Vesta family
A large inner-belt family of bright V-type asteroids originating from 4 Vesta.
The Vesta family (also called Vestian, with FIN number 401) is a large group of asteroids in the inner main belt, centered around its largest member, 4 Vesta. With over 15,000 known members, it is one of the biggest asteroid families. Most of its members are bright V-type asteroids, often referred to as vestoids.
The family includes 4 Vesta itself—the second most massive asteroid, with an average diameter of about 530 km—along with many much smaller bodies, most under 10 km in diameter. The brightest among these smaller members, 1929 Kollaa and 2045 Peking, have an absolute magnitude of 12.2, which corresponds to a radius of roughly 7.5 km if they share the same high albedo as 4 Vesta.
The family formed from a large impact on 4 Vesta, likely at its giant south-polar crater. These asteroids are thought to be the source of the HED meteorites. A few members are J-type asteroids (related to V-type), believed to come from deeper layers of Vesta’s crust and similar to diogenite meteorites.
A 1995 hierarchical clustering method (HCM) analysis by Zappalà identified 235 core family members. Their proper orbital elements fall within approximate ranges, and at the present epoch, the osculating orbital elements of these core members also have defined ranges. A 2005 search of the AstDys proper-element database, covering 96,944 minor planets, found 6,051 objects (about 6% of the total) within the Vesta-family region defined by that table.
Some large bodies with similar orbital elements are not true Vestians. Spectroscopic analysis shows they are interlopers—not of the V or J spectral class—including 306 Unitas, 442 Eichsfeldia, 1697 Koskenniemi, 1781 Van Biesbroeck, 2024 McLaughlin, 2029 Binomi, 2086 Newell, 2346 Lilio, and others.
- Designation
- FIN: 401
- Principal body
- 4 Vesta
- Number of members
- more than 15,000 known members
- Largest member diameter
- 530 km (mean diameter of 4 Vesta)
- Brightest members
- 1929 Kollaa and 2045 Peking (absolute magnitude 12.2)
- Typical member size
- below 10 km diameter
- Core members found by zappala 1995
- 235
Lore & Background
The Vesta family originated from an impact on asteroid 4 Vesta, with the giant south-polar crater the likely impact site. The family is thought to be the source of the HED meteorites. The family includes a few J-type asteroids, related to the V-type, which are thought to have come from deeper layers of Vesta's crust and are similar to diogenite meteorites. A HCM numerical analysis by Zappala 1995 determined a large group of 'core' family members with proper orbital elements lying in approximate ranges; at the present epoch, the range of osculating orbital elements of these core members is also given. That analysis found 235 core members. A search of a recent proper-element database (AstDys) for 96,944 minor planets in 2005 yielded 6,051 objects (about 6% of the total) lying within the Vesta-family region.
Reader's Guide
The Vesta family is significant as one of the largest asteroid families, with over 15,000 known members, and as the likely source of the HED meteorites, linking it directly to samples studied on Earth. The family's origin from a major impact on 4 Vesta, the second-most-massive asteroid, provides insight into collisional processes in the inner asteroid belt. The presence of J-type asteroids suggests that the impact excavated material from different depths of Vesta's crust, offering a window into the body's internal structure. The family's large number of small vestoids (below 10 km) and its bright V-type spectral signature make it a distinct and well-studied group. Interlopers such as 306 Unitas and 442 Eichsfeldia, identified by spectroscopic analysis, show that not all objects with similar orbital elements belong to the family, highlighting the importance of spectral classification in family studies.
Did You Know?
- The Vesta family is one of the largest asteroid families, with more than 15,000 known members.
- Some large Vestians, such as 306 Unitas, are interlopers and not of the V or J spectral class.
More in Notable Asteroids, Part 4 1-24
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