National Astronomical Observatory of Japan

A Total Solar Eclipse Seen in X-rays


This video of a total solar eclipse was captured by the solar observing satellite HINODE. This day (March 19, 2007) a partial eclipse, where only a small portion of the Sun was eclipsed even at the maximum, could be seen from Japan-Sea side of Japan, but for HINODE it was a total solar eclipse.

Why Observe the Sun with X-rays?

The corona extending from the Sun out into space has a temperature over 1 million Kelvin. Because the light from the Corona is very weak, it can only be observed from the surface of the Earth during a total solar eclipse. But solar flares and coronal mass ejections, which can have a direct impact on our lives by causing malfunctions in artificial satellites and power transformer substations, originate from the corona. We can’t study these phenomena with the observational data from total solar eclipses, which only last a couple of minutes. So instead, we make use of the fact that the corona temperature is over 1 million degrees. Gas hotter than 1 million degrees emits X-rays; but gas cooler than 1 million degrees doesn’t emit X-rays. Other than the corona, there aren’t areas in the solar atmosphere hotter than 1 million degrees, so by observing X-rays it is possible to continuously observe just the corona. Actually the X-rays emitted by the Sun are absorbed by the Earth’s Atmosphere, so observations employing an artificial satellite are required.

When a total solar eclipse is observed in X-rays, even from the beginning we can only see the corona, so we don’t see a mysterious dynamic change like is seen from the Earth. But total eclipse data are very important for investigating the performance of the telescope.

Text by: Masumi Shimojo (NAOJ Chile Observatory)
Translation by: Ramsey Lundock (NAOJ)

Video Data

ObjectThe Sun
TelescopeSolar Observing Satellite HINODE
InstrumentX-Ray Telescope
WavelengthSoft X-rays (several Å to 100 Å)
Exposure4 seconds
Date11:55 March 19, 2007 (Japan Central Standard Time)

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