presence of gas at densities high enough to be responsible for such structure. The debris disc surrounding HD 107146 was first discovered by its infrared (IR) excess using IRAS data [@Silverstone2000], but it was not until recently that the disc was resolved by the *Hubble Space Telescope* (HST) in scattered light, revealing a nearly face on disc with a surface brightness peak at 120 au and extending out to $\sim160$ au [@Ardila2004; @Ertel2011; @Schneider2014]. Despite HST’s high resolution, limitations in subtracting the stellar emission or a smooth distribution of small dust likely kept the double ring structure hidden. Using ALMA’s unprecedented sensitivity and resolution, [@Ricci2015] showed that this broad disc extended from about 30 to 150 au, but that it had a decrease in the dust density at intermediate radii, which could correspond to a gap produced by a planet of a few Earth masses clearing its orbit at 80 au through scattering. Finally, analysis of *Spitzer* spectroscopic and photometric data revealed the presence of an extra unresolved warm dust component in the system, at a temperature of $\sim$120 K and thus inferred to be located between 5-15 au from the star [@Morales2011; @Kennedy2014].

[max width=1.0]{}

  ------------------ ------------------------ ------------------ ------------- 