Touching the Universe
The Silhouette of a Radio Telescope against the Carina-Sagittarius Arm of our Milky Way Galaxy.
About the Radio Telescope in this photo:
The 15m dish at Hartebeesthoek Radio Astronomy Observatory, built as the initial eXperimental Development Model (XDM) for KAT (Karoo Array Telescope), the first phase of MeerKAT and the SKA SA – Square Kilometre Array - South Africa.
At the time that I took this photo of the Prototype, the first 64 Radio Telescope Dishes were already up and running on location at Carnarvon in the Northern Cape.
Why do we use Radio Telescopes for Astronomy?
The human eye can only see about one ten trillionth of the Electromagnetic Magnetic Spectrum of light (between 400-700nm, with diminished sensitivity at both ends). Radio Telescopes can detect a much wider range of Electromagnetic Radiation including Radio waves, Microwaves, Terahertz waves, Infrared, Visible light, Ultraviolet, X-rays, and Gamma rays).
About the Milky Way:
The Milky Way Galaxy is estimated to have over 400 billion stars. Stars are suns, and just like in our Solar System, many of the stars have planets and moons. Our sun is a middle aged Yellow Dwarf star, located in the Orion Arm (or Orion Spur) of the Milky Way Galaxy. It’s a minor side spiral arm, located between two larger arms of the Milky Way Galaxy's spiral. The Milky Way is merely one mid-sized barred spiral Galaxy, amongst over 100 billion other Galaxies in the observable Universe. When we look up at the night sky from Earth, we see a glimpse of the Carina–Sagittarius Arm of the Milky Way Galaxy. It takes about 250 million years for the Milky Way Galaxy's spiral arms to complete one rotation.
“The size and age of the Cosmos are beyond ordinary human understanding. Lost somewhere between immensity and eternity is our tiny planetary home." - Carl Sagan.
The known Universe is estimated to contain over One Billion Trillion stars (1 000 000 000 000 000 000 000).