This is CFBDSIR2149-0403, which I’m sure you’ll agree just rolls off the tongue. CFBDSIR2149-0403 made the news yesterday as one of the more recently-discovered rogue planets. Contrary to popular belief, a rogue planet is not:

• A planet which backstabs other planets.
• A planet which drains the powers of other planets.
• A planet all done up in makeup designed to emphasise the cheekbones.

Rogue planets are instead planets which wander the universe all on their lonesome rather than being gravitationally bound to any star, orbiting the galaxy independently instead of as part of a solar system. There are two ways this can happen: either extreme gravitational interactions with other planets eject the planet from the solar system that formed it at an early stage in its lifetime, or else the planet forms on its own out of a molecular cloud collapse just like a star.

My first reaction when reading the headline to this one was “How the hell did they see that?” Extrasolar planets are mainly detected through their effects on their parent star; either they directly block light from the star at fixed intervals, resulting in a regular dip in the intensity of the light we see emitted from that star, or else the back-and-forth wobble they cause in the star’s motion due to mutual gravitational interaction can be spotted by analysing the wavelength of the star’s light and how it changes over time. If you have a hobo planet going around on its own with no parent star than both of these methods are ruled out and you’re reduced to attempting to detect the planet through directly observing it.

Fortunately a direct detection is much easier when there’s no parent star. It’s usually very tricky because stars are vast sources of electromagnetic radiation which swamp the feeble emissions we might see from a planet in another solar system – kind of like trying to spot a candle when it’s placed next to a high-powered searchlight several kilometres away. With no star drowning out the planet’s emissions, though, we can do a proper direct search; planets out on their own obviously do not emit or reflect light, but they do emit a visible quantity of infra-red radiation, and so IR surveys are the best bet for spotting any potential rogue planets¹.

So we’ve found this (potential) new rogue planet through an infra-red survey, but it’s not even the first (potential) rogue planet we’ve found. Why is it making news headlines? The answer basically has to do with nobody knowing what a “planet” is, really; according to the paper CFBDSIR2149-0403 shares common motion with a star cluster called AB Doradus, implying that it formed at the same time in the same way out of the same molecular cloud as the stars in AB Doradus. It’s one of these rogue planets that (probably) did not form as part of a solar system’s planetary disk, but which instead formed on its own just like a star would. The age of the rest of the stars in the cluster – 50-120 million years – implies that CFBDSIR2149-0403 is also 50-120 million years old, and since we know its age we can compare it to computer models of planet formation in molecular clouds to get a very rough idea of what its composition and mass might be like. It’s important to stress that – as with so much in astronomy – the composition and mass details are essentially an educated guess. Nobody has directly seen any of this stuff and nobody ever will, so guessing is all we can really do. If the guess is correct, though, CFBDSIR2149-0403 has between four and seven times the mass of Jupiter.

This is the first time we’ve been able to pin an age and a mass estimate onto a planet/brown dwarf like this, and it’s a little bit inconvenient for the Astronomical Union, who defined a planet as anything below deuterium-burning mass ranges (about 13 Jupiter masses) and classed anything above that as a brown dwarf. It was assumed up until now that anything forming out of a molecular cloud would have more than enough mass to count as a brown dwarf, with the previous rogue planet possibles having mass estimates that were far too uncertain to come conclusively under the brown dwarf limit. CFBDSIR2149-0403 changes things, though; it implies that planets can and do form out of molecular clouds, and that a significant percentage of the currently known brown dwarf population could also be classed as rogue planets if they came it at the lower end of their mass estimates.

This changes our view of what a molecular cloud can spit out by a fair bit. Of course it’s also possible that CFBDSIR2149-0403 was ejected from a solar system, but I’d consider that extremely unlikely because of how big it is. It’s big enough that it’d be the one chucking other planets out of solar systems, not the other way around. I don’t know what the scientist at the end of the article is blathering about when he raises the possibility of lots of other orphaned worlds floating in space; somebody should point him towards the Nice model research that implies that that sort of thing is a practical certainty given what we know about solar system formation, and that CFBDSIR2149-0403 would merely raise the upper limit on the size of planet that loses the gravitational tug of war. Of course he probably knows that already and is just trying to wax poetic, but this is something scientists should never ever be allowed to do because they’re bloody awful at it.

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Jiiiiim asks

Hentzau a matter of utmost importance has arisen.

According to gentlemen like http://www.youtube.com/user/gorilla199 we are on course to be hit by the planet Nibiru early in the 21st century. Obviously the freemasons are hushing this up but you are a man of science and so I ask: why do you deny that extra-terrestrials from the Zeta Reticuli star system have warned us about this impending catastrophe? It even has a wiki page if that’ll help. http://en.wikipedia.org/wiki/Nibiru_cataclysm

THE TRUTH MUST OUT.

Usually I wouldn’t stoop to laughing at the mentally ill. The true horror of everyday existence is pretty stark and unforgiving — especially in our media-driven first world where everybody has to be the central character in their own particular narrative — and the realisation that you’re just another schlub who isn’t going to get any special treatment from the universe and will be dead and likely entirely forgotten a century from now can be difficult to cope with. So, you know, it’s kind of understandable that your mind might snap (or at least buckle) under the strain and you start to believe that out of all the seven billion people on Earth you and you alone have been chosen to receive thought transmissions from extra-terrestrials in the Zeta Reticuli star system. Perhaps it provides these people with the personal validation and sense of purpose that they’d been so sorely missing up till then, and if it helps them get through life then who am I to judge? Usually, therefore, I would simply pity these people and refrain from mocking them.

Usually.

However, I do have to draw a line somewhere, and that for me that line is etched into the fucking ground right at the point where the public start to give these crazy people more credence than actual accredited scientists, because after that point it starts to bleed into what I have to deal with in my everyday life. I used to do very bad planetarium presentations for school classes as part of my outreach job. Would you like to know what was by far the most popular question I got asked at the end of these presentations? The question that I could pretty much guarantee would come up, and which I actually had to spend valuable minutes of my time coming up with reasoned, logical answer to? The question was this:

“Is the world going to end in 2012?”

Thanks, Mayan civilization. Thanks, Hollywood. Five hundred years of scientific progress have led to a comprehensive, detailed model of the Earth and the surrounding universe which is easily accessible to anyone with an internet connection, but people just don’t want to know. They’d prefer to believe that the Moon landings were fake because it makes them smarter than the people they think covered it up; they’d prefer to believe that climate change isn’t real because it means they won’t have to feel guilty every time they fill their SUV with 32 gallons of petrol; and they’d prefer to believe that there’s some kind of impending apocalypse which flies in the face of all currently established scientific orthodoxy because… actually I’m not really sure about that one. Believing that we’re all going to die tomorrow in some kind of horrifying nightmare cataclysm is a little bit grim, isn’t it? Especially when there’s so much stuff out there that can actually kill us, and which would likely do so with little to no warning. If I were going to pick a personal delusion to shape my view of the world I’d pick one that was a little more pleasant, one which allowed me to avoid exactly the sort of feelings of abject misery and despair that an imminent global catastrophe would tend to promote in the general population.

But anyway. I must say I hadn’t heard of this particular end of the world theory before, but that’s okay because it’s hardly original. People have been tossing around the idea of rogue planets/stars/black holes taking a little jaunt through our solar system and screwing with things in a decidedly terminal manner for years, although usually in a more appropriate venue such as a science-fiction novel. Briefly, here is why none of these things are going to be happening any time soon:

Rogue star: We’d see it coming. Even if it were a dead one that’s stopped burning or a brown dwarf that never quite made it, we’d still see it coming in the same way that we can see Jupiter as it makes its leisurely way around the Sun.

Rogue black hole. We wouldn’t see this coming directly, but that’s okay because a black hole’s gravitational footprint is a dead giveaway. We’d notice little things like the outer planets being wrenched out of their orbits, thousands of objects being punted inwards from the Oort cloud turning the inner solar system into a celestial shooting gallery, stuff like that.

Rogue planet: The most popular version of this apocalypse scenario because idiots think that a planet can be small enough that it can somehow escape detection. They are wrong. We have some of the most sensitive observational equipment in existence, both on the ground and in space, scanning the heavens for precisely this sort of thing. In order for astronomers to miss it a rogue planet would have to be actually physically hiding from us somehow as in the hilarious counter-Earth scenario, and even then we’d see evidence of its existence in the way it affected the orbits of the other planets. Even if we did somehow completely miss a planetary interloper barging its way into the solar system from outside, it wouldn’t be a problem because sooner or later Jupiter and/or one of its orbital resonances would give it a gravitational bum’s rush out of the neighbourhood. So while rogue planets may be popular, they’re actually the most scientifically implausible apocalypse mechanism of them all. The gravitational interactions of planetary-scale bodies are very well understood and it is physically impossible for a hypothetical planet such as Nibiru to pose any kind of threat to the Earth.

Honestly, if I were a believer in Nibiru I’d be more worried about the Zeta Reticulans. Think about it: you’re an alien scooting through some faraway star system in your flying saucer and you notice that an inconveniently large chunk of rock is due to strike a nearby populated planet. Do you

a)      Inform the governments of the world so that they can do something about it.

b)      Inform one random woman so she can tell everyone via the internet.

If your answer is b), then you are a dick alien. I’m sorry, but there it is.

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