Identification and Dynamical Properties of Asteroid Families

Abstract

Asteroids formed in a dynamically quiescent disk but their orbits became gravitationally stirred enough by Jupiter to lead to high-speed collisions. As a result, many dozen large asteroids have been disrupted by impacts over the age of the Solar System, producing groups of fragments known as asteroid families. Here we explain how the asteroid families are identified, review their current inventory, and discuss how they can be used to get insights into long-term dynamics of main belt asteroids. Electronic tables of the membership for 122 notable families are reported on the Planetary Data System node.Comment: Asteroids IV chapte

Characterizing the original ejection velocity field of the Koronis family

“…The Koronis family is located in a relatively dynamically quiet region, where, with the exception of the 3ν 6 − 2ν 5 = g + 2g 5 − 3g 6 secular resonance, a pericenter resonance that mostly modifies asteroid eccentricities, no other major mean-motion or secular resonance exists (Bottke et al, 2001;Carruba et al, 2013;Nesvorný et al, 2015). The long-term dynamics of the Koronis family should therefore had had a minor influence in the spreading in proper i of members of the family, as we will also further investigate later on in this paper.…”

“…Despite being a relatively old family (2.65 Gyr at most if one use standard values for the parameters describing the Yarkovsky force , see Carruba et al (2015b) and references therein for more detail on this age estimate), the current dispersion in proper i of Koronis family members could therefore still contain traces of information on the original ejection speeds (Cellino et al, 2004(Cellino et al, , 2009 To investigate this hypothesis, we first obtained an estimate of the current family members. We used data published in Nesvorný et al (2015) for the Koronis family using the Hierarchical Clustering Method (Zappalà et al, 1990), and a velocity cutoff of 45 m/s in the (a, e, sin(i)) domain (see Table 2 in Nesvorný et al (2015) for further details). Since there are two subfamilies inside the Koronis group, the Karin cluster (Nesvorný et al (2002) and the Koronis 2 family (Molnar and Haegert, 2009), we eliminated these two subgroups from the list of Koronis members.…”

The young Datura asteroid family

“…While we could use magnitude distribution as our fundamental quantity, conforming to the bias dependence on H, we opted to use size D distribution. This is a more traditional description of populations of fragments in asteroid families (e.g., Masiero et al 2013Masiero et al , 2015Nesvorný et al 2015). In order to relate sizes D to magnitudes H, we use the conventional functional form D = 1329 × 10 −0.2H / √ p V (e.g., Pravec & Harris 2007) with p V = 0.24 (Sect.…”

“…For this particular goal we would like to have available a snapshot of the family emerging right from the formation event. This is because as time passes, several dynamical processes influence the overall configuration of asteroids in the family, their surface properties and their rotation states (e.g., Nesvorný et al 2015;Vokrouhlický et al 2015). Our ability to determine, or at least constrain, ages of asteroid families, could be therefore highlighted as one of the important achievements of the past decade or so.…”

“…This 5.75 Myr old family was formed when a 5.8 km size impactor blasted a 33 km size parent body by hitting it at 5−6 km s −1 velocity producing A&A 598, A91 (2017) about hundred fragments larger than 2.5 km (e.g., Nesvorný et al 2006a). A couple of similar, but less well characterized families, of this category were discovered in the subsequent years (e.g., Nesvorný et al 2015). However, even the Karin family was found to be affected by traces of dynamical evolutionary processes (e.g., Nesvorný & Bottke 2004;Carruba et al 2016b).…”