Archive for November, 2010


Posted in Personal with tags , , on November 29, 2010 by davidnm2009

Britain is currently having one of these strange things called a ‘winter’. This is actually rather unusual. We share latitudes with Moscow and Newfoundland, where multiple feet of snow are normal, weekly events. However, in southern England at least, we may see a day or two’s snow in any typical winter. This is due to the combination of the Gulf Stream and also the fact we’re an island (maritime climates tend to be cooler in summer and warmer in winter).

However, this year, it’s November and we already have snow.

This is rather unusual. I gather it’s a bit more normal in northern England, and hardly unknown in Scotland. But there was a dusting of snow in Stevenage on Wednesday – it surprised me on the way to work. I spent the weekend on the South Coast, visiting family – and it snowed there. This is very unusual indeed around the Solent.

Also, the temperatures are so low that they actually appear to have erased the London heat island. I had to go through London today – dodging the Tube strike – and went right through central London. As I walked past the Eye and along the Embankment, I was absolutely freezing! I think it was actually colder in London then it was on the coast.

It’s strange, but this is quite unusual in Britain. In fact, to be honest, we don’t really seem to expect winter to actually be cold, and we get all surprised when it is. (It certainly surprised me – much as I love my beige jacket, it doesn’t stop an ice-cold northerly wind!) In a way I’m reminded of my own comments about heatwaves a while back.

Of course, I’m sure the next few days will bring out a predictably-depressing spectacle. I imagine the usual Daily Mail-ite climate-deniers will jump all over it. (After all, one cold week in November overturns decades of statistical evidence, right? I mean, the plural of anecdote is definitely data, don’t we all know?) We had all of this nonsense last year too, despite the fact that the previous winter was something of a fluke event.

(Okay, that was a rant. But I did get encounter the Daily Mail over the weekend, so I needed a vent…)

Stung by a WASP

Posted in Astronomy, Science with tags , on November 25, 2010 by davidnm2009

Here’s an example of something that’s so very, very frustrating.

Basically it’s an object that’s been spotted in a transit survey. As such, it has a robust radius and a reasonably-robust mass estimate. It is in mutual orbit with a reasonably well-behaved F9-type star. That is to say, a spectral type where it’s possible to do age determinations and metallicity estimations, at a level of passable precision. Now, as presumably star and brown dwarf companion must have formed together, we’d expect a common composition. (Or at least, we can reasonably assume a common composition.)

Now, brown dwarfs have some joys but also some nuisances. The major nuisance is that there are a lot of degenerate properties – that is, features of the spectrum that can be affected in the same way by several different processes. Obviously, this makes distinguishing between them really, really difficult. Continue reading

HD 10180 – Densely-Packed Planets

Posted in Astronomy with tags on November 24, 2010 by davidnm2009

Some more exoplanet news. There’s a paper out describing a system with a rather-startling minimum of five (and maybe seven) planets. These are all Neptune-analogues, in mass terms, and they’re packed in between 0.06 to 1.4 AU. So that’s a lot of planets in a pretty small space – transpose them into our solar system, and they’d all orbit inside of Mars.

20 years ago, no-one would have believed that an arrangement of planets like that could even *exist*, let alone be stable.

Also, something else caught my eye. Looking at the numbers for the star – luminosity, metallicity, age – it really does look very solar. No surprise, I suppose, as the spectral type is G1 against G2 for our Sun. Also, planet g, with a suggested orbit of 1.4 AU. That’s presumably still inside the star’s biozone. So if it had any decent-sized moons, the possibility of an interesting climate can’t be entirely ruled out.

Saturday Sketch

Posted in Art with tags , on November 21, 2010 by davidnm2009

Here’s a quick sketch for Saturday very, very early on Sunday:

Because every weekend needs a dark tower of dark ominous-ness.

The Explorer’s List

Posted in Astronomy, Science, Space with tags , , , on November 19, 2010 by davidnm2009

Neptune and Triton, seen by Voyager 2. Image credit: NASA, via APOD.

I’m interested in space exploration. (You’ve probably worked that out by now, right?) I thought it might be interesting to compile a list of places that we have (in some sense) ‘been to’. I’ve ranked the objects in the list by the degree to which they’ve been explored. So something visited by human beings outranks something orbited by a probe, which in turn outranks something just flown past. Note that the categories aren’t exclusive – objects that have had landers on them have also very likely been orbited or flown past too.

  • Explored by actual human beings:
  • The Moon
  • Landed on by remote probes:
  • Venus – the Soviet Venera missions
  • Mars – many (Viking, Pathfinder etc.)
  • Jupiter – the Galileo mission dropped a probe into Jupiter’s atmosphere.
  • Titan – the Huygens lander, returning our only surface photo of an outer-system body.
  • The asteroids Itokawa and Eros.
  • Fly-bys and orbits:
  • Mercury – Mariner 10 and now Messenger (note that Messenger has entered orbit around the planet)
  • Jupiter’s Galilean Moons, Io, Europa, Callisto and Ganymede – the Galileo probe again
  • Saturn – Poineer 10 and 11, Voyagers 1 and 2 and Cassini
  • (Also arguably various Saturnian moons, depending on what you count as a flyby – Cassini and also Voyagers 1 and 2 again)
  • Uranus – Voyager 2
  • Neptune – Voyager 2
  • Also various asteroids.
  • Scheduled flybys
  • Pluto/Charon – New Horizons, estimated for 2014
  • Vesta – Dawn mission, due 2011
  • Ceres – Dawn mission, due in 2015

And that’s it, as far as I know. Everything else is purely telescopic.

The list is interesting as much for its gaps as its items. It’s no surprise that the outer solar system isn’t too well explored. Uranus orbits twice as far out as Saturn, after all. However, on the face of it, it does seem rather surprising that Mercury has only been visited twice. There’s actually good reason for this – it’s because the planet is sat deep in the Sun’s gravity well, where manoeuvring is vastly more fuel-expensive, and the Sun is much more likely to snag an unfortunate probe off course. The upshot is, it’s actually cheaper to send a probe to Jupiter or Saturn then it is to send one inwards to Mercury, weirdly enough.

Also, this shows just how little we have explored even our own solar system. If it’s still possible for one human being to knock out a list like this, in the space of half an hour or so, well … draw your own conclusions! I’d like to see us add at least one more planet to the first category within my lifetime, but whether that will happen or not, who knows?

Paging Dan Brown…

Posted in Science with tags , , on November 18, 2010 by davidnm2009

…or not, as the case may be.

But still – antimatter! Antimatter!

Actually, being slightly more serious, anti-protons and positrons (= anti-electrons) are not as rare as you might think, based on some media articles. Cosmic ray showers make a certain amount of anti-particles all the time. Supernovae spit them out, along with a lot of other stuff. And anti-atoms have been ‘manufactured’ before. The difficulty is getting them to sit still, and isolating them sufficiently from normal matter.

Of course, presumably, there must be a way to do it. The universe we live in is spectacularly, overwhelmingly weighted toward ‘matter-matter’ (if you will) rather than anti-matter. And yet, on the face of it, there’s no obvious reason why that should be. Physics doesn’t really seem to be that picky between the two, barring the decay of the K-meson (if I’ve remembered that correctly). After all, antimatter has the same mass, the same inertia and the same magnitude of charge as normal matter, it’s just that the signs are reversed. (Particle people will no doubt be going, ” ‘Just’, he says. Harrumph.” And they have a point. It’s an important difference.)

The odd thing is, as far as I know, still no-one really knows why we had an excess of matter over antimatter in our universe. There clearly was an excess, since the atoms in our bodies weren’t annihilated within a picosecond or two of the Big Bang, but the why of it remains speculative. Possibly the matter/anti symmetry breaks down at extremely high energies? Or quantum tunneling is somehow more favourable to ‘our’ sort of matter, so when the quarks stick together, they tend to gloop into ‘our’ configuration? I really don’t know.

And nor does it seem that anyone else does, either.

Drinking Contest

Posted in Amusing, Art with tags on November 14, 2010 by davidnm2009

(Yes, I was bored earlier – I had plenty of better things to do, before you ask, but no, I wasn’t doing any of them!)

(Larger and more detailed version here, as usual.)