Abstrakt
Context. Pairs of asteroids, that is, couples of single bodies on tightly similar heliocentric orbits, were recently postulated as a new category of objects in the solar system.
They are believed to be close twins to binary and multiple systems. Aims.
Ages of the known pairs range from about 15 kyr to nearly a million years. Beyond the upper limit, the pairs disperse in the background population of asteroids and become difficult to detect.
Below the lower limit, the pairs should be easily recognizable if they exist and are discovered by surveys. Using the available data, we analyze the possible existence of very young asteroid pairs with clearly proven ages <= 10 kyr.
Methods. We searched for candidate very young asteroid pairs in the current catalog of asteroid orbits.
After a preliminary analysis, we selected the most promising case of the small asteroids (87887) 2000 SS286 and (415992) 2002 AT49. We collected photometric observations to determine their rotation periods and absolute magnitudes.
Results. The rotation period of (87887) 2000 SS286 is 5.7773 +/- 0.0004 h.
HR = 14.99 +/- 0.04 and HR = 16.24 +/- 0.03 for the primary and secondary components. A transformation to the visible band provides H = 15.44 +/- 0.05 and H = 16.69 +/- 0.04.
These two asteroids experienced a very close encounter, probably a formation event, some 7.4 +/- 0.3 kyr ago. The formal extension of our numerical runs backward in time reveal that these close encounters may have continued, starting from similar or equal to 45 kyr ago.
However, based on tests using synthetic fission events, we argue that the older age solutions might be the true solution only at similar or equal to (10 15)% level, assuming their low initial separation velocity is of between 10-20 cm s(-1). This means that 87887-415992 probably is the youngest known asteroid pair in our dataset with a reliable determined age.