Last month, there was some interesting news from the world of extrasolar planets – firstly, the publication of a new study in Astrophysical Journal Letters which suggested that a planet in the nearby Gliese 581 star system might be hospitable enough to support liquid water, and which thus highlighted the possibility of oceans, clouds, rainfall and all the perplexing and wonderful climatic complications we enjoy so much here on this planet.
Granted, the new evidence stems not from actual observations but from computer models, so a note of caution is perhaps in order, but even so, this news is rather heartening.
Gliese 581, like our own dear old solar system, is in the uncharted backwaters of the unfashionable end of the western spiral arm of the Milky Way galaxy, just over 20 light years from us and in the constellation of Libra. Its star is a red dwarf, and to date, astronomers have determined that there are at least four and maybe even six planets in orbit around it.
The four planets astronomers think definitely exist are (from innermost to outermost) Gliese 581-e, Gliese 581-b, Gliese 581-c and Gliese 581-d. Apart from having stunningly imaginative names, the other things to note are that 1) there is no planet Gliese-a, as this is the red dwarf star itself (took me a while to figure this out) and 2) they are named in order of discovery, which is why the physical sequence goes confusingly from e through to d. (By the way, some scientists think Gliese 581 also has stars f and g, but these may not actually exist and so are, much like Schrödinger’s cat, in a sort of indeterminate state, which has to be rather worrying for the planets’ inhabitants, if any.)
The innermost is e, discovered in 2009; it appears to be small (about 1.7 times the mass of Earth) and scientists think it might also be rocky. It’s also probably very hot, as it is much closer to its star than is advisable for any sensible planet thinking of supporting life forms.
Next is b, the first to be discovered (in 2005), and this one’s about as big as Neptune.
After that comes c, discovered in 2007 and about 5 and a half times as massive as our world, thus in a category of planet called the “super-Earth”. Alas, it probably is not inhabited by super-Earthlings, because, like its neighbours e and b, it’s still a little too close to its parent star for comfort.
And then there’s d, another super-Earth and about the same size as c. Discovered in 2009, it is just on the edge of the “Goldilocks zone” where liquid water – and, therefore, life – might exist (and in fact it was this planet that was the subject of the recent study.) In 2009, a radio message was beamed towards Gliese-d by the Australians, in the hope that some sufficiently advanced Gliesans might intercept and decode it (and be friendly enough not to send us an invasion fleet by return of post.)
The reason I find all this rather encouraging is that if planets are very common in our universe – and the fact that we’ve managed to spot dozens of them only a few light years away suggests that they are – and if there are huge numbers of planets in the Goldilocks zone (which, again, seems quite possible), then somewhere, surely, there must be aliens. And maybe, just maybe, there are even a few ETs living in our own neighbourhood. I think it more than likely that they would only be analogues of Earthly life-forms such as algae or bacteria, so making small talk with them might be a little dull, but even so.
The other bit of planetary news I liked was the announcement from a joint Japanese/New Zealand astronomical survey that there are probably vast numbers of solitary planets which are not orbiting around stars but appear to be roaming around the galaxy all by themselves. Rogue planets! And hundreds of billions of them in this galaxy alone – twice as many as there are main-sequence stars, according to the astronomers. They would probably be very cold and dark indeed, and I’m somehow reminded of the home world of the Eddorians, supreme baddies in EE Doc Smith’s magnificent Lensman series of novels, who exist on an orphan planet which, in the stories, has arrived in this universe from another (and presumably far nastier) dimension.
Even if not inhabited by a frigid-blooded, poison-breathing race of monstrosities eager to bend the galaxy to their rule, these myriads of rogue planets could, I suppose, be considered at least hazards to navigation. Of course, that will only be a problem for us in the millennia to come, I suppose, once humanity develops faster-than-light travel, so we won’t need to worry about them for a while. Unless, of course, a rogue planet happens to show up in our solar system next year, to coincide with the end of the Mayan calendar, let’s say – in which case, it might be an appropriate time to panic.
Panic, however, is not normally a very useful response, a fact that was recognised by the late Douglas Adams, who designed his Hitchhiker’s Guide to the Galaxy with large friendly letters on the cover which said quite clearly “Don’t Panic”. Which leads me to the other thing I wanted to mention, that a couple of weeks ago it was Towel Day, a sort of commemoration of Douglas Adams, and a celebration of the towel, which, according to the Guide, is “about the most massively useful thing an interstellar hitchhiker can have.”
I had completely forgotten about this. But looking at my diary, I realise that by utter good fortune, I had indeed known where my towel was, on Towel Day. Because I had taken the opportunity to pop out of the office at lunchtime and go for a nice cool swim at my local sports centre.
My towel is a large, sturdy one, made of plain blue cotton. It lacks advanced nutritional features such as stripes containing protein, vitamin B and C complexes or wheatgerm extract, which would come in handy if I ever found myself trapped in the hold of a Vogon constructor ship, on the way to one of the neighbouring exo-planets we’ve been discovering of late. However, for something like a welcome dip in the pool on a warm Wednesday afternoon in May, it is just about perfect.