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From Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory,
the moon blocked a little over 80% of the Sun's disk during last Thursday's solar eclipse.
ASKAP observations were made during the eclipse to study the effect of
the solar wind on compact radio sources ~5 degrees from the Sun.
The ionized plasma of the solar wind causes compact radio sources,
mostly distant galaxies, to twinkle, and while this effect is always present
it is much easier to study when the Sun -- a very strong radio source -- is blocked.
ASKAP undertook a series of ~2 minute observations with the the centre of the
field of view either 3 or 6 degrees from the Sun.
The images above show two snapshots during these observations, the top image
just before the eclipse began, and the bottom image near the maximum partial eclipse.
The left hand frames show the relative positions on the sky of the Sun (yellow), moon (grey),
and 36 ASKAP beams (red), with the beam in white used for imaging. (Although the
Sun lies well outside this beam, it is so bright that it can be imaged through
the sidelobes of the beam.)
The middle images show the ASKAP image with the position of the Sun marked in yellow
and the moon in grey. The right hand image is an image taken the same day of
the Sun at extreme ultra-violet (EUV) wavelengths by NASA's Solar Dynamics Observatory.
The close correspondence between the active regions seen in the EUV and the hot-spots
detected at radio wavelengths is apparent in the top image.
In the bottom image, most of these active regions are blocked by the moon, with only
one spot on the Sun's disk and two regions on the Sun's edges visible.
(Image credit: Emil Lenc)
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