Images of Embedded Jovian Planet Formation At A Wide Separation Around AB Aurigae (2204.00633v1)

Abstract: Direct images of protoplanets embedded in disks around infant stars provide the key to understanding the formation of gas giant planets like Jupiter. Using the Subaru Telescope and Hubble Space Telescope, we find evidence for a jovian protoplanet around AB Aurigae orbiting at a wide projected separation (93 au), likely responsible for multiple planet-induced features in the disk. Its emission is reproducible as reprocessed radiation from an embedded protoplanet. We also identify two structures located at 430-580 au that are candidate sites of planet formation. These data reveal planet formation in the embedded phase and a protoplanet discovery at wide, > 50 au separations characteristic of most imaged exoplanets. With at least one clump-like protoplanet and multiple spiral arms, the AB Aur system may also provide the evidence for a long-considered alternative to the canonical model for Jupiter's formation: disk (gravitational) instability.

Overview of Jovian Planet Formation Around AB Aurigae

The paper titled "Images of Embedded Jovian Planet Formation At A Wide Separation Around AB Aurigae" presents substantial evidence supporting the existence and characteristics of a protoplanetary formation process around the young star AB Aurigae. This research leverages high-contrast imaging techniques to provide direct observations of a forming Jovian-like planet, labeled as AB Aur b, utilizing data sources from both ground and space-based telescopes such as the Subaru Telescope and the Hubble Space Telescope.

The paper focuses on the detection of AB Aur b, a protoplanet located at a significant distance from its host star, approximately 93 astronomical units (au), which challenges the traditional understanding of planet formation models, specifically the core accretion model usually associated with relatively close planetary orbits. The wide separation of AB Aur b indicates that the alternative disk instability model, which allows planet formation through rapid gravitational collapse at larger distances, could be more applicable here.

Key Findings

• Detection and Imaging: The protoplanet AB Aur b was consistently imaged in multiple datasets from SCExAO/CHARIS and HST/STIS over several years. The protoplanet demonstrates characteristics that differentiate it from typical disk structures, showing a changing position angle consistent with orbital motion around its star.
• Morphology and Separation: The protoplanet is located at a separation of about 93 au from AB Aurigae, with observations suggesting an extended rather than a point-like morphology, possibly indicating surrounding circumplanetary material.
• Emission Sources: Various analyses were performed to deduce the emission characteristics of AB Aur b, which suggest that it is not just a product of scattered starlight. Its spectral energy distribution can be modeled by a dusty low-gravity atmosphere or by a smooth blackbody at about 2200 K. The planet's effective luminosity and size resemble those typical of large gas giants.
• Alternative Formation Mechanism: The presence of AB Aur b supports the hypothesis that disk instability could be a viable planet formation mechanism at play, given the protoplanet's separation from the host star and its interaction with the surrounding disk structure, which include spiral arms that are indicative of gravitational instability.

Implications

The implications of this paper are manifold:

1. Understanding Planet Formation: This work provides crucial insights into gas giant formation in protoplanetary disks, especially in the context of wide-orbit planets. The findings provide empirical evidence supporting disk instability as a valid formation pathway, a model often debated due to its inconsistent compatibility with conventional observations of smaller-scale separations.
2. Astrophysical Modeling: The results are likely to influence future theoretical models of planet formation. New or modified models need to account for gravitational instability under conditions similar to those around AB Aurigae. This highlights the environmental parameters—such as disk mass and temperature—that could foster such phenomena.
3. Future Observational Studies: The methodological framework and imaging techniques demonstrated in this paper will guide subsequent investigations into other protoplanetary systems. It also emphasizes the importance of multi-wavelength and long-term observational strategies to map the complete lifecycle of planet formation.

Speculation on Future Developments in AI

The application of advanced image processing and pattern recognition techniques, potentially enhanced by AI methodologies such as machine learning, can further revolutionize the detection and analysis of protoplanetary disks. AI could play a pivotal role in automating data reduction and feature extraction, enabling faster and more accurate identification of protoplanetary candidates. Additionally, AI-driven simulations could provide more robust models for predicting and visualizing planet formation scenarios.

Overall, this paper represents a significant contribution to the field of planetary science, providing critical observational data and reinforcing the necessity for diversified models to explain the varying pathways of planetary formation in the cosmos.