Of Sunspots and Solar Eruptions

I was initially going to talk about some fascinating images of sunspots showing their structure in a way never seen before, but the Sun made an announcement on Tuesday that took solar astronomers by surprise and has moved to the top of the list.

On June 7th there was a huge eruption on the surface of the Sun, very different from anything observed before.


Coronal Mass Ejection, June 7, 2011 - NASA SDO

The above image shows this huge prominence. This gives you an idea of its size and how much of the Sun it covered, but check out the video below to see how dynamic this event was.


The video shows the eruption as seen by the Solar Dynamics Observatory at two different energies. The second, or greenish-blue image is looking at shorter wavelengths, or higher energy emissions. The other images with the disk in the center (an instrument called a coronagraph) are from the Solar and Heliospheric Observatory’s (SOHO) LASCO coronagraph and STEREO’s (Solar Terrestrial Relations Observatory). If you watch the video closely you will see material falling back to the surface of the Sun creating ejecta as they land.  For more information and more complete videos with descriptions go to The Sun Today.


Now on to something more sedate – sunspots.


The Sun is a very dynamic object, as evidenced by the images above, but from our place in the Solar System it seems pretty quiet and stable. The surface of the Sun is a frenzy of activity and this is no different when you approach the cooler sunspots that dot its surface.


Sunspot with Earth reference.  Image courtesy of the Institute for Solar Physics

Work done by Göran B. Scharmer, Vasco M.J. Henriques, Dan Kiselman, (all from the Institute for Solar Physics of the Royal Swedish Academy of Sciences and the Department of Astronomy at Stockholm University), and Jaime de la Cruz Rodríguez (University of Oslo) has shown that the structure of the sunspot is a heaving mass of cells or filaments almost 1200 miles or about 2000 km long and about 90 miles (150 km) wide, which can be seen in the above image. The brighter, hotter filaments are areas of hot matter that is upwelling at speeds of 6,600 mph (10,800 kph), while the darker filaments are sinking at speeds of about 2,200 mph (3,600 kph).


The image below shows the speed of the sunspot’s filaments as measured by Doppler shift. The red filaments are moving away, or sinking while the blue ones are rising and moving toward the surface.


Sunspot filaments showing relative velocities. - Image courtesy of the Institute for Solar Physics

For more information and images visit the Institute for Solar Physics


These images should humble us, as they are indicative of how much we don’t know about the cosmos, let alone our nearest star.  There is so much to learn…


Till next time,


RC Davison

Leave a Reply