AKARI Infrared Observatory

[Waspie_Dwarf]

Japanese Infrared Imaging Satellite "AKARI" Returns First Images

The Japanese Space Exploration Agency (JAXA) press release is reproduced below:

Commencement of AKARI Observations
and Initial Results from Performance Verification (PV) Phase

May 22, 2006 (JST)
Japan Aerospace Exploration Agency (JAXA)

The infrared satellite AKARI (formerly ASTRO-F) of the Japan Aerospace Exploration Agency (JAXA), which was launched from the Uchinoura Space Center on the 21st of February (UT), captured light for the first time when the telescope aperture lid was opened on the 13th of April. After the aperture lid was jettisoned the instruments became fully operational and their performance was confirmed. Following this, the telescope focus adjustment and the optimization of the attitude control system, etc., were successfully carried out.
We are pleased to announce that the in-orbit performance of the telescope and the two infrared instruments have been verified to be as expected and we are now moving from the performance verification (PV) phase to Phase 1 (real observations) of the mission. The final step in the PV phase has been to produce infrared images of world class resolution and sensitivity which will be presented to the general public.
AKARI carries two instruments, the Far Infrared Surveyor (FIS) and the near-mid Infrared Camera (IRC), to observe the entire sky spanning a large wavelength range from the near-infrared to the far-infrared (See Figure 1).
Figures 2 and 3, the initial images from the mission, show the drastic improvements in resolution and sensitivity over the infrared maps of the Universe currently available. Continuing into the main phase of the mission, we are now looking forward to new infrared maps of the Universe and exciting discoveries in the evolution and origin of stars, galaxies and planetary systems.
The FIS instrument detectors are provided by the National Institute of Information and Communications Technology (NICT) and the instrument itself was developed by Nagoya University, JAXA, the University of Tokyo, the National Astronomical Observatory of Japan and other supporting institutes. The IRC instrument was developed by JAXA, the University of Tokyo and other supporting institutes.
In addition to the domestic institutes mentioned above, the operation and data processing of the AKARI are carried out with international cooperation and support from the European Space Agency (ESA), the Imperial College London, the University of Sussex and Open University in the United Kingdom, the University of Groningen and the Netherlands Institute for Space Research (SRON) in the Netherlands and Seoul National University in South Korea.

Figure 1: AKARI satellite and focal plane instruments


Figure 2.1: Reflection Nebula IC4954 (far-infrared image)


Figure 2.2: Reflection Nebula IC4954 (mid-infrared image)


Figure 3: Spiral Galaxy M81 (near-mid-infrared image)

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About:
Infrared Imaging Satellite "AKARI"(ASTRO-F)

Source: JAXA press release Edited October 21, 2006 by Waspie_Dwarf

[Waspie_Dwarf]

Akari delivers its first images

These two images of the reflection nebula IC4954 were taken by the two instruments on board Akari - the Far-Infrared Surveyor (FIS) – on the left - and the near- and mid-Infrared Camera (IRC) – on the right. The observed wavelengths are 90 and 9 microns, respectively. The IC4954 region is situated at a distance of about 6000 light years from us and extends more than 10 light years across.
In these first infrared images of this area it is possible to see individual stars that have recently been born. They are embedded in gas and dust and could not be seen in visible light. Is it also possible to see the gas clouds from which these stars are made.

Credits: JAXA


22 May 2006
AKARI, the new Japanese infrared sky surveyor mission in which ESA is participating, saw ‘first light’ on 13 April 2006 (UT) and delivered its first images of the cosmos. The images were taken towards the end of a successful checkout of the spacecraft in orbit.

The mission, formerly known as ASTRO-F, was launched on 21 February 2006 (UT) from the Uchinoura Space Centre in Japan. Two weeks after launch the satellite reached its final destination in space – a polar orbit around Earth located at an altitude of approximately 700 kilometres.
On 13 April, during the second month of the system checkout and verification of the overall satellite performance, the AKARI telescope’s aperture lid was opened and the on-board two instruments commenced their operation. These instruments - the Far Infrared Surveyor (FIS) and the near-mid-infrared camera (IRC) - make possible an all-sky survey in six infrared wavebands. The first beautiful images from the mission have confirmed the excellent performance of the scientific equipment beyond any doubt.


Images of the reflection nebula IC4954, taken by Akari’s near-mid-infrared camera (IRC) (left) and IRAS, the only previous infrared sky surveyor (right).
This image comparison shows the enormous improvement in resolution and sensitivity brought by Akari, which is already able to provide us with much more precise information about this star forming region than previous observations.

Launched in 1983, the IRAS Infra-Red Astronomical Satellite was the first mission to make a complete infrared survey of the entire sky. The mission resulted from the joint venture between the USA, United Kingdom, and the Netherlands. IRAS produced infrared maps of the Universe which have been used until the present day.

Credits: JAXA/IRAS

AKARI’s two instruments were pointed toward the reflection nebula IC4954, a region situated about 6000 light years away, and extending more than 10 light years across space. Reflection nebulae are clouds of dust which reflect the light of nearby stars. In these infrared images of IC4954 ­ a region of intense star formation active for several million years – it is possible to pick out individual stars that have only recently been born. They are embedded in gas and dust and could not be seen in visible light. It is also possible to see the gas clouds from which these stars were actually created.

"These beautiful views already show how, thanks to the better sensitivity and improved spatial resolution of AKARI, we will be able to discover and study fainter sources and more distant objects which escaped detection by the previous infrared sky-surveyor, IRAS, twenty years ago," says Pedro García-Lario, responsible for ‘pointing reconstruction’ - a vital part of the AKARI data processing - at ESA’s European Space Astronomy Centre (ESAC), Spain. "With the help of the new infrared maps of the whole sky provided by AKARI we will be able to resolve for the first time heavily obscured sources in crowded stellar fields like the centre of our Galaxy," he continued.


These infrared images of the galaxy M81 were taken by the near- and mid-Infrared Camera (IRC) on board Akari. The observed wavelengths are 3, 4, 7, 11, 15, and 24 microns, respectively. M81 is a spiral galaxy located at a distance of about 12 million light years from us.
The images at 3 and 4 microns show the distribution of stars in the inner part of the galaxy without any obscuration from intervening dust clouds. At 7 and 11 microns it is possible to see the radiation from organic materials in the interstellar gas of the galaxy. The distribution of the dust heated by young hot stars is exhibited in the images at 15 and 24 micron, showing that the star forming regions sit along the spiral arms of the galaxy.

Credits: JAXA

With its near-mid-infrared camera, AKARI also imaged the galaxy M81 at six different wavelengths. M81 is a spiral galaxy located about 12 million light years away. The images taken at 3 and 4 microns show the distribution of stars in the inner part of the galaxy, without any obscuration from the intervening dust clouds. At 7 and 11 microns the images show the radiation from organic materials (carbon-bearing molecules) in the interstellar gas of the galaxy. The distribution of the dust heated by young hot stars is shown in the images at 15 and 24 microns, showing that the star forming regions sit along the spiral arms of the galaxy.

"It’s a feeling of tremendous accomplishment for all of us involved in the AKARI project to finally see the fruits of the long years of labour in these amazing new infrared images of our Universe,” said Chris Pearson, ESA astronomer located at ISAS and involved with AKARI since 1997, “We are now eagerly waiting for the next ‘infrared revelation’ about the origin and evolution of stars, galaxies and planetary systems."


Having concluded all in-orbit checks, AKARI is now entering the first mission phase. This will last about six months and is aimed at performing a complete survey of the entire infrared sky. This part of the mission will then be followed by a phase during which thousands of selected astronomical targets will be observed in detail. During this second phase, as well as in the following third phase in which only the infrared camera will be at work, European astronomers will have access to ten percent of the overall pointed observation opportunity.

“The user support team at ESAC are enthusiastic about the first images. They show that we can expect a highly satisfactory return for the European observing programme," said Alberto Salama, ESA Project Scientist for AKARI. “Furthermore, the new data will be of enormous value to plan follow-up observations of the most interesting celestial objects with ESA’s future infrared observatory, Herschel,” he concluded.

Note:

AKARI is the result of an international effort. It was 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 NICT to the development of the detectors. The IRC instrument is developed by JAXA and the University of Tokyo and other supporting institutes.

Including Seoul National University, South Korea, the project also draws on the involvement of ESA and a consortium of UK universities (Imperial College, London; The Open University & the University of Sussex) funded by the Particle Physics and Astronomy Research Council (PPARC), as well as the Netherlands Institute for Space Research and Groningen University (NL).


The infrared satellite, ASTRO-F, was successfully launched by the Japan Aerospace Exploration Agency (JAXA) on 21 February 2006. In a collaborative effort involving ESA and scientists across Europe, the spacecraft (renamed Akari, meaning 'light') will make an unprecedented study of the sky in infrared light.

Credits: JAXA

ESA/ESAC provides expertise and support for the sky-survey data processing, through the pointing reconstruction – this allows the determination of accurate astronomical positions for each of the new sources discovered. ESAC also provides user support for the observing opportunities distributed to European astronomers. ESA/ESOC is providing the mission with ground support through its ground station in Kiruna, for several passes per day.


Source: ESA - News

[Waspie_Dwarf]

AKARI unveils the birth and death of stars

The Japanese Space Exploration Agency (JAXA) press release is reproduced below:

AKARI unveils the birth and death of stars

August 28, 2006 (JST)
Japan Aerospace Exploration Agency (JAXA)

The Japan Aerospace Exploration Agency (JAXA) infrared astronomical satellite AKARI (formerly known as ASTRO-F) was launched on February 21st, 2006 (UT) from Uchinoura Space Centre, Japan. AKARI is continuing its' mission of surveying the entire sky, making a complete map of our cosmos in infrared light. Here we report two new exciting images recently made by AKARI, depicting scenes from the birth and death of stars.


1. Star-birth!
Figure 1 is an image of the reflection nebula IC 1396 in the constellation Cepheus taken by the Infrared Camera (IRC) in its' scanning mode. 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. Massive young stars in the central region of the image have swept out the gas and dust to the periphery of the nebula, creating a hollow shell-like structure.
The formation of a new generation of stars is now taking place within the compressed gas in these outer shell structures. AKARI has revealed for the first time, the detailed distribution of this swept out gas and dust over the entire nebula with this high resolution and quality image. Many recently born stars that were previously unknown are expected to be detected in the new image. Detailed analysis of this data will reveal the story of the star formation in this area.


2. A star in its' death throes
Figure 2 is an image of the red giant star U Hydrae taken by the Far-Infrared Surveyor (FIS) instrument. This star is located at about 500 light years from our Sun. AKARI observations have detected very extended dust clouds surrounding this star.
Stars with masses close to the Sun will expand during the later stages of their lives becoming so called "red-giant" stars. Such stars will 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 out and escapes from the star. AKARI's superior quality and higher resolution image clearly detects a shell like dust cloud surrounding U Hydrae at a distance of about 0.3 light years from the central star. This image implies that a short and violent ejection of mass took place in the star some 10,000 years ago.

Figure 1: Mid-infrared Image of Reflection Nebula IC1396
(False color composite from 9 & 18 µm images)



Figure 2: Far-infrared Image of Red-giant Star U Hydrae
(wavelength: 90 µm)

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Mission website:
Infrared Imaging Satellite "AKARI"(ASTRO-F)

Source: JAXA press release Edited November 4, 2006 by Waspie_Dwarf

[Waspie_Dwarf]

AKARI’s view on birth and death of stars

This mid-infrared, false-colour composite image shows the reflection nebula IC 1396 in the constellation Cepheus, as viewed by AKARI’s Infrared Camera (IRC) in its scanning mode (at 9 and 18 micrometers 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. Massive young stars in the central region of the image have swept out the gas and dust to the periphery of the nebula, creating a hollow shell-like structure.
The formation of a new generation of stars is now taking place within the compressed gas in these outer shell structures. With this high-resolution and high-quality image AKARI has revealed for the first time the detailed distribution of the gas and dust swept out over the entire nebula. Many recently born stars that were previously unknown are now expected to be detected thanks to this new image, while detailed analysis of these data will reveal the story of the star formation in this area.

Credits: JAXA


28 August 2006
AKARI, the Japan Aerospace Exploration Agency (JAXA) infrared astronomical satellite with ESA participation, is continuing its survey of the sky and its mapping of our cosmos in infrared light. New exciting images recently taken by AKARI depict scenes from the birth and death of stars.

AKARI's Infrared Camera (IRC) imaged the reflection nebula IC 1396 in the constellation Cepheus (a reflection nebula is a cloud of dust which reflects the light of nearby stars). IC 1396 is a bright star-forming region located about 3000 light years from our Solar System, in a region where very massive stars – several tens of times as massive as our Sun - are presently being born. Massive young stars in the central region of the image have swept out the gas and dust to the periphery of the nebula, creating a hollow shell-like structure.
A new generation of stars is now taking place within the compressed gas in these outer shell structures. With this high-resolution and high-quality image of IC 1396, AKARI has revealed for the first time the detailed distribution of the gas and dust swept out over the entire nebula.


This view provides a comparison between a visible image (left) of the reflection nebula IC 1396 – an intense star forming region - and a mid-infrared view of the same area as seen by AKARI’s satellite (right).
In the visible light (left image) it is possible to see the emission from ionized (charged) hydrogen gas as well as light emitted from the massive stars in the centre and scattered by the interstellar dust. High density gas clumps are seen as dark stains. New stars born in these dark regions do however appear bright if observed in infrared light (right image).

Massive young stars, recently born in the centre of the imaged area (right image), blow out interstellar gas and dust and create the giant hollow seen in the central region. The gas that has been swept out creates the bright filament-like structures seen in the infrared 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 bright clump seen on the slightly off-centre right-hand side is known as the ‘Elephant Trunk Nebula’, a star forming region too. It appears as a dark nebula in the visible light (left image), but it is very bright in the infrared. It is a clump of dense gas that was not originally blown away because of its very high density.

Credits: D.De Martin, ESA/ESO/NASA FITS Liberator & Digitized Sky Survey (left), JAXA (right)

A comparison between a visible image of IC 1396 and AKARI's view of the same area shows that stars being born in regions that appear dark in visible light (left), do however appear bright if observed in infrared light (right).


The gas that has been swept out creates the bright filament-like structures seen in infrared 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 bright clump seen on the slightly off-centre right-hand side is known as the 'Elephant Trunk Nebula', a star forming region too. It appears as a dark nebula in the visible light (left image), but it is very bright in the infrared. It is a clump of dense gas that was not originally blown away because of its very high density.

Many recently born stars that were previously unknown are now expected to be detected thanks to AKARI's new image, while the detailed analysis of these data will reveal the story of the star formation in this area.


This far-infrared image (90 micrometers wavelength) shows the red giant star ‘U Hydrae’ as viewed by AKARI’s Far-Infrared Surveyor (FIS) instrument. This star is located at about 500 light years from our Sun. AKARI’s observations have revealed very extended clouds of dust surrounding this star.
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 the 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. AKARI's superior quality and high-resolution imaging allowed the clear detection of a shell-like dust cloud surrounding U Hydrae at a distance of about 0.3 light years from the central star. This implies that a short and violent ejection of mass took place in the star about 10 000 years ago.

Credits: JAXA

AKARI's Far-Infrared Surveyor (FIS) instrument imaged the red giant 'U Hydrae', a star located at about 500 light years from our Sun. AKARI’s observations have revealed very extended clouds of dust surrounding this object.

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 the 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.



This artist’s impression shows a ‘red-giant’ star ejecting matter. Stars with masses close to that of our Sun become ‘red-giant’ stars in the later stages of their life. The radius of a red-giant star expands to a size comparable to the orbit of the Earth, and the matters at the surface of the star flows out and escapes. Dust is formed in the out-flowing gas when the temperature decreases. This mixture of gas and dust is blown away from the central star, and expands into space. The dust cloud seen by the infrared satellite AKARI in U Hydrae was formed about 10 000 years ago by an intense mass ejection, and it reached an extension of about 0.3 light years.

Credits: JAXA

AKARI's superior quality and high-resolution imaging allowed the clear detection of a shell-like dust cloud surrounding U Hydrae at a distance of about 0.3 light years from the central star, implying that a short and violent ejection of mass took place in the star about 10 000 years ago.


Note:

AKARI (formerly known as ASTRO-F) was launched on 21 February 2006 (UT) from the Uchinoura Space Centre, Japan, and started its complete sky survey in April 2006.

The mission is the result of an international effort. It was 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 NICT to the development of the detectors. The IRC instrument is developed by JAXA and the University of Tokyo and other supporting institutes.

Including Seoul National University, South Korea, the project also draws on the involvement of ESA and a consortium of UK universities (Imperial College, London; The Open University & the University of Sussex) funded by the Particle Physics and Astronomy Research Council (PPARC), as well as the SRON Netherlands Institute for Space Research and the Groningen University (NL).

ESA/ESAC provides expertise and support for the sky-survey data processing, through the pointing reconstruction – this allows the determination of accurate astronomical positions for each of the new sources discovered. ESAC also provides user support for the observing opportunities distributed to European astronomers. ESA/ESOC is providing the mission with ground support through its ground station in Kiruna, for several passes per day.

Source: ESA - News

[Waspie_Dwarf]

The Japanese Space Exploration Agency (JAXA) press release is reproduced below:

The quest to unravel the mysteries of galaxy formation: Infrared images of the Large Magellanic Cloud.

--- AKARI moves towards completion of its first scan of the entire sky ---

November 1, 2006 (JST)

Japan Aerospace Exploration Agency (JAXA)

The Japan Aerospace Exploration Agency's (JAXA) infrared astronomical satellite AKARI [1] continues its mission to map the entire sky in infrared light. AKARI commenced the mission's All-Sky Survey observations in May, 2006 and will finish its first coverage of the entire sky in November. The estimated completeness of the coverage at the finish of the first coverage will be about 70 percent, which is what was expected, since some areas were known not to be presently observable due to disturbances by the Moon and other reasons.

During the survey observations, AKARI investigated one of the most important targets for studies of the formation of galaxies, the Large Magellanic Cloud [2], with more wavelength bands than has ever been made in the past, producing stunning images of our nearest neighbour in the Universe.

[infrared images of the Large Magellanic Cloud by AKARI and their implications]

(1) Far-Infrared Image of the Large Magellanic Cloud

AKARI obtained a far-infrared image of the Large Magellanic Cloud showing very active star formation over the entire galaxy known as a "starburst". The image reveals the dust and gas (interstellar matter) distribution over the entire galaxy. Dust grains in these interstellar clouds are heated by the light from recently born stars, and subsequently re-radiate this energy as infrared light. The infrared emission indicates that a great number of stars are currently being formed in this galaxy. Such starburst phenomena are thought to take place in many galaxies during their growth and evolution. 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 (see also appendix). The images from AKARI 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.

The AKARI All-Sky Survey will be far superior to the previous IRAS survey mission [3] especially in its ability to observe finer structure in the galaxy which will provide us with much more detailed information about the location and conditions of starburst. The four wavelength bands in the far-infrared range, two of which are beyond the IRAS coverage, are powerful tools to investigate the physical conditions, especially the temperature, of the interstellar clouds. Using this data we will be able to unlock the secrets of the starburst process that plays such an important role in the formation of galaxies.

(2) Near- and Mid-Infrared Images of the Large Magellanic Cloud

In addition to the All-Sky Survey observations, AKARI also took further detailed images of a segment of the Large Magellanic Cloud at shorter near- and mid-infrared wavelengths (Figure 2). 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 back into the interstellar medium at the end of their lives. The unique capabilities of AKARI are again highlighted in the sheer number of stars detected in these images compared to the previous IRAS mission.

AKARI had some trouble at the beginning of the mission due to the fact that the two-dimensional Sun Sensor could not detect light from the Sun etc. Also the Star Trackers, one of the sensors for attitude control, have a problem on their cooling system. However, these problems have been successfully overcome, and now AKARI is in very good condition and continues to provide high-quality data such as the images shown here.

[1] 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.

[2] The Large Magellanic Cloud is a local, neighbouring galaxy just next to our Milky Way Galaxy to which our Solar System belongs. It contains about 10 billion stars (1/10 of our Galaxy) and is at a distance of 160,000 light years, extremely close by astronomical standards. The Large Magellanic Cloud is visible from the southern hemisphere, located

in the constellation of Dorados. One can see this galaxy together with a smaller neighbouring galaxy, the Small Magellanic Cloud as two dim clouds in the sky. The name "Magellanic" is taken from the great 16th Century navigator Magellan who observed the clouds during his voyage around the world.

[3] IRAS was the first infrared astronomical satellite launched in 1983 by a joint team from the United States, The Netherlands, and the United Kingdom. It carried out the very first infrared All-Sky Survey, the results of which are still being used for astronomical purposes to this day. Similarly, AKARI promises a new valuable legacy for the decades to come.

For inquiries:

Management and Integration Department,

Institute of Space and Astronautical Science (ISAS)

Tel: +81-42-759-8487

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Figure 1: Far-Infrared image of the Large Magellanic Cloud by AKARI

(False-color composite from images at 60, 90 and 140 microns).

* AKARI image of the Large Magellanic Cloud. AKARI is continuing its observations to obtain this kind of data over the entire sky. This figure is a part of that data covering about 6x6 degrees (corresponding to a physical size of 17,000 x 17,000 light years at the distance of the galaxy)

* The bright region in the bottom-left is known as the "Tarantula Nebula", and is a very productive factory of stars.

Figure 2: Near- and mid-infrared image of the Large Magellanic Cloud taken by AKARI

(False color-composite from images at 3, 7 and 11 microns).

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Appendix

Appendix 1: The Large Magellanic Cloud in visible light (courtesy of Mr. Motonori Kamiya) and areas of the AKARI images.

Appendix 2: An image of the Large Magellanic Cloud taken by the preceding infrared astronomical satellite, IRAS (at the wavelength of 100 µm)

(Infrared Processing and Analysis Center, Caltech/JPL)

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Mission website:

Infrared Imaging Satellite "AKARI"(ASTRO-F)

Source: JAXA press release

[Waspie_Dwarf]

The Japanese Space Exploration Agency (JAXA) press release is reproduced below:

AKARI observes Star Forming Regions, Stars at the end of their life,

Supernova Remnants, Active Galactic Nuclei, and distant galaxies.

The University of Tokyo,School of the Science

Nagoya University

Japan Aerospace Exploration Agency(JAXA)

The first Japanese infrared astronomy satellite AKARI, launched in February 2006, continues observations in good condition. Further initial scientific results will be presented in the annual meeting of the Astronomical Society of Japan on the 28th - 30th of March 2007. Five selected results are explained here. On this occasion, the research concerns observations chiefly using the Near- and Mid-Infrared Camera (IRC), one of the instruments onboard AKARI.

1. Star formation history revealed by AKARI wide-area survey observations.

–– Star formation over three generations in the nebula IC4954/4955 in the constellation Vulpecula ––

The cycle of star formation over three generations of stars was observed for the first time at seven different infrared wavelengths by AKARI. The results shed light on the process in which stars form in our Galaxy.

2. The first infrared detection of a supernova remnant in the Small Magellanic Cloud

AKARI detected for the first time, a supernova remnant in our neighbouring galaxy, the Small Magellanic Cloud in the infrared wavelength from 3 to 11 micrometres, and investigated the interaction between the supernova remnant and the interstellar material. This result will be presented in the annual meeting of the Korean Astronomical Society in April.

3. Stars in the later stages of their life cycle as seen by AKARI

–– Detection of mass-loss from relatively young red-giant stars in the globular cluster NGC 104 ––

AKARI detected evidence of high mass-loss rate from the relatively young red-giant stars based on observations from 3 to 24 micrometres. This finding provides us with new insight into to the evolution of the stars in the later stages of their life.

4. Molecular gas surrounding an active galactic nucleus with a giant black hole at its centre as seen by AKARI infrared observations

–– Detection of the molecular gas surrounding the active galactic nucleus in the ultra luminous infrared galaxy UGC05101 ––

AKARI has discovered evidence for molecular gas of different temperatures surrounding the active galactic nucleus containing an enormous black hole at its centre. This data will provide vital clues in understanding the structure of galaxies harbouring active galactic nuclei and black holes.

5. AKARI confirms an era of intense active star formation in the Universe

–– Deep sky survey in 15 micrometre infrared light ––

The Near- and Mid-Infrared Camera onboard AKARI has carried out a wide area deep survey in 15 micrometre infrared light, detecting many galaxies. This result indicates that a phase of intense active star formation took place in the Universe, lasting several billion years over 6 billion years ago.

AKARI is a JAXA’s mission 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.

[LINK]

AKARI Project site >>

1.Star formation history revealed by AKARI wide-area survey observations.

–– Star formation over three generations in the nebula IC4954/4955 in the constellation Vulpecula ––

This study is conducted by Dr. D. Ishihara, research fellow at the School of the Science, University of Tokyo.

The cycle of star formation over three generations of stars was observed for the first time at seven different infrared wavelengths by AKARI. The results shed light on the process in which stars form in our Galaxy.

IC4954/4955 are reflection nebulae in the constellation Vulpecula, located around 6500 light years distant from the Sun. The left panel of Figure 1.1 shows a three-colour composite image from AKARI’s 9 (blue), 11 (green), and 18 (red) micrometre data. Regions in white are thought to be high-density regions. Two arc-like structures are clearly seen in the image. These are formed by a young, massive star (not seen in the image) at the centre of the nebula sweeping the material outward by their strong radiation pressure. Astronomers believe that new stars are formed in such high-density regions. The arcs are located at a distance of about one light year from the central star. The colour composite image from the far-infrared data (right side of Figure 1.1) shows that the arcs are also heated by the central star and appear blue.

Figure 1.2 is a two-colour composite from the 9 and 18 micrometre data of the surrounding region of the stellar nursery and is about 20 times broader than the previous figure. The brightest region in this figure is IC4954/4955. In addition a distinct hollow in the middle of the image is apparent. The diameter of this hollow is about a hundred light years. We suspect that an even earlier, first generation star formed around several to ten million years ago, and that this object induced the star formation of the second generation including the IC4954/4955 region.

The observations of IC4954/4955 were carried out with the Near- and Mid-infrared Camera (IRC) and the Far-Infrared Surveyor (FIS) instruments onboard AKARI carried out observations of this region at seven different infrared wavelengths (9, 11, 18, 65, 90, 140, and 160 micrometres). AKARI's images powerfully demonstrate that infrared observations are vital to detect the material that is invisible to us in normal visual light.

Figure 1.1(left) Figure 1.1(right)

Figure1.2

2. The first infrared detection of a supernova remnant in the Small Magellanic Cloud.

This study is carried out by the research group lead by Prof. Bon-Chul Koo in Seoul National University, Korea.

AKARI detected for the first time, a supernova remnant in our neighbouring galaxy, the Small Magellanic Cloud in the infrared wavelength from 3 to 11 micrometres. The AKARI data reveal the presence of a shock at the interaction between the expanding supernova remnant and the surrounding interstellar medium. The result implies that the precursor of this supernova remnant was a high mass star.

The Small Magellanic Cloud is a small galaxy neighbouring our own Milky Way Galaxy at a distance of 200 000 light years, visible from the southern hemisphere. AKARI detected the supernova remnant B0104-72.3 in this galaxy for the first time at the infrared wavelengths of 3, 4, 7 and 11 micrometres with the Near- and Mid-Infrared Camera (IRC) onboard AKARI. Figure 2 shows the colour composite image of the supernova remnant. A pair of arc-like structures in the middle of the image are the supernova remnant extended to approximately 60x100 light years.

After a supernova explosion at the end of a life of stars much heavier than our own Sun, the matter ejected from the star expands into interstellar space and forms a supernova remnant. Supernovae provide materials for the formation of next generation stars. The contribution of supernova is an essential component in the evolution of our own and other galaxies. Observations with AKARI are expected to play a key role in understanding the evolution of the interstellar material via studies of interaction processes with the supernova remnant.

Figure2

3. Stars in the later stages of their life cycle as seen by AKARI

–– Detection of mass-loss from relatively young red-giant stars in the globular cluster NGC 104 ––

This research is mainly carried out by Dr. Y. Ita (ISAS/JAXA) and Dr. N. Matsunaga (Univ. of Tokyo)

AKARI detected evidence of high mass-loss rate from the relatively young red-giant stars based on observations from 3 to 24 micrometres. This finding provides us with new insight into to the evolution of the stars in the later stages of their life.

Stars with the mass similar to the Sun will evolved to red-giant stars at the late stage of their life. The red-giant stars eject their mass to the interstellar space, which is known as 'mass loss'. Theories predict that such mass loss takes place already in the early stage of the red-giant phase. However, observational evidence of high mass loss so far obtained are all from relatively evolved red-giant stars.

NGC104, also known as 47 Tuc, is a globular cluster visible from the southern hemisphere in the constellation of Tucana. AKARI observed NGC 104 with the Near- and Mid-Infrared Camera (IRC). Figure 3 shows a three colour composite image of the target from the 3, 11, and 24 micrometre data. The bright red stars seen in the image are mostly in the final stages of the red-giant phase and are losing their material at rates of as high as one millionth of their mass per year. A marked star located in the bottom-left corner is the star that was discovered to be losing mass at a high-rate while still in the early stage of the red-giant phase. The current result confirms the presence of mass-losing younger red-giant stars for the first time.

The fate of a star depends on how this mass loss takes place during the life of the star itself. Further analysis of the data and investigation, together with theoretical modelling will enable us to understand how mass-loss changes in the star's life.

Figure3

4. Molecular gas surrounding an active galactic nucleus with a giant black hole at its centre as seen by AKARI infrared observations

–– Detection of the molecular gas surrounding the active galactic nucleus in the ultra luminous infrared galaxy UGC05101 ––

This study is mainly carried out by Prof. T. Nakagawa and Dr. M. Shirahata in ISAS/JAXA.

AKARI has discovered evidence for molecular gas of different temperatures surrounding the active galactic nucleus containing an enormous black hole at its centre. This data will provide vital clues in understanding the structure of galaxies harbouring active galactic nuclei and black holes.

UGC05101 in the constellation Ursa Major is around 550 million light years away from the Earth. The very central part of this galaxy is so bright at infrared wavelengths, that the object is termed an ‘Ultra Luminous Infrared Galaxy’. The total energy emitted from this galaxy at infrared wavelengths alone is about one trillion times more than the total energy of our Sun. It has been postulated that a giant black hole is sitting at the centre of UGC05101, and actss as an engine of the galaxy. However, the central region of this galaxy is covered by a thick interstellar medium, and to this day has never been observed, thus the mechanisms at work in the core region remain a mystery.

Thanks to its high sensitivity in the infrared, AKARI has taken up the quest to unravel the mystery of the central core of HGC05101. Figure 4.1 shows the spectrum of UGC05101 from 2 to 13 micrometres observed with the Near- and Mid-Infrared Camera (IRC) onboard AKARI. The spectrum shows many signals from dust, molecules, atoms, and ions. We especially focus on the characteristics of carbon monoxide (CO) molecules in the gas phase. The observed feature is very broad, indicating that the temperature of this molecular gas is over 500 degrees Centigrade. It is suspected that the warm molecular gas detected by AKARI is indeed being heated by radiation from nearby the black hole.

Figure4

5. AKARI confirms an era of intense star formation activity in the Universe

–– Deep sky survey in 15 micrometre infrared light ––

This research is carried out by Dr. T.Wada, S. Oyabu(ISAS/JAXA) and collaborators.

The Near- and Mid-Infrared Camera onboard AKARI has carried out a wide area deep survey in 15 micrometre infrared light, detecting many galaxies. This result indicates that a phase of intense active star formation took place in the Universe, lasting several billion years over 6 billion years ago.

Galaxies in which active star formation is taking place emit most of their energy as infrared radiation from the interstellar material heated by the light from the young hot stars. The light we observe from the distant galaxies, in reality, left the galaxies a long time ago. Infrared observations with the Infrared Space Observatory (ISO), the European infrared astronomy satellite launched in 1995, revealed that the number of faint, distant galaxies increased drastically when observed at 15 micrometres. This can be explained by the redshift effect, where the original light was emitted from the galaxies at a wavelength of 7 micrometres around 6 billion years ago. The conclusion was drawn from observations of a very small area of the sky containing only 24 galaxies detected in the infrared. Figure 5 shows the results of the deep survey observations at 15 micrometres by the Near- and Mid-Infrared Camera (IRC) onboard AKARI. We detected around 280 galaxies in this region. AKARI's observations concretely confirm the increase of the number of galaxies at 15 micrometres implied by the earlier ISO observations. Moreover, AKARI also discovered comparable numbers of even fainter galaxies, leading us to an important conclusion that the star formation activity was already high at times even earlier than 6 billion years ago.

AKARI is performing similar deep surveys over the entire wavelength range from 2 to 24 micrometres. Such multi-wavelength data will provide a definitive description of the dusty galaxy evolution over the life of our Universe.

Figure5

Source: JAXA press release

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AKARI presents detailed all-sky map in infrared light

11 July 2007

This image shows the entire sky in infrared light at nine micrometres. The bright stripe extending from left to right is the disc of our own Milky Way Galaxy. Several bright regions corresponding to strong infrared radiation appear along or next to the Galactic Plane. These regions are sites of newly born stars. At the brightest region in the very centre of the image, towards the centre of our Galaxy, old stars crowd together. AKARI observed the infrared radiation emitted from the heated interstellar dust.

Credits: JAXA

One year after the beginning of its scientific operations, the high-capability infrared satellite AKARI continues to produce stunning views of the infrared Universe.

Launched in February 2006, AKARI is making a comprehensive, multi-wavelength study of the sky in infrared light, helping to gain a deeper understanding of the formation and evolution of galaxies, stars and planetary systems. The mission is a Japan Aerospace Exploration Agency (JAXA) project with ESA and international participation.

In the course of last year, AKARI performed all-sky observations in six wavelength bands. More than 90 percent of the entire sky has so far been imaged. The mission provides the first census of the infrared sky since the atlas made by its only infrared surveyor predecessor, the Anglo-Dutch-US IRAS satellite more than 20 years ago. AKARI has studied about 3500 selected targets during pointed observations, with improved spatial resolution.

The latest results presented by JAXA today show the infrared sky with unprecedented spatial resolution and wavelength coverage and, in particular, many regions of active star formation.

This image shows the entire sky in infrared light at nine micrometres. The bright stripe extending from left to right is the disc of our own Milky Way Galaxy. Several bright regions corresponding to strong infrared radiation appear along or next to the Galactic Plane. These regions are sites of newly born stars. At the brightest region in the very centre of the image, towards the centre of our Galaxy, old stars crowd together. AKARI observed the infrared radiation emitted from the heated interstellar dust.

The inscriptions indicate constellations and regions of intense star formation. The data used to create this image have a spatial resolution of about nine arcseconds, several times finer than IRAS in 1983. Further detailed analysis of this data will help to learn more about the physical conditions of these star formation regions.

Credits: JAXA

The first two images presented in this article show the entire sky in infrared light at nine micrometres. The bright stripe extending from left to right is the disc of our own Milky Way Galaxy. Several bright regions corresponding to strong infrared radiation appear along or next to the Galactic Plane. These regions are sites of newly born stars. At the brightest region in the very centre of the image, towards the centre of our Galaxy, old stars crowd together. AKARI observed the infrared radiation emitted from the heated interstellar dust.

The inscriptions indicate constellations and regions of intense star formation. The data used to create this image have a spatial resolution of about nine arcseconds, several times finer than IRAS in 1983. Further detailed analysis of this data will help to learn more about the physical conditions of these star formation regions.

The bright spot on the lower-right of the image, indicated as the ‘Large Magellanic Cloud’ shows another galaxy close to our Milky Way, also undergoing active star formation. Even though not visible at the current resolution of this image, there are many more galaxies in the Universe with intense star formation processes. It is one of AKARI’s prime targets to observe these galaxies and build up a comprehensive picture of the star formation history of the Universe.

AKARI’s Far Infrared Surveyor (FIS) instrument also observed the Milky Way and the Orion region. In this image, two views at visual light (left) and infrared light (right) are juxtaposed, both covering a region of about 30x40 square degrees. AKARI’s view is taken at 140 micrometres. For the first time ever, AKARI provided coverage of the Orion region at infrared wavelengths longer than 100 micrometres at such fine resolution.

The right side of the image covers the constellation Orion while the left side shows the Monoceros. The Galactic Plane is located from the top to bottom in the left side of the image. Cold dust in the Galactic Plane appears as diffuse radiation over the entire image.

Credits: Hideo Fukushima, National Astronomical Observatory Japan (left); JAXA (right)

AKARI’s Far Infrared Surveyor (FIS) instrument also observed the Milky Way and the Orion region. In this image, two views at visual light (left) and infrared light (right) are juxtaposed, both covering a region of about 30x40 square degrees. AKARI’s view is taken at 140 micrometres. For the first time ever, AKARI provided coverage of the Orion region at infrared wavelengths longer than 100 micrometres at such fine resolution.

The right side of the image covers the constellation Orion while the left side shows the Monoceros. The Galactic Plane is located from the top to bottom in the left side of the image. Cold dust in the Galactic Plane appears as diffuse radiation over the entire image.

The very bright source just below the belt of Orion shows the famous Orion Nebula (M42), where many stars are being born. Another major star-forming region including the Horse Head nebula can be seen on the left side of Orion's belt. In contrast to its appearance as a dark cloud in visible light, 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, the big circular structure centred at the head of Orion is clearly visible. Apparently many massive stars were formed at the centre of the circle, causing a corresponding series of supernova explosions that has swept out the dust and gas in the region forming a shell-like structure.

The Orion Nebula is located about 1500 light years away from Earth; the Rosetta nebula 3600 light years.

This false-colour composite was obtained by AKARI’s Far Infrared Surveyor (FIS) instrument at 90 and 140 micrometres. It shows star-forming regions in the constellation Cygnus, one of the brightest regions in the Milky Way. The image covers 7.6 x 10.0 square degrees. This region is in a direction along the so-called ‘Orion arm’, one of the spiral arms of our Galaxy. Many objects at distances of three thousand to ten thousand light years are projected on this small region. The Galactic plane appears from the top-left to bottom-right.

Credits: JAXA

This false-colour composite was obtained by AKARI’s Far Infrared Surveyor (FIS) instrument at 90 and 140 micrometres. It shows star-forming regions in the constellation Cygnus, one of the brightest regions in the Milky Way. The image covers 7.6 x 10.0 square degrees. This region is in a direction along the so-called ‘Orion arm’, one of the spiral arms of our Galaxy. Many objects at distances of three thousand to ten thousand light years are projected on this small region. The Galactic plane appears from the top-left to bottom-right.

The many bright spots in the image reveal regions where new stars are being born. They heat up the dust and ionize the gas in their vicinity producing strong infrared radiation. There are only a small number of regions in our Galaxy that exhibit so many massive star-forming regions over such a restricted area of the sky.

The large, dark hollows, also clearly visible on the image, developed from clusters of massive, high-temperature stars that have blown away the surrounding gas and dust by their strong radiation.


Note

AKARI was launched on 21 February 2006. It began its all-sky survey observations in May 2006 and completed its first coverage of the sky in November 2006. The mission is currently in a phase dedicated to pointed observations, interleaved with supplemental scan observations to complete the all-sky survey. It is expected that the mission liquid Helium cryogen will last until at least September 2007.

AKARI is a JAXA mission carried out with the participation of several partners such as: the Nagoya University, The University of Tokyo and National Astronomical Observatory Japan; the European Space Agency (ESA); Imperial College London, the University of Sussex and The Open University (UK); the University of Groningen/SRON (The Netherlands); the Seoul National University (Korea). The far-infrared detectors were developed under collaboration with the National Institute of Information and Communications Technology (Japan).

ESA’s European Space Astronomy Centre (ESAC), Madrid, Spain provides expertise and support for the sky-survey data processing through the pointing reconstruction – this allows the determination of accurate astronomical positions for each of the sources detected. ESAC also provides user support for the European astronomers who have been granted observing opportunities. ESA’s Operations Centre (ESOC) in Darmstadt, Germany, is providing the mission with ground support through its ground station in Kiruna, for several passes per day.

Source: ESA - News

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AKARI’s observations of asteroid Itokawa

23 August 2007

The asteroid Itokawa was observed by the Infrared Camera (IRC) onboard AKARI at 7 micrometres on 26 July 2007.

The above image is a composite of three images from the data showing the motion of Itokawa over 12 minutes. The image covers an area of roughly 7.4 arcminutes x 7.4 arcminutes around the target. The Hayabusa spacecraft itself was too faint to be detected.

Credits: JAXA

The space-borne infrared observatory AKARI, observed asteroid Itokawa last month with its Infrared Camera. The data will be used to refine estimates of sizes of potentially hazardous asteroids in the future.

The data collected by AKARI, a JAXA mission with ESA participation, complements that from JAXA’s asteroid explorer Hayabusa in late April this year.

As AKARI observed Itokawa on 26 July it was in the constellation of Scorpius, and was about 19 magnitudes bright in visible light. The asteroid and Earth were closest to each other, at a distance of about 42 million km (for comparison, Earth is 150 million km from the Sun). Given how close it was, Itokawa moved a significant distance on the sky over the short observing time.

Using observational data of asteroids such as Itokawa in combination with data from the explorer, models that estimate asteroid sizes can be made more accurate. This is especially useful for estimating the size of potentially hazardous asteroids which may be discovered in the future.

Before Hayabusa arrived at Itokawa, many observations to determine the asteroid's approximate size had already been attempted. Among the many different methods of measurement, the most accurate estimate was achieved by mid-infrared observations.

With AKARI, it was possible to observe Itokawa at several different wavelengths in the mid-infrared range, obtaining a much more comprehensive set of data. This data is very important, not only for the study of the asteroid’s infrared properties, but also for use as a template and source of comparison with other asteroids, to improve the estimates of their sizes.

Most sunlight falling on Itokawa is absorbed, heating the asteroid up. It then re-emits this energy as bright infrared light, which was in turn observed by AKARI. Only a small fraction of the incident sunlight is reflected from Itokawa, making it a very faint object when observed in visible light. It is very hard to observe using telescopes of sizes similar to that of AKARI from ground.

This figure shows the positions of Itokawa and the Earth at the time of the observation (July 26th, 2007). 1 AU, or Astronomical Unit is the distance from Earth to the Sun, equal to 150 million km.

The planets and the asteroid Itokawa move along their orbits in the direction indicated. After three orbits for Earth and two orbits for Hayabusa, the asteroid explorer will arrive back at Earth in June 2010.

Credits: JAXA

Asteroid size is one of the most sought-after pieces of information. For asteroids that are not explored directly, their sizes can be estimated based on various observations from Earth. The temperature of asteroids is determined by the balance between the energy input from incident sunlight, and the output, emitted as infrared radiation.

Existing computer models estimate the temperature distribution in asteroids by considering their shape, rotational motion, and surface conditions.

Observational data in the mid-infrared gives information on the infrared light emitted by the asteroid. Asteroid size can be derived by comparing observational data in the mid-infrared, with that expected from the calculations of the model. The models can further be improved by using the infrared observational data of well-studied asteroids, such as Itokawa.

AKARI has also made observations of possible candidates for future asteroid exploration. It is expected that this detailed information will help greatly further our knowledge of these interesting relics of our Solar System.


Notes:

The observation of Itokawa was carried out by the asteroids observation group in the AKARI Solar-System Object consortium led by Dr Sunao Hasegawa at the Institute for Space and Astronautical Science (ISAS) in Japan.

AKARI is a JAXA mission with the participation of several partners: Nagoya University, University of Tokyo and National Astronomical Observatory in Japan; ESA; Imperial College London, University of Sussex and The Open University in the UK; University of Groningen / SRON (The Netherlands) and Seoul Nationa University (Korea).

The far-infrared detectors were developed in collaboration with The National Institute of Information and Communications Technology (Japan).

ESA’s European Space Astronomy Centre (ESAC) provides expertise and support for the sky-survey data processing through the pointing reconstruction. This allows the determination of accurate astronomical positions for each of the sources detected. ESAC also provides user support for the European astronomers who have been granted observing opportunities. ESA/ESOC is providing the mission with ground support through its ground station in Kiruna, for several passes per day.

AKARI was launched on 21 February 2006. It began its all-sky survey in May 2006 and completed its first coverage of the sky in November 2006. About 80 percent of the entire sky has been imaged by AKARI so far. The mission is currently in a phase dedicated to pointed observations, interleaved with observations that fill gaps in the all-sky survey.


For more information:

Alberto Salama, ESA ISO and AKARI Project Scientist Email: Alberto.Salama @ esa.int

Source: ESA - Space Science - News

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AKARI finishes its cool observations

The Japan Aerospace Exploration Agency / Institute of Space and Astronautical Science (JAXA/ISAS) press release is reproduced below:

The infrared astronomical satellite AKARI ran out of its on-board supply of cryogen, liquid Helium at 08:33 (UT) on August 26th, 2007, after successful operation and observations that began on May 8th, 2006. The boil off of the liquid Helium signals the completion of observations at far-infrared and mid-infrared wavelengths with AKARI, including the All-Sky Survey.

AKARI did in fact achieve the pre-launch expected lifetime of 550 days. During this period, AKARI completed the far-infrared All-Sky Survey covering about 94 per cent of the entire sky, and also carried out mid-infrared survey as well as more than five thousand individual pointed observations. The data obtained is now being intensively analysed by the project scientists and astronomers.

AKARI plans to continue warm phase observations using the surviving instruments that can still operate under the conditions provided by the additional on-board mechanical coolers. The preparation and performance evaluation of the next phase of the mission will be carried out over the next few months.

We warmly acknowledge all the people who support the AKARI mission.

AKARI Project Manager Professor Hiroshi Murakami


2007/8/28

Source: JAXA/ISAS

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Galaxies near and far from AKARI

This is a composite image of the spiral galaxy M101.

The image shows the distribution of cold (blue) and warm (red) dust overlaid on the visible
(green, showing distribution of stars) and far-ultraviolet (cyan, indicating the location of
young stars) images of M101.

Credits: Composite: JAXA, visible (green): the National Geographic Society, far-ultraviolet
(cyan): GALEX/NASA

5 September 2007
Two new sets of observations from the AKARI Infrared Space Telescope, JAXA mission with ESA participation, show how the spaceborne telescope has investigated galaxies both near and far.

In the first set, Toyoaki Suzuki, University of Tokyo, observed M101, a spiral galaxy 170 000 light-years in diameter. AKARI’s new observations reveal differing populations of stars spread across its spiral arms.

AKARI observed the galaxy at four infrared wavelengths (65, 90, 140, and 160 micrometres) using the Far-Infrared Surveyor (FIS) instrument. Many young high-temperature stars populate the spiral arms, revealing the areas of star formation and warming the interstellar dust. This causes the galaxy to shine at shorter infrared wavelengths. In contrast, the longer wavelengths show where the ‘cold’ dust is located. Normal stars, typically like our own Sun, warm this dust.



The above panels show images of spiral galaxy M101 overlaid with information from
FIS.

The left panel shows the distribution of the cold dust in the galaxy. Whereas the right
panel shows the distribution of warm dust in the spiral galaxy.

Credits: JAXA

FIS data was compared to an image of the galaxy in the visible and far-ultraviolet. It shows that the warm dust is distributed along the spiral arms, with many hot spots located along the outer edge of the galaxy. These spots correspond to giant star-forming regions. This is unusual because star formation is generally more active in the central parts of spiral galaxies.

The evidence points to M101 having experienced a close encounter with a companion galaxy in the past, dragging out gas from the hapless companion. The gas is now falling onto the outer edge of M101 at approximately 150 km/s, triggering the active star formation.


The image shows the distant Universe seen at far-infrared wavelengths (90 micrometres)
through the Galactic window near the South Ecliptic Pole in the sky. Many faint galaxies
are seen in white over the wide area of 10 square degrees. Observation fields of other
deep surveys at other wavelengths are overlaid.

Credits: JAXA

AKARI has also been observing galaxies in the far distant Universe to address one of the most important questions in modern astronomy: how did the galaxies evolve into their current form?

To help find the answer, Shuji Matsuura and Mai Shirahata, ISAS/JAXA, used AKARI to carry out one of the most extensive observations ever made in the far-infrared, detecting many faint galaxies in the distant Universe at FIR’s four wavebands. This wavelength information is essential to investigate the mechanisms responsible for the emission of infrared light and to estimate the distances to the galaxies.


The images show the distant Universe seen at four different far-infrared wavelengths
through the Galactic window near the South Ecliptic Pole in the sky. Many faint galaxies
are seen in white over the wide area of 10 square degrees. Observation fields of other
deep surveys at other wavelengths are overlaid.

Differences in the brightness of individual galaxies in the different wavelength bands are seen.

Credits: JAXA

The white spots in these images are all faint galaxies of different brightnesses. They imply that ordinary galaxies seen in the present time shone much more brightly in the infrared when they were younger. In many cases this is due to explosive episodes of star birth during earlier times. Some galaxies appear to have a differing brightness at different wavelengths than others and it is suspected that this might be because these galaxies are brightened by the energy released from a black hole at their cores.

The AKARI data shows that the number of galaxies increases rapidly as they appear fainter and so indicates that the galaxies have merged. However, they do not seem to evolve as drastically as inferred by previous observations. As AKARI’s are the most sensitive observations ever made at these wavelengths, this result suggests that a new galaxy evolution model may be necessary.


Note:

AKARI was launched on 21 February 2006 and began its scientific observations in May 2006.

Its on-board supply of liquid helium ran out on 26 August 2007, and the spacecraft entered a new mission phase. The liquid helium was required to keep AKARI cold enough to observe in the far-infrared. The ‘warm’ phase will now use the surviving instruments, which can operate under the warmer conditions provided by the on-board mechanical coolers, for near-infrared observations.

AKARI achieved its planned ‘cold’ lifetime of 550 days. During this time, it conducted an infrared All-Sky Survey, covering about 94 % of the entire sky, with larger wavelength coverage and better spatial resolution than its predecessor, IRAS. It has performed mid-infrared surveys and carried out more than five thousand individually pointed observations.

AKARI is a JAXA mission carried out with the participation of several partners such as: the Nagoya University, The University of Tokyo and National Astronomical Observatory Japan; the European Space Agency (ESA); Imperial College London, the University of Sussex and The Open University (UK); the University of Groningen/SRON (The Netherlands); the Seoul National University (Korea). The far-infrared detectors were developed under collaboration with the National Institute of Information and Communications Technology (Japan).

ESA’s Operations Centre (ESOC) in Darmstadt, Germany, is providing the mission with ground support through its ground station in Kiruna, for several passes per day. ESA’s European Space Astronomy Centre (ESAC), Madrid, Spain provides expertise and support for the sky-survey data processing through the pointing reconstruction – this allows the determination of accurate astronomical positions for each of the sources detected. The goal is to accelerate the production of the survey catalogues as a legacy for Herschel and Planck.

ESAC also provides user support for the European astronomers who have been granted observing opportunities. The 10% of observing time obtained from this collaboration resulted in 400 observations covering various fields of astronomy, from comets to cosmology. The Call for observing opportunities in the warm phase is expected for next Spring.


For more information:

Alberto Salama, ESA Akari Project Scientist
Email: Alberto.Salama @ esa.int
Source: ESA - Space Science - News