QUASARS

1. Context 

2. About Quasars

• Quasars short for "quasi-stellar radio sources" were first discovered six decades ago. 
• They are located in supermassive black holes, which sit in the centre of galaxies.
• As a supermassive black hole feed on gas and dust, it releases extraordinary amounts of energy in the form of radiation, resulting in a quasar.
• The mechanisms that trigger quasars have been hotly debated. Some studies suggest galaxy mergers are responsible, while others found little evidence to support the theory.

3. Findings of the Study

• The mixed results are because the images used in many studies were not sensitive enough to detect them.
• To tackle this issue, the image is a large sample of quasars with the appropriate depth to identify these signatures.
• To do this, researchers relied on the Isaac Newton Telescope in La Palma in the Canary Islands. They compared 48 galaxies that host quasars with over 100 non-quasar galaxies.
• Galaxies that host a quasar showed morphological features that are consistent with galaxy mergers, the researchers noted.
• When galaxies collide, it pushes the gas from the outer reaches of galaxies to the centre. And as the supermassive black hole gorges on the gas, it releases ferocious fountains of energy in the form of radiation, leading to the quasar.
• These results present strong evidence that galaxy interactions are the dominant trigger for quasars in the local universe.
• However, they are unlikely to be the sole factor, the researchers wrote in their study.

4. Significance of quasars

• When a quasar is ignited, it can drive the rest of the gas out of the galaxy. 
• The radiation from these objects is so intense that intervening gas within the galaxy feels a pressure that moves it away from the quasar in the nucleus, driving "outflows" of material.
• In extreme cases, a significant fraction of the total gas in a galaxy gets displaced. This has drastic consequences on star formation. 
• Also, the collision of the Milky Way galaxy with the Andromeda galaxy could likely trigger a quasar, the scientists predict in their study.
• Quasars are one of the most extreme phenomena in the universe and what we see is likely to represent the future of our own Milky Way galaxy when it collides with the Andromeda galaxy in about five billion years.
• It's exciting to observe these events and finally understand why they occur but thankfully, Earth won't be anywhere near one of these apocalyptic episodes for quite some time.
• Further, quasars act as "cosmic lighthouses" allowing researchers to see the outer reaches of the universe.
• NASA's James Webb Space Telescope will study the earliest galaxies in the universe.
• The telescope is capable of detecting light from even the most distant quasars, emitted nearly 13 billion years ago.
• The galaxy collisions are very important for triggering this activity in galaxies closer to us, we can consider whether these events were also important for igniting quasars in earlier epochs of the universe.

Source: Down to Earth