On the early morning of February 13, 2013, people living in the Chelyabinsk region of
Russia awoke to one of the most powerful warnings in recent history.
Anyone looking up saw an incredibly bright meteor streak across the sky, brighter than
the Sun.
Observers said they could even feel the heat of the object as it passed overhead.
Moments later, the shockwave arrived, smashing out windows across a huge region, sending
almost 1,500 people to the hospital with various cuts and injuries.
It was absolutely amazing that nobody died.
But what was it?
According to astronomers, the Chelyabinsk meteor was probably a space rock measuring
about 20 meters (or 60 feet across).
It struck the Earth’s atmosphere going almost 20 kilometers per second, at such a low angle
that it just detonated, raining down debris, but sparing the region the true devastation
of this kind of an impact.
The Universe delivered a powerful warning that the Solar System is filled with rocks
and debris left over from its formation.
And those objects still continue to smash into the Earth.
In fact, one of the most terrifying things about the Chelyabinsk strike is this: the
meteor was completely unknown to astronomers before it crashed into the atmosphere.
The moment of impact was the moment of discovery.
Today I’m beginning a two part series all about the search for killer asteroids and
comets.
In part one, we’re going to talk about the risks we face.
What kinds of objects are out there, how dangerous are they, and what kinds of observatories
and programs are working to find the next impact event.
In part two, we’ll talk about defense.
If we do find a potentially dangerous asteroid or comet, what can we do to prevent an impact?
We’ll talk about the physics and engineering of moving asteroids, to make the Solar System
safer.
It’s not a question of “if” an asteroid will smash into the Earth, it’s a question
of “when”.
In fact, material from space is impacting our atmosphere all the time.
According to NASA, about 100 tonnes of rock and dust gets added to the Earth every day.
Once a year, a car-sized chunk of space rock impacts the Earth, exploding as a bright fireball.
A Chelyabinsk-level event is thought to happen once every 60 years or so.
In fact, there have been three other recorded events with that kind of energy release in
the last century, including the 1908 Tunguska event.
Every 2,000 years or so, an object the size of a football field hits Earth, causing localized
destruction.
And every few million years, an object comes along that releases so much energy, it would
threaten the existence of human civilization.
The problem of course, is that we don’t know when or where these events are going
to happen.
And it’s this problem that astronomers are trying to solve first.
Currently, we know of about 15,000 Near Earth Asteroids in the Solar System.
I’m not talking about the stuff in the asteroid belt, just the stuff that’s orbiting dangerously
close to our planet.
Over the last few decades, several asteroid survey programs have been in operation, mostly
ground-based automated telescopes that scan the sky, night after night, looking for anything
that shifts its position.
In fact, the names of many comets taken on the name of the survey that helped discover
them, like LINEAR and Pan-STARRS.
The Catalina Sky Survey is the most prolific asteroid/comet finder, turning up most of
the recently discovered asteroid and comets.
The repurposed WISE telescope, now NEOWISE has joined the search turning up asteroid
targets from space.
These surveys are important because the US Congress has mandated that NASA find 90% of
the asteroids larger than 140 meters by 2020.
Based on how things are going, it looks like these surveys will fail to meet this goal
because of the difficulty doing comprehensive surveys of the sky.
For every object that meets this 140-meter criteria, there are probably another 20 Chelyabinsk-class
objects out there.
Not to mention an additional 1,000 10-meter class objects.
All them, buzzing around up there.
Let’s talk about devastation for a second.
Just how bad would an asteroid strike be?
Here’s a great calculator that lets you hit the Earth with the impactor of your choosing
and see what the results would be.
Hit my hometown of Courtenay, British Columbia with a 140-meter asteroid, and I’d have
a very bad day.
In fact, here’s another simulation that puts it all on a handy map for you.
That brown crater is the center of my city.
I live right on the edge of it, about 1 km from the epicenter.
A crater 1.1 kilometers wide and more than 200 meters deep.
Most of the city is now a smouldering ruin.
Multi-story buildings are flattened, wooden houses (like my own) are torn apart, bridges
collapse, and cars and trucks are thrown around like ragdolls.
Also, my house’s windows might shatter.
Now that’s insult to injury.
Give this a try for your own hometown.
Try different options, find the apocalypse that’s right for you.
So yes, please find these asteroids.
Thanks.
In order to quantify the threat we face from asteroids, astronomers developed the Torino
Scale.
Every Near Earth Object gets a number from 0 to 10.
Zero is no risk, 10 is a certain impact from an asteroid with a global impact that could
wipe out human civilization.
The kind of event that happens every 100,000 years or so.
Fortunately, right now, there are no objects at all on the Torino Scale.
Occasionally an asteroid is discovered, and gets put on the scale for a few weeks or months
until follow up observations predict its orbit with more precision.
So far, the highest an object has ever been rated is level 4.
That was Asteroid Apophis, which astronomers thought might get kicked into a dangerous
orbit in 2029.
Follow on observations have dropped that risk back down to zero… phew.
In a moment, I’m going to talk about the various missions and observatories in the
works to pick up the pace in asteroid detection, but first I’d like to thank:
Howard Gitelson Michael Shi
Roman Geber Domanic Santerre
And the rest of our 760 patrons for their generous support.
If you love what we’re doing and want to get in on the action, head over to patreon.com/universetoday.
As I said before the break, the pace of asteroid discovery isn’t keeping up with the goal
of finding all the dangerous spacerocks by 2020.
In order to kick things up a notch, there are several new observatories and spacecraft
in the works, by both space agencies and private organizations.
Let’s look at some of these ideas.
In a previous video, I talked about the Large Synoptic Survey Telescope, currently in construction
in Chile.
If all goes well, it’ll be online in 2021, scanning the entire visible sky every few
nights.
Asteroids aren’t its focus, but it’ll be turning up all kinds of objects, explosions
and events.
It’ll help astronomers find anything that changes in the night sky, including the position
of deadly space rocks.
LSST will be capable of finding objects as dim as 24.5 magnitude in a 30-second image,
which means that it’ll be able to find asteroids which are 140-meters across all the way to
the Main Asteroid Belt.
In fact, the observatory could account for 60-90% of all the potentially hazardous objects
all on its own.
It would give us 1-3 months of warning for 45-meter objects on a collision course with
Earth, and find comets years in advance.
Enough time for Bruce Willis to gather together his crew of surly oil drillers.
Now that’s impressive, and you can see why I’m so excited for this observatory.
One recently proposed mission from a company called TransAstra is the Sutter Survey Telescope,
named after a discovery in California that led to the famous gold rush.
The Sutter Telescope would actually be 3 separate and relatively tiny satellites orbiting around
the Sun about 95% of the Earth’s orbit.
They would be positioned 120-degrees apart from Each other, giving them a complete view
of the Solar System at all times, with no blind spots.
TransAstra estimates that the Sutter Survey Telescope would be capable of finding the
same number of asteroids as LSST, but for a fraction of the price.
The entire constellation of tiny satellites could be built for $50 million.
And if the basic version is successful, TransAstra has proposed the Sutter Extreme mission.
This would boost the discovery rate by a factor of 24, and turn up about 7,500 asteroids a
year.
In 2013, the non-profit B612 Foundation, led by astronauts Ed Lu and Rusty Schweickart
began fundraising for the Sentinel Space Telescope.
If all goes well, the satellite will be launched in 2018 into a Venus-like orbit.
All on its own, Sentinel should be capable of identifying 90% of the Earth-crossing asteroids
larger than 140-meters.
So where do we stand?
Right now it looks like the US Congress mandate of finding the vast majority of dangerous
spacerocks is going to fail.
2020 will pass, and we still won’t know where are the deadly asteroids are.
That said, it does look like there are a group of ground and space-based observatories that’ll
get us closer to the answer - when will the next deadly asteroid hit us?
Where would you put asteroid detection in the Earth’s list of priorities.
Do you think we’re doing enough to protect the planet from an asteroid strike?
Or are the risks just too low to take it that seriously?
Next Episode: In this episode, we talked about the threats
we face from space rocks and what organizations and missions are working to find killer space
rocks.
In our next episode, we look at what can be done about them.
What are all the proposed strategies for stopping asteroids from smashing into the Earth.
That’s next time.
For this week’s playlist, we’re going to be hunting for asteroids, of course.
First, a compilation of videos about the Chelyabinsk impact that happened a couple of years ago.
Then a video about just how powerful the Tunguska Impact was, astronaut Ed Lu from the B612
Foundation talks about the threat of asteroids, Curious Droid talks about preventing asteroid
impacts, and finally, a lecture about the Yucatan impact 65 million years ago.