Eta-Virginids: another asteroidal meteoroid stream

Eta-Virginids is a less-known meteor shower active in March. We investigated the meteoroids of this shower using fireball data from the European Fireball Network supplemented by video data of faint meteors. We first derived the criteria for assigning meteors to this shower. A fragmentation model was then applied to selected shower fireballs with good deceleration data and light curves. Meteoroid fragmentation strengths and bulk densities were derived and compared with three other showers. We have confirmed the four year periodicity in the activity of eta-Virginids and their presence in the 3:1 mean motion resonance with Jupiter. The orbital period of four years was directly measured for the fireballs. Fainter meteors showed somewhat longer periods but the shower is poor in faint meteors. No member fainter than magnitude +1 was observed instrumentally. The physical properties of meteoroids are different from cometary streams and are similar to the Geminids. The limiting fragmentation strength of 0.5 MPa and typical bulk density of cm-sized meteoroids of 1500 kg/m3 suggest that the parent body is a carbonaceous asteroid. Besides Geminids, eta-Virginids is another stream of asteroidal origin. Some small meteoroids have densities around 2500 kg/m3. Three asteroids of the sizes between 40 - 120 meters have been found to have similar orbits but their relation to eta-Virginids remains uncertain.

💡 Research Summary

The paper presents a comprehensive investigation of the Eta‑Virginids, a relatively obscure meteor shower active in March, with the goal of determining the physical nature and origin of its meteoroids. The authors combine data from the European Fireball Network (EN) spanning 2017–2025 with a dedicated high‑sensitivity video campaign conducted in March 2025.

First, they establish strict criteria for shower membership. By plotting geocentric radiants in both equatorial and Sun‑centered ecliptic coordinates, they identify a tight concentration (region A) with ecliptic latitude β = 4°–6° and ecliptic longitude offset λ − λ⊙ = 182°–191°. Meteors appearing between solar longitudes 350° and 3° (approximately March 10–23) and possessing orbital periods of 3.8–4.2 yr are classified as high‑confidence Eta‑Virginids. Wider regions (B and C) show much larger scatter in both radiants and periods and are excluded, although a few isolated cases fall within the defined limits by chance.

Second, the authors apply the semi‑empirical fragmentation model (Borovička et al. 2020) to a subset of fireballs with well‑measured deceleration and high‑time‑resolution radiometric light curves. The model simultaneously fits the maximum dynamic pressure (Pf), limiting fragmentation strength (σₗ), and bulk density (ρ). Results indicate a limiting strength of ≈ 0.5 MPa and an average bulk density of about 1500 kg m⁻³ for cm‑scale particles, with some smaller fragments reaching ≈ 2500 kg m⁻³. These values place Eta‑Virginid meteoroids in the same strength and density regime as the Geminids, and they are markedly stronger than typical cometary streams such as the Taurids.

Third, the activity pattern is examined. The fireball count per year shows a clear four‑year cycle, with peaks in 2009, 2013, and 2017, confirming earlier findings by Shiba (2018) and Jenniskens (2023). The video observations, limited to meteors brighter than magnitude +1, reveal that Eta‑Virginids are deficient in faint meteors; all four video‑identified shower members are brighter than +1 mag, while the majority of the 130 video meteors recorded during the campaign are fainter and belong to the sporadic background. This suggests that the stream is dominated by relatively large, dense particles and produces few sub‑centimeter meteoroids.

Finally, the authors search for potential parent bodies. Three near‑Earth asteroids with diameters of 40–120 m share orbital elements similar to the Eta‑Virginids and reside in the 3:1 mean‑motion resonance with Jupiter, the same resonance implicated in the stream’s dynamical evolution. However, no definitive link can yet be established.

In summary, the study demonstrates that Eta‑Virginids are an asteroidal meteoroid stream, characterized by high fragmentation strength, moderate bulk density, and a four‑year activity cycle tied to the 3:1 Jupiter resonance. Their physical properties closely resemble those of the Geminids, making Eta‑Virginids the second confirmed asteroidal meteor shower. The work underscores the value of combining precise fireball trajectory, deceleration, and radiometric data with fragmentation modeling to discern the nature of weak or poorly known streams, and it calls for future spectroscopic observations and dynamical studies to pinpoint the exact parent asteroid.