Space
Billions of planets in the Milky Way galaxy; Hope to find extraterrestrial life!
How many planets does the Milky Way galaxy have? Do we know the number of stars? Has life ever been discovered on one of the planets?
Billions of planets in the Milky Way galaxy; Hope to find extraterrestrial life!
If you are one of those people who are interested in the night sky, you must have watched the arc of the Milky Way galaxy in a clear dark sky away from light pollution. Watching this astonishing sight is one of the most special experiences of every human being, which is accompanied by many questions. For example, maybe you want to know how many planets the Milky Way has. Or how many stars are inside this galaxy? Has life been found elsewhere in this galaxy? In this article, we are going to answer these questions.
Planets beyond the solar system
The existence of other planets in the Milky Way galaxy, especially planets that are similar to the planets of the solar system, has always been attractive to science enthusiasts. The quest to find these planets and understand their properties dates back to the distant past—especially when people were more excited about the subject when light pollution wasn’t around.
The question of whether there is life on other planets has been among other issues that mankind has been trying to answer for a long time. However, historical studies have shown that Earth was originally thought to be the only rocky planet in the universe, so no other living organisms would be found in the universe. This claim goes back to the belief of the Greeks at the time of the great scientist ” Aristotle “. At that time, it was believed that the Earth was the center of the universe and that everything in the universe revolves around the earth.
With this idea, the Greeks following Aristotle believed that there is no other rocky planet in the universe; Because soil, as the heaviest element in the universe, always tends to accumulate in the center of the universe (Earth). Therefore, no soil and stone can exist anywhere else in the world.
It took centuries for medieval thinkers to oppose Aristotle. The great scientist ” Copernicus ” discovered that the earth is not the center of the universe and everything does not revolve around it, but the sun is what the earth and other planets revolve around.
Thus, the debate about the existence and number of planets in the Milky Way continued until the studies of two great scientists, ” Galileo ” and ” Newton “, showed that the solar system with all its planets is only one of the countless planetary systems in the universe. But is it possible to provide an estimate of the number of planets in the Milky Way galaxy? The answer to this question required decades of technological progress for astronomers to make advanced observations of the cosmos and find planets outside the solar system that orbit a star like the Sun. These planets are called ” extrasolar planets “.
Discovery of the first exoplanet in the Milky Way galaxy
The first evidence of exoplanets was found in 1984. The ” Las Campanas ” observatory in Chile was able to record the gas and dust around the star ” Beta Pictoris “, which is a historical image in its own right. Previously, the scientist ” Emanuel Swedenborg ” proposed the theory that planets are formed from the accumulation of gas and dust particles, so planets can be found anywhere in the universe. At the time of the discovery of the first exoplanet, Swedenborg’s theory was highly accepted in the scientific community, and scientists suspected that the gas and dust observed was actually a protoplanet being formed.
In 1992, Alexander Welchchan and Dale Friel discovered the first extrasolar planet—not just the surrounding gas and dust—called PSR B1620-26 b. However, it was still unclear what star the planet was orbiting.
In subsequent studies, finally in 1995, ” Didier Clouse ” and ” Michel Maior ” managed to discover a planet orbiting a Sun-like star, thus the first extrasolar planet was discovered in history. This planet is called ” 51 Pegasi b ” and it revolves around the star ” 51 Pegasi “. This planetary system is about 50 light years away from Earth.
This discovery attracted the attention of scientists towards exoplanets. Now that the existence of other planets outside the solar system was proven, astronomers were curious to discover the secrets of the other planets of the Milky Way.
Trying to find more planets
Despite the discoveries made, the Earth’s atmosphere was an obstacle for further studies; Because it can simply make it impossible to discover exoplanets or study their atmosphere. So to find more exoplanets, ground-based telescopes were not very efficient. At first, scientists went to the only available option, the Hubble Space Telescope. They planned to use this telescope to study the light of the star that the exoplanet revolves around. Periodic changes in the brightness of this star indicate the rotation of the planets around it, and in this way, the rotation period of the planets can also be determined.
As the market for finding and studying these planets heated up, other telescopes were launched.
In 2003, Canada launched the MOST space telescope. The telescope was the size of a suitcase and was specifically designed to detect changes in the brightness of stars. MOST studied exoplanets for more than 15 years.
In the same year, NASA launched the Spitzer Space Telescope. The spitzer was a telescope equipped with an infrared observation instrument. Although this telescope was not specifically designed to study the planets of the Milky Way, its instruments provided a good opportunity to study the atmospheres of these objects. For example, astronomers made the first map of the atmospheric temperature of an exoplanet with the help of this telescope.
Spitzer Space Telescope
Spitzer Space TelescopeIn continuation of these studies, the European Space Agency deployed the ” CoRoT ” telescope in the Earth’s orbit in 2006. The purpose of this telescope was to identify the changes in the light of the stars when the planets pass in front of them. CoRoT was retired in 2014. This telescope discovered 34 exoplanets and more than 600 possible planets.
The most important event in identifying and studying other planets of the Milky Way was the launch of the Kepler space telescope in 2009. Kepler’s plan was to observe the light changes of more than 150,000 stars by observing a wide area of the sky in order to discover possible exoplanets.
Kepler’s advanced technology allowed astronomers to discover smaller planets that were previously undetectable. Kepler -10b was the first planet discovered by Kepler. This planet was actually the smallest planet discovered until that time. This rocky planet is only 1.4 times that of Earth.
Kepler continued to operate for 4 years until the first phase of its mission ended due to a technical failure. During this time, this space telescope was able to find more than a thousand exoplanets. In 2014, NASA engineers were able to readjust the Kepler telescope to begin the second phase of its mission.
During the peak of the second phase of its mission, Kepler discovered more than 1,200 more planets in the Milky Way. Astronomers estimate that about 40% of these planets are rocky and similar to Earth. The discovery of the closest exoplanet to Earth in the orbit of the star Proxima Centauri, the fascinating TRAPPIST-1 system with seven Earth-like planets, and the Kepler 90 system with eight planets are some of Kepler’s notable discoveries.
Kepler ended its mission in the fall of 2018. A few months before this date, NASA had sent the space telescope ” TESS ” into Earth’s orbit for a mission to detect exoplanets. The program of this telescope was two years, but it continues to operate. The James Webb Space Telescope, which is currently operating, is equipped with the most advanced tools for discovering and studying exoplanets.
Kepler space telescope
Kepler space telescopeThe planets of the Milky Way galaxy
Having said that, the number of exoplanets discovered by space and ground telescopes will exceed 5500 by 2024 . The Kepler space telescope has found a large part of these planets. Of course, it should be said that this is only the number of planets that astronomers have confirmed to be planets; There are thousands of other candidates among the findings of these telescopes that have not yet been definitively confirmed as planets. Accordingly, astronomers continue to discover exoplanets in older data.
With all that history we’ve covered, NASA says the age of Milky Way planet exploration has just begun. The number of planets discovered in the Milky Way is expected to increase at an unprecedented rate as data from the James Webb Space Telescope increases and artificial intelligence algorithms are used to detect planetary footprints in the vast amount of data.
However, scientists believe that the planets that have been discovered so far are only a small fraction of the planets that exist in the Milky Way galaxy. Astronomers state that in order to correctly estimate the number of planets, one must first estimate the number of stars. Then by estimating how many planets each star has around it on average, we can find the exact number of planets in the Milky Way. In this count, we should not forget the planets that do not revolve around a star or revolve around objects such as black holes.
Estimating the number of planets in the Milky Way is not an easy task. Astronomers estimate that the Milky Way has between 100 billion and 400 billion stars. This estimate was obtained using observational data from various telescopes such as the GAIA telescope, which studied about 1.7 billion stars.
Kepler’s 90 system with eight planets
Kepler’s 90 system with eight planetsConsidering these points, it is difficult to estimate the number of planets. Some astronomers believe that on average one or two planets orbit each star in the Milky Way galaxy. In this case, it can be estimated that the number of planets in the Milky Way galaxy is probably equal to the number of its stars or a little more. So, our galaxy has about 100 billion stars in the lowest state and probably about 800 billion stars in the highest state.
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Of course, we should not forget that this estimate is based on our limited observations. Instrumental limitations in observations still make it difficult for us to detect stars with multiple planets—except in the rare cases where stars with more than two have been discovered. Some also believe that these stars probably have more than two planets and this is the inability of our observational equipment to discover them. In other words, our observational equipment is not yet advanced enough to detect all the planets in a star. Many of the planets we have seen are very large or orbit very close to the star, making them easy to spot.
They believe that the solar system is a common system in the Milky Way and we must assume that each star has an average of 8 planets in its orbit. With this assumption, the possible number of planets in the Milky Way reaches 3.2 trillion in the maximum state. It should also be kept in mind that our information about the planets that are not in the orbit of the stars is very little and we cannot estimate them. With this calculation, the number of planets in the Milky Way galaxy can be estimated as several trillion!
Life on the planets of the Milky Way
The discovery of life on other planets requires the discovery of certain elements such as water and oxygen and some gases, which are known as the necessities of life. For this, astronomers use the spectroscopic method. However, the existence of these compounds is not the final confirmation of the presence of life on a planet, and more extensive studies should be done to be able to claim that life exists on a planet. Be careful that life does not necessarily mean what is observed on Earth, but other types of life can be witnessed on other planets.
However, so far, none of the millions of studies conducted with the aim of finding life on other planets have been successful, and the existence of life on a planet other than Earth remains an unsolved mystery.
Conclusion
In this article, we reviewed our knowledge about the planets of the Milky Way. We saw that these planets have had a prominent presence in the minds of humans since ancient times. We learned about the history of the discovery of the first exoplanets and saw what telescopes were sent to space to identify them. We read how many stars and planets the Milky Way has and how these numbers were estimated. Finally, we mentioned life on the planets of the Milky Way galaxy.
Frequently asked questions
How to prevent the earth from being baked by the scorching sun?
One day, the sun will enter a stage where life on Earth will no longer be possible and our planet will simply turn into a mass of iron and nickel. The good news is that if we do our best, we can keep our home livable even after the sun gets too hot.
Waking nightmare
The Sun will gradually become brutally brighter, hotter, and larger over time. Billions of years ago, the Sun was 20 percent dimmer than it is today when a series of molecules danced together to form living things. At that time, even the dinosaurs faced a fainter and smaller star.
Today, the sun is halfway through its hydrogen life and is still 4 billion years away from entering the death phase. However, in the next few hundred million years, the temperature and brightness that is giving life to our planet today will lead to its destruction. A few hundred million years is like a blink of an eye on a cosmic scale.
The sun is getting bigger and brighter day by day.
The sun sows the seeds of its destruction based on its fundamental physical properties. In the current conditions, our star consumes 600 million tons of hydrogen every second; So the atoms collide with each other in a nuclear inferno with a temperature of more than 15 million degrees Celsius. Of these 600 million tons, 4 million tons of hydrogen are converted into energy, which is enough to light up the entire solar system.
The fusion reaction is not completely clean and the resulting product is helium. Helium has nowhere to go because the deep convective cycles that continuously churn up the material inside the Sun do not reach the core, where helium is formed; Therefore, helium remains there in an unused, motionless, and stagnant form.
The sun consumes 600 million tons of hydrogen every second
At the present time, the Sun has not reached the high temperature and pressure in its core for helium fusion; So the helium stays there, increasing the overall mass of the nucleus without giving it anything else to fuse with. Fortunately, the sun can compensate for this process through hydrostatic balance.
The Sun is in constant equilibrium on the edge of a nuclear knife. On the one hand, energy is released from the fusion process, which, if left unchecked, can cause the sun to explode or at least expand. In front of this force, there is the gravitational weight of the sun, which exerts an inward force. If this force is released, the sun’s gravity will cause it to collapse and turn it into a black hole the size of an average city.
So what happens when an unstoppable force meets an irresistible force? A pleasant balance is established and the sun can continue to exist for billions of years. If for any reason the temperature of the inner nuclear inferno increases randomly, other parts of the star will also heat up and its outer layers will swell. In this way, the gravitational pressure decreases and the nuclear reactions slow down. If the Sun randomly contracts, more material will force itself into the core, where it will participate in the nuclear dance. The energy released as a result of this event causes the star to re-inflate to normal proportions.
The sun will destroy the earth before it dies.
On the other hand, helium, which is a nuclear product, replaces hydrogen and disturbs the balance. In this state, the sun has no choice but to pull internally, because gravity is unyielding. Meanwhile, nuclear reactions intensify and increase the temperature, which eventually causes the sun’s surface to glow and expand.
Slowly, as helium continues to accumulate in the core of the Sun, or any star of similar mass, the Sun grows larger and brighter in response to this process. It is difficult to predict exactly when this glow will become catastrophic for the Earth, this issue is strongly related to the relationship between the rays, the atmosphere, and the ocean; But the general estimate is that we have about 500 million years before life on Earth becomes impossible.
The burning sun will increase the temperature of the earth’s surface. It evaporates at higher ocean temperatures. Since water vapor is an important greenhouse gas, a large part of it remaining in the Earth’s atmosphere leads to higher surface temperatures. Higher temperatures lead to more evaporation of the oceans, setting the stage for the greenhouse cycle. Finally, we will witness the escape of a large part of the earth’s waters into the atmosphere.
Without water to lubricate tectonic activity, tectonic plates stop moving. Without tectonic activity to pull carbon out of Earth’s atmosphere, the planet’s air density would increase dramatically. As a result, in a few hundred million years, we will become Venus, the twin planet of Earth, which experienced the same fate billions of years ago; Two dead worlds in the hands of their parent star.
By shifting the earth’s orbit, it can be saved from the sun.
Change the position of the planet
The habitable zone is the region around a star where the temperature is suitable for the flow of liquid water on the surface of a planet. Temperatures near the star are too high to prevent any atmospheric complexity so that water exists only as vapor. Outside this range, the temperature is very low.
Earth is now roughly in the middle of the Sun’s life belt, Venus is on the inner edge, and Mars is almost outside. As the age of the sun increases and its brightness increases, the life belt will reach more distant parts of the solar system; So if we want the Earth to survive this process, we have to move it.
Moving a planet will not be an easy task; But fortunately, we are dealing with vast astronomical time scales and we don’t need to move the earth today. In fact, we have hundreds of millions of years to plan this transition. To do this, we can use the same stabilizing force that keeps the planets in orbit around the sun, and that force is nothing but gravity.
The first thing we need to do is find an energy source. Raising the earth’s orbit requires a lot of energy, and this energy has to be supplied from somewhere. Fortunately, we can use the planet Jupiter. Since this gaseous world is 318 times heavier than Earth, its simple movement through the sky provides a surprising amount of kinetic energy, and a small amount can be borrowed.
We are almost 500 million years away from the destruction of the earth by the sun
Jupiter’s energy can be transferred to Earth through orbital interactions. To better understand this issue, suppose you are standing inside a wheeled platform on a railway track and a train is moving towards you. You can’t step out of the way of a train (because then the analogy wouldn’t be fun); So your only chance to survive is to move at least as fast as the train. Of course, if you simply let the train hit the counter, then your speed will match the speed of the train, but not in the way you’d expect.
Instead, you can reach into your pocket and pull out a bouncing meatball. Suppose, this ball is durable and indestructible. You throw the ball at the train. The ball hits the train and bounces back. Then you grab it and move forward a bit. With just a little practice, and through simple conservation of momentum, you’ll find that you can steal some of the train’s energy and give it to yourself and the rolling platform. The train barely notices these collisions, but you do. If you get enough power you can move on without facing disaster.
Now let’s return to the example of Earth and Jupiter. The above analogy is suitable for preventing Jupiter from colliding with our planet, except we use asteroids instead of bouncing balls. We can send asteroids on long orbits around Jupiter. In this scenario, the gravitational interaction between the planet Jupiter and the asteroid leads to an increase in the speed of the asteroid and, in turn, a slight decrease in the speed of the giant Jupiter. Then we can bring the asteroid back to Earth, rotate it in the opposite direction, and achieve the desired force by slowing down its motion.
Running the above process once doesn’t have much effect; So we have to repeat it for hundreds of millions of years so that the Earth can reach higher orbits and thus escape from the wrath of the sun. If our descendants can control this process, they can move the Earth into a safe zone of the habitable zone.
The Sun loses mass through the solar wind or particle stream.
Star setting
If you are not interested in changing the arrangement of the planets, but have the ability for super-engineering projects, we have another solution for you. The main problem with the sun is that helium is a natural product of our star’s fusion process. The hydrogen fusion ratio is defined based on the total mass of the Sun; The bigger a star is, the faster it burns, and in the same way, smaller stars burn at a slower rate; Therefore, if we want to limit the amount of helium production, we must slow down the fusion reactions. The easiest way is to reduce the total mass of the Sun.
Fortunately, the sun is naturally decelerating, but not fast enough. The surface of the Sun continuously emits an endless stream of tiny charged particles, which we call the solar wind. In terms of human-scale statistics, the amount of mass that the Sun loses through the solar wind is 1 to 2 million tons per second, which is an incredibly high rate; But this speed should be increased a little.
The Sun loses one to two million tons of mass every second through the solar wind
One way to speed up the mass loss of the Sun is to heat its surface with lasers or special rays, strong magnetic fields, or whatever mechanism our descendants choose. Heating the surface of the sun leads to an increase in the production of solar winds, and thus the speed of the sun’s mass loss increases; But high-energy particles that are released at high speed are not suitable for habitability on Earth, so they must be transported to a safe place.
One way to control the solar wind is to build a series of particle accelerator stations in orbit around the Sun’s equator. These stations continuously exchange charged particles and create a loop of current in the shape of the solar belt. This current loop creates a torus (donut-shaped) magnetic field that can transform the solar wind into polar outflows in the direction of the sun’s rotation axis and safely remove harmful particles from our planet.
The torus magnetic field can be used to compress the star. According to this method, first, the stations are turned off and thus the particles fall into the sun. Then, by turning on the stations, the magnetic field is interrupted and the falling process is reversed. The magnetic field surrounding the sun’s equator is compressed, forcing particles to be repelled from the sun’s poles.
If our descendants are advanced, they can capture the elusive solar wind and use it for other purposes, such as fusion reactor systems to power an entire facility, and if they are creative, they can direct the outflow of the solar wind in one direction and use it as a booster rocket. use solar to guide the solar system to new points in the Milky Way or even outside the galaxy.
Of course, the technique of moving the star reduces the brightness of the sun; Because despite the lower mass, the fusion reactions take place in a quieter atmosphere, which reduces the power and dimensions of our star. In this way, the life belt moves to an inner part. We may not realize this at first, because the things we do are in opposition to the natural tendency of the life belt to move outward; But eventually, after the Sun has lost 10-20% of its mass, we have to move the Earth to the inner part of the life belt to keep it in the right spot.
In the end, we are left with a smaller, long-lived star. The smallest red dwarfs with a mass of a little more than one-tenth of the Sun can live for trillions of years; But at the same time, it has a more chaotic nature, because due to their low mass, they are subject to stellar explosions that periodically double their brightness. If our descendants want to take this path to increase the life of the sun, they must definitely prevent these explosions.
All in all, if humanity can survive for billions of years, it will probably become an interplanetary or interstellar entity. In this situation, there will be no need to save the land. Perhaps our distant descendants can preserve the land from which they sprang as a mark of respect. Perhaps this is necessary because no other world is as suitable for life as Earth. Ultimately, perhaps, it is an art project, an opportunity to create beauty and wonder on an interplanetary scale, before the fires of nuclear fusion die out and our star breathes its last. The last chapter of the story ends the billions of years of life of the solar system.
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