By 5.30pm local time in Prague (GMT+2), we were on version three of the planet definition. A second discussion had been scheduled, after lunchtime saw vociferous opposition to version two (which I blogged about here). A crowd gathered outside the designated room.

I was expecting to be treated to another lively exhibition of dissent – but it was not to be. Jocelyn Bell Burnell, the astronomer who discovered pulsars and a member of the IAU’s resolution committee, took formidable control of the meeting.

With only 45 minutes set aside, she said, comments were to be no more than “elevator pitches” – an idea sold in the time it takes a lift to travel one floor. “And I will cut you off if you are not brief,” she warned. The astronomers meekly followed orders.

Version three, distributed as we filed in for more drama, was a compromise that also seemed to have dissipated much of the earlier anger. It differed from version two mostly in emphasis.

That earlier definition had required first and foremost that a planet be round, then lumped planets that were not “dominant” in their local population into a subcategory of dwarf planets. The new definition required that a planet be both round and dominant, then put any round objects left over into a “dwarf-planet” category.

The details get confusing, but Bell Burnell spelled out the consequences of shuffling the priorities, “this means that Pluto is a dwarf-planet, but it is not a planet.”

Would that be acceptable to the assembled astronomers?

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I’m just back from the open discussion on what makes a planet. It stopped just short of fisticuffs. For people who argue that defining a planet is a meaningless labelling exercise, astronomers seem to care a great deal.

Within seconds of comments being invited, queues formed at the microphones. One by one the waiting astronomers denounced, in tones ranging from offended to furious, the idea of a planet that had been put forward by the IAU. As this went on, the representatives of the planet definition committee sitting at the front slumped into their chairs, heads propped on hands.

The hour allocated for discussion today wasn’t enough for everyone to vent their views. At one point, the meeting chair, president of the IAU Ron Ekers, tried to hurry things along. This prompted someone near the front of the cavernous hall to shout out:

“If this is a democracy, listen to the questions. You don’t have to speak so much, let the people speak!” And that was just for starters.

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Oh goodness, I’m disappointed I missed this. Scroll down to the last item. It recounts how, last week, cake was served to celebrate the 1000th anniversary of a supernova that went off in 1006 AD, the brightest in recorded history. I love cake. And this one had a picture of a supernova remnant in icing. How briliant!

But, obviously, there’s more to SN1006 than cake (consumed in less than 1000 seconds, according to the report). Wikipedia provides a brief account here. The supernova was also the inspiration for a two day discussion meeting “Supernovae: one millennium after SN1006” at the IAU General Assembly.

Before the meeting, I asked one of the session organisers, Wolfgang Hillebrandt of the Max-Planck Institute for Astrophysics in Garching, Germany why people were still interested in something that happened so long ago. Was there really anything left to learn? He said that astronomers were looking for the companion star that triggered SN1006 to explode, but didn’t think that anyone had found it. “I don’t think there is anything close to being published,” he said.

Unfortunately, I can’t give you an update from the session, because I was still slaving in Nature’s London office when it was taking place on 17-18 August. The program, if you want to check it for yourself, is here.

In conjuring up a new category of planets to be known as “plutons” to tidy away Pluto and its cousins, the International Astronomical Union has attracted a hail of criticism.

My colleague Geoff Brumfiel reports here on the angry reaction of one geologist who studys a type of rock formation already known as a “pluton”. This geologist was concerned at the term being hijacked, and he’s not the only one upset.

My dinner companions tonight included some (very tired) members of the planet definition committee. They said that they’d received hundreds of emails over the past few days from geologists complaining about the use of “pluton” in the proposed planet definition. Many of these emails, they noted, came from Australia. Is someone over there running a campaign?

Another problem has emerged in translation. The french name for Pluto is — you’ve guessed it — Pluton. The definition committee thought this linguistic borrowing would give the pluton label special appeal for French-speaking astronomers, but apparently some object.

All this leads to speculation that tomorrow’s revised definition, whatever other changes it contains, will include a replacement word for “pluton”.