The Milky Way’s most recent supernova was hidden… until now!
“Close to the galactic center, the supernova remnant G1.9+0.3 was first discovered in the radio thanks to the Very Large Array (VLA), with its origin unknown. The fact that it was so small on the sky, despite being at a distance of 25,000 light years, brought up the possibility that this was a very young supernova: perhaps the youngest of all supernovae in the Milky Way. Follow-up observations took place in the 2000s with the Two-Micron All-Sky Survey in the infrared and with the Chandra X-ray observatory, where a wonderful surprise came to light: this supernova remnant was expanding at an incredible pace!
In 1604, Kepler’s supernova went off, the last Milky Way supernova visible to naked-eye skywatchers here on Earth. Yet since the development of radio and X-ray astronomy, other, more recent supernova remnants in our galaxy have been found. They’ve only been invisible to the naked eye because of the galactic gas and dust that blocks their visible light. In 1984/5, the VLA discovered the most recent known remnant near the galactic center, and follow-up observations showed a rapid expansion. The most recent data not only dates this remnant to be only 110 years old, but it teaches us that it’s a Type Ia supernova that formed from the merger of two white dwarfs. The standard model — of one white dwarf accruing matter from a binary companion — may not only be a minority of Type Ia events, perhaps it doesn’t occur at all.