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The Sun in Hydrogen Alpha light with Major Prominence
The Sun appears as a bright featureless disk, but if you have a good telescope with the right filters, you can actually see much more activity on the Sun. There are dark sunspots on the surface, and prominences leaping up from Sun. When we see prominences face on, they look like cooler lines on the surface of the Sun. These are known as filaments. And then when we see them side on, they’re prominences.
A solar prominence is a bright loop of material that extends up from the surface of the Sun. They start at the Sun’s photosphere, and rise up into the corona following magnetic field lines. The Sun’s corona is made up of extremely hot ionized plasma, but prominences are cooler, more like the temperature of the corona – up to 20,000 kelvin. A prominence can rise up in a single day, extending for thousands of kilometers and lasting for months. But the largest prominence ever observed was 350,000 kilometers long. A single prominence can contain hundreds of billions of tonnes of solar material.
Prominences can turn into coronal mass ejections when the magnetic field lines snap and reform. A coronal mass ejection contains plasma heated to tens of millions of degrees, with particles accelerated to nearly the speed of light. A single mass ejection can release 100 billion kg of solar material, and can create beautiful auroras when they interact with the Earth’s atmosphere.
The entire length of a typical solar prominence can stretch from the photosphere up to the corona. Like the corona, a solar prominence is made of plasma. However, prominences are much cooler.
These large features can sometimes last for many months, during which lengthy observations can be carried out by observatories. SOHO or Solar and Heliospheric Observatory, a joint project of the European Space Agency (ESA) and NASA, is one observatory that has made extensive research on sun-related phenomena including solar prominences.
Other observatories are the two STEREO (Solar TErrestrial RElations Observatory) satellites, which have captured magnificent images of solar prominences since their launch in October 2006. In one particular event, the sun ejected a solar prominence which lasted for approximately 30 hours. This enabled the two satellites to capture several views of the event.
As the two satellites, dubbed ‘ahead’ and ‘behind’ move closer to the Sun, scientists hope to unravel more secrets and obtain more information about these bright, magnificent features. Until then, let’s enjoy the amazing images, videos, and time-lapse sequences of solar prominence occurrences from these awesome observatories.
References:
NASA Earth and Space Science Explorers
NASA Sun Earth Day
About Fraser Cain
Fraser Cain is the publisher of Universe Today. He's also the co-host of Astronomy Cast with Dr. Pamela Gay.
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