General · EdgepediaOctober 20, 20263 min read

Lucascavin family

The Lucascavin family is a very young asteroid family of only three known members in the inner main belt, produced by the breakup of a small parent body within roughly the last million years. It was discovered by David Nesvorný and David Vokrouhlický in 2006 and is named for its largest member, 21509 Lucascavin.

Key fact	Detail
Members	Three asteroids: 21509 Lucascavin (H = 15.06), (180255) 2003 VM9 (H = 17.21), and (209570) 2004 XL40 (H = 17.24)¹
Age	300–800 thousand years (Nesvorný & Vokrouhlický 2006); 500–1000 kyr by the later method of Pravec et al. (2018)²
Origin model	Rotational fission of the parent body, with the escaping secondary tidally split into the two small members²
Completeness	No other member with absolute magnitude H ≤ 18.3 exists; no new members found in two decades²
Location	Inside the Flora family region of the inner main belt, at a semimajor axis near 2.28 AU³^•¹

Discovery and membership

Nesvorný and Vokrouhlický identified the cluster in 2006 as a tight grouping of three asteroids sharing nearly identical osculating orbital elements: semimajor axis near 2.280–2.282 AU, eccentricity near 0.11, and inclination near 5.98 degrees¹. Because the family is so young, five of the six osculating orbital elements remain clustered, rather than the three proper elements used for older families².

The cluster is statistically real. Testing against synthetic Flora-family populations, the discoverers found that a chance three-body cluster this tight would occur with probability significantly less than one part in a million³.

Age and formation

Two age estimates exist. The discovery paper estimated 300 to 800 thousand years, with the large uncertainty due to the small size of the two small members and unconstrained magnitudes of the thermal accelerations in their orbits². Pravec and colleagues in 2018 calculated 500 to 1000 thousand years using a different method².

Rotational fission. Assuming the known population is complete, Pravec et al. argued that the estimated sizes of the members and the parent's approximately 5.79-hour rotation period might be enough for rotational fission of the parent object to explain the family. The difference from ordinary asteroid pairs is that the secondary escaping the primary after fission would itself have split into two components, the small members (180255) 2003 VM9 and (209570) 2004 XL40².

A starving family

The Lucascavin family has a limited population: no new members were discovered in the two decades after its identification². A 2024 study using the Catalina Sky Survey found that no asteroid with absolute magnitude H ≤ 18.3 accompanies the three known members, supporting the three-body fission model; the archetypal asteroid pair Rheinland–Kurpfalz shows a similar result². All three members were detected by CSS during its phase 2 operations¹.

The namesake asteroid

Its rotation period is about 5.78 hours⁴.

Context among young families

The Lucascavin family belongs to the class of very young families, those with ages under 1 million years, whose ages are determined by the backward integration method; other examples include Emilkowalski, Datura, Schulhof, and Hobson⁵. It sits within the Flora family region of the inner main belt³. Later surveys of young families note it as an example of a family with only three known members, and it remains one of the smallest known young families⁶.

References

Initially written Oct 20, 2026 · Edited: Oct 25, 2026