Oumuamua

Hello and welcome to Mysteries of Science. My name is Dan and I'm the editor of Science

and Nature, the monthly magazine from the team behind The Week Junior.

And I'm Michael, the features editor. On this podcast, we investigate weird events,

strange creatures and mysterious places.

That's right. And today we will going to be investigating the mystery of a muamua.

A muamua? What's this, Dan? It's a mystery about a cow?

Yeah, some kind of Hawaiian cow. Well, it's, well, it's, it's, it's, well, to be honest, I can't quite tell you what it is.

A muamua was a mysterious object that appeared in our solar system back in 2017.

and nobody was quite sure what it was.

Was it a comet?

Was it an asteroid?

Or a comet?

Would it have been some aliens paying us a visit?

Well, I think we need to speak to some expert guests to find out what it is, where it came

from, and I think the biggest question of all, why it's called Oumuamua.

Indeed, these are the mysteries we will solve today.

This is Mysteries of Science.

Okay, Dan, Oumuamua, I'm going to really enjoy saying that name again and again over the

course of this podcast.

I think we should say as much as we possibly can.

Do you know what else is fun to say?

What?

Another word which is in our newest issue of Science and Nature.

It's moon moon.

Moon moon.

That is fun to say.

Oumuamua and moon moon.

All the fun words today.

Well, yeah, if you get the latest issue of the Week Junior Science and Nature magazine,

which is out now, then you will see a section on moon moons in our article on Oumuamua.

But don't worry if you haven't got your copy yet. Stay tuned, we'll tell you what a moon moon is at the end of the show.

Right, I can't wait for that. So back to Oumuamua. Who can tell us what it is?

Hi everyone, I'm Dr Maggie Lu. I'm a Research Fellow in Machine Learning and Cosmology at the University of Nottingham.

Hello, I'm Chris Lintott. I'm an astronomer here at the University of Oxford.

I also work for the BBC on the Sky at Night programme,

and I'm an astronomer because I grew up looking at the stars and wondering what they were.

Welcome to the show, Chris, and welcome back to the show.

Maggie, long-time listeners of Mysteries of Science,

may have heard Maggie on some of our previous episodes,

so we're in very safe hands here with these two experts.

So, tell us, what is Oumuamua?

Well, Oumuamua is one of the most unusual and interesting objects we've ever seen.

When it was discovered, it was seen only as a point of light moving through the sky,

not moving rapidly, not like a shooting star, but moving from night to night.

And usually this means you've found an asteroid or something like that,

something within our solar system.

But as astronomers watched over a couple of nights,

it became clear that Oumuamua had come from beyond our solar system.

So it's what we call an interstellar asteroid.

It's the first time we've seen something like this

that comes from a different star system and paid us a visit.

Actually, by the time we found it,

it was already on its way out of the solar system.

So we only got a couple of months of being able to watch it.

So all the information we have about it comes from just those few months back in 2017.

Wow.

Okay, so astronomers discovered an object that had come from beyond our solar system.

I love this idea.

And we only had a couple of months to try and figure out what it was?

I love it.

It's a race against time.

Now, I guess that the first thing you do when you're trying to figure out what something is, is take a good look at it.

wouldn't you say, okay, well, what does it look like?

But Chris said Oumuamua just appeared as a tiny point of light moving through the sky.

So how can we figure out what it looks like?

When you observe things in astronomical data,

they don't actually appear like much because they're so far away.

It's usually just a tiny dot.

And what you'll see is just how bright it is,

how bright it is based on how much it's reflecting from the sun.

because this object, it doesn't emit any light itself.

It's not a star. It's not like our sun.

So what you're relying on is reflection from the sun on the object to be able to see it.

OK, so this object is dark.

It doesn't produce any light of its own.

And the only way we can spot it is in the night sky is because it's reflecting light from the sun.

That's right.

and as Maggie is about to explain, how it reflects this light can...

Tell us what it looks like.

If it was just, for example, a fixed circular object

reflecting the same amount of light all the time,

then you would just get this straight line, right?

The light wouldn't change.

But with a muamua, you get this light profile

that gets brighter and then dimmer.

And that's odd.

It tells you that there's something unusual about the object.

And our best idea is that a muamua must have an unusual shape.

So a lot of the first ideas were that it might be pencil-shaped,

so long and thin and tumbling end over end as it travels through space.

And if you think about that for a minute,

if you're looking along the pencil, so you see the long side,

then you see quite a lot of light.

If you were looking straight down the pencil, you see much less light.

So that would explain the change in brightness.

Some people still think it's shaped like that.

Other people think that it's much better to think of it

as a sort of pancake shape or a disc flying through the universe.

But again, this idea that if you look down on the pancake, it's bright.

If you look on the side, it's there.

Okay, so I'm going to do a little experiment here.

Have you got a pen or a pencil to hand?

Pick it up now, look at it,

and in the scientific terms, rotate it,

i.e. spin it around and around in your hands,

imagining that light from the sun is bouncing off it,

and that will kind of give you some idea

of what this strange object looked like

and how it moved through space.

I'm doing it myself you might be able to see me Michael um and and I can see that yes when when

it's uh when you're looking down the pen it's it's very small and round and then as the pen comes up

it gets longer and longer and longer so it's kind of tumbling exactly and the other uh object they

said it might look like is a pancake so you can maybe we'll try the same experiment if you've got

a pancake to hand but to be honest if you've got a pancake in front of you I'd forget all about the

science and just enjoy your breakfast. I'm very jealous

of you right now if you're listening to us while eating pancakes.

Yeah, exactly. Well, if you've got a pancake, maybe just try flipping it in the pan

whilst seeing how it reflects the light just before you gobble it all up.

Anyway, back to Amumu before I get too hungry and have to stop for pancakes.

So it came from outside our solar system. That means it's a visitor from outer space

and it had an unusual pencil shape.

You might say spaceship-style shape or a pancake shape.

You might say flying saucer shape.

I don't know. I don't want to be too leading.

What else do we know about it?

One particular thing is that it was moving incredibly quickly,

much faster than anything pretty much in our solar system,

and they couldn't figure out why it was so fast.

This wasn't expected. It should slow down because it should be pulled.

by the sun's gravity.

So it should have to fight hard to escape the solar system.

But it seemed to be speeding up.

So there's some sort of activity or something there

that's causing it to speed up.

And again, we're still arguing about what that might be.

I mean, I have a pretty good idea of what that might be.

I think I know where you're headed, Michael.

Could you let us know?

It's come from outside our solar system.

It has a very unusual, like you said,

perhaps flying saucer-like shape.

It's moving incredibly fast.

it must be an alien spaceship right makes you think huh makes you think i mean i think the

idea that it was an alien spaceship occurred to lots of us when we were first talking about this

uh object you've got something that's come from another star system we know about this we've seen

it in movies and read it in science fiction uh and in fact there's a famous science fiction book

called rendezvous with rama in which a long thin cylinder visits the solar system and astronauts

go and see it

and it's obviously

a spaceship

although its purpose

is never

revealed. So I think it's a sensible thing to do to say, could this be an alien spaceship?

And so, could it be?

I don't think many people believe it's due to an alien

hitting the kind of acceleration on their spacecraft. And actually, so there were radio

telescopes that focused their antenna on the Onamua Mua to see if they could hear any radio

signals if it was an alien spacecraft and they observed it for many days and there was nothing

so it's unlikely to be an alien spacecraft one day dan one day the answer will be aliens

yes statistically speaking one day it probably will be uh better luck next time uh another

mystery that turned out not to be aliens but in in the in the case of many of these mysteries

You know, we quite often ask, is it aliens?

But the mystery still remains when we find out it's not aliens.

If it's not an alien spaceship, what is it?

I think you can explain what it's doing without it being an alien spaceship.

So we would expect things that live on the outer edges of our solar system tend to be comets.

So when they come into the inner solar system, they're made of ice, they heat up, they grow a tail.

You've probably seen pictures of comets that have these lovely tails.

Well, that's because the ice in the comet, when heated up, turns into gas.

You get this nice tail.

But so we might expect Urumuru, if it was a comet-like thing from another solar system,

to also heat up and have gas shooting from it.

So that would cause like a rocket-like propulsion,

and that would speed it out of the solar system.

Okay, so is that case closed then? Is Urumuru a comet?

The only problem with that idea is that we didn't see any evidence of it being like a comet.

We didn't see a tail. We didn't see what's called a coma, an atmosphere.

So we didn't see signs of this.

Ah, this is a very naughty little mystery.

So, I mean, I'm interested to see that.

There was that unanswered question about how it sped away.

And I like the idea that, you know, if it had grown a tail and it was shooting gas out the back,

that might actually act like a rocket booster and speed it off.

But it's not a spaceship.

I'm happy to accept that.

It's not a comet either,

because there were things which comets have that this didn't have.

So, well, what is a mua mua?

Other people think things like maybe it's a very exotic object,

something we don't see in our solar system.

So there's a group of people who think it's an iceberg,

but an iceberg made of hydrogen.

And we have hydrogen in the universe.

It's the most abundant.

element. There's more of it than anything else. And maybe in the conditions in which stars and

planets form, maybe in these cold regions of space, you might get hydrogen icebergs,

and maybe this is one that escaped. We don't know. What we need to do is find more of them,

because we've only seen Humuma was the first one. And then there was one about a year later that

was called Borisov, named after its discoverer in Kazakhstan. And Borisov was a much more normal

comet. So it came from beyond the solar system, but it basically behaved like a comet. It grew

a tail. It did all the things we expect

comets to do. So, so far we've got two.

One was very unusual. One was

what we expected and

now we're waiting for the third one to turn up.

Wait, so Oumuamua

isn't the only time

this has happened then. We had another one,

Borisov. So, how many other,

how many more of these objects are there

in the solar system? The really mind-blowing

thing about Oumuamua is that it

told us we should be more

awake at looking for these things.

So, just the fact that we saw this

one thing that was faint and dull.

and moving fast, tells us, we think, that there should be, I'll try and get this right,

a billion, billion, billion of these things in the Milky Way galaxy.

So each solar system produces billions of these objects and donates them to the galaxy.

So if you think space is empty, it's actually full of these little rocks whizzing or ice cubes whizzing around.

We think that at any given time, there's one passing through the solar system.

So there's one closer to the sun than Jupiter right now, probably.

but we're very bad at finding them.

So we're having to build new telescopes

and build new techniques to go and look for these things.

It's amazing to me that these may be the most common things in the galaxy.

We can rule atoms out,

but the most common large things in the galaxy are these interstellar objects.

And we hadn't thought to go and look for them until, what, seven years ago.

I mean, that's incredible.

Billions and billions and billions of these objects flying through space.

and I'm no

mathematician Dan

but surely

by the law of

Averages. That means at least one of them has to be an alien spaceship, right?

Yeah, yeah. Clutching at straws a little bit here, maybe.

I think you need to let this one go, Michael.

Never, never.

OK, so we don't know for sure what Oumuamua is.

There's some good theories, that hydrogen iceberg theory.

But to know for sure, we might need to wait and see if we can find other similar objects and study them.

there is one question we can answer definitely though it is the biggest question of all the one

we started with why is this thing called a mua mua so mua mua is a hawaiian name because the

object was discovered by a telescope on a hawaiian island and in hawaiian if you repeat something it

emphasises it. So mua means

far away. So muamua

is really far away.

And u is a scout. Somebody goes out

and looks. So u muamua is the

scout.

from really, really far away.

It's sort of this sense that it's a visitor

coming from elsewhere.

It's a lovely name.

It's good fun to say.

I recommend everyone listening to this

say Umuamua out loud several times.

It's good for you.

It really is a lot of fun to say.

Umuamua, Umuamua, Umuamua.

I'll say it three times.

We have really...

Maybe that'll make it appear.

Yeah, watch out.

Well, apparently if there's billions and billions

of them out there, similar objects,

they should be whizzing past at any time now

if we go and look up using the right telescope.

Yeah, keep an eye out.

It's such fun to say.

In fact, maybe some of our listeners will want to record themselves saying it

and send it to us.

Could you have a go at home in your best space expert voice?

Say, amuamua.

We can see who says amuamua the best.

So to record a voice note, just head to funkidslive.com

forward slash mysteries

hit the big red button.

Yes, it's as easy as that,

and you could appear on a future episode of Mysteries of Science.

Now, Dan, don't think I've forgotten as well about your tease at the start of the show,

so we know what Oumuamua means now.

What's a moon moon?

Aha! Well, a moon moon,

as readers of the Week Junior Science and Nature magazine will already know,

is a moon that orbits another moon.

Actually, do you know what's really fascinating?

no moon moons have been found yet. But scientists are sure that they could exist

under certain conditions. Interesting. Maybe one day we'll have to do a whole episode on moon moons.

Now, it wouldn't be an episode of Mysteries of Science without the Mysteriometer. This is our

scientific scale from zero to 100, with zero being we know nothing at all, and 100 being case closed,

We figured everything out.

So I wonder where our experts...

Chris and Maggie think we are on this scale when it comes to Oumuamua.

So I think for Oumuamua on the mysteryometer, I think we're about 60 or 70.

So we have these big questions like exactly what it was made of,

and we don't even know where it came from.

The frustrating thing is that unlike almost all other science mysteries,

we can't get any more information.

It's gone. It's disappeared.

It's way beyond the reach of our telescope.

So we'll never see it again.

So I would put it close to maybe 20.

We know it's rough shape or length.

We know it doesn't emit any radio signals from what we've heard of.

But yeah, there's still a lot of mystery behind what's exactly going on there.

Yes, I can see.

I love it when scientists have a little bit of a disagreement there on the actual number.

It means that there's lots more to find out about.

but I think both agree that there's