What If You Could See Asteroids In the Night Sky?

An anonymous reader writes: As part of Asteroid Day a 360-degree video rendering the night sky with the population of near-earth asteroids included has been created by 'Astronogamer' Scott Manley. The video shows how the Earth flies through a cloud of asteroids on its journey around the sun, and yet we've only discovered about 1% of the near earth asteroid population.

Comments

How do we know we've only discovered 1% of NEAs?

[sjbe]

The video shows how the Earth flies through a cloud of asteroids on its journey around the sun, and yet we've only discovered about 1% of the near earth asteroid population.

Ok, how do we know what we haven't discovered yet? I know statistical techniques for estimating population sizes of wildlife. (Catch some number, tag and release, catch a bunch more and see how many tagged ones you catch which gives you a population estimate) I'm not sure those techniques are applicable here. Anybody have any idea how this estimate was arrived at or is it taken straight out of someone's derriere? Measurements of orbit perturbations? Something else?

Re:We'd probably be more on protecting ourselves.

[ArcadeMan]

Yeah, right. I'm pretty sure that's not going to happen any time so{#`%${%&`+'${`%&NO CARRIER

And if you're on the asteroid itself...

[ArcadeMan]

Carter, I can see my house!

Re:How do we know we've only discovered 1% of NEAs

[MozeeToby]

It's not that hard, you know how much of the sky you've looked at. You know the sizes, positions, and velocities of all the asteroids you've cataloged. From there it's a non-trivial but certainly doable calculation to come up with an estimate of the total number.

Re:How do we know we've only discovered 1% of NEAs

[aaron4801]

If it's just a count of objects, "1%" doesn't mean much anyway. We should be much more interested in mapping Mass. A 1kg asteroid is mostly harmless (to Earth, though it could be catastrophic for man-made satellites). This may be a faulty assumption, but I would think the larger, more dangerous objects would be detected first. If so, 1% of the total number may represent something like 50% of the total mass of all NEAs. If that's true, it's far less ominous than saying "99% of potential Earth-impacting asteroids are currently hidden!!!1!"

Re:How do we know we've only discovered 1% of NEAs

[rubycodez]

data from impact areas on moon, discovery rate, increase in counts with improvement in instruments are some factors:

http://www.lsst.org/lsst/publi...

while video is great it is biased

[SergeyKurdakov6434]

First, Scott does not mention, that most dangerous asteroids are found

>95% of 1 km size asteroids
>90% for 500 m size asteroids
~60-70% 300 m size asteroids

so yes, we know 1% of asteroids, but still - the danger now for a person to be killed by asteroid is more than 100 times less, than it was two decades ago

another problem with his video, that he omits to mention, that inner asteroids are either harmless, or if they intersect earth orbit - they could be tracked at dusk/dawn ( just like venus is visible - and venus is quite far from being able to hit earth, so closer asteroids and relatively big asteroids are easier to find )

then about finding inner asteroids with space crafts - it is not just B612 foundation, which deals with that , but there are other proposals

http://arxiv.org/abs/1503.0794... - which is really cheap ( though idea requires some more development )
or http://xxx.lanl.gov/abs/1501.0... neocam - the paper has a proof that it is somewhat more realistic than B612 proposal and is not less efficient.

Re:while video is great it is biased

[Dcnjoe60]

...so yes, we know 1% of asteroids, but still - the danger now for a person to be killed by asteroid is more than 100 times less, than it was two decades ago

Actually, the danger to a person being killed by an asteroid is not changed. That won't happen until some technology is developed to deal with them. But, at least we would know the end is coming.

Re:while video is great it is biased

[Dcnjoe60]

Whether we knew/know about an asteroid strike doesn't change whether the strike will occur. As such, the actual likelihood of an asteroid hit is the same, either way. What has changed is our knowledge that it is going to occur.

Put differently, there are a finite number of asteroids in the solar system. If one othem is on a trajectory that will eventually impact the earth, the likelihood of an earth impact is unchanged whether we know it or not. Likewise, if none of them are on a trajectory to impact earth, the likelihood of an earth impact is unchanged whether we know it or not.

At this point in time, there are only two options - either the earth will be hit or it will never be hit. The more we know about the asteroids and their trajectories does not change those results (unless by knowing, we have a means to divert the collision, which currently, we can't).

Answer:

[avandesande]

You Could See Asteroids In the Night Sky...

Re:See with what equipment

[thrich81]

There is one asteroid, Vesta, which can be seen every couple of years or so by people with decent (not exceptional) naked eye eyesight. I've seen it a few times, you just need to know exactly where to look and a have a bit of stargazing experience at picking out faint objects. Its last opposition was in April 2014. Without looking it up I'd guess the next is in late 2015 or early 2016.

Re:How do we know we've only discovered 1% of NEAs

[khallow]

The distribution of asteroids that we can detect follow a power law: for a given cross-sectional area, the number is crudely inversely proportional. This not only holds for the biggest ones which we can observe in telescopes, but also meteorite impacts with the Earth and Moon. So we have estimates of asteroid populations by size from the largest to well below the minimum size which can cause harm to us on Earth.