The Corona

solar eclipse photo showing coronaThe outermost layer of the Sun is called the corona or the crown. The corona is very thin and faint and is therefore very difficult to observe from the earth. Typically, we observe the corona during a total solar eclipse or by using a coronagraph telescope which simulates an eclipse by covering the bright solar disk.

The corona also emits energy of many different wavelengths, from long wavelength radio waves, to short wavelength X-rays. By designing special telescopes we are able to look at the corona in many different ways. Below is a picture of X-rays coming from our Sun taken by an X-ray telescope on the Yohkoh satellite currently orbiting the earth.

x ray image of Sun

The X-rays we see all come from the corona, the outermost layer of the Sun's atmosphere. But not all the corona emits the same amount of X-rays. The most visible structures are the loops and arches around the active regions. We may also see much smaller regions called "bright points." (The name gives away their appearance.) Movies made from X-ray pictures show that the corona is a very stormy place, constantly changing and erupting. In X-ray images we may also see areas called "coronal holes," regions of low brightness at the north and south poles.

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Image Credits:
Solar Eclipse: HAO/NCAR
X-Ray Sun: Yohkoh Science Team