Astronomer Explains How NASA Detects Asteroids

[Reporter] In the new Adam McKay movie, Don't Look Up,

astronomers identify a comet heading towards Earth,

and politicians are slow to respond.

Then what happens like a tidal wave?

[Reporter] Wired talked to Dr. Amy Mainzer,

a real life astronomer who consulted on the film.

Let's take a look at a couple of scenes from the movie

Don't Look Up and explore the science

behind near Earth objects.

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It's gotta be an Oort cloud comet

just based on where you saw it.

Probably the last time it was this close to the sun

was long before human civilization.

Look at the arc on that thing.

A near Earth object is any asteroid or comet

that approaches the sun within about 30% or more

distance from the Earth to the sun.

So in other words, it just sorta has to get

close to the region of the Earth and the sun

in our part of the solar system.

NASA has a near earth object observations program.

And that's a network of telescopes all around the world,

and even in space that are systematically

searching for asteroids and comets

that can get close to the Earth's orbit.

When we first discover a new object,

we have a lot of work to do to figure out what it is.

The images that you see in the movie

where they're looking at these exposures of the comet

kind of marching across the sky,

those are actually images that I took from

our NEOWISE mission and made them a little bit larger

so you can see them.

And from that, we need to figure out where it's going,

and we need to make sure that it's a real object

and not just noise or confusion with a background source.

So when we first get these observations,

the first thing we do is we make a list

of their dates, times, and positions.

And then we send that to something

called the Minor Planet Center.

And this is a place that has a huge database

of all the known asteroids and comets that are out there.

And then they play this game of connect the dots basically,

to try to figure out if this is something

that we have already seen before.

If they can't make a match,

then it becomes a candidate for a new discovery.

And at that point, the news goes public.

To Comet Dibiasky, right?

Cheers.

There are a lot of rules that govern

the naming of bodies in space.

In the case of the comet that's discovered in the movie,

Kate Dibiasky, who's a PhD candidate,

it traditionally would probably take her name.

It would probably become Comet Dibiasky.

So that's pretty realistic.

Usually that whole process of collecting the data,

identifying the candidate new objects,

and getting them posted on the Minor Planet Center's

public website, that's pretty fast.

And that usually happens in less than a day.

Just tell us what it is.

He quickly figures out that this object

is very likely to have come from the Oort cloud.

You can kind of think of it as a cloud or a shell

of comets that surrounds the planets in our solar system.

We actually had to kind of make up a comet

specially for this movie that would have

the characteristics that we would want

for it to kind of drive the plot forward.

I designed the comet to be about nine kilometers across,

which is pretty typical,

and not an unusual size for a comet of this type.

But the thing is, such a large object would come in

from that distant outer part of the solar system,

the kind of frozen outer dark if you will,

it would come in towards the Earth with incredible speed.

That's kind of one of the reason

we pay attention to these long-period comets,

they can be pretty big,

and they can move with incredible velocities.

How would we find out

the comet's velocity and orbit, Professor Mindy?

That is a good question.

Well, this will be fun,

I haven't done orbital dynamics since grad school.

In the movie, we see Dr. Mindy using

what I would call kind of a classical method

of orbit determination called Gauss's Method.

And it's basically the idea that you sort of iteratively

solve for where the object is actually going

in three dimensions based on the two dimensional motion

that we see on the sky.

The math is there, and that is the real math we would use,

but we'd probably use a computer.

You have to remember space is incredibly, incredibly huge.

So the odds of any of these objects

ever getting close to the Earth,

let alone having an impact, are just incredibly rare.

So most of the time when we find something

it's a huge cause for celebration,

because it's gonna bring us new scientific knowledge,

and it has no chance of impacting the Earth whatsoever.

[Student] It's a party.

[Dr. Mindy] I'm just so, so thrilled for you, Kate.

The nature of what would happen if an object

were to impact the Earth really depends on a few things.

It depends on its velocity.

It depends on its size.

This is because the kinetic energy, that impact energy,

it scales as velocity squared.

And then also the size.

Kinetic energy goes as size cubed.

So small changes in size

make a very big change in the impact energy.

What happens depends very greatly on those parameters.

The Earth's atmosphere is really good at screening out

objects below about say 20 meters across.

So kind of the size of a house.

Anything smaller than that,

the Earth's atmosphere is effectively a brick wall.

And the object slams into it,

and is shattered into a zillion pieces.

By the time you get to something that's the size of say

100 meters across, or say a football field,

Now we're talking about something

that really could cause severe regional damage.

There will be mile-high tsunamis

fanning out all across the globe.

If this comet makes impact,

it will have the power of a billion Hiroshima bombs.

There will be magnitude 10 or 11 earthquakes.

You're breathing weird, it's making me uncomfortable.

I'm sorry, I'm just trying to articulate the science.

I know, but it's like so stressful.

I'm like trying to like listen.

If we have enough time,

there are a lot of different options available to us.

If we have, you know, years to decades away

from any potential impact, you've got things

that are as simple as just bumping into the object.

We call that a kinetic impact.

You just basically take a spacecraft,

you load it into a rocket,

and you send it into the path of the comet or the asteroid.

And nature takes its course, boom.

NASA is about to launch a mission called DART,

the double asteroid redirect test.

And in this mission, they're gonna take a spacecraft

and they're actually going to deliberately run it into

an asteroid, specifically the moon of an asteroid.

This is important because it allows us to verify

that indeed we can actually deliberately

alter the orbit of an object if we need to.

Another option if you have a lot of time,

is you can do something called a gravity tractor.

You basically build a really big spacecraft

that's big and heavy, and you park it next to the object,

and you just let the gentle force of gravity

change its orbit enough to make it miss.

If you have less time, or the object is really massive,

then you have to go to more drastic steps.

Something like using some sort of nuclear device

to try to push it out of the way.

But obviously that's the last resort.

At this very moment I say we sit tight and assess.

So NASA has actually put in place plans

to deal with any potential near Earth object impact.

There actually is a national

near Earth object preparedness plan now.

NASA has been doing these exercises

where they bring together the international community,

scientists, basically put them in a room and say,

okay, here's a scenario, go, figure out what would happen.

That said, the system is really set up to be transparent,

meaning that when the astronomers find an object,

we really wanna let the rest of the world know right away.

In 2008 an asteroid was discovered by

the Catalina Sky Survey, and they found

that it was within 24 hours of impacting the Earth.

Now fortunately, this was a really tiny asteroid,

kind of the size of about a VW bus.

But, within that 24 hour period, everybody got notified.

And astronomers contributed hundreds of observations

from all around the world.

The object's orbit was figured out to be so precisely known

that when it impacted in the desert over Sudan,

my colleagues were actually able to go out with students

from the University of Khartoum,

and they collected pieces of the meteorite that it became.

Asteroid impacts are not something you need to worry about

in your everyday life.

That said, it's not a problem that's completely negligible.

From my perspective, the right thing to do

is basically just go and do the kind of good

basic astronomy of looking for the objects,

figuring out where they're gonna go,

and making some measurements of things like their sizes

and other basic physical properties,

so that we have a pretty good idea of what's out there.

If we do that, then the chances of an impact ever happening

that we wouldn't know about well in advance

can be greatly reduced.

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