Eta Corvi

Debris disks

Image of the debris disk with the REASONS survey^[15]

Eta Corvi possesses two dust disks. The cold outer disk is located at 150 au, is 50 au wide, and is inclined at 40° from face-on orientation.^[15] The warm inner disk is located within a few au of the star.^[14] The temperature of the cold dust is around 40 K, while the temperature of the warm dust is 300–400 K.^[14][16]

Excess dust surrounding Eta Corvi was first identified by the IRAS satellite through detection of an excess of infrared radiation from the star.^[17] Spectral energy distribution data suggested the presence of dust populations with different temperatures.^[18][16] The dust was first directly imaged in 2005, revealing a ring of cold dust with a radius of about 150 au, and a relatively empty inner cavity within 100 au possibly cleared by a planetary system,^[16] a result supported by subsequent submillimetre observation attempts.^[19][14] The warm dust component was found to likely reside within a few au of the star.^[20][14]

The dust within the outer disk cannot be primordial, as collisions between dust grains would break them into sufficiently small grains that can then be removed by radiation pressure. This suggests the dust is constantly replenished by collisional cascade, where collisions between planetesimals break large bodies into objects of various sizes, including dust. The inferred initial total planetesimal mass is around 20 Earth masses.^[16]

The warm dust disk component around Eta Corvi is notable for being more luminous than the maximum theoretical luminosity of the disk, derived from collisions between planetesimals formed within the disk itself.^[21] Additionally, the composition of the warm dust appears to resemble cometary materials, with primitive silicates not processed by aqueous alteration, as well as carbon-bearing species and water. Evidence of silica dust has also been detected, indicating high velocity collisions on the order of 5–10 km/s.^[22] These may hence be explained by an influx of planetesimals from a reservoir in the outer system migrating into the inner system before being destroyed by collisions, producing the observed dust.^[21] The warm dust emission appears to remain stable over 30 years, suggesting that the inner disk is efficiently replenished.^[14] The transport of outer disk planetesimals to the inner system may involve a steady state configuration of planets scattering materials inwards, or a one-off event analogous to the Late Heavy Bombardment (LHB) involving instability between planets.^[22][14] Observations of the outer disk favors the steady state model, as an LHB-like instability would have resulted in a broader outer disk.^[23]

The debris disks of Eta Corvi has been imaged by the James Webb Space Telescope (JWST) on 20 May 2025.^[24] The results have been presented at the 247th Meeting of the American Astronomical Society, the 25.5 micrometre imaging revealing a much more compact disk than the outer disk, possibly suggesting a quiet collisional history in the outer disk itself.^[25] As of March 2026, these results have not yet been published.

Planets

Currently, no planet around Eta Corvi has been detected. Radial velocity measurements have ruled out companions with masses down to 6 Jupiter masses orbiting within 2000 days (~3 au).^[26][27][23]

Several papers have made predictions of planets based on the distribution of dust disks in the system. The transportation of planetesimals into the inner system may require one or more perturbing planets, and there may also be an inner planet struck by the planetesimals to produce the observed warm dust. Lisse et al. (2012) predicted a migrating giant planet orbiting at 100–150 au, and a rocky planet less massive than Earth based on impact velocity and escape velocity constraints.^[22] Marino et al. (2016) proposed either a low-mass planet embedded within the outer disk, a single perturber orbiting near the disk's inner edge, or a chain of planets with masses between 3–30 Earth masses, and in the case that the warm dust is produced by impacts on a planet, the paper predicted a 4–10 Earth masses planet based on production of sufficient debris to remain detectable over long time.^[23] Pearce et al. (2022) predicted a single planet sculpting the debris disk with a mass of ≥0.34 Jupiter masses at 104 au.^[28]