Visible light shows only a small fragment of the universe. Astronomy also deals with other areas of the electromagnetic spectrum.
Atacama Large Millimeter/submillimeter Array (ALMA)
By ESO/José Francisco Salgado link [CC BY-SA 4.0 license]
We see a universe of stars in the dark at night. Everything that reaches our eyes, however, is only a fraction of the entire cosmos. The image of the universe created over the centuries contained only elements visible to the human eye. In the nineteenth century, it was realized that visible light is only part of the wide spectrum of electromagnetic radiation that the cosmos produces. This spectrum includes all kinds of radiation from low-energy radio waves, through microwaves, infrared, visible light, ultraviolet, X-rays and energy-rich gamma rays. Astronomy up to the twentieth century was the science of visible light. To understand the universe better, all spectral ranges must be examined. For this purpose, special devices are constructed that record the remaining parts of the spectrum.
A diagram of the electromagnetic spectrum
By Inductiveload, NASA link [CC BY-SA 3.0 license]
The first step beyond visible light astronomers made in the direction of infrared, or wavelengths slightly longer than visible light. They are of great importance in the study of the birth of stars because they penetrate the clouds of gas and dust in which stars are born. The Spectral Space Telescope (SST) is next to the Hubble telescope a wonderful complement to what we observe visually. Below is a picture of the Andromeda galaxy (M31) taken by the infrared Spitzer Telescope compared to visible light.
Three Faces of Andromeda
By NASA/JPL-Caltech/K. Gordon (University of Arizona) link [Public domain]
Radio waves, longer than the infrared, became the object of astronomers interest at the end of the 19th century. In 1932, Karl Jansky, an American engineer, researched the noise in radio receivers and discovered that he had an extraterrestrial origin. After subtracting the radio waves emitted by the Sun and storms on Earth, he came to the conclusion that the emission remains from the Milky Way. This radiation is the strongest in the center of the Galaxy, towards the constellation Sagittarius. Radioastronomy has been developing very dynamically since the early 1950s. Discovered pulsars - rotating remains of dead stars and quasars - very active nuclei of distant galaxies. A microwave cosmic background radiation was also observed, i.e. a remnant of the Big Bang in which the universe was born. Most radio telescopes are huge metal cannons that collect distant cosmic signals. In order to get better images of radio radiation, astronomers combine a lot of radio telescopes, creating one giant layout like the last photo of the article. Radio waves easily reach the Earth's surface. However, radiation shorter than visible light is almost completely absorbed by the Earth's atmosphere. Therefore, the devices that examine them must be in space.
Extreme ultraviolet image of the sun taken by SDO on March 30, 2010
By NASA/Goddard/SDO AIA Team link [Public domain]
Above picture of the Sun in ultraviolet. It allows astronomers to study very hot cosmic objects, such as gas around ordinary stars and very hot stars whose evolution runs faster than our Sun. Such observations are carried out by the FUSE (Far Ultraviolet Spectroscopy Explorer) space telescope. Ultraviolet rays are shorter than X-rays. They allow exploring phenomena as violent as supernova explosions. The Chandra space telescope explores the universe in this radiation band. However, the most energetic radiation is gamma. In it, the most distant and mysterious objects of the universe are visible, such as black holes or neutron stars. They are examined by a GLAST telescope (Gamma-ray Large Area Space Telescope). The last century has opened the eyes of astronomers to the new invisible universe. Thanks to this, the list of cosmic objects known to man has become very long. Unfortunately, we can watch space only in the visible range.
Very Large Array (VLA)
By John Fowler link [CC BY-SA 2.0 license]
Greetings to lovers of Astronomy!
Sources:
Electromagnetic spectrum
Radio telescope
Very Large Array
Atacama Large Millimeter Array
Spitzer Space Telescope
Far Ultraviolet Spectroscopic Explorer
Chandra X-ray Observatory
Fermi Gamma-ray Space Telescope
and my knowledge...
