The collect and collapse process: a way of triggering the formation of massive stars.
In an upcoming issue, the journal Astronomy & Astrophysics will publish the most complete picture of a “triggered” star-forming region. Induced (or “triggered”) star formation is one of the processes that are supposed to lead to the formation of massive stars. Massive stars play a key role in the chemical and dynamical evolution of galaxies. The way massive stars form is still much debated among the astronomers’ community: it is currently one of the hottest astrophysical topics. Do they form by accretion as low-mass stars do or do they need the environment of a dense cluster to form through the merging of low mass protostars?
In this framework, the team led by Annie Zavagno and Lise Deharveng (from the Laboratoire d’Astrophysique de Marseille, France) selected regions where several generations of massive stars are likely to be formed. Stars more massive than 8 solar masses, once formed, emit intense UV photons that ionize the surrounding gas. The region filled with ionized hydrogen is called an HII region. Theory suggests that the expansion of the HII region can trigger massive star formation: after the HII region has formed, it expands continuously because the temperature inside the region is much higher than in the cold environment that surrounds it. During the expansion, a dense layer of gas and dust is collected around the HII region, after which gravitational instabilities in the layer cause it to fragment into dense clumps, which then go on to collapse into new stars. The fragments are massive and thus form massive objects (stars or clusters). The successive steps of this process, called collect and collapse process, are shown in Figure 1.
To characterize this process, the team selected the Galactic HII region RCW 79, located 14000 light-years from the Earth. They combined observational data obtained at different wavelengths, as well as from various origins (space, ground-based telescopes, and archived observations), to probe different parts of the region, as illustrated in Figure 2.
Jennifer Martin | alfa
The Fraunhofer IAF is a »Landmark in the Land of Ideas«
15.06.2018 | Fraunhofer-Institut für Angewandte Festkörperphysik IAF
Delft scientists make first 'on demand' entanglement link
14.06.2018 | Delft University of Technology
Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.
Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...
The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.
Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.
An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.
Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...
Light detection and control lies at the heart of many modern device applications, such as smartphone cameras. Using graphene as a light-sensitive material for...
Water molecules exist in two different forms with almost identical physical properties. For the first time, researchers have succeeded in separating the two forms to show that they can exhibit different chemical reactivities. These results were reported by researchers from the University of Basel and their colleagues in Hamburg in the scientific journal Nature Communications.
From a chemical perspective, water is a molecule in which a single oxygen atom is linked to two hydrogen atoms. It is less well known that water exists in two...
13.06.2018 | Event News
08.06.2018 | Event News
05.06.2018 | Event News
15.06.2018 | Materials Sciences
15.06.2018 | Ecology, The Environment and Conservation
15.06.2018 | Power and Electrical Engineering