Farthest galaxies: How to measure the distance to the first objects of the universe

Farthest galaxies: How to measure the distance to the first objects of the universe

One of the main functions of the James Webb Space Telescope is to find the earliest galaxies, expanding our exploration of the universe both in space and in time. In the month following the publication of the first scientific data collected by the telescope, more than 10 scientific publications have already appeared on the Preprist Portal, describing candidates for the first "residents" of the early universe. If the measurements are correct, these galaxies existed only 200 to 300 million years after the Big Bang.

These star systems are located much further than all previously observed objects of the universe. Scientists write about red-shift galaxies between 12 and 17. But in this celebration of science, there is also a spoon of degit: some researchers believe that the age of objects can be distorted and the results require careful testing.

Which galaxy is the farthest?

Before the launch of the James Webb Space Telescope for a long time, the most remote confirmed galaxy was the GN-z11. It was discovered in 2016 by the Hubble Telescope. It is about 25 times smaller than the Milky Way and represents about 1% of its mass.

GN-z11 is located in the constellation of the Great Bear, and astrophysicists estimate a red shift of 11.1, which means that we see it as it was 13.4 billion years ago, just 400 years after the Big Bang. Since the universe is constantly expanding, galaxies in space are moving away from each other. So our own distance to GN-z11 is about 32 billion light years.

Even before the launch of the new telescope in the spring of 2022, astrophysicists announced the discovery of an even more distant candidate, HD1. It was detected by the Subarou Space Telescope and by ground-based observations. According to the spectroscopy, its red shift is 13.27, which corresponds to a distance of 13.5 billion light years, and the galaxy itself is now 33.4 billion light years away from the Earth.

Just a week after the release of the first data from the James Web telescope, researchers from the Harvard-Smixon Center for Astrophysics announced the discovery of the GLASS-z13 galaxy, which was previously estimated at 13. This is about 300 million years after the Big Bang. A week later, there was a report of a red-shifted galaxy of 14 and even 16.7 If that is true, we see these galaxies as they existed some 200 million years after the Big Bang.

True, all these results are preliminary: until any of these red displacements are confirmed, spectroscopic analysis will be required to determine the distances to these galaxies.

How did they find the new galaxies?

For example, astrophysicists at Missouri Columbia University used gravitational lens effects created by a massive cluster of SMACS J0723 galaxy. A mass object distorts the movement of light by increasing distant objects as the normal optical lens of the telescope. By this method, scientists discovered 88 galaxies with a red shift of at least 11 candidates. Some of them may have a red shift to 20.

Other scientists analysed images of different parts of the sky that did not use gravitational lens effects. These images are part of a study by Cosmic Evolution Early Release Science.

To confirm the real age of distant objects, spectroscopic analysis is required that separates the light from the object into the spectrum, using the near infrared spectrum of the James Webb telescope.

What's a red shift?

When you look at the early universe, the main indicator that scientists use is a red shift. It helps you understand how fast an object is moving away from us. Just like the signal of a sailor or a ship sounds lower when they move from an observer, the light wave changes from a distant object.

The universe is constantly expanding, which means that distant galaxies are moving away from Earth. With a red shift, electromagnetic radiation from a remote object increases the wave length, which means that all the details of the spectrum are moving towards the red area.

The further the galaxy goes, the sooner we see it and the more light it spreads due to the expansion of the universe, the blue and ultraviolet light from hot young stars in 13.5 billion years seems infrared to us.

James Webb's telescope is equipped with sensitive instruments that detect radiation in various areas of the infrared range and therefore can capture the radiation of the early universe.

Why can the first results be wrong?

Preliminary studies are based on single observations and may not be accurate; for example, dust galaxy with star formation, which existed billions of years after the Big Bang, can mask itself under the record distance; and, in addition, light blazed by galaxies can be distorted by other objects.

For example, based on how the red galaxy CEERS-DSFG-1 looks on images of the James Web telescope, astronomers have identified a red shift between 17 and 18. This means that we see it 220 million years after the Big Bang, but Japanese astronomers have used the NOEMA submillimeter telescope to find the same galaxy and show that it contains a huge amount of dust.

Dust absorbs shorter and blue waves of starlight, missing longer and more red, which means that if you look at it from the Earth, the galaxy will look more red. By adjusting the observations to the dust effects, scientists have shown that the real red shift is only about five, which means that the galaxy is seen 1.3 billion years after the Big Bang.

The same results came from researchers who studied the CEERS-1749 galaxy. They called their discovery Schroedinger's galaxy. The whole thing is that red displacement can be equal to either five or 17. If it's a separate, distant galaxy, it's one of the most known systems, and if it's part of a cluster, it's again a billion years after the Big Bang. It's going to be clear after new research.

Whether or not the declared records are confirmed, the new discoveries will make a significant contribution to understanding the development processes of the early universe. Even the "near" distant galaxies, with a red shift of about 5, open up new data.

The interstellar dust is a by-product of the birth cycle and the death of the stars. To influence the red displacement of such dust, there must be a lot of dust, which means that there must be very intensive star formation in such galaxies. Previously, scientists were unaware of such processes.

A large number of distant galaxies from different lifetimes of the universe will help to understand how the first star systems were formed and developed.