The sun through the eyes of radio telescope ALMA

A complex of radio telescopes, the ALMA is one of the most valuable tools available to modern astronomers. Its characteristics allow us to look into things like protoplanetary disks, inaccessible to most of the other observatories. That is why ALMA is so often mentioned in the context of the discovered exoplanets. But it can be used for observation, where closer objects. For Example, The Sun.

A map of the whole disc of the Sun was also made with a single ALMA antenna, using a technique called fast-scanning, at a wavelength of 1.25 millimetres. The accuracy and speed of observing with a single ALMA antenna make it possible to produce a map of the entire solar disc in just a few minutes. These maps show the distribution of temperatures in the chromosphere over the whole disc at low spatial resolution and therefore complement the detailed interferometric images of individual regions of interest.


The sun at the wavelength of 1.25 mm.

ALMA capabilities allow it to detect on the surface of our star items, which are inaccessible to other tools (not to mention the fact that not every telescope is in principle possible to direct the Sun). Recently, astronomers first used it to study sunspots. It has been studied at wavelengths of 1.25 and 3 mm. The observation results met expectations: the researchers obtained images of the structures in the Central part of the spot.

This ALMA image of an enormous sunspot was taken at a wavelength of 1.25 millimetres. Sunspots are transient features that occur in regions where the Sun’s magnetic field is extremely concentrated and powerful. They have lower temperatures than their surrounding regions, which is why they appear relatively dark. These observations are the first ever made of the Sun with a facility where ESO is a partner. They are an important expansion of the range of observations that can be used to probe the mysterious physics of our nearest star.  


Sunny spot at a wavelength of 1.25 mm.

This ALMA image of an enormous sunspot was taken at a wavelength of 3 millimetres. Sunspots are transient features that occur in regions where the Sun’s magnetic field is extremely concentrated and powerful. They have lower temperatures than their surrounding regions, which is why they appear relatively dark. These observations are the first ever made of the Sun with a facility where ESO is a partner. They are an important expansion of the range of observations that can be used to probe the mysterious physics of our nearest star.


Sunny spot at a wavelength of 3 mm.

As you can see, the images vary. The fact that at shorter wavelengths it is possible to see the deeper layers of the Sun. Thus, the image on the wave of 1.25 mm corresponds to a layer that lies deeper and closer to the photosphere (the part of the Sun that radiates energy and that we actually see when we look at the sky) than the layer an image is obtained at a wavelength of 3 mm.

This image of the entire Sun was taken in the red visible light emitted by iron atoms in the Sun’s atmosphere. Light at this wavelength originates from the visible solar surface, the photosphere. A cooler, darker sunspot is clearly visible in the disc, and as a visual comparison is shown alongside the image from ALMA at a wavelength of 1.25 millimetres. The full-disc solar image was taken with the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO).