Key Points
- A possible object was first reported by Purple Mountain Observatory (D29).
- AGO Modra (118) submitted Follow-up observations
- The “object” given the designation 2018 SV13.
- There only 26 hours of observations of this asteroid.
- ESA posted 2018 SV13 to the NEODyS: Risk page
- NASA JPL did not list 2018 SV13 on Sentry: Earth Impact Monitoring Page(NASA JPL)
- Media outlets reported it this asteroid had ‘Non-Zero’ Probability Of Hitting Earth.
- 2018 SV13 had a maximum rating of 0 on Torino Impact Hazard Scale, therefore, we can say “The likelihood of a collision is zero, or is so low as to be effectively zero”
- There was a fail attempt to find precovery observations on archival images.
- P. Veres examined AGO Modra (118)’s images and came to the conclusion 2018 SV13 was not real.
- On 2020 July 17, at 14:31 UT, the Minor Planet issued ” MPEC 2020-O10: RETRACTION OF 2018 SV13 .”
Discovery
The story all begins with the discovery, asteroid 2018 SV13, which was first reported by Purple Mountain Observatory (D29). They submitted using the temporary designation X60263. Pop Culture depicts astronomer sending in photos or racing down winding mountain roads with their images. However, the reality is that observers do not submit their images, report the when, and were of the object. The work of other observers confirms their observations. In the casa of 2018 SV13, follow-up observations were provided by AGO Modra (118).
Placement on the ESA Risk List
There only five observations over 26 hours of observations of the asteroid, three from Purple Mountain Observatory, and two from AGO Modra. There were only five observations over 26 hours of observations of the asteroid, three from Purple Mountain Observatory, and two from AGO Modra. The last two observations had high residuals(aka they were poor). This created highly uncertain in the orbit. As a result, ESA’ posted 2018 SV13 to the NEODyS: Risk page with 1 in 3.6 million risks. NASA JPL performs a similar analysis. 2018 SV13 was not listed to their risks; table. Given the fact of low risk, this is not unusual.
The Retracted of 2018 SV13
Clickbait media outlets reported this asteroid had a ‘Non-Zero’ Probability of Hitting Earth. Sometimes objects will escape noticed in images. Therefore astronomers will sometime take another look at images looking where the steroid could be. Any observations predating discovery, are referred to as precovery observations. M. Micheli performed a fail attempt to find precovery observations on archival images, where 2018 SV13 should have been. P. Veres examined the AGO Modra (118)’s and concluded that 2018 SV13 “was not real.” On 2020 July 17 at 14:31 UT, the Minor Planet Center has Issued ” MPEC 2020-O10: RETRACTION OF 2018 SV13 “. This show2018 SV13 will not hit the Earth.
Orbit Determination
Astronomers search for orbits that place the asteroid in the sky where it was observed. No observation is perfect, and the amount the observations are off from orbit’s postdiction is called their residuals. The orbit with the lowest residuals is known as the best-fit orbit.
The Uncertainty Region
However, there is a range of orbits that will satisfactorily fit the reported observations, comprising an uncertainty region. To find the uncertainty region, they calculated a large number of orbits, each with a virtual asteroid. There will be a range of orbits that will satisfactorily fit the reported observations, comprising an uncertainty region. To find the uncertainty region, they calculated a large number of orbits, each with a virtual asteroid filling this region. For asteroids recently observed, this region will be tiny; however, given the fact that each virtual asteroid as a different orbital period, this region will grow over time. Generally speaking, the uncertainty region grows “longer” and wraps one or more timing around the Sun. If Earth enters this pass-through this region, we have a non-zero probability of impact. However, the “real” asteroid could on the other side of the Sun at the time.
Impact Risk Assessment
Astronomers add the gravitational effects of planets and large asteroids and the Yarkovsky effect to their calculation. To find the impact probability Astronomers add the gravitational effects of planets and large asteroids and the Yarkovsky effect to their calculation. To find the impact probability takes the number of virtual asteroids that impact the Earth(virtual impactors) and divide it by the total number of virtual asteroids(i.e., 1 in 3.6 million). Some would call this a “prediction” of impact. When in reality, it is a statement that an impact can not be ruled out. When a TV weather forecaster states there is a 1% chance of rain, it is a statement rain is very unlikely but possible.
The Purpose of Asteroid Risk Lists
Finally, we should state ESA and NASA post object to there asteroid risk list when they can not rule out an impact. This notifies NEO specialists that more data is needed. Objects posted to the risk lists will get additional attention. There will be precovery searches; there will search for more observations in The Isolated Tracklet File. This is a file kept by the Minor Planet Center, fill with observations that have not been linked to a known asteroid. Sometime and there may be an observing campaign. Note other non-Risk List objects may get this attention too.
Sources
- ESA Risk List
- ESA 2018SV13
- Guide to Minor Body Astrometry
- NEOCP Objects in 2018
- NEOCP Related Activities (Beta)
- MPEC 2018-U61 : DAILY ORBIT UPDATE (2018 OCT. 23 UT)
- MPEC 2020-O10 : RETRACTION OF 2018 SV13
- Recent Close Moon Approaches
- Introduction to Sentry: Earth Impact Monitoring
- Sentry: Earth Impact Monitoring (not there)
- Sentry: Earth Impact Monitoring[Removed Objects](2018 SV13 is not listed so therefore we are saying it was never listed.)
- Torino Scale
- The Tracking News – Earth’s Busy Neighborhood — 2018-10-23 — 2018-10-26 — 2019-10-17 — 2020-07-17
- Understanding Risk Pages by Jon Giorgini
Useful Links
- Asteroid Hazards: The View from Space(MPC)
- Don’t fear apocalyptic asteroids: you’re safer than you think
- Frequently Asked Questions For Impact Risk Assessment
- NEO Search & Follow-Up
- Palermo Technical Impact Hazard Scale
- Quantifying the risk posed by potential Earth impacts Steven R. Chesley (JPL), Paul W. Chodas (JPL), Andrea Milani (Univ. Pisa), Giovanni B. Valsecchi Icarus 159, 423-432 (2002) ( PDF )
Noted: this has been edited for grammar, clarity, and expanded.
The Asteroid 2020 NK1 Has Been Removed From Sentry: Earth Impact Monitoring