Copyright: SOHO (ESA & NASA)
This eerie coloured orb is nothing less than the life-giver of the
Solar System. It is the Sun, the prodigious nuclear reactor that sits at
the heart of our planetary system and supplies our world with all the
light and heat needed for us to exist.
To the human eye, the Sun
is a burning light in the sky. It is dangerous to look at it directly
unless some special filtering is used to cut out most of the light
pouring from its incandescent surface.
However, to the electronic eyes of the Solar and Heliospheric Observatory (SOHO), the Sun appears a place of delicate beauty and detail.
SOHO’s extreme-ultraviolet telescope
was used to take these images. This telescope is sensitive to four
wavelengths of extreme-ultraviolet light, and the three shortest were
used to build this image. Each wavelength has been colour-coded to
highlight the different temperatures of gas in the Sun.
The gas
temperature is traced by iron atoms, where rising temperature strips
increasing numbers of electrons from around the nucleus.
An iron
atom usually contains 26 electrons. In this image, blue shows iron at a
temperature of 1 million degrees celsius, having lost 8 or 9 electrons.
Yellow shows iron at 1.5 million degrees (11 lost electrons) and red
shows iron at 2.5 million degrees (14 lost electrons).
These atoms
all exist in the outer part of the Sun’s atmosphere known as the
corona. How the corona is heated to millions of degrees remains the
subject of scientific debate.
The constant monitoring of the Sun’s atmosphere with SOHO, and with other Sun-staring spacecraft like the Solar Dynamics Observatory and Proba-2,
is allowing solar physicists to build up a detailed picture of the way
the corona behaves. This gives them insight into the physical processes
that give rise to the corona and its behaviour.
Source: ESA/Space Images
