Gagan Deep Anand

Yeah, so galaxies form inside dark matter, a halo.

So the dark matter is the prevailing structure, actually, even though we can't see it.

And then all of the matter that makes up, you know, the things we know, like stars and planets, normal matter or baryonic matter, that is, you know, that's the stuff that we know and love and that you see in the pictures.

But...

The prevailing model of our universe, what's called Lambda CDM, or the model that describes dark energy and dark matter, it predicts that you should have dark matter halos that are actually not massive enough to form stars in the centers.

And so this has been a prediction of the theory, and with the discovery of this relic object, Cloud 9, it's a confirmation that you actually do indeed have dark matter halos that are not massive enough to form stars, just like the simulations predict.

Yeah, so before, you know, if you go back way in time before galaxies formed, you have the universe and you have certain parts of the universe that are just slightly more dense than other parts.

And those are the regions that become galaxies.

And so we think that galaxies form in halos or roughly spherical regions of dark matter.

And so these halos trap gas, and that gas collapses and then forms galaxies.

But our models predict that you have to have a halo that is above a critical mass to actually collapse and form a galaxy.

And so, as Andy was saying earlier, you also have...

But you should also have dark matter halos that are just below this critical mass threshold that remain starless, basically.

Adding on to what Andy was saying earlier, too, relics live in this sweet spot where they're not massive enough to collapse and form galaxies.

but they are just massive enough to hold on to some of the gas still.

And that's the key part, is that since they're able to hold on to the neutral hydrogen gas, we can actually go with radio telescopes and look for the glow of that neutral hydrogen, and we see it in the radio observations.

And that's how the Chinese team that detected Cloud 9 in the first place, that's how they were able to find it.

Yeah, so first of all, it's a big win for the theory.

It's a big prediction of the model that these objects should exist.

And just by finding one, you know you're on the right track.