Astro-E Scientific Objectives
The science to be explored with Astro-E includes:
1. Hot plasmas in cluster galaxies
Tremendous energy emerges in X-rays from the most active and hot
regions of the Universe. In a cluster of galaxies, thousands of
galaxies are embedded in hot plasmas from 10 to 100 million
degrees. The mass of hot gas in the X-ray band is more than three
times larger than the mass of visible component of the galaxies.
X-ray observations are critical to examine the physics of cluster of
Five times more mass than "visible" mass (sum of galaxies
and the hot gas) is required to bind such hot gas. This is called
"invisible mass" or "dark matter."
2. Evolution of the universe
The high resolution spectrometer will reveal the atomic abundance
and physical status of the hot gas with one order better accuracy than
previous experiments. Based on the observations of the gas dynamics it
is expected to study the formation of galaxies and the cluster
galaxies. This will provide us with clues to the evolution of the
Each element has its own characteristic energy of emission
line. Observed line energy and the intensity indicate the atomic
abundance, ionization states and the ionization temperature.
The motion of a gas is derived from the Doppler shift of the
observed line emission.
3. Accretion onto black holes
It has been well know that the gravitational energy of accretion
matter onto compact objects, such as neutron stars and black holes, is
released by the strong radiation in X-rays. The high resolution
spectrometer and the CCD cameras on the focal plane of Astro-E X-ray
telescopes are capable of detecting the velocity of accretion
matter. This tells us about the mass of black holes and the geometry
ASCA found many active galactic nuclei harbor such black holes.
With better sensitivity, Astro-E will discover and examine those
objects farther away, or hidden in thick clouds.
Apparent wave length becomes longer than the intrinsic, when the
X-ray is emitted from the region of strong gravitational field around
4. Acceleration of high energy particles
On the ground, extremely high energy cosmic ray particles have been
detected. The highest energy discovered so far is 16 joule per
particle. 1 Joule corresponds to the heat needed to warm up 1 gram of
water, by 4 degrees C .
In the Universe, there should be huge accelerators to produce such
high energy particles. We want to find the origin, mechanism, and site
of such high energy particle acceleration from the broad band X-ray
and gamma-ray spectra observed with the combination of HXD and focal
plane detectors of Astro-E mission.
ISAS/JAXA Department of High Energy Astrophysics
Last Modified: Sunday, 05-Oct-2003 20:09:44 JST