Read more: 鈥�Mysteries of the Milky Way鈥�
We can see the fiery brilliance of supernovae from more than halfway across the universe, billions of light years away. So why are we missing them in our own backyard? Comparison with similar spiral galaxies suggests that the Milky Way should host about three stellar explosions per century, but in the past millennium and a bit we have seen only five or six.
All of these have been within about 15,000 light years of us, while the Milky Way鈥檚 disc is 100,000 light years across. We are missing the more distant explosions for a simple reason: our lowly viewpoint means most of the galactic disc is hidden behind interstellar dust.
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As the blast wave of a supernova ploughs out into space, it energises particles to emit radio waves, which are not absorbed by intervening dust. Radio astronomers are now finding evidence of many of these supernova remnants. In 2008, one near the centre of our galaxy, called G1.9+0.3, was calculated to be the youngest known. Its light probably reached Earth about 110 years ago 鈥� perhaps marking Queen Victoria鈥檚 funeral, had it not been for the black veils of dust in between.
There is still a dearth of remnants from the past 2000 years, but these explosions occur in complex regions of star formation where ionised gas clouds are also emitting radio waves, confusing the picture. 鈥淚 think they鈥檙e out there,鈥� says of the University of Cambridge, who discovered G1.9+0.3 in the 1970s. 鈥淲e have just not found them yet.鈥�