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What is Radio Astronomy?



Radio Astronomy

What is radio astronomy and what objects are used in the study? What are the most famous radio telescopes in the world?

What is Radio Astronomy?

Astronomy is one of the oldest sciences in the world. Since long ago, humans have tried to discover the various mysteries of the sky above their heads. Today, with the progress of science and technology, astronomy has become one of the most accurate and advanced sciences in the world. In astronomy, astronomers and astronomers study different structures and objects in the universe at different wavelengths. In other words, it can be said that today’s astronomy is classified into different branches, one of which is radio astronomy.

In this article, we are going to examine radio astronomy in detail. First, we will get acquainted with concepts such as wavelength and electromagnetic radiation. Finally, we find out what radio astronomy is and what objects it is most useful in studying.

A brief look at the basic concepts

For a better understanding of radio astronomy, it is better to get acquainted with the basic concepts needed first. These concepts help us to know better and more precisely how radio astronomers study different objects in the universe with the help of this science.


The environment around us is full of different waves. For example, when we use the TV remote control to turn it on/off or adjust the volume and change the channel, we are actually sending waves. Radios, microwaves, mobile devices, and thousands of other devices in today’s world also emit waves at different wavelengths. But what is the wavelength?

What is radio astronomy?

In physics, the distance between two peaks of a wave or the distance between two troughs of a wave is called ” wavelength “. The shorter this distance, the shorter the wavelength.


To understand the relationship between wavelength and energy, imagine a point on the waves in the image above. Suppose these waves are propagating in the same direction at the same speed, that is, both waves above are propagating from left to right at the same speed. Which wave has the highest number of crests in one second (for example) passing your desired point?

Obviously, more crests of a wave with a shorter wavelength will pass through your target point. So in other words, this wave has more energy. It can be said that the more compact the wave – the shorter its wavelength – the more energy it has. Therefore, wavelength and energy have an inverse relationship with each other.

Electromagnetic radiation

Now that we are familiar with the concepts of wavelength and energy, we can take a look at electromagnetic radiation. The discovery of electromagnetic radiation has a long history to which many physicists and scientists have contributed.

In short, scientists discovered in the 19th century that light actually consists of packets of energy called ” photons ” that can behave both like waves and particles.

Electromagnetic radiation is actually the wave-like behavior of light (imagine the waves emitted by dropping a stone into still water in a pond). Electromagnetic radiation covers a wide range of energy (or in other words, wavelength). We leave the investigation of the particle-like behavior of light to another article.

It is interesting to know that celestial objects such as stars radiate in all wavelengths of the electromagnetic spectrum. According to the wavelength, electromagnetic radiation is divided into different categories as you can see below.

Electromagnetic radiation

As you can see, gamma radiation is the most energetic part of the electromagnetic spectrum. In fact, gamma radiation is the dangerous radiation of the nuclei of heavy atoms such as uranium and radioactive materials. The energy of this radiation is so high that it can lead to disasters like Hiroshima.

After that, we see X-rays, which have lower energy and longer wavelengths than gamma rays. X-ray radiation is the same radiation used in radiology and photography in medicine.

Moving towards radiations with lower energy (and longer wavelengths) we reach the visible light range. Visible light is actually a part of the electromagnetic spectrum with a wavelength of 350 to 750 nm that the human eye can see.

In other words, our eyes are designed to see the world in visible light. Shorter or longer wavelengths are not visible to the human eye. For example, our eyes cannot see the infrared radiation of an object.

Finally, at the longest wavelengths, we reach radio radiation, which has the lowest energy. Radio waves have wavelengths ranging from a few centimeters to a few hundred meters. When you are tuning your radio to listen to your favorite radio station, you are actually tuning the wavelength of the radio waves that reach the radio receiver.

Satellites, television, and marine navigators are other tools that use radio waves to send information.

radio astronomy

Now that we are familiar with electromagnetic radiation and radio waves, we can better understand the concept of radio astronomy. As we said, heavenly bodies like stars radiate in the entire electromagnetic spectrum.

In short, the study of the radiation of celestial bodies in the radio range is called “radio astronomy”. High-energy celestial objects, as well as cold and dark objects with low energy, can radiate in the radio range of the electromagnetic spectrum.

Radio astronomers study the emission of gas giant planets, explosions in the depths of galaxies, or even the signals of a dying star, as well as quasars in this branch of astronomy.

radio astronomy

Each of the mentioned objects or phenomena has unique patterns of radio emission that help astronomers to obtain valuable information. Today, radio astronomy is one of the main branches of astronomy and reveals hidden features of our universe full of wonders.

Related Article: What is the farthest thing we can see in the sky?

It was the first time in 1933 that ” Karl Jansky ” managed to record radio radiation from the Milky Way in the Bell Telephone Laboratory. In fact, this was the first detection of radio waves from an astronomical object. It is interesting to know that before that, in the 1860s, scientists had succeeded in predicting the existence of such waves using ” James Clerk Maxwell’s ” equations, but the limitations of the instruments did not allow them to practically record these waves from celestial bodies until 1933. deliver

After that, with the advancement of technology, scientists managed to build a tool to study the radio radiation of astronomical objects in a special way.

Cosmic microwave background radiation, known as evidence of the Big Bang at the beginning of the universe, was discovered through radio astronomy.

Radio telescopes and radio astronomy

Astronomers around the world use radio telescopes to observe naturally occurring radio waves coming from stars, planets, galaxies, dust clouds, and gas molecules.

Astronomers use different methods and tools to study waves in the radio range. One of these famous tools is a large antenna that looks like a satellite dish and is called a “radio telescope”.

While some radio telescopes have only one large dish, some are giant arrays of many dishes stacked together. These sets of telescopes use radio interferometry techniques.

This array helps astronomers obtain radio data and precise images of distant objects in this wavelength range.

Gamma bursts

The radio signals collected by these telescopes are converted into data that can be used to create images. In fact, the data is colored by various techniques and converted into color images to display different properties of the object such as temperature.

Limitations of radio astronomy

Radio astronomers use various techniques to observe objects in the radio spectrum. Instruments may simply target a celestial body as an energetic radio source and analyze the data collected from it.

However, keep in mind that observations from the Earth’s surface are limited to wavelengths that can pass through the Earth’s atmosphere. At long wavelengths, the ionospheric layer of the Earth’s atmosphere becomes troublesome.

When we reach radio waves with very long wavelengths, the water vapor in the ionosphere interferes with the radio waves. For this reason, astronomers are building radio observatories that study shorter wavelengths of radio waves. These observatories, which operate at millimeter wavelengths, are built in dry, high-altitude areas to minimize the amount of water vapor in the line of sight.

On the other hand, the sources of radio waves on earth that are used for daily life can also cause interference in radio waves. For this reason, many radio observatories are built in places far away from human habitation.

The most famous radio telescopes in the world

As we said, radio telescopes in the world are either installed individually – single dishes with very large dimensions – or as arrays of several radio telescopes, to increase the amount of input data. In the following article, we will get to know some of the largest radio telescopes in the world and the largest radio telescope arrays.

Single radio telescope

The largest single radio telescope in the world is called the “Five-hundred-meter Aperture Spherical Telescope”, which is called ” FAST ” for short. This telescope, which is located in a natural valley in Guizhou province in China, was completed in 2016 and due to its very large size, it can observe objects at very far distances.

The spherical reflector of this radio super telescope has a diameter of 305 meters, and was built in collaboration with Cornell University in the United States.

Single radio telescope

” RATAN-600 ” is the name of another radio telescope that is very famous. This Russian radio telescope has a reflecting plate with a diameter of 895 meters and is located near the Caucasus Mountains. Researchers from Australia, France, India, Italy, Russia, and Ukraine have worked together to build such a huge and powerful telescope.

Single radio telescope

Additionally, the record for the largest fully automatic radio telescope goes to GBT, which stands for Robert C. Byrd Green Bank. This huge telescope is located in West Virginia and has been in operation since 2000. The GBT, which operates at short wavelengths of a few millimeters, weighs about 7.3 million kilograms!

Radio telescope

Radio telescope array

The largest and most famous array of radio telescopes in the world is called a “Very Large Array”, abbreviated as ” VLA “.

According to experts, this array is a combination of high sensitivity, clarity, and versatility. VLA consists of 27 dishes with a diameter of 25 meters each. This special and powerful complex is located in the center of New Mexico in the United States and allows more than 1,500 astronomers and astronomers to carry out their research every year. These telescopes are used to study the solar system, the Milky Way galaxy, stars, pulsars, atomic and molecular gases of the Milky Way, and other galaxies.

Radio telescope array

Among the other radio telescope arrays in the world, we can mention the “Westerbork” made in the Netherlands, which consists of 14 dishes each with a diameter of 25 meters.

On the other hand, Indian astronomers have also built the giant radio telescope ” GMRT ” near an area called “Puna” in India, which collects data from the universe at wavelengths of 20 cm to 6 meters.

Frequently asked questions of users

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Black holes may be the source of mysterious dark energy




black holes
The expansion of black holes in the universe can be a sign of the presence of dark energy at the center of these cosmic giants. The force that drives the growth of the world.

Black holes may be the source of mysterious dark energy


According to new research, supermassive black holes may carry the engines driving the universe’s expansion or mysterious dark energy. The existence of dark energy has been proven based on the observation of stars and galaxies, but so far no one has been able to find out its nature and source.

The familiar matter around us makes up only 5% of everything in the universe. The remaining 27% of the universe is made up of dark matter, which does not absorb or emit any light. On the other hand, a large part of the universe, or nearly 68% of it consists of dark energy.

According to new evidence, black holes may be the source of dark energy that is accelerating the expansion of the universe. This research is the result of the work of 17 astronomers in nine countries, which was conducted under the supervision of the University of Hawaii. British researchers from Raleigh Space, England’s Open University, and King’s College London collaborated in this research.

Black hole accretion pillAn artist’s rendering of a supermassive black hole complete with a fiery accretion disk.

By comparing supermassive black holes spanning 9 billion years of the universe’s history, researchers have found a clue that the greedy giant objects at the heart of most galaxies could be the source of dark energy. The articles of this research were published in The Astrophysical Journal and The Astrophysical Journal Letters on February 2 and 15. Chris Pearson, one of the authors of the study and an astrophysicist at the Appleton Rutherford Laboratory (RAL) in the UK says:

If the theory of this research is correct, it could revolutionize the whole of cosmology, because at least we have found a solution to the origin of dark energy, which has puzzled cosmologists and theoretical physicists for more than twenty years.

The theory that black holes can carry something called vacuum energy (an embodiment of dark energy) is not new, and the discussion of its theory actually goes back to the 1960s; But the new research assumes that dark energy (and therefore the mass of black holes) increases over time as the universe expands. Researchers have shown how much of the universe’s dark energy can be attributed to this process. According to the findings, black holes could hold the answer to the total amount of dark energy in the current universe. The result of this puzzle can solve one of the most fundamental problems of modern cosmology.

Rapid expansion

Our universe began with the Big Bang about 13.7 billion years ago. The energy from this explosion of space once caused the universe to expand so rapidly that all the galaxies were moving away from each other at breakneck speed. However, astronomers expected the rate of this expansion to slow down due to the gravitational influence of all the matter in the universe. This attitude toward the world prevailed until the 1990s; That is when the Hubble Space Telescope made a strange discovery. Observations of distant exploding stars have shown that in the past the universe was expanding at a slower rate than it is now.

Therefore, contrary to the previous idea, not only the expansion of the universe has not slowed down due to gravity, but it is increasing and speeding up. This result was very unexpected and astronomers sought to justify it. Thus, it was assumed that “dark energy” pushes objects away from each other with great power. The concept of dark energy was very similar to a cosmic constant proposed by Albert Einstein that opposes gravity and prevents the universe from collapsing but was later rejected.

Stellar explosions

But what exactly is dark energy? The answer to this question seems to lie in another cosmic mystery: black holes. Black holes are usually born when massive stars explode and die. The gravity and pressure in these intense explosions compress a large amount of material into a small space. For example, a star roughly the same mass as the Sun can be compressed into a space of only a few tens of kilometers.

The gravitational pull of a black hole is so strong that even light cannot escape it and everything is attracted to it. At the center of the black hole is a space called singularity, where matter reaches the point of infinite density. The point is that singularities should not exist in nature.

Speed ​​up dark energyDark energy explains why the universe is expanding at an accelerating rate.

Black holes at the center of galaxies are much more massive than black holes from the death of stars. The mass of galactic “massive” black holes can reach millions to billions of times the mass of the Sun. All black holes increase in size by accreting matter and swallowing nearby stars or merging with other black holes; Therefore, we expect these objects to become larger as they age. In the latest paper, researchers investigated the supermassive black holes at the centers of galaxies and found that the mass of these objects has increased over billions of years.

Fundamental revision

The researchers compared the past and present observations of elliptical galaxies that lack the star formation process. These dead galaxies have used up all their fuel, and as a result, their increase in the number of black holes over time cannot be attributed to normal processes that involve the growth of black holes by accreting matter.

Instead, the researchers suggested that these black holes actually carry vacuum energy, which has a direct relationship with the expansion of the universe, so as the universe expands, their mass also increases.

Black hole visualizationVisualization of a black hole that could play a fundamental role in dark energy.

Revealing dark energy

Two groups of researchers compared the mass of black holes at the center of two sets of galaxies. They were a young, distant cluster of galaxies with lights originating nine billion years ago, while the closer, older group was only a few million light-years away. Astronomers found that supermassive black holes have grown between seven and twenty times larger than before so this growth cannot be explained simply by swallowing stars or colliding and merging with other black holes.

As a result, it was hypothesized that black holes are probably growing along with the universe, and with a type of hypothetical energy known as dark energy or vacuum that leads to their expansion, they overcome the forces of light absorption and destruction of the stars in their center.

If dark energy is expanding inside the core of black holes, it can solve two long-standing puzzles of Einstein’s general relativity; A theory that shows how gravity affects the universe on massive scales. The new finding firstly proves how the universe does not fall apart due to the overwhelming force of gravity, and secondly, it eliminates the need for singularities (points of infinity where the laws of physics are violated) to describe the workings of the dark heart of black holes.

To confirm their findings, astronomers need more observations of the mass of black holes over time, and at the same time, they need to examine the increase in mass as the universe expands.

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Scientists’ understanding of dark energy may be completely wrong




dark energy
The standard model of cosmology says that the strength of dark energy should be constant, But inconclusive findings suggest that this force may have weakened.

Scientists’ understanding of dark energy may be completely wrong

On April 4th, astronomers who created the largest and most detailed 3D map ever made of the universe announced that they may have found a major flaw in their understanding of dark energy, the mysterious force driving the universe’s expansion.

Dark energy has been postulated as a stable force in the universe, both in the current era and throughout the history of the universe; But new data suggests that dark energy may be more variable, getting stronger or weaker over time, reversing or even disappearing.

Adam Reiss, an astronomer at Johns Hopkins University and the Space Telescope Science Institute in Baltimore, who was not involved in the new study, was quoted by the New York Times as saying, “The new finding may be the first real clue we’ve had in 25 years about the nature of dark energy.” In 2011, Reiss won the Nobel Prize in Physics along with two other astronomers for the discovery of dark energy.

The recent conclusion, if confirmed, could save astronomers and other scientists from predicting the ultimate fate of the universe. If the dark energy has a constant effect over time, it will eventually push all the stars and galaxies away from each other so much that even the atoms may disintegrate and the universe and all life in it, light, and energy will be destroyed forever. Instead, it appears that dark energy can change course and steer the universe toward a more fruitful future.

Dark energy may become stronger or weaker, reverse or even disappear over time

However, nothing is certain. The new finding has about a 1 in 400 chance of being a statistical coincidence. More precisely, the degree of certainty of a new discovery is three sigma, which is much lower than the gold standard for scientific discoveries called five sigma or one in 1.7 million. In the history of physics, even five-sigma events have been discredited when more data or better interpretations have emerged.

The recent discovery is considered an initial report and has been published as a series of articles by the group responsible for an international project called “Dark Energy Spectroscopy Instrument” or DESI for short. The group has just begun a five-year effort to create a three-dimensional map of the positions and velocities of 40 million galaxies over the 11 billion-year history of the universe. The researchers made their initial map based on the first year of observations of just six million galaxies. The results were presented April 4 at the American Physical Society meeting in Sacramento, California, and at a conference in Italy.

“So far we’re seeing initial consistency with our best model of the universe,” DESI director Michael Levy said in a statement released by Lawrence Berkeley National Laboratory, the center overseeing the project. “But we also see some potentially interesting differences that may indicate the evolution of dark energy over time.”

“The DESI team didn’t expect to find the treasure so soon,” Natalie Palanque-Delaberville, an astrophysicist at Lawrence Berkeley Lab and project spokeswoman, said in an interview. The first year’s results were designed solely to confirm what we already knew. “We thought we would basically approve the standard model.” But the unknowns appeared before the eyes of the researchers.

The researchers’ new map is not fully compatible with the standard model

When the scientists combined their map with other cosmological data, they were surprised to find that it didn’t completely fit the Standard Model. This model assumes that dark energy is stable and unchanging; While variable dark energy fits the new data. However, Dr. Palanque-Delaberville sees the new discovery as an interesting clue that has not yet turned into definitive proof.

University of Chicago astrophysicist Wendy Friedman, who led the scientific effort to measure the expansion of the universe, described the team’s results as “tremendous findings that have the potential to open a new window into understanding dark energy.” As the dominant force in the universe, dark energy remains the greatest mystery in cosmology.

Imaging the passage of quasar light through intergalactic clouds
Artistic rendering of quasar light passing through intergalactic clouds of hydrogen gas. This light provides clues to the structure of the distant universe.
NOIRLab/NSF/AURA/P. Marenfeld and DESI collaboration

The idea of ​​dark energy was proposed in 1998; When two competing groups of astronomers, including Dr. Rees, discovered that the rate of expansion of the universe was increasing rather than decreasing, contrary to what most scientists expected. Early observations seemed to show that dark energy behaved just like the famous ” fudge factor ” denoted by the Greek letter lambda. Albert Einstein included lambda in his equations to explain why the universe does not collapse due to its own gravity; But later he called this action his biggest mistake.

However, Einstein probably judged too soon. Lambda, as formulated by Einstein, was a property of space itself: as the universe expands, the more space there is, the more dark energy there is, which pushes ever harder, eventually leading to an unbridled, lightless future.

Dark energy was placed in the standard model called LCDM, consisting of 70% dark energy (lambda), 25% cold dark matter (a collection of low-speed alien particles), and 5% atomic matter. Although this model has now been discredited by the James Webb Space Telescope , it still holds its validity. However, what if dark energy is not as stable as the cosmological model assumes?

The problem is related to a parameter called w, a special measure for measuring the density or intensity of dark energy. In Einstein’s version of dark energy, the value of this parameter remains constant negative one throughout the life of the universe. Cosmologists have used this value in their models for the past 25 years.

Albert Einstein included lambda in his equations to explain why the universe is collapsing under its own gravity.

But Einstein’s hypothesis of dark energy is only the simplest version. “With the Desi project we now have the precision that allows us to go beyond that simple model to see if the dark energy density is constant over time or if it fluctuates and evolves over time,” says Dr. Palanque-Delabreville.

The Desi project, 14 years in the making, is designed to test the stability of this energy by measuring the expansion rate of the universe at different times in the past. In order to do this, scientists equipped one of the telescopes of the Keith Peak National Observatory in Arizona, USA, with five thousand optical fiber detectors that can perform spectroscopy on a large number of galaxies at the same time to find out how fast they are moving away from Earth.

The researchers used fluctuations in the cosmic distribution of galaxies, known as baryonic acoustic variations , as a measure of distance. The sound waves in the hot plasma accumulated in the universe, when it was only 380,000 years old, carved the oscillations on the universe. At that time, the oscillations were half a million light years across. 13.5 billion years later, the universe has expanded a thousandfold, and the oscillations, now 500 million light-years across, serve as convenient rulers for cosmic measurements.

Desi scientists divided the last 11 billion years of the universe into 7 time periods and measured the size of the fluctuations and the speed of the galaxies in them moving away from us and from each other. When the researchers put all the data together, they found that the assumption that dark energy is constant does not explain the expansion of the universe. Galaxies appeared closer than they should be in the last three periods; An observation that suggests dark energy may be evolving over time.

“We’re actually seeing a clue that the properties of dark energy don’t fit a simple cosmological constant, and instead may have some deviations,” says Dr. Palanque-Delaberville. However, he believes that the new finding is too weak and is not considered proof yet. Time and more data will determine the fate of dark energy and the researchers’ tested model.

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Why the James Webb telescope does not observe the beginning of the universe?




James Webb telescope

The James Webb Space Telescope is one of the most advanced telescopes ever built. Planning to launch James Webb began more than 25 years ago, and construction efforts took more than a decade. On December 25, 2021, this telescope was launched into space and within a month it reached its final destination, 930,000 miles away from Earth. Its position in space gives it a relatively unobstructed view of the world.

Why the “James Webb” telescope does not observe the beginning of the universe?

The design of this telescope was a global effort led by NASA and aims to push the boundaries of astronomical observation with revolutionary engineering. Its mirror is huge, about 21 feet (6.5 meters) in diameter, which is about three times the size of the Hubble Space Telescope, which was launched in 1990 and is still operating.

According to SF, it’s the telescope’s mirror that allows it to gather light. James Webb is so big that it can see the faintest and most distant galaxies and stars in the universe. Its advanced instruments can reveal information about the composition, temperature, and motion of these distant cosmic bodies.

Astrophysicists constantly look back to see what stars, galaxies, and supermassive black holes looked like when their light began its journey toward Earth, and use this information to better understand their growth and evolution. For the space scientist, the James Webb Space Telescope is a window into that unknown world. How far can James Webb look into the universe and its past? The answer is about 13.5 billion years.

Time travel

A telescope does not show stars, galaxies, and exoplanets as they are. Instead, astrologers have a glimpse of how they were in the past. It takes time for light to travel through space and reach our telescope. In essence, this means that looking into space is also a journey into the past.

This is true even for objects that are quite close to us. The light you see from the sun has left about eight minutes and 20 seconds earlier. This is how long it takes for sunlight to reach the earth.

You can easily do calculations on this. All light, whether it’s sunlight, a flashlight, or a light bulb in your home, travels at a speed of 186,000 miles (approximately 300,000 kilometers) per second. This is more than 11 million miles, which is about 18 million kilometers per minute. The sun is about 93 million miles (150 million kilometers) from the earth. which brings the time of reaching the light to about eight minutes and 20 seconds.

Why the “James Webb” telescope does not observe the moment of the beginning of the universe?

But the farther something is, the longer it takes for its light to reach us. That’s why the light we see from the closest star to us other than the Sun, Proxima Centauri, dates back four years. This star is about 25 trillion miles (about 40 trillion kilometers) from Earth, so it takes a little over four years for its light to reach us.

Recently, James Webb has observed the star Earendel, which is one of the most distant stars ever discovered and the light that James Webb sees is about 12.9 billion years old.

The James Webb Space Telescope travels much further into the past than other telescopes such as the Hubble Space Telescope. For example, although Hubble can see objects 60,000 times fainter than the human eye, James Webb can see objects almost 9 times fainter than even Hubble.

Read more: How can solar storms destroy satellites so easily?

Big Bang

But is it possible to go back to the beginning of time?

Big Bang is the term used to define the beginning of the universe as we know it. Scientists believe that this happened about 13.8 billion years ago. This theory is the most accepted theory among physicists to explain the history of our universe.

However, the name is a bit misleading because it suggests that some kind of explosion, like a firework, created the universe. The Big Bang more accurately represents space that is rapidly expanding everywhere in the universe. The environment immediately after the Big Bang resembled a cosmic fog that covered the universe and made it difficult for light to pass through. Eventually, galaxies, stars, and planets began to grow.

That’s why this period is called the “Cosmic Dark Age” in the world. As the universe continued to expand, the cosmic fog began to lift and light was finally able to travel freely through space. In fact, few satellites have observed the light left over from the Big Bang some 380,000 years after it happened. These telescopes are designed to detect the glow left over from the nebula, whose light can be traced in the microwave band.

However, even 380,000 years after the Big Bang, there were no stars or galaxies. The world was still a very dark place. The cosmic dark ages did not end until several hundred million years later when the first stars and galaxies began to form.

The James Webb Space Telescope was not designed to observe the time to the moment of the Big Bang, but to see the period when the first objects in the universe began to form and emit light.

Before this time period, due to the conditions of the early universe and the lack of galaxies and stars, there was little light for the James Webb Space Telescope to observe.

By studying ancient galaxies, scientists hope to understand the unique conditions of the early universe and gain insight into the processes that helped them flourish. This includes the evolution of supermassive black holes, the life cycles of stars, and what exoplanets are made of.

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