A long-standing joke in some scientific communities is that nuclear fusion energy is always 30 years away. 

But a number of private companies are saying that the atomic reaction that powers the sun, and produces zero carbon emissions, could be feasible on Earth in the next decade. 

Investors are starting to bet big on this timeline becoming a reality. 

Commonwealth Fusion Systems has raised a $1.8 billion Series B in a deal led by Tiger Global with participation from a long list of investors, including Bill Gates, Khosla Ventures and Soros Fund Management.

Last month, Helion Energy, another notable nuclear energy company, raised a $500 million Series E plus an additional $1.7 billion tied to performance-based milestones in a deal led by former Y Combinator president Sam Altman. Earlier this week, General Fusion, a Canadian startup backed by Jeff Bezos, closed a $130 million round. 

Chris Sacca's cleantech venture firm Lowercarbon Capital is currently hoping to raise a new fund focused on nuclear fusion, Axios reported. And funding is likely to only continue to flow into this area amid increased emphasis on combating climate change.

Featured image by Aitor Diago/Getty Images.

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