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We've been observing the planets with telescopes | 0:00:02 | 0:00:05 | |
for hundreds of years and sending probes out into space for over 50. | 0:00:05 | 0:00:09 | |
So you might have thought that our cosmic neighbourhood would be | 0:00:09 | 0:00:12 | |
pretty well explored. But the truth is, | 0:00:12 | 0:00:14 | |
we've only just scratched the surface. | 0:00:14 | 0:00:17 | |
The reality is that most of the Solar System still remains a mystery. | 0:00:17 | 0:00:21 | |
Once you head out beyond Neptune, you enter a realm that was, | 0:00:23 | 0:00:26 | |
until recently, almost completely unknown. | 0:00:26 | 0:00:30 | |
Yet we now know that it's full of extraordinary objects. | 0:00:31 | 0:00:35 | |
So tonight we're going to explore this unknown area. | 0:00:36 | 0:00:39 | |
We're going to venture out into this dark zone. | 0:00:39 | 0:00:43 | |
Since Pluto's relegation to dwarf planet status, | 0:01:11 | 0:01:14 | |
the planets of the Solar System now end at Neptune. | 0:01:14 | 0:01:17 | |
And if you think that all the exciting stuff | 0:01:17 | 0:01:19 | |
happens between there and the Sun, you're totally mistaken. | 0:01:19 | 0:01:22 | |
We now know that that dark realm beyond Neptune's orbit is filled | 0:01:22 | 0:01:27 | |
with a vast number of strange icy bodies. | 0:01:27 | 0:01:30 | |
And, as we've discovered them over the last couple of decades, | 0:01:30 | 0:01:33 | |
it's become clear that they play a critical role | 0:01:33 | 0:01:36 | |
in the evolution of the whole Solar System. | 0:01:36 | 0:01:40 | |
Tonight, from the Observatory at Herstmonceux, | 0:01:41 | 0:01:44 | |
we'll explore the incredible objects | 0:01:44 | 0:01:46 | |
that we're finding in the outer Solar System. | 0:01:46 | 0:01:49 | |
Some are on uniquely baffling orbits, | 0:01:49 | 0:01:51 | |
while others spin surprisingly rapidly. | 0:01:51 | 0:01:55 | |
And Marcus du Sautoy investigates the surprising mathematical laws | 0:01:55 | 0:01:59 | |
that govern these objects, and how they reveal that our Solar System is | 0:01:59 | 0:02:03 | |
potentially on the brink of catastrophic instability. | 0:02:03 | 0:02:08 | |
This group of strange new worlds needed a name, | 0:02:08 | 0:02:11 | |
and we call them the Trans-Neptunian Objects. | 0:02:11 | 0:02:13 | |
But to understand the role they play in the Solar System, | 0:02:13 | 0:02:17 | |
you really have to see them in context. | 0:02:17 | 0:02:19 | |
Let me paint you a picture of our Solar System. | 0:02:24 | 0:02:26 | |
At the centre, we have our local star, the Sun. | 0:02:26 | 0:02:30 | |
Then, the inner planets. | 0:02:30 | 0:02:32 | |
Mercury, Venus, | 0:02:32 | 0:02:34 | |
Earth, which of course we're on, | 0:02:34 | 0:02:36 | |
and then, a little beyond, Mars. | 0:02:36 | 0:02:39 | |
Then we move on to the outer planets. | 0:02:39 | 0:02:42 | |
Jupiter, Saturn. | 0:02:42 | 0:02:44 | |
Over here is Uranus. | 0:02:44 | 0:02:47 | |
And way over here is Neptune. | 0:02:47 | 0:02:50 | |
4.5 billion kilometres away from the sun. | 0:02:50 | 0:02:53 | |
Now, the images of the planets aren't drawn to scale, | 0:02:53 | 0:02:56 | |
but the distances from the Sun are about proportional. | 0:02:56 | 0:03:00 | |
Except this isn't the outer edge. | 0:03:00 | 0:03:03 | |
Not by a long way. | 0:03:03 | 0:03:05 | |
Because beyond is the realm of the Trans-Neptunian Objects. | 0:03:08 | 0:03:12 | |
Most are in a region called the Kuiper Belt. | 0:03:14 | 0:03:16 | |
Pluto, for instance, is here. | 0:03:18 | 0:03:20 | |
One called Haumea is here. | 0:03:21 | 0:03:24 | |
Another, called Eris, sits here. | 0:03:25 | 0:03:27 | |
And some are even further out, | 0:03:28 | 0:03:30 | |
or in strange orbits outside the plane of the Solar System. | 0:03:30 | 0:03:34 | |
The Kuiper Belt alone is huge, | 0:03:36 | 0:03:38 | |
some 16 billion kilometres wide. | 0:03:38 | 0:03:41 | |
It forms a flat disc, lying in the same plane as the planets. | 0:03:42 | 0:03:46 | |
And within it are hundreds of thousands of new objects, | 0:03:47 | 0:03:51 | |
maybe millions. | 0:03:51 | 0:03:53 | |
Trans-Neptunian Object hunter Michelle Bannister has been using | 0:03:55 | 0:03:59 | |
some of the most powerful telescopes in the world | 0:03:59 | 0:04:02 | |
to search through this dark zone. | 0:04:02 | 0:04:04 | |
She tells Chris about some of her most exciting discoveries. | 0:04:04 | 0:04:07 | |
Well, the outer Solar System is a fascinating and interesting place, | 0:04:09 | 0:04:12 | |
but what's been found recently? | 0:04:12 | 0:04:14 | |
Well, we've just wrapped up one of the largest surveys ever made | 0:04:14 | 0:04:18 | |
of the outer Solar System, and we've been able to double the number | 0:04:18 | 0:04:21 | |
of Trans-Neptunian objects orbiting outside Neptune, that are known, | 0:04:21 | 0:04:25 | |
that have really well understood orbits. | 0:04:25 | 0:04:27 | |
We've been able to discover more than 800 icy worlds, | 0:04:27 | 0:04:31 | |
little objects about 50 to maybe 300 or so kilometres in size, | 0:04:31 | 0:04:35 | |
most of them, that orbit beyond Neptune. | 0:04:35 | 0:04:38 | |
These are leftover pieces, planetesimals, | 0:04:38 | 0:04:40 | |
from the formation and evolution of the giant planets. | 0:04:40 | 0:04:43 | |
Just very excited, I've got | 0:04:43 | 0:04:44 | |
a picture of one of your discoveries here. | 0:04:44 | 0:04:47 | |
This goes by the delightful moniker of 2015RR245. | 0:04:47 | 0:04:51 | |
So RR245, it's a lot bigger than some of these others. | 0:04:51 | 0:04:56 | |
This is bright, this is really bright, | 0:04:56 | 0:04:58 | |
and when we found it, | 0:04:58 | 0:05:00 | |
it's moving across the sky over three hours | 0:05:00 | 0:05:02 | |
in these three images you see here, | 0:05:02 | 0:05:04 | |
really slowly, and because it's bright and slow, | 0:05:04 | 0:05:09 | |
that means it has to be very far away. | 0:05:09 | 0:05:11 | |
It turns out it's about 700km across. | 0:05:11 | 0:05:15 | |
It's one of the 20 largest dwarf objects in the outer Solar System. | 0:05:15 | 0:05:18 | |
So, what's a world like this actually like? What's it made of? | 0:05:18 | 0:05:21 | |
What would it be like to be there? | 0:05:21 | 0:05:23 | |
What you probably would see is a surface of complex ices. | 0:05:23 | 0:05:27 | |
Definitely water ice. | 0:05:27 | 0:05:28 | |
On Pluto, we know that water ice makes mountains. | 0:05:28 | 0:05:31 | |
So here maybe you'd see terraces | 0:05:31 | 0:05:34 | |
and small mountains of some water ice. | 0:05:34 | 0:05:36 | |
You'd also see reddish layers on the surface. | 0:05:37 | 0:05:40 | |
And that's because RR245 is probably large enough that it has | 0:05:40 | 0:05:45 | |
some of the complex molecules that form on icy surfaces over time, | 0:05:45 | 0:05:50 | |
from hydrocarbon molecules being bombarded | 0:05:50 | 0:05:53 | |
by the slow rain of cosmic rays. | 0:05:53 | 0:05:55 | |
So, I've got a picture of one of my favourites. | 0:05:55 | 0:05:58 | |
This is an artist's impression of Haumea, | 0:05:58 | 0:06:00 | |
which is one of the first to be discovered. | 0:06:00 | 0:06:03 | |
Yes, it was discovered back in 2003, | 0:06:03 | 0:06:05 | |
and we now know a lot more about this wonderful icy world, | 0:06:05 | 0:06:08 | |
this is one of the strangest objects in the outer Solar System. | 0:06:08 | 0:06:11 | |
It's shaped in this elongated way, like a rugby ball, | 0:06:11 | 0:06:14 | |
cos its spin axis is actually here. | 0:06:14 | 0:06:17 | |
So it's spinning like this, and it spins every 3.9 hours or so. | 0:06:17 | 0:06:21 | |
That's really fast. These are big things. | 0:06:21 | 0:06:23 | |
It's one of the fastest things in the Solar System, spinning, yeah. | 0:06:23 | 0:06:26 | |
This is spinning so fast that the solid rock itself | 0:06:26 | 0:06:29 | |
that makes up most of this object is actually flowing out, | 0:06:29 | 0:06:33 | |
and that gives it this elongated shape. | 0:06:33 | 0:06:35 | |
-How are they arranged? -Some of them are in a flat disc, | 0:06:35 | 0:06:39 | |
so they have round orbits that are flat. | 0:06:39 | 0:06:41 | |
These are probably the ones that have changed the least | 0:06:41 | 0:06:44 | |
since the formation of the Solar System in the Kuiper Belt. | 0:06:44 | 0:06:47 | |
Then you have ones where their orbits have been | 0:06:47 | 0:06:49 | |
dynamically changed, so they're actually excited, | 0:06:49 | 0:06:52 | |
they have tilted orbits out of the plane of the System. | 0:06:52 | 0:06:54 | |
Not a whole lot, but, you know, a few tens of degrees. | 0:06:54 | 0:06:58 | |
What are the big new discoveries still lurking out there? | 0:06:58 | 0:07:01 | |
There's some fun indications that we could have another dwarf planet | 0:07:01 | 0:07:05 | |
out beyond Neptune, that we haven't yet found. | 0:07:05 | 0:07:07 | |
This could be as big as a Mars-sized object, | 0:07:07 | 0:07:09 | |
and this ties into an object | 0:07:09 | 0:07:12 | |
that was found about a year and a half ago now, | 0:07:12 | 0:07:14 | |
by a different survey in Hawaii. | 0:07:14 | 0:07:16 | |
And this object, it actually orbits perpendicular | 0:07:16 | 0:07:18 | |
-to the plane of the Solar System. -Oh, is it called Niku? | 0:07:18 | 0:07:21 | |
-It's called Niku. -OK, I was going to talk to you. | 0:07:21 | 0:07:23 | |
-There's Niku in all its glory. -Yes! | 0:07:23 | 0:07:25 | |
I have to say, it doesn't look like much. | 0:07:25 | 0:07:27 | |
-It's got charisma. -All right, we'll go to the theory. | 0:07:27 | 0:07:29 | |
There you go, there's the theory. | 0:07:29 | 0:07:31 | |
We've watched this object move across the sky for several years, | 0:07:31 | 0:07:34 | |
and therefore able to do the computation of its orbit | 0:07:34 | 0:07:36 | |
and show this orbit is strange. | 0:07:36 | 0:07:38 | |
So, this is Jupiter, Saturn, Uranus, Neptune, all in a plane, | 0:07:38 | 0:07:41 | |
-and the Earth would be in this plane as well. -Right. | 0:07:41 | 0:07:43 | |
But this object orbits perpendicular to the plane of the Solar System, | 0:07:43 | 0:07:47 | |
and this is a mechanism that we don't have a clear idea yet | 0:07:47 | 0:07:51 | |
of how to form orbits like this. | 0:07:51 | 0:07:52 | |
You can make a comet that goes way out, | 0:07:52 | 0:07:55 | |
and then comes back in on such a perpendicular orbit, | 0:07:55 | 0:07:58 | |
but making something that's relatively small and close... | 0:07:58 | 0:08:01 | |
This dips in amongst the giant planets, and then zips out as far as | 0:08:01 | 0:08:04 | |
the Kuiper Belt. Except the Kuiper Belt's over here, it's, you know, | 0:08:04 | 0:08:08 | |
in a nice, relatively even disc. | 0:08:08 | 0:08:10 | |
Nothing does this in the Kuiper Belt. | 0:08:10 | 0:08:13 | |
Every time I talk to anyone who studies the outer Solar System, | 0:08:13 | 0:08:16 | |
I end up with more questions, so I hope you find more things, | 0:08:16 | 0:08:19 | |
I hope you come back and tell us about them. | 0:08:19 | 0:08:21 | |
-Thank you very much. -Thank you. | 0:08:21 | 0:08:22 | |
The more we peer in to this dark zone beyond Neptune, | 0:08:24 | 0:08:28 | |
the more mysteries we discover. | 0:08:28 | 0:08:30 | |
For most of astronomical history, | 0:08:33 | 0:08:35 | |
these Trans-Neptunian Objects have been hidden | 0:08:35 | 0:08:38 | |
from even the most powerful telescopes, | 0:08:38 | 0:08:40 | |
and that's why they've never got the attention they really deserve. | 0:08:40 | 0:08:43 | |
But these days, are they so impossible to spot? | 0:08:43 | 0:08:46 | |
To find out, we set Pete Lawrence a challenge - | 0:08:46 | 0:08:49 | |
to try and see a Trans-Neptunian Object using amateur equipment. | 0:08:49 | 0:08:54 | |
I've been given tough challenges on The Sky At Night before, | 0:08:59 | 0:09:02 | |
but this one has to be up with some of the hardest I've ever had. | 0:09:02 | 0:09:06 | |
These objects are, after all, tiny, dark and a long, long way away. | 0:09:06 | 0:09:11 | |
But I've decided to try and observe Haumea. | 0:09:11 | 0:09:14 | |
The reason I've chosen that particular one | 0:09:15 | 0:09:18 | |
is that it's really well placed at present. | 0:09:18 | 0:09:20 | |
It's actually located just between the midpoint, | 0:09:20 | 0:09:24 | |
or just south of the midpoint between the stars | 0:09:24 | 0:09:27 | |
Arcturus and Muphrid, | 0:09:27 | 0:09:29 | |
and both of those stars are in the constellation of Bootes. | 0:09:29 | 0:09:31 | |
I know the exact position of Haumea because I've looked it up | 0:09:32 | 0:09:36 | |
on the JPL Horizons Ephemeris Generator. | 0:09:36 | 0:09:39 | |
That's a free online resource. | 0:09:39 | 0:09:41 | |
And I can tell you, it's pretty faint, it's about magnitude 17.6, | 0:09:41 | 0:09:45 | |
which is about 36,000 times fainter | 0:09:45 | 0:09:47 | |
than the faintest star you can see with the naked eye. | 0:09:47 | 0:09:51 | |
To attempt this observation, I'm using my 130mm telescope, | 0:09:51 | 0:09:56 | |
with a DSLR camera and my laptop to process the images. | 0:09:56 | 0:10:01 | |
We are trying to capture this very close to the June Solstice, | 0:10:04 | 0:10:08 | |
so the sky is still really bright. | 0:10:08 | 0:10:11 | |
In fact, the threshold of brightness is too high, really, | 0:10:11 | 0:10:13 | |
to pick out anything really faint. | 0:10:13 | 0:10:16 | |
It's a little bit frustrating because I'm confident | 0:10:16 | 0:10:19 | |
that under darker skies, for instance, later in the year, | 0:10:19 | 0:10:22 | |
I'd be able to make this work. | 0:10:22 | 0:10:24 | |
I did have an inkling this was going to happen, so a month ago, | 0:10:24 | 0:10:28 | |
I did dial into a remote telescope set-up in New Mexico. | 0:10:28 | 0:10:33 | |
This is a commercially available telescope | 0:10:34 | 0:10:37 | |
that anyone can book time with on the internet. | 0:10:37 | 0:10:39 | |
The one I'm using is actually smaller than mine, | 0:10:39 | 0:10:43 | |
but the skies in New Mexico are fantastically dark. | 0:10:43 | 0:10:47 | |
And these are the results. | 0:10:47 | 0:10:49 | |
Well, looking at the New Mexico results, they're much clearer, | 0:10:50 | 0:10:54 | |
those dark, transparent skies have really worked for us. | 0:10:54 | 0:10:58 | |
But how am I going to find Haumea amongst all those stars? | 0:10:58 | 0:11:02 | |
Well, I'm going to use a classic technique | 0:11:02 | 0:11:04 | |
which is known as the blink method. | 0:11:04 | 0:11:06 | |
So, the blink method works like this. | 0:11:07 | 0:11:09 | |
The object I'm looking for will move over a period of days. | 0:11:09 | 0:11:13 | |
So if I take a picture on one day and then wait a few days, | 0:11:13 | 0:11:16 | |
take another picture, | 0:11:16 | 0:11:18 | |
and then I align the stars between those two pictures, | 0:11:18 | 0:11:21 | |
and then blink between them, | 0:11:21 | 0:11:23 | |
anything that moves should stand out like a sore thumb. | 0:11:23 | 0:11:27 | |
This is the same technique that was used in the 1930s | 0:11:28 | 0:11:31 | |
by Clyde Tombaugh to spot Pluto. | 0:11:31 | 0:11:34 | |
And these are the images he took over a week | 0:11:34 | 0:11:37 | |
that eventually revealed Pluto's existence. | 0:11:37 | 0:11:41 | |
Hopefully, that same technique should work for me. | 0:11:41 | 0:11:44 | |
And there it is! I can see it, | 0:11:46 | 0:11:48 | |
I can see the dot moving backwards and forwards. | 0:11:48 | 0:11:52 | |
Now, that represents the movement of Haumea over six days. | 0:11:52 | 0:11:56 | |
So the blink method has worked. | 0:11:56 | 0:11:58 | |
That's incredible, isn't it? I mean, that's an object which is | 0:11:58 | 0:12:01 | |
just a few hundred kilometres across, | 0:12:01 | 0:12:04 | |
and about 7.5 billion kilometres away. | 0:12:04 | 0:12:08 | |
That's amazing! | 0:12:08 | 0:12:09 | |
If you'd like to try and spot a Trans-Neptunian Object, | 0:12:10 | 0:12:14 | |
we've put some information about the positions of Haumea, | 0:12:14 | 0:12:17 | |
Makemake and Niku on our website. | 0:12:17 | 0:12:21 | |
And please do drop us a line to let us know how you do. | 0:12:21 | 0:12:25 | |
It's not just our instruments that have improved. | 0:12:28 | 0:12:31 | |
We now get much more information about objects in deep space | 0:12:31 | 0:12:35 | |
from missions like New Horizons. | 0:12:35 | 0:12:38 | |
Three, two, one... | 0:12:38 | 0:12:40 | |
We have ignition and lift-off of Nasa's New Horizons spacecraft... | 0:12:40 | 0:12:45 | |
Nasa's space explorer, New Horizons, reached Pluto in 2015, | 0:12:45 | 0:12:50 | |
and it's still exploring, venturing deeper into the Kuiper Belt. | 0:12:50 | 0:12:54 | |
It revealed new information about both Pluto and its moon, Charon. | 0:12:56 | 0:13:01 | |
It found unexpected warmth on Pluto | 0:13:01 | 0:13:04 | |
and a mysterious dark red area on Charon's North Pole. | 0:13:04 | 0:13:08 | |
Maggie spoke to New Horizons team member Carly Howett | 0:13:10 | 0:13:14 | |
from her base in Colorado, for the latest updates on these mysteries, | 0:13:14 | 0:13:18 | |
and to see where they're going next in this dark zone. | 0:13:18 | 0:13:22 | |
-Hi, Carly, good to see you again. -Yeah, you, too. Good to be here. | 0:13:23 | 0:13:26 | |
Now, last time we spoke, it was incredibly exciting, | 0:13:26 | 0:13:29 | |
because New Horizons had just flown past Pluto. | 0:13:29 | 0:13:32 | |
So what have been the most exciting findings so far? | 0:13:32 | 0:13:34 | |
So, I think there's two that really jumped out for me. | 0:13:34 | 0:13:38 | |
One is actually to do with Charon. | 0:13:38 | 0:13:40 | |
So, Charon, of course, is Pluto's biggest moon. | 0:13:40 | 0:13:42 | |
It's most of the same size as Pluto, | 0:13:42 | 0:13:45 | |
it's very large indeed, compared to its orbital parent body, | 0:13:45 | 0:13:48 | |
and so we didn't know it had a red pole. | 0:13:48 | 0:13:50 | |
And so there was a lot of work that's gone into | 0:13:50 | 0:13:53 | |
trying to understand what's going on. | 0:13:53 | 0:13:55 | |
And now, after two years of analysis, | 0:13:55 | 0:13:58 | |
Carly's team think they finally have an answer. | 0:13:58 | 0:14:02 | |
Charon is stealing Pluto's atmosphere, | 0:14:02 | 0:14:05 | |
which is freezing at its poles, then turning slowly red. | 0:14:05 | 0:14:10 | |
So, we think that Charon's poles are red because they're sort of nabbing | 0:14:10 | 0:14:14 | |
some of Pluto's atmosphere as it's being lost, | 0:14:14 | 0:14:17 | |
which I think is phenomenal. | 0:14:17 | 0:14:19 | |
But this process happens incredibly slowly. | 0:14:19 | 0:14:21 | |
So, Pluto has a very thin atmosphere, | 0:14:21 | 0:14:24 | |
and so you end up with about 1.5 millimetres | 0:14:24 | 0:14:28 | |
-per million Earth years. -Whoa! | 0:14:28 | 0:14:30 | |
So this process is not something that's happening overnight, | 0:14:30 | 0:14:34 | |
this is a very, very slow process, and it tells you, really, | 0:14:34 | 0:14:37 | |
that Charon's surface must be incredibly stable. | 0:14:37 | 0:14:39 | |
There's not an overturning, there's not a change in the surface, | 0:14:39 | 0:14:42 | |
because otherwise that reddening couldn't have happened. | 0:14:42 | 0:14:44 | |
But there's also talk that Pluto has a heat source. | 0:14:44 | 0:14:47 | |
Has that been confirmed? | 0:14:47 | 0:14:48 | |
The origins of that is that there's these shapes | 0:14:48 | 0:14:51 | |
that have very discrete boundaries, | 0:14:51 | 0:14:52 | |
and what we think is, they're like lava lamps, | 0:14:52 | 0:14:55 | |
so they're getting heated from the bottom, | 0:14:55 | 0:14:57 | |
slowly the material is rising up, and then falling back down again. | 0:14:57 | 0:15:00 | |
Now, there's two ideas, | 0:15:00 | 0:15:01 | |
one is that the energy source from that is from the interior | 0:15:01 | 0:15:04 | |
and it's leftover radioactive decay. | 0:15:04 | 0:15:06 | |
If it's radioactivity, wouldn't it have decayed long ago? | 0:15:06 | 0:15:09 | |
So, we think that, actually, there's enough remnant radiation, | 0:15:09 | 0:15:12 | |
because you just don't need enough, you just need a little bit. | 0:15:12 | 0:15:15 | |
We're still trying to figure out whether it's just purely sunlight, | 0:15:15 | 0:15:18 | |
whether sunlight's enough to drive it, or whether we do need | 0:15:18 | 0:15:21 | |
to sort of invoke extra radiation, um...sort of a superpower | 0:15:21 | 0:15:25 | |
for Pluto, for radiation to allow this convection to happen. | 0:15:25 | 0:15:28 | |
But we certainly don't need a lot of heat for it to happen, | 0:15:28 | 0:15:31 | |
a few degrees is all that's needed. | 0:15:31 | 0:15:33 | |
We've got all these fantastic results, | 0:15:33 | 0:15:35 | |
but what's next for New Horizons? | 0:15:35 | 0:15:36 | |
New Horizons is still busy, we found another target for it to visit. | 0:15:36 | 0:15:40 | |
It's got a very catchy name of 2014 MU69, | 0:15:40 | 0:15:44 | |
and this is a very small object | 0:15:44 | 0:15:48 | |
that's located in the Kuiper Belt. | 0:15:48 | 0:15:50 | |
We think it's never been heated up, so again, it's this sort of remnant | 0:15:50 | 0:15:53 | |
of the early Solar System. | 0:15:53 | 0:15:54 | |
Which is, again, important in order to understand | 0:15:54 | 0:15:57 | |
our own Solar System formation theory. | 0:15:57 | 0:16:00 | |
It hasn't been modified since | 0:16:00 | 0:16:01 | |
basically the dawn of our Solar System, so it's very exciting. | 0:16:01 | 0:16:05 | |
So, we're observing things en route, | 0:16:05 | 0:16:07 | |
but our next target we reach on the 1st of January in 2019. | 0:16:07 | 0:16:11 | |
So, there's going to be quite a lot of scientists that are going to be | 0:16:11 | 0:16:14 | |
-very sober on New Year's Eve 2018. -THEY LAUGH | 0:16:14 | 0:16:18 | |
So, Carly, what have we learned from its journey? | 0:16:18 | 0:16:21 | |
Oh, we've learned so many things. | 0:16:21 | 0:16:23 | |
I think we've learned that this region of space is not boring, | 0:16:23 | 0:16:27 | |
it's not dead. Activity is happening, | 0:16:27 | 0:16:29 | |
there's variation across different targets. | 0:16:29 | 0:16:32 | |
This is a region of space that really wasn't known | 0:16:32 | 0:16:34 | |
very much at all, and it's completely revolutionised | 0:16:34 | 0:16:37 | |
our understanding of these targets. | 0:16:37 | 0:16:39 | |
Well, Carly, thank you for talking to us again, | 0:16:39 | 0:16:41 | |
and we look forward to getting the latest results as they come through. | 0:16:41 | 0:16:44 | |
Thanks for your time. | 0:16:44 | 0:16:46 | |
Most of the Trans-Neptunian Objects | 0:16:48 | 0:16:50 | |
are leftovers from the origins of the Solar System. | 0:16:50 | 0:16:53 | |
This means they contain important clues as to how it evolved. | 0:16:54 | 0:16:59 | |
Scientists believe they've played a significant part | 0:17:01 | 0:17:04 | |
in the Solar System's most turbulent period, | 0:17:04 | 0:17:07 | |
a time when the orbits of the planets changed dramatically, | 0:17:07 | 0:17:11 | |
and they suggest there's a chance that this might happen again. | 0:17:11 | 0:17:15 | |
To understand how such relatively small objects | 0:17:16 | 0:17:20 | |
play such an important role, | 0:17:20 | 0:17:22 | |
you need a very particular tool... | 0:17:22 | 0:17:24 | |
mathematics. | 0:17:24 | 0:17:26 | |
Marcus du Sautoy explains. | 0:17:26 | 0:17:28 | |
For a mathematician like me, what's so fascinating | 0:17:35 | 0:17:38 | |
is that the planets, the Moon, the stars, all move | 0:17:38 | 0:17:40 | |
through the night sky following very strict mathematical rules. | 0:17:40 | 0:17:44 | |
And this idea is perfectly captured by this thing here. | 0:17:44 | 0:17:48 | |
It's called an orrery. | 0:17:48 | 0:17:50 | |
An orrery is a model of the planets revolving around the sun | 0:17:51 | 0:17:56 | |
that runs on one of the most beautiful mathematical systems, | 0:17:56 | 0:18:00 | |
clockwork. | 0:18:00 | 0:18:01 | |
Mathematics describes the clockwork nature of the way the planets move | 0:18:01 | 0:18:06 | |
around the Sun with such remarkable detail | 0:18:06 | 0:18:09 | |
that we're able to make predictions about where the planets will be | 0:18:09 | 0:18:12 | |
into the future with pinpoint accuracy. | 0:18:12 | 0:18:15 | |
This is because of Newton's theory of gravity - | 0:18:17 | 0:18:20 | |
a mathematical equation that shows how objects attract each other | 0:18:20 | 0:18:24 | |
through gravitational force. | 0:18:24 | 0:18:26 | |
Crucially, this means that as the planets and other objects move, | 0:18:28 | 0:18:32 | |
they can influence each other in ways that can be very profound. | 0:18:32 | 0:18:36 | |
Let's suppose this metal ball is a planet orbiting the Sun. | 0:18:36 | 0:18:40 | |
Let's set it off on its orbit. | 0:18:40 | 0:18:42 | |
I'm going to use this magnet | 0:18:44 | 0:18:45 | |
to represent the influence of a second planet. | 0:18:45 | 0:18:48 | |
So I should be able to give a kick | 0:18:48 | 0:18:50 | |
to the stable orbit of this first planet. | 0:18:50 | 0:18:53 | |
There, see, we're starting to influence the orbit | 0:19:00 | 0:19:03 | |
of the first planet in quite a dramatic way. | 0:19:03 | 0:19:05 | |
When one object or planet affects another via gravity, | 0:19:07 | 0:19:11 | |
we call it perturbation, | 0:19:11 | 0:19:13 | |
and it's an influence which has had a major effect on the Solar System. | 0:19:13 | 0:19:17 | |
And over the years, we've used the mathematics of perturbation | 0:19:17 | 0:19:21 | |
to solve some of the great mysteries of the Solar System. | 0:19:21 | 0:19:25 | |
For instance, in the 19th century, | 0:19:25 | 0:19:27 | |
the predictions of the position of Uranus were discovered to be wrong. | 0:19:27 | 0:19:32 | |
And mathematicians guessed this could actually be due | 0:19:33 | 0:19:37 | |
to another planet perturbing the orbit of Uranus. | 0:19:37 | 0:19:40 | |
And within 20 years, they found it. | 0:19:41 | 0:19:44 | |
It was named after the Roman god of the sea, | 0:19:44 | 0:19:47 | |
Neptune. | 0:19:47 | 0:19:48 | |
Mathematics doesn't just help us | 0:19:49 | 0:19:51 | |
to predict where objects will be in the future, | 0:19:51 | 0:19:54 | |
it also helps us to understand the very structure of the Solar System, | 0:19:54 | 0:19:58 | |
how it evolved and how it might eventually end. | 0:19:58 | 0:20:02 | |
And many believe that the Trans-Neptunian Objects | 0:20:03 | 0:20:07 | |
are evidence of this mathematics at work, | 0:20:07 | 0:20:09 | |
because of my second mathematical principle - | 0:20:09 | 0:20:12 | |
resonance. | 0:20:12 | 0:20:13 | |
This is a Barton pendulum, | 0:20:16 | 0:20:18 | |
and it shows how, under certain circumstances, | 0:20:18 | 0:20:21 | |
a regular pattern can powerfully influence another | 0:20:21 | 0:20:24 | |
through something called resonance. | 0:20:24 | 0:20:27 | |
I've got a series of pendulums hanging from a string here, | 0:20:27 | 0:20:30 | |
and I've got a driver pendulum. | 0:20:30 | 0:20:32 | |
And when I set this off, | 0:20:32 | 0:20:34 | |
the energy is going to get transferred to the other pendulums, | 0:20:34 | 0:20:37 | |
but they're not all going to react in the same way. | 0:20:37 | 0:20:39 | |
LANGUID PIANO MUSIC PLAYS | 0:20:39 | 0:20:42 | |
What we see is that these two pendulums are swinging much more | 0:20:44 | 0:20:47 | |
than the others, and this is because they're in resonance. | 0:20:47 | 0:20:51 | |
Resonance occurs when a pendulum absorbs the momentum easily | 0:20:52 | 0:20:57 | |
from the driver and relates to its length. | 0:20:57 | 0:21:00 | |
And some lengths work better than others. | 0:21:00 | 0:21:03 | |
So, here, the length of the string is the same as the driver, | 0:21:03 | 0:21:08 | |
and this one is in a 2:3 ratio. | 0:21:08 | 0:21:12 | |
Amazingly, the same thing can happen with the planets and the moons. | 0:21:12 | 0:21:16 | |
The gravitational attraction as they orbit means that, | 0:21:16 | 0:21:19 | |
under certain circumstances, they can begin to resonate. | 0:21:19 | 0:21:23 | |
So they kind of get locked in, creating a regular pattern. | 0:21:23 | 0:21:27 | |
For instance, Pluto resonates with Neptune, | 0:21:29 | 0:21:32 | |
orbiting twice for Neptune's three times. | 0:21:32 | 0:21:36 | |
And the Trans-Neptunian Objects resonate too. | 0:21:37 | 0:21:40 | |
Although this resonance seems to create order and balance, | 0:21:42 | 0:21:46 | |
it's not guaranteed, because, as with any finely balanced object, | 0:21:46 | 0:21:51 | |
it's easy for it to become destabilised. | 0:21:51 | 0:21:54 | |
Which brings us on to another mathematical subject | 0:21:57 | 0:22:00 | |
called chaos theory. | 0:22:00 | 0:22:01 | |
Roughly speaking, the idea reveals how a small change in the present | 0:22:05 | 0:22:10 | |
can have dramatic implications for the future. | 0:22:10 | 0:22:13 | |
Consider this pendulum here. | 0:22:13 | 0:22:15 | |
If I set it off, then it does exactly what you'd expect it to do. | 0:22:15 | 0:22:19 | |
If I now add a magnet to the base, then it perturbs the orbit. | 0:22:22 | 0:22:27 | |
It's still pretty predictable, but it's beginning to wobble. | 0:22:27 | 0:22:30 | |
But now, if I add two more magnets to the base, | 0:22:31 | 0:22:34 | |
the orbit becomes wildly unpredictable. | 0:22:34 | 0:22:38 | |
More accurately, what mathematicians mean by chaos | 0:22:38 | 0:22:41 | |
is that a small change in the starting position | 0:22:41 | 0:22:45 | |
can cause a completely different outcome | 0:22:45 | 0:22:47 | |
for the trajectory of the pendulum. | 0:22:47 | 0:22:49 | |
What we've come to realise in the last few years | 0:22:53 | 0:22:56 | |
is that our Solar System has much more in common | 0:22:56 | 0:22:59 | |
with this chaotic pendulum than we ever imagined. | 0:22:59 | 0:23:02 | |
Far from being stable and predictable, | 0:23:04 | 0:23:07 | |
it's actually unstable and chaotic. | 0:23:07 | 0:23:10 | |
And a small wobble of a tiny object could theoretically change | 0:23:10 | 0:23:15 | |
the whole structure of the Solar System completely. | 0:23:15 | 0:23:18 | |
But how about this for a thought? | 0:23:19 | 0:23:22 | |
Scientists now believe that chaotic disturbances have already played | 0:23:22 | 0:23:26 | |
a critical role in the history of our Solar System. | 0:23:26 | 0:23:28 | |
In particular, they suggest there may have been | 0:23:32 | 0:23:36 | |
a chaotic resonance catastrophe around 4.5 billion years ago. | 0:23:36 | 0:23:41 | |
As well as messing with the planets, | 0:23:42 | 0:23:45 | |
this might also finally explain | 0:23:45 | 0:23:47 | |
the weird orbits, spins and positions | 0:23:47 | 0:23:50 | |
of the Trans-Neptunian Objects. | 0:23:50 | 0:23:52 | |
To find out more, | 0:23:53 | 0:23:55 | |
Chris met up with Marek Kukula of Greenwich Observatory. | 0:23:55 | 0:23:59 | |
So what's the story? | 0:24:00 | 0:24:01 | |
What did happen 4.5, 5 billion years ago? | 0:24:01 | 0:24:04 | |
Well, the most popular model for what might have happened is | 0:24:04 | 0:24:07 | |
called the Nice model. | 0:24:07 | 0:24:09 | |
It's named after the Observatoire de la Cote d'Azur, | 0:24:09 | 0:24:11 | |
down in Nice in France, where the model was first come up with, | 0:24:11 | 0:24:16 | |
in 2005, I think. | 0:24:16 | 0:24:18 | |
And the idea here is that the giant planets - | 0:24:18 | 0:24:21 | |
Jupiter, Saturn, Uranus and Neptune - | 0:24:21 | 0:24:23 | |
were all in very neat orbits, but closer to the Sun than they are now, | 0:24:23 | 0:24:28 | |
and beyond them was this very thick, dense Kuiper Belt, | 0:24:28 | 0:24:31 | |
very different to the one that we have today. | 0:24:31 | 0:24:34 | |
So, although it looked, | 0:24:34 | 0:24:35 | |
perhaps from the outside, very neat and stable, | 0:24:35 | 0:24:37 | |
actually the seeds of its own destruction were already there. | 0:24:37 | 0:24:41 | |
And what happens is that the giant planets are able to pull in | 0:24:41 | 0:24:44 | |
the smaller objects from the Kuiper Belt and they flick them inwards. | 0:24:44 | 0:24:47 | |
But when the small objects start to get into the realm of Jupiter, | 0:24:47 | 0:24:51 | |
then something a little bit different happens. | 0:24:51 | 0:24:53 | |
Jupiter, obviously, the most massive planet, | 0:24:53 | 0:24:55 | |
its gravity is very powerful. | 0:24:55 | 0:24:57 | |
It's able, actually, to flick these objects | 0:24:57 | 0:24:59 | |
not further in, but further out, | 0:24:59 | 0:25:01 | |
it's flicking them perhaps even out of the Solar System entirely. | 0:25:01 | 0:25:04 | |
And of course, if it's flicking them out, | 0:25:04 | 0:25:06 | |
it has to move further in. | 0:25:06 | 0:25:08 | |
So, Saturn, the other giant planets are moving out, | 0:25:08 | 0:25:10 | |
Jupiter is moving in, and then you get to the situation where we have | 0:25:10 | 0:25:14 | |
a resonance, where Jupiter is going around the sun twice | 0:25:14 | 0:25:18 | |
for every one orbit that Saturn makes. | 0:25:18 | 0:25:21 | |
That resonance is a very powerful situation, | 0:25:21 | 0:25:24 | |
and that means that, as they do that, | 0:25:24 | 0:25:26 | |
they're giving very regular gravitational tugs | 0:25:26 | 0:25:28 | |
to Uranus, to Neptune and to the Kuiper Belt objects. | 0:25:28 | 0:25:31 | |
So what you get is, | 0:25:31 | 0:25:33 | |
as Jupiter and Saturn are doing this resonance thing, | 0:25:33 | 0:25:36 | |
they are pushing Uranus and Neptune further out | 0:25:36 | 0:25:40 | |
and they've pushed them out into this dense Kuiper Belt. | 0:25:40 | 0:25:43 | |
That's very chaotic. | 0:25:43 | 0:25:44 | |
These smaller objects are being thrown in all directions. | 0:25:44 | 0:25:47 | |
Many of them are being flung into the Solar System, | 0:25:47 | 0:25:49 | |
and this is where all hell breaks loose. | 0:25:49 | 0:25:53 | |
This computer simulation shows this moment of resonance, | 0:25:53 | 0:25:57 | |
followed by chaos. | 0:25:57 | 0:25:59 | |
The Kuiper Belt is in green and the outer planets are in the centre. | 0:25:59 | 0:26:02 | |
Suddenly, Jupiter and Saturn wreak havoc, | 0:26:03 | 0:26:06 | |
and the Kuiper Belt is scattered. | 0:26:06 | 0:26:09 | |
When that process is finished, | 0:26:09 | 0:26:10 | |
Uranus and Neptune perhaps swap places. | 0:26:10 | 0:26:13 | |
They and Saturn have moved further out from the Sun, | 0:26:13 | 0:26:16 | |
the Kuiper Belt has been scattered in all directions. | 0:26:16 | 0:26:19 | |
It's now much less dense and much more extensive, | 0:26:19 | 0:26:22 | |
and this is why we have the Solar System that we have today. | 0:26:22 | 0:26:25 | |
So, when we think about the chaos | 0:26:25 | 0:26:27 | |
that still exists in the Solar System, | 0:26:27 | 0:26:29 | |
the potential for chaos, the fact that things could change, | 0:26:29 | 0:26:32 | |
what's the worst that could happen? | 0:26:32 | 0:26:34 | |
Should we be worried? | 0:26:34 | 0:26:35 | |
Well, perhaps a little bit worried. | 0:26:35 | 0:26:37 | |
If you look at the Solar System as it is today, | 0:26:37 | 0:26:40 | |
it does look fairly stable, but in fact that's an illusion. | 0:26:40 | 0:26:43 | |
And if you look at all of the orbits of the planets, the other objects, | 0:26:43 | 0:26:46 | |
the Kuiper Belt, the asteroids, it is still rather a chaotic system. | 0:26:46 | 0:26:50 | |
It turns out that Mercury's orbit is not particularly stable | 0:26:50 | 0:26:54 | |
and there is a small, perhaps 1% chance, | 0:26:54 | 0:26:56 | |
that over the next few tens or hundreds of millions of years, | 0:26:56 | 0:27:00 | |
Jupiter's influence on Mercury could cause it | 0:27:00 | 0:27:02 | |
either to crash into the Sun, | 0:27:02 | 0:27:04 | |
to fly out of the Solar System entirely, | 0:27:04 | 0:27:06 | |
or perhaps even to crash into either Venus or the Earth. | 0:27:06 | 0:27:10 | |
So, no sign that that's happening, but we can't be certain. | 0:27:10 | 0:27:13 | |
We can't rule it out. | 0:27:13 | 0:27:14 | |
It's a small possibility, but it is a real, finite possibility, | 0:27:14 | 0:27:19 | |
so we're still living in chaotic times, the chaos isn't over yet. | 0:27:19 | 0:27:24 | |
It seems now that the exploration | 0:27:26 | 0:27:28 | |
of the weird world of Trans-Neptunian Objects | 0:27:28 | 0:27:31 | |
is presenting us with a new chaotic picture of our Solar System. | 0:27:31 | 0:27:35 | |
This is light years away from the stable, predictable one | 0:27:36 | 0:27:40 | |
we thought we knew before. | 0:27:40 | 0:27:42 | |
And there's still so much more to explore. | 0:27:43 | 0:27:47 | |
I'm so impressed by what's being found in the outer Solar System - | 0:27:52 | 0:27:55 | |
the diversity of worlds, but also their sheer number. | 0:27:55 | 0:27:58 | |
800 new places in that one survey alone, | 0:27:58 | 0:28:01 | |
and who knows what else is out there? | 0:28:01 | 0:28:03 | |
But that's the exciting thing, I think. | 0:28:03 | 0:28:05 | |
We're discovering new things all the time, | 0:28:05 | 0:28:07 | |
and by looking at these objects so far away from the Sun, | 0:28:07 | 0:28:10 | |
we're discovering about the evolution | 0:28:10 | 0:28:12 | |
of the whole of the Solar System. | 0:28:12 | 0:28:14 | |
That's all we have time for in this programme, | 0:28:14 | 0:28:16 | |
but do join us next month | 0:28:16 | 0:28:18 | |
when we'll be looking at the profound effect | 0:28:18 | 0:28:20 | |
that space has here on Earth, | 0:28:20 | 0:28:22 | |
from a deluge of space dust to the beauty of a meteor storm, | 0:28:22 | 0:28:26 | |
to the potential for life itself. | 0:28:26 | 0:28:28 | |
And in the meantime, do check out our website at bbc.co.uk/skyatnight, | 0:28:28 | 0:28:34 | |
where you'll find exclusive content, including a star guide. | 0:28:34 | 0:28:37 | |
In the meantime, of course, get outside and... | 0:28:37 | 0:28:40 | |
get looking up. | 0:28:40 | 0:28:42 | |
Goodnight. | 0:28:42 | 0:28:43 |