Lift your gaze and be carried away by the lights that shine in the Universe, stars so close yet so far, in space and above all in time. The fascination of infinity. Who at least once hasn't dreamed of the inscrutable with their nose upturned? It is no coincidence that the observation of the night sky over the centuries has given rise to mythological characters and stories that, despite the passage of time, persist in the languages and cultures of peoples. Sardinia is no exception and of the almost 400 that have a name, the best known, the Polare, the Sardinians call it Su Norte.
In a boundless Cosmos it cannot be imagined that only the Earth is inhabited by sentient beings, even if there are no traces. Astronomers keep searching. Thus, poking with hyper-technological eyes less than a month ago they detected something sensational that even confirmed the existence of Black Holes: a worldwide network of radio telescopes observed, coming from areas even two billion light years away, a powerful emission of Gamma rays. These are large quantities of matter capable of transforming themselves into energy in a few moments. Those recorded on October 9th, arrived to us with an astonishing delay of two billion years, seem to be due to the collapse of a massive star that imploding gave birth to a Black Hole.
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Sardinia makes its contribution with an important astronomical observatory: in Selargius, where many people work, some are radio astronomers, they can see billions of light years away. Their work enchants adults but also children. Who, as we know, first of all look at the Moon: they see it close to you that you can almost touch, and they ask many questions.
Maria Francesca Chiappe
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A Gamma Flash reveals the birth of a Black Hole
La prima immagine di un buco nero (foto Ansa)
In the past three years, the eyes of humanity have seen images of two large Black Holes for the first time. Observed with a worldwide network of radio telescopes, they have given us proof of the existence of Black Holes, confirming some hypotheses about their appearance and nature. A few days ago the news came that telescopes located in space and on Earth observed a powerful emission of Gamma rays on 9 October.
For astronomers, this explosion came from a nascent Black Hole. Gamma bursts, called Gamma Ray Bursts (GRBs), are powerful energy emissions from remote areas of our Universe, billions of light years away. The energy of a gamma-ray burst is generated in seconds. Its intensity is equal to or greater than that produced by a star like the Sun over its entire existence. These explosions are born in violent phenomena, where in a few moments large quantities of matter are transformed into energy. Mergers of pairs of Neutron stars, collisions between a Black Hole and a Neutron Star, are some of the events that could give rise to a GRB. But the massive Gamma lightning recorded in early October appears to have been born in the collapse of a large star at least 2 billion light years away. A massive star, now at the end of its life, which imploding gave rise to a Black Hole, releasing an enormous amount of energy. On 9 October we recorded what we can define the "first cry" of a Black Hole, which came to us with a delay of about 2 billion years.
The questions
Black Holes, but what are they? Remains of massive stars described by Einstein's General Relativity. Gravitational wells that until 30 years ago were a topic of discussion for theoretical physicists and astrophysicists. Today, however, children also talk about it and are the protagonists of highly successful cinematic colossals. A huge boost to their popularity was given by the famous book by the English physicist Stephen Hawking, “From the Big Bang to Black Holes”: it describes these strange celestial objects able to imprison light by bending spacetime. A black hole is the extreme manifestation of the force of gravity, the force that keeps us glued to the surface of the Earth and that governs the motion of the planets around the Sun. It was Newton in 1687 who discovered the force of gravity, describing its behavior with the law of Universal Gravitation.
Thanks to this law we can do some math. For example, it is possible for a human being to leave the Earth, but only if he reaches the escape speed of 40,000 km / h. If, on the other hand, we assume to concentrate the Earth in a radius 1,000 times smaller, to leave it we would have to reach the incredible speed of 1.3 million km / h. Based on these considerations in 1783 the English scientist John Michell hypothesized the existence of a Dark Star. Star of such large mass and so concentrated that not even light could escape, making it in fact a black and dark star. Years passed and when Albert Einstein published the theory of General Relativity in 1915, the German astronomer Karl Schwarzschild, a fighter on the Russian front, took up his work and found the first solution to those equations. The result he obtained described a strange object, so dense as to curve space time and such as not to allow light to escape, a Dark Star. THE
The name
The name Black Hole will arrive only in 1967. Coined by astrophysicist John Archibald Wheeler, it best describes the nature of these objects, similar to a well surrounded by an edge beyond which nothing, not even light, can come back. But that border is not just a point of no return, it is a shell that prevents us from observing what happens beyond, a horizon that hides events.
So what's in the abyss of a Black Hole, beyond the event horizon? According to General Relativity, a singularity is hidden, a place with infinite density, where the laws of physics no longer have value, including Relativity itself. The mystery of the singularity stirs the dreams of theoretical physicists. Perhaps it will be the description of the infinitely small, quantum mechanics, to help us understand what lies beyond the event horizon. But what happens near a Black Hole seems paradoxical. As well told in the film Interstellar, when the protagonists travel near the Black Hole, time slows down so much that it almost seems to cancel itself out. If, according to man, time flows in a uniform and immutable way, Einstein showed instead that time is relative and flows differently depending on the conditions in which one finds oneself. For Einstein, matter acts on spacetime by deforming it. Because of this, an observer who approaches a celestial body slows down in the passage of time. The Earth itself creates this effect, imperceptible to our senses, but important when we calculate the position of an object on our planet with GPS satellites. If the Earth collapsed into a Black Hole, everything would change. Its radius would be less than one centimeter and time would slow down considerably. A hypothetical astronaut who lived on the Moon, watching a friend of his near the Black Hole Earth would never see him grow old. While the inhabitants of the Earth would see astronauts grow old and die in a few hours or minutes. A Black Hole is therefore not just a well, it is also a powerful time machine.
For a long time, astronomers have searched for clues to the existence of Black Holes, and physicists have tried to simulate their behavior and shape. From observations of the great Black Holes at the center of galaxies and from that wail coming from a distance of over two billion light years, perhaps we will be able to cast a light beyond the abyss of the event horizon, to unravel the mysteries of Black Holes.
Manuel Floris
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Su Carru Mannu and Su Norte: the autumn sky in Sardinia
(foto Floris)
Observing the night sky has always aroused wonder in man. Turning his gaze to the celestial vault and wondering about the meaning of the cosmos, he joined the stars to form figures: the constellations.
Characters and incredible stories were represented in the sky. Traces of this mythical world have remained in the languages and cultures of the peoples, even in the Sardinian language. If we observe the sky on these nights it is easy to recognize the seven stars of the Big Dipper, Su Carru Mannu, in a northerly direction. It is the oldest known asterism, and in Sardinia it bears several names: Sete Frades, - Sette Fratelli, perhaps a reference to the mountain formation north-east of Cagliari - or Sete Bacas, the seven cows, from the Latin name of constellation "septemtrio", the seven oxen, from which north. In the Big Dipper there is a pair of very close stars, Mizar and Alcor, which in Sardinian takes the name of Sos Turbadores, the two metal rings through which the bridle, sos frenos, allows the oxen to be guided, disturbed.
If almost 400 stars have a name, the best known is certainly the Polar Star. Less bright than others, it is the only star that appears stationary in the night, while the whole sky seems to revolve around it. To find it, the two rear stars of the Chariot are joined and a line is drawn until you find a bright enough star, Polaris. Called in Sardinian Su Norte, with six other stars it forms the Piccolo Carro, Su Carru Piticu. The two chariots belong to larger constellations, the Ursa Major and the Ursa Minor. The Bear is also a very ancient figure, of Indo-European origin, but which is also found in North America. Also to the north, opposite the Big Dipper with respect to the Polar, is Cassiopeia. Unmistakable for its W shape, for the Greeks it represented the queen of Ethiopia. The most common representation sees her sitting on the throne and in Sardinian she is known as Sa Trona. In this area of the sky the Greeks set a great myth, with all the protagonists represented by constellations. Cassiopeia boasted of being more beautiful than the Nereids, sea nymphs, unleashing the wrath of Poseidon who sent the monster Cetus, the Whale, to devastate Ethiopia. To appease the wrath of the god, King Cepheus, after hearing an oracle, decided to offer his daughter Andromeda as a sacrifice to the monster. But Perseus intervened in time, who on the back of the winged horse Pegasus killed the monster and married the girl. Among these constellations, that of Perseus is known in Sardinia as Su Corru 'and Chervu, the Horn of the deer.
To an attentive observer the sky appears to be in motion, with the stars moving in the night from east to west. If at the beginning of the evening the Summer Triangle formed by the stars Vega, Altair and Deneb dominates us, as night falls, it turns to sunset, leaving room for the winter constellations that face east. Among these, in the constellation of Taurus, we find a small group of stars, the Pleiades. If for the Greeks the Pleiades were seven sisters, in northern Sardinia they are known as Sos Puddighinos, the Gallinelle. Throughout Sardinia, however, they are known as Su Budrone, the bunch of grapes, and their evening rise in autumn marks the beginning of the transhumance towards the plain: «Cando su Budrone betat a mare est ora de calare in Campidanu».
Fabrizio Pedes
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“In Selargius we study the cosmos. Aliens? Unlikely to be alone "
Emilio Molinari (foto L'Unione Sarda)
The earliest memory, "the farthest", is a Hoepli pocket planetarium received as a gift. "Amazing thing, it had semi-circular pages that could be rotated and showed the position of the constellations in the sky." A few years later, in high school, the discovery of the telescope: a small tube with a 6 cm lens «with which I still look at Saturn from time to time». Today he uses a 64-meter radio wave dish in Sardinia after using two smaller but very powerful optical telescopes in the Canaries and Chile.
The child who raised his eyes to the sky half a century ago was amazed by the beauty of the stars has become a researcher who studies the Universe, observes planets and galaxies and directs fundamental infrastructures to discover their details. An astrophysicist. Landed in Sardinia after directing the Galileo National Telescope for 9 years in the Canary Islands, he coordinates a team of 70 people who study the cosmos between Selargius and San Basilio as director of the Astronomical Observatory of Cagliari, one of the 17 research structures that belong to the 'National Institute of Astrophysics. Emilio Molinari is 59 years old, comes from Saronno, is married, has two children and has always had a passion for astronomy. Since 2017 he has been director of the Selargius astronomical observatory, on which the large Gerrei radio telescope, "one of the best and most sensitive in the world", depends. From the small instrument of a few centimeters useful for direct observation, «often from the terrace of the house I point it towards the sky and look», to the gigantic parabola that captures radio waves and transforms them into sounds, images, graphics. A huge leap, many more responsibilities. With the same enthusiasm of the origins.
Director, what are you looking for in Selargius?
“There are several working groups. Many are radio astronomers. Radio waves allow us to observe what we are not allowed to see in normal light. For example we are targeting the largest structures in the Universe, such as clusters of galaxies. We can also see some billions of light years away ».
What discoveries have you made?
"Among the most recent and important is perhaps the explosion of a magnetar, a star with an enormous magnetic field."
What are the main scientific activities today?
«The study of galaxies and pulsars, neutron stars that emit beams of waves, real beacons in space. But also the observation of the sun, visible with the radio telescope even if it rains: the weather forecasts of the solar system are important to prevent solar storms that can damage the functioning of the many probes sent to the planets and of the satellites now in daily use ».
When was the Observatory born?
«In 1899 in Carloforte. It was a station created to observe the passage of the stars and calculate the time. There were four or five others in the world. Then in 1979 we moved to Poggio dei Pini, Capoterra, where a laser beam was fired at the satellites and returned to measure the position of the town on the earth's sphere: it was used to understand how the various tectonic plates move. Around the year 2000 with the astrophysicist Nichi d'Amico, who died in 2020, it was decided to build the Sardinia radio telescope in San Basilio, managed by the Observatory. The logical consequence was to build a headquarters near Cagliari but not too far from San Basilio, so we moved to the former Selargius powder keg which was converted into a Science Campus. Inaugurated in 2013, it is still in the expansion phase ».
What role does the island play in observing the cosmos?
«The radio telescope is not among the largest but it is one of the best, modern and most sensitive on a planetary level. It plays a decisive role in different types of observations and will be further refined in 2023 thanks to European funding of € 18 million. It will pick up higher frequencies, in the order of 100 giga Hertz, and will allow us to see things that are currently unobservable. A level reached by few instruments in the world. In addition, the Italian Space Agency uses 20% of the observing time for interplanetary communications and space exploration of our surroundings in collaboration with NASA. In short, it is a very versatile tool ».
What does an astrophysicist do?
«He has several skills. There is the theorist who creates models and who observes, who builds the telescopes and who the instruments ».
Who works with you?
“About 70 people, mostly Sardinians and young people. Computer scientists, technicians, administrators, theoretical astrophysicists and those who scrutinize space. We collaborate with colleagues from all over the world, from Canada to the United States to China to observe the same phenomena in a different light. Radio telescopes can be virtually connected to each other and simultaneously observe the same object: it is called "interferometry", it allows you to exploit a virtual radio telescope that is practically as large as the distance between real telescopes ».
Do non-experts show interest in topics of this type?
“We often offer an outreach program with the participation of students and the public, and every time we run out of places. Everyone is surprised to discover how technological Sardinia is. At the 2020 Expo in Dubai, a documentary by director Gabriele Salvatores was screened in a continuous cycle: it lasted 20 minutes, one was dedicated to each Italian region. For Sardinia 20 seconds were dedicated to the Sardinia radio telescope ».
How does the radio telescope work?
«It collects the electromagnetic waves arriving from the cosmos and conveys them into a receiver which transforms them into an electrical signal and a number which in turn are transformed into images, sounds, graphics».
Little poetic compared to the observation of the planets and stars of the sky.
“For direct observation you need that telescope with a refractor of a few centimeters. With the "Srt" we collect electromagnetic waves in the field of radio waves. None of our senses are useful for perceiving them, so they must be transformed into something usable ».
So what is astrophysics?
«The search for awareness of our place in the Universe. Understanding where we are and what the cosmos is made of. Sometimes it serves to reduce us ».
Are there other forms of life in the universe?
"We do not know. No trace was found. But the number of planets we know exist in the galaxy, and the huge number of galaxies, makes it statistically unlikely that Earth is the only planet with intelligent life. "
So is it possible that intelligent life forms have tried to contact us?
“We participate in the Seti extraterrestrial life research program because we know ours is not the only solar system. So it is important to look for other forms of life. But at the moment there is no evidence or suspicion that anyone has tried to contact us ».
Do you think there could be life on other planets and in other galaxies?
“I'm an astrophysicist, so let's go back to the field of statistics. I admit that I would like to live the moment in which it will pass to certainty. Now our technology still has limits ».
Where will technology take us?
«The radio astronomy projects are international and we actively participate in them. The hundreds of connected antennas will allow us to go much further in space and time by picking up much weaker signals. Maybe those of hypothetical control towers for aircraft on other planets. There are always surprises ».
Andrea Manunza
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The curiosities of the little ones - The Moon
La Luna (foto Ansa)
The Moon is the first object that remains imprinted on a child in front of the night sky. It is large and bright. It looks mysterious, but so close it can almost be touched. It is seen at different times and its shape seems to change over time. As the days go by, the Moon is illuminated differently from the Sun, so it has a day and a night like the Earth. A "lunar day" is marked by the alternation of the phases of the moon, lasts just over 29 Earth days and depends on the movement of the Moon around the Earth. But the Moon in orbit around our planet hides a side from us: how can this happen?
The Moon completes a complete revolution around the Earth in just over 27 days, the same time it takes to make a revolution on itself. We can think of the Moon as in love with our world. He walks around him without ever taking his eyes off him. The love of the Moon is none other than the force of gravity that keeps our satellite tied to the Earth and that has oriented the densest and most massive part of the Moon towards us in 4.5 billion years.
How big is the moon?
The Moon is smaller than the Earth. If we reduce the size of the Earth to that of a large orange, the Moon would be about the size of a walnut, with its radius 4 times smaller than that of our planet.
How far is it?
The Moon is not always at the same distance, but more or less it is located at 384,000 km, a number so large that it is not understood by our mind. So if we take our Earth in the form of orange and the Moon in the form of a walnut, we should place the walnut about four meters from the orange, to roughly reproduce the Earth-Moon distance.
Who lives on the moon?
There is no life on the moon. There is no liquid water and the atmosphere necessary to make our Moon habitable. In the future, perhaps man will live there, building underground bases where new scientific experiments can be carried out.
What is it made of and how many holes does it have?
The Moon is made of rock like our Earth. Its surface is covered with plains, mountains and valleys and the "holes" are called craters. There are at least 700,000 craters larger than a kilometer, born as a result of the fall of comets and asteroids.
How many astronauts have been on the moon?
Twelve astronauts walked on the moon, arriving there after a journey of just over 3 days. There were six Apollo missions that managed to bring men to the moon, while the famous Apollo 13 mission failed to land.
The wonders of the Cosmos in the latest discoveries | L'Unione Sarda
