NASA's Solar Dynamics Observatory (SDO) has taken the first clear images of huge ejections of plasma from the Sun's surface. The images were shown yesterday at the 216th American Astronomical Society Meeting in Miami by Alan Title of Lockheed Martin. The ejections are so powerful that they sweep over halfway across the star's face, and the ability to study them in such clear detail could help our understanding of how solar activity affects satellites orbiting Earth.

The $850m SDO was launched in February and it uses a suite of extremely sensitive instruments to make a wide range of measurements of the Sun. As such, the mission can chart solar disturbances from their origins deep inside the core of the star to their appearance on the surface and their rapid ejection into space. SDO started science operations on 14 May after a calibration period.

Four-telescope array

The SDO craft sits in a geosynchronous orbit, which enables the satellite to continuously observe the Sun and makes it easier to transmit data to a ground-based station. It carries three instruments, including the Atmospheric Imaging Assembly (AIA), which is an array of four telescopes that will observe electromagnetic radiation from the Sun over 10 different wavelength bands.

Although astronomers have already taken clear images of smaller coronal mass ejections – expulsions of plasma threaded with magnetic fields – the studies have never covered such a large scale. Indeed Title, principal investigator for the AIA, showed images of the mass ejections that are so large they travel over halfway across the Sun's face.

'Not rare at all'

Title says SDO scientists have now spotted four such ejections. "For the first time we can clearly see these huge ejections," Title told physicsworld.com. "What we have also found is that they are not rare at all."

The ejections are likely to travel around 500 kilometers per second and as a result astronomers have found it difficult to clearly observe such huge ejections. "All we could previously do is see just a blur of this phenomena," says Title.

Appreciating the Sun

Seeing events like this gives you a great appreciation of the Sun Alan Title, Lockheed Martin

Scientists will now try to understand how such huge ejections occur to provide an early warning system for satellites as well as planes that are flying over the poles, which are regions most affected by geomagetic storms. "Seeing events like this gives you a great appreciation of the Sun," says Title.

The SDO is the first mission in NASA's Living With a Star programme, which was established in 2001 to try to obtain a better understanding of how the Sun's activity can impact on life on Earth.