In our last episode, we brought you tales of a vampiric star and its thrall… or rather its companion star. In this episode, we are keeping with the Halloween season theme and exploring the hidden places where stars go when they die.

No seriously, this is a real scientific problem.

Astronomers haven’t had a good understanding of where the remnants of large stars end up. Put simply – there are a whole lot of missing black holes and neutron stars that were kicked out of supernovae.

But what’s missing can sometimes be found. In a new paper in the Monthly Notices of the Royal Astronomical Society, researchers led by David Sweeney use detailed galactic models to discover where neutron stars and black holes live out eternity.

This model had to take into account many different factors, but the largest challenge of all was sorting out what happens during the supernovae explosions.

It turns out many to perhaps all of these explosions are asymmetric. While a glowing nebula – a supernova remnant – marks the original star’s location, any stellar remnant is cast out in a random direction. And they’re flying fast. This team estimates that 30% of the stellar remnants are flung away with sufficient energy to leave our galaxy.

The objects that don’t escape are generally kicked into highly-elliptical orbits that stray in and out of the main disk of the Milky Way. The team refers to this family of orbits as the ‘galactic underworld’.

We are used to seeing only our galaxy’s living stars along with its expansive flat disc and bulging spheroid in the center. The expected distribution of dead stars is very different. It is basically a giant blob with just a hint of a disk. And this blobby result should be testable. Sweeney explains: The most exciting part of this research is still ahead of us. Now that we know where to look, we’re developing technologies to go hunting for them. I’m betting that the ‘galactic underworld’ won’t stay shrouded in mystery for very much longer.

We wish this team well in their discoveries, but we would remind them dead men tell no tales, and we’re not entirely sure we want to know what yarns dead stars may try to weave.

More Information

The University of Sydney press release

“The Galactic underworld: the spatial distribution of compact remnants,” David Sweeney, Peter Tuthill, Sanjib Sharma, and Ryosuke Hirai, 2022 August 25, Monthly Notices of the Royal Astronomical Society