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A pair of ‘super-puff planets’ lighter than a shaving foam or cotton candy have been discovered, researchers have told Metro.
TOI-791 b and TOI-791 c are exoplanets, planets outside our Solar System, 1,100 light-years away from Earth, or a 10billion-year-long drive away.
Yet despite them being the size of Jupiter, neither is a celestial heavyweight – they’re what are genuinely called ‘super-puff’ planets.
Jupiter has a density 28 times greater than TOI-791 c and 35 times greater than TOI-791 b, according to a paper published in the Monthly Notices of the Royal Astronomical Society.
No, they’re not made of pink candy floss, lead author Dr George Dransfield tells Metro. No, you can’t eat them, either.
‘They also have a similar density to shaving foam. At least shaving foam is white, not pink, and doesn’t taste nice,’ the astrophysicist at the University of Oxford says.
‘So people aren’t just thinking, “oh, tasty planets”.’
Dr Dransfield and her team used observations from the Antarctic Search for Transiting ExoPlanets telescope at Concordia Station in Antarctica.
She says being at the station is almost like being in an alien world. ‘There’s no life, there’s no microbes, there’s no birds, there’s no nothing, she says.
‘Nothing can live there because it’s so cold and so dry.’
Sadly, the same could be said for these otherworldly puffballs.
If Earth were as fluffy as TOI-791 b or TOI-791 c, the blue marble would be ‘devoid of all life’, says Dr Dransfield, even the more ‘exotic’ kind.
‘There would be no solid surface to speak of, and these planets are less dense than water, so they would float in almost any liquid.
‘I don’t know how you’d be able to get life going on these floating balls of gas.’
Fewer than 37 of the 6,300 exoplanets discovered so far are super-puffs, so we don’t know an awful lot about them.
‘Only four other systems contain multiple super-puffs in the same system,’ Dr Dransfield adds. ‘It’s a really rare configuration.’
TOI-791 b and TOI-791 c orbit a yellow-white dwarf, a star just a little brighter and hotter than our Sun.
This brightness is a big reason why Dr Dransfield and her team realised theexoplanets are so pillowy.
When an exoplanet passes in front of its host star, its atmosphere, if it has one, is backlit, a moment scientists call transit.
The gases in the planet’s atmosphere change the colour of the starlight that reaches telescopes, like the kind Dr Dransfield used in Antarctica.
By analysing changes in the light, which appear on screens as squiggly lines called wavelengths, scientists can guess the planet’s chemical makeup.
They also guessed the world’s densities by how their gravities tug at one another, affecting how long a transit takes.
In the case of TOI-791 b and TOI-791 c, researchers think their atmospheres may be filled with featherweight hydrogen and helium.
Planets form when all the gas and dust swirling around a young star clump together over millions of years, and gravity shapes them into a ball.
Gas giants are almost all atmosphere, though, being layers upon layers of gas swirling and wafting around a squished core.
TOI-791 b and TOI-791 c may have formed fairly far away from the fledgling star, where it’s colder.
‘Somehow these planets got away with not having a core 10 times the mass of Earth because there’s so much gas there,’ says Dr Dransfield. ‘They must have had a significantly smaller core.
‘One thing that we think might be happening is they’re forming in a region of the disc where there’s a lot more gas available than solids, so that they can start grabbing gas.’
TOI-791 b and TOI-791 c were identified in 2019 and 2023, respectively, by the Planet Hunters citizen scientist group using Nasa data.
Further investigation could help understand how super-puffs form.
After all, what makes them even quirkier is that they have a rare cosmic racecourse called a mean-motion resonance, for every five orbits completed by the inner planet, the outer completes roughly three.
Astronomers even found that their transits can last as long as 11 hours, which they were able to chart thanks to the darkness of Antarctica.
And that’s not even mentioning how ‘awkward’ their star is, adds Dr Dransfield.
When things are this rare and weird, scientists make goofy comparisons to make them easier to grasp. Hence why they’re called ‘candy floss’ planets.
‘Or cotton candy, if you’re American,’ Dr Dransfield says.
