ACTIVE GALACTIC NUCLEUS

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Context

Researchers from the Indian Institute of Astrophysics (IIA) have found evidence of an interaction between a radio jet emitted from a special kind of galaxy called Active Galactic Nuclei (AGN) and the surrounding interstellar medium. 

What is a Radio Jet?

A radio jet is material that is spewed from the centre of some galaxies almost at the speed of light and sends out strong radio waves.

About IIA

IIA is an autonomous research institute wholly funded by the Department of Science and Technology, Government of India. IIA conducts research primarily in the areas of astronomy, astrophysics and related fields. Headquarters are in Bengaluru.

Active Galactic Nucleus

AGN is an extremely bright central region of a galaxy that is dominated by the light emitted by dust and gas as it falls into a black hole.

Characteristics

The extremely luminous central region is emitting so much radiation that it can outshine the rest of the galaxy altogether. 

AGNs emit radiation across the entire electromagnetic spectrum, from radio waves to gamma rays. This radiation is produced by the action of a central supermassive black hole that is devouring material that gets too close to it.

A galaxy hosting an AGN is called an ‘active galaxy’. AGNs are the most luminous persistent sources of electromagnetic radiation in the Universe. 

Tyes of AGN

They are classified based on their observed characteristics. The most powerful AGNs are known as quasars, which give rise to extremely luminous galactic centres. A blazar is an AGN with a jet of light and energy that is pointed toward the Earth.

Galaxies

Galaxies are concentrations of stars, gas, dust, and dark matter. They come in a variety of shapes and sizes. Some are fated to collide, like the Milky Way and Andromeda.

Types

Astronomers classify galaxies into three major categories: elliptical, spiral and irregular. 

Their size varies from dwarf galaxies containing as few as 100 million stars to giant galaxies with more than a trillion stars.

Ellipticals

These account for about one-third of galaxies observed. They vary from nearly circular to very elongated. They possess comparatively little gas and dust, contain older stars and are not actively forming stars anymore.

The largest and rarest of these, called giant ellipticals, are about 300,000 light-years across. These are formed by the mergers of smaller galaxies. 

Spiral galaxies 

Spiral galaxies appear as flat, blue-white disks of stars, gas and dust with yellowish bulges in their centers. Spirals are actively forming stars and comprise a large fraction of all the galaxies in the local universe.

These galaxies are divided into two groups: 

1. normal spirals: 
2. barred spirals. the bar of stars runs through the central bulge. 

Irregular galaxies 

Irregular galaxies, which have very little dust, are neither disk-like nor elliptical. These galaxies are abundant in the early universe, before spirals and ellipticals developed.

How do Galaxies Form?

The appearance and make-up of galaxies are shaped over billions of years by interactions with groups of stars and other galaxies.  The early universe was filled mainly with hydrogen, helium, and dark matter, with some areas slightly denser than others. These dense areas eventually collapsed, allowing the hydrogen and helium to accumulate in clumps of dark matter swirling through space and the first stars and galaxies to form. 

READ ABOUT: 

QUASARS: https://www.iasgyan.in/daily-current-affairs/quasars

MAGNETAR:  https://www.iasgyan.in/daily-current-affairs/magnetar

BLUE STRAGGLER: https://www.iasgyan.in/daily-current-affairs/blue-straggler-20

READ: Active Galactic Nuclei (AGN): https://www.iasgyan.in/daily-current-affairs/active-galactic-nuclei-agn

BLACK HOLES: https://www.iasgyan.in/daily-current-affairs/black-hole-13

Sources: 

HINDU