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The Voyager Twins

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The Voyager Twins
The Voyager 2 twins, the pioneering probes launched 45 years ago to visit the four giant planets of the solar system, are still operating, although some instruments have been turned off.

The Voyager Twins; Explorers of the skies to infinity

The Voyager Twins; Explorers of the skies to infinity. If the lucky stars hadn’t aligned, two of the most amazing spacecraft ever launched wouldn’t have taken off from Earth. In this case, the lucky stars were actually the planets, or more precisely, the four major planets of the solar system. Almost 60 years ago, these four planets were slowly moving to a special position in the early years of the 19th century. For a while, this rare planetary alignment was largely ignored. The first person to notice this was an aeronautical doctoral student at the California Institute of Technology (Caltech) named Gary Flandreau.

The story goes back to 1965 and the early years of the era of space exploration; When the Soviet Union launched the world’s first satellite named Sputnik 1 just eight years ago. Working part-time at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, Flandreau was tasked with finding the most efficient way to send a space probe to Jupiter, or perhaps even Saturn, Uranus, or Neptune. Using a precision tool favored by 20th-century engineers, the pencil, he mapped the orbits of those giant planets and discovered an interesting fact: in the late 1970s and early 1980s, all four giants of the solar system were like pearls on a celestial necklace in an arc. They will line up with the ground.

This planetary alignment meant that a spacecraft could accelerate due to the gravitational pull of any passing giant planet; It is pulled as if by an invisible string that snaps at the last second and throws the probe on its way. Flandreau calculated that these repeated gravitational contributions would reduce the transit time between Earth and Neptune from 30 to 12 years. There was just one problem: planetary alignments only happen once every 176 years. The spacecraft would have to be launched by the mid-1970s to reach the planets while the lineup still stands.

Voyager 2 under test at NASA's Jet Propulsion and Launch Laboratory

Voyager 2 is being tested at NASA’s Jet Propulsion Laboratory before flight (left). The spacecraft was launched on August 20, 1977 (right).

As we know, NASA built two spacecraft to take advantage of this unique opportunity. Voyager 1 and Voyager 2, which are identical, were launched 15 days apart in the summer of 1977. After nearly 45 years in space, they are still working, sending data back to Earth daily from beyond the farthest known planets in the solar system. Voyagers have traveled and survived longer than any other spacecraft in history, reaching into interstellar space with an eye toward our understanding of the boundary between the Sun’s realm and the rest of the galaxy. Considering that the Voyager missions were originally supposed to last only four years, this long period of activity is an amazing record.

A rare alignment of the solar system’s giants provided a once-in-a-lifetime opportunity to visit them all in one mission.

Early in their journey four decades ago, Voyagers showed amazed researchers the first close-up views of the moons of Jupiter and Saturn, revealing the existence of active volcanoes and fissured ice fields on worlds that astronomers thought were lifeless and crater-filled like our own. They are collisions. In 1986, Voyager 2 became the first spacecraft to pass by Uranus. The spacecraft visited Neptune three years later and is the only probe to date to have made such trips. Now, as pioneering interstellar probes more than 19 billion kilometers from Earth, the Voyagers are simultaneously delighting and confounding theorists with a series of unexpected discoveries about that uncharted region.

The long adventure of the Voyagers explorers is finally coming to an end. For the past three years, NASA has turned off heaters and other non-essential components and stored the spacecraft’s remaining fuel to extend their unprecedented journey until around 2030. For scientists, many of whom have worked on Voyager’s mission since its inception, the end of the spacecraft’s career is a bittersweet time. They are now facing the end of a project that far exceeded their expectations.

“We’re at 44 and a half years [of the mission],” says Ralph McNutt, a physicist at Johns Hopkins University’s Applied Physics Laboratory who has devoted much of his life to Voyagers; As a result, we have lasted 10 times the guaranteed period.”

Read More: James Webb telescope’s deep look at the first days of the world

Big Tour

The stars of fortune may have helped, but at first, Congress did not cooperate. After Flandreau’s report, NASA drew up plans for a mission called the “Grand Tour” that would send four probes to the four giant planets and Pluto. But such a project was ambitious and expensive, and for that reason, Congress rejected it. “There was this really big prospect, and it got scaled back because of the cost,” says Linda Spilker, a planetary scientist at the Jet Propulsion Laboratory who began working on the Voyagers in 1977, months before they launched.

Congress eventually approved a scaled-down version of the Grand Tour, originally called Mariner Jupiter Saturn 1977 (MJS 77). In the new program, two spacecraft will be sent to only two planets. However, NASA engineers moved in relative secrecy to design spacecraft capable of withstanding the rigors of much longer missions. They hoped that once the twin probes proved themselves, their plans would extend to Uranus, Neptune, and beyond.

“Four years was the length of the original mission,” says Susan Dodd, who returned to the Voyager team in 2010 as project manager after a 20-year hiatus. “But if the project engineer could choose a 10 percent more expensive part that was not needed for the four-year mission, he would do it and not necessarily inform management.” He added that the fact that scientists were able to build two spacecraft and both are still working is a far more impressive achievement.

The construction of Voyagers was an entry into completely new territory from an engineering and navigation perspective in deep space. The slogan “failure is not an option” had not yet been invented and was not considered very appropriate at that time. In the early 1960s, NASA attempted to send a series of spacecraft to the moon with the goal of surveying landing sites for future manned missions. After 12 failures, finally one of these attempts was successful.

The construction of Voyagers was an entry into completely new territory from an engineering and navigation perspective in deep space

“In those days we always launched two spacecraft,” says Donald Grant, because the failure rate was so high. Grant, a physicist at the University of Iowa who was one of the lead scientists on the Voyager team and a seasoned member of 40 other space missions, died in January a few weeks after being interviewed for this article. At his obituary, Grant’s daughter Christina said her only regret was that she would not be alive to see the Voyager data in the next 10 years.

When Voyager was built, only one spacecraft had used a gravity assist to reach another planet: the Mariner 10 probe, which took advantage of the gravitational pull of Venus on its way to Mercury.

But the Voyagers had to receive multiple gravity inputs with a margin of error in tens of minutes. Jupiter, their first station, was almost 10 times farther from Earth than Mercury. In addition, the Voyagers had to travel through the asteroid belt along the way. Before Voyagers, McNutt says, it was hotly debated whether a spacecraft could pass through the asteroid belt “without disintegrating.” However, in the early 1970s, when Pioneer 10 and 11 flew safely through the region, it became clear that the asteroid belt consisted mostly of empty space, paving the way for the Voyagers.

Voyager's Golden Disc

Because an alien civilization might intercept the spacecraft, each Voyager carries a golden disk (left) of terrestrial sounds and images. Engineers install Voyager 1’s disk cap before launch (right).

To deal with all these challenges, the Voyagers, which are each about the size of an old Volksfrog, had to benefit from some degree of internal intelligence. As a result, NASA engineers equipped space computers with 69 kilobytes of memory, which is less than one hundred thousandths of the capacity of ordinary smartphones. In fact, the comparison with smartphones is not very fair. “Voyager’s computers have less memory than the key that opens your car door,” says Spilker. All data collected by the spacecraft’s instruments are stored on 8-track recorders and then transmitted to Earth by a 23-watt transmitter (about the same power as a refrigerator light bulb). To compensate for the weak transmitter, both Voyager spacecraft carry dish antennas approximately 3.5 meters in diameter to send and receive signals.

“At the time, it felt like we were at the cutting edge of technology,” says Alan Cummings, a physicist at the Cal Institute of Technology and another veteran Voyager scientist. The amazing thing was how quickly it all happened. Over the course of four years, the MJS 77 team built three spacecraft, including a full-scale, functional prototype. The original spacecraft were renamed Voyager 1 and Voyager 2 a few months before launch.

Although many scientists have worked on Voyager over the decades, Cummings can make a unique claim. “I was the last person to touch the spacecraft before launch,” he says. Cummings was responsible for building two detectors designed to measure the flux of electrons and other charged particles as the Voyagers encounter the giant planets. Particles pass through a small window in each detector, which is made of aluminum foil only three microns thick. Cummings was concerned that technicians working on the spacecraft might have accidentally damaged the windows. “As a result, they had to be revised just before launch,” he says. In fact, I noticed that one of the windows was a little loose.”

Meeting the giants of the solar system

Voyager A reached Jupiter in March 1979, 549 days after launch. Following a different route, Voyager 2 arrived at the first station in July of the same year. Both spacecraft were designed to be fixed platforms for their vidicon cameras; A type of photography tool that uses red, green, and blue filters to produce full-color images. These cameras hardly rotate while moving very fast in space to minimize the risk of blurring. In fact, their rotational motion is more than 15 times slower than the crawling of a clock hand. Still, about three or four months away from reaching Jupiter, the spacecraft began sending the first images of the planet back to Earth, watched by a standing crowd at the Jet Propulsion Laboratory.

” They had monitors installed in all the main conference rooms and in the hallways,” says Spilker. As a result, as the data arrived line by line, each image appeared on one monitor. “It was immensely exciting to see the way and the growing anticipation of what we were going to see when we actually got close to it.”

Voyagers discovered an exciting variety of lunar landscapes around Jupiter and Saturn

Cummings vividly remembers the day he laid eyes on Io, Jupiter’s third-largest moon, for the first time. “I was walking into a building on the Caltech campus; Where they were showing the live feed [of Voyager images]. I entered the building and saw a large orange and black picture of Ayo. “I thought the Caltech students were playing a joke and this picture was of poor-quality pizza.” Ayo’s colorful appearance was completely unexpected. Before Voyager captured the image of Io, it was assumed that all the moons of the solar system were more or less the same, uniform, and cratered. No one expected the Voyagers to discover such an exciting variety of lunar landscapes around Jupiter and Saturn.

The first clue that the moons in the sky might be more diverse than astronomers thought came when Voyager was still about 1.5 million kilometers from Jupiter. One of the spacecraft’s instruments, the Low Energy Charged Particle (LECP) detector system, picked up unusual signals. “We saw oxygen and sulfur ions hit the detector,” said Stamatios Krimigis, designer of the LECP and former director of the Space Unit at Johns Hopkins University’s Applied Physics Laboratory. “The concentrations of oxygen and sulfur ions had increased a thousandfold compared to the levels measured up to that point.” At first, his team thought the instrument had malfunctioned. “We crunched the data,” Krimigis said. But there was no problem.”

Voyager’s cameras soon solved the mystery: Io had active volcanoes. This tiny world, slightly larger than Earth’s moon, is now known to be the most volcanically active mass in the solar system. Edward Stone, who has been a project scientist on the Voyager missions since 1972, says: “The only active volcanoes we knew about at the time were on Earth, and suddenly we saw a moon that was 10 times more volcanically active than Earth.” The colors of Io and the unusual ions that hit the Krimigis detector came from elements blasted from the moon’s volcanoes. The largest Ayu volcano, known as Pele, has erupted 30 times the height of Mount Everest and its remains have covered an area almost the size of France.

Voyager images of the giant planets of the solar system

The Voyager 2 twins made detailed visits to the giant planets of the Solar System, and by flying past Jupiter (1 and 2) and Saturn (5 and 6), they captured the first close-up views of those planets’ moons. For example, it turned out that Europa, Jupiter’s moon (3) is covered in ice and Io (4) is full of volcanoes. These discoveries came as a surprise to scientists who thought that the moons of other planets, like Earth’s moon, were gray worlds full of craters. Voyager 2 then passed by Uranus (7) and Neptune (8), becoming the only probe to ever visit these two ice giants.

In total, the Voyagers took more than 33,000 pictures of Jupiter and its moons. Each image seemed to bring a new discovery: Jupiter has rings, and Europa, one of Jupiter’s 53 named moons, is covered in a cracked icy crust now estimated to be more than 60 miles (95 kilometers) thick. As the spacecraft left the Jupiter system, they accelerated by approximately 16 km/s as they received a gravitational boost. Without this help, they could not overcome the gravitational pull of the Sun and reach interstellar space.

After visiting Saturn, Voyager 1 left the solar system and Voyager 2 traveled alone to Uranus and Neptune.

At Saturn, Voyagers separated. Voyager 1 flew through Saturn’s rings and hit thousands of dust grains, headed for Titan, a moon shrouded in orange smoke, and then headed north of the planet’s surface. Voyager 2 continued its journey alone to Uranus and Neptune. In 1986, Voyager 2 discovered ten new moons around Uranus, adding the planet to the growing list of ringed worlds. However, just four days after Voyager 2’s closest approach to Uranus, its discoveries were overshadowed by the explosion of the space shuttle Challenger. The spacecraft exploded shortly after launch, killing all seven crew members, including Christa McAuliffe, a high school teacher from New Hampshire who was to become the first civilian astronaut.

Three years later, Voyager 2 passed 4,800 km above Neptune’s methane-rich azure atmosphere, measuring the highest wind speed of any planet in the Solar System: up to 1,600 km/h. It turns out that Triton, Neptune’s largest moon, is one of the coldest places in the solar system with a surface temperature of minus 235 degrees Celsius. The glaciers on this moon threw nitrogen gas and powder particles up to a height of 8 km into the atmosphere.

Voyager 2’s images of Neptune and its moons might have been the last images taken by Voyager 2 had it not been for renowned astronomer Carl Sagan, a member of the mission’s imaging team. With the Grand Tour officially over, NASA decided to turn off the cameras on both probes. Although the mission was extended with the hope that the Voyagers would reach interstellar space (the program was officially renamed the Voyager Interstellar Mission), after Neptune there would be no targets to photograph, only the boundless void of space and very distant stars.

Jupiter's moon Io

The discovery of the Pele volcano, shown in this image from Voyager 1, confirmed that Jupiter’s moon Io is host to volcanic activity.

Siegen asked NASA officials to send Voyager 1 its last set of images back to Earth. Consequently, on Valentine’s Day 1990, the probe aimed its cameras at the inner solar system and captured the final 60 images. The most impressive photo of them all, called the “Pale Blue Dot” by Cygne, captured the Earth from a distance of more than 6 billion kilometers. This photo is still considered the most distant portrait ever recorded of our planet. The ground cover is barely visible in the light reflected from the camera optics and does not even occupy a full pixel.

Spilker says Cygne, who died in 1996, worked hard to convince NASA that it was worth looking at ourselves and seeing how small the pale blue dot was.

Leaving the Sun’s Realm

Both Voyagers are now so far from Earth that a one-way radio signal traveling at the speed of light takes approximately 22 hours for Voyager 1 and just over 18 hours for Voyager 2. Spaceships move three to four light seconds away from Earth every day. Their only way of communication with Earth is through NASA’s Deep Space Network; An array of antennas around Earth that allow uninterrupted communication with the spacecraft as the planet orbits. As the Voyagers get farther away from us in space and time, their signals get weaker. “Earth is a noisy place,” says Glenn Nagel, director of development and communications at the Far Space Network Facility in Canberra, Australia. Radio, TV, and cell phones all make noise. As a result, it becomes harder and harder to hear the faint chatter of the spacecraft.

As the chatter fades, astronomers’ expectations of what the Voyagers will discover as they enter the interstellar phase of the mission change. Stone and other Voyager scientists caution against confusing the boundary of interstellar space with the boundary of the solar system. The solar system includes the distant Oort cloud; A globular collection of comet-like bodies trapped in the Sun’s gravity and possibly orbiting the nearest star. Voyagers will not reach the inner boundary of this range for at least another 300 years. However, interstellar space is much closer and begins where a phenomenon called the solar wind ends.

Like all stars, the Sun emits a steady stream of charged particles and magnetic fields called the solar wind. This wind, traveling at supersonic speeds, leaves the Sun like an inflating balloon and forms a region of space that astronomers call the heliosphere. As the solar wind blows through space, it pulls the Sun’s magnetic field along with it. Finally, the pressure caused by the interstellar material prevents the expansion of the heliosphere and creates a boundary with the interstellar medium along a huge area called the “exit shock zone”. Before the Voyagers, estimates of the distance to the boundary of the heliosphere, the interstellar space known as the heliopause, varied greatly.

No one was sure exactly when the Voyagers would leave the Sun’s realm

“Frankly, some of those estimates were just guesswork,” Grant says. One early estimate placed the heliopause near Jupiter. Grant’s own calculations, made in 1993, put the distance at between 116 and 177 AU (about 25 times farther) (each AU is equal to the distance between the Earth and the Sun, which is 150 million kilometers). According to him, these numbers were not liked by his colleagues. By 1993, Voyager 1 was 50 AU away from Earth. “If [the heliopause] was at 120 AU, then we had another 70 AU to get to,” Grant says. If Grant was right, the Voyagers would not have exited the heliosphere at a rate of about 3.5 AU per year until at least two decades later.

The prediction raises troubling questions: Will the Voyagers, or Congressional support, last that long? The mission budget was extended with the expectation that the spacecraft would pass the heliopause at a distance of approximately 50 AU. However, the spacecraft passed the milestone without finding any of the expected signatures of the interstellar transition. Astronomers expected Voyagers to detect a sudden burst of galactic cosmic rays. These rays are energetic particles that are fired like shrapnel at the speed of light from supernovae and other catastrophic events in deep space.

Voyager’s ground team also waited for the spacecraft to register a change in the prevailing magnetic field. The interstellar magnetic field, thought to be generated by nearby stars and massive clouds of ionized gas, is likely to have a different direction than the heliosphere’s magnetic field; But the Voyagers had not detected such a change.

The mystery of the heliosphere

Grant’s estimates in 1993 were considered a kind of prophecy. Almost 20 years passed until one of the Voyagers finally reached the heliopause. Meanwhile, the mission barely survived budget threats, and Voyager’s team dwindled from hundreds of scientists and engineers to a few dozen fixed companions. Most of these people are still working today. “When you have such a long-term mission, you start to see your colleagues as family,” says Spilker. We had a baby around the same time and took time off together. “Now we’re spanning several generations, and some of the younger colleagues on [the] Voyager [team] weren’t even born [when the spacecraft] launched.”

The tenacity and commitment of that group of brothers and sisters paid off on August 25, 2012, when Voyager 1 finally crossed the heliopause. However, some of the data sent from the spacecraft was confusing. “We’ve been belatedly announcing that we’ve reached interstellar space,” Cummings says. Because we could not agree on this fact. “For about a year, there were many discussions.”

Although Voyager 1 did indeed find the expected jump in plasma density (the spacecraft’s Plasma Wave Detector, an instrument designed by Grant, inferred an 80-fold increase), there was no sign of a change in the direction of the ambient magnetic field. If the spacecraft had gone from the region under the influence of the Sun’s magnetic field to the region with the magnetic field caused by other stars, wouldn’t this change be observable? “It was shocking and it still haunts me,” Cummings said. But many colleagues have come to terms with it.”

Voyager 2 also failed to detect a change in the magnetic field when it reached the boundary of interstellar space in November 2018, adding another mystery: the spacecraft encountered a heliopause at a distance of 120 AU from Earth; The same distance that Voyager 1 identified as the boundary of the heliosphere 6 years ago. This issue did not agree with any of the theoretical models; Because they all said that the heliosphere should expand and contract simultaneously with the 11-year cycle of the sun, during which the solar wind wanes and rises. Voyager 2 reached the heliopause when the solar wind was peaking, and if the models were correct, they should have pushed the heliopause farther than 120 AU. “This was unexpected for all the theorists,” Krimigis says. “I think the modeling was not accurate enough in terms of what the Voyagers found.”

Now that the Voyagers are giving theorists real field data, their models of the interaction between the heliosphere and the interstellar medium are becoming more sophisticated. “The overall picture is that our Sun emerged from a hot, ionized region and entered an inhomogeneous, partially ionized region of the galaxy,” says Gary Zank, an astrophysicist at the University of Alabama in Huntsville. This hot region was probably formed by a supernova; An event in which some kind of ancient star nearby, or perhaps a few, exploded at the end of their lives, heating up space and stripping electrons from their atoms in the process.

The border around that area can be considered like a seashore with all the water and waves swirling and mixing. We are in that kind of turbulent region where the magnetic fields are changing and flipping. These magnetic fields are not like the uniform examples that theorists usually like to paint; However, the amount of observed turbulence can be different depending on the type of observation. Voyager data show little field variation on large scales: but many small-scale fluctuations around the heliopause are the result of the heliosphere influencing the interstellar medium. It is thought that at some point the spacecraft will leave the turbulent masses behind and eventually encounter the net interstellar magnetic field.

Or maybe the image described is completely wrong. A group of researchers believe that the Voyagers have not yet left the heliosphere. “There is no reason why the magnetic fields in the heliosphere and the interstellar medium should have exactly the same direction,” says Leonard Fisk, a space plasma scientist at the University of Michigan and a former administrator at NASA. For the past few years, Fisk and George Gloeckler, his Michigan colleague and longtime Voyager mission scientist, have been working on a model of the heliosphere that pushes its boundary out another 40 AU.

To understand the heliosphere more deeply, we need to launch a new interstellar probe

However, most people working in this field are convinced that the dramatic increase in galactic cosmic rays and plasma density means that Voyagers will leave the heliosphere. “Given that, it’s hard to argue that we’re not really in interstellar space,” Cummings says. But on the other hand, not everything is right. That’s why we need interstellar exploration.”

McNutt has been working on such a mission for decades. He and his colleagues at Johns Hopkins have just finished drafting a nearly 500-page report outlining plans for interstellar exploration. The probe, which will be launched in 2036, could potentially reach the heliosphere in 15 years, taking 20 years off the Voyager 1 flight. The new interstellar probe, unlike Voyager’s missions, will be specifically designed to study the outer boundary of the heliosphere and its surroundings. Over the next two years, the National Academies of Sciences, Engineering, and Medicine will decide whether this mission should be one of NASA’s priorities for the next decade.

An interstellar probe could answer one of the most fundamental questions about the heliosphere. “If I’m looking in from the outside, what does this structure look like?” McNutt says. We really don’t know. It’s like trying to understand what tight looks like to a goldfish. “We [must] be able to see Teng from the outside.” In some models, when the heliosphere moves at a speed of 724,000 kilometers per hour, interstellar material, like water around the chest of a ship, slowly flows alongside it, forming a comet-like shape. One recent computer model, developed by Merav Ofer and his colleagues at Boston University, predicts that the more turbulent dynamics would give the heliosphere a cosmic croissant-like shape.

Some things are still around even though they no longer serve any particular purpose: answering machines, video recorders, and coins. Using technology from 50 years ago, Voyagers pushed beyond their limits. “The amount of software on these spacecraft is very small,” Krimigis says. “There are no microprocessors involved, because they didn’t exist [half a century ago].” Voyager’s designers couldn’t rely on thousands of lines of code to help turn the spacecraft. “Overall, I think the mission took too long,” Krimigis says. Because almost all functions of spacecraft are fixed and cannot be changed by software. Today’s engineers do not know how to do this. I don’t know if it is possible to build such a simple spacecraft now. “Voyager is the last example of its kind.”

Journey to Infinity

It will not be easy to say goodbye to the pioneering Voyagers. “It’s hard to see it ending,” Cummings says. But we really achieved something amazing. We might never reach the heliopause, But we did it.”

Voyager 1 and Voyager 2 now have 4 and 5 active instruments remaining, respectively. All of them are powered by a device that converts the heat from the nuclear fission of plutonium into electricity. But with power output dwindling to roughly four watts per year, NASA has been forced to prioritize needs. Two years ago, the mission’s engineers turned off the heater of the Cosmic Ray Detector, which was crucial in determining the transition from the heliopause. Everyone expected the death of this tool. “The temperature dropped to about 60 or 70 degrees Celsius, which was well outside the tested operating limits,” says Spilker. [But] the tool continued to work. It was amazing.”

The last two Voyager instruments to shut down will likely be the magnetometer and the plasma science instrument. They are located in the body of the spacecraft, where they are heated by the heat emitted from the computers. Other instruments are suspended on a 13-meter fiberglass arm. “So when you turn off the heaters, those tools get very, very cold,” Dodd says.

But how many more years can Voyagers last? “If all goes well, we might be able to extend the missions into the 2030s,” Spilker says. It depends only on energy, which is the limiting factor.”

The pale blue dot and Carl Sign

This image of Earth from a distance of approximately 6 billion kilometers is considered one of the last images taken by Voyager 1. Voyager scientist Carl Sagan called it the “faint blue dot.”

Even after the Voyagers are completely powered down, their journey will continue. In 16,700 years, Voyager 1 will pass Proxima Centauri, our nearest neighboring star, and 3,600 years later, Voyager 2 will succeed in repeating the same feat. They will then continue to orbit the galaxy for millions of years. Years after our sun has collapsed and the heliosphere and of course, the pale blue spot are gone, the Voyagers will still be roaming out there, more or less intact. They may be able to convey a final message at some point in their journey. This message will not be transmitted through radio waves and if it is received, the recipients will not be human.

Even after the Voyagers are completely powered down, their journey will continue

Voyager’s message is conveyed on a different kind of old technology: two discs, albeit different from the standard plastic version. These discs are made of copper, covered with gold, and protected in an aluminum casing. In the grooves of the golden discs, there are images and sounds that aim to give a sense of the world from which Voyagers came: images of children, dolphins, dancers, and sunsets; The sound of crickets, rain, and a mother kissing her child and 90 minutes of music including Brandenburg Concerto No. 2 by Bach and Johnny B. Good Chuck Berry.

In the discs, the message of greetings of earthlings to aliens is stored in 55 languages ​​of the world, including Farsi. The text of the Farsi message is as follows: “Peace be upon the inhabitants of the beyond the heavens.” Human beings are members of one body, which is one gem in creation. When one member was hurt, the other members were not spared.” Finally, there is a message from the then-President of the United States, Jimmy Carter. It reads in part: “We send this message to the universe. We hope to one day join a community of galactic civilizations by solving the problems we are facing. This disc represents our hope and determination and our goodwill in a limitless and wonderful world.

Space

Black holes may be the source of mysterious dark energy

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

Black holes may be the source of mysterious dark energy

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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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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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