as dense as shaving foam fresh from a can
In the vast catalog of worlds beyond our sun, two planets have emerged that quietly upend our assumptions about what a planet can be — Jupiter-sized in girth yet lighter than spun sugar, orbiting a distant star in the southern constellation Volans some 1,110 light-years away. Discovered through NASA's Tess satellite and published by a team from the University of Oxford, these so-called super-puffs are the largest of their extraordinarily rare kind ever found, numbering among fewer than 40 in a census of nearly 6,300 known exoplanets. Their existence is a reminder that the universe holds configurations we have not yet learned to expect, and that each anomaly is an invitation to revise the story we tell about how worlds are made.
- Two Jupiter-sized planets with densities comparable to shaving foam have shattered expectations about the upper limits of planetary puffiness.
- Their near-impossible lightness — less dense than cotton candy despite their enormous size — creates urgent questions about planetary formation that current models struggle to answer.
- Detected by NASA's Tess satellite over the past decade, researchers used ground-based telescopes to confirm the planets' orbits and calculate the startling mass-to-volume ratios.
- The chemical makeup remains unconfirmed, leaving scientists uncertain whether clouds, hydrogen, or helium dominate these ghostly atmospheres.
- NASA's James Webb Space Telescope is positioned as the next instrument to weigh in, with follow-up observations expected to decode the planets' spectral fingerprints.
- With fewer than 40 super-puffs known among thousands of exoplanets, these two record-breakers are rare data points tightening the constraints on how gas-rich planetary systems evolve.
Two planets discovered in NASA's Tess satellite data have given astronomers something genuinely difficult to explain: worlds as large as Jupiter that weigh almost nothing. Their density, described by lead researcher George Dransfield of the University of Oxford, is roughly that of shaving foam fresh from a can — making Jupiter, by comparison, 35 times denser for the same volume. The findings were published Wednesday in Monthly Notices of the Royal Astronomical Society.
The planets orbit a star in the southern constellation Volans, named for the flying fish, approximately 1,110 light-years from Earth. Tess detected them by watching for the faint dimming of starlight as each planet crossed in front of its host star. Ground-based telescopes then measured orbital periods and the star's gravitational wobble, allowing the team to calculate mass, size, and ultimately density — numbers that came back nearly unbelievable.
What these planets are made of is still an open question. Dransfield suspects vast envelopes of hydrogen and helium accumulated around rocky cores during the planets' formation in gas-rich protoplanetary disks, before the surrounding material dissipated. Their color is likely white or blue depending on cloud cover — the cotton-candy pink of popular imagination, it turns out, is more poetry than science. Confirmation of their chemical composition awaits observations by NASA's James Webb Space Telescope, which will parse the planets' light into a spectrum revealing the atoms and molecules present.
Super-puffs are vanishingly rare: fewer than 40 exist among nearly 6,300 confirmed exoplanets. Finding the two largest ever recorded adds a meaningful constraint to planetary formation models and deepens the broader question of what variety is truly possible across a cosmos far stranger than our solar system alone would suggest.
Two planets have turned up in the data from NASA's Tess satellite that challenge what astronomers thought they knew about how massive worlds could be built. They are as large as Jupiter, the giant that dominates our own solar system. But they weigh almost nothing—so little that if you could somehow place them on a scale next to a cloud of spun sugar, the planets would lose. They are, in the language of astronomy, super-puffs, and these are the biggest ones ever found.
The discovery came from a team led by George Dransfield at the University of Oxford, who published the findings Wednesday in Monthly Notices of the Royal Astronomical Society. The two planets orbit a star called Volans, named for the flying fish, in the southern sky roughly 1,110 light-years from Earth—a distance so vast that light itself takes more than a millennium to cross it. What makes these worlds so strange is their density. Dransfield described it in an email with a comparison that sticks: they are about as dense as shaving foam fresh from a can. Jupiter, by contrast, is roughly 35 times heavier for the same volume.
The planets were detected over the past decade by Tess, which scans the sky for the tiny dips in starlight that occur when a world passes in front of its host star. Once the researchers knew the planets were there, they used ground-based telescopes to measure how long each orbit took and how much the star wobbled under the gravitational tug of its companions. From those measurements, they calculated mass and size, and therefore density. The numbers came back almost unbelievable: these Jupiter-sized bodies are lighter than cotton candy.
What they are made of remains uncertain. Dransfield suspects they are mostly hydrogen and helium, the lightest elements, wrapped in an atmosphere so thick and wispy that it dominates the planet's volume. The color is probably white or blue, she said, depending on whether clouds veil the surface. The romantic notion of cotton-candy pink worlds, it turns out, is just marketing. But the composition will not be confirmed until NASA's James Webb Space Telescope can observe them in detail, breaking down their light into a spectrum that reveals what atoms and molecules are present.
Super-puffs are thought to form in the swirling disk of gas and dust that surrounds a newborn star, in regions where gas vastly outnumbers solid material. In such an environment, a rocky core can accumulate an enormous envelope of hydrogen and helium before the disk dissipates. Over time, the planets lose some of this material, but these two have held onto enough to remain extraordinarily puffy. They are rare. Of the nearly 6,300 exoplanets confirmed so far, fewer than 40 are super-puffs. Finding the largest ones yet is a piece of a much larger puzzle: understanding how planets form, why they take the shapes they do, and what variety is possible in a universe far larger than we can easily imagine. Each discovery like this one adds another constraint to the models, another data point that says: this is how the cosmos actually works.
Citações Notáveis
These two planets have densities comparable to a nice blob of shaving foam, fresh from the can.— George Dransfield, University of Oxford
By studying exotic systems containing rare planet types, we add further pieces to the puzzle of planet formation and learn more about our place in the cosmos.— George Dransfield
A Conversa do Hearth Outra perspectiva sobre a história
When you say these planets are lighter than cotton candy, are you speaking literally—that if you weighed them, they'd come out lighter?
Not quite. They're the same size as Jupiter, so the total mass is still enormous. What's remarkable is the density—how much mass is packed into that volume. A sugar cloud is mostly air. So are these planets. They're mostly empty space filled with gas.
How do you measure the density of something 1,110 light-years away?
You can't put it on a scale. Instead, you watch how the planet moves around its star. The star wobbles slightly under the planet's gravity. You measure that wobble, calculate the planet's mass, and you already know its size from how much starlight it blocks. Divide mass by volume, and you have density.
Why would a planet form so puffy in the first place?
Around a young star, there's a disk of gas and dust. If there's much more gas than dust, a rocky core can grab an enormous atmosphere of hydrogen and helium before the disk blows away. These planets held onto that atmosphere. Others shed it and became denser.
Are these planets habitable?
Almost certainly not. They're gas giants with no solid surface. But that's not really the point. The point is that they exist at all—they show us that nature can build planets in ways we didn't fully expect.
What happens next?
The Webb telescope will look at them more closely, break down their light to see what elements are actually there. That will either confirm the hydrogen-helium theory or surprise us with something else. Either way, we learn more about how planets come to be.