Current Status and Statement of the Problems. Indeed, the behavior of the object incoming into the Earth's atmosphere depends critically on its mass/size, velocity and composition. It is known, that icy body penetrating the Earth's atmosphere very likely exploded in the atmosphere at low altitude, while a strong rocky object will penetrate deeper and impact the surface. Thus, the preassigned physical and dynamical properties of an object allow forecasting the circumstances of its possible entry and subsequent consequences.
In order to identify the properties of a PHA, it is necessary to distinguish between real asteroids and extinct comets. The aim of the project is the solving this task and the known 1651 PHAs are the objects of study.
Seen from distance, inactive comets do not look outwardly differ from primordial asteroids. So, to implement the aim, both the method for identifying inactive comets among asteroids developed in the Institute of Astrophysics and the complex observations of PHAs by telescopes will be employed. In addition, the systematic observations of large bodies entering the Earth's atmosphere will be carried out, as well as the reduction of data and determination their dynamical and physical parameters.
The method of identification of extinct comets is based on the assumption that those asteroids that are really dormant cometary nuclei move on comet-like orbits and have associated meteoroid streams that were formed during the period of past activity of these comets. To achieve this, the orbital evolutions of PHAs moving on comet-like orbits have to be investigated, the Earth-crossing conditions for each object-candidate has to be determined and the theoretical properties of meteoroid streams associated with objects-candidates calculated. A search for existing active meteor showers close to predicted ones has then to be conducted using all available observational data. If an association of the theoretical showers from a candidate with an established meteoroid stream is confirmed, we conclude that it is very likely to be cometary in nature.
Observations of any PHA under investigation to obtain both astrometric and photometric data will provide a significant further indication of the cometary or asteroidal nature of the object. From the dynamical and physical properties of PHA that has been obtained, a qualitative assessment or forecast of the consequences to the Earth of any impact will be determined.
The Main Goals of the Project are:
a) Determination of the fractions of primordial asteroids and inactive comets among 1651 PHAs, discovered till 2016, on the base of investigation of their orbital evolution and examine their association with existing meteoroid streams;
b) Carrying out astrometric and photometric observations of available PHAs by telescopes of GisAO and SAO as well as large bodies entered the Earth’s atmosphere by video equipment; and processing of obtained data;
c) Determination of the dynamical and physical properties of observed objects and setting of the candidates to inactive comets;
d) Combining and analyzing results, confirmation of the number of extinct cometary nuclei among real asteroids and set up qualitative assessment of consequences of possible impacts with potentially hazardous objects;
d) Presentation of the results at the international conferences, publication of the results as papers and as a catalogue and supply it to experts employed in corresponding areas.
Expected Results and Their Application
The implementation of this Project will lead to finding of a fraction of extinct cometary nuclei among PHAs. The new data on dynamical and physical properties of PHAs will be obtained, which will be additional evidences of their origin and strongly support a conclusion on cometary or asteroidal nature of each object under investigation. The distinguishing of PHAs by composition on icy and stone (iron) bodies with provision for their sizes will provide a forecast of consequences of their possible impacts with the Earth. The new data on dynamical and physical features of large bodies incoming to the Earth’s atmosphere on the base of their video observations will be obtained as well. The results will be published as a catalogue which will be helpful for specialists studying the small bodies of the Solar System and their relations, especially for experts developing the methods of mitigation strategy of the space treats.
The project’ influence on progress in this area. New inactive comets that will be found among PHAs, new interrelations of asteroids and comets which will be set up within the proposed investigation, as well as studying of their physical-dynamic properties will stipulate the best understanding of their nature and a new insight into a formation of minor bodies of the Solar System.
Scope of Activities. For the achievement of the project goals the following activities will be implemented:
- calculation of secular variations of orbital elements of the PHAs, and finding of their Earth-crossing conditions;
- determination of the radiants, velocities, orbits of theoretically predicted showers associated with the PHAs;
- search for the active observable showers close to predicted ones using the published data on observations and our own data, thus, in the case of the showers identification, a finding of new dormant comets among the PHAs;
- carrying out of astrometric and photometric observations of available PHAs by telescopes, and of large bodies incoming to the Earth’s atmosphere by video equipment;
- reduction of the obtained data, determination of dynamical and physical properties of observed objects;
- analyzing of results, a final classification of PHAs on icy and stone bodies by dynamical and physical features;
- publication of results as a catalogue, papers and presentation to the international scientific community.
The Institute of Astrophysics of the Academy of Sciences of the Republic of Tajikistan is responsible for all planned works of the proposed project.
