Cyanogen: a poison, a comet and a Jedi story

Protonated cyanogen detected in two dark and cold molecular clouds.

For years the hypothesis has been raised that cyanogen could be an important constituent of the interstellar environment, but until now it had been impossible to confirm. Detected in Titan’s atmosphere (Saturn’s satellite) and in the tail of Halley’s comet (although, in this case, it was other compound in the cyanogen family than the one in our history), its finding caused not a few “end-of-the-world” advertisements in 1910. And while it is extremely toxic to humans, science fiction has made cyanogen a habitat for fictional creatures: the Celegians. Together, they form a triad of stories.

Cyanogen (NCCN) is the simplest member of the dicyanopolyynes series. Its name means “what produces cyanosis” (in short, if you breathe it, you turn blue like a smurf of a bad suffocation). It smells like almonds and is colorless. And, as we said, very toxic, so don’t even think about playing with this gas.

This compound has been observed in the infrared range in Titan’s atmosphere, which is rich in nitrogen and carbon compounds, and is believed to be an important species in comets. In fact, let’s make a subsection to tell you the first of our three stories.

The Assasin Comet

Take a sit. Year: 1910. From the Yerkes Observatory, a team of researchers discovers that Halley’s tail has “cyanogen”. The news was published as a small column in The New York Times, but it was not scientific news.

The headline read: “Comet’s poisonous tail”, and after a very brief introduction to cyanogen detection on a spectrum carried out from the Yerkes Observatory, the cataclysm that would mean that Halley’s tail, laden with lethal cyanogen, entered Earth, ravaging all known life. “Cyanogen is a very deadly poison, a grain of its potassium salt touched to the tongue being sufficient to cause instant death. In the uncombined state it is a bluish gas very similar in its chemical behavior to chlorine and extremely poisonous.” The astronomer “Prof Flammarion is of the opinion that the cyanogen gas would impregnate the atmosphere and possibly snuff out all the life on the planet.”

For Marcelino Agúndez, researcher at the ICMM-CSIC (we will talk about him in this article), “Mr. Flammarion was quite a character in his day, but we cannot forget that, in addition to astronomer, he was spiritualist and quite fanciful. Scientifically, it is not argued that gas from the tail of a comet like Halley, whose closest distance to Earth at the time was about 22.4 million kilometers, could not even be mixed with our atmosphere. Fortunately today we know a lot more about these issues.”

Whoever wrote the New York newspaper article had no choice but to add the opinions of other specialists (astronomers) who claimed the classic “I’m afraid not”: “Most astronomers do not agree with Flammarion, inasmuch as the tail of a comet is in a state of almost inconceivable rarification, and believe that it would be repelled by the mass of the earth as it is by the light of the sun. Also it is considered probable that the cyanogen of the comet’s tail on contact with the earth’s atmosphere would be decomposed by combustion into nitrogen and carbon dioxide, in quantities quite harmless to animal life.”


Protonated cyanogen

In this article from “The New York Times” they didn’t really refer to exactly the same species we’re going to talk about now, but to the cyanide radical (CN), that is sometimes called cyanogen.

Apart from its toxic characteristics, and already entering our second history, which centers on Astrochemistry, some hypotheses raise that this family of molecules can be an important constituent of the interstellar and circumstellar medium, but it is very difficult to corroborate this theory because observations do not allow us to detect them clearly.

This is because this species does not have a stable electric dipole moment and therefore has no rotation spectrum so it cannot be detected by radio techniques.

And why do we talk about cyanogen if we can’t detect it? Because a research team, led by Marcellin Agúndez (researcher of the Molecular Astrophysics Group of ICMM-CSIC) set out to confirm its presence in molecular clouds using indirect techniques. Analyzing data obtained with both the 40 meter Yebes radio telescope and the IRAM30m radio telescope, and applying chemical models [1] developed by this multidisciplinary team, they searched for the protonated “cousin” of cyanogen. Finally, the team has obtained the first solid evidence of the presence of protonated cyanogen (NCCNH+) [2] in the cold dark molecular clouds TMC-1 and L483.

The protonated species is polar and can be observed in the range of radio waves. Although protonation can change its properties, it helps us to know that the molecule is there. The bottom line is that cyanogen (NCCN) could have an abundance comparable to that of other abundant and decades-known species such as hydrogen cyanide (HCN).

In short: it was hard to spot it, but now we know that there is cyanogen in the interstellar medium.


And to close this strange triad, the third story is pure science fiction, because you have to know that there are some living beings that appear in the comics of the Jedi stories of “Star Wars” for whom cyanogen is like oxygen to us. These are the Celegians, strange creatures (forgive me the geek-purists, but I don’t quite know how to call them) similar to the octopuses (or brains with legs) that breathe cyanogen and, to leave their planet, have to live in a tank full of that gas.

If the authors of the comic had known in time, they would not have made these beings merely live in a tank, as they could walk through the interstellar environment or the atmosphere of Titan as cool as a cucumber. Well, maybe not so cool, but we could let them try and see what happens.

More information:

Paper: “Probing non polar interstellar molecules through their protonated form: Detection of protonated cyanogen (NCCNH+)”.


[1] The chemical model predicts an abundance ratio of NCCNH+/NCCN of ~ 10-4, implying that the abundance of cyanogen in dark clouds could be as high as (1-10) x 10-8  compared to H2, i.e. comparable to that of other abundant nitriles such as HCN, HNC and HC3N.

[2] Protonated cyanogen (NCCNH+) has been identified through rotational transitions J = 5 – 4 and J = 10 – 9.


Originally published in Spanish on the Naukas website:  El cianógeno: un veneno, un cometa y una historia jedi (2015/07/21).