Radio Astronomy

December 17, 2020

Radio Astronomy

When you opened up your eyes and looked at the sky and see the twinkling stars and think where the light come from? That light has travelled across space for years, hundreds, thousands of years before entering your eyes.

What is Radio Astronomy?

Radio Astronomy is the field of Astronomy which study about the Radio frequencies.

When you listen to your radio, and use a mobile phone or watch TV, you are using a device which emits the radio waves. Radio waves are a form of electromagnetic radiation, like the visible light you are used to seeing with your eyes. The difference in radio waves is they have a longer wavelength and are lower in frequency than visible light. They also carry less energy. Visible light is good enough to help plants produce their own food through photosynthesis. Radio waves are weaker than this so we need electronic amplifiers to help us in boost their signal. Any electromagnetic with a wavelength greater than 1mm is radio wave.

Radio waves were first detected from the space in early 1930. After development of RADAR it led to improvement in antennas and electronics. Scientists has started to use this equipment to find Radio signals which are coming from the space, and then the science of radio astronomy was born.

How are Radio Waves produced?

All the matter around us is made up of atoms. And atoms are made up of sub- atomic particle.

When charged particles like electrons accelerates by changing their speed and directions it emits electromagnetic radiation. There are many form of electromagnetic Radiation which are detected by our scientists and well seen in EM spectrum.

The long wavelength, low frequency hence low energy form is called radio waves. Going up in frequency and energy the electromagnetic ( EM) spectrum comprises radio and microwaves, infrared waves, visible light, ultraviolet rays, X-rays and γ - or gamma rays.

Each type of radiation is produced by certain conditions. Astronomers can detect each type of radiation emission by using telescope on the ground. Like X- rays can only be detected by the telescope in space as the atmosphere absorbs and prevent them to reaching the Earth's surface.

We need to understand how they are produced. There are two basic forms of radio emission; thermal and non-thermal.

Thermal emissions are caused by the motion of charged objects such as molecules and atoms. As all matter has some heat energy stored in it, atoms vibrate, emitting electromagnetic radiation. The more energy stored, the more the atoms vibrate and the greater the amount of radiation emitted.

When a gas is heated the energy will eventually be enough to kick out one or more of the electrons orbiting an atom. The atom now ionised and has a positive charge while the electron is now free. As negative electrons move around in this high temperature, charged gas (called plasma) they continually interact with the positive charges. Because they are thus accelerating they emit electromagnetic radiation.

source- google

Another form of thermal emission is due to the spin of electrons as they "orbit" a nucleus. An excited electron loses energy by flipping it spin back to a more stable state. The radio wave emitted in this process always has a specific discrete wavelength. An electron in a neutral hydrogen atom, for example, produces radio waves of 21cm wavelength via this process. As hydrogen is the most abundant element in the Universe this 21cm hydrogen line was one of the first radio emissions detected from space and continues to be a key wavelength for astronomers to observe.

Non-thermal sources of radio waves include synchrotron radiation, in which electrons moving near the speed of light get accelerated in strong magnetic fields. Such conditions occur in very powerful sources such as quasars, active galactic nuclei and supernova remnants, the remains of massive stars that have exploded. Geosynchrotron emissions are a related process produced by pulsars, rapidly spinning neutron stars that are remnants of more massive stars. Masers or microwave amplification by the stimulated emission of radiation are similar to lasers but at short wavelength radio frequencies or microwaves instead of visible light. Natural maser sources are sometimes found in clouds of molecules in regions where stars are forming.

So now we will talk about the Radio telescopes.

A Radio telescope is designed to recieves the radio signal far from the galaxy. It has mainly three components

One or more antennas to collect the radio signals
2. Receiver and Amplifier to boost the least or weak radio signal to the measurable levels.
A Recorder, to keep records of the signals.

For example-

SKA ( square kilometres array) the biggest Radio Telescope is going to build till the end of 2027. SKA is making in two parts,antennas which is making in South africa and this time they are using many thousands of antennas to collect the radio signals far from the space and other one part is making in Australia.

It is the biggest telescope we have ever seen and will launch by 2027( approximately).

SKA will study About the dark ages and will also study about what happened before the big bang!!

Isn't it intresting?

SKA

Radio telescope