# Leaning Sideways: VHS 1256-1257 b is a Super-Jupiter with a Uranus-like Obliquity

**Authors:** Michael Poon, Marta L. Bryan, Hanno Rein, Caroline V. Morley, Gregory Mace, Yifan Zhou, Brendan P. Bowler  
**arXiv:** [2410.02672](https://arxiv.org/abs/2410.02672)  
**Date:** 2024-10-03  
**Summary page:** https://www.summarizepaper.com/en/paper/2410.02672v1/

## Key points

- Study focused on angular momentum architecture of VHS J125601.92-125723.9, a hierarchical triple system
- System consists of low-mass binary and planetary-mass companion VHS 1256 b
- System estimated to be around 140 million years old with substellar photometric variability and unique characteristics
- Research aimed to determine obliquity of VHS 1256 b, found it has large planetary obliquity
- All three measured angular momentum vectors for the system are misaligned
- Origin of tilt similarities with Uranus distinct, suggested top-down formation via core/filament fragmentation as potential explanation
- Findings accepted for publication in The Astronomical Journal

## Summary

A recent study by Michael Poon et al. delved into the angular momentum architecture of VHS J125601.92-125723.9, a hierarchical triple system consisting of a low-mass binary and the widely-separated planetary-mass companion VHS 1256 b. This intriguing system, estimated to be around 140 million years old, has garnered significant attention due to its high level of substellar photometric variability and unique characteristics such as silicate clouds and disequilibrium chemistry. The focus of this research was on determining the obliquity of VHS 1256 b, i.e., the tilt of its spin axis relative to its orbit. Through multiple measurements, including a projected rotation rate obtained from near-IR high-resolution spectra and a published photometric rotation period, it was determined that the companion is viewed edge-on with a line-of-sight spin axis inclination. Additionally, astrometry measurements were refitted to confirm an orbital inclination, leading to the conclusion that VHS 1256 b possesses a large planetary obliquity. The study also revealed that all three measured angular momentum vectors for the system are misaligned with respect to each other. Despite sharing similarities in terms of tilt with Uranus, their origins are distinct. The researchers ruled out planet-like scenarios such as collisions and spin-orbit resonances and instead suggested top-down formation via core/filament fragmentation as a potential explanation for the unique characteristics observed in this system. This comprehensive analysis not only adds valuable information to our understanding of this super-Jupiter on a Tatooine-like orbit but also sheds light on the complex dynamics at play within this intriguing hierarchical triple system. The findings, accepted for publication in The Astronomical Journal, provide important contributions to ongoing research in exoplanetary science.