What the latest images from the James Webb Space Telescope tell us

As predicted long before it was put into operation, the James Webb Space Telescope continues to amaze us with its enormous potential to penetrate into the most distant and primitive universe.

On this occasion we have been able to enjoy an image showing different depths in the universe: from a star close in the Milky Way, passing through the galaxies of the Pandora cluster (located about 4 billion light years from Earth). Thus, we have come to observe galaxies so distant that they were not known to date.

This new panoramic image is made up of a composite of four James Webb snapshots, and is estimated by astronomers to consist of some 50,000 infrared light-emitting sources.

However, before analyzing this new image of the deep sky in detail, let’s see what a galaxy cluster like the one in Pandora consists of.

Thousands of galaxies held together by their gravitational attraction

The gravitational force is responsible for keeping these galaxies grouped, which can range in number from a few dozen (small groups) to thousands (as is the case with clusters).

Large galaxy clusters and superclusters often exhibit strong X-ray emission due to heating of intergalactic gas to millions of degrees of temperature. It is worth mentioning that our Milky Way belongs to the Local Group of galaxies, which is located on the outskirts of the Virgo Supercluster.

As an example, the image below corresponds to the galaxy cluster IDCS 1426, one of the most massive clusters detected in the early universe. Located 10,000 million light years from Earth, its mass is equivalent to 500 trillion suns.

When these clusters get in the way of light from a more distant object, it bends and produces gravitational lensing, one of the keys to successfully observing the earliest galaxies.

A magnifying glass that magnifies the most distant objects

This is an effect already predicted by Einstein’s general theory of relativity. The equivalent phenomenon in optics would consist of the deformation of the image of an object when we look through a lens.

The following animation explains this effect in detail. A very massive object (for example, a black hole) moves from left to right in the figure, in front of a background formed by a galactic grouping.

The light coming from these galaxies undergoes the effect of gravitational lensing when it passes close to the black hole and the image we observe is perceived distorted and amplified.

Even the James Webb telescope would not have been able to detect the most distant galaxies without this aid in the form of a gravitational lens.

The new images of the Pandora cluster (and beyond)

Some details of this new snapshot of James Webb (among the many yet to be discovered and that are currently being studied) would be the following:

In the foreground we observe a star close to our own galaxy with the typical 8-pointed star shape of James Webb.

The reason for this peculiar shape is due to diffraction produced by both the telescope’s hexagonal primary mirror and the secondary mirror supports.

The bright white sources (surrounded by a hazy glow) correspond to galaxies that are part of the Pandora cluster (Abell 2744).

Although it may seem surprising, the galaxies in this cluster contribute less than 5% to its mass: hot gas (which it emits in the form of X-rays) contributes 20% of the total, leaving the remaining 75% to the distribution of dark matter .

On the other hand, expanding the detail of this impressive mosaic, we can observe galaxies that had not been detected in previous studies (carried out, for example, by the Hubble Space Telescope).

In particular, the bottom image shows a reddish spiral galaxy found by James Webb. It is a galaxy that still maintains the structure of spiral arms (containing large amounts of stellar dust), but abundant in stars old with a marked reddish hue.

A new supermassive black hole?

It is difficult to notice this detail, but the presence of this very distant small red dot (with hardly any distortion by gravitational lensing) has not gone unnoticed by astronomers analyzing these new images.

What kind of astronomical object would be able to remain unfazed, despite the great magnifying effect of the gravitational lensing of the galaxy cluster?

Although these are still very preliminary studies, a possible explanation would be the emission of gases heated to enormous temperatures that orbit a supermassive black hole.

What we can be completely sure of is the ability of the James Webb Space Telescope to continue to take amazing images of the deep sky: we will continue to discover and admire the most unexplored and distant universe.

Oscar del Barco Novillo, Assistant Professor Doctor. Applied Physics Department, Zaragoza’s University

This article was originally published on The Conversation. Read the original.