Why Do We Love Pluto So Much?

Humans seem to have a special affection for the dwarf planet.

Jul 15 2015, 10:00am

Image: Stuart Rankin/Flickr

As NASA's New Horizons spacecraft made its closest approach to Pluto this week, astronomers at NASA and beyond rejoiced. But it wasn't just space geeks celebrating: people around the world were tuning in, tweeting, and talking about this historic moment.

Although it was an important milestone, this mission seems to have attracted a particularly high amount of public interest compared to some other recent space launches. There's plenty of evidence that Pluto is one of the most beloved objects orbiting our Sun. There are societies dedicated to re-promoting it to planet classification, dozens of T-shirts and posters featuring the dwarf planet, and even songs written about it. So what is it about this distant, frozen body that makes us feel so warm and fuzzy?

"Even before the whole planet/dwarf planet thing, Pluto was always seen as the underdog," said Joel Parker, a NASA research astronomer and member of the science team for New Horizons. "You have all these big gas planets out there and then you have this little dinky thing. Little Pluto was just out on the edge and it was almost like someone who had gotten left behind. That engenders some kind of empathy for Pluto."

Indeed the language and imagery we use for Pluto in pop culture signifies a kind of pity for a planet so different from our own, all little and cold and ostracized from the rest of the planet family. Humans have a tendency to anthropomorphize inanimate objects, and it seems like Pluto has fallen subject to this habit. But why don't we feel in awe of mighty Jupiter or dazzled by cerulean Neptune in the same way we adore Pluto?

The declassification from planet to dwarf planet may have something to do with it. When Pluto was first discovered, it seemed appropriate to classify it as a planet because it was so hard to detect its size and mass. The best estimations astronomers could come up with was that it was about the size of Mars. It wasn't until 1978, when Pluto's moon Charon was discovered, that a more accurate view of Pluto's size came into focus. With a diameter of less than 1,500 miles and a mass 1/400th of Earth's, astronomers even then weren't totally convinced we had a ninth planet.

But by the late 90s and early 2000s, we began to learn more about the Kuiper belt—the region beyond the planets that's home to hundreds of small objects like asteroids—and its objects beyond Pluto, making it more and more clear that it didn't really fit in with the rest of the planets in our system. Pluto kept its planetary status until 2006, when the International Astronomical Union voted at its annual general assembly to create a new classification for celestial bodies: the dwarf planet, which included Pluto.

This caused a lot of controversy both within the world of astronomy and in the public at large. People signed petitions to reclassify Pluto as a planet. They protested. Years later, they still talk about it. There seemed to be a real attachment to our littlest planet. For decades, Pluto was understood as the ninth, smallest, and furthest planet in our solar system and the reclassification rattled many people.

"We all grew up with the idea that the solar system had nine planets. It was one of those givens," Robert Cockcroft, an astronomer at McMaster University, told me over the phone. "When astronomers decided to change that, there was a lot of emotion behind that decision."

Cockcroft said there are other good reasons why people might be particularly enchanted with this mission over others. Aside from the deep scientific merit, the public at large is getting to witness an historic event that marks a milestone in humanity's exploration of our solar system. When New Horizons was launched, Pluto was still a planet and it was the only one we had yet to explore. It was the last planet to check off the list and we're finally doing that, even if Pluto isn't technically a planet any more.

"For people of my generation, we are not old enough to have seen the first missions to the other planets: Jupiter, Saturn, Uranus, and Neptune that were sent out in the 1970s," Cockcroft said. "This mission to Pluto is our first and last chance to see in real time a mission going up close and personal to one of the major bodies in the solar system. It's just incredible to see."

Beyond its declassification, Pluto has long held some sentimental attachment for astronomers and space geeks alike, according to Simon Porter, a postdoctoral researcher on the New Horizons team. Though there are now multiple bodies similar to Pluto that have been identified in the Kuiper belt, for so long that wasn't the case. It was discovered by Clyde Tombaugh in the 1930s using mechanical technology, named by an 11-year-old girl, and marked the furthest reaches we could even dream of exploring in our own solar system. This connection to Pluto's history has lingered through generations, even as a clearer picture of our solar system beyond Pluto emerged. When New Horizons was launched in 2006, some of Tombaugh's ashes were placed on board.

"It was this point of light out in the very far distance," Porter explained. "For a long time, it was the only thing that we knew was out there and so it has this very special status in a lot of people's hearts."