The gamma-ray sky map produced using Fermi Space telescope observations from August 2008 to May 2021. Credit: D. Carlos, L. Siconato, R. de Menezes, R. Nemmen (Univ. de Sao Paulo).

The Black Hole Group is part of the Fermi LAT collaboration. The Fermi collaboration is a group of scientists that uses observations taken with the Fermi Gamma-ray Space Telescope, a telescope devoted to the observation of the gamma-rays:  the highest-energy form of light, and uses this to study different astronomical sources. Among the sources studied are, for example, black-hole systems, supernova remnants, and merging neutron stars.

Now, the Fermi telescope was launched on 11 June 2008, and until today it is still capturing high energy photons and giving us a large amount of data about the universe. As a way to better visualize the gamma-ray sky, Douglas Carlos, Lucas Siconato, and Raniere Menezes produced the above image.

To produce this, we used data with sources from all the sky collected by the Fermi telescope, with the beginning of the observation being in August 2008 and the ending in May of 2021. With this data, our group members did a split using the photon energy as a criterion. The first energy range was chosen to be from 100MeV to 1GeV. The second one was from 1GeV to 10GeV, and the last one has a range initiating in 10GeV and ending in 1TeV. Each one of these energy ranges has been assigned to a color from the RGB system that resulted in this incredible image when put together! When a source is mostly red, we have most of its photons belonging to the first energy range talked above. When a source is mostly green, its photons majority belong to the second energy range discussed, while a source that is mostly blue has the majority of its photons belonging to the last energy range. Beyond the fact that the sky seen in gamma rays harbors information from the light that is billions of times more energetic than the visible one, an image done in the configuration discussed above gives us information about each one of the sources’ emissions using colors. The colors make the image work like a map of the sky!

To understand a little better what you are seeing, you have to know that: each one of the points present in this image is a source whose Fermi Space Telescope has observed gamma light in the last 13 years. The central and very bright part is the galactic plane. It has a lot of diffuse emission of gamma rays, as one can see by the absence of point sources in this part. Another interesting feature that is possible to see is the Fermi bubbles. These bubbles have as an origin the central part of the Milkyway (faint blue glow at the center of the image) and are expanded to about 25 thousand light-years above and below the galactic center.

Now, an approach to think about this image is the one that we realize that each one of these sources has its own scientific potential and keeps precious information about nature and how it works! Also given enough time, it should be studied and understood. However, a complementary approach to think about it (and that someone would hardly say that it is not right) is to just realize how pretty and incredible the gamma-ray sky can be! Right?

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