3 Is asteroid 1995 CS a fragment of Adonis?

In February 1995, using the Spacewatch telescope at the Kitt Peak observatory, Jedicke (1995) discovered a very faint asteroid of an absolute magnitude H=25 when it passed near the Earth at a distance of about 2 million km. The equivalent diameter d of 1995 CS, calculated using the following expression (Bowell & Lumme 1982)

$$\log d=3.12-0.2H-0.5\log p,$$ (4)

for a assumed albedo p=0.08, is equal to 50 m, wheras that of Adonis is equal to 0.8 km. It turned out that 1995 CS has the following orbital elements (Marsden 1995):

a=1.900 AU,   e=0.769,   q=0.439 AU,

$$i=2.60^{\circ}, ~ \Omega=135.7^{\circ}, ~ \omega=252.2^{\circ}, ~ \pi=27.9^{\circ}.$$

They are very similar to that of Adonis, with their directions of perihelion $(\pi=\Omega+\omega)$ differing by only about 5$^{\circ}$, but their longitude of ascending nodes $(\Omega)$ and arguments of perihelion $(\omega)$ differ substantialy being in quite different phases of their precession cycles.

The similarity in the directions of perihelion, semi-major axes, eccentricity, and perihelion distances of these two objects imply that they separated from a common body at an earlier time or the smaller 1995 CS detached from the larger Adonis (Steel 1997). In order to investigate possible genetic relationship of the Adonis and 1995 CS, Steel (1997) performed a series of back integrations of the orbits of Adonis and 1995 CS over the time span of $\sim$55 000 yr and came to the conclusion that these two objects might have had identical orbits at least $\sim$30 000 yr ago and therefore:

1) the small asteroid 1995 CS may be a fragment of the larger body (2101) Adonis, which by then represented an extinct or dormant cometary nucleus, or

2) as for 1995 CS, Adonis is itself a fragment of a larger cometary body yet to be discovered, or that might be known but wandered into a sufficiently different orbit, or

3) it is possible that Adonis and 1995 CS do not share a common origin, but occupy similar orbits in the present epoch merely by chance.

Our back integration of the orbit of 1995 CS over $\sim$15 000 yr performed by the Halphen-Goryachev (Goryachev 1937) method shows that 1995 CS is a quadruple-crosser of the Earth's orbit for the same values of the argument of perihelion $(\omega)$ as Adonis (Fig. 1). Moreover, it was found that the orbital elements of 1995 CS coincide nearly with the theoretical ones of day-time $\chi$-Capricornids (Table 1). Therefore it seems that 1995 CS belongs to the meteoroid stream associated with Adonis. At the time of its discovery, the radius-vector of the ascending node of 1995 CS was equal to $\sim$1.0 AU, and so using 1995 CS' orbital elements, for the point of minimum distance from the Earth's orbit we calculated the theoretical geocentric radiant and velocity equal to:

$$L_{\odot}=315.7^{\circ}, ~ \alpha=310.8^{\circ}, ~ \delta=-21.1^{\circ}, ~ V_{g}=24.9 ~\rm km~s^{-1},$$

which correspond to the geocentric radiant and velocity of the day-time $\chi$-Capricornid meteor shower associated with Adonis (see Table 2). On these grounds we may conclude that 1995 CS probably is a fragment of Adonis, and belongs to the stream meteoroids producing $\chi$-Capricornid meteor shower.

The membership of 1995 CS to the day-time $\chi$-Capricornid meteor shower shows that meteoroid streams may be populated also by large bodies of several tens of meters in diameter. Therefore, small extinct comets might be searched for along the orbits of meteoroid streams during periods of meteor shower activity. This inference is confirmed by the detection of 17 objects of some meters to some tens of meters, which passed within a few million km of the Earth. They were observed by Barabanov et al. (2001) during the period of activity of the Capricornids, Perseids, Leonids, and Coma Berenicids meteor showers, near the radiant positions of these showers, using 60-cm and 1-m telescopes with CCD-cameras ST-6, at the Zvenigorod (Moscow district) and Simeiz (Crimea) observatories of the Institute of Astronomy, Russian Academy of Sciences.