These Exoplanets Are As Fluffy As Cotton Candy!


An illustration depicting the Sun-like star Kepler 51 and three giant Jupiter-sized planets, discovered by NASA's Kepler Space Telescope discovered in 2012-2014 (Credit: NASA, ESA, and L. Hustak, J. Olmsted, D. Player and F. Summers (STScI))

Cotton candy is probably the last thing that comes to mind when one thinks of exoplanets. But the three giant worlds orbiting the Kepler 51 star system, about 2,600 light-years away from Earth, are so "light and fluffy" that they warrant a comparison to the beloved spun-sugar confection.

The exoplanets named Kepler 51 - b, c, and d, detected by NASA's Kepler Space Telescope between 2012 and 2014, belong to a rare class of low-density "super-puffs" — only 15 of which are known to exist. Curious about the composition of the exoplanets’ atmospheres and to find clues around how these lightweight worlds may have formed, a team led by the University of Colorado (CU), graduate student, Jessica Libby-Roberts, decided to investigate.

The scientists began by using the Hubble Space Telescope to zoom in on the 500-million-year-old Kepler 51-star system, which hosts the planets. The data enabled the team to develop accurate estimates for the three planets' masses and densities. The researchers' calculations revealed the three "super-puffs" had a density of less than 0.1 g/cm³ of volume — almost identical to that of the sweet pink carnival treat. In contrast, the similar-sized Jupiter boasts a density of 1.33 g/cm³. “We knew they were low density,” said Libby-Roberts. “But when you picture a Jupiter-sized ball of cotton candy—that’s really low density.”

While confirming the planets' "super puff" status was easy, using the Hubble to peer into their atmosphere proved impossible due to a high-altitude opaque shell around each of their outer layers. “This was completely unexpected. We had planned on observing large water absorption features, but they just weren’t there. We were clouded out,” Libby-Roberts said.

Artist's illustration comparing the size of the "super-puff" Kepler-51 planets to some of the planets in our Solar System (Credit: NASA / ESA / L. Hustak & J. Olmsted, STScI.)

Computer simulations and other tools led the researchers to theorize that the Kepler-51 planets most likely comprise lightweight gases like hydrogen and helium, which also explains their puffiness. They suspect that similar to Saturn's moon Titan, the worlds are encompassed by a layer of methane. “If you hit methane with ultraviolet light, it will form a haze,” Libby-Roberts said. “It’s Titan in a nutshell.”

Libby-Roberts and study co-author, CU assistant professor Zachory Berta-Thompson, maintain that the "super-puff" worlds may not be as unusual as was first thought. Their observations showed the trio were shedding as much as tens of billions of tons of gas into space every second. The researchers say if the pace continues, the planets will lose their cotton-candy puffiness within the next billion years and end up looking more like the normal class of exoplanets called “mini-Neptunes.”

“People have been really struggling to find out why this system looks so different than every other system,” Libby-Roberts said. “We’re trying to show that, actually, it does look like some of these other systems.” Berta-Thompson agreed: “A good bit of their weirdness is coming from the fact that we’re seeing them at a time in their development where we’ve rarely gotten the chance to observe planets.”

Only time will tell if the scientists are right. For now, it is just fun to imagine three ginormous balls of cotton candy floating around in our universe.


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  • carebear0518
    carebear0518Wednesday, March 18, 2020 at 12:20 pm
    Ok I going to space but how will I eat it 🍭🍭
    • seventeenkpop
      seventeenkpopSunday, March 15, 2020 at 4:19 pm
      Hey guys it's not actually cotton candy it's just a planet that is fluffy like cotton candy.
      • blueclaw
        blueclawMonday, May 25, 2020 at 12:36 pm
        • moonlight35
          moonlight35Friday, May 15, 2020 at 2:47 am
          we know its just fun to talk about XD
          • 7seventwice7
            7seventwice7Wednesday, April 1, 2020 at 8:27 am
            idc its still fun
            • superemogamer
              superemogamerTuesday, March 17, 2020 at 3:21 pm
              But can I pretend it's cotton candy?!
            • lamas
              lamasThursday, March 12, 2020 at 7:28 am
              • devanf
                devanfWednesday, March 11, 2020 at 1:17 pm
                Weird.Flying Cotton Candy in space.
                • blueclaw
                  blueclawMonday, May 25, 2020 at 12:35 pm
                  YOU MEAN YUMMY!😋‼❕❕
                • cobrakid
                  cobrakidTuesday, March 3, 2020 at 4:39 pm
                  • daniela43347
                    daniela43347Tuesday, March 3, 2020 at 10:08 am
                    can i eat the planet and if i can can i go to space grab a peice of the planet go back to planet earht and eat it. like if you like this idea and reply if you have some diffrent ideas
                    • moonlight35
                      moonlight35Friday, May 15, 2020 at 2:48 am
                      I LOVE THAT IDEA!!
                      • jmhedgehogsrule
                        jmhedgehogsruleSunday, May 10, 2020 at 10:06 am
                        Good luck!
                        • superemogamer
                          superemogamerTuesday, March 17, 2020 at 3:20 pm
                          Maybe you can build a shrink ray, go into space, shrink the exoplanets, bring them back to Earth, and then just put the whole thing in your mouth. Or you can just use them as pillows!
                        • cobrakid
                          cobrakidWednesday, March 4, 2020 at 4:01 pm
                          I would eat it in front of my friends, devouring every bite
                          • superemogamer
                            superemogamerTuesday, March 17, 2020 at 3:22 pm
                            LOL. They would get so jealous XD!
                            • jmhedgehogsrule
                              jmhedgehogsruleSunday, May 10, 2020 at 11:05 am
                              I would steal a bite honestly
                          • cobrakid
                            cobrakidWednesday, March 4, 2020 at 3:13 pm
                            I would eat it in front of my friends
                          • odd1sout
                            odd1soutThursday, February 20, 2020 at 10:13 am
                            whoa thats cool I wounder if there are more of them.
                            • angie_yoqueen20
                              angie_yoqueen20Wednesday, February 12, 2020 at 8:20 am
                              this is so cool😁😃
                              • qwerty9
                                qwerty9Tuesday, February 11, 2020 at 8:27 am
                                now i'm hungry for cotton candy😂😢
                                • 7seventwice7
                                  7seventwice7Tuesday, February 11, 2020 at 7:14 am
                                  i want to eat it