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Coming at the world from an unexpected angle, far too fast to stop.

4,000 Light Years From Home

NewsPosted by Pelotard 2013-01-11 10:41:24

I would appear to have discovered a planet. In my Web browser.

No, really. At least I am one of five who can lay claim to first having spotted it. And this is not as strange an achievement for a translator as it might seem at first sight.

It’s a crowdsourced science project, which anyone can join at www.PlanetHunters.org. The background is this:

In 2009, NASA launched a telescope called Kepler into space specifically to look for planets around other stars. The principle is very simple: look closely at a star, and see if it dims as a planet crosses it. The devil is, as usual, in the details. We’re talking about noticing a speck of dust orbiting a pinhead of light in China, or something similar (I haven’t actually worked out the scale but it usually goes something like that). The speck has to line up exactly with the pinhead. If we were trying to find, say, Jupiter from this distance, the transit would last for a few hours every twelve years, and dim the light by one tenth of a percent – rather less than the regular dimming of the Sun during the 11-year sunspot cycle, and comparable to the optical ‘noise’ generated in the telescope unless you flood it with liquid nitrogen or something.

Still, it works. Out of the 145,000 stars that are monitored, there are a few where planets line up nicely with the star when seen from our perspective, where said planets are big enough to cause the light to dim enough so that it’s noticeable over the background noise, and where their orbital period (‘year’) is short enough so that you can spot several transits (if you see only one, it could be most anything, from a real planet, via a boulder-sized asteroid near Mars, a bolt that someone at ISS dropped and which is now orbiting Earth, and then all the way down to a cosmic ray happening to hit the detector; for a “discovery”, they need three transits so that they can see that it’s regular).

This is where the crowdsourcing comes in. Watching 145,000 stars at regular intervals for several years will generate quite ludicrous amounts of data. Computers can sort out likely candidates – from what I can see, they flag anything where there is a pre-set amount of variation in the data points. But computers are actually quite bad at one thing that the human brain excels at: pattern recognition. The Kepler researchers have thus enlisted the help of some 200,000 human brains to examine their patterns, and it is all done via a Web interface that is so easy that you don’t have to know much about anything at all to contribute usefully to the science, simply by flagging anything that looks out of the ordinary.

Below, I’ve inserted a screen shot of what most of the light curves look like. (Each point represents a measurement; they have been taken every 30 minutes or so over the course of three months.) Nothing very much. Fuzz that falls vaguely along a line across the screen. (The reason the dots don’t fall exactly on the line is that regardless what you’re measuring, and no matter how expensive – sorry, delicate – your equipment is, you will not get exactly the same result twice in a row.)

Sometimes, the star will be variable. It will vary regularly (or, quite often, irregularly) over a period of days, weeks or months. The light curve will be similar, although for reasons having to do with how they are plotted, the curve will normally look a bit less fuzzy around the edges. (If you’re a scientist, the reason will be obvious. If you’re not, the reason is irrelevant.)

And this is what we are looking for. A few data points stand out by being below the rest. This is the light curve of KOI (Kepler Object of Interest) 4760478, and I drew a box around something that looked suspicious to me. (The gap on the right isn’t relevant because it lacks data points altogether, which means that the telescope was doing something else at the time.)

Ta, as they say, Daa.

Of course, I wasn’t alone. Each light curve is examined by a bunch of people, to make sure we don’t miss anything. It appears that eight others spotted this one. (Had I been the only one, it would probably never have been examined by the actual scientists on the project.) On top of that, it’s still only a “candidate”: we’ve only spotted two transits so far, probably simply since the planet has only had time to complete two orbits since Kepler became operative. It’s on the watch list, though, and will probably be confirmed soonish.

And for all the yesterday’s news about discovering planets, I still remember when I was a kid. Not only had we failed to discover any planets outside our own Solar System, but the science books I read – many of them published in the 60s, and many of them based on science from the 50s – were only gradually coming over to the view that planets might be a normal feature of stars. But until 1978, the smart money was betting that planets formed only under highly unusual circumstances, and that our galaxy might contain something like a dozen planetary systems altogether. The first verified exoplanet was announced only in 1992. It’s exploded now: there are currently 854 verified planets on the lists, and Kepler has identified some 18,000 likely candidates that only need more observations to be confirmed.

Was there any point to this, then? After all, I have scanned some 5,000 light curves. Took quite some time. Seems like very little to show for it.

Well, I started out as a scientist, and frankly, looking at various forms of spectra was what I liked most. As they unfold, in a research context, you know that you are actually looking at someone that nobody in human history has ever looked at before. Every new data point can pop up in a new, unexpected place, heralding knowledge that nobody has ever had before. This feeling of adding something new, no matter how small, to the combined knowledge of the human race, is awe-inspiring. (You might find this really, really weird. If you work with golf or sailing, I find you equally weird. Takes, as they say, all sorts.)

If you prefer, you can be awestruck by the human ingenuity. We laboriously dug rare materials out of the ground, and painstakingly put them together to form an intricate device. We put other equally rare and uncooperative materials together in such a way that they could have exploded and killed hundreds or thousands of us, but we controlled the explosion so that the intricate, fragile device was hurled out into space intact. We use the device to look at something so distant that we can’t even perceive it with our own eyes. A few photons were missing for a few moments. And from this, we are able to deduce that a planet got in the way, thousands of light-years away.

And not only that, actually.

This is a figure from the actual scientific publication where they announce the discovery (available in its entirety at arXiv or the Zooniverse; reprinted by kind permission by the authors, as are my screen dumps of the PlanetHunters interface). I’ve coloured “my” planet blue, at the lower right. There is more information available in the paper, but this gives you the top two facts:

1) It’s big. Radius is 12 times Earth’s radius, which makes it something like one-and-three-quarters Jupiters in volume.

2) It’s lukewarm, for a planet. I nearly fell off the chair when I saw that the temperature given is 272 K, which is -1 °C. This is a “theoretical surface temperature”: the planet is very unlikely to have a solid surface at all, and if it does, it lies at the bottom of an atmosphere. Atmospheres provide greenhouse effects, and a planet with an atmosphere is considerably warmer than one without (for Earth, the difference is about 30 °C). This planet is comfortably inside the “habitable zone”, the distance from its star where water can reasonably be expected to exist on the surface of a “rocky planet” like Earth or Mars.

And gas giants like Jupiter have moons.

Imagine we took Jupiter and dragged it to a similar place in our own Solar system. This planet, KOI4760478-1 (this name isn’t official; I’ve formed it by analogy with how they form designations of confirmed planets), circles a star slightly more massive than the Sun, and three times as luminous, at 1.4 times the Earth-Sun distance (that’s some of the ‘more information’ I mentioned earlier). So we’d have to drag it to a place somewhere between the orbits of Earth and Venus, say 1/3 of the way from here to Venus. (We’d have to drag ourselves out of the way, but compared to dragging KOI4760478-1 that’s a piece of cake, or even biscuit.)

Jupiter would probably stay much the same: the main influence on Jupiter isn’t the Sun, but Jupiter itself. It gives off more heat than it gets from the Sun, and this would stay much the same. But the three moons that seem to contain lots of water – Europa, Ganymede and Callisto – would thaw. We would have a system with three potential life-bearing moons. (Io is probably not very friendly to life, and seems to lack water).

Detecting moons around KOI4760478-1 will probably be a task for my grandchildren. But it’s intriguing. All gas giants we’ve seen so far have moons, so it seems very reasonable to assume this one has, too. They will be warm and cosy, and given what we know about planetary development and whatnot, there’s a fair chance that at least one of them would harbour life.

The really interesting stuff starts to happen if more than one of them is inhabitable.

Face it, the reason NASA stopped going places was that there was nowhere much to go. The Moon was devoid of air, water, and anything remotely valuable; Mars was only marginally better endowed and impractically far away. Had we lived around KOI4760478-1, there might have been loads of interesting places to go quite nearby, cosmically speaking.

I leave it as an exercise to the reader to dream up an interesting scenario with three inhabited moons, only two of which have space technology, various religious and political sects setting up colonies all over, and the various colonialistic ideologies that might arise. Then dream up a plot where this is all background and the point is something else altogether.

In the meanwhile, I’ll contend myself with pictures of Endor and Pandora. And I think I’ll lay claim to the third moon, counting outwards from the planet, name it Pelotard and proclaim myself Emperor.

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