Dark Matter Stars May Have Seeded Supermassive Black Holes

We're getting very theoretical here, considering we're not even sure what dark matter is. Anyway, in the early universe, when all the matter was squished together a lot more tightly than it is today, stars that formed were often a little different. Oh sure, they were made of hydrogen, but they also contained a bit of dark matter in the form of Weakly Interacting Massive Particles.

These dark matter stars would have looked a lot different than the stars we know today. For one, they were gigantic, spanning up to 10 AU across. They could be millions of times heavier than the sun, and billions of times as bright.

The existence of these stars could solve a big mystery of the early universe. Galaxies seemed to form around supermassive black holes, but where did these black holes come from. A gigantic star would collapse into a gigantic black hole. It's almost a little too obvious.

Are Dark Matter and Dark Energy Actually the Same Thing?

We're getting into some very high-minded science here today. One of the thorniest issues with astrophysics today is dark matter and dark energy. We know they exist, but we have no idea what they are and they seem to make very little sense. Scientists have tried combining the two in models previously, but that involves modifying general relativity, which is a pretty bedrock theory. Modifying it hasn't gone well.

But now, there's a new idea out there, something that combines two things that sound ridiculous but are actually completely compatible with general relativity: negative masses and matter creation. Essentially, this new theory posits that dark matter and dark energy are some sort of exotic fluid that possesses negative mass and also continuously creates new negative mass. Negative mass, if you don't know, is mass, but negative. If you tried to throw a baseball made of negative mass, it would accelerate toward you instead of away. It's weird and completely hypothetical at this point. It was also thrown out as a candidate for dark matter/energy because it would get thinner and less repulsive as the universe expanded, and that's not the result we're seeing. That's where matter creation comes in. If this negative matter constantly creates more negative matter, the density won't thin out and the expansion of the universe works out.

Frankly, this is some EXTREMELY hypothetical stuff, with not a hint of proof behind it. However, it works perfectly within our current laws of physics, and it perfectly predicts the observations we see of dark matter halos. It fits the observations we have, now all we have to do is observe it. No problem, right?

Apparently We're Looking For Dark Photons Now

I am not a theoretical physicist. Shocking, right? But I like to think I have a greater knowledge and appreciation for the subject than the average person. I've read some books, I occasionally peruse science news websites. But I had never heard of dark photons until today. Sure, they're still theoretical, but the fact that we're confident enough in their existence to actually spend money searching for them... I'm skeptical.

But anyway, yes, we're searching for dark photons. And we're doing it by shooting antimatter at a diamond. Science is weird, but it's also pretty cool. 

I guess the better question is why are we looking for something called a dark photon anyway? Well, if you follow astrophysics at all, you'll know that most of the universe is not actually visible. The matter we see? Only about 10% of the universe's mass. The rest is so-called dark matter/energy. And you'll also know that we've had absolutely no luck in figuring out what either of those things actually are. If dark photons are a thing, and that's a big if, they could help us detect dark matter and help us figure out what it is. In addition, the existence of dark photons would mean the existence of a fifth fundamental force beyond gravity, electromagnetism, and the weak and strong nuclear forces. That's right, the fifth fundamental force would be... dark electromagnetism. 

I don't want to downplay the work these people are doing, and obviously, if they're successful, that would be really cool and would change our viewpoint of the universe, but these names are terrible.

The Universe's First Stars Have Been Discovered

These are some pretty old stars we're talking about here. Previously, the oldest stars we knew about formed 400 million years after the Big Bang, but it was suspected that stars formed much earlier than that. We just couldn't see them yet. Well, now we have. And they did form much earlier, coming into existence a mere 180 million years after the Big Bang.

Credit: N.R. Fuller, National Science Foundation

Finding these old stars took some doing. Until 500 million years post-Big Bang, the universe was filled with loose, heated hydrogen, which is very good at blocking light. So instead of looking for the stars themselves, astronomers have to look for their impact on the cosmic background radiation. This is no easy task, the radio signals astronomers were searching for were something like 10,000 times dimmer than normal radio noise. But you know what? They did it.

Besides that, there's something interesting going on with the signals. They're twice as bright as expected, meaning the radio background was stronger than expected, or the hydrogen filling the young universe was cooler. The second option is more likely, but what would be cooling down the hydrogen is a mystery. A likely contender is dark matter. If that's the case, this discovery may accidently have given us our best look at what dark matter actually is. And that's news worth mentioning.