Asteroids and comets belong to the small bodies of the Solar System. In the past, it was thought these categories were clearly distinguishable. Then objects with dynamically asteroidal orbits, but comet-like activity started to be discovered. This class of objects is also known as active asteroids. The activity of comets is caused by the sublimation of ice and accompanying dust removal. In the case of active asteroids, several possible mechanisms of activity accompanied by a mass loss are discussed. A meteoroid impact can also trigger observable activity. It is more likely that such a collision would involve a stream meteoroid which moves around the Sun in a corridor with a relatively much higher density of meteoroids than the density of sporadic meteoroids. In this work, we mapped the passages of the main-belt asteroids through the corridors of known meteoroid streams. By considering all of the reliably known main-belt asteroids and all of the mean orbits of known meteoroid streams, we found over 232 million of passages. A list of the dates of passages is provided for a period of the next ten years. In future, if an outburst of initially inactive asteroid occurs, one can quickly find whether the asteroid crossed any of the known meteoroid streams shortly before the outburst or not and hence evaluate whether the collision with stream meteoroid could be a possible trigger. In addition, we dealt with the determination of the enhanced probability of a collision between an asteroid in the main belt and a meteoroid which is a member of meteoroid stream. Firstly, we estimated minimum probability of collision of asteroid with meteoroid by considering the minimum flux. In this case, if meteoroids with masses larger than 10 kg were considered and if the typical radius of asteroid was 200 m, the mean time between two collisions would be about a century. Further, another probability estimate was made by identifying the known flux of Perseids with the flux of “mean” meteoroid stream. For typical radius of asteroid equal to 100 m and in case of meteoroids larger than 100 kg, we would get approximately 10-320 years as a mean period between two collisions. And this period would be shorter than about 10 years if the typical asteroidal radius was 500 m. Our estimates of the probability for some reasonable values of free parameters imply that a meteoroid impact cannot be excluded as a mechanism triggering the comet-like activity of a significant amount of known active asteroids. We cannot exclude, either, that the impact is the dominant mechanism of this triggering.
This work was supported by the VEGA - the Slovak Grant Agency for Science, grant No. 2/0009/22.
Good morning, I am thrilled
Good morning, I am thrilled by your work. I am curious how much might be reliable such predictions. Do you have any previous data, from past years, about the predictions stated and subsequently how did it go then. Is it possible to somehow quantify the reliability of predictions? Thank you in advance for your reply, ZB
Good evening :) Thank you for
Good evening :) Thank you for your questions.
The activity of comets is caused by the sublimation of ice and accompanying dust removal. In case of active asteroids, several possible mechanisms are discussed, for example ice sublimation and dust ejection (like in comets), fast rotation, meteoroid impact/collision, thermal fracture or dehydration, etc. However the activity can be triggered by several mechanisms operating together. That means it is slightly more complicated to identify the trigger of activity of an asteroid. Within this work we tried to focus on collisions with stream meteoroids as a possible trigger.
Of course, we cannot predict that given asteroid will be hit by a meteoroid during the passage through a given meteoroid stream. To somehow quantify the probability we took the approach similar to the approach of the police when they are trying to estimate how many traffic accidents occur in a country for a certain period of time. On the basis of past statistics, the police can predict that there will be approximately N accidents per month, but they cannot say which specific cars, when and on which road will have an accident. In this case we considered an asteroid of “mean” size, flux of “mean” stream, “mean” period of passage of asteroid through such stream… Unfortunately, these quantities are unknown, so we ended up with several free parameters. Maybe it would be better to call it a rough estimate.
We don’t know about any other predictions from the past. But we tried to apply this to several asteroids, which were discovered inactive, but later their activity was observed (for example 493 Griseldis, 6478 Gault or 62412 (2000 SY178)). We wondered whether their outburst might be triggered by an impact of a stream meteoroid. We mapped the passages of these asteroids through the known meteoroid streams a short time before their outburst (like in Tab. 1). In all of these randomly chosen cases a passage or few passages were found. So the collision cannot be ruled out as a trigger (however it is also true that it cannot be confirmed either). That’s why our conclusion was “only” that a meteoroid impact cannot be excluded as a mechanism triggering the activity of significant amount of active asteroids.
A comparison of the prediction with actual frequency of the outbursts is complicated by several circumstances. Our prediction is based on several free parameters. We tried to use as reasonable values as possible, but to be honest, we can only guess. Moreover, outburst may be triggered by a sporadic meteoroid, meteoroid of unknown stream or by other mechanism. In addition, we are not able to detect every outburst (an outburst may occur when the asteroid is above the horizon during daytime, not all asteroids are observed each year…). So it is difficult to answer the question on quantifying the reliability.
I am sorry, if it is too long, but I wanted to give you some context :)
MK
Thank you, thank you so much
Thank you, thank you so much for all your efforts to elucidate me the inconsistencies that might occur within your research area. I wish you all the best in your further work. Keep doing great job! :-)