Type: Prelims Only

On Dec 18, 2021, after years of delays, the James Webb Space Telescope is scheduled to launch into orbit and usher in the next era of astronomy.

James Webb Space Telescope

• JWST is a joint NASA–ESA–CSA space telescope that is planned to succeed the Hubble Space Telescope as NASA’s flagship astrophysics mission
• It is the most powerful space telescope ever built.
• It will enable a broad range of investigations across the fields of astronomy and cosmology, including observing some of the most distant events and objects in the universe,
• It would help understand events such as the formation of the first galaxies, and detailed atmospheric characterization of potentially habitable exoplanets.

Its significance

• Some have called JSWT the “telescope that ate astronomy.”
• It is said to look back in time to the Dark Ages of the universe.

What does the ‘Dark Ages’ of the universe mean?

• Evidence shows that the universe started with an event called the Big Bang 13.8 billion years ago, which left it in an ultra-hot, ultra-dense state.
• The universe immediately began expanding and cooling after the Big Bang.
• One second after the Big Bang, the universe was a hundred trillion miles across with an average temperature of an incredible 18 billion F (10 billion C).
• Around 400,000 years after the Big Bang, the universe was 10 million light-years across and the temperature had cooled to 5,500 F (3,000 C).
• Throughout this time, space was filled with a smooth soup of high-energy particles, radiation, hydrogen and helium.
• There was no structure. As the expanding universe became bigger and colder, the soup thinned out and everything faded to black.

This was the start of what astronomers call the Dark Ages of the universe.

How will JWST study this?

Ans. Looking for the first light

• The Dark Ages ended when gravity formed the first stars and galaxies that eventually began to emit the first light.
• Astronomers aim to study this fascinating and important era of the universe, but detecting first light is incredibly challenging.
• Compared to massive, bright galaxies of today, the first objects were very small and due to the constant expansion of the universe, they’re now tens of billions of light years away from Earth.
• Also, the earliest stars were surrounded by gas left over from their formation and this gas acted like fog that absorbed most of the light.
• It took several hundred million years for radiation to blast away the fog. This early light is very faint by the time it gets to Earth.

Try this PYQ:

Consider the following phenomena:

1. Light is affected by gravity.
2. The Universe is constantly expanding.
3. Matter warps its surrounding space-time.

Which of the above is/are the predictions of Albert Einstein’s General Theory of Relativity, often discussed in media?

(a) 1 and 2 only

(b) 3 only

(c) 1 and 3 only

(d) 1, 2 and 3

 

Post your answers here.

UPSC 2022 countdown has begun! Get your personal guidance plan now! (Click here)

The researchers from the Geological Survey of India collected about 30 meteorite fragments with the largest weighing around a kilogram near the town of Katol in Nagpur in 2012.

Significance of meteor study

• Now, by studying the composition of these meteorite fragments, researchers have unraveled the composition expected to be present in the Earth’s lower mantle which is at about 660 km deep.
• Studying the meteorite could also tell us more about how our Earth evolved from being a magma ocean to a rocky planet.

Key component of the Meteor: Olivine

• Initial studies revealed that the host rock was mainly composed of olivine, an olive-green mineral.
• Olivine is the most abundant phase in our Earth’s upper mantle.
• Our Earth is composed of different layers including the outer crust, followed by the mantle and then the inner core.

How to study a meteorite?

• The researchers took a small sample of the meteorite and examined it using special microscopy techniques.
• The mineralogy was determined using a laser micro-Raman spectrometer.
• These techniques helped the team identify, characterise the crystal structure of the meteorite and determine its chemical composition and texture.

What does the new study show?

• The international team of scientists examined a section of this highly-shocked meteorite. It resembles to the first natural occurrence of a mineral called bridgmanite.
• The mineral was named in 2014 after Prof. Percy W. Bridgman, recipient of the 1946 Nobel Prize in Physics.
• Various computational and experimental studies have shown that about 80% of the Earth’s lower mantle is made up of bridgmanite.
• By studying this meteorite sample, scientists can decode how bridgmanite crystallized during the final stages of our Earth’s formation.

Bridgmanite: On Earth vs. on Meteorite

• Katol meteorite is a unique sample and it is a significant discovery.
• The bridgmanite in the meteorite was found to be formed at pressures of about 23 to 25 gigapascals generated by the shock event.
• The high temperature and pressure in our Earth’s interior have changed over billions of years causing crystallisation, melting, remelting of the different minerals before they reached their current state.
• It is important to study these individual minerals to get a thorough idea of how and when the Earth’s layers formed.

How does it help understand evolution of Earth?

• The inner planets or terrestrial planets or rocky planets Mercury, Venus, Earth, and Mars are formed by accretion or by rocky pieces coming together.
• They were formed as a planet by increased pressure and high temperature caused by radioactive elements and gravitational forces.
• Our Earth was an ocean of magma before the elements crystallised and stabilised and the different layers such as core, mantle were formed.
• The heavier elements like iron went to the core while the lighter silicates stayed in the mantle.
• By using the meteorite as an analog for Earth, we can unearth more details about the formation.

Answer this question from our AWE initiative:

What are seismic waves? How have they helped in understanding the structure of the earth? (250 W/ 15 M)

UPSC 2022 countdown has begun! Get your personal guidance plan now! (Click here)