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X-ray Astronomy at JAXA Japan's Leading-Edge X-ray Astronomy: Unveiling the Mysteries of a Dynamic Universe
ASTRO-EII Launched Into Space - Summer 2005
 
One of the World's Three Key Stars

Differentiation from Chandra and XMM-Newton

XMM-Newton Illustration Candra Illustration
Performance comparison of big three international X-ray satellite in the 2000s
ASTRO-E was launched just after the United States and Europe launched their own advanced X-ray observatories — NASA's Chandra and ESA's XMM-Newton — in 1999. At that time ASTRO-E was positioned to become one of the world's top three X-ray observatories, but unfortunately the launch was not successful. ASTRO-EII is the successor to that mission.
The three observatories have clearly distinct capabilities, which means that, through cooperation, they can efficiently complement each other. In Prof. Takahashi's words: "It's important to take the position that astronomy satellites are to be used by everyone. As long as ASTRO-EII offers data that uses the same analysis system as Chandra and XMM-Newton, it will be appreciated by researchers around the world."
So, what is ASTRO-EII's particular strength?
As Prof. Takahashi explains: "Chandra has high image resolution. It's like a digital camera with many pixels. And XMM-Newton has powerful light-collecting capability, so it can gather a lot of X-ray molecules in a short time span. Meanwhile, the strength of ASTRO-EII is spectroscopy — it can recognize tens of thousands of different colors where in the past only thousands of colors could be defined. In terms of astrophysical phenomena — in other words, the energy of X-rays — the 'ecolors' emitted by a celestial body are a signal. The signal is a clue to measuring the convulsive motion and energy of massive amounts of hot gas, for example in collisions of galaxy clusters consisting of several hundred galaxies. In short, we can learn about the dynamics of the universe by analyzing colors."
After having been recognized as one of the big three contributors to X-ray astronomy, Japan seemed to have fallen behind after the failure of the ASTRO-E launch. Thanks to the delay, however, international anticipation for ASTRO-EII has only grown, as celestial phenomena unobservable by other X-ray satellites are being found. This time, Japan has been able to underline its indigenous capabilities. After all, everything has turned out for the best.
Dreaming About the Gas that Fills Galaxy Clusters

Kazuhiro Nakazawa,
Research Assistant, High Energy Astrophysics, Institute of Space and Astronautical Science, JAXA

The ultimate goal of ASTRO-EII is to solve the mysteries of black holes and dark matter, and for this I have been working on galaxy cluster research since the ASCA project.

A galaxy cluster is the largest celestial body in the universe. For instance, while visible light shows the Coma Berenices cluster consisting of about 3,000 galaxies, X-rays reveal that it is actually a huge mass of gas. This suggests that the gas is trapped by unknown particles that are as yet invisible to us. In fact, more than 90 per cent of the matter in the universe consists of the unknown, which is called "dark matter." This means that, even including the Milky Way, stars, and galaxy cluster gas, what we are seeing is only a very small part of all the matter that exists in the universe.
No one has seen dark matter yet; however, when a galaxy cluster was observed by ASCA using X-rays, scientists were able to confirm the existence of a spot of dark matter at the center. Galaxy cluster gas that glows with X-rays is our landmark for finding signs of dark matter.

ASTRO-EII is also capable of gamma-ray observation, and today there is a theory that observation will show that galaxy clusters glow with gamma rays. If strong gamma-ray emissions are confirmed, it will be proof that inside galaxy clusters, which have thus far appeared to be permanently stable, there are vortices and strong shock waves releasing the most powerful energy in space. If we can prove the existence of something we have never seen or imagined, it might give us a precious piece of the puzzle of the evolution of the universe.

Also, ASTRO-EII has excellent high-resolution spectroscopy, which allows us to determine the velocity of celestial bodies. Because the universe is so massive, there is very little opportunity for us to watch the progress of its evolution in our lifetime. Measuring the velocity of various objects in space will enable us to create precise pictures of the universe several hundred million years in the past and future, as well as in the present.
The advanced spectroscopic analysis of ASTRO-EII, plus all the capabilities of Chandra and XMM-Newton, will make great contributions to understanding the universe.

Unveiling the Mysteries of the Universe 1 | 2 | 3 Observation Instruments
1. What Is X-ray Astronomy? 2. Japan's Leading-Edge X-ray Astronomy 3. ASTRO-EII Launched into Space - Summer 2005
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