Alan Friedman tells us
the Story of the Sun
Appearing like scenes from science fiction, astrophotographer Alan Friedman shows us the unexpected portraits and personalities of our local celestial body, the Sun.
Alan Friedman is an astrophotographer focused on our neighborhood star, the Sun. An incredibly dynamic subject, the Sun’s features change from day to day and sometimes hour to hour, radiating energy at all wavelengths. Unlike dim and harder to image galaxies and nebulae, the sun is a perfect subject for urban, backyard observation. Like a keen photojournalist, Alan creates unusual and compelling imagery to tell the story of the sun while surprising us with its ineffable beauty.
Employing a variety of filters for both diagnostic and aesthetic reasons, Alan showcases the incredible complexity of the solar chromosphere, its massive sunspots, arching prominences, and dancing filaments. With this diverse palette of tools, Alan paints a compelling portrait of his favorite celestial subject and brings an excitement for science to a wide and diverse audience.
While Alan’s work has been featured in NASA’s Astronomy Image of the Day and various online media, we’ve asked him to share the story behind some of his favourite public and personal imagery.
↥ Sometimes a morning with the sun can be ho hum and sometimes it is something else completely. This was a good day to be looking. In this hydrogen alpha portrait, the sun is peppered with (count ‘em) nine active sunspot regions.
Each sunspot in this active region is larger than the earth with a magnetic field that harbors energy capable of hurling M-class solar flares. But the big story on this day was the massive hedgerow prominence at the upper left edge of the sun. This massive arch of hydrogen plasma extends more than 55,000 miles (seven earth diameters) above the solar surface.
↥ The sun imaged in CaK, a spectral band 2.2 angstroms wide, centered at 393.37nm.
The Ca-K line is found at the short end of the visible spectrum - where blue light meets ultra-violet at the very limits of human perception. When I look through the Ca-K telescope, I see nothing. The yellowing of my eye’s lens blocks the violet light and renders the detail invisible.
Fortunately, my camera is much more sensitive at this wavelength and uses a black and white sensor. All color is applied afterwards while processing the image. I experiment with tonality, as sometimes a negative image increases contrast and makes the structure more three-dimensional. Since the sun radiates energy in all colors, I select a unique palette for each image, to add visual interest and to create an emotional connection with the viewer.
↥ Grand sunspot 2192 from October 19-27, imaged in CaK - a spectral band 2.2 angstroms wide, centered at 393.37nm.
I have been fortunate to have use of a very fine Ca-K telescope loaned to me by an astronomy friend. The Ca-K line shows activity in the solar chromosphere occurring just below the solar atmosphere seen in Hydrogen Alpha. The appearance of the chromosphere is quite different at this spectral line, with active sunspot regions shown vividly. In this triptych, a very large active region is shown from different perspectives as it rotates with the sun over the course of a week.
↥ Sun in two wavelengths, October 23, 2014
These two images are recorded through two different filters, taken within minutes of each other. The yellow image is captured through a simple white light filter, showing how the sun would appear to our naked eyes if we could reduce the intensity by a factor of 1000 and observe it safely. This is the photosphere – the surface of the sun, peppered with a number of small sunspots and one massive active region.
The orange image shows the sun’s chromosphere (the sun’s atmosphere) which is the layer just above the photosphere. A narrow band hydrogen alpha filter is needed to see the details of the chromosphere – the surface texture, hot plage areas surrounding the active regions (they appear black here), the prominences arching off the edge of the sun and the filaments – long stretches of hydrogen plasma, which are actually prominences seen against the disk of the sun. In this image, the tonality is inverted, rendering the cooler areas white and the hotter areas dark. The centers of the sunspots, which are black in the upper image, are white in the Ha image.
↥ Close-up of active region 2192 in collaboration with Randy Shivak
Randy captured this data with his home-built 9" refractor telescope in excellent conditions from his observing site in Phoenix, AZ.. He shared the raw file and allowed me the privilege of processing this excellent data into the final image above. This massive sunspot group (the largest in many decades) was recorded in full spectrum light. It is the same view we might see with our eyes – if we could look at the sun safely from a much closer vantage point than earth. The photosphere of the sun at high magnification shows granulation caused by convection currents below the surface. Each of these granules is about the size of Texas.
↥ For a stretch of two months on either side of the winter solstice, solar observing is not possible from my backyard observatory. The sun is low in the sky, blocked by trees and houses surrounding me. The seeing (air stability) is bad, affected by a stationary jet stream and heat escaping from rooftops nearby. And the lake effect weather brings almost constant clouds from late October to February.
I always save unprocessed data from summer to give me work to complete during this winter hibernation. By early spring, I am itchy to get back outside and collect new material. This image was an early season capture. The atmospheric stability was exceptionally good that morning, and the image shows a wealth of fine detail across the disk and at the edge of the sun.