Why do astronomers seek to discover the most distant galaxies?

In the past months, an international team of astronomers introduced a galaxy called HD1 to the world, which, if confirmed, would be the most distant astronomical object discovered.

BingMag.com Why do astronomers seek to discover the most distant galaxies?

In the past months, an international team of astronomers introduced a galaxy called HD1 to the world, which, if confirmed, would be the most distant astronomical object discovered.

HD1 shone in the Big Bang only 320 million years after the birth of the universe, when it is very close to the origin of the universe, and so the light from this galaxy has traveled an incredible 13.4 billion years for reaching our telescopes has done.

To have an understanding of this time, one must consider that dinosaurs roamed our planet only 0.2 billion years ago, and the entire history of the Earth from 4.5 billion years ago. it has begun. So when the photons finally recorded by our telescopes left HD1, our planet still didn't exist. Even the appearance of the solar system itself took place approximately 9 billion years after the Big Bang.

Understanding the Evolution of the Universe

But the reason for this new type of space race is to look at the oldest and most distant. What are objects? There is undoubtedly something poetic, even epic, in discerning light emerging from the darkness of the early universe. But there is a much deeper motivation for such a search.

Simply put, it should be said that astronomers are looking to complete a thousand-year quest to map the universe and its evolution. Studying ancient objects like HD1 could help fill long-standing gaps in our knowledge, allowing us to finally see how the universe evolved from an amorphous expanse of plasma to the familiar arrangements of galaxies, stars and planets that grace the sky. .

The study of distant sources requires an understanding of what astrophysical source produced their light. For example, scientists have offered several explanations for HD1. Among them, the light must either come from the collective glow of billions of stars of a certain mass, or from a supermassive black hole that feeds on enormous amounts of gas.

Study of cosmic objects with light

Astronomers often try to infer the nature of light sources that are billions of light years away from us by studying their spectra, that is, the division of the received light into its constituent colors. This can be very complex, so in such cases, the information about a source is definitely incomplete and uncertain.

For example, the light from HD1 shows something puzzling: the ultraviolet radiation of this most distant known galaxy. , is much stronger than what galaxies closer to us have. If most of this light is produced by stars, it should be somewhat different from our Sun, emitting more energetic photons.

Given how far back our view of HD1 takes us, these bright sources They can be among the first population of stars formed in the universe and the so-called Population III stars. Such stars, which have never been seen before and are thought to be heavier, larger and hotter than our Sun.

On the other hand, HD1 emits light that we would expect from a supermassive black hole with a mass of a hundred million times the Sun. Is compatible. It's about 25 times more massive than the Arc E* black hole recently imaged by the Event Horizon Telescope at the center of the Milky Way. It has a very distant and relatively violent past; When stars and galaxies were rare in the universe. In fact, HD1 shined during the period when the universe was finally exiting its initial state, an era that astronomers call the cosmic dark age: a period that lasted about a hundred million years and was essentially devoid of bright astrophysical objects. The first stars and black holes were just beginning to form, filling the universe with visible light for the first time.

BingMag.com Why do astronomers seek to discover the most distant galaxies?

HD1 is the most distant galaxy ever observed.
Credit: Harikane et al

More distant than the most distant

This The most distant galaxy discovered is 100 million years away from the previous record holder, the galaxy GN-z11, which was discovered in 2016, and 250 million years away from the third place, the galaxy EGSY8p7, which was discovered in 2015.

To understand the change in their spectrum, we can say that if a lamp that emits pure violet light is placed in a region of the universe that corresponds roughly to a redshift of 1 from Earth's point of view, it will appear dark red. arrives. Therefore, by comparing the observed spectra of these galaxies with the spectra of a stationary source, we can understand how fast the galaxies are moving away from us and how far away they are. Cosmic history is a book, transfer to red as page number It serves to indicate when an event occurs throughout the story. But unfortunately, not all chapters are visible to us, and cosmic dark ages make up the bulk of the book's missing pages. Imagine reading Shakespeare's Hamlet and skipping the opening scenes. Then you go from someone whispering in the dark to the walls of a castle in Denmark, to a prince who sees ghosts and stabs at the curtain.

This is the deepest and most detailed reason why astrologers continue to search for sources. They are further and further away. Fortunately, we live in an age where telescopes of unprecedented power can help us in this cosmic endeavor. It is like the first light of the cosmic dawn. Many other telescopes will play their part, including the Nancy Grace Roman Space Telescope and the new class of giant ground-based observatories that will join the array to explore the far reaches of the cosmos.

Over 13 billion years of evolution. The cosmos has reached this moment and us. It's heartening and sobering to think that our actions on this small, lonely planet may be the most profound expression of a universe trying to know itself.

Cover photo: The galaxy cluster MACS J0416.12403 from Hubble's gaze, in search of the most distant lights in the universe
Credit: ESA/Hubble, NASA, HST Frontier Fields
Acknowledgment: Mathilde Jauzac (Durham University, UK and Astrophysics & Cosmology Research Unit, South Africa) and Jean-Paul Kneib (cole Polytechnique Fdrale de Lausanne, Switzerland)

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