RAS PN 07/38: AKARI Maps Warm Universe in Exquisite Detail
ROYAL ASTRONOMICAL SOCIETY PRESS INFORMATION NOTE
WEDNESDAY 11 JULY 2007
Ref.: PN 07/38
Issued by RAS Press Officer:
Dr Robert Massey
Tel: +44 (0)20 7734 4582
Mobile: +44 (0)794 124 8035
RAS Web: http://www.ras.org.uk/
RAS PN 07/38: AKARI MAPS WARM UNIVERSE IN EXQUISITE DETAIL
A team of Japanese and European astronomers have mapped the whole sky at infrared wavelengths for the first time in two decades. The new map, produced using the AKARI surveyor is far sharper than its most recent predecessor, completed by the IRAS satellite back in 1984.
Team member Dr Chris Pearson from the Japan Aerospace Exploration Agency (JAXA) and European Space Agency presented the results at this week’s ‘From IRAS to Herschel and Planck’ conference at the Geological Society in London. The meeting is being held to celebrate the 65th birthday of Royal Astronomical Society President Professor Michael Rowan-Robinson.
The AKARI satellite uses a telescope with a 68.5-cm diameter mirror to detect radiation at near-, mid- and far-infrared wavelengths. Many of the cooler objects in the Universe emit infrared radiation that penetrates dust and gas much more readily than visible light, so telescopes like AKARI are able to image objects like forming stars and the centres of galaxies.
AKARI was launched on 21 February 2006 from the Uchinoura Space Center in southern Japan. On current projections, the liquid helium it uses to keep the detectors cold will last until at least 9 September 2007, giving the primary mission a lifetime of about 550 days. Scientists may then extend its life using mechanical coolers to allow observation of sources emitting near-infrared radiation to continue.
The new high-resolution map is assembled from thousands of different images made as the AKARI satellite orbited the Earth gradually scanning the entire sky. One of the released images shows the whole sky as seen by AKARI, with the plane of our Galaxy (the Milky Way) visible as a bright stripe running from left to right. The bright region in the centre of the image is the material surrounding the galactic centre, thought to harbour a giant black hole.
At the lower right of the all-sky image is the Large Magellanic Cloud, a small galaxy that orbits the Milky Way at a distance of about 160,000 light years (or 1.5 million million million km). AKARI images clearly show the regions in this and the other galaxies where stars are forming at a vigorous pace.
Another set of figures shows the region of the sky in the direction of the constellation of Orion, familiar to northern hemisphere observers in the winter months. One image is made with visible light whilst the other image shows the same region depicted using the far-infrared emission detected by AKARI. In both images star-forming regions like the Orion, Rosette and Horsehead nebulae (clouds of gas and dust) are clearly visible. The infrared light from young stars in each nebula heats up their surroundings so much that these regions dominate the AKARI image. At the top right a giant circle of gas is all that remains of a series of explosions that took place when some of the most massive stars ended their lives, sweeping away the surrounding dust and gas.
A fourth image shows the far-infrared view of the constellation of Cygnus, a part of the sky best seen in the northern summer. Bright spots mark other regions of star formation, alongside dark voids cleared by the winds from nearby massive stars. The Milky Way runs from top left to bottom right.
Chris Pearson commented on the new images, “The first comprehensive result from the AKARI mission’s All-Sky Survey is an astoundingly beautiful map of the entire sky. With this image we can see in explicit detail the structure of our own galaxy and the Universe beyond. We are now looking forward to the next images that will show the sky at longer infrared wavelengths.”
Open University scientist and collaborator Dr Stephen Serjeant added, “I'm delighted with this beautiful image of the whole sky. The images of Orion show how strikingly different the sky looks in infrared light. This is our first step towards a comprehensive map of the birth of stars and galaxies in the Universe.”
AKARI will continue to scan the sky at six independent wavelengths until the expiration of the on-board 170 litres of liquid helium, all the while gradually building up a multi-colour map of the entire sky. From these observations, detailed catalogues will be created with the aim of providing a complete census of the local infrared Universe. These catalogues will eventually be released to the global astronomical community. After the helium has expired AKARI will still have the use of its near-infrared cameras in the final phase of the mission that will last for a further year.
Dr Chris Pearson
ESA Support Astronomer for AKARI
Department of Infrared Astrophysics, Institute of Space and Astronautical Science,
Japan Aerospace Exploration Agency,
E-mail: cpp at ir.isas.jaxa.jp
Dr Stephen Serjeant, Senior Lecturer
Room N1070, Venables Building
Department of Physics
The Open University, Milton Keynes
E-mail: s.serjeant at open.ac.uk
Tel: +44 (0)1908 652724
Fax: +44 (0)1908 654192
A description of and news from the AKARI observatory can be found on these three sites
AKARI U.K. consortium website http://www.akari.org.uk/
ISAS website http://www.ir.isas.jaxa.jp/ASTRO-F/Outreach/index_e.html
ESA AKARI website http://astro-f.esac.esa.int/
Details of the conference can be found at:
Royal Astronomical Society:
The press release images can be found on a password-protected site at:
Captions (jpeg images within jpeg_full folder):
All sky map (unlabelled). This image is made from 9-micrometre wavelength infrared radiation. The bright stripe running across the centre of the image from left to right is the disk of our own Galaxy (the Galactic Plane). The brightest region in the very centre of the image is in the direction of the very centre of the Galaxy. In this direction old, bright red stars crowd together adding their contribution to the infrared emission of our Galaxy in addition to that from the interstellar dust. Several bright regions are also visible, corresponding to strong infrared radiation along or next to the Galactic Plane. These are sites of newly born stars where we are viewing the radiation emitted from the heated dust.
(As IRC_AllSky.jpg with English labels)
An image of the sky in the direction of the constellations of Orion and Monoceros, made using visible light. Bright stars dominate the scene and there are several pinkish emission nebulae (clouds of gas and dust) lit up by radiation from newly formed stars.
A 30 x 40 square degrees far-infrared map of the same region of the sky, made with the AKARI satellite, with marks indicating the positions of the bright stars that make up the constellation of Orion. The Galactic Plane runs from top to bottom on the left side of the image and associated cold dust appears as a diffuse glow over the whole picture.
The very bright source just below the belt of Orion is the famous Orion nebula (M42). Many stars are being born in this nebula and the dust heated up by these stars is a very strong emitter of infrared radiation. The bright object on the left side of Orion’s belt is another major star forming region that includes the Horsehead nebula. In contrast to its appearance in visible light as a dark cloud, it is extremely bright in the infrared. The bright, extended emission seen in the middle-left part of the image is the so-called Rosette Nebula, yet another star forming region. Finally, at the top of Orion is a big ring structure. This is the remnant of a series of explosions that took place when some of the most massive stars ended their lives as supernovae, sweeping the dust and gas in the region into a shell-like structure.
The Orion nebula is located about 1500 light years from the Earth and the Rosette nebula is at a distance of around 3600 light years.
This is an infrared image of the ‘Cygnus-X’ region taken by AKARI. The image covers 7.6 x 10 square degrees in the constellation of Cygnus. This region is in the direction of the ‘Orion arm’, one of the spiral arms of our Galaxy and the Galactic Plane runs from top left to bottom right.
Objects in this image are at distances of between 3000 and 10000 light years. The many bright spots mark regions where new stars are being born. They heat up the dust and ionise the gas in their vicinity producing strong infrared radiation. There are only a small number of regions that exhibit so many massive star-forming regions over such a restricted area of the sky. Large, dark hollows are also clearly visible on the image. They are created as radiation from clusters of massive, high-temperature stars blows away the surrounding gas and dust.
NOTES FOR EDITORS:
The AKARI Project is carried out with the support of Nagoya University, The University of Tokyo, the National Astronomical Observatory Japan, the European Space Agency (ESA), Imperial College London, the University of Sussex, The Open University (UK), the University of Groningen / SRON (The Netherlands), Seoul National University (Korea). The far-infrared detectors were developed in collaboration with The National Institute of Information and Communications Technology.