G1.9+0.3 is a radio source (RS, its identifier "G1.9+0.3" consists of its
galactic coordinates) that is a supernova remnant of a supernova (SN)
presumed to have occurred in the decades circa 1900,
and is the youngest Milky-Way SN remnant known.
The SN was not observed, apparently due to cosmic dust obscuration.
The remnant's age is estimated by the observed expansion of its
angular diameter since the RS's discovery.
The RS was discovered and considered a SN remnant candidate in 1984,
and further observation in 2008 confirmed the theory.
The SN is thought to have been a Type Ia supernova.