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What is an exoplanet? Everything you need to know



Planets outside the solar system are called exoplanets. So far, more than 5000 exoplanets have been definitively discovered.

What is an exoplanet? Everything you need to know

For years, extrasolar planets have occupied the minds of scientists and dreamers. Since the discovery of the first stars in the night sky, man has been searching for the worlds that revolve around these stars. Are exoplanets rocky bodies similar to Earth? Can they have liquid water flow on their surface? Does the existence of essential elements for life in other worlds mean that we are not alone in this infinite world?

For thousands of years, humans have been trying to answer this question: Are we alone? Until the 1990s, astronomers had no evidence of exoplanets; But finally, in 1992, the first exoplanet was discovered. Since then, more than 5,000 exoplanets have been discovered in different types and categories and have amazed scientists more than ever

Table of Contents
  • What is an exoplanet?
  • Types of extrasolar planets
  • Stone worlds
  • Gas giants
  • Introduction of extrasolar planets
  • TOI-1452b, a blue world candidate
  • WASP-39b, the first planet with a carbon dioxide atmosphere
  • WASP 103b, the rugby ball planet
  • 51 Pegasi b; The first planet around a Sun-like star
  • PSR B1620-26b; The oldest known planet
  • Gliese 876d; rocky planet
  • Kepler-11f; gas dwarf
  • Kepler-452b; Earth-like planet
  • Search for life in extrasolar planets
  • Interesting facts about exoplanets
  • Detecting the color of an exoplanet for the first time in 2013
  • There are 10 billion Earth-like planets in the Milky Way
  • NASA’s Kepler space telescope has discovered the most exoplanets
  • The possibility of exoplanets around stars with high metallicity
  • Using the gravitational microlensing method to observe exoplanets
  • Most exoplanets were discovered through radial velocity
  • The transit method is the easiest way to find exoplanets
  • Exoplanets can orbit more than one star
  • Exoplanets can have harsh climates
  • Some exoplanets have strange orbits
  • Exoplanets can have unique atmospheres
  • Conclusion

What is an exoplanet?

Exoplanet k128bIllustration of the exoplanet k12-18b, which is a super-Earth.

An exoplanet is a world outside the solar system in a different star system. Over the past two decades, thousands of exoplanets have been discovered, and most of these discoveries belong to NASA’s Kepler Space Telescope.

Exoplanets have different sizes and orbits. Some of them are giant worlds near the host star and others are icy and rocky worlds. NASA and other space agencies are always on the lookout for a specific type of exoplanet: an Earth-like planet in the habitable belt of a Sun-like star.

The habitable zone is the region of a star’s orbit where the planet’s temperature allows surface liquid water to flow. The first definition of the life belt was based on the concept of heat balance, however, based on current calculations, it also includes other criteria such as the greenhouse effect of the planet’s atmosphere. For this reason, determining the boundaries of the life belt has become a little vague.

The Kepler Space Telescope, an observatory that started its operation in 2009 and continued to operate until 2018, has the honor of discovering the largest number of exoplanets. The telescope has definitively discovered 2,342 exoplanets and provided indications of the existence of another 2,245 planets.

Types of extrasolar planets

Our solar system is home to eight planets, divided into two groups: rocky planets and gas giants. The four inner planets of the solar system, namely Mercury, Venus, Earth, and Mars, are rocky. At the same time, the four outer planets of the solar system, namely Jupiter, Saturn, Uranus, and Neptune, are classified as gas giants. Most of the planets that were discovered in the orbit of other stars are either rocky or gas giants. However, gas and rock giants can be divided into groups and subgroups.

Stone worlds

Planet Kepler 22b
An artist’s rendering of Kepler 22b, a distant, possibly super-Earth planet

The rocky planets themselves are divided into two categories: small rocky planets and so-called super-Earth planets. Small rocky planets are the type of planets that are also found in the solar system. Although the rocky planets in the solar system differ from each other, they all fall into one category.

However, exoplanets do not exist in the solar system, yet they are one of the most common planets in the Milky Way. These planets, as their name suggests, are a kind of rocky planet larger than Earth. According to a more precise definition, the rocky exoplanets are at least twice the size of Earth.

The mass of super-Earths can reach up to ten times the mass of the Earth. Scientists still do not know at what point the planets lose their rocky surface and become gas planets. However, in the range of 3 to 10 times the mass of Earth, there may be super-Earths with different compositions, such as blue worlds, snowball worlds, or even planets like Neptune that are made of very dense gas. As a result, heavy super-Earths that have turned into gas giants can be classified as sub-Neptunian or mini-Neptunian planets.

Gas giants

Hot JupiterArtist’s rendering of hot Jupiter orbiting its star

Gas giants are divided into three categories: gas giants, ice giants, and hot Jupiters. Simple gas giants are called worlds like Jupiter and Saturn. These heavy worlds are usually located in orbit far from their star, have dense atmospheres mostly composed of hydrogen and helium, and do not have a solid surface.

On the other hand, planets like Uranus and Neptune are called ice giants. Although the predominant composition of all gas giants is hydrogen and helium, ice giants are a type of gas giant with ice concentrations in their atmosphere. For example, both the planets Uranus and Neptune have large amounts of chemicals such as methane, ammonia, and water. Ice giants are usually located in the outer reaches of their star system; Where ice is found in high concentrations.

Gas giants and ice giants can be seen in the solar system. However, the third type, hot Jupiter, does not exist in our solar system. A hot Jupiter is a gas giant that is in a very close orbit from its parent star. This orbit can be even closer to the Sun than the orbit of Mercury; Therefore, hot Jupiter planets usually have hellish temperatures in their atmospheres, hence the nickname hot Jupiters.Introduction of extrasolar planets

Although exoplanets are classified in the group of rocky planets such as super-Earths or gas and ice giants and hot Jupiters, some planets violate the existing classifications and the number of these types of planets is increasing day by day. In this section, we introduce some of the most interesting exoplanets that have been discovered so far.

TOI-1452b, a blue world candidate

Planet TOI 452bIllustration of TOI 1452b, a super-Earth planet.

The planet TOI-1452b is located in the orbit of a red dwarf star at a distance of 100 light-years from Earth. Researchers discovered this planet through the blocking of starlight and its fluctuations.

Based on the obtained information, the planet TOI-1452b is almost 70% larger than the Earth and therefore it is included in the group of super-Earth planets. The planet also orbits its star once every 11 days. The density of this planet indicates that it has a liquid ocean surface as well as rocky and metallic compositions like planet Earth. Surprisingly, water makes up 30% of TOI-1452b’s mass. While water on earth is only 1% of its mass.

WASP-39b, the first planet with a carbon dioxide atmosphere

Planet wasp39bAn artist’s rendering of the exoplanet WASP 39b

The James Webb Telescope’s Near-Infrared Spectroscopy (NIRSpec), closely observing the exoplanet WASP-39b, found clear evidence of carbon dioxide in its atmosphere. This is the first time that this familiar gas has been discovered on Earth in a planet outside the solar system. The spectrum of 3 to 5.5 microns, which is the infrared ratio of the transmission spectrum, is useful not only for detecting carbon dioxide but also for water and methane, which are all indicators of life.

WASP 39b, with a temperature of 870°C, is a hot Jupiter-type planet about 700 light-years from Earth. The mass of this planet is equal to a quarter of the mass of the planet Jupiter, but its diameter is 1.3 times larger than Jupiter. The planet also orbits a Sun-like star at such a high speed that it completes its orbit in just four days.

WASP 103b, the rugby ball planet

Planet wasp103bA rendering of the planet wasp103b that resembles a rugby ball.

WASP-103b, shaped like a rugby ball, is the first non-spherical exoplanet ever discovered. This planet, which completes its orbit around its star in less than a day, has strong gravitational forces that have turned it into a rugby ball.

The Cheops telescope of the European Space Agency discovered this strange planet in the constellation of Hercules. The planet WASP 103b, twice the size of Jupiter, is very close to its star.

51 Pegasi b; The first planet around a Sun-like star

Planet 51pegasibIllustration of the exoplanet Pegasi B 51

Although 51 Pegasi b is not the first exoplanet discovered, it can be considered the first example discovered around a Sun-like star. In addition, this planet has no resemblance to the planets we know. This huge world completes its star orbit in just a few days.

In 2015, the atmosphere of 51 Pegasi b was studied in the visible spectrum. As a result, researchers were able to find out the real mass or orbital orientation of this planet through its light.

PSR B1620-26b; The oldest known planet

Ancient planet psrb16bPSR B1620 is the oldest known exoplanet.

The name PSR B1620-26b may not be as easy to pronounce as many exoplanets. However, this planet, with an approximate age of 12.7 billion years, is the oldest planet ever discovered. This planet is only slightly younger than the age of the entire universe. This ancient planet orbits a pulsar as well as a superdense white dwarf at the same time. These two stars revolve around each other and the gas giant planet also revolves around their gravitational axis.

Gliese 876d; rocky planet

Planet Gliese 876dIllustration of the rocky planet Gliese 876d

The planet Gliese 876d is only 15 light-years away from Earth, and due to its small size, it belongs to the group of rocky planets. Of course, this planet is slightly bigger than our Earth. By all accounts, Gliese 876d is a hell of a world. This planet is very hot, yet since its discovery in 2005, it has been considered important evidence for the existence of rocky worlds outside the solar system.

Kepler-11f; gas dwarf

kepler11f planetSome planets like Kepler 11f are mini-Neptunes.

There is a problem with the classification of smaller exoplanets; So far, we have observed several planets in space that are larger than Earth but smaller than Neptune; But we don’t have such a group in the solar system. For this reason, it is difficult to guess that rocky planets like Mars and Earth can grow to what extent? Or exactly in what dimensions do they become gas giants like Uranus and Neptune?

Kepler 11f is a mini-Neptune planet. The density of this planet shows that it has an atmosphere similar to Saturn and a small rocky core. This planet led to the creation of a new category called gas dwarf, which does not exist in our solar system.

Kepler-452b; Earth-like planet

Planet Kepler452bThe Kepler 452b planet can be considered the most Earth-like planet.

Kepler 452-b can be considered the most Earth-like planet ever discovered. The star of this planet is the same size as the sun and its year is slightly longer than the Earth’s year. Of course, this planet is slightly larger than Earth, but it is definitely located in the life belt of its star.

However, there are a few problems with Kepler 452b: First, the planet is more than 1,000 light-years away from Earth, so we’ll never reach it. It is also 1.5 billion years older than Earth, so it can be said that its host star has grown so much that it has made the planet uninhabitable. So maybe it was Earth’s twin many years ago.

Search for life in extrasolar planets

One of the biggest questions of mankind is whether there is life outside the earth. The James Webb Space Telescope, launched in 2021, has found evidence of the essential ingredients for extraterrestrial life: a mixture of gases in the atmospheres of Earth-like exoplanets. This telescope was able to discover atmospheric signs similar to Earth, such as oxygen, carbon dioxide, and methane, which are strong indicators of possible life.

Probably, future telescopes will be able to detect the signs of photosynthesis, which is the conversion of sunlight into chemical energy necessary for plants. Or maybe they can detect gases and molecules from animal life. Also, extraterrestrial intelligent life probably creates atmospheric pollution that can be detected from a distance.

Life on an extrasolar planetIn the area of ​​the life belt, it is possible for liquid water to flow on the surface of the planet.

So far, more than 5,000 exoplanets have been discovered, but their total number can reach trillions. One of the best tools for scientists to increase the accuracy of searches is the area known as the life belt. As we said in the previous section, the life belt is a distance from the orbit of a star whose temperature is suitable for the flow of surface liquid water.

Many other conditions are necessary for the formation of life on exoplanets: first of all, the size of the planet and the right atmosphere are important. Also, the host star must be stable and not emit deadly flares. Lifebelt is just one way to narrow down searches. So far, many Earth-like planets have been discovered, however, more advanced tools are needed to increase the accuracy of searches.

Interesting facts about exoplanets

In the era of innovation, we are getting closer to the outside world every day. Searching for extrasolar planets has been one of the latest human space adventures. In this section, we discuss interesting facts and points about these mysterious objects.

Detecting the color of an exoplanet for the first time in 2013

The study and discovery of extrasolar planets began in the ’90s, But it was in 2013 that researchers were able to identify the color of an exoplanet for the first time. Based on a measure called reflectivity, astronomers obtained a dark blue color for the planet HD 189733b. It was from this point that the colors of other exoplanets were obtained. For example, the color of the planet GJ 504b is purple. According to astronomers, helium planets are mostly white or gray.

There are 10 billion Earth-like planets in the Milky Way

According to estimates, the number of Earth-like planets in the Milky Way alone reaches ten billion. Kepler 22b was discovered in 2011 as the first exoplanet in the habitable belt. When the news of this discovery spread, people immediately fantasized about life on such a planet. However, the distance of 587 light years from Earth means that we have to spend thousands of years to reach this exoplanet. This planet is currently under investigation.

Earth-like planetThere are 10 billion Earth-like planets in the Milky Way

NASA’s Kepler space telescope has discovered the most exoplanets

NASA’s Kepler Space Telescope, which was launched for the first time in 2009, was dedicated to the search for exoplanets. Initially, the Kepler mission was supposed to last only 3.5 years, however, this spacecraft continued its investigations until 2018. This telescope definitively discovered more than 2,600 exoplanets.

The possibility of exoplanets around stars with high metallicity

Most of the physical materials in the world are composed of hydrogen and helium. Metallicity is the term astronomers use to describe elements other than helium and hydrogen. According to data collected by the Kepler telescope, stars with more diverse elements are more likely to host exoplanets in their orbits.

Using the gravitational microlensing method to observe exoplanets

In the gravitational microlensing method, a star other than the exoplanet host is used. When a star passes in front of another star, its gravity acts like a lens that magnifies the light of the other star. If the lensed star has a planet in its orbit, the exoplanet’s mass increases the magnification effect. Astronomers used this method to search for more than 20 exoplanets.

Most exoplanets were discovered through radial velocity

The general rule for identifying exoplanets is to observe the motion of their star. This method, which is also called Doppler oscillation, has been the most successful method for discovering exoplanets, so far 400 planets have been discovered this way. The radial velocity of the star changes due to the gravitational pull from the planet around it. In this case, the star seems to be sliding.

The transit method is the easiest way to find exoplanets

The transit method, which from our point of view is the burning of a star, is one of the common methods for discovering exoplanets. Using this method, astronomers can estimate the orbits and mass of exoplanets from Earth through their flickering frequency.

Exoplanets can orbit more than one star

Unlike the Solar System, where planets orbit a single star, some planetary systems can have more than one star. These double or triple systems provide unique contexts with multiple radiation sources.

Exoplanets can have harsh climates

Some exoplanets show strange weather phenomena. Hot Jupiters, for example, can reach scorching temperatures and violent storms.

Some exoplanets have strange orbits

Not all exoplanets follow an elliptical or circular pattern of orbital motion. Some planets have eccentric, elongated orbits, taking an adventurous journey around the axis of their star. Exoplanets can have unique atmospheres

By analyzing the light passing through the atmosphere of exoplanets, scientists can gain interesting insights about the composition of these planets. The atmosphere of some extrasolar planets has elements such as iron vapor, carbon dioxide, and even methane.


An exoplanet is a planet outside the solar system that is classified into different groups and types. The first group are rocky planets similar to Earth or larger than Earth, which are also called super-Earths. Super-Earths can eventually become gas planets known as mini-Neptunes. The next group is the gas planets, which are divided into gas giants, ice giants, and hot Jupiters.

So far, more than 5000 exoplanets have been discovered and confirmed, and this number is increasing day by day. According to estimates, there are only 10 billion Earth-like planets in the Milky Way. Earth-like planets are usually located in the life belts of their stars. In the zone of the life belt, the temperature of the planet is so suitable that it is possible for surface liquid water to flow on it, and this feature can increase the potential for life. Researchers hope to get more data from exoplanets by building more advanced telescopes because understanding exoplanets will help us to better understand our planet and the world around us.


What are the obstacles on the way for humans to reach Mars?





Sending the first humans to Mars has not only been a dream for countless generations, but also dates back to the early modern era. Also, one of the topics of the space age is the planning of such missions, and it is considered an integral part of the current vision for the future of space exploration, but this long-standing dream has not yet been realized.

What are the obstacles on the way for humans to reach Mars?

In the last 20 years, the public has heard claims that NASA will send the first humans to Mars by the early 2030s. First the moon, then to Mars! This is the plan NASA seemed to be sticking to for a while.

According to IA, in recent years, other players, including the China National Space Agency (CNSA) and Elon Musk’s commercial space giant, SpaceX, have joined the “race for Mars“. According to several sources, China, like NASA, plans to build infrastructure on the moon that will help the country send its first astronauts to Mars as early as 2033.

SpaceX’s plans are even more ambitious, with missions planned for the late 2020s and plans to build a self-sufficient city on Mars before the end of the decade. Unfortunately, many naysayers have said that reaching Mars by 2033 or sooner is unrealistic.

There have also been numerous delays along the way, showing how the entire Moon-to-Mars mission could fall behind its planned timeline.

2040 may be a more likely year for a manned mission to the surface of Mars, according to statements issued last summer by Deputy Administrator Jim Reuter. While delays are common in spaceflight, a seven-year delay seems significant and raises questions.

For example, why does such a mission take so long? And what would it take to send the first humans to Mars?

Answering these questions requires recalling memories.

The journey begins

Efforts to carry out missions to Mars began in 2004 with the announcement of a project called Vision for Space Exploration (VSE) by NASA. This vision came in response to the Space Shuttle Columbia disaster, the state of human spaceflight at NASA, and a desire to rekindle public interest in space exploration.


The project’s specific goals included completing the International Space Station (ISS), retiring the Space Shuttle by 2010, and creating a new fleet of heavy launch vehicles that would enable manned missions to the Moon, Mars, and beyond.

The plan included a series of robotic missions to the Moon to prepare and support future human exploration activities that began in 2008.

The plan also supports the use of lunar exploration, science, and resources to develop the technologies and systems necessary to support sustainable human space exploration to Mars and other destinations.

Meanwhile, NASA will resume sending robotic missions to Mars to search for evidence of life and prepare for the eventual arrival of manned missions. This led to the formation of NASA’s Mars Exploration Rover (MER) program, which consisted of the Spirit and Opportunity rovers and the Curiosity and Perseverance rovers.

Following this, the NASA Authorization Act of 2005 officially launched the Constellation Program.

The program called for a new group of launch vehicles, including a crew launch vehicle (CLV) and a cargo launch vehicle (CaLV), which led to the design of the Ares I and Ares V rockets.

Other vehicles included the Crew Exploration Vehicle (CEV) and the Lunar Surface Access Module (LSAM).

NASA planned to use Eriz 1 and 5 back-to-back to send astronauts to the Moon and Mars. The crew was to be launched using a two-stage Ariz-1 rocket capable of delivering 56,000 pounds (25,400 kg) to low Earth orbit (LEO). The payload was sent separately on Ariz 5, which was capable of sending 88,000 kg into low Earth orbit. This program came to fruition in 2009 when NASA completed the Launch Stop System (LAS) and the first stage of the Ariz 1 rocket. The second one was successfully tested on October 28 of the same year.

Unfortunately, the Constellation program was canceled in 2010 due to the global financial crisis known as the “Great Recession” that began in 2007-2008. Almost a year later, the Obama administration signed off on the Mission to Mars.

Details and goals of the program were published in the NASA Authorization Act of 2010 and the US National Space Policy of the same year. NASA’s priorities in this matter are summarized as follows:

Our next step is deep space, where NASA will send a robotic mission to capture and guide an asteroid into lunar orbit. Astronauts aboard the Orion spacecraft will explore the asteroid in the 2020s and return to Earth with samples. This experience in human spaceflight beyond low-Earth orbit will help NASA test new systems and capabilities, such as solar electric propulsion.

Beginning in fiscal year 2018, NASA’s powerful Space Launch System rocket will enable these missions to test new capabilities. Human missions to Mars will rely on Orion, an evolved version of the Space Launch System rocket that will be the most powerful launcher ever to fly.

In many ways, “Journey to Mars” picked up where the Constellation program left off.

While the Ariz 1 rocket and lunar lander were discarded, the Ariz 5 launcher and crewed exploration spacecraft were retained and became the basis for the Space Launch System (SLS) and the Orion spacecraft.

Timelines were also updated, with missions to Mars planned for the early 2030s.

The proposed journey will include three phases and 32 launches of the Space Launch System between 2018 and 2030. These missions send all the necessary components to space between the Earth and the Moon and then to space near Mars before landing the crew on the surface of Mars.

Phase one, called the Earth-based phase, will focus on further long-term studies on the International Space Station until 2024 and testing the Space Launch System and Orion spacecraft. This included Exploration Mission 1 (EM-1) in 2018, the first flight of the Space Launch System, and the second unmanned test flight of Orion.

As with the Constellation program, NASA also planned to launch an Asteroid Redirection Mission (ARM) in 2020, in which a robotic spacecraft would rendezvous with a near-Earth asteroid and pull it into lunar orbit.

Exploration Mission 2 (EM-2) will include a manned flyby of the Moon and asteroid ARM between 2021 and 2023. At this point, NASA moves to Phase Two, shifting the focus from Earth to the space between the Earth and the Moon. The multiple launches of the space launch system will bring the important components of the mission to the lunar surface and orbit at this stage.

Since 2012, these elements have included the lunar gateway known as the Deep Space Habitat, an orbiting space station consisting of a Power and Propulsion Element (PPE), a Habitat and Logistics Base (HALO), a refueling supply system, and infrastructure. and has a communication module (ESPRIT), an international habitation module (I-Hab), and a reusable lunar lander.

Other elements include the Artemis Base Camp, which consists of a lunar base surface habitat, a habitable mobile platform, a Lunar Ground Vehicle (LTV), and a Deep Space Vehicle (DST). The spacecraft will integrate with Orion to transport a crew of up to four to Mars and other deep space destinations.

In the early 2030s, phase three (ground-independent) will begin, which will include essential elements delivered to Mars by a deep space vehicle. This second space station will be equipped with a reusable Mars lander that will allow the crew to perform scientific operations on the surface and then return to orbit.

A road map is formed

In 2017, NASA’s long-term vision to return astronauts to the Moon and Mars began. According to the National Aeronautics and Space Administration’s 2017 Transfer Authorization Act, NASA’s priorities for the Moon to Mars program were determined.

These priorities included continued development of the Space Launch System, Orion, the Lunar Gateway, and other critical mission elements. The bill also directed NASA to scrap the asteroid reorientation mission in favor of something more cost-effective. Other priorities included expanding the US commitment to the ISS and restoring domestic launch capability through the Commercial Orbital Transportation Service (COTS) and the Commercial Crew Program (CCP).

According to their timeline, the construction of the Moongate space station will be completed by 2028. The first manned missions to Mars will be launched from the Moon Gate in 2033. The crew will spend up to a year conducting science operationsthen make their return trip to Earth.


The spacecraft and crew will then spend 6 to 9 months en route, returning to the lunar gateway and landing on Earth with the Orion capsule. Subsequent missions are carried out once every 26 months. These missions will lead to the establishment of a long-term habitat on Mars, allowing for return visits. It could also deliver the first Mars sample to Earth, similar to how the Apollo astronauts returned moon rocks for analysis.

Read more: Can humans endure the psychological torment of living on Mars? 

However, by 2019, NASA was forced to reevaluate its priorities and long-term goals as the Trump administration inaugurated a new program.

As you can see, NASA’s long-term vision for the first manned missions to Mars has evolved since its inception 20 years ago, and even in its early stages, there were doubts that the timelines and commitments were realistic. With all these challenges, the most important pressure factors had not yet arrived. You can read these factors in the second part of this report.

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History of the world; From the Big Bang to the creation of the planet Earth




History of the world
The universe started from a singularity and continues to expand until today, 13.8 billion years old. in this article we’re going to examine the history of the world.

History of the world; From the Big Bang to the creation of the planet Earth

Since its launch in 2021, the James Webb Space Telescope has sent us spectacular images of the universe’s deep field. This telescope revealed fine details like a galaxy with an age of 13.1 billion. Such distant objects may not be visually impressive, appearing as fuzzy red blobs in images, but they can provide a fascinating glimpse into the universe’s infancy.

Space and time are intertwined. Light travels at a constant speed, so the images captured by telescopes like James Webb’s are actually images of the universe from millions or even billions of years ago. The higher the sensitivity and accuracy of a telescope, the more distant objects it can observe and thus display more distant times. As the most powerful telescope ever launched, the James Webb Space Telescope (JWST) is extremely sensitive. This telescope can theoretically see objects within 100 million years since the formation of the universe.

Table of Contents
  • The first moments
  • Initial plasma
  • The world becomes transparent
  • Cosmic Dark Age
  • The first habitable age
  • The first lights in the dark
  • Blooming cosmos with stars
  • Star seeds
  • The oldest known star
  • The oldest known planet
  • The formation of galaxies
  • Large-scale structures of the universe
  • Collision of galaxies
  • Massive black holes
  • The formation of the Milky Way disc
  • Overcoming dark energy
  • The birth of the sun
  • The formation of the earth
  • The first forms of life
  • Extraterrestrial life and alien civilizations

There are still many unknowns about the history of the universe, but telescopes like Webb’s can unravel these mysteries and reveal unprecedented detail.

History of the world

The first moments

The first moments of the worldThe universe was born about 13.8 billion years ago from the Big Bang.

The entire universe was created from an ancient and vast explosion that continues to this day. This spark , called the Big Bang, happened nearly 13.8 billion years ago. The Big Bang is the best hypothesis ever proposed for the existence of the universe. Although there is still no way to directly observe the Big Bang, this theory is well established and has been confirmed by many scientists over the past few decades.

In the first moments of the universe, a fraction of a second after the Big Bang, everything was inside a singularity, which is an infinitesimally small point of space with a very strange and high density that encompasses everything. In a few moments after the birth of the universe, the world was in an era known as Planck’s age. In this era, the whole world was so small that space and time had no meaning. Then, in less than a second, the universe entered a phase known as cosmic inflation, and for a moment, it expanded greatly. The infant universe consisted of a hot soup of subatomic particles and radiation, preventing any kind of structure from forming.

Initial plasma

The beginning plasma of the worldThe universe was initially filled with turbid, hot plasma.

The early universe was a highly viscous place filled with turbid plasma for several thousand years. This murky plasma was a mass of subatomic particles that were too hot to contract into atoms. The lack of transparency of the early world makes it impossible to see the events of that time; However, the early chapters of the universe’s history are of interest to many cosmologists because they represent a stage for the existence of everything.

Scientists believe that the early universe was filled with equal amounts of matter and antimatter, which eventually annihilated each other, leaving only a small amount of matter in the present universe. The question of why one of them was more remains a mystery and physicists are still trying to answer this question.

Eventually, the universe cooled and atoms and then strange molecules began to form. The first molecule that was formed in the world was made of only two elements, hydrogen and helium. These molecules finally made a compound called helium hydride. This chemical reaction actually created a helium compound that looks like it shouldn’t exist.

The world becomes transparent

Transparency map of the universeThe world became transparent after 300 thousand years.

On its 300,000 birthday, the world entered an era known as the age of recombination. It was during this period that atoms began to form, although the word “recombination” is a bit of a misnomer because it was during this period that everything was combined together for the first time. As the universe cooled enough, matter began to form atoms, and the universe became transparent for the first time. This transparency allowed the light left over from the Big Bang to spread throughout the universe.

The ancient Big Bang radiation marks the edge of the visible universe and can still be observed. As the universe continues to expand, the light in it is stretched, which astronomers witness in the form of the redshift phenomenon. The older the light of an object, the more it is stretched and moves to the red side of the spectrum like infrared and finally to longer wavelengths.

The initial light of the birth of the world is the most stretched light and the human eye cannot observe it. This light can be seen in all directions today as the cosmic background radiation (CMB). As seen in the image above, some speckled areas show slight fluctuations left over from cosmic inflation. These faint background rays are the last reflections of the birth of the universe.

Cosmic Dark Age

darkness of the universeThe world had no stars in the dark ages.

With the universe filled with atoms, light was finally able to move freely in open space. However, there was nothing in the universe capable of producing light. In fact, this age of the world is known as the age of cosmic darkness. In this period, the stars were not yet born and the space was full of silence and infinite darkness. The universe was in its infancy and there was nothing but dark matter with neutral helium and hydrogen, But it was in this darkness that the materials of the world gradually joined each other.

Finally, with the formation of the first stars, the world entered an era known as the Bazion, and the first stars shone. They emitted intense ultraviolet light in the dark and eventually removed the electrons from the new atoms; But even though the stars were shining for the first time in the universe, their light could not travel very far. Because the entire space was filled with a fog of hydrogen gas and blocked the light of the first stars. After some time, the starlight traveled further distances and reached us today.

The first habitable age

Early habitable ageAccording to calculations, the first habitable age started in 10-17 million years of the world.

According to human earth standards, any place with liquid water can be classified as habitable. As the early Earth cooled, the surprising truth was revealed that the entire universe was once at a habitable temperature. According to an article published in the International Journal of Astrophysics, this period is called the early habitable age. Based on this hypothesis, the question arises as to what exactly happened in a world where life theoretically existed everywhere. According to calculations, this cosmic age corresponds to the time when the universe was still 10 to 17 million years old.

Of course, scientists have differences in this hypothesis. According to an article in Nature that argues against this idea, life requires a hot-to-cold energy flow and cannot exist in a uniformly warm universe. Furthermore, at this early age it is not known whether the universe had stars or planets, or even oxygen to produce water. However, this hypothesis cannot be completely rejected. The first planets were probably formed in the first few billion years of the universe; So the hypothesis of an early habitable age is little more than a fascinating thought experiment.

History of the world

The first lights in the dark

The first lights of the worldThe first stars of the universe were composed of light elements.

The first stars of the universe were formed from the virgin material left over from the Big Bang and were the cause of the formation of the first heavy elements of the universe. These stars, which lacked elements heavier than helium, are known as population 3 stars (confusingly named stellar populations in the wrong order). Since these stars were responsible for the formation of the heavy elements of the universe, they must have existed at some point in history. These objects are expected to have formed between 100 million and 250 million years after the Big Bang.

According to the models, Population 3 stars were very massive and short-lived by today’s stellar standards. The lifetime of some of these stars reached only 2 million years, which is a long time from the human point of view; But on a stellar scale, it’s like a blink of an eye. When these stars ended their lives, they likely perished in unstable binary supernova explosions, the most violent type of stellar explosion in the universe. Although no stars belonging to this group have been observed so far, perhaps this trend will change with powerful instruments such as the James Webb Space Telescope.

Blooming cosmos with stars

The formation of starsSome stars of the Milky Way date back to 11 to 13 billion years ago.

We live in a season of the world known as the age of star formation. This age is the beginning of the stars shining in the dark and is actually the modern age of the world, in which the cosmic matter turns into stars, planets and galaxies. According to scientists, the era of star formation began approximately one million years after the Big Bang and will continue until the universe is 100 trillion years old. Until the very distant future, the birth, life and death of stars in the universe and the fusion of hydrogen into heavier elements will continue until hydrogen disappears completely.

Although stars are actively forming in the universe, there is a wide range from newly born stars to very old stars. Stars can live for billions of years. Red dwarfs, the smallest and most populous stars in the universe, live so long that their deaths have not been recorded until now because the universe is not old enough. Astronomers have also observed very old stars in the universe, some of which date back to the earliest days of the Milky Way, between 11 and 13 billion years ago. Stars like this have been observed for most of the history of the universe.

Star seeds

A star nebulaNebulae are breeding grounds for the formation of new stars

By weight, most of Earth is made up of chemical elements heavier than helium, which are made in the cores of stars. This process is known as nucleation. During the lifetime of a star, nuclear reactions combine light elements and produce heavier elements. In this way, elements such as carbon, oxygen, silicon, sulfur and iron are formed in the hearts of stars. When stars run out of fuel, they throw the elements they made back into the universe.

Stars fill the galaxy with elements by their birth and death over billions of years. Carbon, oxygen, and nitrogen are among the most abundant elements made by smaller stars. As these stars die, their outer layers form a stellar nebula. From this example, we can refer to the Southern Ring Nebula, whose image was published by the James Webb telescope.

The life of the biggest stars also ends in a supernova explosion. These explosions not only fill galaxies with heavy elements such as iron, but their shock waves can be the basis for the birth of new stars.

History of the world

The oldest star in the worldThe oldest star in the universe was formed only 100 million years after the Big Bang

The hunt for the oldest stars in the universe is one of the fascinating fields of astronomy that can help scientists understand the early days of the universe. The oldest star ever discovered is HD 140283. The star is so old that the first estimates of its age are older than the universe itself. However, this effect is an illusion caused by the uncertainty in the estimates. Therefore, measuring the age of a star is not an easy task.

According to another research in the Journal of Astronomy and Astrophysics, the age of HD 140283 was estimated to be almost the same as the age of the universe, i.e. 13.7 billion years. In other words, this star was probably born a hundred million years after the Big Bang, and thus it is one of the first generation of stars that were born in the world. This star is metal-poor, or in other words, has a small number of chemical elements heavier than helium, and thus it is placed in the category of population 2 stars. Such stars are among the oldest objects that have ever shone in the universe. Based on the ratio of chemical elements, these stars are survivors of early stars from the early days of the universe.

The oldest known planet

The oldest planet in the worldThe oldest planet in the world is nearly 12.7 billion years old.

No one knows exactly when the first planets formed, but they seem to be able to outlive stars. The oldest known planet orbits two dead stars, one of which is a pulsar and the other a white dwarf. Both stars are stellar wrecks that have run out of fuel and have released much of their chemical material into their galaxy. The mentioned pulsar is called PSR B1620 and the planet located in its orbit is known by the nickname Methuselah. This planet, which is a kind of gas giant, is not unlike the planet Jupiter.

According to estimates, the lifespan of Methuselah reaches 12.7 billion years, but this age is not exact. There is no good way to estimate the age of planets, so this estimate is based on other stars in the Methuselah cluster. Globular clusters, such as the Methuselah host cluster, are full of stars that formed at the same time.

According to the research of Science magazine, the existence of the ancient planet Methuselah offers interesting hints about the time of formation of the oldest planets. If the estimates are correct and Methuselah is really 12.7 billion years old, we can say that the planets were formed earlier than we think. In other words, Methuselah may not be the only ancient planet in our galaxy.

The formation of galaxies

The formation of galaxiesGalaxies usually come together in several clusters

When the universe was only 200 million years old, the first galaxies were formed. The discovery initially surprised astronomers because they thought galaxies formed much later. Early galaxies were not similar to today’s massive galaxies. Rather, they were shapeless clouds of irregular gas and dust. These galaxies, accompanied by a wave of star birth, eventually became the massive galaxies that fill the universe today. It seems that the Milky Way galaxy was formed approximately 13.6 billion years ago. Our galaxy was then an unrecognizable mass of stars, not unlike the present spiral.

The oldest galaxy ever discovered was formed 300 million years after the Big Bang. This galaxy is called HD1 and the James Webb telescope played an important role in determining its age. HD1, if confirmed, would be the oldest galaxy ever seen by astronomers and could offer fascinating insights into the formation of the universe’s first galaxies. The formation of galaxies is still a mysterious research field full of unanswered questions. Helping to solve these questions will be one of the main goals of the James Webb telescope.

Large-scale structures of the universe

The large-scale structure of the universeGalaxies are held together by gravity and form large-scale cosmic structures

Much of the world seems to be an empty void, But the universe has complex structures on very large scales. The universe is covered with an array of dark matter filaments that form a web-like structure. This network of dark matter, called large-scale structure, shapes the universe and causes galaxies to fall into regular patterns. The gravity of the large-scale structure causes both dark and visible matter to lie next to each other. By examining this structure, we can find signs of the youth of the world.

Deep background images, such as the James Webb Telescope image, can reveal how galaxies fit together. These structures are actually the largest visible structures or galaxy strings in the universe, held together by gravity. In addition, the structures are not random but have an order that still fascinates researchers. Galaxies and large galaxy clusters appear to be evenly spaced in the galactic strings, resembling a pearl necklace. There are still many uncertainties about large-scale structures.

Collision of galaxies

Collision of galaxiesSome galaxies collide and form larger galaxies.

Gravity pulls everything in the universe together, and the heavier the mass, the greater this attraction. Galaxies are among the heaviest objects in the universe, whose formation and evolution are still a matter of discussion and their evolution is strongly influenced by their interaction with each other.

Galaxies usually tend to form groups or clusters that come together due to gravity and start interacting when they are close to each other. The gravitational pull of galaxies leads to the creation of lethal forces. In the most dramatic examples, galaxies can collide and their merger may take billions of years.

Galactic collisions can lead to the formation of new stars; Because the change of gravitational forces causes disturbances on huge scales. Some stars are ejected into the dark intergalactic space, while others are trapped by the gravity of supermassive black holes at the center of colliding galaxies. As the galaxies merge, their spiral arms are eventually destroyed, and the two galaxies eventually become one massive elliptical galaxy. In this way, some of the largest galaxies in the universe are formed. Some galaxies also grow by absorbing smaller galaxies. According to some evidence, the Milky Way has experienced such a collision in the past, and its signs can be seen in the form of remnants of galaxies that it has absorbed in the past.

History of the world

Massive black holes

QuasarQuasars are caused by the feeding of the black hole from the surrounding matter.

The largest galaxies, such as the Milky Way, have a supermassive black hole at their center; Although how these black holes formed is still a mystery, it is clear that they are very old. The European Space Agency has released an image of an ancient galaxy known as UDFj-39546284, which appears to be a small red dot in the image. This spot is actually the oldest quasar observed by astronomers and dates back to 380 million years after the Big Bang.

Quasars are among the brightest objects in the world, which are created by the feeding of the supermassive black hole at the center of a galaxy from the surrounding material. The big question here is how these black holes have reached these dimensions at a high speed. According to a study published in the journal Nature, supermassive black holes appear to have formed suddenly from turbulent cold gas in the early universe. In the right conditions, black holes were formed with great intensity and suddenly as a result of the collapse of streams of initial materials grew to dimensions exceeding 40,000 times the mass of the Sun.

The formation of the Milky Way disc

milky way discIn the first 3 billion years of its existence, the Milky Way had no spiral arm.

Today, the Milky Way is a spiral galaxy, but it hasn’t always been this way. The spiral galaxy formed in a galactic disk, but the Milky Way disk formed about ten billion years ago. This means that our galaxy spent its first three billion years without a disk and therefore had no spiral arm.

The disk of a spiral galaxy contains a large part of the material of that galaxy. In such galaxies, star birth often occurs in spiral arms, as stars are formed from vast clouds of gas and dust slowly swirling around the galactic core. How and why spiral arms and disks are formed is still not completely clear, although this phenomenon has been observed frequently in the sky.

Some galactic disks appear to be very old. The oldest galactic disk ever seen is the Wolf disk. This old spiral galaxy dates back to when the universe was only 1.5 billion years old. Of course, due to the distance of this galaxy, we have no information about its new appearance.

Overcoming dark energy

Dark energyMysterious dark energy is responsible for accelerating the expansion of the universe.

One of the milestones in world history can be related to dark energy; The mysterious force that controls the expansion of the universe. No one knows exactly what dark energy is, although astronomers can measure its effects. Until a long time ago, the universe was in a tug-of-war between the force of gravity and the repulsive force of dark energy. At some point around 5-6 billion years ago, dark energy won the race. As the universe continued to expand, dark energy overcame gravity and accelerated the expansion of the universe.

The effect of dark energy on the future of the universe is still unclear. Without knowing more about dark energy or how it works, there’s no way to know. Although dark energy appears to make up a large part of the universe, its specifics are still shrouded in mystery. According to a possibility, this energy can be one of the inherent characteristics of space itself.

The birth of the sun

The birth of the sunThe sun was formed about 4.6 billion years ago from a cloud of gas and dust.

The sun is almost a third of the entire universe. This star was formed about 4.6 billion years ago. With the formation of the sun, the clouds of gas and dust around it formed planets such as Earth and many moons of the solar system.

The sun is one of the population’s 1 stars. Such stars are among the newest stars in the universe and are rich in heavy elements, examples of which can be found on Earth. According to a hypothesis, the shock wave resulting from a supernova was the cause of the formation of the solar system from vast dust clouds. The traces of this supernova exist in the form of radioactive isotopes in the entire solar system; So a star died so we could live.

The formation of the earth

The formation of the earthEarth was formed from the joining of asteroids.

According to scientists, the story of the formation of the earth goes back to 4.6 billion years ago. Our planet formed in a disk-like cloud of gas and dust around the primordial Sun. Inside this disk, gas and dust particles of different sizes were rotating at different speeds in the orbit of the sun and in this way, they collided and stuck to each other. Finally, the tiny particles turned into huge rock fragments and objects called asteroids, whose diameters ranged from one to hundreds of kilometers.

Asteroids eventually gained enough gravity to clear their orbits and attract other bodies through collisions, becoming larger bodies several thousand kilometers in diameter and forming planets.

Single cell lifeThe first life on earth dates back to 3.7 billion years ago.

Life on Earth is the only life we ​​know of in the entire universe. Life first appeared about 3.7 billion years ago, shortly after the formation of the Earth itself. Thus known life is roughly a quarter of the age of the universe, although the complex life that would eventually become humans is much more recent.

Carbon is an essential element for life and appears to have been unavailable until 1.5 billion years after the Big Bang. For this reason, it is still not possible to estimate with certainty the first form of life in the entire universe. Maybe other parts of the world have different chemistry or different elements than life on Earth.

Extraterrestrial life and alien civilizations

planet EarthLife in other parts of the world may be chemically different from life on Earth.

To quote the late astronomer Carl Sagan, “We are a way of knowing the world.” Humans are part of the world like the most distant stars or galaxies. In other words, at least a part of the world is capable of thinking and observing other parts. The oldest early humans appeared on earth approximately 2.4 million years ago; This means that humans and our direct ancestors only existed in 0.02% of the entire history of the world. On a cosmic scale, it seems like we were born just yesterday. However, humans may not be the only civilization in the world.

The question about the existence of other civilizations in the galaxy has a long history. Half of all Sun-like stars could host habitable universes; Therefore, there is no shortage for the formation of civilizations. According to a relatively conservative study, there should be at least 36 space civilizations capable of communicating in the Milky Way. According to another research, there are more than 42 thousand civilizations in the Milky Way. Currently, there is no way to find out the existence of these civilizations. With more accurate telescopes, we may be able to find evidence that we are not alone in this infinite universe.

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A mystery that is solved by the China’s Chang’e-6 probe!




Chinese explorer

China’s Chang’e-6 probe, launched to retrieve samples from the far side of the moon, has a big mystery to solve about Earth’s moon.

A mystery that is solved by the China’s Chang’e-6 probe!

China’s Chang’e-6 mission, which is currently on its way to bring back samples from the far side of the moon, will help investigate theories about why the far and near sides of the moon differ.

According to Space, Changi 6 is expected to land in early June in the Apollo impact basin, which is located within the larger South Pole–Aitken basin.

The Aitken Antarctic Basin is the largest collisional feature of its kind in the solar system, with an area of 2,400 x 2,050 km. This basin was formed about 4.3 billion years ago, which is very early in the history of the solar system.

Although the Apollo Basin is younger, it is the largest impact site within the Aitken Antarctic Basin. Apollo has a two-ring structure, the inner ring consists of mountain peaks with a diameter of 247 km, and the outer ring is about 492 km wide.

The Chang’e-6 mission was launched on May 3 from the Wenchang Satellite Launch Center in Hainan Province, located in southern China, and went to the moon on a Long March 5 rocket.

As the first mission to bring samples from the far side of the moon, Changi 6 is supposed to bring back about two kilograms of precious lunar material. The far side of the moon is a relatively unknown place. The fact that we can’t see the far side of the moon from Earth adds to its mystery. For the first time, the Soviet Union’s “Luna 3” spacecraft photographed the far side of the moon in 1959.

With that photo, scientists around the world were amazed to see how different the far side of the moon is from the side we are familiar with. Although both the far and near sides have many craters, the near side also contains vast volcanic plains called “lunar maria” that cover about 31% of it.

The far side of the moon is opposite and volcanic plains cover only about 1% of it.

So how did the far side and the near side become so different? It seems that the thickness of the shell is one of the factors. In fact, NASA’s GRAIL mission found in 2011 that the far-side crust is on average 20 kilometers thicker than the near-side crust.

The reason for this is thought to be that our moon was formed from debris from the impact of a Mars-sized planet on Earth about 4.5 billion years ago. As the Moon formed from that debris, it became tidally locked. This means that it always shows the face of our planet.

The surface of the earth was completely melted by that big impact and it radiated heat towards the near side of the moon and kept itself molten for a longer time. Scientists believe that the rock vaporizes on the near side and condenses on the colder side, thickening the crust on the far side.

Hong Kong University (HKU) researcher Yuqi Qian is one of the lead researchers on a new project that shows that a sample to be returned to Earth by Chang’e 6 could test this theory. Keyan said: Basic findings show that the difference in crustal thickness between the near and far sides may be the main cause of the difference in the moon’s volcanism.

In places like most distant parts where the Moon’s crust is thick, magma can’t seep through fractures to the surface. In areas such as the near side where the crust is thin, fractures can allow magma to seep in and lead to lava eruptions.

The Aitken and Apollo Antarctic Basins, despite both being on the far side of the Moon, create contradictions. That’s because they’ve gouged deeply into the Moon’s crust, and at the base of these giant impact sites, the crust is thinner than elsewhere on the far side. Volcanic plains also exist within these basins, but only five percent of their area is covered by basalt lava. This limited amount of volcanism seems to contradict the conventional idea that crustal thickness dictates volcanic activity. This creates a paradox in lunar science that has been known for a long time.

An alternative possibility suggests that the near side could contain more radioactive elements than the far side. These elements may have generated heat and led to the melting of the lower mantle. As a result, much more magma has formed and a thinner crust has formed on the near side. Hence, the volcano is more in this area.

However, by landing on one of the few volcanic plains on the far side, Chang’e 6 could provide samples to directly test such theories. In particular, the Apollo Basin area where Chang’e 6 will land contains a variety of materials that require investigation.

Some evidence shows that there were two major volcanic eruptions in this area. Scientists believe that one of them covered the entire region in magma containing a small amount of titanium around 3.35 billion years ago. The other, which probably occurred 3.07 billion years ago, probably contained titanium-rich magma and erupted near the Chaffee S crater. Thus, the thickness is reduced.

Read more: Discovering new evidence of the impact that formed the Earth’s moon

New research shows that bringing samples from near the Chafi S crater will bring the most scientific benefits. This area has titanium-rich basalt in the upper part, titanium-free basalt in the lower part, and various pieces of projectile material from the impact.

“Joseph Michalski” (Joseph Michalski), a researcher at the University of Hong Kong and one of the researchers of this project said: “Diverse sample sources provide important information to answer a set of scientific questions about the Moon and the Apollo Basin.”

These diverse samples can also provide scientists with information about magmatic processes occurring on the far side of the moon. By comparing them with nearby samples brought back to Earth by the Apollo missions, scientists may be able to answer the question of why the number of volcanoes on the far side of the Moon is so limited.

This research was published in the journal “Earth and Planetary Science Letters”.

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