What emits the least radiation when hot? What element with a high vapor point the emits to least light or radiation when heated to its vapor pressure point in a vacuum?  

Ideally I would like to know in 0 gravity and 0 pressure which elements can be get the hottest around the sun before the vapor pressure point is reached and/or emit the least black body radiation when hot. 

https://space.stackexchange.com/questions/35486/shielding-capability-of-liquid-metals
Technically, a smooth or molten, unoxidized metal surface (regardless of chemistry) makes a good candidate.  This thesis from Auburn University reports the emissivities of both oxidized and unoxidized metals at temperatures typically encountered in industrial processes; note the low values for all the unoxidized metals studied in the IR range where most radiation is given off.