4. Conclusions
The estimated τ values are short (∼ 1 My) with few exceptions. These exceptions apply to only three objects: 240 2008 KV42, 2011 MM4 and (336756), whose median lifetimes are longer than 10 My. Of these short τ values, the dynamical lifetime of 2004 NN8 is exceptionally short (-0.3 My and 0.4 My). In many cases, τ values of the past and future are comparatively different – this is visible in Fig. 245 2 and 3. Such behaviour suggests the existence of various dynamical regimes (e.g. chaotic zones) in their orbital motion. Additionally, the Yarkovsky effect’s dependence on estimated lifetimes is evident. A more detailed discussion of this dependency was elaborated in our previous stud250 ies (Kankiewicz and W lodarczyk, 2017). Presently, a lack of detailed observational data produces limitations in the thermal model, thus these limitations only raise speculation on this effect’s ability to potentially extend τ values. We hope that the dynamical model with applied thermal 255 forces can be improved on after new observations provide the means to update physical and rotational properties. It is worth pointing out that acquiring such diverse parameters is a complex task and will rather be based on combining the results of ground observations and space missions 260 observing asteroids. For the purpose of this paper, it was necessary to collect this information from various bibliographic sources and services (JPLDB, MPC). For such purposes, a dedicated, complete database of these parameters would be beneficial.
