Physics.
World. Hello and welcome to the Physics World Stories Podcast.
I'm Andre Glasser,
and although last month I did promise you that we'd be looking at the
international Year of basic sciences for sustainability.
Something has happened in the world of physics,
which has shifted that down the schedule a bit. We will bring you that podcast.
But on June the 29th, 2023,
the North American Nano Hertz Observatory for gravitational waves,
otherwise known as Nano Graph,
made a major announcement during a live streamed event from the National
Science Foundation.
The official press release reads astrophysicists using large radio
telescopes to observe a collection of cosmic clocks in our galaxy have
found evidence for gravitational waves that oscillate with periods of years
to decades,
according to a set of papers published in the Astrophysical Journal.
Letters from the press conference. Here's Dr. Sean Jones,
the assistant director for the Director of Mathematical and Physical Sciences
at the National Science Foundation.
In 1995, the Hubble Space Telescope revealed the Hubble Deep Field,
a tiny sliver of the night sky brimming with a veritable zoo of galaxies in
various stages of evolution. In 2022,
the James Webb Space Telescope refined and deepened that image fantastically
displaying galaxies more than 13 billion light years away from earth.
Aided by the state-of-the-art optical and infrared telescopes and decades of
advancement and instrumentation and data processing,
we perceive a static image of distant galaxies.
Today's announcement shatters that perception of a static universe through the
direct observation of gigantic gravitational waves washing across our
Milky Way galaxy, spawned by cataclysmic events, including some,
some from the most distant regions of the cosmos.
These observations reveal a rolling,
noisy universe alive with a cosmic symphony of gravitational
waves.
In the recent announcement,
the nano graph team announced the detection of shockwaves from what they believe
could be the merger of super massive black holes.
You may be thinking, hang on,
didn't they already detect gravitational waves at the Ligo Virgo observatories a
few years ago? And if you've been listening to this podcast for a few years,
then you'll know that they sounded like this.
The difference here is that rather than one-off events,
nano graph has detected a consistent hum triggered by gravitational
waves.
It could be the first direct evidence of the stretching and
squeezing of space time due to black holes,
and it opens a new window on the universe speaking to physics
world, his Ben Steppers from the University of Manchester.
The gravitational wave, um,
is often referred to as being a ripple in space time.
So it's something which is generated when, uh, well,
it's most easily detected when you have massive objects, for example,
orbiting each other. And so that generates a, a,
a so-called ripple in space time. But like if I throw a stone into a, uh,
into a pond and you see the water ripples, um, we have the equivalent of, uh,
of what gravity does to a space time.
Nano graphs started as a group of about a dozen scientists back in
2007. It's now grown to 194 members,
including 77 graduate students at over 80 institutions,
not only in the US but around the world.
Cherry Young was involved in the early stages of nano.
I am a radio astronomer,
and my research interest is in everything transient things
that, um, uh,
like explosions and fast time scales or things like
pulsars that we can detect their, um, posters,
radio posters very well using radio telescope facilities. Uh,
during my PhD,
I've worked on a pulsar all Skye blind search using the
Australian Parks radio telescope,
and then I moved to Canada where I spent eight years, um,
of my time on the Chime radio telescope, uh,
helping to commission this new facilities,
which has led to a large number of fast radio burst
discoveries.
And it is also involved in Pulsar research. Uh,
very recently moved to France where I took up a
permanent astronomer position at the C N R S National Research
Institute.
And so I'm hoping to continue my work on Pulsar Fast Radio Burst and
set, as well as my other research interest.
I think we're need to talk about those things,
but maybe we'll talk about them later because, um,
there's a particular topic for this podcast.
The Pulsar Community.
We are very excited to share with the public the discovery wave of
evidence of gravitational waves from the Pulsar Timing experiment,
basically using, uh,
the fastest spinning millisecond pulsar in a pulsar timing array experiment to
detect gravitational waves. And this is a really long time effort.
We have been doing this experiment for over a decade now.
The idea is to observe an ensemble of these millisecond pulsars,
and they have extreme rotational stability.
We can pre predict the arrival time of their pulses to a extremely
high precision. Normally the pulses, um,
stably ticking away that,
but the idea is if there is a gravitational wave,
some distortion of the space time in the background, we will see,
uh, the arrival time of the pulsars from a certain region of the sky.
We'll see the pulses arriving a bit earlier and maybe the,
and the another direction of the sky might be a bit later due to the passing of
this gravitational wave from the background.
So the idea is to use these pulsar pulsar pulses
to, to work backwards to detect the underlying gravitational waves.
And after over a decade of analysis,
we think we have finally reached the significance threshold to say that we have
seen the first evidence of these waves.
Pulsars were first detected in 1967 by Northern Irish physicist
Jocelyn Bell.
You are probably familiar if you've been listening to this podcast recently with
the story of how she was overlooked in the 1974 Nobel Prize,
celebrating that discovery,
which was shared by her supervisor Anthony Hewish and the radio
astronomer Martin Ryle. That podcast, by the way,
was the Physics World Stories Podcast from back in May,
in which we look at the impacts of the Belbin El Graduate Scholarship Fund
funded by money generously donated by Jocelyn from prizes.
She has subsequently won. I asked Cherry to remind me what pulsars are.
Uh, basically pulsars are rapidly spinning neutron stars,
and they, they are extremely dense. Um, and they,
they have a size of, um,
a city like London, probab probably, I would say the, the diameter,
um, of a pulsar could be the size of London,
but it has the mass of mod,
like one and a half times our sun all squeezed into the
size of London. So it's really dense.
And this is what contributes to the very
extreme rotational stability. These pulsars, um,
have emission coming from the two poles.
And an interesting fact is that the rotational axis and the
emission axis are misaligned,
just like how it is in a lighthouse, if you know what that is.
So as the pollar spins, we,
we see a pulse when the emission passes our line of sight.
So this is what causes the, um,
apparent pulsation. It doesn't mean the side is pulsating, it's just rotating.
And we see, um, the signal and whenever it comes to us, us.
Using pulsars for the detection of gravitational waves,
where's this fit in the history of the hunt for them.
The idea of gravitational waves first brought up,
it was by Einstein in 1916, right? So that was really a long time ago.
And although there has been some proofs, um,
so some evidence of gravitational waves in the past,
they were not the same as what we have seen now with the postal
timing wave. The first proof of gravitational waves was about 60 years after
Einstein first talked about it.
And that was from one pulsar binary system.
The astronomers realized that there is a pulsar that is in a binary system with
a white dwa and, uh, the, the fact that they are operating each other,
but as time goes by, they are getting closer and closer to them, to each other,
uh, at a rate predicted by general relativity.
If they are radiating gravitational waves losing energy as they
get closer to, to each other. So this was, uh,
an evidence of gravitational wave,
but only indirectly because we could only say on dance maybe the waves because
the, the two objects are getting closer to each other.
It was however very exciting and this analysis won
a Nobel prize, um, as well.
And then the next breakthrough was from li g o, um,
was also quite recent in the last few, 2015 I believe,
was when LIGO first detected gravitational waves by two colliding still a mass
black hole. How now, um,
fast forward into 2023 posts are timing array
has now contributed to yet and other evidence of gravitational waste.
But this time from, um,
the pre-merger of super massive black hole. So these are even more,
um,
much more massive objects compared to what LIGO has seen.
Super massive black hole as is named, such as its name suggests, uh, really,
really massive black holes. And, um,
let's say they are sort of millions to even billion times, um,
the size of our sun.
And we believe that in the center of most galaxy,
there should be a black hole and throughout the cosmic history,
galaxies merge and the black hole in the center collide to form
bigger galaxies and bigger black holes.
And eventually we'll get to these super massive monster black,
black holes and they should eventually merge as well. And the,
the signals we are detecting from the Pulsar timing array experiment is actually
not from individual merger because these events are
from so far away.
The amplitude of it is really, really tiny.
And what pulsar timing array we currently has the ability to detect with belief
at least is the, um, background of these waves.
That is the distortion in space time caused by
many of these supermassive black hole pre-merger,
all through the cosmic history and the, yeah,
the signal of them combining adding together is what,
um, led to this little distortion,
a little humming in the signal in the, in the,
in the deviation of the pulsar arrival time that we see.
Why do we think that it is specifically those mergers over time that's caused
this hum? What's, what tells us that.
In fact we are not a hundred percent sure what we are detecting
is from super massive black hole.
It is however the very most likely reason
because.
It's sort of so big that it has to be something that catastrophic if you.
Well, I think it's smart that, you know,
from Einstein has predicted when massive objects come together,
they will lead to the emission of gravitational wave.
So we think super massive black hole merger will definitely cause this.
And from simulation we under,
well we have some idea of how many of these events might have happened during
the cosmic time and if we, if they emit in this way,
we see that they would add up to such a kind of signal that Tulsa timing array
would have detect something by now. And we did,
we indeed detect features in our data that is consistent with this,
these predictions.
This is why we think supermarket black hole merge pre-merger is the best
explanation. However,
there are other possible courses for these background
gravitational waves that could lead to this humming that we see
now data including dark matter axion,
black holes left from the beginning of the universe,
the so-called primo black holes and even cosmic strains. So
it's not a, yeah, it's not a, it's not a done deal yet. We are still, we will,
we will need to improve the, um,
sensitivity of the postal timing array experiment to really pinpoint, um,
the exact, uh, origin of these signals.
And I think we will be able to achieve that in the next years because,
um, so the, the recent discoveries is published by diff individual different,
um, postal timing communities.
There are a number of collaborations that have been working on this postal
timing array experiments.
So there's a large North American collaboration called nanogram.
There is the European Timing Array,
there is the Australian Pulsar Timing Array.
There is a group in India and there's a group in China and they have all
sort of seen the same signals now.
But the next step is really to combine data from all these individual groups
that this is what we're called the International Postal Timing Array,
and which will have the most sensitive detection,
the best sensitivity of all,
and hopefully we'll be able to answer some of these questions. So.
Are there particular pulse cells that you're looking at?
Yeah, personally, uh,
my role in the Pulsar timing array experiment is that I have, um,
conducted many of the nanogram pulsar observations
using the R receivable and the green bank telescope. Um, uh,
a nanogram for example,
we have about 80 millisecond pulsars that we monitor
regularly. Uh, well our receivable has been decommissioned, uh,
two years ago, I think now it's been two years. Um, but uh, with,
uh,
green Bank we get these regular scheduled time to monitor the pulsar
in the array experiment. I also use the chime radio telescope,
the, um, one in Canada that I mentioned earlier. Um,
chime gets to see, um, the sky every single day.
So we have really high cadence observations of all of
these 80 pulsar, some of them every single day,
some of them every few days. So, um,
we analyze all these data and add them to the pulsar timing
every experiment.
So something quite probably colliding super massive black holes
is sending out gravitational waves across space and disturbing the
pulsars and our reading of them back here on Earth.
But how significant is that? What can we use that discovery for?
These objects that ate gravitational waves such as super
massive black hole? It's, they are, they are invisible to most,
uh, electromagnetic waves because they do not, um,
we cannot detect them in another way. So using reputational waves,
it really opens up a new window to study these sources that we cannot
probe otherwise.
The reason is that gravitate gravitational waves interacts very weakly
with matter, so they basically pass through, uh,
the cosmic history untouched.
And so studying the, studying these gravitational waves,
we can really learn about these objects that emitted them from the first place.
We are also hoping to get a better understanding of these merger of supermassive
hole, of how, um,
they merge together forming the bigger galaxy and how, um, these
hierarchical merging events lead to the universe as we know it today.
Okay.
Brilliant. How can we use those pul sars?
They act as almost like a cosmic clock.
We know exactly when the next pulse is going to come.
And so by studying the arrival time of these pulses and
to,
and by paying attention to whether there's any deviations from what we expect,
we can work backward to see, ah,
what might have caused these distortion in the arrival time or
why are these pulses coming earlier? And some are the later,
some other ones later. And this is exactly what we have done.
We've studied many pulsers in different part of the skies,
and by realizing that some of these pulses comes earlier
and some of these pulses come later,
we figured out that there must have been a gravitational waves that has
distorted the space time between the earth and these pulsars.
That's brilliant. So you were involved in this fairly early on. Does it,
is it something that you've been desperately waiting to hear the news?
What does it, what makes you want to go back to study?
Yeah, pulsar is very, um,
how do I say it's, uh, very dear to me. It's, um,
what I did my PhD thesis on.
I've, um, um, spent a lot of my research time studying pulsars.
I was involved in monograph mostly, uh,
between 2015 and 17 where I collected a lot of these
pulsar observations during the time.
So it was really exciting to see these decade long
efforts finally coming to fruition that we could finally say we have seen
the evidence of gravitational waves.
But I think the cool thing is this is just the beginning. Um,
we know that the next step is to combine the data set from all these different
experiment and for sure the sensitivity will increase.
We'll hopefully be able to really study the astrophysics of these
superman black hole and how the merger history throughout the universe.
We'll return to cherry shortly,
but this news has caused perturbations beyond the Pulsar community.
Al Cordova describes herself as a writer of words, maker of videos,
lover of the cosmos, sci-fi tv, movies and literature.
And she posted this on Instagram.
We got space time compressions, gravitational waves,
signals coming from the Pulser timing array.
We're using spinning stars as a telescope to watch some old black holes doing do
to dose. Now these waves could be coming from dozens of things, dark mattered,
worm holes, even cosmic strains because the universe is old,
it's been busy as hell. So where the ripples come from is kind of hard to tell,
but the drumming and the drumming of the waves that are coming is the summing of
a humming that's becoming so stunning and it really paints a beautiful tapestry
of the ancient cosmos and its majesty. Look,
we're just a little planet in the Milky way of burbs trying to understand the
universe and how it occurred and now we have a brand new way to observe.
So it's just another win for the whole planet Earth. Well done guys.
Vasel Cordova and the beat is by Cato producer on Instagram.
My own foray into the world of physics began by studying
Seti, the search for extraterrestrial intelligence at Chadro Bank linked to the
Manchester University. So when Cherry said that she's now working with Seti,
I wanted to know more about what she's up to since working on the
Pulsar timing array. Yeah.
It was actually very interesting how, uh,
I got involved in Seti. Like I said,
my background is in Pulsar and I worked on Phos Fast fast radio burst as well.
It turned out that the study of Pulsar Fast Radio burst and Seti actually have
some common ground. Um,
basically we are detecting very small signals in the radio, uh, data.
And so I started, uh,
working with the Breakthrough Listen initiatives in
2021, I think.
And I was leading the commissioning of two city
projects on one on the,
on the very luxury in the US and MECA telescope in South Africa.
We are hoping to use this really, um,
state-of-the-art radio telescope to
do a systematic search for set signal in the sky. Um,
these telescope are interferometric facilities and
what that means is that they can give us a really large sky mapping speed so
that we can scan a large part of the sky, um, all at once.
In my opinion, we haven't detected any, um,
convincing e t I signals yet, but
I don't think they necessarily not exist.
I think we just haven't looked enough.
If you take a look at the parameter space,
we have searched for steady signal throughout, um,
the time we haven't, we have only, um, well we haven't,
we haven't looked much really,
we have only searched for a very small range of emitting frequency range and the
number of stars that we have observed is only to the other of a thousand or so.
And this is tiny fraction compared to the total number of stars even in our
Milky Way galaxy. So, um,
I think with the V L A and the MECA study project, this will,
they will really bring a game changer to the set field by hugely increasing
the number of stars we can monitor for any setty signal.
If.
You did find an extra terrestrial intelligence and you could
communicate with it, what would you ask is what would you ask it? You know,
whether these gravitational waves were caused by super massive black holes
combining, for example.
. I think
I know if I can only ask for one, if I can only ask one question,
I think it won't be this one because I think we are quite sure that it should be
super massive like h causing the gravitational.
I think if I to wanna ask my question probably be how can humanity
survive climate change .
I'd like to thank Jenny Eng for talking to me for this episode of the Physics
World Stories podcast and I can't help but wonder whether we will find signs of
extraterrestrial intelligence or a solution to climate change. First,
in any case,
the next steps for NANOGrav and the other gravitational wave groups around the
world is to try and sift through the background to distinguish specific
gravitational waves and trace them back to their sources and they can then
combine that data with the observations that have been made in the
electromagnetic areas of light.
And the potential is there for new and exciting discoveries to be made
in this new frontier for astronomy. Speaking at that nano GR announcement,
here's Dr. Maura McLaughlin,
the Ely Distinguished Professor of physics and astronomy at West Virginia
University.
Well this is not at all the end of the story .
This is just the end of the beginning.
Nanogram is already working on our next dataset,
which we'll have 17 to 18 years of pulsar timing data.
And we expect that the evidence for the gravitational wave background that we
have found in this dataset to be much stronger in that one.
And we're going to become even more sensitive with time as we increase the
length of our dataset as we add more pulsars to our array,
and most importantly,
gain access to bigger and better new radio telescopes with more dedicated
nanogram observing time. In addition,
we are very proud to be a member of the International Pulsar Timing Array.
The I P T A was formed 15 years ago and consists of Pulsar
timing array collaborations worldwide today
groups in Europe, Australia, India,
and China have also released results from their most recent gravitational wave
analysis.
And we all see similar features in our independent data sets,
which of course is reassuring and also incredibly exciting.
Furthermore,
through this collaboration and partially supported through an N S F Excel net
Award,
we are working with colleagues around the world to combine our current dataset
with Pulsar timing datasets from large radio telescopes in Europe, India,
South Africa, and Australia,
to form an Uber dataset that will be much more sensitive than any of the
individual data sets alone.
We aim to announce results from a gravitational wave analysis of this combined
I P T A dataset within the next year or two.
This analysis will be truly transformative.
It should result in a significant detection of this gravitational wave.
Background hum. In this combined I P T A dataset,
we may even detect our first individual supermassive black hole binary
source and likely also be able to observe it with electromagnetic
telescopes at optical x-ray or other wavelengths truly
ringing in the era of multi messenger ano hertz gravitational wave
astronomy. Ultimately,
we will produce an incredible map of invisible gravitational waves
from gargantuan black holes spread across cosmic time.
We will also probe some other exotic and less well understood sources for this
background.
We are so thrilled that you are joining us on this journey. Thank you.
At one time, all we knew about the universe resulted from visible light,
light we can see with our eyes.
Then when radio and x-ray and gamma ray telescopes came online,
we learned so much about the universe that we just couldn't have imagined
before, like the radio pulsars that Jocelyn discovered over 50 years ago.
Now we can only dream about what we'll learn with observations and a different
part of the gravitational wave spectrum from the LIGO detections that
visionaries like KIPP made possible with continued investment in our science,
science and in large radio telescopes.
And we are certainly expecting the unexpected.
All we have to do is keep listening.
We'll be back in September when we'll be looking at Green energy,
including an intriguing new project from the European Space Agency called
Solaris. I dunno about you,
but that makes me want to watch an old Russian science fiction film.
But this is about solar panels in space feeding
back their energy to earth. And if that sounds like science fiction,
that's because it is. I can recommend News from Gardenia by Robert Lou Ellen,
who you might remember as Creighton from Red Dwarf.
His science fiction novel contains that very idea.
And if you are looking for some reading this August ahead of that podcast,
next September News from the Squares and the book that comes before it,
news from Gardenia, from Robert Lu Ellen. Good.
Make a welcome edition to your summer reading.
We'll be back with more on Solaris and some other fascinating projects next
month. But for now, thank you very much for listening.
Physics world. I.