Since the beginning of the human story, the stars, planets
and the dazzling Milky Way have been a constant presence
in the night sky.
They have helped us navigate the oceans and chart time,
and they have inspired great works of art.
But worsening light pollution means the glories of the night sky are now
hidden from many of us.
In this programme, we'll be looking at the impact of light pollution,
not just on astronomy, but on life itself.
And we'll also be discovering how to work around light pollution,
lessen its impact, and looking at ways to provide beautiful dark
skies for future generations to enjoy.
Welcome to The Sky At Night.
Here in London, a new attraction is the Van Gogh experience.
Oh, wow.
We're here to experience one of the artist's most famous
paintings, Starry Night.
Well, this is impressive, isn't it?
This is amazing.
It's like being inside the picture. Yes.
I mean, I think it does portray that - it gives you the impression
of being out under an impressive stellar sky,
and your mind whirling because of what you're seeing.
Yes, I think he drew this when he was actually in an asylum
suffering from depression.
So I'd like to think of this is the antithesis.
You know, he's in a horrible place,
but this is where he'd like to be.
Yeah, looking out at the universe,
and I like the fact it's a real night sky.
Obviously, it's not a technical drawing.
It's swirly and impressionistic.
I think that's Venus up there, the crescent. I think it must be.
So I like to think this is actually what he was seeing
from outside his window.
Just seeing it makes me feel quite peaceful.
And that's what seeing the night sky makes me do.
It sort of relaxes me, and I think we need more of that.
I think what's interesting is you can imagine a modern version.
You'd have to light the church and put streetlights in.
It's very hard to experience being under a dark sky like this.
Ever since industrialisation,
astronomers have complained
that the night sky isn't as dark as it used to be.
But over the last decade, we've been able to combine satellite
data with ground observations to quantify the problem.
And it's not just astronomers who are interested in the data.
Chris spoke to Kevin Gaston, a biologist
at the University of Exeter.
Well, Kevin, thank you for talking to us.
What do we know about the conditions of our skies?
How bad are things?
I think we're learning very quickly that they're much worse
than we imagined.
Something like 80% of the world's population is living under
light-polluted skies, and that's nearer to 99-100%
of the population in Europe.
Is that a way of quantifying what's going on?
Can we say something about how bad things are and whether it's getting
worse or getting better?
If we just take the raw data that satellites
are directly measuring,
we estimate that between 1992 and 2017, so about a 25 year period,
emissions have grown by about 49%.
But as we've undergone a sort of lighting technological revolution,
bringing in LEDs, which emit much more in the blue, very commonly,
we've had to explore ways of, if you like, adjusting
the calculations to understand
just how important and significant those blue emissions are.
The satellites that have been used over the last 25 or more years
have been very limited in their detection of emissions in the blue.
So that sounds like things are worse than we expected.
If we then adjust for the bits in the blue and the shift to LEDs,
that's at least 200%, 270% and maybe a lot more than that.
So we've been quite drastically underestimating what's happening.
Obviously, it matters to astronomers because we want a view of the sky,
but there's a broader issue here.
Why does light pollution matter?
Biological processes and their timings are foremost driven
by two things - they're driven by temperature
and they're driven by light.
And what we're doing here is we're messing
around with those light signals.
So it affects organisms' physiology.
It affects their behaviour.
It affects where... Their ability to know
where they are in the season. It...
And those have impacts on reproduction, on mortality,
and therefore on populations and communities.
And these things just ramify through ecosystems.
If we're influencing the natural world then,
presumably, do humans suffer similar effects?
I think where our psychology in terms of kind of our place
in the scheme of things,
I think it's something astronomers
have kind of perhaps thought about more than many others.
There's also those impacts on physiology, and there's
lots of concern around how that might feed through to impacts
on mental wellbeing, on impacts,
on potentially cancer risks and so forth.
But what do you think we should do in terms of rules for lighting?
Are there things we can do that that are plausible?
Lighting is one of those things that we could change very quickly.
We have a lot of night-time lighting
that persists all night long,
when actually there aren't many people who are using it.
And actually, we could exploit sort of more responsive technologies
that actually light things when you need it.
Well, I think this sounds like an excellent idea.
So, Kevin, thank you very much.
For all the reasons Kevin describes it's becoming increasingly obvious
that we need to work on reducing light pollution and protecting
the few pockets of dark sky we have left.
Pete met up with Dark Skies Officer Dan Oakley in one of those dark
spots known as Moore's Reserve,
after our very own Patrick Moore.
Dan, we're in this fantastic location here.
Where exactly are we?
We're in the South Downs National Park.
We're at a site called Old Winchester Hill, and you can see
all around us, we've got this lovely rural landscape, but we've got
lovely big cities all the way to the south that provide us
with all the light pollution.
Portsmouth is about 15 miles away.
We've got Gosport. Yes.
All the way around to Winchester,
which is over that hilltop over there, got Basingstoke,
and up towards the north we've got Guildford,
and a bit further you'll see London as well. Right, OK.
And although our reserve has a central core area,
which is where we find the darkest skies... Yes.
..we've actually got little pockets of dark skies
all the way along the south coast, that even touch onto the iconic
Seven Sisters cliffs in the... Right.
..and you can get the same experience there.
So it's not all about protecting the core.
For us, it's about protecting any bit of dark skies...
Sure. ..across the South Downs.
So in order to meet the Dark Sky Reserve criteria, how dark does
it actually need to be?
Is there a value that you measure?
So we have to use a sky quality metre... Oh, yes.
..which is a little device that I point to the sky,
and it measures the brightness
in the small patch of the sky... Right.
..converts it to a number, compares that to the Bortle scale.
And from there, we can compare ourselves to other sites worldwide.
OK. I mean, we're definitely level four, which is a rural.
And as you can tell, we are, you know, properly rural.
But, you know, we're a good rural sky.
We know we can see the Milky Way here,
which is the important... Oh, that's amazing. Yes.
So I mean, that's where people start their experience.
So all these people on the south coast, they've got half an hour
and they can come and see their home, the Milky Way.
That's pretty amazing, yeah. Yeah.
I should explain that the Bortle scale
is a nine-grade scale, isn't it?
A nine-point scale where one is ridiculously dark
and nine is what you get if you were living in a city,
so four's pretty good. Four's good.
I would love to be a three but, you know, there's just too many
people living here, which is great because they can enjoy it.
And for me, it's the experience,
rather than the actual measure, I think.
Well, I'm really excited to come back and have a look at the sky
when it's dark tonight. So hopefully the clouds will disappear,
and we'll get a view of the stars.
Yeah, no worries. See you later!
Well, it's dark, Dan, but the clouds haven't gone away, unfortunately,
but you know, in a way that's helped us to see
just how special this site is,
because you can see the light pools around us, can't you?
Quite clearly. Yeah. For us, it's all about the relative differences.
So you've got... You can see all the light, all the light
pollution from all those different sources coming off the clouds.
But as soon as you stop that... that move away
from the urban environment coming into the rural, you can see
that the density of housing goes down, the amount of light
pollution goes down.
So this is what we're trying to protect.
This kind of... This buffer zone between the urban and the rural.
So that's why keeping this is very, very important... Dark,
because it's protecting the night sky above our head.
The International Dark Sky Association requires
you to have a certain value of darkness to the sky.
You were mentioning earlier about your dark sky metre.
Have you brought it with you? Yes, I have, it's right here.
Yeah, it's one of the... One of the hand-held versions,
so it's just a nice, easy thing with one button on it,
and we just basically just press it up to the sky...
Yeah. ..and it gives us a reading. 17.5.
Now, that's not particularly dark...
Because you've got clouds up here, yes.
So we'd expect to see about 20.5. Right.
That's actually the point where my eyes can pick out
the Milky Way quite well.
And this is the thing you've got to do for your IDA requirement.
But the trouble we had, as a national park in the south,
is we didn't think we were dark enough. OK.
And when we compared ourselves to places like Exmoor who went
before us... Yes. ..they kind of know they're dark
because they've got big areas of open wilderness.
So we took a different approach by taking a GPS version of this,
sticking it on the side of a car.
And then I just basically drove around the South Downs for three
years at night, you know, late into the morning,
taking all these readings.
And from that we developed a lovely,
colourful map of where all the sky quality was,
and that map we now use for planning purposes and gives us
a good way to implement the policies a bit more smarter.
But how do you go about keeping this in place?
I mean, do you need to have legislation in place to make people
obey the dark sky requirements?
Well, I mean, we've got the planning law, which does a certain extent
and we have environmental nuisance laws as well.
But I think, from the authority's point of view, we like to engage
with our communities.
So I think it's important that we get those messages
and they're really simple messages. So, you know, you get a lot
of questions about how I can do my garden light and make it better.
Right. And we just tell people, you know, do the basic. 101 for light
pollution is make sure the light's going where it's needed
and not up into the sky. Yes, yes.
And you'll see that kind of principle
in all the good street lighting.
So a lot of the places on the... on the... on the downs,
the lighting authorities are Hampshire, West Sussex
and East Sussex.
All their street lights make sure the light goes down and, if it's not
going up into the air, we get to see more stars.
When we submitted our application to the dark skies,
I mean, the motto I gave the application is we may not
be the biggest, we might be the darkest,
but we will be the most cared for. And I think that's right.
We've had communities all along the South Downs, even outside, even
communities in Brighton wanting to do their things
to help cut out light pollution.
So the messages were there,
and it's slowly getting embedded... It's spreading out.
..which is brilliant, it's exactly what we wanted to do,
it's exactly the point of reserve.
It's getting those principles embedded in all levels of society.
Well, I think the Dark Sky Reserve is a fantastic testament
to the amount of work you're all doing.
And it's just... It's incredible.
I actually find it...
It lifts my spirits to know this is happening
and it's spreading out.
It's just superb. Brilliant job. Fantastic. Thanks.
Around 80% of us now live in bright urban areas, and many have to travel
a significant distance to experience dark skies like these.
But that doesn't mean you're out of luck.
Chris went to meet a group of astronomers who are determined
to show that wherever you live, you can still enjoy the night sky.
Astronomy group the Baker Street Irregulars have been preaching
the gospel of inner city astronomy for over ten years.
But here, a Television Centre under bright
west London night skies, it's easy to be sceptical.
Well, gentlemen, I've observed in some ridiculous places
for The Sky At Night, but I think this wins the award.
What are we doing here?
Why are we in the middle of London trying to look at the sky?
Well, we just want to prove that the good astronomy can be done
from any location, regardless of the conditions.
And it doesn't matter if you're a middle of a city,
it doesn't matter if you're middle of the light pollution.
Good astronomy can still be done. No problem.
So we're just off to prove this.
What are the simple tips for people who want to observe with the naked
eye from the middle of a city? What can you do to help?
Well, one thing that you can do is move away
from local light pollution.
So don't have any lights immediately in your surroundings,
or going on to go into a relatively locally dark area.
Dark adapt your eyes.
Get used to being outside in the dark. Absolutely. Yeah.
Take somewhere between 20 and 40 minutes for full dark adaptation
and you'll see a lot more.
You three in your group have been really ambitious.
So, so... So what have you gone on to do from inner city skies?
I mean, we've all branched out in various directions,
which is why we've got a little group here today.
We have ISS imaging here. We have people
who like night-vision devices. Well, let's go in order.
Let's talk about the space station, because I think there's something
about seeing the space station in the sky and waving
at it that really appeals to people,
but you've taken it much further than that.
Yes, it's definitely, I think, one of the brightest objects in the sky,
one can observe wherever you are, whatever
light polluted city you are living in.
You said you'd photographed it as well.
How did you go about doing that?
I had to experiment myself, because there are no descriptions
that... Or recipes that... How you need to do this.
I had to experiment a bit,
but it's a telescope and a high frame rate camera...
And swinging it across the sky. Exactly. So it's manual tracking.
Do you have a particular favourite image that you've captured
or a particular pass of the space station that sticks in your mind?
There are a few, if I probably have to choose one.
It was last year I had a birthday present.
The ISS just went in front of the moon and even
Chris Hadfield, the astronaut, shared it on Twitter.
So you managed to capture a photo of that from here in London?
Yes, it's an animation because we're taking high frame
rate camera videos.
It means that you can actually see it zoom past. Can we see it here?
You can even see some of the spacecraft that docked
to the International Space Station.
Yeah, yeah.
Very often, if you go out at night in the early evening,
all of the planets are so bright they will be out before any
of the stars. So, from an urban location,
very, very easy to identify.
I mean, we have one taken of Venus here, but in this case, we've used
an ultraviolet filter and combined the normal white light images
with the ultraviolet so we can get some cloud detail there.
Filters are part of this game.
If we're doing city astronomy and city astrophotography,
filters are really important.
Very much so. If you take a look here. Yeah.
Here we have the Andromeda galaxy.
This shot is taken unfiltered and unprocessed, but if we show
you the same picture, once filters have been applied,
and it's been properly processed, you can see the sky now has gone
back to black, nice and dark.
You can see all of the stars behind it.
You can see the dust lanes, everything.
And we should say when we say filter,
this isn't a Photoshop filter.
This isn't something in the computer.
This is the filter on the telescope that stops the light pollution.
getting in. Absolutely.
I have to say I'm a... I stare at a laptop most of the day.
And so when I come and want to use the telescope,
I want to look through it.
I'm a visual observer. Is there...
Gavin, is there anything we can do to rescue that experience
from the middle of the city? Right? Yes, there is.
And that's obviously my... That's my passion, is live visual observing.
What I use to help me is this device you see here,
which is a night-vision monocular used by the military.
OK. And this actually intensifies the light by about 60
to 70,000 times. So in films, this is where you see them look,
and it's all green and people are running around in the woods,
that sort of thing. Exactly, but this one is actually white.
So more natural looking there, and that's one of my favourite
nebulae, the Rosette Nebula.
So, so let's look at this. The structure in this image
is just lovely.
So that's through a telescope with this enhancing
night-vision device. Yes.
And if you know what you're doing, you can achieve spectacular results.
These might look like pictures from the Hubble Space Telescope,
but they're actually the work of a member of the Baker Street
Irregulars taken from right here in light polluted London.
Well, it's brilliant and important work that you're doing.
Keep it up and, you know, let's enjoy the sky wherever we are.
Thank you.
Well, hopefully we've convinced you that even from a rooftop
in a city, there's plenty to see in the sky.
So to tell us what to look out for,
here's Pete.
Well, it's still cloudy here at the Moors Dark Sky Reserve,
unfortunately, but if it were clear at the time we're filming this,
Orion would be just below the horizon for me.
But by the time you're watching this, Orion will be well placed
in the southern part of the sky,
and Orion is a fantastic constellation,
regardless of what your sky quality is like.
If you live in the city, you can only make out the brightest
stars, and that actually helps you if you're a beginner
in astronomy, picking out the main pattern because you haven't got
the faintest stars to confuse you.
If you've got slightly darker skies, you should be able to make out
the faint line that runs underneath the belt of Orion,
and that's Orion's sword.
If you've got binoculars or a small telescope,
then have a look at the sword. Right in the centre,
you should be able to make out a misty patch, which is the Orion
Nebula Messier 42.
Now, if you look up at the belt again and use binoculars,
you should be able to make out some fainter stars around that.
And the reason for that is that this is a region occupied
by an open cluster known as Collender 70.
Now you can use the belt again to good effect,
because it's a good measure, a sky ruler, if you like.
You basically identify the line made by the belt,
and then look at the star on the left hand,
or eastern side of the belt.
That's Alnitak, and imagine that's a pivot point.
Then if you rotate the belt by 90 degrees in an anti clockwise fashion
around that point,
where the free end ends up, that points to Messier 78,
another region of nebulosity.
Now I like this region.
If you look at it with a telescope, you'll see that there is some
mistiness with two bright stars in there.
It always reminds me of car headlights
coming towards you in fog.
And if you go back towards Alnitak,
that's the star on the left-hand edge of Orion's Belt,
and you've got slightly darker skies, still,
you should be able to make out an area of nebulosity
just to the east or the left of that star, and that's another
nebula known as the Flame Nebula NGC 2024.
Now, the problem with viewing the flame
is that Alnitak is a really bright star,
and you get natural light pollution from that star
which ruins your view, so it's quite difficult to see.
Now, the next object is really quite tough
and you need to have really dark skies,
a big telescope or an astrophotography set up to see it,
because running south from Alnitak is a curtain of nebulosity -
that's known as IC 434.
Now, to the east of that curtain, there are fewer stars,
and the reason for that is there's a big dark cloud blocking the way.
Now there's a finger of that cloud which sticks out in front
of that curtain of nebulosity, and that finger forms a silhouette,
which looks exactly like the profile of a night piece from a chess game
and that's known as the Horsehead Nebula or Barnard 33,
but that is a really tough target to see visually.
And if you have really dark skies,
then consider taking a wide field photograph of Orion,
a long exposure wide field photograph,
because then you should be able to make out Orion's alter ego.
There's a huge loop of nebulosity that surrounds the main pattern,
that's called Barnard's Loop.
And around the stars,
which form Orion's head,
there's another circular patch of nebulosity and that's the
Lambda Orionis Nebula,
or the Angelfish Nebula.
Now, those two circular features taken together give
Orion his alter ego.
He looks just like a giant snowman in the sky.
Now, as anyone who's taken a long exposure photo of the heavens
will know, it's increasingly common
to have your picture ruined by streaks
of light produced by orbiting satellites.
But this form of light pollution is nothing new, as Maggie
has been finding out.
In 1997, the Iridium programme was born. The dream was to start
a new era in mobile telephony using satellites.
Imagine great connectivity no matter where you are in the world.
But there were problems.
Firstly, the Iridium programme needed a lot of satellites
and secondly, each satellite had a large antenna
which was highly reflective.
The early satellites caused an iridium flare, a novelty
in the night sky that was enthusiastically photographed
by some, but which was a visual nuisance to others.
The trouble was the 66 satellites worked like a dream, a technological
triumph, and now the idea has been replicated
on a massive scale.
Space X and others are in the process of installing
42,000 satellites into low-Earth orbit.
These mega constellations will provide internet
to remote areas.
The impact that these thousands of satellites may have an optical
observations is easy to appreciate, but other forms of astronomy
are also in danger,
as I found out from Tim Stevenson from the Square
Kilometre Array Observatory.
Hi, Tim, it's lovely to speak to you.
And we've got this glorious image, an artist's impression
of the square kilometre array.
But can you tell us what it's going to do?
The two telescopes will be the largest radio telescopes ever
built, and size matters when it comes to radio telescopes.
You get high resolution and you get greater sensitivity,
so we're exploring a larger region of the universe than we were before.
So what sort of things can you pick up with radio astronomy?
You can explore both the structure and evolution of our galaxy
in very, very high resolution,
but also the structure and the evolution of the broader universe.
We've been talking about optical telescopes and the challenge
of having dark skies and light pollution.
Do we have similar problems with radio astronomy?
Five years ago, most of the emitters that would cause us problems
from space were stationary in the sky, geo-stationary,
So you could avoid them. You could look around them.
You could look past them, so to speak.
But now the two constellations, the mega constellations
that are deployed at the moment, they radiate about 13 gigahertz.
So for us, that sits in our Band 5B. Now, it's much more intense
and the sources are rapidly moving.
You mentioned this 5B wave band and you mentioned
that it's vulnerable. Can you tell us what it gives us?
So carbon monoxide, which is an important indicator of the general
gas concentration in stellar forming processes
and galaxy evolution and so on, at certain distances
we can't see it because these spacecraft are radiating
very strongly in those bands,
and it lines our telescopes. Yes.
So you're swamped by the local signal coming from the satellites.
So this sounds like a real challenge,
but can anything be done about it?
The most obvious thing for us to do is to deal directly
with the industry, appeal to them that we have a problem
and get their cooperation now
and work with them in understanding their system
and their commercial imperatives,
and negotiate with them to minimise the amount
of radio frequency power that we see on our sites.
So you're not talking about sort of shifting the frequencies
to somewhere else. You're talking about sort of having...
effectively sort of turning the satellites off
when they're over certain areas or... Yes. That's exactly right.
You can't shift the frequencies because effectively,
these major constellations operate within ITU rules,
and they're only allocated certain bands in which to operate.
So Tim, I guess one of the problems
is that these constellations of satellites
are trying to provide internet to rural areas,
and you build radio telescope in rural areas to get away
from the noise.
So aren't these two things in conflict?
Yes, indeed they are.
But part of it is already resolved,
because our telescopes are in radio quiet zones as they call them.
And these radio quiet zones are established by law.
The government of South Africa and Australia, respectively,
have actually made it illegal to operate radio equipment
in these zones. But they are rural and, in the case of South Africa,
underdeveloped areas and these, the communities within these areas
would benefit very much from the improved internet connectivity.
Well, I hope the negotiations go well.
And as you say, we're all scientists and engineers
sort of working together, so hopefully solutions can be found.
Thank you so much for speaking to me today. Thank you.
Through this programme, it's really been interesting to see how light
pollution is affecting everything, really.
Yeah, it's a serious problem.
I think we think of it as an astronomical issue,
but it affects how people sleep, their mood, it affects wildlife
and the problem's getting worse.
But I think there are solutions.
Technology means we could be smarter about lighting.
We can put light where we need it, when we need it,
rather than just lighting up whole swathes of a city.
Just because that's easy. Yes.
And the thing is - environmentally that makes so much more sense.
But with light pollution as well, it's not just affecting us,
it's affecting everything.
It's sort of wildlife all over the world.
Yeah, and maybe we should look up at the sky and be reminded
that that's worth preserving.
People want to go and see the northern lights.
People want to at some point go and sit under a dark sky.
I think it's good for people to get out and look up and see
something spectacular. For all that you can do astronomy in the city,
there's nothing like being in a properly dark site looking
at the kind of view that Van Gogh was enjoying.
That's all for this month.
And so, until next time from this starry night...
A happy new year to you from everyone here at The Sky At Night.
And as always, goodnight.