Welcome to the STEREO Learning Center

Coronagraphs

A Coronagraph is an instrument which studies the Sun's outer atmosphere, the corona. From Earth the corona is most easily seen during a total solar eclipse. It is also possible to cover the bright disk of the Sun with a disk to create a sort of mini-eclipse and allows us to see the Sun's fainter outer atmosphere. If we do this from space we do not have to worry about the bright blue sky which makes this harder to do from Eath's surface.

Each STEREO spacecraft has two coronagraphs which study the Sun from space. These two coronagraphs, which are part of STEREO's SECCHI suite of imagers, have different fields of view, using different sized occulting disks to allow us to see the faint corona at different distances from the Sun's surface.

The image is from STEREO SECCHI's Cor2 coronagraph on the Ahead spacecraft. The white circle shows the size and location of the Sun's surface. The color isn't "real". We color code the images so we can tell them apart quickly.

The main feature to notice in this image is a faint coronal mass ejection (CME). CMEs are huge magnetic eruptions which blast off the Sun and can affect us here on Earth.

Some images from the coronagraphs and the Heliospheric Imagers also show planets, stars, and even comets.

In addition, there are various strange looking features that are artifacts of the instruments. You can read more about those on our image artifacts page