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Physics Black Holes Evolution Home A New Map of ‘Empty’ Space Challenges a Tranquil Picture of the Galaxy Comment Save Article Read Later Share Facebook Copied! Copy link Email Pocket Reddit Ycombinator Comment Comments Save Article Read Later Read Later astronomy A New Map of ‘Empty’ Space Challenges a Tranquil Picture of the Galaxy By Perri Thaler October 30, 2026
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In 2010, the Hubble Space Telescope released this image of a pillar of gas and dust in the Carina nebula that’s about 3 light-years — roughly 18 trillion miles — tall.
astronomy astrophysics cosmology galaxies physics All topics You might imagine space to be empty. But the seeming void contains a barely perceptible fog of hydrogen and other neutral atoms. In 2020, NASA’s New Horizons spacecraft, having passed the orbit of Pluto, measured a proxy for the amount of hydrogen around it. In the area between stars in our galaxy — the “interstellar medium,” or ISM — New Horizons found around 130 hydrogen atoms per liter of space.
This hydrogen, along with some helium and other molecules, is mostly left over from the Big Bang, and it’s constantly supplemented by infusions from cosmic phenomena such as stars ejecting jets of gas and dust as they are born and shedding their outer layers as they die.
Because the ISM is so diffuse and changes so slowly, astronomers have largely ignored its details for the last half-century, treating it as a stationary backdrop to the flashier happenings of the universe.
Over the past few years, astrophysicists have transformed our understanding of the interstellar medium. Using newly developed maps stretching thousands of light-years across our galaxy, they’ve discovered that it’s not the quiet, steady backdrop that researchers thought. Instead, much of the ISM appears to be unstable — a finding that directly contradicts the leading theoretical models taught in textbooks. The surprise finding could help resolve a long-unanswered question about how quickly stars form.
In 1969, the researchers George Field, Donald Goldsmith, and Harm Habing came up with a model of how the ISM behaves. They predicted that it exists in two stable states: cold and warm.