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.