Sunspots, such as those on the right in the image above, can often been seen as dark regions in the photosphere of the Sun. Sunspots often lie below very bright regions in the Sun's upper atmosphere, the corona.
X-ray telescopes are able to view these bright features in the corona. The X-ray image on the left shows several of these active regions. Can you see the related sunspots?
Active regions are born when the magnetic field of the Sun pokes out into the corona. Hot gas is visible near the magnetic field, making bright loops. Active regions may last for several weeks or even several months.
Image Credit: Yohkoh Science Team