Du C60 et du C70 dans l'espace !

[Vincent Boudon]

Le télescope spatial Spitzer de la NASA a découvert les plus grosses molécules jamais trouvées dans l'espace : les fullerènes C60 et C70 ! Et ce, dans la nébuleuse planétaire Tc 1.

Alan Buis 818-354-0474/ Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
Alan.buis@jpl.nasa.gov / Whitney.Clavin@jpl.nasa.gov

J.D. Harrington 202-358-5241
NASA Headquarters, Washington
j.d.harrington@nasa.gov

News release: 2010-243 July 22, 2010

NASA Telescope Finds Elusive Buckyballs in Space for First Time

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?r ... e_2010-243

PASADENA, Calif. - Astronomers using NASA's Spitzer Space Telescope have discovered carbon molecules, known as "buckyballs," in space for the first time. Buckyballs are soccer-ball-shaped molecules that were first observed in a laboratory 25 years ago.

They are named for their resemblance to architect Buckminster Fuller's geodesic domes, which have interlocking circles on the surface of a partial sphere. Buckyballs were thought to float around in space, but had escaped detection until now.

"We found what are now the largest molecules known to exist in space," said astronomer Jan Cami of the University of Western Ontario, Canada, and the SETI Institute in Mountain View, Calif. "We are particularly excited because they have unique properties that make them important players for all sorts of physical and chemical processes going on in space." Cami has authored a paper about the discovery that will appear online Thursday in the journal Science.

Buckyballs are made of 60 carbon atoms arranged in three-dimensional, spherical structures. Their alternating patterns of hexagons and pentagons match a typical black-and-white soccer ball. The research team also found the more elongated relative of buckyballs, known as C70, for the first time in space. These molecules consist of 70 carbon atoms and are shaped more like an oval rugby ball. Both types of molecules belong to a class known officially as buckminsterfullerenes, or fullerenes.

The Cami team unexpectedly found the carbon balls in a planetary nebula named Tc 1. Planetary nebulas are the remains of stars, like the sun, that shed their outer layers of gas and dust as they age. A compact, hot star, or white dwarf, at the center of the nebula illuminates and heats these clouds of material that has been shed.

The buckyballs were found in these clouds, perhaps reflecting a short stage in the star's life, when it sloughs off a puff of material rich in carbon. The astronomers used Spitzer's spectroscopy instrument to analyze infrared light from the planetary nebula and see the spectral signatures of the buckyballs. These molecules are approximately room temperature -- the ideal temperature to give off distinct patterns of infrared light that Spitzer can detect. According to Cami, Spitzer looked at the right place at the right time. A century from now, the buckyballs might be too cool to be detected.

The data from Spitzer were compared with data from laboratory measurements of the same molecules and showed a perfect match.

"We did not plan for this discovery," Cami said. "But when we saw these whopping spectral signatures, we knew immediately that we were looking at one of the most sought-after molecules."

In 1970, Japanese professor Eiji Osawa predicted the existence of buckyballs, but they were not observed until lab experiments in 1985. Researchers simulated conditions in the atmospheres of aging, carbon-rich giant stars, in which chains of carbon had been detected. Surprisingly, these experiments resulted in the formation of large quantities of buckminsterfullerenes. The molecules have since been found on Earth in candle soot, layers of rock and meteorites.

The study of fullerenes and their relatives has grown into a busy field of research because of the molecules' unique strength and exceptional chemical and physical properties. Among the potential applications are armor, drug delivery and superconducting technologies.

Sir Harry Kroto, who shared the 1996 Nobel Prize in chemistry with Bob Curl and Rick Smalley for the discovery of buckyballs, said, "This most exciting breakthrough provides convincing evidence that the buckyball has, as I long suspected, existed since time immemorial in the dark recesses of our galaxy."

Previous searches for buckyballs in space, in particular around carbon-rich stars, proved unsuccessful. A promising case for their presence in the tenuous clouds between the stars was presented 15 years ago, using observations at optical wavelengths. That finding is awaiting confirmation from laboratory data. More recently, another Spitzer team reported evidence for buckyballs in a different type of object, but the spectral signatures they observed were partly contaminated by other chemical substances.

For more information about Spitzer, visit: http://www.nasa.gov/spitzer .

JPL is managed for NASA by the California Institute of Technology in Pasadena.

[Vincent Boudon]

Au fait, ça ressemble à ça, C60 !

C60.gif (2.69 Kio) Consulté 2868 fois

[Dom...]

Les plus grosses quoi, Vincent ?

[Vincent Boudon]

Molécules, Dom

La suite :

http://www.jpl.nasa.gov/news/news.cfm?r ... l&rst=2679

Le spectre (image à droite) est effectivement sans ambiguïté.

[JxArnaud]

Je ne comprend pas trop le dernier paragraphe. C'est quoi ces "tenuous clouds between the stars"?
S'ils l'avaient découvert il y a 15 ans pourquoi les laboratoires n'ont toujours pas confirmé les résultats?

[Vincent Boudon]

Pour moi, cela veut dire que jusqu'à présent, ils n'avaient pas trouvé la bonne cible, avec une signature spectrale claire.

[Eric Chariot]

Ooooh, un C60, ça ressemble à une liste cristal en 3D !

[Vincent Boudon]

Heu ... oui

Et aussi à un ballon de foot (les anciens, pentagones noirs et hexagones blancs) ...

[Emile Touron]

Ou tu les trouve, tes schématisations de molécules ?!

La C70 et ta CH4 sont pareilles (au niveau graphique hein !)


Et comment ça se fait qu'un atome de carbone peut-être aussi gros ? D'habitude c'est du C12 ou C14...

[Vincent Boudon]

Ouh là !!! Emile, tu me mélanges atomes et molécules.

D'abord, il faut faire attention où tu mets les nombres ! 12C, 13C, 14C, ça ce sont les isotopes de l'atome de carbone (le nombre de neutrons du noyau n'est pas le même, mais c'est le même élément chimique). Et ces atomes ont tous la même taille. 12C est de très loin l'isotope le plus abondant.

Après, C60, c'est une molécule, avec 60 atomes de carbone. Donc ça, c'est gros. C60 et C70 sont des molécules de la famille des fullerènes.

Quant aux molécules en 3D, c'est fait avec Rasmol, un logiciel pour linux (tu vas trouver ça !). En fait, Rasmol permet d'afficher des fichiers .pdb de description de molécules. On en trouve plein. Tu cherches dans google, par exemple C60.pdb, CH4.pdb, ADN.pdb, etc.