The Yohkoh Space Observatory
The Yohkoh satellite, an observatory
for studying X-rays and gamma-rays from the Sun, was launched
from Kagoshima, Japan (picture at right) on August 30, 1991.
Yohkoh is a project of the
Institute for Space and Astronautical Sciences, Japan;
Yohkoh (the spacecraft) was built in Japan, but the observing
instruments have contributions from the United States and from the
United Kingdom.
Why should the Sun make X-rays and gamma-rays?
The visible surface of the Sun is hot
- some 6,000 degrees, but that is not hot enough for X-radiation.
The photosphere actually appears dark in the Yohkoh
soft X-ray images, which show instead the extremely hot corona
that envelops the Sun and extends far out into space.
Yohkoh's main scientific objectives deal with finding
explanations for the solar X-ray and gamma-ray emission and the
interesting phenomena seen only in this kind of radiation.
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| The Mu-3SII rocket sending
Yohkoh into orbit. The launch site is at the southern tip
of Japan's southernmost main island, Kyushu, at the village of
Uchinoura on the Ohsumi peninsula. The Pacific Ocean can be seen
in the background.
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