<p>This is because there are many more small NEOs than there are large ones and the larger ones are easier to find and so were found first. The numbers of NEOs follow what's know as a power law distribution with an exponent of ~1.75. This means that given the roughly factor 7 difference between 140m and 1000m NEOs, there will be 7^1.75 = ~31 times as many 140m NEOs as 1000m NEOs. This is shown in this plot below. <a href="https://i.sstatic.net/Z8KoS.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Z8KoS.png" alt="NEO size-frequency distribution"></a> We estimate there are about 950 NEOs 1km or larger and about 25,000 NEOs larger than 140m. We have found over 93% of the 1+km NEOs and so there aren't many left to find. In comparison, over 2/3rds of the 140-1000m NEOs still remain to be found, most in the 140-300m size range. However this improved considerably since even 2010 when about 82% of the population was still to be found.</p>

CC BY-SA 4.0
2019-02-12T17:01:17.683Z
I just want to mention that the Gaia downloads should cause a jump in this data.
Jack R. Woods
CC BY-SA 4.0
2018-12-07T23:49:02.317Z
2018-12-07T23:49:02.317Z
astrosnapper
<p>Near Earth Objects (NEO's) have been mapped by NASA and JPL since 1990's. The graph below shows how many of these potential planet-killers have been found and classified over the years. I am curious as to why there have been so many more 140 meter to 1 km NEO's discovered, as opposed to NEO's with a diameter of 1 km or more. I think it is as simple as there are just more "smaller" objects left over from the formation of the solar system? Am I correct in saying this, or are there deeper astronomical processes at play here?</p>

<p><a href="https://i.sstatic.net/G5AKg.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/G5AKg.jpg" alt="enter image description here"></a></p>

<asteroids><near-earth-object>
Discovery of Near Earth Objects (NEO's)
Jonathan L.
# Discovery of Near Earth Objects (NEO's)

(Asked by: username_0 on 2018-12-07)

Near Earth Objects (NEO's) have been mapped by NASA and JPL since 1990's. The graph below shows how many of these potential planet-killers have been found and classified over the years. I am curious as to why there have been so many more 140 meter to 1 km NEO's discovered, as opposed to NEO's with a diameter of 1 km or more. I think it is as simple as there are just more "smaller" objects left over from the formation of the solar system? Am I correct in saying this, or are there deeper astronomical processes at play here?

[![enter image description here](https://i.sstatic.net/G5AKg.jpg)](https://i.sstatic.net/G5AKg.jpg)

**Tags:** asteroids, near-earth-object


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## 1 answers

### Answer by username_1 on 2018-12-07. Score: 3 | Accepted answer

This is because there are many more small NEOs than there are large ones and the larger ones are easier to find and so were found first. The numbers of NEOs follow what's know as a power law distribution with an exponent of ~1.75. This means that given the roughly factor 7 difference between 140m and 1000m NEOs, there will be 7^1.75 = ~31 times as many 140m NEOs as 1000m NEOs. This is shown in this plot below. [![NEO size-frequency distribution](https://i.sstatic.net/Z8KoS.png)](https://i.sstatic.net/Z8KoS.png) We estimate there are about 950 NEOs 1km or larger and about 25,000 NEOs larger than 140m. We have found over 93% of the 1+km NEOs and so there aren't many left to find. In comparison, over 2/3rds of the 140-1000m NEOs still remain to be found, most in the 140-300m size range. However this improved considerably since even 2010 when about 82% of the population was still to be found.

> **Comments:**
> **username_2**: I just want to mention that the Gaia downloads should cause a jump in this data.  

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