Infrared images of the Large Magellanic Cloud - AKARI nears completion of first all sky survey

As the AKARI satellite nears completion of its All Sky Survey, it has released two stunning images of the Large Magellanic Cloud (LMC). AKARI is an infrared astronomical satellite from the Japan Aerospace Exploration Agency (JAXA) with involvement from the UK, the Netherlands and the European Space Agency.

Professor Glenn White of the CCLRC Rutherford Appleton Laboratory / Open University said,"This stunning AKARI image traces the far-infrared emission from a noticeable bar of stars, some of which, including S Doradus, are extremely luminous. The Large Magellanic Cloud is rich in a variety of diffuse nebulae, including the spectacular Tarantula Nebula, planetary nebulae, open clusters, and globular clusters, which suggest that it has experienced early and late bursts of star formation."

The Large Magellanic Cloud is a dwarf galaxy orbiting our own galaxy. It lies at a distance of about 160,000 light years, having about 1/20 the diameter of our galaxy and 1/10 the number of stars. It is believed that the LMC was once a barred spiral galaxy that was disrupted by the Milky Way to become somewhat irregular. AKARI provides a superb view of the Large Magellanic Cloud - which is being consumed by our own galaxy. All galaxies cannibalize each other; in time, our own galaxy will be subsumed within the Andromeda galaxy.

AKARI (formerly known as ASTRO-F) was launched in February 2006 and began its All Sky Survey in May. It is the first new infrared survey satellite since the 1980s and the data it collects will shed new light on the dusty Universe - such as areas where stars are born and die.

During the survey observations, AKARI investigated one of the most important targets for studies of the formation of galaxies, the Large Magellanic Cloud, over more wavelength bands than has ever been possible in the past. Using the data taken by AKARI astronomers will be able to unlock the secrets of how both the Large Magellanic Cloud and our own Galaxy have formed and have grown to their current state.

Since most stars are formed deep in dusty clouds of interstellar gas, their starlight is not directly visible in the optical, but light from the young stars heats the surrounding dust, which in turn radiates at infrared wavelengths that can escape the dusty clouds. However, if dust is very widespread and thick throughout galaxies, the stars which heat the surrounding dust may not be just the young stars, so the observed infrared radiation would not be the good measure of star formation rates that it is usually assumed to be. Clarifying the dust content of typical galaxies is important to understanding how they evolve over time, as interstellar gas is transformed into stars. These AKARI far infrared surveyor observations are designed to trace the distribution of warm dust close to hot stars, and the associated star-formation rate. Understanding this in one of the Local Group galaxies in our own backyard is crucial to our understanding of the formation and evolution of more distant galaxies.

Notes for editors

The Large Magellanic Cloud

The Large Magellanic Cloud is a dwarf galaxy orbiting our own galaxy. It lies at a distance of about 160,000 light years, having about 1/20 the diameter of our galaxy and 1/10 the number of stars. It is believed that the LMC was once a barred spiral galaxy that was disrupted by the Milky Way to become somewhat irregular. The Large Magellanic Cloud is located in the constellation Dorados in the southern sky.

Further information is available on the UK AKARI project website:http://astrof.open.ac.uk/

The images

The far-infrared image by AKARI reveals that the interstellar clouds cover the entire galaxy in contrast to the stellar distribution which dominates in optical (visible light) images.

Figure 1 is taken in the long-wavelength far-infrared light and reveals the dust and gas (interstellar matter) distribution over the entire galaxy. Dust grains in these interstellar clouds are heated by the light from newly born stars, and subsequently re-radiate this energy as infrared light. The infrared emission indicates that many stars are currently being formed. Such copious star formation activity over the whole galaxy is called a "star burst". The nature of the Large Magellanic Cloud is further revealed by the contrasting structure of the interstellar matter forming the disk-like structure and the stars that are distributed in the "spindle" shape in the lower half of the image. These images show that the two components are clearly displaced from one another. Astronomers believe that the observed active star formation and the displacement of these two components in the Large Magellanic Cloud were both triggered by the gravitational force from our own Milky Way Galaxy.

Figure 2 shows a close-up of part of the Large Magellanic Cloud at shorter near- and mid-infrared wavelengths. In contrast, this image shows many old stars in addition to the interstellar clouds. This image enables us to study the processes of how stars recycle and return their component gas into the interstellar medium at the end of their lives.

Participating institutes

The AKARI Project is carried out with the participation of mainly the following institutes: Nagoya University, The University of Tokyo, National Astronomical Observatory Japan, European Space Agency (ESA), Imperial College London, University of Sussex, The Open University (UK), University of Groningen / SRON (The Netherlands), Seoul National University (Korea).

The far-infrared detectors were developed under collaboration with The National Institute of Information and Communications Technology.

The Council for the Central Laboratory of the Research Councils (CCLRC) is one of eight UK research councils and is one of Europe's largest multidisciplinary research organisations supporting scientists and engineers across the world. It operates world-class large scale research facilities, provides strategic advice to the government on their development and manages international research projects in support of a broad cross-section of the UK research community.

For more information please contact:

Natalie Bealing
or
Professor Glenn White, g.j.white@open.ac.uk

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