December 1, 2022

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Even with the Webb Space Telescope, certain corners of the universe cannot be reached

Even with the Webb Space Telescope, certain corners of the universe cannot be reached

Time and time again, the Webb telescope impresses us with new images of things we already know, which, due to their capabilities, are much better than previous space telescopes, which look amazing. But this telescope also has its limitations

Space is theoretically open only to us. Missions like Artemis not only have trouble going to this remote space, but not all the objects in that space can be observed. Some constraints seem obvious, such as those imposed by matter in the disk and center of the galaxy, which obscure what lies beyond.

That is why astronomers cannot observe the space beyond the Milky Way in about 10% of the sky. It’s just that in this direction you can only see the objects of our galaxy, and what is hidden behind a thick veil of dust and many stars in our surroundings is very difficult to see.

Astronomers have managed to penetrate the dust of the Milky Way

Of course, this limitation can be overcome and one way is to observe infrared radiation. It requires long monitoring cycles, but it seems to pay off slowly. The VVV survey likely detected a large structure, consisting of several dozen galaxies, behind the Milky Way.


VVV survey observations are made with the help of the VISTA telescope on the Cerro Paranal. The image here shows a gigapanorama toward the center of the galaxy

However, even in this case, the monitoring possibilities available to us seem to be limited (photo above can be enlarged And then you can see how crowded it is in the center of the galaxy) and it’s hard to expect that the direction of observing through the galactic disk would give us a chance to get to things from the beginning of the universe.

The beginning of the universe required infrared observation, among other things

The beginning of the universe as we know it has recently been undergoing a turbulent process of reconstruction, because not only doubts about the Standard Model have emerged, but also the need for certain stages in the evolution of the universe. However, this is a topic for a different, broader discussion, as while we limit ourselves to what we know, we can use the Webb Space Telescope for observation.

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backward time notes
Observing the origins of the universe goes back to the past. Practically speaking, we cannot see the entire universe as it is today. The farther we look, the older we see him. We can say that we observe it at every moment of its existence, but every part of space is in a different period of time

Thanks to the previously unprecedented possibilities of infrared observation, it is able to observe very distant galaxies and possibly the stars that make up them. However, is he able to go back to the times (because remote observations are also observations from the past) when the universe was young and no more than a few hundred million years old, and the first stars, of which the first galaxies formed, were in the making?

What are the first stars in the universe?

Protostars are the so-called group III, a group of things that are still considered theoretical rather than directly observed and confirmed. These are the oldest and least diverse stars in terms of composition. It was similar to the formation of the universe in the early eons of the universe. These primitives were 3/4 hydrogen to 1/4 helium and had a bit of a lithium mixture.

Formation of protostars and the sun
Formation of protostars compared to the Sun and approximate size difference (Image: STScI)

Our Sun, as a star of the early inhabitants, which is relatively small, also contains mostly hydrogen and helium, but also contains a rich mixture of heavier elements at a level of 2% of the total composition, that is, the so-called mineral is high.

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There are also group II stars that have low but detectable metallic levels, usually very old and young stars. It was formed after the stars of the third group were left behind. These elements have enriched the universe with the first dose of the most massive minerals, which is why the second group already contains some mixture of them in the composition.

And these, due to the lack of minerals in the composition, were all quite massive, as was expected. Much larger than the Sun, they age much faster and explode as supernovae. Therefore, their research covers the time in which they existed, that is, the early stages of the universe’s existence, and this means observing the most distant things. And here the question arises, were these primordial stars bright enough?

We are looking for protostars, smaller than the third group of stars, at the very beginning of the universe’s existence, and observing its farthest corners, because perhaps these stars existed only at that time.

Because observing their remnants (black holes, neutron stars and even white dwarfs), which we will certainly find at a shorter distance from the Sun, with direct contact with the original object is somewhat out of the question. There is also a possibility that some primordial stars were and will still be low mass and will exist in the Milky Way, but nothing has happened so far.

Will Webb see primordial stars and galaxies? As long as it exists

Today, after traveling approximately 13.8 billion light-years, photons from these stars have significantly reddened and their flux is weakened by intergalactic material in the way of the Webb telescope’s infrared detectors. So it is clear to assume that these stars, despite their enormous brightness, as well as the first galaxies from which they were formed, will be very weak sources of light in our sky.

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Primary star redness
As it travels from the protostar to the Webb Telescope, the light photons lose their energy, and the star’s ultraviolet spectrum shifts toward the visible and infrared (Image: STScI)

A group of astronomers decided to theoretically simulate the amount of light emitted by these faint stars, even assuming that there were no obstacles in the path of the observer. The result is not positive, although there are works that suggest otherwise.

Unfortunately, it would be nearly impossible to observe such stars and their primordial galaxies even using Webb’s instruments, unless mission control chose very long exposures (up to about 50 days) and the source stars were massive and very bright. However, most of them, despite their enormous brightness, would still be objects too faint for an observer on Earth.

There is, of course, a portal, even with Webbie…

… They are gravitational lenses, which amplify light from distant stars, galaxies. It is to his credit that Webb, and will continue to be in the future, will reach things far beyond what the scope of his observation might suggest. However, to see the first galaxies without the additional help of a lens, rehashing jokes about K2’s winter forays in a way that will count, requires a more powerful Webb telescope.

Hubble Erndell
Earndel, the most distant star observed so far by the Hubble Space Telescope. Through the lens we saw an object that emitted light 12.9 billion years ago. The inset shows the location of the star in one of the lensed arcs of the image. Webb has a chance of getting farther than Hubble in this way

Supporting the capabilities of the Webb Space Telescope could also be giant telescopes currently under construction on Earth, such as the Giant Magellan Telescope with a mirror with an effective diameter of about 25 meters.

Source: phys.org, inf. Own, STScI