Speaker
Description
A common question from the public is: How many dangerous asteroids could potentially hit the Earth? Our response usually starts by mentioning that the number is size-dependent, because while there are numerous small asteroids, they pose less threat to life on Earth.
We have agreed to use two limits: 1km objects for global catastrophes and 140m objects for regional events.
In the last 25 years, I have counted at least 12 different estimates of the population number for various size limits [1,2,3,4,5,6,7,8,9,10,11,12]. Specifically, the estimates for the number of NEAs larger than 1km range widely, from fewer than 800 to over 1,200 (including error bars). A critical aspect in all models is the relationship between absolute magnitude and diameter, which depends on the (generally unknown) albedo.
There is a lower constraint for this number: the NEAs already discovered that are larger than 1km. However, this brings us back to the albedo problem. Are all these estimates consistent with this constraint?
The number of NEAs larger than 1km is a critical issue for the public, decision-makers, and scientists. Therefore, we should strive to reach a consensus based on the evidence.
Although I have not been involved in any of the previous works, I have closely followed the topic and am in a very favorable position to make a critical revision of all the estimates and propose a figure for this relevant number.
The aim of my presentation is to come up with a realistic number based on the models and observational constraints.
References:
1. D’Abramo, G. et al., 2001. A simple probabilistic model to estimate the population of near-Earth asteroids. Icarus 153, 214–217.
2. Bottke, W.F., et al., 2002. Debiased orbital and absolute magnitude distribution of the near-earth objects. Icarus 156, 399–433.
3. Stuart, J.S., Binzel, R.P., 2004. Bias-corrected population, size distribution, and impact hazard for the near-Earth objects. Icarus 170, 295–311.
4. Mainzer, A., et al., 2011. NEOWISE observations of near-earth objects: Preliminary results. Astrophys. J. 743:156
5. Harris, A.W., D’Abramo, G., 2015. The population of near-Earth asteroids. Icarus 257, 302–312.
6. Granvik, M., et al., 2018. Debiased orbit and absolute-magnitude distributions for near-Earth objects. Icarus 312, 181–207.
7. Morbidelli, A., et al., 2020. Debiased albedo distribution for near earth objects. Icarus 340, 113631
8. Harris, A.W., Chodas, P.W., 2021. The population of near-earth asteroids revisited and updated. Icarus 365, 114452.
9. Harris, A.W., Chodas, P.W., 2023. Update of NEA population and survey completion. In: ACM Conference in Flagstaff, #2519.
10. Nesvorný, D., et al., 2023. NEOMOD: A new orbital distribution model for near-earth objects. Astron. J. 166:55.
11. Nesvorný, D., et al., 2024. NEOMOD 2: An updated model of near-earth objects from a decade of catalina sky survey observations. Icarus 411, 115922.
12. Nesvorný, D., et al., 2024. NEOMOD 3: The debiased size distribution of Near Earth Objects. Icarus 417, 116110.