From the May 2013 issue

When the Sun produces a coronal mass ejection, is the blast of sufficient force to alter our star’s path through the cosmos? Do these eruptions significantly perturb our solar system?

Bill Brown, Rolling Meadows, Illinois
By | Published: May 28, 2013 | Last updated on May 18, 2023
Coronal mass ejections
When the Sun blasts off radiation and material, it creates what’s called a coronal mass ejection (CME). The radiation from a CME can affect planets and satellites in its path, but it doesn’t alter our star’s motion. // SOHO (ESA/NASA)
The Sun sheds material in two ways: a constant solar wind due to an outward expansion of its extremely hot upper atmosphere (or corona) and less frequent explosive events called “coronal mass ejections” (CMEs). The Sun is made of plasma (hot ionized gas) and magnetic fields; the interaction between the two can cause a buildup of magnetic energy. Basically, plasma motions stress the fields, causing them to become highly sheared or twisted (similar to twisting rubber bands), which can lead to an eruption like a CME (as if the rubber bands snap).

Although CMEs are incredibly energetic, the force they exert on the Sun is small; therefore, they have no measurable effect on our star’s movement through the Milky Way Galaxy. This type of explosion is inherently different from an ejection of a solid object, like a bullet, from another solid object, like a gun, which produces significant recoil.
The solar wind shapes the boundary of our solar system, and we call this region the heliosphere. CMEs, which travel far (sometimes to the edge of the solar system), can perturb the relatively consistent flow of the Sun’s wind as they pass by. During a CME’s long journey through interplanetary space, it can provide a higher dose of radiation than normal to objects, such as planets and satellites, that lie in its path.

CMEs perturb our solar system in those ways, but these local, short-term disturbances do not permanently change the space environment. The Sun is extremely dynamic, and its domain is vast; because our solar system is susceptible to the Sun’s variations, there is an entire scientific field, called space weather, dedicated to studying such phenomena.

Holly Gilbert
NASA’s Goddard Space Flight
Center, Greenbelt, Maryland