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Yes, he did it.

Astronomer Mike Brown admits that he took aim at a faraway rock that was minding its own business until he came along. The title of his new book tells the story: “How I Killed Pluto and Why It Had It Coming.”

Five years ago, Brown made a discovery with the help of North County’s Palomar Observatory that spelled the end of Pluto’s special status, at least in the minds of many astronomers.

He says there are only eight planets, not nine, and Pluto doesn’t make the cut. The astronomy organization that names things in the universe had to decide whether Brown’s discovery, a Pluto-like rock orbiting the sun, was another planet (the 10th) or something else.

They decided to call it a “dwarf planet” and, in a highly publicized rethink of the solar system, they downgraded Pluto to the same designation.

Brown hadn’t technically killed Pluto. It still exists, of course. But he’d helped it lose its special status in the solar system. It’s no longer ranked up there with Mercury, Venus, Earth & Co.

Never mind that Brown named his discovery after a “warrior princess” on a TV show. His opinions about Pluto dismayed countless kids and more than a few adults, turning him into one of the few scientists whose office (at Caltech in Pasadena) gets late-night crank calls from annoyed “Pluto-huggers.”

I called Brown yesterday and asked him about his discovery, the science of planethood, and the unusual appeal of a faraway rock named after the Roman god of the underworld.

What did Pluto ever do to you?

It didn’t do anything. I loved Pluto as a kid. Who didn’t? It was this funny oddball out at the edge of the solar system, everybody’s favorite planet. It was the underdog, and how could you not love it?

Do you think it would have had the same appeal if it was named Fred instead of sharing a name with a Disney cartoon dog ?

No. If it had been named the planet Fred, people would say, “I never liked Fred. I’m glad he’s gone.”

Astronomers discovered Pluto in 1930. Why did they think it was a planet?

At the time, there was nothing else to call it. It was the only thing known outside of Neptune, and there had never been anything found out there before. They thought they’d found something big and massive, tugging Neptune along in its orbit. It turned out to be tiny and have an insignificant mass: Neptune doesn’t even know Pluto exists.

When did they figure out it was really small?

It was a slow process. The first nail in the coffin was the discovery in the 1970s that Pluto’s surface is covered with methane ice. You suddenly realized that the reason it’s as bright as it is isn’t because it’s big. It’s because it’s small and covered in ice.

In 2005, you were looking for moving objects in the solar system using images from a Palomar Observatory telescope and you found something that reminded you of Pluto and was also quite far out there.

The process is a pretty simple one: you take three pictures of the sky in the same spot, and you simply look for something that moves. I was looking at things that the computer had flagged as moving, and sure enough there was this one. It was so bright and so far away that I knew it had to be at least as big as Pluto, if not bigger.

Why wasn’t this dwarf planet, as it’s now officially known, discovered before?

The big advantage we had at Palomar is that digital cameras were getting to be moderately cheap for wide-scale astronomic use. We put together the largest digital camera anywhere in the world, sticking a bunch of cameras on one big plate so we could take bigger pictures and scan the sky faster.

You named this thing Xena after the TV character. (The group of astronomers that officially names things later decided to call it Eris.) And you declared that it isn’t a planet. How come?

For the same reason that Pluto’s not a planet. If you look at solar system with fresh eyes — and it’s hard to do — you realize that the eight things we call planets are the big dominant objects in the solar system. You could almost ignore everything else and just go home.

That’s rude to the poor asteroids.

It is rude. Asteroids are very important but to the solar system, but they are debris compared to those eight planets that dominate the solar system.

What are some of the most striking responses you’ve gotten about the official downgrade of Pluto to dwarf planet?

I get hate emails from people masquerading as kids, and some nice crayon drawings from kids putting Eris in the solar system. But the funniest ones are still happening: those are the obscene phone calls that I get in my office, usually at 3 a.m. on a Saturday.

This is five years later, so I like to picture them as 13-year-olds who were mad at the time. They’ve gone to college, joined a frat and can make a drunken call to the guy who ruined their childhood. The calls run the gamut of slightly funny to viciously obscene. If you listen to them, you’re like, “Oh my God.”

You’ve really hit a nerve.


What do you think of the “Pluto-huggers,” as you call them?

I remain convinced — maybe I’m wrong — that it’s not Pluto that they miss. What they really miss is the cartoon solar system, the one that you see on lunch boxes and on kids’ placemats: It always has nine planets more or less the same size, kind of close.

If you look at the real solar system instead of the cartoon solar system, you can’t find Pluto. It’s so much smaller than other things.

They miss the cartoon Pluto, and they don’t know the real Pluto, which they wouldn’t miss at all.

Please contact Randy Dotinga directly at and follow him on Twitter:

Randy Dotinga

Randy Dotinga is a freelance contributor to Voice of San Diego. Please contact him directly at

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