AB Aurigae: Possible evidence of planet formation through the gravitational instability

James Cadman, Ken Rice, Cassandra Hall

Research output: Contribution to journalArticlepeer-review


Recent observations of the protoplanetary disc surrounding AB Aurigae have revealed the possible presence of two giant planets in the process of forming. The young measured age of 1 − 4 Myr for this system allows us to place strict time constraints on the formation histories of the observed planets. Hence we may be able to make a crucial distinction between formation through core accretion (CA) or the gravitational instability (GI), as CA formation timescales are typically Myrs whilst formation through GI will occur within the first ≈104 − 105 yrs of disc evolution. We focus our analysis on the 4 − 13 MJup planet observed at R ≈ 30 AU. We find CA formation timescales for such a massive planet typically exceed the system’s age. The planet’s high mass and wide orbit may instead be indicative of formation through GI. We use smoothed particle hydrodynamic simulations to determine the system’s critical disc mass for fragmentation, finding Md, crit = 0.3 M⊙. Viscous evolution models of the disc’s mass history indicate that it was likely massive enough to exceed Md, crit in the recent past, thus it is possible that a young AB Aurigae disc may have fragmented to form multiple giant gaseous protoplanets. Calculations of the Jeans mass in an AB Aurigae-like disc find that fragments may initially form with masses 1.6 − 13.3 MJup, consistent with the planets which have been observed. We therefore propose that the inferred planets in the disc surrounding AB Aurigae may be evidence of planet formation through GI.
Original languageEnglish
Pages (from-to)2877-2888
Number of pages12
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Early online date6 Apr 2021
Publication statusPublished - 1 Jun 2021


  • astro-ph.EP
  • astro-ph.SR


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