How to study the cosmos

In the beginning, astronomy was made with the use of optical telescopes, such as with Galileo's refractor and Newton's reflector telescopes. Although they were versatile and practical, such tools were limited and did not allow the study of "deep space". Over time, improvements were made, so that today there are several optical telescopes that can capture images at distances in the order of billions of light-years (like Hubble).

Light year is a unit of distance, characterizing how much light (with its speed of 300,000,000 m/s) travels in an interval of one year. When the night sky is glimpsed, what you observe is the past. Consider a star at a distance of 5,000 light-years from Earth. The light of such a star takes 5,000 years to reach Earth, so that when it arrives, this light is already "dated" from 5,000 years ago. Heaven is, in a way, a "time machine".

The electromagnetic spectrum consists of waves of radio, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays (the order shown is from the least energetic to the most energetic range). In order to study the Cosmos with greater emphasis, the exclusive use of optical telescopes is not enough. There are many celestial bodies that do not emit radiation in the visible light range, which make them "invisible" to optical instruments like Hubble.

There are currently other types of telescopes, such as radio telescopes, X-ray telescopes and gamma-ray telescopes. Radio telescopes, instead of using radiation (light) in the visible spectrum range, use the range of the spectrum corresponding to radio waves. When they receive the radio waves, the radio telescopes collect the data, direct them to an amplifier, and then transmit them to a computer, where they will be analyzed. The presence of these telescopes is very recurrent in films, in which huge sets of radio telescopes, called interferometers, are shown. As the name implies, X-ray telescopes analyze the radiation presented in the range of the X-ray spectrum, while gamma-ray telescopes analyze the radiation presented in the gamma-ray spectrum. The study of these more energetic radiations is of paramount importance for the understanding of celestial bodies such as pulsars and quasars.

One of the biggest problems scientists face in relation to ground-based telescopes is the turbulence ("blur") caused by the atmosphere. The particles present in the Earth's atmosphere absorb some of the radiation from the celestial bodies and re-emit them in a different orientation, altering the original "path". To work around this issue, scientists have imposed on some powerful telescopes lasers, which simulate in the sky the brightness of extremely luminous stars, enabling the correct calibration of the instruments, thus correcting the turbulence.

One of the last instruments developed for the study of the universe is the Laser Interferometer Gravitational Wave Observatory (LIGO), a structure developed for the detection of gravitational waves. Gravitational waves are perturbations (ripples) in the fabric of space-time, having been predicted by the theory of general relativity. Such disturbances are difficult to detect, given their low interaction with matter; however, in 2015, LIGO made the first detection of gravitational waves, which were produced during the collision of two black holes.

It is conclusive that astronomy requires a variety of tools for the study of the universe, which is justified by its magnitude and complexity.

Photo 1: Hubble telescope

Photo 2: VLT telescope with its powerful laser

Photo 3: ALMA telescope

Reference material: "The Evolving Universe" (S. George Djorgovski)

Astrophysics for people in a hurry (Neil deGrasse Tyson)