Debris disks are extrasolar analogs to our own Kuiper Belt and they are detected around at least 17 % of nearby Sun-like stars .
The morphology and dynamics of a disk encode information about its history , as well as that of any exoplanets within the system .
We used ALMA to obtain 1.3 mm observations of the debris disk around the nearby F5V star HD 170773 .
We image the face-on ring and determine its fundamental parameters by forward-modeling the interferometric visibilities through a Markov Chain Monte Carlo approach .
Using a symmetric Gaussian surface density profile , we find a 71 \pm 4 au wide belt with a radius of 193 ^ { +2 } _ { -3 } au , a relatively large radius compared to most other millimeter-resolved belts around late A / early F type stars .
This makes HD 170773 part of a group of four disks around A and F stars with radii larger than expected from the recently reported planetesimal belt radius - stellar luminosity relation .
Two of these systems are known to host directly imaged giant planets , which may point to a connection between large belts and the presence of long-period giant planets .
We also set upper limits on the presence of CO and CN gas in the system , which imply that the exocomets that constitute this belt have CO and HCN ice mass fractions of < 77 % and < 3 % , respectively , consistent with Solar System comets and other exocometary belts .