All language subtitles for BBC.The.Sky.at.Night.2024.Hiding.in.Starlight.1080p.HDTV.x264.AAC.MVGroup.org

The movement of the sun at
the centre of our solar system

sets the rhythms of life
down here on Earth.

Its rising and setting mark the
beginning and ends of our days.

Its presence, or absence,
sets our seasons.

And it provides the energy on which
almost all life on Earth depends.

Its presence is a constant
in all of our lives,

which is why it's remarkable
that every 18 months, or so,

across a tiny slice
of the planet's surface,

the sun disappears, briefly,
in a total solar eclipse.

These events have been studied
since ancient times with awe,

wonder and fear.

These awe-inspiring events
have allowed people to observe

the sun in ways they can't
at any other time.

They have revealed the secrets
hidden in the bright light.

In 1715, an eclipse over the UK,
which was timed at multiple sites,

gave us a better understanding
of the moon's orbit

and helped us predict
future eclipses.

And, in 1919, two coordinated
observations provided

experimental evidence for Einstein's
theory of general relativity.

It's no wonder we're so fascinated
by eclipses.

So, tonight we're looking at
technology which will allow us

to create eclipses on demand -
to study not just our own sun,

but also the other stars
across the universe.

Welcome to the Sky at Night.

There's plenty of news
from the universe this month.

A team using ESA's Gaia satellite
have discovered a black hole

30 times the mass of the sun,
lurking just 2,000 light years away.

We haven't seen evidence for a black
hole of this mass on its own before.

And so, the discovery marks
a step forward in understanding

how they're created.

Closer to home, NASA is looking
again at plans to bring back

Mars rocks collected by the
Perseverance rover.

The original plans, despite
ESA's help, were threatening

to eat the entire planetary
science budget

and were unlikely to bear fruit
until the 2040s.

A review is looking for new ideas.

If you have any, send them to JPL,
California, ASAP.

But in the meantime,
Perseverance trundles on.

But, of course, the most exciting
event for me, personally,

last month
was the total solar eclipse.

I've been lucky enough to travel to
four total eclipses in my time,

and they're always
incredible events -

the one on April 8 was no
exception.

And while I was in Ohio, in America,
Pete was more than

1,000 miles away in Texas.

Both of us were in
the narrow band of totality,

where the moon blocks the sun
completely,

revealing its beautiful outer
atmosphere, the corona.

Well, that was the plan.

And it's a beautiful morning.

Very excited about what's coming up
later, and trying not to think about

the fact that the weather forecast
says that high clouds

are going to roll in
just when we don't want it to.

The skies, they're a bit mixed
at the moment.

There are lots of big blue patches
up there.

Luckily, the temperature can change
dramatically during an eclipse.

In Ohio, it dropped by about
ten degrees -

and that can change the wind,
the weather, and the clouds.

In the end, both Pete and I had
beautifully clear skies.

He got some amazing pictures.

But pictures can't do such an event
justice.

They don't show the contrast
between the detail in that

pearly white corona, the purple sky,

and the darkness of the moon's disc.

Nor do they really show the
360 degree sunrise, the orange

as light seeps in all around us
from beyond the shadow.

And all the while, at the back of
your head, there's just something

screaming that the sun
has disappeared.

It's an incredible experience.

Totality just passed.

Every time I try and tell people
what an eclipse is like,

what a total eclipse is like,
and there are no words for it.

I cried.

It was beautiful.

There were prominences.

There was a prominence, a bright
orange glow at the bottom

of the sun, beautiful corona,
long streamers,

a solar maximum corona.

All of which makes sense,
scientifically, but...

My God...

We're so lucky to live on a planet
that does this.

We made it - we got totality.

The skies cleared, and...

It's just an amazing sight.

It's really, really emotional.

It's been an emotional
roller-coaster.

I never want to do another
eclipse again.

That's a lie.

But it's absolutely superb.

We saw the whole of totality.

We saw Venus, we saw Jupiter.

The corona was amazing.

Apart from the sheer magnificence
of the event, eclipses allow us

to study the sun in a way
that we can't at any other time.

When kids draw a yellow disk
for the sun, or you look through

eclipse glasses, you're seeing
a layer called the photosphere.

But rising above that,
heated to over a million degrees,

is the sun's upper atmosphere -
the corona.

And it's this region that scientists
are able to study when the light

from the sun's disk is blocked.

But each eclipse lasts
just a few minutes, at most,

so scientists have been thinking
about creating their own

controlled eclipses.

Maggie's been finding out about
a new mission that does just that.

MAGGIE: I'm in Belgium, at
a space facility where they're

in the last stages
of a very special mission.

Wouldn't it be great
if we could have a total

solar eclipse every day?

Well, that's just what the European
Space Agency are trying to do

with their new mission, Proba-3.

This will involve two satellites
flying together in formation.

One acting like the moon
during an eclipse,

blocking out the light of the sun's
central body...

..while the second will observe
the sun's corona.

By blocking out the sun in this way,
Proba-3 will reveal

the innermost workings
of the sun's corona,

allowing us to study it
in more detail than ever before.

This should hopefully give us
better prediction and protection

against space weather, but also
reveal some of the greatest

mysteries of our sun.

I'm meeting Damien Galano,
project manager of Proba-3,

to find out more.

Now, you've been involved in Proba-3
right from the get-go.

So, where are we at the moment?

So, how does the spacecraft work?

So, the occulter is the thing
that's going to block out

the majority of the sun?

Yes.

OK.

So, you mentioned that the distance
between the two spacecraft is 150m,

and that is defined by the size
of the occulter.

Why the balance here?

OK, yes.

Yes, but hard to launch.

THEY LAUGH

Proba-3 aims to study the corona
for six hours

in every 20-hour orbit.

That's like images we see during
an eclipse, but for 100 times longer

than the fleeting glimpses we get
from natural eclipses here on Earth,

giving us a detailed look that may
reveal a solar secret.

So, with this system, we are going
to actually get a much more

detailed view of the corona -

but the corona very, very close
to the sun.

And I believe there's a mystery
there, because the surface

of the sun seems to be cooler
than part of the corona.

That seems very counterintuitive.

Yes.

And with Proba-3, we'll be able
to get to that boundary between

the very edge of the sun and that
sort of massive temperature rise,

and so, hopefully, the mystery
will be solved.

Damien, thank you so much.

It's been fascinating getting
an understanding of how this...

challenging mission will work.

I'm looking forward to seeing it
in the clean room.

Thank you. Thank you.

The satellite is being tested
just along the corridor,

so I have to take a look.

I'm meeting Marie Beeckman,

who is the satellite operations
test manager.

But this is a delicate piece
of space kit, so we have to don

some clean room gear before we can
get anywhere near it.

So, Marie, we're in between
the two satellites now.

Yes, we are.
It's very exciting to see them.

So, can you talk me around
the chronograph?

Yes, of course.

So, first of all, we have the actual
camera there.

That's, like, why we are doing it,
kind of, to do the pictures

of the corona.
That's the science.

Yeah, that's the science behind
the whole thing.

That's what we can find there
in the left.

It actually has a little door.

What does that do?

So, the door is actually there
to protect the instruments,

because it's not possible to have
the full sunlight

onto the instrument. So, we have
to wait, we have to make sure

that the other satellite is
positioned perfectly in front

of the door, like,
casting the shadow onto it,

and only then we can open the door
and take the pictures of the corona.

And that perfect positioning
will be done by the two spacecraft

communicating with each other.

The two brown ones,
these are actually the antennas,

making sure that we can
communicate well.

Oh, between the satellites?

That the satellites can communicate
between each other.

And this is one of the interesting
things - it's autonomous. Yeah.

So, this isn't being controlled
from Earth.

They are speaking to each other,
keeping their distance,

and doing all that remotely.

Literally everything has to
happen remotely,

like, automatically. Yes.

This is also why the testing
has to be so extensive.

We really want to see that the
satellites are able to do it.

Yes. It will be very boring
for us, in the end,

because it will be one command
every week,

to give the satellite the week's
schedule, and that's it.

Marie takes me to the other
satellite,

the one that will block the sun,

to show me how the formation flying
will be achieved.

Now, this is the occulter.
So, what have we got here?

All right.

So, here we have actually
the really, the actual things

that will make it possible to do
formation flying.

OK, perfect.

The first thing they will do
is activate their VBS,

which stands for
visual based sensor. OK.

And this visual based sensor has
two cameras, the wide angle camera

and the narrow angle camera.

So, we call it the WAC and the NAC.
OK, yes.

And the WAC is the one on the right.
OK, yes.

Those are the wide angle cameras.
Right.

Whenever they are active,
they will be looking like this...

..with their wide angle camera
for the other spacecraft.

Yes, the flashing lights
of the other spacecraft? Exactly.

Space is dark,
so if there would be no lights,

this satellite would not be able...

It would be hard to spot them.
Yeah, exactly.

And then, he will switch
to the narrow angle cameras

to make... to go into
the centimetre precision.

You've found each other on the wide.

You've narrowed it down
on the narrow. Exactly, yes.

OK. So, then what happens?

And then, we go into the laser part.

So, we were in centimetre now,
with the narrow angle camera,

and we're going to millimetre
precision,

because we activate the laser.

And the laser is behind that,
like, orange ring.

So, that's actually the
story here of how the formation

will be acquired. Yes.

These are just a few
of the instruments that make up

the two satellites.

And each part will need to be
thoroughly tested

before they're ready to launch.

Marie, thank you so much for giving
us a tour around your babies.

It was lovely. Yes!

And I'm guessing there's a lot
of testing to do.

But, yes, it's going to make sure
that it will work when it gets out

there in space. Definitely.
Me and my team, we will go for it.

Yes!

Good luck with the testing.
Thank you.

And, yeah, we can't wait to see
those first results coming through.

Me neither.

This project feels so revolutionary.

I mean, it's got everything -
from precision formation flying,

autonomous navigation,

and also views of the sun
like we've never seen it before.

So, I'm really hoping that this work
will lead to the next generation

of satellites -
satellites that will explore

our solar system and beyond.

So, I, for one, can't wait
until it's launched.

CHRIS: But while we wait, other
stars have stories to tell us, too.

Pete's off to find out more.

In October 2023, a research paper
confirmed that

two planets had collided.

This was an incredible finding,

and the first time that the remnant
of two planets colliding

had been positively identified.

But incredible though this
discovery was,

what was amazing, for me,
was how the discovery came about.

I am meeting Doctor Simon Lock
and Doctor Zoe Leinhardt

from the University of Bristol...

..and a whole team from across
the world to find out more.

Hello! Hey.

Lovely to meet you all. Wow.

That's a gallery of people.

This gallery of people were all
involved in identifying

two planets colliding.

And the story began when Michael
Rizzo Smith noticed something

unusual happening to the brightness
of a star.

I was working for a team called
the All Sky Automated Survey

for SuperNovae.

And, usually, we're looking for
these very bright events,

but we also catch some events that
change in the opposite direction,

where they get fainter.

We noticed a dimming event,
which was quite unusual. OK.

So, not being an expert in that,
I posted that to sort of a forum,

called the Astronomer's Telegram,
telling people we saw this

sort of interesting object,
with the hopes that someone

would follow up with it.

The Astronomer's Telegram is
a free online publication

where the latest astronomical
observations are quickly reported

to a community of thousands
of professional

and amateur astronomers.

And that caught the interest
of Matt?

Hello. Yes.

So, initially, I thought it was
going to be a big disk,

or a set of rings around a planet
moving in front of the star.

But there was another key piece
of information that came in,

wasn't there, from R2?

Absolutely.

A Finnish amateur astronomer, called
R2 Sainio, tweeted at me and said,

"Hey, didn't your star get very
bright in the NEOWISE survey?"

And I went, "What?"

So, it almost doubled in brightness
in the infrared -

but it happened about 900 days
earlier,

which was completely unexpected.

The bright flash of light
over two years before the star

started dimming led Matt to wonder
if what they were seeing

was caused by debris from
a collision near the star.

Matt got in touch with Zoe and I,
and was like,

"What do you make of this?
Could this be a collision?"

And the more we thought about it,
I think the more convinced

we were that we were looking
at something that was

very consistent with a collision.
Right.

But they needed more data -
and this is when amateur astronomers

and their telescopes got to work.

I have a day job as an engineer.

And I had been
following this object. Right.

I build my own telescopes.

I did try to take a spectrum,
but my telescope isn't big enough.

Unable to get the data needed,
Hamish reached out to Olivier,

who, along with four other
amateur astronomers in France,

remotely operate telescopes
in Chile.

The technical achievement
that Olivier's group did

in actually taking a spectrum
during the dimming.

And their productivity - 10 to 15
spectra a night. Incredible.

I get one or two a night.

That's amazing, utterly amazing.

How many clear nights do you get
throughout the year in Chile?

So, 300 nights of clear skies.

So, based in the UK,
I think it's the other way round.

We probably get 300 nights
of cloudy skies.

Because of the data Olivier
and his team provided,

work by all these people, and more,
proved the dimming star

was actually the result of debris
from the two planets colliding

and eclipsing the star.

This has been an amazing project.

What does it mean for you to have
that amateur input?

This is something which happened
almost purely because

an amateur astronomer tweeted
at us and said,

"Hey, what's going on here?
This looks like your star."

And having this wonderful community
of astronomers all around the globe

is absolutely fantastic.

It's been an absolute privilege
to meet you,

and it's been heart-warming to hear
how amateurs and pros have been

working together to come up
with this amazing discovery.

So, thank you very much,
and goodbye.

MAGGIE: Dimming starlight
can reveal explosive secrets.

But it's by blocking out starlight,

we get to reveal planets
like our own.

Chris is off to find out more.

CHRIS: At the Sharmanka
Kinetic Theatre, in Glasgow,

they use light and shadow
to bring their creations to life.

These are quite impressive
sculptures, with so much detail.

Yeah, there's a few...

I'm here to meet Professor
Beth Biller, from the University

of Edinburgh, to talk about how
shadows that scientists create

can help us find planets
like our own.

Shall we have a look around?
Yeah, let's wander.

Oh, look, there's a telescope.
Nice bit of astronomy.

Beth uses shadows to directly
image exoplanets.

And has a shadow caster of her own
to explain how this can be done.

So, normally, when we think about
exoplanets, we're used to hearing

about discoveries via transits.

How does that work?

Well, we have a demo here that shows
exactly how we detect a planet

via transit.
So, if this is our planet,

and we have the right alignment,

when the planet passes between us
and the star,

it's going to dim just a tiny
bit of the starlight.

And we can look at the star.

And if we see that dimming in the
very characteristic shape

of a transit, we know the planet
is there.

And, ideally, you'd see transit
after transit after transit,

and be able to pick this up?

Yes, and they would, of course,
happen exactly once each orbit.

But you can't do everything
that way. Why not?

Well, while transit is an incredibly
powerful technique

for finding planets, first you have
to have a planet that transits.

So only about 10% of exoplanets
are actually going to have

a transit from our perspective.

So this is where
there's other techniques,

so for instance, direct imaging.

But it's not as simple
as just taking a picture.

No, I mean, the big issue is stars
are very bright

and planets are comparatively faint.

So you need to go through many steps
to block out the starlight

before you're going to be able
to see faint planets

next to a very bright star.

So how does that work?
How does this coronagraphy work?

So the simple part is you block out
the star. OK.

You put a disk over the star.

So I can use the demo we use to show
transiting planets before.

Adapt it a little bit
to be a coronagraph.

So instrument construction
in real time.

Real time instrument
construction. Nice!

Our star is now a very long distance
away from our observer over there,

so we just need to line it up
in such a way that we block out

the starlight, revealing
any faint planets orbiting the star.

And there they are,
revealed by the coronagraph.

Using this method, JWST is already
providing images of exoplanets,

but they're all very young compared
to our own solar system.

Why does the age of the planet
make a difference?

So a young planet which is just
formed is still quite warm,

and that means it's glowing
a lot brighter

than it will at those later ages.

And that means that the contrast
ratio between the star

and that planet is much
more favourable compared

to if you look at planets
like the ones in our solar system,

which are very, very cold
comparatively, and don't put a lot

of their own light, we have to look
at them via the light

that they reflect from our own sun.

But with the Nancy Grace Roman Space
Telescope

scheduled for launch in 2027,

we will hopefully be able
to see older exoplanets

providing a step towards finding
Earth's twin.

So what planets will Roman let
us see that we can't see today?

Roman will really let us start
pushing down to colder planets,

older planets, specifically planets
that we've likely

detected already via other methods.

That would be cool. So planets that
we know are there,

but we've never seen, being able
to picture them would be fabulous.

Exactly. And that means that we can
start studying their atmospheres

and really understanding
how they work, physically.

But these will be
the larger outer planets,

the equivalent of our own Jupiter.

It will take another technological
leap before we get to planets

like our own.

I know all exoplanets are special,
but people want to think about

Earth-sized planets in Earth-like
orbits around Sun-like stars.

Is there any prospect
of ever getting an image of one

of those through this
direct imaging technique?

To get to true Earth twins is going

to take the next large space
telescope,

but this is now on the horizon with

the Habitable Worlds Observatory.

And this is planned
currently for the 2040s, 2050,

but people are working on it now.

It shows how fast this is moving.

We've gone from just having a
handful of directly imaging planets

to this being really
mainstream exoplanet science.

Right now, we're in the golden era
of transits, and there's so much

being done with that and thousands
of planets detected via transit.

But I really think in the next
10 or 20 years, direct imaging

is going to catch up and we're going
to have a lot more detections

of a lot wider range of planets.

It's exciting stuff.

It's amazing what you can do
with a coronagraph and the shadows

that it causes. Thank you very much.

DR MAGGIE: Well, the search
continues for exoplanets

similar to those in our
solar system.

Pete is looking at our local planets
that can be seen in our skies

even when the sun is bright.

When you think about observing
the planets, you generally think

about looking at them at night.

But there are some which can be seen
during the day as well.

Obviously not today thanks
to the clouds, but if you are going

out with a telescope during the day,
the first thing to consider

is to avoid the sun.

You should never look directly
at the sun or near the sun

unless you're using appropriate
certified solar safety filter.

The general rule is if you're unsure
about what you're doing,

don't do it.

This month, Mercury is at a great
position to observe during the day,

and that's because it has
a reasonable distance

from the sun's glare, which will
allow you to observe

it under relative safety.

If you are an astronomer

with experience of viewing the sun,

then it should be possible to view

a conjunction, or meeting,

between Mercury and Jupiter,

which takes place
on the 4th of June,

both planets being at their closest

in daylight around 11.30 BST.

This will require care to see,

though, as both objects will only

be separated by just over

a fist's width at arm's length

from the sun.

As a consequence, this is only

suitable for observing via a camera,

and full solar safety procedures

are required,
so please do be careful

and only try this out

if you can do so safely.

To find Mercury in the daylight sky
this month, there are a number

of strategies you can use.

The easiest method is to get
up early and find Mercury

in the pre-sunrise dawn sky.

If you locate it, centre
up on it and keep with it.

After the sun has risen

until Mercury is in a higher part

of the sky.

Another way of doing it is
if you've got a Go-To mount,

which will allow you to synchronise
on the sun.

So basically what you do for this
is you put your solar filter

over the front of your telescope
to make sure it's protected,

and then you remove any finders,
etc, which are attached

to the telescope for safety.

You point the telescope at the sun
and then with the Go-To system

you synchronise on that position.

Once you've done that,
all you have to do is go,

"go to Mercury"
and it'll find it for you.

Couldn't be easier.

As well as Mercury, the moon
will be visible in the day

for much of the month.

You'll notice that daylight
does have a detrimental effect,

it reduces the contrast of the view.

Again, if you're using binoculars,
please take extra care to make sure

you stay well away from the sun.

As an astrophotographer, finding
the thinnest of lunar crescents

in the evening or morning twilight
is something which gives me

great pleasure because it's actually
quite a tricky thing to do.

The next New Moon will be on the 6th
of June, and there are opportunities

to capture thin moons
on the mornings of

the 4th and 5th of June,

low above a flat northeast horizon
before sunrise...

..and on the evenings
of the 7th and 8th of June,

low above a flat
northwest horizon following sunset.

So do have a go, and if you get any
that you're happy with, do upload

them to our Sky At Night Flickr and
we'll pick some of our favourites

and show them in next month's show.

In the meantime, these are some
of our favourites of the eclipse

that you've been uploading
this month.

CHRIS: As far as we know,
none of the millions of planets

around the millions of stars
in the Milky Way have anything

as spectacular as a total eclipse.

But what is clear is that our
exploration has just started,

so who knows what we might find.

Goodnight.