We come one of the great and terrible things about science. It’s a process, and over time, we often learn that the things we assumed, well, we all know what they say about assumptions.

Let’s take a moment to consider the fact that our galaxy, like all similar galaxies, has a supermassive black hole in its core. This black hole is smaller in volume than the planet-having parts of our solar system and packs in four million Suns’ worth of mass. As long as things are on stable orbits, there is no danger they’ll get sucked into that behemoth – we are in no danger, for instance – but instabilities happen. Sometimes a star gets too close to another star or two, and changed orbits can send things in to feed that black hole.

It had been believed (assumed) that our galaxy wasn’t actively feeding and consumed its last large meal about 2-4 million years ago. In newly analyzed images from the Hubble Space Telescope, it turns out – surprise, surprise – our supermassive black hole is way more active than thought and is currently having a good meal of whatever gas, dust, or stars most recently crossed its event horizon. When it eats, the infalling material generates a powerful magnetic field as it circles in, and researchers can see the jets that the magnetic field is creating. According to coauthor Alex Wagner: The streams percolate out of the Milky Way’s dense gas disk. The jet diverges from a pencil beam into tendrils, like that of an octopus.

These diverging jets are responsible for the soap bubble structure in the inner 500 light-years of our galaxy.

While today’s jet is relatively small and very hard to find, the event that occurred 2-4 million years ago was a million-fold brighter. This implies that just when life emerged on Earth, the constellation Sagittarius glowed with the light – largely blocked by dust – of a feeding black hole.

It kind of makes me hope it feeds again, just so we can watch from where we are, far far away.

More Information

Hubble press release

“Tracing the Milky Way’s Vestigial Nuclear Jet,” Gerald Cecil et al., 2021 December 6, The Astrophysical Journal