What is a solar prominence?

How our Sun emits some fiery plasma, sometimes to the delight of eclipse watchers.
By | Published: October 31, 2016
On August 31, 2012 a long prominence/filament of solar material that had been hovering in the Sun’s atmosphere, the corona, erupted out into space at 4:36 p.m. EDT. Seen here from the Solar Dynamics Observatory, the flare caused an aurora on Earth on September 3.
NASA Goddard Space Flight Center
The Sun’s fiery hot sphere produces a variety of special features. Maybe the most intriguing is a so-called solar prominence. Astronomy enthusiasts, eclipse chasers, and Sun watchers talk about solar prominences all the time. So just what is a solar prominence, anyway?

Think of the Sun as a highly magnetic ball of gas. Following along magnetic field lines, giant loops of plasma can form that extend far outward into space from the Sun’s glowing “surface,” its photosphere. These loops of plasma are solar prominences, and they can measure many times larger than Earth’s diameter.

Prominences push out into the Sun’s thin, extremely hot atmosphere, called the corona. They radiate at lower temperatures than the corona itself. These prominences can last for days, sometimes even months, and are often associated with a very powerful surge of gas that flows outward in a giant solar “belch” — a coronal mass ejection that can light up Earth’s skies with an aurora and even interfere with our technology.

For solar observers, prominences are a joy. Of course to ever look at the Sun in any way, you need to do it properly and carefully. A solar filter that permits seeing prominences is a so-called Hydrogen-alpha (H-alpha) filter, which transmits the wavelength of light prominences give off.

If you have a telescope fitted with an H-alpha filter, you can see these tongues of reddish gas blasting above the Sun’s limb, and even watch them as they slowly change over minutes or hours. It makes an incredible way to appreciate our home star, the source of all the energy that makes life possible on Earth.