The Mystery of 'Oumuamua The Sky at Night

Last October, astronomers made a spectacular discovery.

For the very first time,

they spotted an object visiting our solar system from outer space.

It set off a hurricane of press speculation.

Tonight, we have new, exclusive revelations

and reveal the complete story of this mysterious visitor,

which now goes by a suitably exotic name -

'Oumuamua.

To tell this detective story, I've come here to Belfast,

which has become the centre of research into

this cosmic visitor -

an object called 'Oumuamua.

When we first saw it, all we knew was that it was small

and moving fast. The first object from deep space ever to be seen

passing through our solar system.

And its sudden appearance raised a whole host of questions.

What did it look like? How had it formed?

What was it made of? And where had it come from?

To answer these questions,

I'm going to piece together all the clues that scientists were able

to extract from the small amount of data that they gathered as 'Oumuamua

flashed through the solar system.

This forensic analysis, including new, exclusive revelations,

will give us the most comprehensive picture yet

of this extraordinary object.

Our story starts in Hawaii in mid-October last year,

when one of the biggest telescopes in the world

spotted something unusual.

Now, this is the first picture taken

of 'Oumuamua from the telescope in Hawaii.

Looking at it, it's quite hard to spot

but it's actually this splodge here.

Now, you can tell it's moving really fast

because the stars appear as points,

whereas this is a blur across the screen.

I called Karen Meech in Hawaii, who led the team that night,

to find out how the discovery was made.

Hi, Karen. Nice to meet you and thank you for waking up so early.

-No problem.

-Now, can you take us

through the night of the first observation?

Well, this was discovered by the Pan-STARRS telescope in Hawaii,

which is conducting a Nasa-funded search

for near-Earth objects.

And this particular night, on the 19th of October,

one of the objects that was flagged

had a very long streak, which meant it was moving quite fast.

So, what had you effectively discovered by then?

Well, at that point, people weren't sure.

But as soon as some follow-up observations came in,

one of the groups at the European Space Agency ground station reported

that the orbit looked interesting.

Namely, they said its shape didn't look circular.

And it wasn't until a few more nights of data came in

that we decided that this was definitively

something from outside the solar system.

How did you feel when you found out that it was an extrasolar object

coming from another solar system?

I actually sat there for a while just thinking about

what it meant and getting more and more excited

that this really is the first time we have

something so close that's delivered from outside.

The frustrating thing was that it was moving so fast.

We only had a little over a week

during which time it was bright enough to

actually do the experiments we'd like to do.

So, what that really meant was a team of people

were working around the clock and I ended up sleeping in the office

for most of the week, because we were putting in 18-hour workdays.

How do you go about naming these objects?

We thought it might be nice to have a Hawaiian name.

And so the director suggested that we talk to

a Hawaiian navigator and a Hawaiian linguistics expert

on the Big Island. And they suggested a very nice name to us.

It was 'Oumuamua, where the O means "to reach out for",

and "mua" means "first" or "in advance of",

and by duplicating that piece, it gives it emphasis in Hawaiian.

So, the intent of their definition was that

this is a scout or distant messenger

sent out from our beginnings to reach out to us

or build connections with us,

so we thought it was a very appropriate name.

Thank you so much, Karen.

It's a fascinating story and I'm looking forward to finding out more.

Well, thank you.

Karen's discovery caught the imagination of scientists

around the world.

First indications were that 'Oumuamua

was just a few hundred metres across

and was travelling at over 50km per second.

But the big story was about its origins.

Within days, scientists had gathered enough data to start working out

the trajectory of 'Oumuamua.

Now, initially they assumed that it was an elliptical orbit.

But just days later, they realised it wasn't an orbit at all.

It was actually open.

Now, this flagged up all sorts of questions,

because it meant that 'Oumuamua didn't originate

from within our solar system.

More importantly,

they'd only spotted it as it made its journey outward

from the solar system. That meant they had a limited time

to gather more data to find out what it was like, how it was made,

and where it had come from.

By late October, astronomers in Belfast

and around the world were getting excited.

Michele Bannister's team were among the first to take on the quest

to understand 'Oumuamua.

They focused on what it looked like,

what shape it was, and - crucially - what colour.

So, you did what astronomers have always done,

which is ask simple questions like, "What colour is it?"

That can often tell us a lot.

Yeah. So, we're seeing this object

entirely with reflected sunlight.

And so the colour that you get

of the reflected surface tells you about

potentially what the composition is.

And, so, what colour is it?

It's a touch redder than sunlight, but kind of pinky.

However, you wouldn't see that if you were to look at 'Oumuamua

with your naked eye, rather than with one of the world's biggest

telescopes, because when it reflects the sun's light,

it's reflecting it back at almost the same colour as the sun.

Just a bit redder in the infrared part of the spectrum.

This colour, a hint of pink or red

especially noticeable in the infrared,

is reminiscent of some objects in our own solar system.

It could actually be a little cousin of one of the objects that you see

in the populations known as Jupiter Trojans,

which orbit out near Jupiter.

Another thing your observations showed was that the brightness of

the object was changing over time.

Yes, we observed for about two hours.

So, if I show you here...

So, this gives you some idea of how

the brightness that we measured

-changed over time.

-You've got this

really quite dramatic dip here. It faces quite dramatically,

-and then recovers.

-It changes in brightness

over a remarkable amount of contrast

and we weren't expecting that. That was great.

What do we think causes that variation?

Probably the shape of the object.

So, I have a way of showing you what effect shape is going to have on

-the brightness of an object over time.

-OK.

So, here I have a sun...

-OK.

-Here I have a turntable that is rotating an object over time.

-OK.

-So, the camera is watching this object and it can't see the shape of

the object directly. It's just going to see its brightness.

On the screen here, you see what the camera is measuring of how it sees

this little object changing in brightness over time as it rotates.

Now, the sphere - you can see you don't get much change

-in brightness at all.

-No.

Let's try this with something a bit stranger in shape.

OK, I'll remove the sphere. There we go.

Instead, put on this delightful potato asteroid here.

-Fine.

-And you can see what the camera is seeing

as this point of light changes in brightness

as it turns, is when the short end is pointing towards the camera...

-Like it is now.

-..you have minimum surface area being reflected,

the light, so it's dimmest. And when it turns round

and the whole side of this object is being illuminated,

it's the brightest to the camera,

and so you see this brightness peak.

And what do you find? What shape is 'Oumuamua?

It's actually got to be even more elongated than this little potato.

This is 3:1. 'Oumuamua has to be at least 5:1,

maybe even a bit longer.

But this is the thing, when I saw this result

from all this hard work of astronomers

scrambling to telescopes, it seems to me very unlikely

that the first interstellar visitor would be this unusual.

Is that something that disturbs you,

or does this make sense if you've been thinking about these things?

The shape is a bit unusual,

but the colour is so much like what we see in our own solar system.

There's a kinship there. It tells you that something that formed

around a different star and something that formed

around our own star have a lot of similarity in their surface.

It's a very deep thought, that.

It's sort of a poetic... It's scientific, but it's poetic as well,

that there is this relationship

to something that came from so far away.

Yeah, we're finally getting to touch something that's from

another solar system that's larger than a grain of dust.

Within days of being spotted,

detailed information about 'Oumuamua was coming in.

From Michele's light analysis, a shape was proposed.

It was thought to be an elongated cigar shape,

100 to 400 metres in length.

The ratio of length to width was thought to lie

between 10:1 and 5:1.

And although it was dark, it seemed to have a touch of pink or red.

By the end of November,

the strange shape and exotic nature of 'Oumuamua had led to some

extraordinary speculations.

Was 'Oumuamua an alien artefact?

It wasn't an entirely stupid question.

'Oumuamua was so strange

that at this stage almost anything seemed possible.

So I met astrophysicist and expert in the search for extraterrestrials

Duncan Forgan, to find out how scientists deal with the question of

whether an object is natural or alien.

So, Duncan, all this very interesting data was coming through,

what was the press's response to it?

It was a little bit frenzied, to be honest.

There were a lot of stories about this idea that maybe this

weird interstellar visitor was, in fact,

an alien spacecraft coming to visit the Earth.

But, unfortunately, a lot of that stuff was very overbaked.

So, how should scientists treat these stories?

I think it's important to make sure that when you're thinking about,

"What is this new, interesting, weird thing?"

you make your list of natural explanations,

-and then right at the very bottom you put the aliens explanation.

-OK.

And you wait until you've exhausted all the natural explanations.

And then, when nothing else is left, Sherlock Holmes-style,

you come back to the aliens explanation.

So, one of the things that we did was to basically check

if 'Oumuamua was a transmitter.

So, they wanted to see if it was emitting radio waves

in the way that we'd expect a radio transmitter

built by an intelligent being to work,

so they pointed their radio telescopes at 'Oumuamua

and checked and found nothing.

So, what would you have done if it was found out that 'Oumuamua

was an alien artefact?

There are a list of protocols that people who are doing the search

for intelligent life are supposed to follow -

what they call a post-detection protocol, so what do you do next?

And so one of the things you need to do is A - check your answer,

-because if you get this wrong it could be very embarrassing.

-Yes.

So, ask your colleagues to use a different instrument and try and do

the same experiment and if it comes out to be the same answer

then, OK, you've got something there. And then get more and more

people to check and make sure that your hypothesis has been validated.

And then you go to United Nations and tell the Secretary General,

"By the way, there's alien life and it's coming towards us."

-An interesting e-mail!

-Yeah.

And then you're supposed to tell the public at large.

-Well, thank you so much. It's been fascinating.

-Thank you.

In mid-December, the mysteries about 'Oumuamua were still mounting,

and scientists were beginning to wonder just where it had come from.

Michele Bannister picks up the story.

So, this brings me to the next question I wanted to ask, which is -

do we know where this asteroid, this body, came from?

It seems to me you've seen it coming in, so can we trace it back?

That will be a work in progress.

What we can do is say the arc that it took as it came into

the solar system, if we extend that back and back and back

for 100 million years...

You know, that's the better part of halfway round the galaxy

-as the sun's travelling.

-OK, so we've travelled a long way,

-this thing's been moving, it's complicated.

-Yeah.

You have to run the galaxy backwards in time and say,

"Where were all the stars millions and millions of years ago?"

And then say, "Was 'Oumuamua close to one of these stars?"

And if it was, that's its last port of call.

Now, that's not the same thing as saying that's where it's from.

-No.

-Because the next star system that 'Oumuamua goes through,

it'll look like it came from us.

That's true. People will trace...

Aliens will trace it back and think it came from here.

But people have tried to match this trajectory,

to do this difficult calculation - how have they got on?

You can see it comes not close-close,

but perhaps a little bit close to some stars.

There's about 15 stars that are currently potential candidates that

it could've come near in that time.

But everything starts getting a little fuzzy, because we don't

actually know the positions of these stars particularly well.

About five of them are in a group of stars

loosely called the Local Association.

It's an amazing thought that it might be bouncing around

and, of course, it may encounter other stars in the future.

It has a long journey to go.

-Michele, thank you very much.

-Thank you, Chris.

So tracking 'Oumuamua's orbit back through time and space has suggested

that it might come from a group of stars that astronomers call

the Local Association.

You might think that the Local Association would be a nice, neat

little cluster of stars in the night sky, but it isn't that simple.

Although they all formed around the same place

and at around the same time,

just 100 million years ago, they have since spread out.

Pete Lawrence explores this Local Association,

starting by looking towards the southern part of the sky.

The Local Association

is roughly in this direction here.

Most of the stars in it are too dim to be seen

with the naked eye, but it does include one of my favourite

open clusters, the Pleiades.

The Pleiades are some of our closest neighbours,

at a distance of 440 light years.

They're very distinctive, like a miniature Plough.

To locate them, find Orion in the southern sky

and follow the line of the belt up and to the right,

past Taurus and its distinctive V,

and then continue the line.

You should see a little huddle

of beautiful blue-white stars.

These really are one of the highlights of the winter night sky,

looking like rare jewels on black velvet.

But binoculars or a telescope will show even more.

And photography reveals an exquisite blue nebula,

visible because of light reflecting off of a cloud of dust

that the stars are moving through.

Associations like this are often hundreds of light years across.

For instance, there's another star in the association, which you can

find by heading southeast from the Pleiades

so that you're on the other side of Orion, the Hunter.

So a fair distance away.

Here you're in the constellation of Monoceros, the unicorn.

And there's a faint star there

which is a candidate for the origin of 'Oumuamua.

The star is called Ross 614.

You'll need a telescope to see it,

but to find it go back to Orion and head south and east.

Monoceros, or the unicorn,

is a group of fairly dim stars

between Canis Major and Canis Minor.

And Ross 614 is about

halfway along his front leg.

And it's in this group...

Oh, there it is!

It's just 13 light years away and is a component

in a red-dwarf binary system.

And it's fascinating and really exciting to think that may be

where 'Oumuamua came from.

By now, scientists had worked out quite a bit about 'Oumuamua.

They knew its rough size, speed and colour.

And if it did come from the Local Association,

they knew its age, too -

100 million years,

when these stars were formed.

But two big mysteries remained.

What was it made of and how was it formed?

Back in Belfast, Chris met up with Alan Fitzsimmons,

who started to investigate 'Oumuamua's composition.

His team believed it was icy, like most small distant objects.

But all the images they collected told a different story.

Because, if it was icy, why didn't it have a tail?

And so you got those images back and you were expecting to see what?

A comet with a nice tail, I guess.

That's right. This object passed pretty close to the sun,

and so the ices there should have been heated

and we should have seen that material expanding

away to form the atmosphere of the comet and the tail,

but there was nothing like that.

It looked like an asteroid, and so we were thinking,

"What is this thing?"

What did you do next?

The important thing then was to figure out how this object was

reflecting light because that could give us to a clue

to what it was made of. To do that,

we needed to get spectroscopy of the object.

So, what did the spectrum show?

Well, we saw the signature of carbon.

-Carbon?

-Yeah.

Now, when we think of an icy comet,

we think of something that's mostly made of water ice,

although there may be some carbon monoxide and carbon dioxide.

This is an object that could have been out there between the stars for

millions or billions of years.

And so it's been sitting out there and during that time

it's been affected by the cosmic rays,

high-energy particles that fill our galaxy.

OK, so it's the cosmic rays that might have changed the surface.

-What would they have done to it?

-They take those ices on the surface,

and in particular they take the carbon,

and the carbon rearranges itself

to form new molecules and new compounds.

And so what does that look like? How can we see what's happening?

I can explain using this demo, now...

-OK.

-Basically a meringue - egg whites and sugar - OK?

And we can add some energy. Now, we're not going to use cosmic rays.

We're going to use a little blowtorch here.

-OK. Well, safety first.

-Safety first indeed.

I do this every time I cook, you know. Very sensible. OK.

-There we go.

-And now,

if we add energy to that we'll see a chemical transformation

to a different substance.

It's a very different material on the surface,

with the meringue intact inside.

Now... This is great cooking,

but what's this got to do with an interstellar asteroid

-or interstellar comet?

-Well, instead of egg whites, of course,

and sugar, we have ice, we believe, that we start off with.

And instead of a blowtorch,

we have energy deposited on the surface by cosmic rays.

But only on the surface?

That's right. Now, over about 100 million years,

this chemical transformation can go down about half a metre or so.

Within that depth, we could still have ice there.

And the important thing is this not only changes the surface properties

and how it reflects light, this new crust of carbon-based material

also insulates the interior.

So it locks in, perhaps, the ice that's still there.

That's right, and when we do the calculations we find that

even though 'Oumuamua passed within the orbit of Mercury,

passed very close to the sun,

that heat from the sun could not have penetrated

within more than half a metre.

So the ice would have remained locked up

and that explains why we didn't see a comet,

we saw something that looked initially like an asteroid.

We'll look forward to hearing about whatever comes next.

-Alan, thank you very much.

-Thank you.

By Christmas, scientists had a pretty good understanding

what 'Oumuamua was made of. But then came a new and exciting discovery -

revealed tonight for the very first time.

A powerful new theory started to emerge,

based on a detailed analysis of the light reflected off 'Oumuamua.

It suggested not just how it was formed, but also where it came from.

To find out more,

Chris met lead scientist on this new research Wes Fraser.

So, Wes, taking a close look at this thing,

it turns out to be even more complicated than we thought.

-What's going on?

-Well, I was weirded out by the fact

that no-one publishing all these papers coming out of 'Oumuamua

could actually determine how quickly it was rotating.

And so one morning, one Friday morning, I just thought,

"I'm just going to pull all of this together and see what I can see.

"Now that we've got many days' worth of observations,

"surely we can pull all of this data together and just figure out how quickly this thing is spinning."

Wes's new investigation compares the light we might expect

from a spinning object, shown with the dotted line,

with the data that Wes actually gathered.

So, if you look at the plot here,

it works in some places,

but it completely fails in others -

where the curve is low,

the data are high.

-Yeah, yeah. Look, down here in day five - it's way off.

-Yes, exactly.

Or even in the first couple of days, there's something odd going on.

It was exactly the comparison between night two and night five

that really... "OK, there's something weird going on here."

-OK.

-And so we started to look at it a little bit,

and it was very clear that, in fact, this thing is tumbling.

So, what do you mean by "tumbling"?

Tumbling is an unusual state of rotation.

We can demonstrate this with a simple ping-pong paddle.

So, when we throw it like this...

..just spins on a single axis and it remains that way.

But when we throw it like this...

..it immediately enters tumbling.

It spins like this at the start,

but then quickly starts to wobble around chaotically.

And that's what we call tumbling.

This thing's been travelling in space for a long time.

How does it end up tumbling like this?

We think it was due to a collision.

And so at some early stage of its life,

it was just spinning normally like everything else

and then it suffered a collision.

That would impart enough energy on one particular spot

in such a way as to then be confused in how it spins.

And so where would that have happened? Out in empty space?

No, so we can pretty safely assume that the collision that caused this

thing to tumble was in its original stellar system,

before it got kicked out.

So this thing's carrying information

-about the early days of a different solar system?

-In a way, yeah.

It's hard to know if it was during planet formation

or after the planet formation process.

Certainly more collisions happen while planets

are growing than afterwards, so that's a very good guess.

It now seems that Wes's result may tell us something profound.

'Oumuamua could be a relic from the formation of another solar system.

There is a chance that this tumbling occurred while planets were forming,

and so this is actually a moderately violent process.

So you can produce, you know, rocks and boulders and pebbles this way,

but eventually you do produce the planets in the process.

At that point, those collisions become violent and very destructive.

This may very well be where 'Oumuamua's shape has come from.

It's most likely where its tumbling has come from as well.

And we do know that objects are kicked out of our solar system,

as well - they have been and continue to do so.

So, while this is a bit of space that has, you know,

come its way to us, we are of course sending bits of ourselves naturally

to other places as well in a similar way.

You make it sound like the galaxy's full of these things.

Must be. Very, very much so.

-Yes.

-So, how come this is the first one we've seen?

How many more are there that we're missing?

Our best guess at the moment -

and this is pretty uncertain cos we've only ever seen one -

but our best guess is, at least within our own solar system,

there are about 10,000 of these currently passing

-within the orbit of Neptune.

-There are 10,000 of these...

-That's right.

-..going through the solar system today?

-Today.

-Not this year, not...

-Yep.

-So, why don't you see them?

For every one of those that we see, there's 10 or 100 that we miss.

And that just because of the fact that they're moving.

And so it was a fantastic job of the discoverers to find this thing.

-It's a fantastic discovery.

-Well, lots more to look forward to...

-Yes, indeed.

-..and it will be intriguing to find out

-whether this one is particularly unusual.

-That's right.

-Wes, thank you very much.

-Thank you.

The discovery of 'Oumuamua

has been one of the great scientific stories of the last 12 months.

This is our first deep-space object.

And this is now the most complete picture we have of 'Oumuamua.

It's now suggested that 'Oumuamua's origins

lay in the chaos of planetary formation...

..around a distant star...

..perhaps 100 million years ago.

That's it from Belfast for this month

and we're taking a break next month, but we'll be back in April.

In the meantime, don't forget to check out our website

for Pete's star guide and for our special weekly weather forecast.

And, of course, get outside and get looking up. Goodnight.