Carbon grains around evolved stars

The Nanocosmos team published in October 21, 2019, at Nature Astronomy, the results of a set of laboratory experiments showing that gas-phase chemistry, under conditions similar to those of a red giant star environment, can produce very efficiently small amorphous carbon grains and carbon chains similar to those found in oil.

Stardust, an ultra-high vacuum machine built in the ERC Nanocosmos project (a Synergy project funded by the European Research Council), was specifically conceived to simulate, with a high level of control, the complex conditions of stardust formation and processing in the environment of evolved stars. In addition, the AROMA setup was built to analyse the molecular content of the samples synthesized by Stardust.

In the words of José Ángel Martín-Gago (Institute of Materials Science of Madrid, ICMM-CSIC, Spain), responsible for the Stardust instrument, “Mimicking the conditions of the envelope of an evolved star, laboratory experiments allow scientists to follow, step by step, the formation process of dust grains, from atoms to simple molecules and their growth to more complex clusters of molecules.”

For José Cernicharo (Institute of Fundamental Physics, IFF-CSIC, Spain), lead co-investigator of the project together with Martín-Gago and Christine Joblin (Institut de Recherche en Astrophysique et Planétologie, IRAP-CNRS, France), “That process is important because those grains of dust, which emerge from the final stages of the evolution of medium-sized stars like our Sun will provide the fundamental pieces needed for the birth of the planets and the main ingredients for the onset of life once injected into the interstellar medium.”

This is why it is essential to develop experiments combining laboratory astrophysics, surface science and astronomical observations to unveil the chemical routes that operate in the inner layers of the envelope of evolved stars.

The results obtained show the formation of amorphous carbon nanograins and aliphatic carbon clusters with traces of aromatic species and no fullerenes. This shows that the latter species cannot form effectively by gas-phase condensation at these temperatures in the zone of the evolved star where the dust is formed, a region that extends up to a few stellar radii.

Chemical complexity

Carbon dust analogues were produced in Stardust and analysed with several characterization techniques including Scanning Tunneling Microscopy and mass spectrometry with the AROMA setup. To produce them only gas carbon atoms and molecular hydrogen were used in a ratio close to that in the atmospheres of AGB stars.

The results showed two types of products: amorphous carbonaceous nanograins – the most abundant, considered to be the main component of carbonaceous star dust – and aliphatic carbon groups. But almost no aromatic molecules were found in the analysis.

According to Joblin, “Polycyclic aromatic hydrocarbons (PAHs) are widespread in massive star-forming regions and in carbon-rich protoplanetary and planetary nebulae. Large carbonaceous molecules like buckminsterfullerene C60 have also been detected in some of these environments. But it seems that they need different conditions to be formed”.

One possible pathway could be through thermal processing of aliphatic material on the surface of dust, which could take place as a result of the significant rise in the temperature of nanograins that occurs in highly UV-irradiated environments. Those results give us new insights into the chemistry of carbonaceous stardust seed formation and foster new observations in order to constrain the physical and chemical conditions in the inner shells of the envelops of evolved stars.

About the ERC

The European Research Council, set up by the European Union in 2007, is the premier European funding organisation for excellent frontier research. Every year it selects and funds the very best, creative researchers of any nationality and age to run projects based in Europe. The ERC has three grant schemes for individual principal investigators – Starting Grants, Consolidator Grants, and Advanced Grants – and Synergy Grants for small groups of excellent researchers.

To date, the ERC has funded more than 9,000 top researchers at various stages of their careers, and over 50,000 postdoctoral fellows, PhD students and other staff working in their research teams. The ERC strives to attract top researchers from anywhere in the world to come to Europe.

The ERC is led by an independent governing body, the Scientific Council. The ERC current President is Professor Jean-Pierre Bourguignon. The ERC has an annual budget of €2 billion for the year 2019. The overall ERC budget from 2014 to 2020 is more than €13 billion, as part of the Horizon 2020 programme, for which European Commissioner for Research, Innovation and Science Carlos Moedas is currently responsible.

Kick-off meeting

A two-day meeting (May 5 and 6, 2015) will be held at the Spain National Research Council (CSIC) headquarters in Madrid. This meeting will be focused in well targetted presentations to put forward the main goals of the project and to foster further team discussions and brainstorming. The meeting will be divided into 4 sessions covering the following topics:

  • May 5 (09:30 to 10:30) General overview of the project
  • May 5 (10:30 to 13:00) Dust formation (observations, spectroscopy, chemical modelling and nucleation)
  • May 5 (15:00 to 17:30) Dust analysis (analogs, experimental techniques)
  • May 6 (09:00 to 13:30) Dust spectroscopy (astrophysical conditions) and processes (photo/thermo-processing, gas-grain interactions)
  • May 6 (15:00 to 17:00) Technical session (engineering, vacuum)
  • May 6 (17:30 to 18:30) Summary of the PIs

The final program will be posted here when available.

Meeting place and travel

The meeting will take place at the CSIC Press Room in C/ Serrano 113 (Building 113). See both the general map around CSIC and map of CSIC headquarters. See also an underground (“Metro”) map or visit this link to consult the Madrid metro in different formats.

CSIC headquarters is pretty near both from the República Argentina (line 6) and Gregorio Marañón (line 7) metro stations. The Nuevos Ministerios metro station, which connects to all the airport terminals, is 1.5 km away. These items can be checked at the general map around CSIC above.

Metro fares can be consulted here

If you consider to take a taxi from/to the airport, please visit this site. Official taxi fares can also be consulted here.

Recommended hotels
Both the NH Breton Hotel and the NH Madrid Zurbano Hotel are located pretty near from the CSIC headquarters (1 km away). Prices for a single room are around 80 euros per night.

Stardust machine

New article featuring the Stardust machine and the AROMA setup! (see below, October 2019)

The Stardust machine
 The Stardust machine

Relevant publications

Prevalence of non-aromatic carbonaceous molecules in the inner regions of circumstellar envelopes (L. Martínez, G. Santoro, P. Merino, M. Accolla, K. Lauwaet, J. Sobrado, H. Sabbah, R. J. Peláez, V. J. Herrero, I. Tanarro, M. Agúndez, A. Martín-Jimenez, R. Otero, G. J. Ellis, C. Joblin, J. Cernicharo & J. A. Martín-Gago). Nature Astronomy, 2019 October 21.

More relevant information on this frontier research:

Check our post on this research:


Precisely controlled fabrication, manipulation and in-situ analysis of Cu based nanoparticles (L. Martínez, K. Lauwaet, G. Santoro, J. M. Sobrado, R. J. Peláez, V. J. Herrero, I. Tanarro, G. J. Ellis, J. Cernicharo, C. Joblin, Y. Huttel, and J. A. Martín-Gago). Scientific Reports 8, 7250 (13pp), 2018 May 8.

More information on the Stardust experimental set-up can be found here

 The Stardust machine has been designed and assembled at the Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC). The elapsed time has been from October 2014 to the end of 2015. Throughout 2016, we entered into the commissioning phase with several ongoing verification experiments and processes. The article shown above is the result of this commissioning phase. From mid-2017, we are dealing with the first astrophysical experiments, the so-called exploitation phase.

The Stardust machine is basically a forefront facility to produce and analyze in-situ highly-controlled analogs of the dust grains in a versatile ultra-high-vacuum experiment (up to pressures of 10-11 mbar) to reproduce the physical conditions that prevail in the photospheres of AGB stars. In this environment, the nucleation of the aggregates and their possible interaction with the circumstellar gases will be mimicked. The Stardust machine will characterize microscopic processes (interaction with photons and gas) through surface science techniques. It encompasses 5 independent vacuum chambers, with their own instrumentation, pumping systems, gas-dosed systems in a highly-controlled ultra-high vacuum (UHV) environment:

  • MICS (Multiple Ion Cluster Source) chamber. The MICS is a new optimized route for cluster growth of a standard technique based on a sputtering gas. It allows the formation of nanoparticles of controlled elemental composition by atomic aggregation. A special port has been adapted to perform optical spectroscopy.
  • NEON (NEutral to iON) chamber that separates neutral from ionized nanoparticles as well as a mass selection. It also accelerates, simulating the radiation pressure, and anneals the formed clusters.
  • INTERACTION chamber. Interaction and chemical reactions are induced between the generated nanoparticles and molecules in the gas phase (H2, CH4, C2H2, etc).
  • INFRA chamber. In-flight analysis is performed through UV, visible, near-mid and far-infrared spectroscopy. It is expected that microwave spectroscopy will be performed with the new HEMT receivers (developed in CNIG/IGN) that will provide the opportunity to study second/minute time-dependent changes in the gas composition using these extremely sensitive radio astronomical receivers. A cryostat and a sample manipulator were acquired in order to study ice interstellar analogs.
  • ANA chamber, the analysis chamber. This allows us to collect the nanoparticles and perform X-ray photoelectron spectroscopy (XPS), thermal desorption spectroscopy (TDS), Auger electron spectroscopy (AES) and Ultraviolet photoelectron spectroscopy (UPS) in-situ. Also some in-situ processing can be performed here. The collected samples are duly transported and delivered to the AROMA setup for ulterior analysis.

In summary, the Stardust machine combines different techniques to achieve original studies on individual nanoparticles, their processing to produce complex molecules, the chemical evolution of their precursors and their reactivity with abundant astronomical molecules. The simulation chambers are equipped with state-of-the-art in situ and ex situ diagnostics.

 

The project

idea

Cosmic dust is made in evolved stars. However, the processes involved in the formation and evolution of dust remain so far unknown. NANOCOSMOS will take advantage of the new observational capabilities (increased angular resolution) of the Atacama Large Millimeter/submillimeter Array (ALMA) to unveil the physical and chemical conditions in the dust formation zone of evolved stars. These observations in combination with novel top-level ultra-high vacuum experiments and astrophysical modelling will provide a cutting-edge view of cosmic dust.