Astronomers believe that a supernova remnant near the centre of the Milky Way is about 140 years old. This would make it the youngest supernova in the galaxy.

The ring-like supernova remnant, called G1.9+0.3, was first identified in the early 1980s. Recent observations by NASA’s Chandra X-Ray Observatory and the Very Large Array in New Mexico show that the glowing gas shell’s diameter has expanded by 16 per cent over the past 22 years.

Assuming that the speed of expansion is roughly constant, this would make the remnant, which is about 28,000 light years away, about 140 years old.  Before this, the youngest supernova was believed to have been the source of the remnant Cassiopeia A. That supernova occurred around the year 1680.

G1.9+0.3 would not have been visible to astronomers in the 19^th century because the best telescopes at the time would not have been able to detect it amidst the dense gas and dust near the galactic centre, according to Stephen Reynolds of North Carolina State University in Raleigh.

Measurements of supernova rates in other galaxies suggest that the Milky Way should have about three supernovae every century. This means that our galaxy should have about 10 remnants younger than Cassiopeia A.

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