Imagine looking through a telescope and discovering a planet almost as large as Jupiter. Naturally, you would expect it to be enormous, heavy, and packed with gas.
Now imagine scientists telling you that this giant world is so surprisingly light that they compare its density to cotton candy.
That is exactly what astronomers have discovered. Two newly confirmed exoplanets, known as TOI-791 b and TOI-791 c, are among the lightest giant planets ever found. Although both are roughly the size of Jupiter, they are so incredibly fluffy that their average density is even lower than cotton candy, earning them a place among a rare group of worlds known as super-puff planets. The discovery is giving scientists a fascinating new opportunity to better understand how planets form and evolve throughout the universe.
What Are Cotton Candy Planets?
Before you start imagining astronauts bouncing across a giant pink dessert, the nickname has nothing to do with taste.
Scientists use the phrase "cotton candy planet" because of density rather than appearance. Density describes how much matter is packed into a certain amount of space. A bowling ball and a beach ball may look similar from a distance, but one contains far more material than the other.
The same idea applies here. TOI-791 b and TOI-791 c are almost as large as Jupiter, yet they contain only a small fraction of Jupiter's mass. Their enormous atmospheres spread that mass across such a large volume that the planets become astonishingly light for their size. In fact, Jupiter is around 28 to 35 times denser than these newly discovered worlds.
A Rare Discovery
Super-puff planets are already among the rarest types of planets known to science. Fewer than a few dozen have been confirmed despite astronomers discovering thousands of exoplanets beyond our Solar System.
Finding one super-puff planet would already be exciting. Finding two orbiting the same star is even more remarkable.
The sibling planets orbit a star called TOI-791, located about 1,110 light-years away in the constellation Volans. Their unusual characteristics make the system an exceptional natural laboratory for studying how giant planets grow, migrate, and hold onto their enormous atmospheres during the early stages of planetary formation.
How Did Astronomers Find Them?
The discovery began with NASA's Transiting Exoplanet Survey Satellite (TESS), a space telescope designed to search for planets orbiting distant stars. Rather than photographing planets directly, TESS watches for tiny dips in a star's brightness. When a planet passes in front of its star, it blocks a small amount of light, creating a repeating pattern that astronomers can measure.
After TESS identified the promising signals, researchers used additional telescopes and instruments to confirm that the objects were indeed planets. By combining several types of observations, scientists were able to estimate both the planets' sizes and masses, revealing just how extraordinarily light they are for worlds of such enormous dimensions.
Why Scientists Are So Excited
Every new planet teaches astronomers something about how our universe works. These two planets are especially valuable because they challenge existing ideas about how giant planets form and survive.
Normally, planets with such large atmospheres are expected to lose much of their gas over time as radiation from their stars gradually strips it away. Yet TOI-791 b and TOI-791 c have somehow managed to remain remarkably inflated. Understanding why may help scientists improve models of planetary evolution and better explain the incredible variety of worlds that exist beyond our Solar System.
The discovery also provides exciting targets for future observations. Powerful telescopes, including the James Webb Space Telescope, may eventually study the planets' atmospheres in greater detail, searching for clues about their chemical composition, temperatures, and formation history.
The Universe Keeps Surprising Us
Only a few decades ago, astronomers had not yet confirmed a single planet orbiting another Sun-like star. Today, scientists have identified thousands of exoplanets, revealing a universe filled with worlds far stranger than anyone once imagined.
Some planets rain molten iron. Others may have oceans beneath thick layers of ice. There are planets orbiting two stars, planets hotter than lava, and now, giant worlds so unexpectedly light that they have earned the nickname "cotton candy planets."
Each discovery reminds us that our own Solar System is only one chapter in a much larger cosmic story. The more astronomers observe the universe, the more they discover that nature often has a far greater imagination than we do.
Why This Matters
Not every scientific discovery changes our daily lives overnight. Some expand something equally valuable: our understanding of the universe.
Discoveries like TOI-791 b and TOI-791 c inspire new questions, encourage future generations of scientists, and remind us that there is still an extraordinary amount left to explore. Every new world we discover helps paint a richer picture of the universe we all share.
One More Good Thing Happened Today
Somewhere more than a thousand light-years away, two remarkably fluffy planets reminded humanity that the universe is still full of wonderful surprises waiting to be discovered.
Frequently Asked Questions
What is a cotton candy planet?
A cotton candy planet is an informal nickname for a rare type of exoplanet known as a super-puff planet. These worlds are nearly as large as Jupiter but contain much less mass, giving them an extremely low density.
Why are they called cotton candy planets?
The nickname refers to their density, not their appearance or composition. Like cotton candy, they are surprisingly light for their size because their thick atmospheres are spread across a very large volume.
Where are TOI-791 b and TOI-791 c?
The two planets orbit the star TOI-791, located approximately 1,110 light-years from Earth in the constellation Volans.
Could humans ever visit these planets?
Not with today's technology. At their current estimated distance, a journey would take far longer than a human lifetime. For now, astronomers study them using powerful space- and ground-based telescopes.
Do these planets have solid surfaces?
Scientists have not identified solid surfaces on either planet. Like Jupiter and Saturn, they are believed to be giant gas planets with deep, extended atmospheres.
Why should I care about planets so far away?
Every new planet expands our understanding of how the universe works. Studying distant worlds helps scientists improve theories about planetary formation, the evolution of solar systems, and the incredible diversity of planets that exist throughout our galaxy.
Did You Know?
- More than 6,000 exoplanets have now been confirmed beyond our Solar System.
- The first confirmed exoplanet orbiting a Sun-like star was announced only in 1995.
- Some exoplanets complete an orbit around their stars in just a few hours, while others take many years.
- Astronomers have discovered planets orbiting two stars, planets hotter than lava, and worlds where glass may fall as rain under extreme conditions.
- The James Webb Space Telescope is allowing scientists to study the atmospheres of distant exoplanets with unprecedented detail.
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