Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Hydrocarbons in the Horsehead mane

22.02.2005


Observing the edge of the famous Horsehead Nebula with the IRAM interferometer located on the Plateau de Bures (France), a team of French and Spanish astronomers discovered a large quantity of small hydrocarbon molecules. This is a surprise because the intense UV radiation illuminating the Nebula should destroy the small hydrocarbons near the edge. The astronomers suggest that these molecules might result from the fragmentation of giant molecules, called “polycyclic aromatic hydrocarbons” (PAHs).



More than 120 molecules have been observed in the interstellar medium, of which about twenty are small hydrocarbons. These hydrocarbons are an important component of the interstellar chemistry as they furnish a carbon skeleton needed to build more complex molecules. However, these small hydrocarbons are easily broken apart by the UV radiation from young stars. Therefore, astronomers try to understand how these molecules are regenerated in spite of their destruction by UV radiation.

In addition to these small hydrocarbons, giant molecules, called polycyclic aromatic hydrocarbons (PAHs), were detected in the early 1980’s, at infrared wavelengths. PAHs are aggregates made of tens to hundreds of mainly carbon and hydrogen atoms. Previous theoretical studies suggested that radiative fragmentation of the PAHs lead to small hydrocarbons. Jérôme Pety (IRAM, France) and his colleagues [1] have now provided one major step toward validating this theoretical hypothesis. They observed the famous Horsehead Nebula with the IRAM Interferometer (Plateau de Bures, France) [2], to search for hydrocarbons and to compare their location with that of PAHs detected a few years ago with the ISO satellite in the same region.


The Horsehead Nebula is one of the most famous and easily-recognizable shapes in the sky. In addition, for astronomers, its light-bathed silhouette is above all a fantastic interstellar chemistry laboratory where high density gas and stellar light interact. More precisely, the Horsehead appears as a dark patch against a bright region (named IC 434). It also undergoes strong ultraviolet radiation that mainly comes from the nearby star σ Orionis. Thanks to the high spatial resolution of the IRAM interferometer, the team was able to explore the edge of the nebula, “the horse mane”, where the gas density increases and the temperature and illumination decrease within a few hundredths of a light-year.

The team discovered three small hydrocarbons (C2H, C3H2, C4H) in the illuminated edge of the nebula. The abundance of these molecules is close to that measured inside interstellar dark clouds. The team was very surprised by the high abundance of C2H, C3H2, C4H in the Horsehead “mane”: these molecules should be destroyed by the intense UV radiation in the edge of the nebula.

Where do the hydrocarbons come from? In their article, Jérôme Pety and his colleagues compare the places where the hydrocarbons have been detected to the places where the ISO satellite detected PAHs. The correspondence between the hydrocarbons’ and the PAHs’ sites is very good and confirms the hypothesis that the hydrocarbons come from the fragmentation of PAHs. Under strong interstellar radiation, PAHs might be eroded and free a large number of small hydrocarbons. This mechanism would be more efficient in regions similar to the edge of the Horsehead Nebula, named “photo-dissociation regions”, in which UV radiation is stronger. This scenario now has to be confirmed by laboratory experiments, such as the experimental set-up PIRENEA in Toulouse (France) [3], for the study of the chemical reactions in the interstellar medium.

Jennifer Martin | alfa
Further information:
http://www.edpsciences.org

More articles from Physics and Astronomy:

nachricht New NASA study improves search for habitable worlds
20.10.2017 | NASA/Goddard Space Flight Center

nachricht Physics boosts artificial intelligence methods
19.10.2017 | California Institute of Technology

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>