Este ESTRANHO OBJETO está bombardeando a Terra com ANTIMATÉRIA ｜ Astrum Brasil

800 light years away, there is an invisible antimatter factory, producing high-energy positrons. Small antimatter particles that flow through the cosmos and collide with our planet. For much of history, we did not know about the existence of this strange source. Most of the positrons that bomb us went completely unnoticed, we only noticed them when we began to observe beyond the limits of our planet. In 2011, NASA's Alpha Magnetic Spectrometer was turned on, a particle detector of the latest generation, about 320 km in altitude, aboard the International Space Station. What he found? You guessed it, positrons. The presence of these subatomic particles was expected, but not in the amount they were found. The volume of positrons detected was so large that the usual sources, such as natural radioactive decay and cosmic rays, no longer offered a sufficient explanation. So, where did they come from? Only recently, we managed to track the culprit for this cosmic rain of antimatter, and it all comes down to another high-energy discovery. A strange cloud of gamma rays called Gemminga, identified for the first time in the 1970s. What is this mysterious source of gamma radiation? And what does it have to do with the unusual abundance of high-energy positrons that hit our planet? I am Denis Ariel and you are watching the Astrum Brasil. Join me today to tune in to the enigmatic frequency of Gemminga, whose gamma radiation has been illuminating the world of astrophysics for decades. Have you not yet experienced the incredible sensation of observing the moon up close? Or another planet in our solar system? Or even a comet? Observing and recording the night sky can be a very stimulating activity, with the potential to expand your knowledge of the laws of physics, celestial objects and their characteristics, of the seasons and changes. Anyway, I personally recommend it. And for those of you who always ask me where to get the equipment, we proudly present our dear partner Photon Astro, the largest astronomical equipment store in Brazil. A store specializing in astronomy and astrophotography equipment, with a large and diverse catalog of products created especially for you, a lover of the night sky. There you will find telescopes, cameras dedicated to astrophotography, mounts for sky tracking, filters, accessories and much more. In addition to having several products in stock in Brazil ready to go, you can also order the imported products and pay nothing more than the fixed value on the site. Access the link in the description of this video, and when you decide to close the purchase, use the Astrum coupon to guarantee a discount. In our night sky, nestled in the Gemini constellation in the northern celestial hemisphere, something peculiar is happening. In 1972, the small NASA's Astronomical Satellite-2, or SAS-2, identified an unknown source of gamma radiation. But with the technology available at the time, the best it could do was to trace its origin to this wider region of our Milky Way. Thus, the final source of radiation remained hidden among the stars for decades. However, it received a name, Geminga, named in 1976 by the Italian physicist Giovanni Benyammi, who would dedicate his career to studying it. It is a game of words, a combination of Gemini, the region where it is located, and gamma, the type of radiation it emits. Geminga is also a pun in the Milanese dialect of Benyammi, which means it is not there, a name appropriate for a cloud of unknown-origin gamma rays. It was only in 1983 that Benyammi and his team finally had their big chance. They managed to identify a weak X-ray signal from Geminga, using Einstein's X-ray satellite. This meant that although its exact position remained unknown, they could restrict their search area and were approaching the discovery of Geminga's hiding place. But that didn't answer the big question, which was, after all, since astronomers could only offer vague guesses about the true nature of the source. This until 1991, when they had another stroke of luck. Two different missions identified the radiation coming from Geminga, and they were not constant signals, but pulses. The first of these discoveries was made with a X-ray telescope built in Germany, known as ROSAT, the abbreviation of the German word for X-ray. ROSAT was the first to identify pulses in the X-ray signal from Geminga, and soon after, they were also confirmed in the gamma wave lengths by the Experimental Telescope of Energy Gamma Rays, or EGRET, a telescope aboard the satellite of NASA's Compton Gamma Ray Observatory. These complementary observations not only showed that X-rays and gamma rays came from Geminga, but for the first time revealed what Geminga was. With a period of 0.237 seconds, blinking as it rotated around its axis at just over 4 hertz, or four times per second, Geminga behaved like a pulsar. A pulsar is a type of neutron star that rotates rapidly, emitting radiation beams that sweep through space like a cosmic spotlight. From across the galaxy, most pulsars seem to emit radio waves, from a few times per minute to 700 times per second. And at that point, in the early 90s, they were incredibly rare. Before ROSAT and EGRET, only two other high-energy gamma ray pulsars had been identified, the crab and sail pulsars, and these were different from Geminga in some important aspects. First, in addition to the gamma rays, both pulsars also produced radio waves, and therefore were visible using radiotelescopes. Therefore, if Geminga were a pulsar, it would be the first discovery of one that was apparently silent in terms of radio, emitting enough radiation just to be seen in the wavelengths of gamma and X-rays. And second, the crab and sail pulsars are surrounded by their respective nebulae, traces of when they were created from supernova explosions. But Geminga's nebula was notable for its absence. So, why is Geminga, this powerful source of gamma rays, so good at hiding from our radiotelescopes? Where is your nebula? Or could it be a completely different type of object? Well, the answer to the first question is, in part, because we were not hearing correctly, due to the limitations of the technology available, and due to our understanding of radio emissions of these remaining stellar. Although radio pulsars can emit radio waves in a wide bandwidth, from up to 17 MHz, to above 87 GHz, about half the radio spectrum, not all of these frequencies travel well through space. Although we have known since the 1970s that radio pulsars often reach peaks between 100 and 200 MHz, where they are intrinsically brighter, factors such as interstellar medium, the bottom temperature of the sky, and the effects of the ionosphere, mean that lower frequencies are attenuated as they cross space, resulting in very weak signals and more difficult to detect. As these radio signals are so weak, most radiotelescopes did not look for them, instead, limiting themselves to looking for signals between 430 and 1600 MHz. This would have been acceptable, if Geminga had behaved as expected for one of its kind. As this did not happen, scientists only realized in 1997 what was happening. Three independent observations of the Puchino Radio Astronomy Observatory, were able to identify extremely weak pulses of Geminga, using a sensitive traffic antenna. Weak radio pulses reached about 100 MHz, which explains why previous searches for Geminga resulted in radio silence. It turns out that Geminga was not really hiding, and was sending us signals, we were just not listening correctly. In the same year, the team led by the late astronomer Janos Jou, theorized that another reason for Geminga to seem silent in terms of radio, may be its magnetic field. Models showed that radio waves can be absorbed or refracted within the pulsar magnetosphere, leaving only weak pulses around 100 MHz detectable. This would effectively make it inactive in the highest radio bands, used by most telescopes. Confirming that Geminga was a pulsar, and specifically a gamma-ray pulsar, was a great feat. In fact, 99% of its emission is in the gamma band, making it one of the brightest gamma-ray sources in our entire galaxy. As you can see, everything that remained after a star, several times more massive than our sun, exploded about 350,000 years ago. But its relative radio silence, and the apparent absence of a nebula, were not the only unusual things about this pulsar. When Italian astrophysicists, including Biame, who named Geminga, compared a series of observations of the 3.6-meter telescope of the European Southern Observatory, and the New Technology Telescope, with observations of the Canadian-French-Hawaiian Telescope, they discovered that Geminga was moving. In addition, it was traveling at a speed normally high of about 0.2 arc seconds per year. As a reminder, a second of arc is a very small unit of angular measurement, used when we need more precise measurements than one degree would allow. Within each degree of arc, there are 60 minutes of arc, and within each minute of arc, there are 60 seconds of arc. These seconds of arc are a common unit used in astronomy to describe the movement of objects in the sky, from our perspective on Earth. If you drew a circle around the orbit of the Moon around the Earth, there would be 360 degrees around this circular path. Therefore, at any time of the day or night, assuming that nothing is blocking your horizon view, you can see about 180 degrees of the sky, and from the horizon to the zenith, the top of the sky is 90 degrees. If you extend your little finger with your arm extended and close your eye, the tip of your little finger will cover about one degree of the sky, approximately. The next time you are outdoors on a clear night, try to do this, and see if your little finger can cover the Moon. It should, because the Moon occupies only about half a degree, or about 31 minutes of arc in the night sky. Gemini traveling 0.2 seconds of arc through our sky each year may not seem much, but from our perspective on Earth, a typical star moves only a few thousandths of a second of arc per year. However, despite being 800 light years from us, Gemini will travel 30 minutes of arc, the equivalent of the apparent diameter of the Moon, through our sky in just over 10,000 years. In other words, this stellar corpse is running through the galaxy, at almost 210 kilometers per second. Going towards the border between the constellations of Gemini and Lynx, and in its current rate of movement, Gemini will remain twins for another half a million years, but may need a new name after that. However, this mysterious pulsar is even stranger. It is its enormous speed that helps to produce another feature that scientists were about to discover. As it moves through space, Gemini leaves behind two ghostly tails of X-rays that extend for 3 trillion kilometers in the sky. As I mentioned earlier, despite this fast-moving pulsar being almost silent in terms of radio, it is certainly not silent in the wavelengths of gamma rays and X-rays. In 1999, the multi-X-ray mirror mission of ESA, or XMM-Newton, was launched to explore this X-ray universe more deeply. And four years later, a team led by Patricia Caraveo discovered these X-ray trails similar to comets. Its shape and brightness are partially explained by the shock wave created by the movement of Gemini in space, and its rotation like a pulsar. But it also reveals another attribute, the colossal mass of Gemini. Measuring only about 20 to 30 kilometers in diameter, Gemini is extremely dense, containing approximately the same mass as a sun and a half. To put this into perspective, if you had a teaspoon of neutron star material, it would weigh about 4 billion tons, equivalent to 10,000 buildings in Paris State. As this dense and massive object advances through the low-density interstellar medium, only 0.06 to 0.15 atoms per cubic centimeter, it compresses the interstellar medium and its own magnetic field incorporated by a factor of 4. Meanwhile, the incessant rotation of the neutron star creates an environment where the electrons and their antimatter counterparts, called positrons, can be accelerated to extreme energies, powerful enough to emit high-energy gamma rays. Although most of these electrons are seen in the gamma radiation that escapes the pulsar, some are trapped and spiral within this intensified magnetic field. In these images of a computational model, the tails can be seen scratching the edges of the three-dimensional shock wave of Geminga, like the raft created by a boat crossing the water. But this boat is more massive than our sun, and the raft is made up of X-rays of very high energy. But the final piece of Geminga's puzzle was only discovered in 2005, its Nebula. Taking the form of a neutral hydrogen gas shell, with a radius of 0.4 parsecs in width, it turned out to be what we call a pulsar wind nebula. This type of nebula is created from the plasma wind emanating from the magnetic poles of a pulsar. The plasma made of charged particles that can be accelerated at speeds close to the speed of light, involves the pulsar, creating a high-energy particle nebula that allows strong X-ray emissions. With the confirmation that Geminga really had a nebula, its identity as a pulsar could finally be confirmed. But Chandra's telescope went even further. In addition to obtaining images of Geminga, Chandra also observed a second pulsar, called B0355-54. And comparing the two, astronomers discovered another possible explanation for the absence of radio pulses in Geminga. Superficially, these pulsars seem quite similar. Both are about half a million years old, and rotate about 4 or 5 times per second. However, as you know, Geminga is mainly seen in gamma-ray pulses, without bright radio emissions. In contrast, the other pulsar, which I will call B, is not seen in gamma rays, and instead it is one of the brightest known radio pulsars. How can these two pulsars be so similar, but so vastly different in the way we see them? The answer may be as simple as the orientation of each of these pulsars in relation to our observation of the Earth. Astronomers believe that these images of Geminga and B0355-54 revealed their axis of rotation, and discovered a reason why radio pulses and gamma rays may be present or absent in different pulsars. Just like our own magnetic field around the Earth, both pulsars have magnetic poles close to their rotation poles. These poles are where the radio pulsating emissions come from. You can try to model this by poking a small foam ball right in the middle. The foam ball is a pulsar, and the radio waves coming from the poles are represented by the wooden spike coming out of both ends. If you rotate the ball around the spike like an axis of rotation, you create a equator around the middle. To illustrate the source of gamma rays along the equator, you could make a hole in a piece of paper and press it on the foam ball. Now you have a gamma ray disk radiating from the equator in all directions. With Geminga, the edge of the paper disk is pointing to us, which means that the gamma rays are heading to Earth. For the pulsar B, its relative position in relation to us is at a different angle, as if it were looking at the flat surface of the disk. The gamma rays are moving perpendicularly to our line of vision, therefore not reaching the Earth. Let's look again at the two images of Chandra from Geminga on the left and Pulsar B on the right, along with artistic illustrations of how astronomers believe the nebulae of the pulsar wind look alike. In the image of Pulsar B, the long blue tails represent the radio waves emanating from its poles, and the spike coming out of both ends. But instead of being straight like a wooden spike, Pulsar B is moving so fast through space that these jets seem curved backwards, dragging backwards as the pulsar moves through space. Now look at the image of Geminga. Here, the long twin tails on both sides of the image are the radio waves, following behind while it also advances through space. But this time, instead of pointing almost directly away from our point of view on Earth, these jets seem to be pointing to the sides, not to Earth. So when astronomers look at Geminga, they see powerful gamma ray emissions from the equator, but the radio jets point to the sides and remain invisible. And when they look at Pulsar B, the opposite happens. The radio jets are pointed almost directly to our planet, while the gamma ray source in the equator does not reach Earth. Sometimes the simplest explanation is the correct one, and that finally brings us back to the mystery of decades, of an unusual abundance of antimatter bombing our planet. For more than a decade, a particle detector called Alpha Magnetic Spectrometer, or AMS-02, is coupled to the International Space Station, collecting information about antimatter, dark matter and cosmic ray sources. As a reminder, cosmic rays are energetic particles, fragments of atoms, that travel through space at a speed close to light. They can be produced by the sun, by supernova explosions, or by other cosmic means. In 2013, the first results of the AMS-02 experiment were announced. The detector had registered more than 400,000 positrons, the largest sample of positron data of cosmic rays ever collected, and increasing by 100 times the total data of positrons of cosmic rays in the world. For years, many astronomers and physicists hoped that this excess of antimatter could be the by-product of the annihilation of dark matter, offering possible clues about this mysterious substance. After all, dark matter can make up about 27% of the cosmos, and yet we do not know what it is. Like common matter, dark matter contains mass and occupies space, but it does not seem to absorb, reflect or interact with light, at least not in a way that we can detect. Some theorize that dark matter can be composed of types of particles not yet identified. Whatever it is, scientists had great hopes that the superabundance of antimatter detected aboard the International Space Station could contain clues about the true nature of dark matter. Unfortunately, they were disappointed. The more scientists analyze the data, the clearer they become. The most likely source of these positrons may actually be the pulsars. Astrophysicists had long suspected this, but until 2017 there was simply no proof. It was the Cherenkov Gamma-ray Observatory of High-Altitude Water, or HALC, that finally added evidence to this hypothesis. A small halo of gamma radiation was identified around Geminga, with trillions of times more energy than is visible to our eyes, from 5 to 40 trillion electron volts, the type of radiation generally produced by positrons. This was the first real observational evidence pointing to a pulsar as a potential source. Pulsars naturally surround a cloud of electrons and their equivalent positrons, as a result of the intense magnetic field of the star. This intense magnetic field attracts particles from the surface of the pulsar and accelerates them to speeds close to that of light. Scientists believe that these accelerated positrons and electrons collide with starlight, bringing light to higher energies, which then radiates like the halo of gamma rays observed. But, based on the size of the halo observed by the HALC team, the positrons of Geminga would rarely have the energy needed to reach our planet, and therefore, they believed that the excess of positrons should have a more exotic source. Until new impressive information was discovered a few years later, thanks to a team led by astrophysicist Mathias de Mauro. Using a decade of gamma-ray data on Geminga, acquired by the Fermi Large Area Telescope, which is able to observe light of less energy than the HALC gamma-ray observatory, the team of de Mauro managed to subtract all other sources of gamma rays to reveal a spectacular brightness coming from Geminga, much, much greater than any other that scientists had ever seen. This vast halo of bright gamma rays, with an energy of 10 billion electron volts, covered 20 degrees of the sky, similar to the area occupied by the constellation of Ursa Major. And that's not all. The brightness of gamma radiation is even greater in lower energies. If we could see it with the naked eye, the gamma brightness of Geminga would dominate our sky, covering an area 40 times larger than that of the full moon. With this new information, astrophysicists discovered that the size of the halo of Geminga meant that this pulsar alone could be responsible for up to 20% of the excess of positrons detected near the Earth. From there, it is not difficult to imagine that other pulsars are the most likely culprits for the remaining abundance of antimatter that we find. This explanation may not have solved the mystery of dark matter, but it is certainly a magnificent revelation. It was Jocelyn Bell Burnell who discovered the first pulsar in 1967, at a time when people thought that these regular signs could be a work of extraterrestrial life. In the almost 60 years that have passed since then, we have found thousands of pulsars, and our understanding of these neutron stars has grown with each of them. And since Geminga was identified as only the third gamma-ray pulsar known in 1991, we have seen more than 300 thanks to NASA's Fermi mission. But given the history of Geminga in challenging expectations and promoting science, I like to think that this particular pulsar still has more secrets to reveal. Thank you very much to all who subscribe to the channel, all who comment, watch and enjoy the content. 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