Who’s so tEMErarious in the fierce Orion?

Looking for trans ethyl methyl ether in Orion KL

When the Big Bad Wolf threatened the Three Little Pigs with blowing and blowing until destroying their houses, they challenged him by saying that each would build his house of a different material: straw, wood and brick. Obviously, it doesn’t take long to build a thatched or wooden house as a brick house (so the story criticized the vagrancy of two of the piglets). The wolf managed to blow down the houses of straw and wood (imagine the lung power of the canis lupus), but not the brick one, where the three tEMErarious piglets ended up scalding the fierce wolf. (My inner child wondered if that brick house, made so hastily, was not going to be a terrible quality one…).

The key factor, in this case, was time.

In Astrochemistry we also handle that variable (as in the entire universe) to determine the chemistry of gas in the interstellar medium. How long does it take for changes to be made to the chemistry of a given environment? What conditions of temperature, pressure, or other parameters, are needed?

In this particular work, we talk about the tentative detection [1] of a molecular species: by identifying a large number of lines of rotation of the molecule, a team of researchers, led by Belén Tercero (ICMM-CSIC), has presented in this paper the tentative detection, in Orion KL, of trans ethyl methyl ether (t-CH3CH2OCH3, from now on, tEME). In addition, in order to try to restrict the type of chemical processes that occur in this source, they also carried out the search for gauche-trans-n-propanol (Gt-n-CH3CH2CH2OH, an isomer of tEME, which we will call, for short, Gt-n-propanol).

But we’ve put a lot of technicality in at once… what does all this mean?  Let’s go in parts.

First, what are rotation lines?

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 (i.e. when its energy levels rise or drop).

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 in space around their bonds.

These rotation changes can be detected with radio telescopes in the millimetric and submillimetric wave domain (the less energetic range of the electromagnetic spectrum), resulting in spectra loaded with lines to “translate”.

Thanks to the analysis of the data provided by the IRAM 30m radio telescope and the ALMA interferometer, lines of both species (tEME and Gt-n-propanol) have been identified, even being able to obtain maps with their spatial distribution [2].

Thousands of lines

A few years ago an exhaustive study of the Orion KL region was carried out with the IRAM 30m radio telescope. The result showed more than 15,400 spectral lines of which some 11,000 were identified and attributed to 50 molecules (199 isotopologues and different vibrational modes). To date, there have been several jobs based on this data.

As a result of fruitful collaboration between astrophysicists and laboratory molecular spectroscopy experts, 3,000 previously unidentified lines were assigned. Three molecular species and 16 isotopologues and vibrationally excited states of molecules abundant in Orion, never before detected in space, were identified.

With the same data set, now, a research team, led by Belén Tercero (ICMM-CSIC), has published the detection of another new molecule in space, tEME. In addition, several unidentified lines in this data have been provisionally identified as belonging to Gt-n-propanol (a tEME isomer).

Spatial Distribution

Our protagonist molecular species (which, more than a wolf, looks like a poodle).

With ALMA data, maps of the spatial distribution of oxygen-carrying saturated organic species containing methyl, ethyl and propyl groups have been carried out, estimating the abundance ratios of related species and the upper limits of column densities of undetected ethers [3].

As for its provenance, while the tEME comes mainly from the “Compact ridge” area of Orion, the Gt-n-propanol appears in a hot core of southern Orion. Until now it was thought that the “Compact ridge” area was the main host of all oxygen-carrying organic saturated species in Orion, but recent studies (including the one at hand) show other regions within Orion KL where these complex oxygen-rich molecules are significantly more abundant than in “Compact ridge”. This result suggests a chemical complexity not yet well characterized, related to the processes that create and segregate these species in the region.

The abundance and spatial distribution of these molecules suggest important processes that would take place in the gas phase that occurs after the evaporation of the mantle that would cover the dust grains in the warmest areas of the region.

To summarize, by combining IRAM 30m and ALMA data, we can provide a solid starting point for the definitive identification of tEME in the interstellar medium.

Fierce Wolf

The formation of complex molecules in space is a mystery to unravel. Although, for starters, we should differentiate the term “complex molecule” on Earth and in space. Of course, given the hostile conditions in the interstellar environment and in environments such as Orion KL, combining molecules and forming more complex species is an achievement. Hence species that on earth can be common, in space are called “complex”.

Gradually we discover that dust grains, protective “bubbles” created by pressure, temperature and jets of material, and other phenomena that take place in space, generate environments that promote these changes.

As fierce as Orion KL is, there seem to be places where these chemical combinations make their way and, as much as it “blows”, they will continue to stand, tEMErarious, facing the hostilities, combining and surprising us over time.


[1] In Astrochemistry we usually talk about tentative detection when we have almost all the keys to confirm the presence of a molecule in a certain environment but we lack a piece of the puzzle (in some cases, more than one). In this case, we talk about tentative detection because certain species that have a very abundant and complex pattern of rotational lines must be identified over a very wide range of frequencies to ensure detection. This work shows that in the frequency range studied there is no missing piece of the puzzle.

[2] Maps of CH3OCOH, CH3CH2OCOH, CH3OCH3, CH3OH, and CH3CH2OH are also provided to compare the distribution of these oxygen-carrying saturated organic species containing methyl and ethyl groups in this region. The work also includes abundance quotients of related species and higher limits to the abundances of undetected ethers.  An abundance ratio of N(CH3OCH3)/N(tEME) ≥to 150 is derived in Orion’s “Compact ridge”.

[3] Column density is the amount of material contained in an imaginary cylinder (usually with a cross-section area of 1 cm2) between an observer and an astronomical object. (Oxford-Complutense Astronomy Dictionary, Ian Ridpath, 1999, Editorial Complutense). The derived column densities for these species at the location of their emission peaks are ≤(4.0±0.8)×1015 cm−2 and ≤(1.0±0.2)×1015 cm−2 for  tEME and Gt-n-propanol, respectively. The rotational temperature is ∼100 K for both molecules.

Link to the paper: Searching for Trans Ethyl Methyl Ether in Orion KL

Image: «Methoxyethane-3D-balls», by Ben Mills and Jynto – Derived from File:Ethanol-alternative-3D-balls.png. Available under public domain license via Wikimedia Commons.

Originally published in Spanish on the Naukas website: ¿Quién tEME al Orión feroz? (2016/01/25).

Flatulence in Space (II)

A few months ago, from Astromol’s facebook, we posed a challenge: if we could reach four hundred followers, we would write more reports on stinky gases in the universe. And we got over them. In fact, since the publication of “Flatulence in Space (I)“, we have exceeded eight hundred. So here’s the second part of “spatial flatulence,” dedicated, this time, to carbonyl sulfide.

“Nature never ceases to amaze us.” As if it were the script of a documentary, I see myself pronouncing this phrase as I choose the title of this report. I know it’s a little scatological, but it’s totally true: let’s talk about some of the gases that are in our flatulence. Watch out, in our flatulence there’s not just gas, there are more things, but we’re not going to talk about those. The compounds that give farts that smell (not all smell the same, it will all depend on what we have ingested) are well known. And some of them are also in space. Now you’ll understand why I, who usually talk about Astrophysics and Astrochemistry, get into these issues.

After talking about hydrogen sulfide (H2S) in “Flatulences in Space (I)“, today we will focus on carbonyl sulfide (OCS) which, although having a very nice name, does not fall short in terms of danger compared to the previous compound.

On our planet, carbonyl sulfide, a colorless gas, is produced in swamps, inside volcanoes, in the oceans, in hydrothermal sources and, pay attention, in fertilized soils (manure) and other environments. It is present in some grains and seeds, and in some cheeses and prepared cabbage.

Humans release carbonyl sulfide to the environment after certain processes (no, we don’t yet talk about farts), for example, combustion, when we use the car, in coal-fired power plants, when processing fish (all this is said by Wikipedia and I believe it), in the manufacture of some products, but in all these cases they are a result, an impurity generated after a process (what is called a by-product).

It is known that inhaling it in high concentrations for a short time can cause narcotic effects in humans and can irritate eyes and skin. But if we stay too long, it can cause seizures and lead to collapse and death from respiratory paralysis. This happens because, as with hydrogen sulfide, it affects our nervous system, nullifying our olfactory capabilities and leaving us exposed to danger. So you know, if you detect something smelly, walk away just in case.

Another danger is its combustion capacity: it is a highly flammable gas [1]. And according to this company in Canada, under pressure it’s corrosive.

Finally, as you already knew, this sulfur compound is found in flatulence, albeit in a very low proportion. In fact, its presence in the environment is generally quite low, although it stinks of rotten eggs.

Apparently, this that smells so bad can be related to… (we know we repeat this a lot in astrochemistry and astrobiology, but it is simply the truth) the origin of life!

Carbonyl Sulfide in Space

It was 1971 [2] when Jefferts and his team detected the presence of OCS in the interstellar medium, specifically Sagittarius B2 (Sgr B2), one of the largest molecular clouds in our galaxy (its total mass is three million times the mass of the Sun and its size about 150 light years). Again, as with hydrogen sulfide, Penzias and Wilson, Nobel laureates thanks to their discovery of the cosmic microwave background, signed the article describing this finding along with P.M Solomon, astronomer at Columbia and California universities (remember that Jefferts, Penzias and Wilson worked for Bell Telephone Laboratories). [2]

In 1995 Mauersberger et al. reported on the first detection of carbonyl sulfide in an extragalactic source: the Silver Coin Galaxy or NGC253, a very bright galaxy that is nearly 13 million light-years from us.

The same year, the OCS molecule was also detected in ice mantles covering interstellar dust grains, near the W33A protostar.

Paradoxically, it took time to confirm its presence in our Solar System. In 1997 L.M. Woodney led the team that found this molecule on Comet Hyakutake. (As you may recall, in “Spatial Flatulences I”, we also talked about comets and the importance of detecting these compounds in these objects.)

But today we are going to focus on the detection of OCS in the atmosphere of the planet Venus, carried out in 1990. Studies suggest that, due to the difficulty of carbonyl sulfide to be produced inorganically, and since, on Earth, the presence of this gas is considered an indicator of biological activity, it would be interesting to review the atmospheric chemistry of the planet. But what happens, does anyone suggest there’s life on Venus?

Not exactly, but apparently in Venus’ atmosphere, about 50 km from the surface, lies the only place (after Earth) of the Solar System with an atmospheric pressure of almost one bar, temperatures that would allow the existence of liquid water (0 to 100 °C ), energy provided by the Sun and life-critical elements such as carbon , oxygen, nitrogen and hydrogen.

So far, missions launched to Venus have not detected microbial life. What has been done has been to confirm the distribution of OCS in the Venusian atmosphere thanks to ESA’s Venus Express mission and VIRTIS instrument, aboard the satellite. The data confirmed in 2008 that there is more carbonyl sulfide in equatorial regions than in high latitudes.

So, if we go to Venus, we should be prepared to smell what will surely not be a dish of taste because there smells like flatulence too. Although no, it’s not our last word.  

To be continued…


[1] Air flammability limits (under standard temperature and pressure conditions): 12.0-28.5 vol%

[2] Ten years later, in 1981, there were already ten interstellar and circumstellar sources in which the presence of SCO had been detected.


Space-filling 3D model of carbonyl sulfide. Ball-and-stick model of the carbon disulfide molecule, OCS. C=S bond length of 1.5601 Å; C=O bond length of 1.1578 Å. Data from CRC Handbook of Chemistry and Physics, 88th edition. Credits: Ben Mills. Wikipedia.


Data about OCS ant its discovery in different environments in www.astrochymist.org.

New Jersey Department of Health: hazardous substance fact sheet for Carbonyl Sulfide https://nj.gov/health/eoh/rtkweb/documents/fs/0349.pdf

Originally published in Spanish on the Naukas website:  Flatulencias espaciales (II) (2016/01/13).