but understanding these stellar explosions will need many different perspectives.
ALEC: In the past it's been I have a telescope and I can see light of different colors but it's
still all light and then as humanity got radio telescopes for example hey you can see radio
waves you can see past a lot of stuff you can see infrared or ultraviolet or x-rays uh gamma rays
you can see all these different wavelengths they're still all electromagnetic radiation
but kind of the different categories of them are so different that that's they're all different
messengers even though they're really all just photons of electromagnetic radiation
KATE: But there's actually more than that there's more than photon messengers in the, in the universe
neutrinos of course they're my favorite one
neutrinos also bring information there's also gravitational waves and that's a newcomer
and then there's also cosmic rays and so it's really you know much broader than
photons multi-messenger astronomy is you know everybody bringing information to the party.
VO: This is multi-messenger astronomy, the study of all the signals arriving on earth from a
cosmic event like a supernova, and it offers our best chance yet of understanding our universe.
ALEC: And when you have different messengers and you can see
different aspects of the same process you can learn a lot more than just looking through
whatever small hole you're looking through in the fence, no matter how cool a picture you get
being able to have that different perspective of different totally different processes making these
different messengers either different wavelengths of light or particles or gravitational waves
really lets people pin down what really is going on out there.