JAXA | X-rays Reveal an Intense and Dynamic Universe

Q. Could you tell us about the objective of the X-ray astronomy satellite ASTRO-H?

New Japanese X-ray astronomy satellite ASTRO-H

Hard X-ray imager for higher-energy wavelengths

Microcalorimeter with very high-energy resolution

ASTRO-H will conduct X-ray observations of extremely dynamic phenomena in the universe, looking at hot gases in clusters of galaxies, around black holes, and supernova remnants. The universe is filled with X-rays, which are a form of light that cannot be seen with the naked eye. X-rays are emitted from extremely hot regions – regions that have a temperature of millions to hundreds of millions degrees Celsius. Recent studies have shown that 80 to 90 percent of the material we can observe in the universe is so hot, it can only be seen with X-rays.
In the universe, very intense phenomena are occurring all the time: galaxies colliding and merging, stars violently exploding at the end of their life, etc. We are developing ASTRO-H to look specifically at such violent aspects of the universe at the highest-ever resolution. Using cutting-edge high-performance instruments, ASTRO-H will answer many questions and test certain assumptions we’ve had for some time.
A galaxy cluster is an object formed billions of years ago, when dark matter attracted hundreds of galaxies to one area of the universe. ASTRO-H will allow us to measure the velocity of super-hot gases in galaxy clusters – gases that are swirling at speeds of hundreds of kilometers per second – and to see what heavy elements exist there. For example, iron is ionized in these high-energy environments of the universe, and we will be able to study the detailed structure of line spectra that are emitted as a result. ASTRO-H is expected to show us the universe as it’s never been seen before.

Q. What is the best feature of ASTRO-H?

Simply put, it is to be able to observe the dynamism of the universe. For example, we expect to be able to detect massive black holes located in the center of newly formed galaxies, which have been hidden from us by thick clouds of gas. This way, ASTRO-H will give us clues to the structure and evolution of the universe.
To make this happen, we are developing world-class instruments. Typically, instruments placed on satellites are first used on the ground, but this time, for the first time, we are developing cutting-edge instruments that will have their debut in space, on ASTRO-H. It is clear that by improving instrument performance even by a factor of ten, we can reveal a new world. All of the instruments on ASTRO-H have much higher performance than we’ve ever seen before. We are looking forward to unraveling the mysteries of the universe with absolutely new eyes.

Q. What would you personally like to accomplish with ASTRO-H?

Galaxy M82 observed in X-rays. There is a black hole at its center. Blue, green and red indicate levels of energy of X-rays, from high to low. (courtesy: NASA/SAO/G.Fabbiano et al.)

I’m fascinated with the dynamics of the universe. I want to find out how cosmic rays accelerate to super-high-energy levels, and what role these processes played in the formation of the universe. I’m also hoping to reveal what role black holes played in the formation of galaxies throughout cosmic time.
There is a huge black hole at the center of each galaxy, and it’s becoming clear that there is a correlation between the mass of that black hole and that of its galaxy. It seems there is a co-evolution mechanism through which a black hole and a galaxy grow together. To do this, the massive black holes must have some impact on the gas from which galaxies grow, which is spread out over very much larger distances than the galaxy itself. We know that the black hole not only sucks material in, but it also ejects some fraction of this material in an energetic jet. It is probably this jet which transports energy outwards from the black hole to very much larger scales, heating the gas and controlling the formation of galaxies and galaxy clusters.
The formation of these galaxy clusters is also affected by dark matter and dark energy, giving us a way to probe these hidden components of our universe.

Q. What is the development roadmap for ASTRO-H?

Crab Nebula, a supernova remnant observed by Chinese and Arab astronomers in AD 1054. The technology developed to observe high-energy phenomena of the universe, such as supernova explosions. (courtesy: X-ray: NASA/CXC/ASU/J.Hester et al.; Optical: NASA/ESA/ASU/J.Hester & A.Loll; Infrared: NASA/JPL-Caltech/Univ. Minn./R.Gehrz)

We are aiming for launch in 2014, and are currently at the stage of detailed design. Development is going smoothly. However, as I mentioned earlier, we plan to equip ASTRO-H with the most sophisticated instruments, so we must test them every way we can think of before launch. For example, we’ve put them in a balloon that climbs to an altitude of almost 40 kilometers. We cannot overlook even the smallest defect.
We are now collaborating with scientists in other fields to apply ASTRO-H’s gamma-ray imaging technology, because it allows us to accurately determine the source of gamma radiation, by measuring its direction, intensity and distribution.
The gamma-ray camera may make it possible to pinpoint the location of cancer with just one examination by measuring multiple gamma-ray lines from tracer drugs. Such spin-off applications are part of the verification process. Reliability can be improved if we can apply mass-production processes to building instruments for space use.

Q. The X-ray microcalorimeter on the X-ray astronomy satellite Suzaku, which was launched in 2005, failed shortly after launch. How has that lesson been applied on ASTRO-H?

We review all causes of failures on past satellites, including Suzaku, to ensure that the same mistakes never happen again. In the case of Suzaku, the microcalorimeter failed because liquid helium, which was its cooling agent, vaporized in unexpected conditions after launch. ASTRO-H will also carry a microcalorimeter. We are modifying the design for higher reliability, making sure that the helium does not vaporize, and that, even without helium, the instrument will still be able to conduct observations.
Also, we have asked experienced scientists in Japan and abroad for advice. The key is to have a mix of expertise in various fields, from space to elementary-particle experiments and low-temperature experiments. We always remind ourselves to be humble and open to learning. We avoid making easy assumptions, and intentionally try to maintain a sense of tension when we are working.

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