Multiple Gaps in the Disk of the Class I Protostar GY 91

TL;DR

This study uses high-resolution ALMA observations to reveal multiple gaps in the disk of the Class I protostar GY 91, suggesting early formation of Saturn-mass planets within 0.5 million years.

Contribution

First high-resolution imaging of GY 91's disk showing multiple gaps, indicating early planet formation comparable to HL Tau.

Findings

GY 91 disk has three dark lanes at 10, 40, and 70 AU.

Gaps are consistent with Saturn-mass planets.

GY 91 and HL Tau are of similar ages, GY 91 possibly younger.

Abstract

We present the highest spatial resolution ALMA observations to date of the Class I protostar GY 91 in the $\rho$ Ophiuchus L1688 molecular cloud complex. Our 870 $\mu$m and 3 mm dust continuum maps show that the GY 91 disk has a radius of $\sim$80 AU, and an inclination of $\sim$40$^{\circ}$, but most interestingly that the disk has three dark lanes located at 10 AU, 40 AU, and 70 AU. We model these features assuming they are gaps in the disk surface density profile and find that their widths are 7 AU, 30 AU, and 10 AU. These gaps bear a striking resemblance to the gaps seen in the HL Tau disk, suggesting that there may be Saturn-mass planets hiding in the disk. To constrain the relative ages of GY 91 and HL Tau, we also model the disk and envelope of HL Tau and find that they are of similar ages, although GY 91 may be younger. Although snow lines and magnetic dead zones can also produce dark lanes, if planets are indeed carving these gaps then Saturn-mass planets must form within the first $\sim$0.5 Myr of the lifetime of protoplanetary disks.