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Last October, astronomers made a spectacular discovery. | 0:00:02 | 0:00:07 | |
For the very first time, | 0:00:07 | 0:00:08 | |
they spotted an object visiting our solar system from outer space. | 0:00:08 | 0:00:13 | |
It set off a hurricane of press speculation. | 0:00:15 | 0:00:18 | |
Tonight, we have new, exclusive revelations | 0:00:23 | 0:00:26 | |
and reveal the complete story of this mysterious visitor, | 0:00:26 | 0:00:30 | |
which now goes by a suitably exotic name - | 0:00:30 | 0:00:34 | |
'Oumuamua. | 0:00:34 | 0:00:35 | |
To tell this detective story, I've come here to Belfast, | 0:01:09 | 0:01:12 | |
which has become the centre of research into | 0:01:12 | 0:01:15 | |
this cosmic visitor - | 0:01:15 | 0:01:16 | |
an object called 'Oumuamua. | 0:01:16 | 0:01:20 | |
When we first saw it, all we knew was that it was small | 0:01:20 | 0:01:23 | |
and moving fast. The first object from deep space ever to be seen | 0:01:23 | 0:01:27 | |
passing through our solar system. | 0:01:27 | 0:01:30 | |
And its sudden appearance raised a whole host of questions. | 0:01:30 | 0:01:33 | |
What did it look like? How had it formed? | 0:01:34 | 0:01:38 | |
What was it made of? And where had it come from? | 0:01:38 | 0:01:42 | |
To answer these questions, | 0:01:42 | 0:01:44 | |
I'm going to piece together all the clues that scientists were able | 0:01:44 | 0:01:48 | |
to extract from the small amount of data that they gathered as 'Oumuamua | 0:01:48 | 0:01:52 | |
flashed through the solar system. | 0:01:52 | 0:01:55 | |
This forensic analysis, including new, exclusive revelations, | 0:01:55 | 0:01:59 | |
will give us the most comprehensive picture yet | 0:01:59 | 0:02:02 | |
of this extraordinary object. | 0:02:02 | 0:02:04 | |
Our story starts in Hawaii in mid-October last year, | 0:02:07 | 0:02:11 | |
when one of the biggest telescopes in the world | 0:02:11 | 0:02:14 | |
spotted something unusual. | 0:02:14 | 0:02:15 | |
Now, this is the first picture taken | 0:02:19 | 0:02:20 | |
of 'Oumuamua from the telescope in Hawaii. | 0:02:20 | 0:02:24 | |
Looking at it, it's quite hard to spot | 0:02:24 | 0:02:26 | |
but it's actually this splodge here. | 0:02:26 | 0:02:29 | |
Now, you can tell it's moving really fast | 0:02:29 | 0:02:32 | |
because the stars appear as points, | 0:02:32 | 0:02:34 | |
whereas this is a blur across the screen. | 0:02:34 | 0:02:36 | |
I called Karen Meech in Hawaii, who led the team that night, | 0:02:42 | 0:02:46 | |
to find out how the discovery was made. | 0:02:46 | 0:02:48 | |
Hi, Karen. Nice to meet you and thank you for waking up so early. | 0:02:50 | 0:02:52 | |
-No problem. -Now, can you take us | 0:02:52 | 0:02:54 | |
through the night of the first observation? | 0:02:54 | 0:02:57 | |
Well, this was discovered by the Pan-STARRS telescope in Hawaii, | 0:02:57 | 0:03:01 | |
which is conducting a Nasa-funded search | 0:03:01 | 0:03:04 | |
for near-Earth objects. | 0:03:04 | 0:03:06 | |
And this particular night, on the 19th of October, | 0:03:06 | 0:03:10 | |
one of the objects that was flagged | 0:03:10 | 0:03:12 | |
had a very long streak, which meant it was moving quite fast. | 0:03:12 | 0:03:17 | |
So, what had you effectively discovered by then? | 0:03:17 | 0:03:20 | |
Well, at that point, people weren't sure. | 0:03:20 | 0:03:22 | |
But as soon as some follow-up observations came in, | 0:03:22 | 0:03:27 | |
one of the groups at the European Space Agency ground station reported | 0:03:27 | 0:03:33 | |
that the orbit looked interesting. | 0:03:33 | 0:03:35 | |
Namely, they said its shape didn't look circular. | 0:03:35 | 0:03:39 | |
And it wasn't until a few more nights of data came in | 0:03:39 | 0:03:43 | |
that we decided that this was definitively | 0:03:43 | 0:03:46 | |
something from outside the solar system. | 0:03:46 | 0:03:48 | |
How did you feel when you found out that it was an extrasolar object | 0:03:48 | 0:03:52 | |
coming from another solar system? | 0:03:52 | 0:03:54 | |
I actually sat there for a while just thinking about | 0:03:54 | 0:03:58 | |
what it meant and getting more and more excited | 0:03:58 | 0:04:01 | |
that this really is the first time we have | 0:04:01 | 0:04:03 | |
something so close that's delivered from outside. | 0:04:03 | 0:04:07 | |
The frustrating thing was that it was moving so fast. | 0:04:07 | 0:04:11 | |
We only had a little over a week | 0:04:11 | 0:04:12 | |
during which time it was bright enough to | 0:04:12 | 0:04:15 | |
actually do the experiments we'd like to do. | 0:04:15 | 0:04:17 | |
So, what that really meant was a team of people | 0:04:17 | 0:04:20 | |
were working around the clock and I ended up sleeping in the office | 0:04:20 | 0:04:24 | |
for most of the week, because we were putting in 18-hour workdays. | 0:04:24 | 0:04:27 | |
How do you go about naming these objects? | 0:04:27 | 0:04:29 | |
We thought it might be nice to have a Hawaiian name. | 0:04:29 | 0:04:32 | |
And so the director suggested that we talk to | 0:04:32 | 0:04:36 | |
a Hawaiian navigator and a Hawaiian linguistics expert | 0:04:36 | 0:04:40 | |
on the Big Island. And they suggested a very nice name to us. | 0:04:40 | 0:04:44 | |
It was 'Oumuamua, where the O means "to reach out for", | 0:04:44 | 0:04:50 | |
and "mua" means "first" or "in advance of", | 0:04:50 | 0:04:52 | |
and by duplicating that piece, it gives it emphasis in Hawaiian. | 0:04:52 | 0:04:57 | |
So, the intent of their definition was that | 0:04:57 | 0:04:59 | |
this is a scout or distant messenger | 0:04:59 | 0:05:02 | |
sent out from our beginnings to reach out to us | 0:05:02 | 0:05:05 | |
or build connections with us, | 0:05:05 | 0:05:06 | |
so we thought it was a very appropriate name. | 0:05:06 | 0:05:08 | |
Thank you so much, Karen. | 0:05:08 | 0:05:10 | |
It's a fascinating story and I'm looking forward to finding out more. | 0:05:10 | 0:05:14 | |
Well, thank you. | 0:05:14 | 0:05:15 | |
Karen's discovery caught the imagination of scientists | 0:05:18 | 0:05:21 | |
around the world. | 0:05:21 | 0:05:22 | |
First indications were that 'Oumuamua | 0:05:25 | 0:05:27 | |
was just a few hundred metres across | 0:05:27 | 0:05:30 | |
and was travelling at over 50km per second. | 0:05:30 | 0:05:33 | |
But the big story was about its origins. | 0:05:36 | 0:05:39 | |
Within days, scientists had gathered enough data to start working out | 0:05:41 | 0:05:45 | |
the trajectory of 'Oumuamua. | 0:05:45 | 0:05:48 | |
Now, initially they assumed that it was an elliptical orbit. | 0:05:48 | 0:05:51 | |
But just days later, they realised it wasn't an orbit at all. | 0:05:52 | 0:05:56 | |
It was actually open. | 0:05:56 | 0:05:58 | |
Now, this flagged up all sorts of questions, | 0:05:58 | 0:06:01 | |
because it meant that 'Oumuamua didn't originate | 0:06:01 | 0:06:04 | |
from within our solar system. | 0:06:04 | 0:06:05 | |
More importantly, | 0:06:05 | 0:06:07 | |
they'd only spotted it as it made its journey outward | 0:06:07 | 0:06:10 | |
from the solar system. That meant they had a limited time | 0:06:10 | 0:06:13 | |
to gather more data to find out what it was like, how it was made, | 0:06:13 | 0:06:17 | |
and where it had come from. | 0:06:17 | 0:06:18 | |
By late October, astronomers in Belfast | 0:06:23 | 0:06:25 | |
and around the world were getting excited. | 0:06:25 | 0:06:28 | |
Michele Bannister's team were among the first to take on the quest | 0:06:28 | 0:06:31 | |
to understand 'Oumuamua. | 0:06:31 | 0:06:34 | |
They focused on what it looked like, | 0:06:35 | 0:06:37 | |
what shape it was, and - crucially - what colour. | 0:06:37 | 0:06:40 | |
So, you did what astronomers have always done, | 0:06:42 | 0:06:44 | |
which is ask simple questions like, "What colour is it?" | 0:06:44 | 0:06:48 | |
That can often tell us a lot. | 0:06:48 | 0:06:49 | |
Yeah. So, we're seeing this object | 0:06:49 | 0:06:51 | |
entirely with reflected sunlight. | 0:06:51 | 0:06:53 | |
And so the colour that you get | 0:06:53 | 0:06:55 | |
of the reflected surface tells you about | 0:06:55 | 0:06:58 | |
potentially what the composition is. | 0:06:58 | 0:07:00 | |
And, so, what colour is it? | 0:07:00 | 0:07:02 | |
It's a touch redder than sunlight, but kind of pinky. | 0:07:02 | 0:07:05 | |
However, you wouldn't see that if you were to look at 'Oumuamua | 0:07:05 | 0:07:08 | |
with your naked eye, rather than with one of the world's biggest | 0:07:08 | 0:07:11 | |
telescopes, because when it reflects the sun's light, | 0:07:11 | 0:07:15 | |
it's reflecting it back at almost the same colour as the sun. | 0:07:15 | 0:07:18 | |
Just a bit redder in the infrared part of the spectrum. | 0:07:18 | 0:07:21 | |
This colour, a hint of pink or red | 0:07:25 | 0:07:27 | |
especially noticeable in the infrared, | 0:07:27 | 0:07:30 | |
is reminiscent of some objects in our own solar system. | 0:07:30 | 0:07:33 | |
It could actually be a little cousin of one of the objects that you see | 0:07:36 | 0:07:41 | |
in the populations known as Jupiter Trojans, | 0:07:41 | 0:07:44 | |
which orbit out near Jupiter. | 0:07:44 | 0:07:45 | |
Another thing your observations showed was that the brightness of | 0:07:45 | 0:07:48 | |
the object was changing over time. | 0:07:48 | 0:07:50 | |
Yes, we observed for about two hours. | 0:07:50 | 0:07:53 | |
So, if I show you here... | 0:07:53 | 0:07:55 | |
So, this gives you some idea of how | 0:07:55 | 0:07:57 | |
the brightness that we measured | 0:07:57 | 0:07:58 | |
-changed over time. -You've got this | 0:07:58 | 0:08:00 | |
really quite dramatic dip here. It faces quite dramatically, | 0:08:00 | 0:08:03 | |
-and then recovers. -It changes in brightness | 0:08:03 | 0:08:05 | |
over a remarkable amount of contrast | 0:08:05 | 0:08:07 | |
and we weren't expecting that. That was great. | 0:08:07 | 0:08:10 | |
What do we think causes that variation? | 0:08:10 | 0:08:12 | |
Probably the shape of the object. | 0:08:12 | 0:08:14 | |
So, I have a way of showing you what effect shape is going to have on | 0:08:14 | 0:08:18 | |
-the brightness of an object over time. -OK. | 0:08:18 | 0:08:20 | |
So, here I have a sun... | 0:08:20 | 0:08:22 | |
-OK. -Here I have a turntable that is rotating an object over time. | 0:08:22 | 0:08:26 | |
-OK. -So, the camera is watching this object and it can't see the shape of | 0:08:26 | 0:08:29 | |
the object directly. It's just going to see its brightness. | 0:08:29 | 0:08:32 | |
On the screen here, you see what the camera is measuring of how it sees | 0:08:32 | 0:08:37 | |
this little object changing in brightness over time as it rotates. | 0:08:37 | 0:08:41 | |
Now, the sphere - you can see you don't get much change | 0:08:41 | 0:08:43 | |
-in brightness at all. -No. | 0:08:43 | 0:08:46 | |
Let's try this with something a bit stranger in shape. | 0:08:46 | 0:08:49 | |
OK, I'll remove the sphere. There we go. | 0:08:49 | 0:08:51 | |
Instead, put on this delightful potato asteroid here. | 0:08:51 | 0:08:55 | |
-Fine. -And you can see what the camera is seeing | 0:08:55 | 0:08:59 | |
as this point of light changes in brightness | 0:08:59 | 0:09:02 | |
as it turns, is when the short end is pointing towards the camera... | 0:09:02 | 0:09:06 | |
-Like it is now. -..you have minimum surface area being reflected, | 0:09:06 | 0:09:09 | |
the light, so it's dimmest. And when it turns round | 0:09:09 | 0:09:12 | |
and the whole side of this object is being illuminated, | 0:09:12 | 0:09:17 | |
it's the brightest to the camera, | 0:09:17 | 0:09:20 | |
and so you see this brightness peak. | 0:09:20 | 0:09:21 | |
And what do you find? What shape is 'Oumuamua? | 0:09:23 | 0:09:26 | |
It's actually got to be even more elongated than this little potato. | 0:09:26 | 0:09:31 | |
This is 3:1. 'Oumuamua has to be at least 5:1, | 0:09:31 | 0:09:35 | |
maybe even a bit longer. | 0:09:35 | 0:09:37 | |
But this is the thing, when I saw this result | 0:09:37 | 0:09:39 | |
from all this hard work of astronomers | 0:09:39 | 0:09:42 | |
scrambling to telescopes, it seems to me very unlikely | 0:09:42 | 0:09:45 | |
that the first interstellar visitor would be this unusual. | 0:09:45 | 0:09:50 | |
Is that something that disturbs you, | 0:09:50 | 0:09:52 | |
or does this make sense if you've been thinking about these things? | 0:09:52 | 0:09:55 | |
The shape is a bit unusual, | 0:09:55 | 0:09:57 | |
but the colour is so much like what we see in our own solar system. | 0:09:57 | 0:10:01 | |
There's a kinship there. It tells you that something that formed | 0:10:01 | 0:10:03 | |
around a different star and something that formed | 0:10:03 | 0:10:06 | |
around our own star have a lot of similarity in their surface. | 0:10:06 | 0:10:09 | |
It's a very deep thought, that. | 0:10:09 | 0:10:11 | |
It's sort of a poetic... It's scientific, but it's poetic as well, | 0:10:11 | 0:10:14 | |
that there is this relationship | 0:10:14 | 0:10:15 | |
to something that came from so far away. | 0:10:15 | 0:10:17 | |
Yeah, we're finally getting to touch something that's from | 0:10:17 | 0:10:21 | |
another solar system that's larger than a grain of dust. | 0:10:21 | 0:10:24 | |
Within days of being spotted, | 0:10:28 | 0:10:30 | |
detailed information about 'Oumuamua was coming in. | 0:10:30 | 0:10:34 | |
From Michele's light analysis, a shape was proposed. | 0:10:34 | 0:10:37 | |
It was thought to be an elongated cigar shape, | 0:10:37 | 0:10:41 | |
100 to 400 metres in length. | 0:10:41 | 0:10:43 | |
The ratio of length to width was thought to lie | 0:10:43 | 0:10:46 | |
between 10:1 and 5:1. | 0:10:46 | 0:10:48 | |
And although it was dark, it seemed to have a touch of pink or red. | 0:10:50 | 0:10:54 | |
By the end of November, | 0:10:58 | 0:10:59 | |
the strange shape and exotic nature of 'Oumuamua had led to some | 0:10:59 | 0:11:04 | |
extraordinary speculations. | 0:11:04 | 0:11:06 | |
Was 'Oumuamua an alien artefact? | 0:11:13 | 0:11:15 | |
It wasn't an entirely stupid question. | 0:11:25 | 0:11:28 | |
'Oumuamua was so strange | 0:11:28 | 0:11:30 | |
that at this stage almost anything seemed possible. | 0:11:30 | 0:11:33 | |
So I met astrophysicist and expert in the search for extraterrestrials | 0:11:33 | 0:11:38 | |
Duncan Forgan, to find out how scientists deal with the question of | 0:11:38 | 0:11:43 | |
whether an object is natural or alien. | 0:11:43 | 0:11:46 | |
So, Duncan, all this very interesting data was coming through, | 0:11:46 | 0:11:50 | |
what was the press's response to it? | 0:11:50 | 0:11:52 | |
It was a little bit frenzied, to be honest. | 0:11:52 | 0:11:54 | |
There were a lot of stories about this idea that maybe this | 0:11:54 | 0:11:57 | |
weird interstellar visitor was, in fact, | 0:11:57 | 0:11:59 | |
an alien spacecraft coming to visit the Earth. | 0:11:59 | 0:12:01 | |
But, unfortunately, a lot of that stuff was very overbaked. | 0:12:01 | 0:12:05 | |
So, how should scientists treat these stories? | 0:12:05 | 0:12:08 | |
I think it's important to make sure that when you're thinking about, | 0:12:08 | 0:12:10 | |
"What is this new, interesting, weird thing?" | 0:12:10 | 0:12:14 | |
you make your list of natural explanations, | 0:12:14 | 0:12:17 | |
-and then right at the very bottom you put the aliens explanation. -OK. | 0:12:17 | 0:12:20 | |
And you wait until you've exhausted all the natural explanations. | 0:12:20 | 0:12:23 | |
And then, when nothing else is left, Sherlock Holmes-style, | 0:12:23 | 0:12:27 | |
you come back to the aliens explanation. | 0:12:27 | 0:12:29 | |
So, one of the things that we did was to basically check | 0:12:29 | 0:12:31 | |
if 'Oumuamua was a transmitter. | 0:12:31 | 0:12:33 | |
So, they wanted to see if it was emitting radio waves | 0:12:33 | 0:12:36 | |
in the way that we'd expect a radio transmitter | 0:12:36 | 0:12:38 | |
built by an intelligent being to work, | 0:12:38 | 0:12:40 | |
so they pointed their radio telescopes at 'Oumuamua | 0:12:40 | 0:12:42 | |
and checked and found nothing. | 0:12:42 | 0:12:44 | |
So, what would you have done if it was found out that 'Oumuamua | 0:12:44 | 0:12:48 | |
was an alien artefact? | 0:12:48 | 0:12:50 | |
There are a list of protocols that people who are doing the search | 0:12:50 | 0:12:53 | |
for intelligent life are supposed to follow - | 0:12:53 | 0:12:56 | |
what they call a post-detection protocol, so what do you do next? | 0:12:56 | 0:12:59 | |
And so one of the things you need to do is A - check your answer, | 0:12:59 | 0:13:02 | |
-because if you get this wrong it could be very embarrassing. -Yes. | 0:13:02 | 0:13:05 | |
So, ask your colleagues to use a different instrument and try and do | 0:13:05 | 0:13:08 | |
the same experiment and if it comes out to be the same answer | 0:13:08 | 0:13:11 | |
then, OK, you've got something there. And then get more and more | 0:13:11 | 0:13:14 | |
people to check and make sure that your hypothesis has been validated. | 0:13:14 | 0:13:17 | |
And then you go to United Nations and tell the Secretary General, | 0:13:17 | 0:13:19 | |
"By the way, there's alien life and it's coming towards us." | 0:13:19 | 0:13:22 | |
-An interesting e-mail! -Yeah. | 0:13:22 | 0:13:24 | |
And then you're supposed to tell the public at large. | 0:13:24 | 0:13:26 | |
-Well, thank you so much. It's been fascinating. -Thank you. | 0:13:26 | 0:13:29 | |
In mid-December, the mysteries about 'Oumuamua were still mounting, | 0:13:42 | 0:13:47 | |
and scientists were beginning to wonder just where it had come from. | 0:13:47 | 0:13:51 | |
Michele Bannister picks up the story. | 0:13:53 | 0:13:55 | |
So, this brings me to the next question I wanted to ask, which is - | 0:13:57 | 0:14:01 | |
do we know where this asteroid, this body, came from? | 0:14:01 | 0:14:04 | |
It seems to me you've seen it coming in, so can we trace it back? | 0:14:04 | 0:14:09 | |
That will be a work in progress. | 0:14:09 | 0:14:11 | |
What we can do is say the arc that it took as it came into | 0:14:11 | 0:14:13 | |
the solar system, if we extend that back and back and back | 0:14:13 | 0:14:18 | |
for 100 million years... | 0:14:18 | 0:14:20 | |
You know, that's the better part of halfway round the galaxy | 0:14:20 | 0:14:24 | |
-as the sun's travelling. -OK, so we've travelled a long way, | 0:14:24 | 0:14:26 | |
-this thing's been moving, it's complicated. -Yeah. | 0:14:26 | 0:14:29 | |
You have to run the galaxy backwards in time and say, | 0:14:29 | 0:14:32 | |
"Where were all the stars millions and millions of years ago?" | 0:14:32 | 0:14:36 | |
And then say, "Was 'Oumuamua close to one of these stars?" | 0:14:36 | 0:14:39 | |
And if it was, that's its last port of call. | 0:14:39 | 0:14:42 | |
Now, that's not the same thing as saying that's where it's from. | 0:14:42 | 0:14:45 | |
-No. -Because the next star system that 'Oumuamua goes through, | 0:14:45 | 0:14:49 | |
it'll look like it came from us. | 0:14:49 | 0:14:50 | |
That's true. People will trace... | 0:14:50 | 0:14:52 | |
Aliens will trace it back and think it came from here. | 0:14:52 | 0:14:55 | |
But people have tried to match this trajectory, | 0:14:55 | 0:14:59 | |
to do this difficult calculation - how have they got on? | 0:14:59 | 0:15:01 | |
You can see it comes not close-close, | 0:15:01 | 0:15:04 | |
but perhaps a little bit close to some stars. | 0:15:04 | 0:15:08 | |
There's about 15 stars that are currently potential candidates that | 0:15:08 | 0:15:12 | |
it could've come near in that time. | 0:15:12 | 0:15:14 | |
But everything starts getting a little fuzzy, because we don't | 0:15:14 | 0:15:16 | |
actually know the positions of these stars particularly well. | 0:15:16 | 0:15:19 | |
About five of them are in a group of stars | 0:15:19 | 0:15:22 | |
loosely called the Local Association. | 0:15:22 | 0:15:26 | |
It's an amazing thought that it might be bouncing around | 0:15:26 | 0:15:28 | |
and, of course, it may encounter other stars in the future. | 0:15:28 | 0:15:31 | |
It has a long journey to go. | 0:15:31 | 0:15:32 | |
-Michele, thank you very much. -Thank you, Chris. | 0:15:32 | 0:15:35 | |
So tracking 'Oumuamua's orbit back through time and space has suggested | 0:15:37 | 0:15:41 | |
that it might come from a group of stars that astronomers call | 0:15:41 | 0:15:45 | |
the Local Association. | 0:15:45 | 0:15:47 | |
You might think that the Local Association would be a nice, neat | 0:15:48 | 0:15:51 | |
little cluster of stars in the night sky, but it isn't that simple. | 0:15:51 | 0:15:55 | |
Although they all formed around the same place | 0:15:57 | 0:15:59 | |
and at around the same time, | 0:15:59 | 0:16:01 | |
just 100 million years ago, they have since spread out. | 0:16:01 | 0:16:05 | |
Pete Lawrence explores this Local Association, | 0:16:11 | 0:16:14 | |
starting by looking towards the southern part of the sky. | 0:16:14 | 0:16:18 | |
The Local Association | 0:16:21 | 0:16:22 | |
is roughly in this direction here. | 0:16:22 | 0:16:25 | |
Most of the stars in it are too dim to be seen | 0:16:25 | 0:16:27 | |
with the naked eye, but it does include one of my favourite | 0:16:27 | 0:16:30 | |
open clusters, the Pleiades. | 0:16:30 | 0:16:32 | |
The Pleiades are some of our closest neighbours, | 0:16:34 | 0:16:37 | |
at a distance of 440 light years. | 0:16:37 | 0:16:40 | |
They're very distinctive, like a miniature Plough. | 0:16:40 | 0:16:43 | |
To locate them, find Orion in the southern sky | 0:16:44 | 0:16:48 | |
and follow the line of the belt up and to the right, | 0:16:48 | 0:16:51 | |
past Taurus and its distinctive V, | 0:16:51 | 0:16:54 | |
and then continue the line. | 0:16:54 | 0:16:56 | |
You should see a little huddle | 0:16:56 | 0:16:58 | |
of beautiful blue-white stars. | 0:16:58 | 0:17:00 | |
These really are one of the highlights of the winter night sky, | 0:17:02 | 0:17:05 | |
looking like rare jewels on black velvet. | 0:17:05 | 0:17:08 | |
But binoculars or a telescope will show even more. | 0:17:08 | 0:17:11 | |
And photography reveals an exquisite blue nebula, | 0:17:12 | 0:17:16 | |
visible because of light reflecting off of a cloud of dust | 0:17:16 | 0:17:20 | |
that the stars are moving through. | 0:17:20 | 0:17:22 | |
Associations like this are often hundreds of light years across. | 0:17:24 | 0:17:28 | |
For instance, there's another star in the association, which you can | 0:17:28 | 0:17:32 | |
find by heading southeast from the Pleiades | 0:17:32 | 0:17:34 | |
so that you're on the other side of Orion, the Hunter. | 0:17:34 | 0:17:37 | |
So a fair distance away. | 0:17:37 | 0:17:38 | |
Here you're in the constellation of Monoceros, the unicorn. | 0:17:38 | 0:17:42 | |
And there's a faint star there | 0:17:42 | 0:17:45 | |
which is a candidate for the origin of 'Oumuamua. | 0:17:45 | 0:17:49 | |
The star is called Ross 614. | 0:17:51 | 0:17:54 | |
You'll need a telescope to see it, | 0:17:54 | 0:17:57 | |
but to find it go back to Orion and head south and east. | 0:17:57 | 0:18:02 | |
Monoceros, or the unicorn, | 0:18:02 | 0:18:04 | |
is a group of fairly dim stars | 0:18:04 | 0:18:06 | |
between Canis Major and Canis Minor. | 0:18:06 | 0:18:09 | |
And Ross 614 is about | 0:18:09 | 0:18:11 | |
halfway along his front leg. | 0:18:11 | 0:18:14 | |
And it's in this group... | 0:18:16 | 0:18:18 | |
Oh, there it is! | 0:18:18 | 0:18:20 | |
It's just 13 light years away and is a component | 0:18:20 | 0:18:23 | |
in a red-dwarf binary system. | 0:18:23 | 0:18:25 | |
And it's fascinating and really exciting to think that may be | 0:18:25 | 0:18:29 | |
where 'Oumuamua came from. | 0:18:29 | 0:18:32 | |
By now, scientists had worked out quite a bit about 'Oumuamua. | 0:18:36 | 0:18:41 | |
They knew its rough size, speed and colour. | 0:18:41 | 0:18:44 | |
And if it did come from the Local Association, | 0:18:44 | 0:18:46 | |
they knew its age, too - | 0:18:46 | 0:18:49 | |
100 million years, | 0:18:49 | 0:18:51 | |
when these stars were formed. | 0:18:51 | 0:18:53 | |
But two big mysteries remained. | 0:18:54 | 0:18:56 | |
What was it made of and how was it formed? | 0:18:56 | 0:18:59 | |
Back in Belfast, Chris met up with Alan Fitzsimmons, | 0:19:03 | 0:19:06 | |
who started to investigate 'Oumuamua's composition. | 0:19:06 | 0:19:11 | |
His team believed it was icy, like most small distant objects. | 0:19:11 | 0:19:16 | |
But all the images they collected told a different story. | 0:19:16 | 0:19:20 | |
Because, if it was icy, why didn't it have a tail? | 0:19:20 | 0:19:24 | |
And so you got those images back and you were expecting to see what? | 0:19:27 | 0:19:30 | |
A comet with a nice tail, I guess. | 0:19:30 | 0:19:32 | |
That's right. This object passed pretty close to the sun, | 0:19:32 | 0:19:35 | |
and so the ices there should have been heated | 0:19:35 | 0:19:37 | |
and we should have seen that material expanding | 0:19:37 | 0:19:39 | |
away to form the atmosphere of the comet and the tail, | 0:19:39 | 0:19:42 | |
but there was nothing like that. | 0:19:42 | 0:19:43 | |
It looked like an asteroid, and so we were thinking, | 0:19:43 | 0:19:46 | |
"What is this thing?" | 0:19:46 | 0:19:48 | |
What did you do next? | 0:19:48 | 0:19:49 | |
The important thing then was to figure out how this object was | 0:19:49 | 0:19:52 | |
reflecting light because that could give us to a clue | 0:19:52 | 0:19:54 | |
to what it was made of. To do that, | 0:19:54 | 0:19:56 | |
we needed to get spectroscopy of the object. | 0:19:56 | 0:19:58 | |
So, what did the spectrum show? | 0:19:58 | 0:20:00 | |
Well, we saw the signature of carbon. | 0:20:00 | 0:20:02 | |
-Carbon? -Yeah. | 0:20:02 | 0:20:04 | |
Now, when we think of an icy comet, | 0:20:04 | 0:20:06 | |
we think of something that's mostly made of water ice, | 0:20:06 | 0:20:09 | |
although there may be some carbon monoxide and carbon dioxide. | 0:20:09 | 0:20:13 | |
This is an object that could have been out there between the stars for | 0:20:13 | 0:20:16 | |
millions or billions of years. | 0:20:16 | 0:20:18 | |
And so it's been sitting out there and during that time | 0:20:18 | 0:20:22 | |
it's been affected by the cosmic rays, | 0:20:22 | 0:20:25 | |
high-energy particles that fill our galaxy. | 0:20:25 | 0:20:28 | |
OK, so it's the cosmic rays that might have changed the surface. | 0:20:28 | 0:20:32 | |
-What would they have done to it? -They take those ices on the surface, | 0:20:32 | 0:20:35 | |
and in particular they take the carbon, | 0:20:35 | 0:20:37 | |
and the carbon rearranges itself | 0:20:37 | 0:20:40 | |
to form new molecules and new compounds. | 0:20:40 | 0:20:43 | |
And so what does that look like? How can we see what's happening? | 0:20:43 | 0:20:46 | |
I can explain using this demo, now... | 0:20:46 | 0:20:48 | |
-OK. -Basically a meringue - egg whites and sugar - OK? | 0:20:48 | 0:20:53 | |
And we can add some energy. Now, we're not going to use cosmic rays. | 0:20:53 | 0:20:56 | |
We're going to use a little blowtorch here. | 0:20:56 | 0:20:59 | |
-OK. Well, safety first. -Safety first indeed. | 0:20:59 | 0:21:02 | |
I do this every time I cook, you know. Very sensible. OK. | 0:21:02 | 0:21:05 | |
-There we go. -And now, | 0:21:07 | 0:21:09 | |
if we add energy to that we'll see a chemical transformation | 0:21:09 | 0:21:12 | |
to a different substance. | 0:21:12 | 0:21:14 | |
It's a very different material on the surface, | 0:21:14 | 0:21:17 | |
with the meringue intact inside. | 0:21:17 | 0:21:19 | |
Now... This is great cooking, | 0:21:19 | 0:21:22 | |
but what's this got to do with an interstellar asteroid | 0:21:22 | 0:21:25 | |
-or interstellar comet? -Well, instead of egg whites, of course, | 0:21:25 | 0:21:29 | |
and sugar, we have ice, we believe, that we start off with. | 0:21:29 | 0:21:32 | |
And instead of a blowtorch, | 0:21:32 | 0:21:34 | |
we have energy deposited on the surface by cosmic rays. | 0:21:34 | 0:21:37 | |
But only on the surface? | 0:21:37 | 0:21:39 | |
That's right. Now, over about 100 million years, | 0:21:39 | 0:21:42 | |
this chemical transformation can go down about half a metre or so. | 0:21:42 | 0:21:48 | |
Within that depth, we could still have ice there. | 0:21:48 | 0:21:52 | |
And the important thing is this not only changes the surface properties | 0:21:52 | 0:21:56 | |
and how it reflects light, this new crust of carbon-based material | 0:21:56 | 0:22:01 | |
also insulates the interior. | 0:22:01 | 0:22:04 | |
So it locks in, perhaps, the ice that's still there. | 0:22:04 | 0:22:07 | |
That's right, and when we do the calculations we find that | 0:22:07 | 0:22:11 | |
even though 'Oumuamua passed within the orbit of Mercury, | 0:22:11 | 0:22:14 | |
passed very close to the sun, | 0:22:14 | 0:22:17 | |
that heat from the sun could not have penetrated | 0:22:17 | 0:22:20 | |
within more than half a metre. | 0:22:20 | 0:22:22 | |
So the ice would have remained locked up | 0:22:22 | 0:22:24 | |
and that explains why we didn't see a comet, | 0:22:24 | 0:22:27 | |
we saw something that looked initially like an asteroid. | 0:22:27 | 0:22:31 | |
We'll look forward to hearing about whatever comes next. | 0:22:31 | 0:22:33 | |
-Alan, thank you very much. -Thank you. | 0:22:33 | 0:22:36 | |
By Christmas, scientists had a pretty good understanding | 0:22:47 | 0:22:50 | |
what 'Oumuamua was made of. But then came a new and exciting discovery - | 0:22:50 | 0:22:55 | |
revealed tonight for the very first time. | 0:22:55 | 0:22:58 | |
A powerful new theory started to emerge, | 0:23:03 | 0:23:07 | |
based on a detailed analysis of the light reflected off 'Oumuamua. | 0:23:07 | 0:23:13 | |
It suggested not just how it was formed, but also where it came from. | 0:23:13 | 0:23:19 | |
To find out more, | 0:23:20 | 0:23:22 | |
Chris met lead scientist on this new research Wes Fraser. | 0:23:22 | 0:23:26 | |
So, Wes, taking a close look at this thing, | 0:23:28 | 0:23:30 | |
it turns out to be even more complicated than we thought. | 0:23:30 | 0:23:32 | |
-What's going on? -Well, I was weirded out by the fact | 0:23:32 | 0:23:36 | |
that no-one publishing all these papers coming out of 'Oumuamua | 0:23:36 | 0:23:40 | |
could actually determine how quickly it was rotating. | 0:23:40 | 0:23:43 | |
And so one morning, one Friday morning, I just thought, | 0:23:43 | 0:23:46 | |
"I'm just going to pull all of this together and see what I can see. | 0:23:46 | 0:23:48 | |
"Now that we've got many days' worth of observations, | 0:23:48 | 0:23:51 | |
"surely we can pull all of this data together and just figure out how quickly this thing is spinning." | 0:23:51 | 0:23:55 | |
Wes's new investigation compares the light we might expect | 0:23:58 | 0:24:01 | |
from a spinning object, shown with the dotted line, | 0:24:01 | 0:24:04 | |
with the data that Wes actually gathered. | 0:24:04 | 0:24:07 | |
So, if you look at the plot here, | 0:24:08 | 0:24:10 | |
it works in some places, | 0:24:10 | 0:24:12 | |
but it completely fails in others - | 0:24:12 | 0:24:14 | |
where the curve is low, | 0:24:14 | 0:24:15 | |
the data are high. | 0:24:15 | 0:24:17 | |
-Yeah, yeah. Look, down here in day five - it's way off. -Yes, exactly. | 0:24:17 | 0:24:19 | |
Or even in the first couple of days, there's something odd going on. | 0:24:19 | 0:24:22 | |
It was exactly the comparison between night two and night five | 0:24:22 | 0:24:25 | |
that really... "OK, there's something weird going on here." | 0:24:25 | 0:24:28 | |
-OK. -And so we started to look at it a little bit, | 0:24:28 | 0:24:30 | |
and it was very clear that, in fact, this thing is tumbling. | 0:24:30 | 0:24:33 | |
So, what do you mean by "tumbling"? | 0:24:33 | 0:24:34 | |
Tumbling is an unusual state of rotation. | 0:24:34 | 0:24:37 | |
We can demonstrate this with a simple ping-pong paddle. | 0:24:37 | 0:24:40 | |
So, when we throw it like this... | 0:24:40 | 0:24:42 | |
..just spins on a single axis and it remains that way. | 0:24:47 | 0:24:50 | |
But when we throw it like this... | 0:24:50 | 0:24:52 | |
..it immediately enters tumbling. | 0:24:55 | 0:24:57 | |
It spins like this at the start, | 0:24:57 | 0:24:58 | |
but then quickly starts to wobble around chaotically. | 0:24:58 | 0:25:01 | |
And that's what we call tumbling. | 0:25:01 | 0:25:03 | |
This thing's been travelling in space for a long time. | 0:25:03 | 0:25:05 | |
How does it end up tumbling like this? | 0:25:05 | 0:25:07 | |
We think it was due to a collision. | 0:25:07 | 0:25:10 | |
And so at some early stage of its life, | 0:25:10 | 0:25:13 | |
it was just spinning normally like everything else | 0:25:13 | 0:25:16 | |
and then it suffered a collision. | 0:25:16 | 0:25:18 | |
That would impart enough energy on one particular spot | 0:25:20 | 0:25:23 | |
in such a way as to then be confused in how it spins. | 0:25:23 | 0:25:26 | |
And so where would that have happened? Out in empty space? | 0:25:26 | 0:25:29 | |
No, so we can pretty safely assume that the collision that caused this | 0:25:29 | 0:25:33 | |
thing to tumble was in its original stellar system, | 0:25:33 | 0:25:37 | |
before it got kicked out. | 0:25:37 | 0:25:40 | |
So this thing's carrying information | 0:25:40 | 0:25:42 | |
-about the early days of a different solar system? -In a way, yeah. | 0:25:42 | 0:25:46 | |
It's hard to know if it was during planet formation | 0:25:46 | 0:25:50 | |
or after the planet formation process. | 0:25:50 | 0:25:52 | |
Certainly more collisions happen while planets | 0:25:52 | 0:25:54 | |
are growing than afterwards, so that's a very good guess. | 0:25:54 | 0:25:57 | |
It now seems that Wes's result may tell us something profound. | 0:26:02 | 0:26:06 | |
'Oumuamua could be a relic from the formation of another solar system. | 0:26:06 | 0:26:11 | |
There is a chance that this tumbling occurred while planets were forming, | 0:26:13 | 0:26:16 | |
and so this is actually a moderately violent process. | 0:26:16 | 0:26:20 | |
So you can produce, you know, rocks and boulders and pebbles this way, | 0:26:20 | 0:26:23 | |
but eventually you do produce the planets in the process. | 0:26:23 | 0:26:26 | |
At that point, those collisions become violent and very destructive. | 0:26:26 | 0:26:31 | |
This may very well be where 'Oumuamua's shape has come from. | 0:26:31 | 0:26:34 | |
It's most likely where its tumbling has come from as well. | 0:26:34 | 0:26:37 | |
And we do know that objects are kicked out of our solar system, | 0:26:37 | 0:26:40 | |
as well - they have been and continue to do so. | 0:26:40 | 0:26:43 | |
So, while this is a bit of space that has, you know, | 0:26:43 | 0:26:47 | |
come its way to us, we are of course sending bits of ourselves naturally | 0:26:47 | 0:26:50 | |
to other places as well in a similar way. | 0:26:50 | 0:26:53 | |
You make it sound like the galaxy's full of these things. | 0:26:53 | 0:26:55 | |
Must be. Very, very much so. | 0:26:55 | 0:26:58 | |
-Yes. -So, how come this is the first one we've seen? | 0:26:58 | 0:27:01 | |
How many more are there that we're missing? | 0:27:01 | 0:27:03 | |
Our best guess at the moment - | 0:27:03 | 0:27:04 | |
and this is pretty uncertain cos we've only ever seen one - | 0:27:04 | 0:27:06 | |
but our best guess is, at least within our own solar system, | 0:27:06 | 0:27:10 | |
there are about 10,000 of these currently passing | 0:27:10 | 0:27:12 | |
-within the orbit of Neptune. -There are 10,000 of these... | 0:27:12 | 0:27:16 | |
-That's right. -..going through the solar system today? | 0:27:16 | 0:27:18 | |
-Today. -Not this year, not... -Yep. -So, why don't you see them? | 0:27:18 | 0:27:21 | |
For every one of those that we see, there's 10 or 100 that we miss. | 0:27:21 | 0:27:25 | |
And that just because of the fact that they're moving. | 0:27:25 | 0:27:27 | |
And so it was a fantastic job of the discoverers to find this thing. | 0:27:27 | 0:27:31 | |
-It's a fantastic discovery. -Well, lots more to look forward to... | 0:27:31 | 0:27:34 | |
-Yes, indeed. -..and it will be intriguing to find out | 0:27:34 | 0:27:36 | |
-whether this one is particularly unusual. -That's right. | 0:27:36 | 0:27:39 | |
-Wes, thank you very much. -Thank you. | 0:27:39 | 0:27:40 | |
The discovery of 'Oumuamua | 0:27:46 | 0:27:48 | |
has been one of the great scientific stories of the last 12 months. | 0:27:48 | 0:27:52 | |
This is our first deep-space object. | 0:27:52 | 0:27:56 | |
And this is now the most complete picture we have of 'Oumuamua. | 0:27:56 | 0:28:00 | |
It's now suggested that 'Oumuamua's origins | 0:28:07 | 0:28:10 | |
lay in the chaos of planetary formation... | 0:28:10 | 0:28:13 | |
..around a distant star... | 0:28:17 | 0:28:19 | |
..perhaps 100 million years ago. | 0:28:21 | 0:28:24 | |
That's it from Belfast for this month | 0:28:27 | 0:28:29 | |
and we're taking a break next month, but we'll be back in April. | 0:28:29 | 0:28:32 | |
In the meantime, don't forget to check out our website | 0:28:32 | 0:28:35 | |
for Pete's star guide and for our special weekly weather forecast. | 0:28:35 | 0:28:39 | |
And, of course, get outside and get looking up. Goodnight. | 0:28:39 | 0:28:44 |