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).

IRC+10216 asks for respect for her privacy

In statements made to “The Life of the Stars”, the hottest “celebrities” program of the moment, the IRC+10216 circumstellar envelope has declared to be fed up with being persecuted by the paparazzi.

Distribution of matter around IRC+10216.

It’s been a few years since IRC+10216 rose to fame for going through a rather tumultuous moment in her life. However, in the latter stages, she confesses to being already very fed up with paparazzi’s persecution, who insist (in a way that becomes strenuous) to make known every detail of her daily existence. “I’m especially tired of such an ALMA, it doesn’t leave me alone,” she says angrily. 

Apparently, such “ALMA” has penetrated its intimacies to limits that exceed molecular sizes. Readers of heart magazines and social media users have made multiple comments about it, even with sometimes unwise tweets. “She is dangerously close,” said Luis Velilla (who is causally an astrophysicist and studies stars of this kind) after learning of her statements and her exhausting. Other tweets say “That happens to you for going star” or “as an audience, we don’t like to stay on the surface, we like to go beyond the envelope”.

ALMA, the “paparazzi” of the coldest stars

We have contacted ALMA, the paparazzi of the coldest stars, to find out her opinion. “I was working on cycle zero, which was a bit like my baptism of fire, and I gave to look closely at the celebrity I had closest. Others are dedicated to hot stars. I’m more into evolved, colder stars, who have a lot to tell but who hide their intimacy insistently. It was an impressive challenge for me. It’s not my fault she’s around and she’s a (role) model.”

The last assault on her intimacy perpetrated by ALMA and made public has been the one that has revealed  in detail how silicon is distributed in IRC+10216.

How did this happen?

In the spring of 2012 IRC+10216 was in her things when she realized she was being watched. She had been of interest to the pink press before. But this time it was different. ALMA’s ability to get “to the kitchen” was impressive. As if it were an impressive telephoto lens, ALMA draw with unprecedented precision the map of the distribution SiS, SiO and  SiC2  in the envelope of  this evolved star [1].

For us, who are very gossipy, this has been a real bomb, since knowing the inner parts of IRC+10216 in such detail is very revealing: in particular, the lines of high vibrational levels [2] of SiS come from a very warm region, an area very close to the star with which IRC+10216 maintains a special relationship. This is CW Leonis, who ended up making these statements:

“Yes, IRC+10216 and I have a very close relationship since I reached mature age. This is what happens to evolved stars: we eject the material to the outside in the form of layers. I will not deny it: something special has been born between us. My envelope and I are very close.”

This is not dirty laundry, this is molecules

Penetrating IRC+10216 to the limits with CW Leonis, as if it were the layer of an onion, we stumbled upon SiC2, but this molecule mysteriously disappears as we walk away to, oh surprise, reappear in a thin layer quite far from the star.  This may be due to the capabilities of ALMA [3].

As for SiO, it has a certain extensive and elongated structure. What could this be about? Explaining elongation is very speculative, but it gives rise to interesting ideas.

First, it could be the presence of a dust “belt” in the direction of elongation. This could cause more gas to form due to increased density in that area. Or, maybe, there is a companion star orbiting CW Leonis. This companion star could also create a preferred direction (the plane of the orbit) for material accumulation and increased density, favoring molecular formation. Although it could also be a molecular jet. For now, it’s all assumptions.

For ALMA this has just begun: “I am now finishing cycle two. If in cycle zero I was learning, now I’m taking a wagon: I’ve learned to use my tools and now there’s no one to stop me.”

IRC+10216 has stated that it will continue to grant exclusives as long as the privacy of its relationship with CW Leonis is respected (on the possible companion star she said not much, but it will undoubtedly be another of the hot topics of the “stellar summer”). The most chic community looks forward to news about this relationship that so many articles are generating in the pinker press (scientific, of course).

More information

Paper: “Si-bearing molecules toward IRC+10216: ALMA unveils the molecular envelope of CW Leo” (DOI: 10.1088/2041-8205/805/2/L13).


[1] Detailed maps of the SiS, SiO and SiC2 distribution have been carried out in IRC+10216. In particular, rotational transitions were observed and not only in the fundamental vibrational state, as the detected even SiS rotational transitions of high vibrational levels (v-7) and tentatively (v-10).

[2] Molecules have different energy levels: electronic, vibrational and rotational. Because the energy is quantized, we can know what kind of transition has taken place when a molecular species is excited or deexcited. Within a particular electronic state, the molecule can reach different types of vibrational states (those produced by the vibration of the atoms that make up the molecule) and, in turn, within the same vibrational state, the molecules rotate, producing a rotation spectrum that can be detected with radio telescopes in the domain of millimeter and submillimeter waves.

[3] There is some loss of flow (emission) in the outer thin layer because it has a very large size. This is because in ALMA (and any other interferometer) exists what is called an MRS (Maximum Recoverable Scale), the maximum recoverable scale. This means that any actual structure that is larger than a given formula is filtered and we lose much of its emission.


Image 1: This image shows the central section of a series of images that, as in a scan, allow us to distinguish the distribution of matter around the star IRC+10216. The data for composing this image has been obtained by the IRAM 30m telescope and was developed for the article Molecular shells in IRC+10216: tracing the mass loss history“.

Image 2: ALMA, the “paparazzi” of the coldest stars. Credit:  ESO/B. Tafreshi  (

Originally published in Spanish on the Naukas website:  IRC+10216 pide respeto a su privacidad (2015/07/16).