A company aiming to make billions of dollars by cooling the planet has lifted the veil of secrecy that has kept it hidden from plans to prevent sunlight from overheating the planet.
It relies on aerosol particles that are 125 times smaller than the smallest grain of sand.
Stardust Solutions has raised $75 million since 2023 from investors betting that global warming will get out of control and governments may decide to pay Israeli and American startups to spray millions of tons of sunlight-reflecting aerosols into the stratosphere. The plan was so closely guarded that scientists had to sign non-disclosure agreements before researching technologies that could change the Earth.
The company revealed the composition of its proprietary particles on Thursday. They are made of something known as amorphous silica, are 0.5 microns in size, and can only be seen under a microscope. The startup also shared information about a system that can be used to disperse spherical silica particles about 11 miles above the ground and monitor them as they fall to Earth.
“Our initial premise was that the only way governments would consider solar reflective technology was if we provided a robust, science-based solution to all the challenges and concerns and demonstrated that it was safe, practical and controllable,” Stardust CEO Yanai Yedvav said in a statement. “That is the mission we have set for ourselves, and the details we are announcing today represent a major step toward that goal.”
The company is a leader in the study of solar geoengineering, a hypothetical approach to blocking the sun’s rays before they hit the Earth, altering clouds and other properties of the atmosphere. Other ideas envision building giant sunshades in space or creating foamy mixtures of reflective sea foam to limit the amount of heat the ocean absorbs.
Geoengineering is different from other climate change responses because, while it can theoretically reduce global warming, it does not address the root cause, the burning of fossil fuels. This means that until countries reduce their use of oil, gas and coal to safe levels and then remove excess climate pollution from the atmosphere and oceans, the world will effectively become addicted to solar geoengineering.
Stardust’s revelations came as President Donald Trump and Chinese President Xi Jinping held an unusual bilateral summit in Beijing after this year’s record heat and drought sparked historic wildfires in the United States and Southeast Asia. Analysts said climate change and geoengineering were not on the summit’s agenda, but Stardust will likely need the support or acquiescence of both countries to deploy its particles and repay investors.
“Given their size, they play an important role in everything,” said Erin Sikorsky, who served on the National Intelligence Council during the Obama administration, referring to the United States and China. She currently heads the Center for Climate and Security, a think tank. “You could stop someone from doing this if you wanted to. So that’s important for a company like Stardust.”
The company’s CEO Edvab said in an email that the timing of the announcement was “unrelated” to the U.S.-China summit.
Yanai Yedvav at the Stardust offices in Ness Ziona, Israel, on November 5, 2025. Politico’s Amit El-Kayam
New details about Stardust’s silica particles and other systems have been revealed in six academic papers posted online. Most of the papers were written with experts from top universities, but have not yet been peer-reviewed. This is an important step in the scientific publication process where other experts peer review and comment on the findings.
The company is currently seeking patents on particles and other technologies that are key elements of its business strategy. Stardust said it is also submitting papers to scientific journals.
Stardust has developed two types of amorphous silica-based particles. One of them is “completely biologically safe, currently manufacturable at scale, and in a very advanced stage of validation,” according to the study summary. Another version of similarly sized silica particles contains a core of calcium carbonate, which allows them to block solar radiation more effectively.
“Both designs are intentionally designed to be recycled into existing natural cycles after they hit the ground,” the brief states.
Amorphous silica has a different atomic structure than crystalline silica, which is a reactive and dangerous dust released by cutting or crushing certain types of rock. Stardust does not use crystalline silica in its manufacturing process. The World Health Organization’s cancer research agency says amorphous silica is not known to pose a risk to humans at low doses.
According to investor documents previously reported by POLITICO Magazine, Stardust had previously pitched to investors plans for a “global rollout” as early as 2035. At that point, the company’s expected revenue will be about $1.5 billion annually, Deck said. Stardust said its presentation from 2023 no longer reflects current thinking.
Some scientists remain wary of Stardust and other solar geoengineering companies. They worry that the technology could be misused at a time when international cooperation is fraying.
“This announcement is a clear example of why self-governance by for-profit organizations doesn’t work,” said Shuchi Talati, executive director of the Solar Geoengineering Integrity Council, a nonprofit organization that seeks to include marginalized countries and communities in the debate over solar-reflecting technology.
Stardust “cannot create its own principles and take credit for following them. It cannot define safety according to its own standards and self-certify that it meets them. We need coordinated, legitimate and independent research governance in this area,” she said.
The Talati Alliance works with the Natural Resources Defense Council, the American Geophysical Union, and other organizations to set standards for solar geoengineering research and development.
Hannah Safford, a former White House climate change policy adviser in the Biden administration, added: “When the people who develop globally important technologies are also responsible for managing them, things rarely go well.”
“In the United States, the government is more interested in banning climate science than in thoughtfully managing emerging technologies,” said Safford, who now works for the Federation of American Scientists think tank. “That leaves the door wide open for other countries, companies and individuals to take the lead, and we may not like their choices.”
