Friday, 27 August 2004

Too Many Planets

File this one under 'Space'.

At our current level of technology, we should have great difficulty finding planets obitting other stars. The Planets would have to be really, really close to the parent star, or just very close indeed and absolutely huge. This is because the only way we have of deducing the existence of a planet is either by the perturbation of the orbit of the star, or (recently) via occultation, the 'blink' that happens when the planet passes in front of the parent, dimming its light slightly.

Trouble is, we're finding not just a few, or dozens, but over a hundred now.

Consider one of the systems that's the closest in nature to ours :
In a discovery that has left one expert stunned, European astronomers have found one of the smallest planets known outside our solar system, a world about 14 times the mass of our own around a star much like the Sun.

It could be a rocky planet with a thin atmosphere, a sort of "super Earth," the researchers said today.

But this is no typical Earth. It completes its tight orbit in less than 10 days, compared to the 365 required for our year. Its daytime face would be scorched.

The planet's surface conditions aren't known, said Portuguese researcher Nuno Santos, who led the discovery. "However, we can expect it to be quite hot, given the proximity to the star."

Hot as in around 1,160 degrees Fahrenheit (900 Kelvin), Santos told

Still, the discovery is a significant advance in technology: No planet so small has ever been detected around a normal star. And the finding reveals a solar system more similar to our own than anything found so far.

The star is like our Sun and just 50 light-years away. A light-year is the distance light travels in a year, about 6 trillion miles (10 trillion kilometers). Most of the known extrasolar planets are hundreds or thousands of light-years distant.

The star, mu Arae, is visible under dark skies from the Southern Hemisphere. It harbors two other planets. One is Jupiter-sized and takes 650 days to make its annual trip around the star. The other planet, whose existence was confirmed with the help of the new observations, is farther out.

The three-planet setup, with one being rocky, is unique.

"It's much closer to our solar system than anything we've found so far," said Alan Boss, a planet-formation theorist at the Carnegie Institution in Washington.
So we have one 10x (actually 14x) Earth-sized planet orbitting closer than Mercury does to the Sun, a Giant like Neptune at about the orbit of Mars, and another Gas Giant 'somewhere further out'.

That's close to our own setup?

Not as such. We have some 4 small, even dwarf planets in the 'Goldilocks belt' (not too hot, not too cold, but just right), another far too close in, then a big gap to a huge Gas Giant (Jupiter), so big it's a great vacuum cleaner of infalling ice chunks from the Oort cloud. Much bigger, and it would be a star in its own right. After than, it's Gas Giants all the way out (except for the oddball Pluto-Charon double planet system).

Of the four planets that could be life-bearing, Venus has been hit by a runaway Greenhouse effect (and renews its surface in massive planet-wide eruptions every now and then), Mars is both a bit cold and far too small to keep much of an atmosphere in the long term, and only the Double-planet Earth-Moon system is placed optimally for carbon-based water-soluble lifeforms. And the Moon, like Mars but even more so, is too small to retain any atmosphere for long.

As I've blogged about before, I think the probability is that "Life As we Know It" is pretty common, indeed (pardon the pun) Universal. Anywhere Life can exist, it will.

But unlike some astronomers, I don't see the latest data about an increasing probability of planetary formation as being a cause for optimism that there's much useable real-estate out there. There are just too many systems with Jovians or Super-Jovians too close, it appears that our own Solar System may have been formed by quite a different mechanism from the rest of the crowd. Unique? With a sample size of One, it's hard to say. But certainly rare.

Again, with a sample size of One, the only method we know of forming intelligent life - at least as intelligent as, say, a Newt, or John Kerry, is by multi-cellular organisms. Mats of Bacteria, hardy and plentiful though they may be, do not cut the mustard. First you need non-cellular organisms (or single-celled ones with no nucleus), Prokaryotes, then single-celled ones formed by a symbiosis of different organisms working together, (Eukaryotes). These then become multicellular organisms, with increasing specialisation of functions by different cell groups, until we have things like John Kerry, with brain cells, bone cells, muscle cells and so on. Colonies of multicellular organisms become symbiotes too, for example people need 'intestinal flora', bacteria, inside their gut to aid digestion.

So we have Prokaryotes banding together and specialising inside Eurkaryotes, then Eurkaryotes banding together and specialising to form larger multicellular organisms, then those large multicellular organisms banding together and specialising into organisations, such as the USA, or Microsoft, or the local football team. It's very Fractal, the smallest part contains the pattern for the growth of larger ones.

All of this (including the last part) requires Evolutionary pushes. When growing a computer system based on Genetic Algorithms (which relies on Evolution to produce the required characteristics of the final system), you can speed things up a lot by having periodic "mass extinctions", and having multiple habitats and niches which form and re-form, so only the most flexible systems survive.

Now a Double-planet system which is therefore tectonically active (ie it has volcanos and continental plates), is perfect for this. And, as mentioned previously, Jupiter vacuums up *most* of the infalling ice-mountains that would otherwise nearly sterilise the joint. So you get periodic mass-extinctions, but not so many as to render life itself extinct, or reset it to the Prokaryotic stage.

It could be that in order to get multi-cellular lifeforms within the 10-20 billion years available from planetary formation till the time the star novas, you need to hurry. It took about 4.5 billion years to get there on Earth, if I remember correctly, even with all the advantages we have.

Now from my reading of things, we have Too Many Planets out there. The configuration of the Solar System may be freakishly rare. That means that we're going to find nice, terraformable real-estate vanishingly uncommon. Worse, it may even mean that in a galaxy, with all its myriads of stars, there is only on average less than one technological civilisation in existence at a time. Possibly a lot less. Of course, to get from one end of the Galaxy to the other is going to take hundreds of thousands of years, assuming no-one invents FTL (Faster-Than-Light) travel. Which would be nice to have, but isn't essential. Keep to, say, 3% of Light Speed (rather than 80%) and Slower-Than-Light travel doesn't require masses of antimatter the size of Jupiter any more as fuel.

That means that we could be the 'Elder Race', the 'Ancients' that were the font of all wisdom and who gave Intelligent Life a nudge throughout the Galaxy.

Bloody Hell.

No comments: