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Humankind is one step closer to making nuclear fusion – the very process that powers stars – a viable energy source.

ZYLSTRA: "I think this is a very exciting time. You know, people have been working on fusion for many decades, and this is literally decades in the making.”

U.S. government scientists have announced hitting a huge milestone called “a burning plasma,” which marks a step toward self-sustaining nuclear fusion energy.

Alex Zylstra is an experimental physicist at Lawrence Livermore National Laboratory.

"We are publishing findings that for the first time we've been able to create what we call a burning plasma in the laboratory. And burning plasma is one that's related to fusion energy research. And it's a system in which the fuel is mostly heating itself. In the past, we've always had to provide external heating to the fuel to get it hot. But now the fusion is actually doing most of the work for us."

Using the world’s largest laser, the researchers coaxed fusion fuel for the first time to heat itself beyond the heat they zapped into it.

The energy they produced was modest – about the equivalent of nine nine-volt batteries – but the experiments represent a big step in the decades-long quest.

The scientists cautioned that years of more work are needed.

“From there, the next step is actually we want to try to get to the point where the fuel is heating itself so fast that it can overcome mechanisms that reduce the temperature of the fuel. That would be what we would call ignition. Beyond there, we still need to show that we can produce more energy from fusion than we take to actually start the experiment.”

Unlike burning fossil fuels or the fission process of existing nuclear power plants, fusion offers the prospect of abundant energy without pollution.

Zylstra is encouraged by the progress.

“You know, there's many milestones that are being reported in the last few years. It's quite an exciting time for, for fusion. And I think it's also important to note that this particular milestone that we're reporting now is, is exciting because it's the first time that we're able to study how the fusion fuel behaves under these sorts of conditions, and that's key for building our understanding to guide the path forward."