Tag: Orion

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But… what happens in those globules?

It is not the first time we talk about Orion, nor about the molecular cloud pierced by the winds of its most massive star… but this is about molecular globules. In this constant process of destruction, something is being created.

Gallery of globules detected at the edge of the expanding Orion bubble

Those who have ever read me (poor) will say that we always talk about the same areas of space. Legendary is the series about IRC+10216 (a star and its envelope, better known as CW Leonis) published on this platform, as well as studies related to the chemistry of Orion. This is because both are magnificent “laboratories” that we can observe with relative ease (translation: these places are “close” and bright enough to observe with our telescopes). The study of these areas is aided by new and increasingly precise instruments.

On this occasion, the combination of the IRAM 30 meters telescope (in Pico Veleta, Granada) and the SOFIA stratospheric telescope (which is mounted on an airplane), helped us to discover the presence of an extremely interesting phenomenon.

But let’s take perspective…  In the Orion Nebula there is a good mess. There are massive stars (of about 8 solar masses or more) being born and emitting winds and ultraviolet radiation, which, in turn, destroys the large molecular cloud in which they were born (the one that has provided them with the material and the necessary conditions to condense). In that scuffle, an international research team has detected the presence of small molecular globules.

Expanding gas bubbles – the result of the destruction of the parent cloud – form around young massive stars because wind and radiation violently “sweep” huge amounts of the material. Ultraviolet radiation is responsible for dissociating (destroying) the gas molecules. Similar shapes had previously been found around massive stars in the Milky Way, dozens of bubbles that were detected using infrared images (let’s not forget that those environments have lots of dust and that infrared makes it easy for us to “go through” the opaque outer layers and see what happens inside). The result of this whole process is that the rate of star birth slows down, as the amount of fuel available for the formation of new stars (the molecular gas) is limited.

But there is another consequence: the presence of small globules of molecular gas on the edge of these large expanding bubbles whose existence has been a surprise: “We did not expect this discovery: one does not expect the presence of molecular gas in this kind of environment so turbulent and “sterilized” by ultraviolet radiation, but we have detected a dozen globules of thick molecular gas that have survived these harsh conditions. Most of these globules can be transiting objects that eventually fade or evaporate. But we didn’t expect this script twist.”

This is said by one of the two researchers who has led this work, Javier R. Goicoechea, from the Astromol Group at the IFF-CSIC, who goes on to describe how they are: “The globules are not massive at all, their size is approximately 200 times smaller than the Orion Nebula itself and their typical mass is around a third of the mass of the Sun. That’s why we were surprised to find out what they were hiding.”

And what has been discovered inside those globules that seemed to be just lumps? Well, scientists have discovered that one of these globules is evolving to form a very young, low-mass star. Let’s say it would be the “daughter” of the one who is riding this whole mess (the young, “angry” star, the most massive in the Trapezium cluster, Orionis C, located at the center of the Orion Nebula).

The importance of the movement

To understand what was happening within the great Orion bubble there are several important parameters that until now had been difficult to obtain: knowing how it moves, what forces drive its expansion and what its chemical composition is. Thanks to the combination of the data obtained with these two facilities, the team has obtained the first images that solve the speed of the gas and show the properties of this bubble of 10 light years in size that is suffering the wrath of Orionis C, since the bubble expands at almost 50,000 km / h, providing its peculiar appearance to the iconic region that we know as “the sword of Orion”.

This information has been obtained thanks to the analysis of the emission of gases produced by molecules of carbon monoxide (CO) as well as positively charged carbon atoms (ionized carbon or C+, analyzed in the work led by Cornelia Pabst, of the University of Leiden, The Netherlands).

As the authors of these works state, “It is not yet clear whether these small objects can be a source of very low-mass stars, brown dwarfs, or planetary-mass objects. We have captured the first glimpses of the star-forming processes that are taking place within one of these small globules.”

The team hopes to be able to carry out more observations of the emission of other molecules (more sensitive to the presence of more dense gas inside the globules) to clarify their future and fate. Will they evaporate in the long run or, conversely, will they evolve into a nursery of newly formed stars?

Technical information:

This work is part of an international collaboration that leads two major complementary observation programs. One uses the 30-meter IRAM telescope in Pico Veleta, Spain (Dynamic and Radiative Feedback of Massive Stars, PI: J. R. Goicoechea) to map the emission of 12CO, 13CO and C18O (J=2-1) at a resolution of 11 arcseconds; the other uses NASA/DLR’s SOFIA airborne observatory (C+ Square-degree map of Orion, PI: Prof. A. G. G.M. Tielens) which has produced the largest map of the [CII]158 μm line (usually the brightest line in the neutral interstellar medium) at a resolution of 16 arcseconds. These Orion C+ images are also relevant as a local model in the extragalactic context as the ALMA and IRAM-NOEMA radiointerferometers can detect the emission of [CII] 158 μm from galaxies with very distant star formation (with high redshift).

The consortium consists of the following institutions: CSIC, University of Leiden, University of Cologne, IRAP-CNRS, IRAM, Max-Planck Institute for Radio Astronomy, ESAC, NASA Ames and University of Maryland.

The scientific articles related to this work are:

– J. R. Goicoechea, C. H. M. Pabst, S. Kabanovic, M. G. Santa-Maria, N. Marcelino, A. G. G. M. Tielens, A. Hacar, O. Berné, C. Buchbender, S. Cuadrado, R. Higgins, C. Kramer, J. Stutzki, S. Suri, D. Teyssier, and M. Wolfire. Molecular globules in Orion’s Veil bubble. IRAM 30 m 12CO, 13CO, and C18O (2-1) expanded maps of Orion A. Accepted for publication in Astronomy & Astrophysics (2020).

– C. H. M. Pabst, J.R. Goicoechea, D. Teyssier, O. Berné, R.D. Higgins, E. T. Chambers, S. Kabanovic, R. Güsten, J. Stutzki, and A.G.G.M. Tielens: Expanding bubbles in Orion A: [CII]158μm observations of M42, M43, and NGC 1977. Accepted for publication in Astronomy & Astrophysics (2020).

IMAGES:

Images of the Orion Nebula (M42). The left panel shows the emission of positively charged carbon atoms, observed with SOFIA, revealing a huge bubble pushed by the winds of the most massive star in the Trapezium cluster. The 12CO and 13CO images, taken with the 30-meter IRAM telescope, show the molecular gas in the cloud in which stars are forming, behind the bubble. The # numbers show the position of some of the detected globules at the edge of the bubble. Credits: Goicoechea et al. (2020).

Gallery of globules detected at the edge of the expanding Orion bubble. The reddish colors represent the emission of carbon monoxide molecules detected with the 30-meter IRAM telescope. The bluish color is an infrared image obtained by the Spitzer Space Telescope. The #1 globule coincides with the position of a very young, low-mass star. The white circle represents the angular resolution of the IRAM telescope 30-meters, approximately several times the size of the Solar System. Credits: Goicoechea et al. (2020).

Originally published in Spanish on the Naukas website: “Pero… ¿qué pasa en esos glóbulos?” (2020/07/02).

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Star eats cloud (or “In Orion it’s no time for joking”)

Getting data from a telescope can be very exciting. Basically, because getting them and interpreting them is a whole process that can take several years… Since the observation program is designed, the time is requested, it is granted (or not), the observations are carried out, the data is obtained and, finally, the information is analyzed and extracted… the whole process is a marathon full of uncertainty and challenges.

Image 1: Red-green-blue image showing three different velocities of the gas associated with the heart of the Orion cloud.

Of course, it can be data from a ground-based telescope or a space telescope.

Or, as in our case, it can be both.

SOFIA: Ground or space telescope? Well, both!

We’re talking about a telescope installed in a modified NASA Jumbo 747 aircraft. It is called SOFIA (Stratospheric Observatory for Infrared Astronomy) and, at each observation, it takes flight to the stratosphere, about 13 km above sea level (a couple of km above commercial flights) and goes back down, perching at its Californian airport and returning home to rest.

Each observational flight lasts about 10 hours, and the data obtained are very important, among other things because, right now, there is no instrument outside the Earth (that is, above the atmosphere and its nefarious turbulence) that observes in the far infrared, a range of the electromagnetic spectrum critical to understand how stars form and interact with the interstellar medium.

With a mirror of 2.5 meters in diameter, SOFIA is the name of the whole set. And Javier R. Goicoechea says (I will introduce him in a moment) that it is impressive to see how the whole plane can tremble from the turbulence while the intelligent hydraulic structure that supports the telescope and its instruments compensates for those alterations and remains perfectly still (I would love to change myself for the instrument, I want one of those compensators for my air trips).

Image 2: SOFIA (The Stratospheric Observatory for Infrared Astronomy)

SOFIA is 80% NASA (which has built and operates the observatory) and 20% DLR (the German space agency).

For starters, getting a plane to fly with an impressive door open (yes, you read that right, open), is already quite a feat. That it does so, in addition, with a team formed by telescope and instrument of about 20 tons of weight, also has its complications.

But let’s get to deeper.

It turns out that Javier R. Goicoechea, senior scientist at the Institute of Fundamental Physics (IFF) of the CSIC, participates in an international team that studies the destructive effects of ultraviolet radiation and the strong winds emitted by young massive stars in the interstellar clouds where they are born. Last year the team obtained 10 observation flights in order to map the Orion cloud in the emission of ionized carbon, the brightest emission from interstellar gas. As he states, “SOFIA is like a space telescope, in the sense that it allows us to observe in the infrared above 99% of atmospheric water vapor, but after a night of observations, astronomers and telescope land on the ground to regain strength.”

Image 3: Javier R. Goicoechea (IFF-CSIC) in full flight and data collection. In the background is Jürgen Stutzki (University of Cologne, Germany), co-Principal Investigator of the GREAT instrument.

The results have been really amazing.  

WHAT A PROGENY! Daughters eating parents.

As we have told in other articles, dense clouds of gas and dust are the birthplace of the most massive stars in the galaxy. The mass is concentrated, condensed, the reactions begin in the nucleus and… A star is born!

The more mass the star has, the more violent it is and the less time it will live. The fact is that we know that, in this area of Orion, there are very massive stars -the Trapezium cluster- that are “sweeping” the surrounding material, undoing the cloud that saw them born with their powerful stellar winds and their intense ultraviolet radiation. A kind of “parentophagy” (I know this word does not exist…).

The data obtained with SOFIA have revealed that this happens much earlier than previously thought. In just a few hundred thousand years the winds coming from the most massive star of the Trapezium have pierced the natal cloud, creating a huge bubble, whose expansion and movements have been revealed thanks to the 3D observations obtained (have I not said that an amazing 3D film has been made with the data?). A single star giving shape to one of the most observed and known regions of the sky.

What a blow.

Measuring speeds for the first time

The results obtained have given, for the first time (yes, we always say that because it is very cool in astronomy to say “as never before”, “for the first time”, “with an unprecedented resolution”, and again and again)… For the very first time a 3D map of the gas velocities in the studied area has been made. Thanks to the spectroscopy of very high spectral resolution, maps of the speed of the expanding gas bubble have been obtained, resulting in this amazing video:

In short. Everything is going faster than predicted, in every way. The young massive stars determine, much earlier than previously thought, the shape and evolution of the interstellar environment that saw them born, ravaging and cleaning, with their strong stellar winds, the entire region that surrounds them. That means they sweep away the interstellar material needed for the formation of new stars.

For Javier R. Goicoechea, “It is incredible that after more than 400 years observing the great Orion Nebula, we have now been able to understand that the winds coming from the most massive stars blow the surrounding cloud and give it that morphology so recognizable“.

Images

Image 1: Red-green-blue image showing three different velocities of the gas associated with the heart of the Orion cloud. The wind from the most massive stars has created a bubble (in black) and prevents the formation of new stars in its environment. At the same time, the wind sweeps the gas from the edges (in color), creating a shell of thin gas around the bubble and where perhaps a new generation of stars can form. Credits: NASA/SOFIA/Pabst et al.

Image 2: SOFIA (The Stratospheric Observatory for Infrared Astronomy) flying over the California sky. The telescope can be seen inside the open cavity at the rear of the aircraft. Credit: NASA/Jim Ross

Image 3: Javier R. Goicoechea (IFF-CSIC) in full flight and data collection. In the background is Jürgen Stutzki (University of Cologne, Germany), co-Principal Investigator of the GREAT instrument.

More information:

Paper: C. Pabst, R. Higgins, J.R. Goicoechea, D. Teyssier, O. Berne, E. Chambers, M. Wolfire, S. Sury, R. Guesten, J. Stutzki, U.U. Graf, C. Risacher, A.G.G.M. Tielens. Disruption of the Orion Molecular Core 1 by the stellar wind of the massive star Ɵ1 Ori C, Nature. DOI: 10.1038/s41586-018-0844-1.

CSIC Press Release (in Spanish):  Los vientos estelares de las estrellas masivas dan forma a la nebulosa de Orión

Link to the SOFIA press release with 3D videos

Hydrocarbons open bar in Orion

Orion’s skin

New observations of the Orion B nebula reveal the anatomy of a star-forming reservoir

Originally published in Spanish on the Naukas website: Estrella come nube (o «En Orión no está el horno p’a bollos») (2019/01/14).

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Baby, baby, baby, light my way

Yes, may be this reminds you the lyrics of “Ultraviolet”, a song from U2 that fits perfectly with our topic. Let’s sing some astrochemistry.

Image 1: Orion Nebula.

The world of science often says that space is hostile, that it is very difficult to find complex molecules (even if there are). The fact is that one of the culprits of breaking bonds between atoms and leaving everything broken is ultraviolet radiation from stars, and in this case, the distant ultraviolet. But also, like Ying and yang, it may be responsible for liven up certain organic molecules.

Astrochemistry looks for those molecules and study their endurance and how they react. In this particular work, scientists have studied the molecular gas in space that is being strongly irradiated by ultraviolet rays. The team, led by Sara Cuadrado (ICMM-CSIC), has performed (the words in bold are explained below) a complete spectral survey of lines in the millimeter range using the IRAM30m telescope. This spectral survey (a kind of thorough review of that entire range of the electromagnetic spectrum) has been carried out at the edge of the photodissociation region of the Orion Bar, which is being irradiated by a very intense field of distant ultraviolet radiation.

But let us take it one step at a time.

Maybe you already know the Orion Bar from other previous reports: it is located within the well-known Orion Nebula, about 1,300 light years from Earth, and is the closest massive stars formation region.

The energetic far ultraviolet reaches this area of the Orion Bar. This ultraviolet range of light comes from young and massive stars that are forming  nearby (the stars known by the name of the Trapezium) and emit much of their energy in this range of the electromagnetic spectrum. The far ultraviolet is responsible, in this case, for the photodissociation of the molecules.

The photodissociation region is the one in which ultraviolet light is dissociating, that is, separating the atoms of the molecules (although, at the same time, new bonds between atoms may be forming, creating new molecules). The photodissociation region of the Orion Bar is very special because, being “close”, we can study it in detail.

The millimeter range is the range of the electromagnetic spectrum that allows us to study cold areas of the cosmos. For an astronomer a “cold” environment is one in which the temperature does not allow us to observe it because it emits poorly and it is very difficult to detect objects. Infrared and millimeter help us “see” those cold objects. 

Finally, the lines we are talking about are like fingerprints of chemical species. We detect them in space and they are reflected in lines like the ones I show you:

Image 2: Orion Bar Spectrum.

Well, despite the fact that the Orion Bar is a hostile environment where it was only expected to  find very simple molecules, the observations show spectra with many lines (the team has detected more than 850!), of which about 250 correspond to complex organic molecules and related precursors  [1]: methanol, formaldehyde,  formic acid  (the ants one), acetaldehyde, etc.

What does this mean?

La zona de la Barra de Orión sufre el castigo constante de la radiación ultravioleta emitida por estrellas masivas jóvenes del entorno. Por eso se pensaba que no podía haber complejidad química. Pero la hay. Y, aunque se desconocen los procesos por los cuales se forman estas especies descubiertas en el borde de la Barra, se han planteado varios escenarios que explicarían cómo se forman las moléculas orgánicas complejas halladas:

The Orion Bar area suffers the constant punishment of ultraviolet radiation emitted by young massive stars in the environment. That’s why it was thought that there could be no chemical complexity. But there is. And, although the processes by which these species discovered at the edge of the Bar are formed are unknown, several scenarios have been proposed that would explain the formation of the complex organic molecules found:

The first scenario would take into account new chemical reactions that only occur in the hottest gas and that have not yet been included in current theoretical chemistry models that try to reproduce the processes that occur in the interstellar medium.

In the second, complex organic molecules would be produced on the hot surfaces of the nearly bare grains (without ice sheets [2]).

And, in the third scenario, the dynamics of the photodissociation regions (something like currents of motion within the cloud) would cause complex organic molecules or their precursors, which have formed in the icy mantles of dust grains inside the molecular cloud, to sublimate and reach the edge of the Bar.

In short: the presence of complex organic molecules in the interstellar medium is more ubiquitous than initially expected. It includes environments as adverse as gas in the process of colliding at high speeds and, now, gas strongly illuminated by distant ultraviolet radiation. The formation of complex organic molecules reflects the complicated interaction between the chemical processes that occur in the gas phase and on the surface of the dust grains, leaving us with the question of what do all these molecules do in the Bar?

For Sara Cuadrado, “The formation routes of these species are not entirely clear and may not even be the same in different environments. More theoretical studies and laboratory experiments are needed to investigate the different chemical processes that take place on the surface of grains. The next step is, thanks to the new and increasingly powerful telescopes, to study regions similar to the Orion Bar to learn more about the different mechanisms taking place in these chemically surprising regions.”

Going back to the title of this report, you will understand that we sing the chorus of the “Ultraviolet” song from U2, “Baby, baby, baby, light (photodissociate, photoionize and photodesorb) my way”.

Notes:

[1] H2CO, CH3OH, HCO, H2CCO, CH3CHO, H2CS, HCOOH, CH3CN, CH2NH, HNCO, H213 CO, and HC3N (in decreasing order of abundance). The inferred column densities are in the range 1011— 1013 cm-2. The work also provides the upper limit of abundance for some organic molecules that have not been detected in spectral scanning, but are present in other star formation regions: HDCO, CH3O, CH3NC, CH3CCH, CH3OCH3, HCOOCH3, CH3CH2OH, CH3CH2CN, and CH2CHCN.

[2] The desorption of complex organic molecules from the icy mantles that coat the dust grains by the action of UV radiation is one of the main mechanisms of formation of these species in the interstellar medium, a mechanism known as photodesorption. But this process does not occur on the illuminated and warmer edge of the Orion Bar, as the dust grains are no longer coated by ice.

More information:

This work has been published in the paper “Complex organic molecules in strongly UV-irradiated gas”, by S. Cuadrado (Molecular Astrophysics Group, Institute of Materials Science of Madrid –CSIC, Spain); J. R. Goicoechea (Molecular Astrophysics Group, ICMM-CSIC, Spain); J. Cernicharo (Molecular Astrophysics Group, ICMM-CSIC, Spain); A. Fuente (Observatorio Astronómico Nacional – IGN, Spain); J. Pety (Institute of Millimeter Radio Astronomy (IRAM); LERMA, Paris Observatory, CNRS/PSL Research University, France); and B. Third (Molecular Astrophysics Group, ICMM-CSIC, Spain).

IMAGES

Image 1: Orion Nebula: The Orion Nebula, an immense stellar nursery about 1,500 light-years away. This stunning false-color view has been based on infrared data obtained with the Spitzer Space Telescope.  Credits: NASA/JPL-Caltech

Image 2: Orion Bar spectrum: Part of the spectral survey in the Orion Bar photodissociation region obtained with the IRAM-30m radio telescope. Credit: Sara Cuadrado.

Originally published in Spanish on the Naukas website: “¿Qué tiene el ultravioleta que a todas horas…?” (2017/10/23).

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“Gas on the rocks”: shaken, not stirred

Methyl isocyanate in space and in comets

Orion Nebula

One of the translation errors (from English to Spanish) that has caught my attention the most has been that of the expression “on the rocks”. I’ll never forget that Hollywood classic where someone asks another character for a whiskey and says, “Yes, on the rock” (literally, put the glass on the stone rock!) … In Spanish the translation should have been, “Yes, only with ice.” Equally curious is the translation of “Shaken, not stirred” for the Martini, which brings translators crazy, although it seems this expression has been the most used by James Bond. The erroneous expression in Spanish “Sí, sobre la roca” is very useful to talk about not whisky, but gas: the gas that is deposited on the “rock” (whether a grain of dust or a comet) and which, later, may end up being transformed into ice. All very “on the rocks” and very mixed.

Today, detecting new molecular species in space is something relatively normal. It is very complex, because molecules emit in the range of the least energetic electromagnetic spectrum, and that is why very sensitive instruments are necessary. To date, a large number of molecular species have been detected, and about 30% of these detections have been carried out by Spanish research teams.

One of the goals in all astrochemical research is to understand how chemical phenomena take place in space: is it important that a molecule found in a comet is also present in the interstellar environment? How can the mixture of molecular species condition the emergence of life or the future characteristics of a planet? What amounts are needed? Is there any relationship between the chemistry of the primitive Solar System and the current one?

Dense interstellar clouds are the places where stars and planets form. Most of its mass is essentially molecular gas with a small fraction of tiny grains of dust [1].

On the other hand, dust grains usually have a nucleus of silicates on which the molecules of the gas phase are adhering and accumulating, forming ice sheets on the grain. This occurs during the gravitational collapse of the clouds of gas and dust, clouds from which new stars and planetary systems like ours will form, resulting in giant gaseous planets and rocky bodies such as Earth, asteroids and comets.

Our Solar System was formed 4.5 billion years ago from an interstellar cloud of gas and dust and, therefore, the composition of the bodies that emerged from it is closely linked to the composition of the interstellar cloud from which they were born. Thus, it is considered that, for example, the icy surface of comets is a repository of information that tells us about the composition of the gas and dust that was in the primitive solar nebula.

Comet 67P/Churyumov-Gerasimenko and the Orion Cloud

The recent analysis of the composition of the icy surface of comet 67P/Churyumov-Gerasimenko [2] by its lander, Philae, revealed the existence of a significant number of complex organic molecules, most of them already detected in gas phase in interstellar clouds.

But among the species detected on the surface of the comet there was one that had not previously been observed in interstellar clouds: methyl isocyanate (CH3NCO).

Philae detected the molecule with a mass spectrograph, but to detect a molecular species on a comet, techniques other than those used in the interstellar medium are used. In fact, to confirm its presence in the interstellar medium, a thorough analysis had to be performed consisting of obtaining the rotational spectrum of molecules in a molecular spectroscopy laboratory, so that frequencies and lines corresponding to that molecule could be obtained.

After hard laboratory work that began in 2010, an international research team, led by José Cernicharo (from the Molecular Astrophysics Group of the Madrid Institute of Materials Science (ICMM) of the Higher Council for Scientific Research (CSIC)), discovered, in the clouds of Orion, methyl isocyanate. In fact,  from this observation work, carried out with the data obtained with the IRAM 30-meter radio telescope and the ALMA interferometer, 400 lines of this molecule have been characterized and detected.  

This result, together with previous analyses of other comets studied from the ground, has led to the development of important work in the search for a possible connection between interstellar and cometarian molecular abundances.

CH3NCO

Methyl isocyanate (CH3NCO) could play an important prebiotic role in the formation of peptides that could be important in the chemical evolution of primitive Earth. It is known that, at room temperature, methyl isocyanate reacts with water and with many substances containing N-H or O-H groups [3], common in the gas phase in Orion.

Although it is a potentially relevant molecule in the chemistry of the interstellar medium, it had so far not been included in any chemical model and has not been released until now in astrophysical journals. However, as Cernicharo states, “We intuit its presence by similarity to other previously detected species and finally confirm it. To our surprise, it is one of the most abundant molecules with a methyl group and an isocyanate group.”

Orion’s massive star formation region is the prototype of “hotcore”, the most promising areas to search for CH3NCO.  Its most active part is the Kleinmann-Low nebula (Orion-KL) where a group of newborn stars, deeply embedded in the region, interacts with their surrounding material: the fact that it has been detected in hot nuclei and not in dark and cold clouds suggests a chemistry dominated mainly by the activity in the mantle of dust grains. That is, the evaporation of the ice sheets of the dust grains produces a very rich chemistry (when the original gas molecules mix with the ones that arise from that evaporation).

On the other hand, we assume that the frozen surface of comets maintains memory of the composition of the dust grains of the primitive solar nebula. These dust grains, if similar to Orion’s, will expel molecules as soon as they are heated by radiation or impacts with cosmic rays.

It will be of great interest to observe the comet’s coma to learn about the abundances of gas phase species and to obtain information on how molecules that survived the ejection of the comet’s surface have been identified. In addition, laboratory experiments on ice are essential to learn about CH3NCO formation processes on these surfaces. Knowing its original composition will help us to know more about what are the conditions necessary for systems similar to ours to emerge, systems that start being simply “gas on the rocks”.

Laboratory characterization

In 2006, this research team initiated an in-depth survey of lines in Orion KL’s millimeter domain (80-280 GHz) with the IRAM 30m radio telescope with the aim of fully characterizing its chemical composition. However, due to the high kinetic temperature ofthe gas [4], there were many rotational and vibrational levels of abundant species that produced a forest of spectral lines (i.e., there was a huge amount of information “overlapping”, difficult to decipher).

The number of unidentified lines was too large to perform a realistic search for new molecular species. Initially, about 15,000 spectral lines were detected, of which 8,000 were unknown. It was necessary to initiate systematic work in spectroscopic laboratories to characterize all the isotopologues and vibrationally excited states of the most abundant species in Orion-KL in order to identify unknown lines.

Numerous isotopologues and vibrational states were characterized in the laboratory, later identifying them in the data and reducing the number of unidentified lines to 4,000, some of them particularly strong [5].  

Of the expected 523 lines of CH3NCO in the data obtained by the team, 282 are not mixed with others and 119 are partially mixed with other species (without this preventing them from being identified on the line profile). The other 122 lines are completely mixed with lines of other more abundant species, most of them in the 1.3 mm (197-280 GHz) wavelength domain, where the density of lines in Orion grows enormously.

Notes:

[1] The fraction of dust grains is ~1/200. The most abundant molecular species is molecular hydrogen (H2), followed by CO. More than 180 complex molecules are added to this list in different proportions.

[2] The COSAC (Cometary Sampling and Composition) experiment, aboard the Rosetta mission’s Philae lander, has measured in situ the abundances of the main surface components of comet 67P/Churyumov-Gerasimenko.

[3] CH3NCO was responsible for the deaths in the  Bhopal industrial disaster.

[4] TK  ~ 100-300 K

[5] A large number of isotopologues containing 13C, 15N, 18O and vibrationally excited states of species such as CH2CHCN, CH3OCOH, CH3CH2CN, and NH2CHO among others, were fully characterized in the laboratory and identified in the data. New molecules such as ammonium, NH3D+, methyl acetate, CH3COOCH3 and CH3OCH2CH3, methyl ethyl ether, were also detected.

More information:

Paper: “A rigorous detection of interstellar CH3NCO: An important missing species in astrochemical networks”, Astronomy and Astrophysics Journal.

Images:

Orion Nebula in the infrarred. This wide-field view of the Orion Nebula (Messier 42), lying about 1350 light-years from Earth, was taken with the VISTA infrared survey telescope at ESO’s Paranal Observatory in Chile. The new telescope’s huge field of view allows the whole nebula and its surroundings to be imaged in a single picture and its infrared vision also means that it can peer deep into the normally hidden dusty regions and reveal the curious antics of the very active young stars buried there. This image was created from images taken through Z, J and Ks filters in the near-infrared part of the spectrum. The exposure times were ten minutes per filter. The image covers a region of sky about one degree by 1.5 degrees. Credits: ESO/J. Emerson/VISTA. Grading: Cambridge Astronomical Survey Unit.

Video:

Artistic impression that takes us on a 3D journey through the Orion Nebula. Credit: ESO/M. Kornmesser. Original video link:  https://www.eso.org/public/spain/videos/eso1006e/

Originally published in Spanish on the Naukas website: “Gas on the rocks: mezclado, no agitado”(2016/03/08).

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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.

Notes:

[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).

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Orion’s skin

Orion is the nearest and brightest massive stars forming region, a “stellar nursery” that has become our astrophysical experimentation laboratory. It is so close that we can take images of the entire region and, at the same time, study details of it. In this article we will focus on how ultraviolet radiation from stars influences the interstellar clouds of gas and dust that surround them.

The Orion Nebula.

Interstellar clouds are areas of space “among the stars” formed by gas and dust, regions monstrously larger than the clouds of the sky in which, in some lumps “chosen” by gravity, matter can condense and collapse into stars. In particular, the great cloud of Orion is a tremendously active region of the sky. Within it stands out the Trapezium Cluster, a group of massive and very energetic stars surrounded by gases that can be seen from the ground even with small amateur optical telescopes.

Compared to our Sun, massive stars (more than eight solar masses) are huge and have shorter lives because they consume the “fuel” of their core very quickly. They are so energetic that powerful winds emanate from them that “shake” the whole environment, and also emit a lot of “sterilizing” light, especially in the ultraviolet (UV) range of the electromagnetic spectrum.

Massive stars grow so fast that there is no time for the cloud of molecular gas and dust that spawns them to disappear (as with the birth of lower-mass stars like our Sun), so that they destroy (photoevaporate and/or photoerode) the cloud that gave birth to them: they are like children who devour their parents.

For researchers it is very important to determine the impact these massive stars have on the progenitor clouds and also their impact on the whole galaxy, since their birth and existence determine the properties and future of the entire interstellar environment.

The Orion Nebula (annotated).

The main characters

To talk about this research we need to present the main characters, and the first is the aforementioned area of Trapezium, dominated by relatively young and massive stars (up to 30 times the mass of the Sun for the brightest star of Trapezium) and located on the sword of the “hunter” of the Orion’s constellation. The entire region is surrounded by the Orion Nebula, formed by a very hot gas that has been ionized by UV radiation emitted by these stars.

On the other hand we have the molecular cloud that lies just behind the Trapezium and the nebula. In this cloud of molecular gas and dust hundreds of protostars are being “incubated”, colder objects that are not yet “adult” stars but are in the process of formation (you can watch this video to have an idea of the distribution of matter in this area). While we need optical telescopes to capture visible light emitted by hot gas from the nebula, the only way to “cross” the region and see the molecular cloud is to observe it in infrared and radio waves.

And in the outer skin of that molecular cloud, very interesting things are happening. For example, we know that UV photons emitted by Trapezium stars are beginning to “burn” the cloud – starting with the skin – with mechanisms that researchers know well (e.g. ionization of atoms). This causes a bright flash of Orion’s skin in the range of the far infrared. Something like an interstellar “tan”.

We know our third character thanks to the data obtained with the HIFI instrument aboard the Herschel Space Telescope: we have been able to see the “skin of Orion burned” because it emits in the line of ionized carbon (C+), a line that traces how the molecular cloud is being photoevaporated.

Image of the [CII] 158μm emission captured by Herschel.

This C+ emission line, the brightest of the interstellar medium (we’ll call it the “superline”), is a fundamental tool for plotting how UV radiation destroys molecular clouds. It also gives us clues about the rate of stellar formation, a critical parameter in astrophysics to know fundamental details about our universe (how many stars are formed and at what rate?).

In addition, this emission cools interstellar neutral gas: the thermal agitation of the gas becomes, mainly, radiation emitted in the C+ line that escapes from the cloud and cools the medium. Emission is difficult to observe from the ground, so it is necessary to use space satellites or telescopes embarked on stratospheric aircraft to study it. In fact, the team that carried out this research work obtained ten hours of observation with the Herschel Space Telescope, managing to extract from the data and the maps information about the kinematics of the gas in the skin of Orion, thus revealing its three-dimensional structure and then elaborating this impressive video.

Far beyond time and space

The information we extract from this work doesn’t end here. We have a superline that tells us about how clouds are photoevaporated and how many stars are born in a certain environment of stellar formation, such as the Orion region. But what if it was able to tell us about much further areas?

By the redshift effect, which causes light emitted in a range to move to ever longer wavelengths (due to the expansion of the universe), the C+ line emitted from very far galaxies (when the universe was much younger) comes to us in the range of millimeter and submillimeter radio telescopes that astrophysicists build at high altitudes (as is the case with ALMA -Atacama Large Millimeter/submillimeter Array – installed in Chile’s Atacama desert, more than 5,000 meters high).

That means that, if we used to need ten hours with a satellite to observe regions of the Milky Way like Orion, now, in a matter of minutes, with radio telescopes like ALMA, composed of dozens of antennae, we can get the same information from very distant objects (young galaxies) thanks to that redshift of light.

But not only can ALMA offer great advances in detailed study of what happens in the “skin of Orion”. Members of the NANOCOSMOS team [1] participate in a project that has obtained time from the Impact Legacy Program to map the entire Orion region into C+ using the “upGREAT” instrument aboard SOFIA (Stratospheric Observatory for Infrared Astronomy). A NASA telescope “flying” at a height of about 14 km (about 4 km above commercial flights, fasten your seat belts!).

These are 54 hours of flights and observations (usually the programmes granted with SOFIA are one hour or less) that will be carried out over the next two years in order to map a region 20 times the one presented in this study. Astronomers, climbed on an airplane, will work from the stratosphere to learn more about Orion’s (less mysterious) skin in order to understand the mechanisms that produce the emission of C+ and then be able to understand more accurately the emission that ALMA observes from the primitive universe.

Study what we have around to understand what we observe far away. All thanks to Orion’s skin.

Notes

[1] The scientific team that obtained time with SOFIA is led by A. Tielens (Leiden) and includes three members of the NANOCOSMOS project (J. Goicoechea, O. Berné and J. Cernicharo). This project will allow the use of the C+ line to be established as a stellar formation rate indicator, to measure the mass of molecular clouds that cannot be measured with CO (the so-called “CO-dark” gas), and to determine semi-empirically the efficiency of photoelectric heating in PAHs (polycyclic aromatic hydrocarbons) and interstellar powder grains.

Images:

Image 1: The Orion Nebula.  The Orion Nebula seen by Hubble. Credits: NASA, ESA, M. Robberto (STScI/ESA) et al. (Link to image).

Image 2: The Orion Nebula (with annotations). Color composite image of the Orion Nebula (M42) taken in visible light with the Hubble Space Telescope (Robberto et al., 2013). The molecular cloud of Orion, where new protostars develop, lies behind the ionized nebula. Black contours show the emission of C+ in the far infrared detected with Herschel-HIFI, tracing the illuminated skin of the cloud (Goicoechea et al., 2015).

Image 3: Image of the [CII] 158μm emission captured by Herschel, with annotations indicating the location of the best known regions of the Orion cloud. Credits: Goicoechea et al., 2015.

Videos:

Video 1: This video shows ionized carbon emission at different gas speeds. Thanks to the “high spectral resolution” technique, gas movements can be distinguished in detail. This video is analogous to an Orion “scanner” in which, first, the peripheral regions of the Orion Nebula (especially atomic and ionized gas seen in images of visible light) are detected and finishes penetrating into the molecular cloud and dust hidden behind the visible nebula (with gas speeds above 8 km/s). The skin of the cloud (illuminated by UV radiation from the stars of Trapezium) can be seen in the gas that moves at speeds between 8 and 10 km/s. Credits: Goicoechea et al., 2015.

Vídeo 2: Spectacular 3D video of the Hubble Space Telescope inside the Orion Nebula. These stars are in a dramatic landscape of gas and dust reminiscent of the Grand Canyon. The Orion Nebula is an illustrated book about the massive formation of young stars. Credits: NASA, ESA, G. Bacon and the Science Visualization Team (STScI) https://hubblesite.org/contents/media/videos/2006/01/513-Video.html?news=true

Original video and more information: http://hubblesite.org/newscenter/archive/releases/2006/01/video/c/

Originally published in Spanish on the Naukas website: La piel de Orión (2015/12/10).

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Hydrocarbon open bar in Orion

1. The Trapezium in the Orion Nebula

Using the IRAM-30m radio telescope and sophisticated interstellar chemistry models, an ASTROMOL team has studied the composition and spatial distribution of small hydrocarbons in the “Orion Bar”, a clear example of molecular cloud radiated by ultraviolet light

Hydrocarbons are the simplest organic molecules, formed only by hydrogen and carbon. They are one of the main sources of energy in the modern world, as they are part of oil, natural gas, gasoline; they are also found in many materials that we usually use, such as plastics, fibers or paints, and we even walk on them every day as they are the main component of asphalt.

But not only can we find hydrocarbons on our planet: since the 1970s it is known that hydrocarbons are present in much of the interstellar environment, and one of the issues that astrochemistry has been looking to clear since then is how they form and what their chemical behavior is in that environment.

In order to study them, one of the most appropriate environments are Photodissociation Regions (PDRs), transition zones between cold and neutral gas (mostly molecules) protected from ultraviolet radiation, and atomic and ionized gas, illuminated by intense ultraviolet fields mostly coming from massive stars [1].

Photodissociation regions are found in many astrophysical environments and on many spatial scales, from the nuclei of star-forming galaxies to the illuminated surfaces of protoplanetary disks. All of them show a chemistry whose common characteristic is the photodissociation of molecules caused by ultraviolet radiation.

The most spectacular and close example of this type of photodissociation region is the so-called Orion Bar, which is located within the well-known Orion Nebula, located about 1,300 light-years from Earth. The Orion Nebula is one of the most studied astronomical objects of all time: it is an immense cloud of gas and dust lovingly regarded as a stellar nursery, as thousands of stars begin their lives there. It is not the only stellar nursery in the galaxy but, being the closest forming massive stars (more than 8 times the mass of the Sun), it offers us the opportunity to study in detail how the stars are born; how, once formed, they interact with the interstellar environment that surrounds them; and, in particular, how intense stellar ultraviolet radiation fields end up “destroying” (photodissociating) the molecular cloud where they were born.

Ultraviolet radiation that ionizes atoms and dissociates molecules in the Orion Bar comes from the famous set of massive stars in the Trapezium cluster, which takes its name from the asterism that make up its four brightest stars.

Having a chemistry controlled by ultraviolet radiation makes that, in these regions, very peculiar species are produced, such as radicals (C2H, OH, HCO…) and ions (SO+, CO+, CH+, HOC+, etc.). These species do not exist naturally on our planet, as they are extremely reactive and unstable and quickly react with other molecules to form new, more stable compounds. They can only be formed in the laboratory under very specific controlled conditions.

2. Center of the Orion Nebula

The study of the Orion Bar

In order to establish the limits of the chemical complexity of the interstellar environment, and using data obtained with a spectral mapping [2] carried out with the IRAM-30m radio telescope (located in Sierra Nevada, Granada, Spain), an ASTROMOL team has managed to expand our knowledge of which molecules exist in environments radiated by strong fields of ultraviolet radiation and how they form.

Although the Orion Bar is a hostile environment where you would expect only very simple molecules, observations show a spectrum with more than 500 lines coming from the emission of more than 60 different molecules containing 2 to 6 atoms. What is surprising is that approximately 40% of the detected lines belong to hydrocarbons [3]! So, it’s all about making a word game and claiming that we have an area with a hydrocarbon open bar in Orion.

But how do these hydrocarbons form in the interstellar environment and why are they so abundant? Until now, in studies in other regions radiated by less intense ultraviolet radiation fields, such as the famous Horsehead Nebula, or in interstellar diffuse clouds, the results obtained through the analysis of observations did not match the theoretical results obtained from gas phase models [4]. The abundances of hydrocarbon measured in these regions were much greater than those predicted by these models. That is, gas chemistry was not enough to explain these high abundances.

Researchers looked for alternative sources of carbon that might be contributing to the amount of hydrocarbons formed through gas reactions, and thought about polycyclic aromatic hydrocarbons (PAHs). PAHs are powerful environmental pollutants, but they are also present ubiquitously in the universe (see image 2). In these regions, the incidence of radiation on PAHs would completely break down the cyclical structure of these compounds, forming small hydrogen and carbon molecules, and contributing to the amount of hydrocarbons formed by gas phase reactions.

However, the ASTROMOL team has discovered that, to explain the high abundances of hydrocarbons in the Orion Bar, there is no need to resort to the destruction of PAHs (or their contribution is not the dominant one) as Trapezium stars illuminate the region with ultraviolet radiation fields so intense that molecular gas reaches very high temperatures, bringing into action new gas chemical reactions that need very high energies to occur [5].

This takes a step further in understanding the results and details of photodissociation in gas clouds, helping us improve our knowledge of interstellar carbon chemistry and learn more about how chemical complexity in space increases.

3. Hydrocarbon Spectra in the Orion Bar

Notes

[1] Generally, massive OB-type stars, at least 8 times more massive than the Sun and main source of ultraviolet radiation in galaxies like ours.

[2] Spectral maps are one of the most important tools in the field of astrochemistry to study the interstellar medium, as they allow to carry out a complete chemical characterization of the region under study. In this case, spectral lines have been obtained in the millimeter range, one of the lowest energy in the electromagnetic spectrum and whose emission is dominated by low-energy transitions produced by molecules.

[3] C2H, C4H, c-C3H2, c-C3H, C13CH, 13CCH, l-C3H, l-C3H+ and l-H2C in decreasing order of abundance.

[4] These models attempt to computationally simulate the physical and chemical conditions of interstellar clouds, simulating hundreds of chemical reactions and processes that occur in different regions.

[5] Endothermal reactions (or with barriers, i.e. those that only occur from certain temperatures) in gas phase between C+, radicals and H2, can dominate chemistry and promote the formation of hydrocarbons. However, photodissociation of PAHs, hydrogenated amorphous carbons (HACs) and very small grains (VSGs) may be required, as well as a greater knowledge of surface chemistry in carbonous grains to explain the abundances of the most complex hydrocarbons.

More information

This work has been published in the scientific paper “The chemistry and spatial distribution of small hydrocarbons in UV-irradiated molecular clouds: the Orion Bar PDR”, and the authors are S. Cuadrado (Molecular Astrophysics Group of the Institute of Materials Science of Madrid (ICMM, CSIC); Astrobiology Center (CAB/CSIC-INTA), Spain; J. R. Goicoechea (Molecular Astrophysics Group of the ICMM-CSIC; CAB/CSIC-INTA, Spain); P. Pilleri (Université Toulouse III – Paul Sabatier, UPS- Observatoire Midi-Pyrénées, OMP – Institut de Recherche en Astrophysique et Planétologie, IRAP); Centre national de la recherche scientifique, CNRS – IRAP, France);  J. Cernicharo (Molecular Astrophysics Group of the ICMM-CSIC; CAB/CSIC-INTA, Spain); A. Fuente (National Astronomical Observatory, OAN-IGN, Spain); and C. Joblin (Université de Toulouse UPS-OMP, IRAP; CNRS, IRAP, France). 

Links

Images:

1. The Trapezium in the Orion Nebula.

At the center of this image, surrounded by dust and gas, we see the intense brightness of the stars that make up the Trapezium, the four most massive stars of the Orion Nebula. The ultraviolet radiation they emit alters the chemistry of their entire environment. http://hubblesite.org/newscenter/archive/releases/2006/01/image/e/

Credits: NASA,ESA, M. Robberto (Space Telescope Science Institute/ESA) and the Hubble Space Telescope Orion Treasury Project Team.

2. Center of the Orion Nebula

Image of the center of Orion Nebula in the infrared (at 8 microns) taken by the IRAC camera aboard the Spitzer Space Telescope (data from NASA/Spitzer’s public file: http://archive.spitzer.caltech.edu). At these wavelengths the emission is dominated by polycyclic aromatic hydrocarbons (PAHs). It also shows the position of the Trapezium Cluster (marked with stars) and the region studied in this work (the green box). Credits: NASA/Spitzer; Javier R. Goicoechea

3. Hydrocarbon Spectra in the Orion Bar

Spectra of the Orion Bar at 85 GHz. Three lines (rotational transitions) of two different hydrocarbons (C4H and C3H2) and a hydrogen recombination line from the atomic and ionized gas region (HII region) can be observed.

Originally published in Spanish on the Naukas website: Barra libre de hidrocarburos en Orión (2015/03/11).