funny science - Pluto’s widow (ENG)

For an occasional yet loyal reader of Science & Vie like me, a big fan of 'vulgarisation', a frustrated scientist who got lost in a business school, the very fact of discovering new planets in our local solar system is emotional. It’s like finding out you have been living with someone for years in the same flat without noticing. It is emotional to have a planet disappear too. We are observing the first exo-planets some light-years away and at the same time we are still discovering small 'planets' in our solar system. Or are they really 'planets'?

Even more touching is the way the scientific community have been reacting to the discovery of the many new ‘objects’ beyond Neptune over the last three years, in what they call the Kuiper Belt. On one hand, Astronomers realised they had to define the word ‘planet’ which of course had no scientific definition so far. After Mike Brown’s team discovered the object 2003UB313 ‘Xena’ in 2003 (bigger object than Pluto), and since many other similar objects have been spotted, the astronomical community realised there are probably hundreds of icy objects about the size of Pluto in the Kuiper Belt. Scientists have to be logical and consistent; therefore either they had to call Xena and all its siblings 'planets', or they would need to downgrade Pluto to being an asteroid and no longer a ‘planet’. On the other hand, many astronomers admitted they were quite fond of Pluto and would love to find a definition that would allow to ‘keep’ Pluto in the Premiership of planethood. It is always a tragedy when your favourite team since childhood is retrograded to second division.

It has to be reminded that Pluto was hardly accepted as a planet from the beginning. Pluto was first observed by Clyde Tombaugh in 1930. It was quite a shock because since 1846 and the discovery of Neptune the 8 planets seemed to form an balanced and harmonious system – 4 telluric planets, 4 giant planets with distances from the sun growing in an elegant geometrical series. And then the former farm boy from Arkansas brought this 9th little boy, much further than the 8th planet, and much smaller – actually smaller than the moon, yes our little moon. So some at the time argued it should be called a comet or an asteroid – like the biggest objects in the asteroid belt between Mars and Jupiter.

But because Pluto was an underdog, because its discovery was a kind of Bob Beamon maverick leap in astronomy, the new kid became rapidly immensely popular. I guess for schoolboys and astronomers themselves it became the cute, late child in the family surrounded by big, big brothers and sisters. le petit dernier. So without any official decision, Pluto became de facto the ninth planet in school books and in school posters.

Retrospectively, we better realise the feat accomplished by Clyde Tombaugh in 1930. It took 76 years, tens of astronomers, digital photography and computer tracking to find more big objects beyond Neptune, only in the 90s. Back in the 20s Clyde found Pluto by looking at thousands of photographs nights after nights. It was a miracle. Again, a Bob Beamon act.

So what did astronomers decide in the end?

One month ago, at the international astronomical union (IAU) held a congress and voted a definition of ‘planet’. A planet has to: (i) circle around the sun, (ii) be round, obviously. And they added a third condition (iii) a planet must ‘dominate its own’ orbit, ie must orbit in an area it has cleared of smaller objects thanks to its own gravity/size/mass. This third condition excludes all the objects from the asteroid belt or the Kuiper from being called planets, but they can be called dwarf planets. And no-one will be forbidden to give them names, even unofficially. This will somehow alleviate the sorrow of Pluto fans. I suspect many boys will start to fancy cute dwarf planets more than big ones, just like they like hobbits, and the final impact might raise the curiosity for astronomy.

One of them had argued that the most important thing was not to disappoint children, some of whom might be disturbed to the point of giving up interest in science if deprived from their pet planet. Another one said it won’t upset current and future schoolchildren at all, but only ageing astronomers and ‘all those of us who used to be schoolchildren.’

But the most touching comment was made by the widow of Clyde Tombaugh. She is now 93 - her husband died in 97 at the age of 90 He lived long enough to start to suspect the Kuiper Belt would provide hundreds of Plutos. But he died soon enough not to see the discovery of Pluto-sized ones.

The charming old lady told the Arizona Daily Star: ‘I feel like I sort of got demoted from my job of being the wife of the discoverer of Pluto. Now I am the widow of a discoverer of a dwarf planet.’