The Sun in H-alpha light




Nuclear fusion of Hydrogene into Helium in the core of the sun heats the inner 500 000 km radius of the sun to temperatures up to 10 000 000 °C. That heat radiates outwards, through the convective zone and heats the Photosphere, the 500 km thick visible layer of the Sun, to a temperature of about 5500 °C, visible from Earth as yellow light. That heat radiation masks most details on its surface.


Details are revealed when imaging at a narrow wavelength band centered around 6562.8 Å, the H-alpha ray. That light is emitted by hydrogen atoms, by far the most common element in the Sun. When electrons within those atoms absorb energy, they rise to a higher energy level and when they cascade back to their original orbits, they release that energy as a crimson light at 6562.8 Å wavelength.


My imaging setup:

- The sun light enters the telescope through an ERF filter (Energy Rejection Filter), which removes the unwanted hot infrared spectrum (which would melt the whole setup!).

- An H-Alpha filter lets only that 6562.8 Å wavelength through.

- A dedicated webcam then records the image obtained.






The Sun imaged in H-Alpha wavelength on 30 May 2022 from Singapore. Earth is pasted at scale in the upper right corner !

In this image, notice the granular aspect of the surface of the sun, bright where hot gas from inside the Sun rises to reach the surface. As the gas cools down, it slides down into the Sun's interior and that region appears dark. There are some dark filaments, huge arcs of plasma (electrified gas) in the Sun's atmosphere. They look dark because they are not as hot as the Sun's surface behind them. When they appear on the edge of the Sun, they appear as bright prominences on the black background of outer space.

There are 2 sunspots in this image. Sunspots form when concentrations of magnetic field from deep within the sun well up to the surface. They appear dark because they are cooler than their surroundings at around 3500 °C next to 5500 °C regions.

This photograph is a mosaic of 77 images. Each image is a stack of 900 frames extracted from a 15s movie. 175 Gb of data was captured for an original mosaic of 10 000 pixel x 10 000 pixels, reduced to 3 000 pixels here.





Zoom in Sunspots group 3023 imaged from Singapore on 30 May 2022.. Earth is pasted at scale in the upper right corner !






Yes! The Sun rotates!

Below a GIF of 2 images taken 24 hours apart.

At the Equator, the rotation rate is 1 rotation in 24 days and it slows as we get closer to the poles where the rotation is about 1 rotation in 35 days.





Below a timelapse taken over 18 minutes on 26 June 2022.





Below an image taken on 26 June 2022.