Expert Explains: How James Webb Space Telescope has raised questions in cosmology

Sub: Sci

Sec: Space

Context:

Images from the James Webb Space Telescope are puzzling – instead of newborn galaxies, the early phases of the Universe appear to be full of adult-sized galaxies.
This discovery could demand a more comprehensive rethink of cosmic history.

James Webb Space Telescope (JWST):

Largest and most powerful telescope in space.
It has a huge mirror that is five times bigger than that of its predecessor, the Hubble Space Telescope.
JWST was launched on Christmas Day in 2021 and arrived at its destination, the Sun-Earth Lagrange point 2 in January 2022
The telescope has been looking at the early epochs in the history of the Universe, when the first galaxies had barely formed.
Its images were, however, very different from what astronomers had thought they would see.
The James Webb Space Telescope (JWST or “Webb”) is a joint NASA–ESA–CSA space telescope that is planned to succeed the Hubble Space Telescope as NASA’s flagship astrophysics mission.
The JWST will provide improved infrared resolution and sensitivity over Hubble, and 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, such as the formation of the first galaxies.
JWST will study various phases in the history of the universe, from the formation of solar systems to the evolution of our own Solar System.
The James Webb Space Telescope (sometimes called JWST or Webb) is an orbiting infrared observatory that will complement and extend the discoveries of the Hubble Space Telescope, with longer wavelength coverage and greatly improved sensitivity.

What is puzzling about the images?

Scientists had expected to find newborn galaxies. instead, the early phases of the Universe appear to be full of adult-sized galaxies.
The space telescope was designed to peer at toddler galaxies.
Those baby galaxies were supposed to be relatively smal But the data coming out of JWST seem to show full-bodied galaxies at the dawn of the Universe, with billions of stars.

Ways to measure expansion:

The rate of expansion of the Universe has been a subject of scientific debate for quite some time.
Two different methods of determining the rate have yielded results that differ by as much as 10%.
Method 1: It is based on phenomena in the early Universe, which implies events at a great distance, because the light we see from distant objects started its journey a long time ago.
- The early Universe method relies on a relic radiation from the primeval epochs, when the Universe was hot.
- The radiation has now cooled down as the Universe has expanded, and has become a microwave ‘hum’.
- A detailed analysis of this radiation can tell us how fast the Universe has been expanding.
Method 2: relies on local celestial objects, although ‘local’ means a region spanning billions of light years.
- Some stars vary their brightness in a periodic manner, and the duration of this change tells us something about how bright they really are.
- From this, one can figure out their distance and, in turn, how the Universe has been expanding.

Discrepancy in figures:

The new space telescope was expected to nail the reason for the mismatch between the results obtained by the two methods.
But its measurements seem to have only increased the discrepancy.
Its deeper inspection of the local method of measurement gives a rate of expansion that is somewhat faster than that based on early Universe