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Parker Probe; Touching the sun with the world’s fastest spacecraf

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Parker Probe
Studying the Sun up close and trying to uncover its secrets has been a long-held dream that has now become a reality thanks to the Parker Solar Probe.

Parker Probe; Touching the sun with the world’s fastest spacecraft

The sun has supported life on planet Earth for billions of years and has helped shape belief systems and legends throughout human history. This most luminous body in the sky is unavoidable and its existence is undeniable except in the rarest terrestrial environments. However, we still don’t really know how the sun works. Here we will talk about the Parker Probe.

The star of our system is much more complicated than it seems. Instead of the fixed and unchanging disk that our eyes see, the Sun is a dynamic and magnetically active star. The Sun’s atmosphere continuously ejects magnetized material that sweeps across the entire Solar System far beyond the orbit of Pluto, affecting all existing worlds along the way.

The long-standing dream of meeting the sun

Astronomers have studied the Sun for over a century. Using ground and space telescopes that are designed to withstand the impressive radiation of the sun’s burning face, they have stared at this star at every wavelength of the electromagnetic spectrum; But no matter how hard scientists have tried, they have not been able to reveal the secrets of the sun. Perhaps this failure is because until recently no telescope had come close enough to the Sun to really study it.

However, the situation changed recently. In the fall of 2021, for the first time in human history, a spacecraft flew into the Sun’s atmosphere and passed through the super-hot particles of the Sun’s corona. This achievement provided scientists with important information, with the help of which we can finally discover the secrets of the closest star to Earth. This daring spacecraft is called Parker Solar Probe.

Parker probe over the sun
Artist’s impression of the Parker probe’s entry into the Sun’s atmosphere.

The spacecraft was named Parker Solar Probe in honor of Eugene Parker, a famous American astrophysicist

For more than 60 years, scientists have dreamed of flying a spacecraft like the Parker Probe. In 1958, the year NASA was founded, the Space Studies Board of the National Academy of Sciences proposed that this newly established organization send a spacecraft into the orbit of the planet Mercury in order to study the environment around the Sun. Over the years, several research groups have presented different ideas for launching a solar probe; But none of the missions could get as close to the Sun as astronomers wanted. It took decades for the technology of heat shields and other elements to come together well and make the long-held dream of scientists a reality.

The original Solar Probe design in the 1990s intended to use Jupiter’s gravitational pull and enter a polar orbit that would send the spacecraft almost directly toward the Sun; But due to problems including the high cost and time of the mission, the plan was changed in the following years. In the early 2010s, the Sun exploration project was transformed into a less expensive project called Solar Probe Plus, and it was decided to use the gravitational assistance of Venus and a more direct flight path to reach the Sun. In May 2017, the spacecraft was renamed Parker Solar Probe in honor of Eugene Parker, a prominent American astrophysicist and the inventor of the term ” solar wind “. This was the first time that NASA put the name of a living person on one of its spacecraft. Finally, after decades of waiting for scientists, the Khurshid spacecraft was launched on August 12, 2018 (21 August 2018) and began its 7-year mission.

The mysterious star

The Sun’s atmosphere is made up of different layers just like the atmosphere of our planet. The Earth’s atmosphere has three layers, the troposphere, stratosphere, and mesosphere respectively, and the layers of the Sun’s atmosphere are the photosphere, chromosphere, and corona (sun’s crown). The surface of the Sun is often thought to be hotter than other parts, But the photosphere or the surface of the sun is actually not that hot. The temperature in this layer ranges from nearly 6200 degrees Celsius in the lower part to 3700 degrees Celsius in the upper part. This temperature is almost equal to the heat of electric arc welding. It is interesting to know that the air around a lightning strike can be up to five times hotter than the photosphere.

The strange thing is that the corona, as the outermost layer of the Sun’s atmosphere, is much hotter than the photosphere. The temperature of the corona, which starts approximately 2,100 km above the surface of the sun, reaches half a million to several million degrees Celsius, or at least 80 times the surface temperature. It’s like moving away from a fire, and the further you move away from it, the hotter you get. This unusual feature is what makes the achievement of the Parker Solar Probe even more impressive.

Parker Solar Probe
Parker solar probe in clean room. The heat shield of the spacecraft with its white ceramic coating can be seen at the top.

Why the Sun’s corona is much hotter than the Sun’s surface is one of the unsolved mysteries of the universe, and it is the task of the Parker Solar Probe to unravel it. As a result, the probe has the task of collecting information from the magnetic fields and charged particles of the solar corona and trying to answer this puzzle.

Overall, the scientific goals of the Parker probe are to determine the mechanisms that generate the fast and slow solar winds, the heating of the sun’s corona, and the transport of energetic particles. In order to achieve these goals, the probe must approach the Sun less than 10 solar radii from the center of the Sun (the radius of the Sun is 695,500 km) and spend at least 14 hours below 10 solar radii and at least 950 hours below 20 solar radii to make in situ measurements. spend Flying around the Sun, compared to other space missions whose destination is a planet, asteroid, or comet, presents unprecedented technical challenges to the spacecraft, which we will mention below.

Technical challenges of the Parker probe

Parker probe travels faster than any other spacecraft; So that in its last trip around the sun, it will fly over its surface at an incredible speed of 690,000 kilometers per hour. This speed is so high that the distance between Tehran and Kermanshah can be covered in less than three seconds. However, the first big problem facing Parker was actually getting to the sun. Although the sun’s gravity acts as an anchor for the entire solar system, it is not easy to approach.

To get a satellite out of orbit around the Earth, we need to reduce its angular momentum so that it falls towards the planet. This is what we have to do when trying to remove an object from orbit around the Sun; With the difference that in this case, we are at a distance of one astronomical unit or 150 million kilometers from the sun and we are moving at a speed of 30 kilometers per second.

Parker’s first big problem was getting to the sun

Any object that is launched from the earth will enter the path around the sun with the same orbital speed; This means that in order to achieve a shorter orbit around the sun, we must reduce the orbital speed of the spacecraft around the sun. Decelerating the spacecraft is an extremely energy-consuming operation; Especially when you add in the energy required to escape Earth’s gravity. So let’s assume that we first want to get our satellite from the surface of the earth to the orbit around the earth. This requires moving the satellite up to a speed of 9.2 km/s relative to the earth’s surface. Then, the satellite is placed in orbit around the Earth and moves around the Sun at a speed of 30 km/s.

After placing the satellite in the earth’s orbit, we have to perform an orbital maneuver called “Hohmann transfer”. By performing this maneuver, we change the spacecraft’s orbital energy to correct its perigee (closest distance to the Sun) or apogee (farthest distance from the Sun). To meet an outer planet like Mars, we need to increase the solar apogee by adding to the orbital energy of the spacecraft; While reaching an inner planet like Venus requires reducing the solar perigee by reducing the orbital energy. To reach Mars and Venus from Earth’s orbit, we need a delta way (change in velocity) of approximately 2.9 km/s and 2.5 km/s respectively. These values ​​are obtained using the following equation:

Delta V calculation formula

In the equation, the Greek letter mo, similar to the English u, is called the Sun’s planetary parameter, which is the product of the Sun’s mass. R 1 is the orbital radius of the mass from which we start moving. In this case, the distance of 150 million kilometers from the Earth to the sun is considered the orbital radius, and finally, R 2 is the perigee or zenith. If we calculate the DeltaV required for the Parker Solar Probe to reach its closest distance to the Sun (6.2 million km), we will arrive at a number of 21.4 km/s, which is more than 8.5 times the DeltaV needed to reach Venus.

The obtained Delta V number is considered extremely high and exceeds the capability of all rockets built so far. But four years ago, the Parker Solar Probe launched from Cape Canaveral, Florida atop the Delta 4 Heavy, the world’s second most powerful rocket after SpaceX’s Falcon Heavy. In order to give the probe additional thrust, Delta 4 was equipped with a special solid-fuel third stage, which provided an additional three kilometers per second delta velocity for the normally two-stage rocket.

However, even with this extra power, the probe could never get close to the Sun. In order to make his record-breaking flight, which was one-seventh of the record of Helios 2, NASA’s previous solar probe, Parker was assisted by the gravity of the planet Venus in an amazing way five times, and he is going to make two more flybys of this planet in 2023 and 2024.

The path of the Parker probe. The spacecraft shortens its orbit around the Sun with each Venus flyby.

Since Venus is a relatively low-mass planet, Parker needed this number of flybys. The amount of speed a planet can change is largely determined by its gravity, which in turn is determined by the planet’s mass. As mentioned earlier, Parker’s original plan was to get a gravitational boost from Jupiter that would bring the probe three times closer to the Sun; But this path was accompanied by some problems.

Since Jupiter’s orbit is very far from the Sun, the sunlight reaching the solar panels at the peak of Parker’s orbit was reduced by 25 times, and therefore the spacecraft needed much larger panels to provide its energy. This became problematic as the spacecraft orbited Jupiter and began accelerating toward the Sun. In this situation, the panels would be destroyed by the sun’s heat and could not be folded and hidden behind the solar shield.

Other options were available. The Parker builders could have used a radioisotope thermal generator; But this would dramatically increase the cost, weight, and complexity of the spacecraft. The real strength of Parker’s new and different flight path is getting more time and data to help scientists meet the rover’s mission goal of studying the Sun.

With the original plan to fly around Jupiter, the probe had only 100 hours of time in the target region around the Sun, and could only fly past the Sun twice before reaching the end of its eight-year mission. The new shorter path means that Parker Solar Probe will take less than 150 days to complete an orbit around the Sun, allowing scientists to collect more than 900 hours of data during the probe’s 24 orbits.

The main instruments of the spacecraft

Heat Shield

The change in the program was accompanied by a change in design, abandoning the original cone-shaped heat shield and using the flat, compact, and familiar shield used in other spacecraft. This shield is made of carbon foam with a thickness of 11.4 cm; A truly amazing material that is the product of one of the most capable material innovation labs called Ultramet. Under the scanning electron microscope, this carbon foam appears to be an extremely porous material with 97% of its internal volume being empty space, thus providing amazing insulation properties for the heat shield while benefiting from the thermal stability of carbon.

Parker’s heat shield is made of carbon-carbon composite and is exposed to temperatures of approximately 1400 degrees Celsius.

The next material is carbon-carbon composite, which is made by combining graphite with an organic binder such as bitumen or epoxy resin. This compound was applied to each side of the foam before being superheated and converting the glue into a pure form of carbon, creating a carbon-carbon composite. Finally, ceramic white was used to paint the sun-facing side of the shield to reflect the heat more.

But if the temperature of the Sun’s corona is at least half a million degrees Celsius, how can the probe enter it without melting? Although the Sun’s outermost layer is incredibly hot, it has a very low density. As a comparison, think of the difference between putting your hand in the oven and a pot of boiling water. (Don’t do this at home!) Hands can withstand much higher temperatures in the oven for longer than boiling water; Because they have to face many more particles in the pot of water.

Similarly, the Sun’s corona is less dense than the visible surface of the Sun; As a result, the spacecraft encounters less hot particles. In fact, while Parker is moving in an environment with a temperature of several million degrees Celsius, the heat shield facing the sun of the spacecraft only heats up to approximately 1400 degrees Celsius.

Read More: The Voyager Twins

Solar Probe Cup (SPC)

Other parts of the spacecraft, plus some specialized sensors and solar panels, had to be designed to fit under the shield’s shadow. But there are various tools that bravely step out from under the shadow of the heat shield; Like the cup of the solar probe, which is one of several sensors on board the spacecraft. This piece is undoubtedly Parker’s most impressive piece of technology, completely outside the scope of the sun shield’s protection; As a result, designers had to be very creative in using materials.

The Parker Solar Probe cup is a Faraday cup and part of the Solar Wind Survey Instrument (SWEAP); A device that can count and measure the properties of electrons and ions radiated from the sun and actually gives the spacecraft the ability to study the solar wind and objects ejected from the sun’s crown. This device basically works by applying an electric field to the grid placed in the mouth of the cup. By changing the voltage, it is possible to select or filter the particles that are able to enter the cup, and at the same time as the charged particles hit the collector plate at the bottom of the cup, more information can be obtained about the cause of the current. In practice, the cup is a very simple device; But facing temperatures of 1,400 degrees Celsius, which is just below the melting point of pure iron, the solar probe cup required some engineering innovations.

Solar Probe Cup (SPC)
Solar Probe Cup (SPC).

The first challenge was to choose a material for the electric grid that would create a selective electric field at the entrance of the cup. In addition to conductivity and resistance to heat, this network must also be machinable to make a spaced network on the scale of one hundred microns. For this purpose, the makers used tungsten; The same material used here on Earth in incandescent light bulbs. Thanks to tungsten, the lamps can survive the very high temperatures required to produce light. Tungsten filaments operate at a temperature of three thousand degrees Celsius; As a result, they are very durable against extreme temperatures. However, machining tungsten in a very fine mesh is difficult.

Micron-scale machining is not possible with traditional tools. By using these tools, as soon as the necessary force is applied to shave the metal, the mesh breaks. Instead, in such cases, lasers are usually used for engraving on materials; But since tungsten is very resistant to heat, the laser will not be able to melt it to form a network. Instead, the makers used acid printing.

Next, cables were needed that could supply the main power and carry the electrical signals away from the collector plate. Copper and aluminum, two common conductors on Earth, will be transformed into a pool of molten metal at the Parker Solar Probe position; As a result, they could not be used in any way. Each conductive cable in this part of the spacecraft must be made of niobium C-103, a special alloy consisting of 89 percent niobium, 10 percent hafnium, and 1 percent titanium. This strange aerospace material has also been used in the construction of all the components of the outer cover. Normally the wires are insulated with plastic outer coverings, But obviously, this option was not possible for the Parker space probe and the engineers had to use sapphire to ensure the insulation of the niobium wires.

To accomplish what is a relatively mundane task on Earth, Parker’s builders were forced to use strange materials. Other parts of the sensors beyond the solar shield are constructed in a similar manner. Magnetic field measuring instruments hidden behind the shield require antennas that extend beyond the solar shield to make measurements of the Sun’s magnetic field. These four antennas are also made of Niobium C-103.

Solar Panels

Solar panels were the next challenge. While orbiting the sun in its distant orbit, the spacecraft can fully open its solar panels without any problems; But as the probe begins its rapid return to the Sun, heat will become an increasing problem. By collecting solar panels, this problem can be partially dealt with; But the spacecraft must maintain some power to launch its scientific equipment during this important phase of the flight.

Parker has two smaller secondary panels that face the sun and are water cooled. This water is inside the solar panels and black radiators that are like titanium trusses right under the solar shield. It is pumped. This truss is very light despite its large size. The whole truss weighs only 22.7 kg, which considering the size of the structure, is very low weight even for titanium as a metal with low density. By performing detailed stress calculations, NASA engineers have ensured that the truss can use as little material as possible. This, of course, saves the launch weight; But the materials available to transfer heat from the heat shield to the bus (main body) of the spacecraft have also been minimized.

Edilo solar furnace
Edilo solar furnace in France.

It is difficult to test systems on the ground in the heat they are expected to encounter. The Edilo Solar Furnace is the most similar location to the environment that the Parker Probe systems will have to endure. Built on a mountainside in southern France, the facility uses ten thousand adjustable mirrors to focus light onto a concave mirror. Edilo solar furnace has the ability to reach a temperature of 3500 degrees Celsius; More than twice the temperature that Parker’s solar shield will experience.

Parts such as the Faraday cup and the solar shield were placed at the focal point of the concave mirror of the furnace and exposed to the temperatures that they must withstand when exposed to the sun. However, a piece like Faraday’s cup had to be tested while performing its sensory functions. To that end, the engineers needed a particle accelerator to simulate the electrons and ions from the solar wind that the cup would encounter. It was not possible to combine the particle accelerator with the solar furnace; As a result, researchers from the University of Michigan proposed the smart idea of ​​using four high-power IMAX projectors to simulate the sun’s heat. They also found that the Faraday cup actually performed better when heated; Because heat cleans the system from pollutants.

Much of the information obtained from the Faraday Cup is of little interest to the casual space enthusiast. They are the raw data that provide scientists with valuable clues about the nature of the Sun. However, one of the sensors on the spacecraft, which is in charge of transmitting images to the ground, can surprise us.

Wide Field Camera for Solar Probe (WISPR)

During a solar eclipse, we can observe a beautiful phenomenon: bright rings of light that appear around the sun. These extraordinary patterns are the result of bright electrons that move around the Sun on magnetic field lines and have been deformed by the pressure of the solar wind. We have been able to observe streams of energetic electrons from our Earth and solar observatories located at Lagrangian point 1, But we never managed to see them up close until recently.

After completing its final orbit and completing its mission, Parker will evaporate into the Sun’s atmosphere

As the Parker Solar Probe entered the corona on its ninth encounter with the Sun, it began capturing images of the surrounding space with its Wide Field Imager (WISPR), an array of optical telescopes. The images sent back to Earth are like a traveler’s view of a blizzard passing through on a dark night: glowing sub-particles streaming past as the probe plunges into the eye of the storm. These beautiful images will undoubtedly provide scientists with unique data about the nature of the sub-particles flowing in the Sun’s corona.

The path ahead of the Parker probe

The next close encounter of the Parker Solar Probe will take place on June 11, 1401, and the spacecraft will circle the Sun another 15 times for a total of 24 times in the next three years. With two more flybys of Venus in 2024 and 2025, Parker will break his records and get much closer to the Sun. On the last visit, the probe will reach a distance of 16.6 million kilometers from the Sun, which is almost seven times closer than any other spacecraft.

After completing the 24th orbit, the probe may have some fuel to continue orbiting the Sun; But Parker ultimately fails to ignite the thrusters necessary to keep his heat shield facing the Sun. The probe will then begin to rotate, and parts of the spacecraft not designed to see the sun will be exposed to full radiation.

The spacecraft will first break into large pieces and then become smaller and smaller. In the end, the entire probe, which is about the size of a small car, will be left with nothing more than tiny dust scattered across the Sun’s corona. However, Parker’s legacy will live on. The probe’s observations are expected to finally help solve questions that have been puzzling scientists for decades.

Space

Black holes may be the source of mysterious dark energy

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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

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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

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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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Space

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

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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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