Download Full Press Release - The Open University

Media Relations Office
Communications Group
The Open University
Milton Keynes
United Kingdom
MK7 6AA
t
f
e
w
+44 (0)1908 653343
+44 (0)1908 652247
[email protected]
www.open.ac.uk/media/
New s
For the attention of: news editors
August 30, 2006 [PR5217]
AKARI unveils the birth and death of stars
The Japan Aerospace Exploration Agency (JAXA) AKARI Infrared Space
Telescope has returned spectacular new images showing the earliest stages of
star formation and the final stages of the death of stars in our Galaxy.
The results presented in a press release in Japan depict scenes showing infrared
pictures of the birth and death of stars. The quality of these data has delighted
the Japanese, UK and Dutch Team members and shown the power of this new
telescope for studies of astronomical objects of our own Galaxy.
AKARI was launched on February 21st 2006 from Uchinoura Space Centre,
Japan, and is now about half way to complete its first map of the sky in infrared
light. Open University Physics & Astronomy Department astronomers Professor
Glenn White and Dr Stephen Serjeant are collaborating with colleagues at
Imperial College and the University of Sussex, and Japanese, Korean and Dutch
Partners in the far-infrared all sky survey experiment on the satellite. The
European Space Agency contributes to pointing reconstruction and ground
station support in return for access to some of the pointed observations.
Page 1 of 8
Figure 1: Artist impression of the AKARI satellite in orbit
Star-birth in Cepheus
An area of approximately 3 square degrees around the reflection nebula IC 1396
in the constellation Cepheus has been observed by the AKARI Infrared Camera
(IRC) in its scanning mode at wavelength
Figure 2: Mid-infrared Image of the Reflection Nebula IC1396 (The Elephant
Trunk Nebula). This false colour image was made by combining infrared camera
images at 9 & 18 µm wavelength.
IC 1396 is a bright star formation region located about 3000 light years from our
Solar System in a region where very massive (several tens of solar masses)
stars are presently being born. In addition to a massive O6.5V star that ionises
most of the gas in the nebula, several other young stars in the central region of
Page 2 of 8
the image have swept out the gas and dust to the periphery of the nebula,
creating a hollow shell-like structure.
The gas that has been swept out creates the bright filament-like structures seen
in the surrounding regions. The dust in the gas is heated by the intense light
coming from both the massive star at the centre of the nebula and the newly born
stars in the dense gas itself, and emits infrared light.
The formation of a new generation of stars is now taking place within this
compressed gas in these outer shell structures. The AKARI data reveals for the
first time, the detailed distribution of this swept out gas and dust over the entire
nebula, and sees many previously unknown newly born stars, enabling a census
to be made of the star formation in this area.
Glenn White, Professor of Astronomy at the Open University, and The Rutherford
Appleton Laboratory said “This image is extremely impressive - the infrared
radiation has penetrated through the obscuring dust clouds between the Earth
and the IC1396 reflection nebula allowing us to measure the whole star formation
history in the region. Observing star forming regions over areas of many square
degrees lets us study the physics of stars that are born and how earlier
generations of stars can feedback to and trigger the next burst of star birth.
PPARC’s role in providing funding for staffing and travel has enabled UK
astronomers to work at the forefront of the data analysis of the AKARI all sky farinfrared survey”
Dr Richard Savage, postdoctoral research fellow at the University of Sussex and
co-author of the far-infrared survey pipeline software said “These images are a
glimpse of vast range of science that AKARI is beginning to address. It's
fantastic to think how far we've come since launch and even more exciting how
much further we'll be able to go in the coming months. Although the telescope
has almost the same size mirror as the earlier all-sky survey mission, IRAS, the
improvements in detector technology and software processing since IRAS are
truly staggering, as can be seen by comparing this IRAS image at 12
wavelength (below) with the new AKARI image (above)"
Page 3 of 8
image shown earlier. The power of the AKARI data to reveal sharper and more
sensitive data can be seen by comparing this with the previous image
Dr Stephen Serjeant, Senior Lecturer in Astronomy at the Open University said “I
find it quite amazing that we can now see star formation in action at close
quarters in our own Galaxy with such clarity. The dust in these stellar birthplaces
absorbs the light and hides much of the action from optical telescopes. With data
like the beautiful AKARI image we can detect the reprocessed energy from the
dust and infer what's hidden. AKARI is a superb telescope to watch the birth of
stars like our Sun, and the birth of galaxies like our own”
A star in its death throes
The AKARI Far-Infrared Surveyor (FIS) instrument has been used to take an
image of the red giant star U Hydrae. This star is located at about 500 light years
from our Sun. These observations have detected extended dust clouds
surrounding this star, shown by the halo of emission around the central star.
Page 4 of 8
Figure 4: Far-infrared Image of Red-giant Star U Hydrae at a wavelength of 90
µm. The image size is about 20 arc minutes across.
Stars with masses close to the Sun will expand during the later stages of their
lives becoming so called "red-giant" stars. These stars often eject gas from their
surface into interstellar space during the final phases of their life. Dust is formed
in the ejected gas, and this mixture of gas and dust expands outward and
escapes from the star.
This “mass loss” process is so important that it may well determine the final stage
of the star’s life. Stars with masses close to that of our Sun will expand during the
later stages of their life becoming so-called 'red-giant' stars. During this final
phase of their life such stars often eject gas from their surface into interstellar
space - dust is formed in the ejected gas, and this mixture of gas and dust
expands and escapes from the star.
Since most of the ejected material consists of small grains with temperatures
below about 100 K, the natural regime to study these is at far infrared
wavelengths. The AKARI image clearly detects a detached shell-like dust cloud
surrounding U Hydrae at a distance of about 0.3 light years from the central star,
Page 5 of 8
and implies that a short and violent ejection of mass took place in the star some
10,000 years ago.
Figure 5. Artists’ impression of a red-giant star ejecting matter
Michael Rowan-Robinson, Professor of Astronomy at Imperial College, London
said “Observations at infrared wavelengths provide a unique view of the final
stages of the evolution of stars – in particular as they eject of shells of dusty
material which go on to seed future generations of star formation in the Galaxy.
This ejected material spreads throughout star forming clouds and may eventually
be assimilated into a new generation of stars, enriching them with heavy
elements. Observations like this help us understand what galaxies look like when
seen from large distances”.
Dr Seb Oliver, Reader in Astronomy at The University of Sussex added “Results
like this help us understand the relation between mass and light in our own
Galaxy. This understanding can then be used to help us weigh galaxies earlier in
the history of the Universe which in turn helps us model how galaxies form and
evolve”.
Dr Chris Pearson of the European Space Agency and JAXA said “AKARI’s
unique ability to map large areas of the sky is producing extraordinary insight into
the entire life cycle of stars in our Galaxy, providing for the first time high
Page 6 of 8
resolution images that are revealing the very moment of the birth of stars in
stellar nurseries as well as the final stages of the life-cycle of stars like the Sun.
The gain in image quality compared to the IRAS all-sky survey is quite
astounding and allows AKARI to make direct observations of the circumstellar
shells around evolved stars. Features in circumstellar shells only previously
inferred by using sophisticated image reconstruction are now directly accessible
to AKARI’s instruments”.
Figure 6: Comparison far-infrared Image of Red-giant Star U Hydrae at a
wavelength of 100 µm from the IRAS all-sky survey showing the same area as
the AKARI image.
The AKARI spacecraft is continuing its mission of exploration the Universe and
has already scanned more than half the sky. After completing a first pass of the
whole sky, it will repeat this several times to confirm sources, improve the
sensitivity, and search for variable objects. AKARI is an international mission with
strong collaboration with ESA, and a consortium of UK institutes (The Open
University, Imperial College London and Sussex University) and the SRON /
Kapteyn Institute in the Netherlands. The project also includes contributions from
Seoul National University, South Korea.
AKARI is developed by the Japan Aerospace Exploration Agency (ISAS/JAXA),
with the participation of Japanese universities and institutes. The FIS instrument
is developed by Nagoya University, JAXA, the University of Tokyo & the National
Astronomical Observatory of Japan and other institutes, with contributions of
Page 7 of 8
NICT to the development of the detectors. The IRC instrument is developed by
JAXA and the University of Tokyo and other supporting institutes.
Editor’s Notes
Academic contact details

Prof Glenn White
Professor of Astronomy
The Open University and The CCLRC Rutherford Appleton Laboratory
Tel: +44 (0)771 423 4897

Dr Stephen Serjeant
Tel: +44 (0)1908 652 724
The Open University
Mobile: 07946 605 913
Resources
Web
Website:
http://www.esa.int/esaCP/SEM4TU5LARE_index_0.html
Media contact
Louis de La Forêt 44 (0) 1908 653256 [email protected]
Page 8 of 8