SOHO sees solar eruptions and comet collision
Posted: October 25, 2001

Photo: ESA & NASA
A very bright Sun-grazing comet was discovered by the SOHO spacecraft while a pair of coronal mass ejections were heading for Earth, following two solar explosions on Monday.

The last one of the eruptions can be seen in the above image, and the comet's tail can be seen growing as it approaches the Sun. Solar radiation heats the comet, causing an outgassing of water molecules and dust. The dust scatters sunlight at visible wavelengths, making the comet bright in LASCO instrument images from SOHO. The water molecules are broken down by ultraviolet light into oxygen and hydrogen atoms, and the hydrogen atoms interact with the coronal plasma.

In these images, the shaded disk is a mask in the instrument that blots out direct sunlight. The white circle added within the disk shows the size and position of the visible Sun.

In just six years, SOHO has discovered more than 365 comets, making it the most prolific comet finder in the history of astronomy.

The Solar and Heliospheric Observatory (SOHO) is a joint project of NASA and the European Space Agency.