A team of researchers from the Spanish Astrobiology Center (CAB) has just presented the most accurate star map of the Milky Way on record to date. In this celestial plane, which was built mainly with the observations of the Gaia telescope of the European Space Agency, three of the great spiral arms of stars that make up our galaxy can be clearly seen: the arm of Orion, where the Solar System is ; the arm of Perseus, located at the outer edge of the Galaxy, and the arm of Sagittarius, which is towards the center of the Milky Way. During the research process, the CAB group of scientists, led by Michelangelo Pantaleoni González and Jesús Maíz Apellániz , discovered a hidden structure that they named the Cepheus spur.
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Pantaleoni, a young researcher who, despite not having finished his degree in Physics, is already the author of six scientific publications in the journals with the greatest impact in his field, says that this new region is essentially a “bridge of massive blue stars. that extends by a branch of 10,000 light years in length and leaves the spiral arm of Orion to connect with the arm of Perseus ”. According to the researcher, the Cepheus spur had not been seen before because such a complete and detailed stellar catalog did not exist. “In the galactic map that we have drawn, which is the update of the ALS catalog (of Alma Luminous Stars ) and has 20,000 classified celestial objects, an over-density of stars is observed in a space that was previously apparently empty,” explains Pantaleoni.
The results of the work, published recently in the British magazine Monthly Notices of the Royal Astronomical Society , show that the spur is not a random alignment of stars but a compact structure that appears to have consistent movement. Even, says Pantaleoni, we found that the entire structure is located slightly above the galactic disk, about 300 light years above the midplane of the galaxy. This difference in height is believed to be caused by a kind of corrugations that have been observed in other neighboring galaxies but that until recently had not been seen in the Milky Way. "Possibly they are oscillations of the galactic disk resulting from the convulsive evolution of the galaxy, perhaps they are the echoes of collisions with other galaxies billions of years ago or perhaps it is something else", says the researcher.
The strip of yellow dots, which it is between the arm of Orion (light blue) and that of Perseus (Red), it is the spur of Cepheus. M. Pantaleoni González, J. Maíz Apellániz, RH Barbá and B. Cameron Reed.
The massive blue stars that make up the new spur, called by astrophysicists OB stars, are the largest, rarest and those with the highest temperature of the galaxy. Of the estimated 400 billion stars in the Milky Way, less than one in a million is an OB star. They are in some ways a "rare disease," says Pantaleoni. While the surface of a star like the Sun is around 5,500 ° C, OB stars exceed 30,000 ° C and have tens of times their mass. The researchers explain that the relationship between an object's temperature and the color it glows in is called Planck's Law. “If we heat a piece of coal to more than 1,000 ºC we will begin to see that it glows a dark red color. If we heat our ember more and more it will eventually reach the temperature of the Sun and shine in a yellowish white color and if we continue we will get the color of that glow to be blue ”, explains Pantaleoni. And he jokes: "There are jokes out there about astrophysicists burning their hands in public toilets for not understanding the color code of the taps."
Apellániz and Pantaleoni state that OB stars are the most interesting objects that can be studied in the universe because the nuclear reactions that occur inside them are particularly violent. This makes them the largest factories of heavy elements on the periodic table that nature can offer. "The elements that our planet is made of, such as silicon or phosphorous atoms in our DNA, mostly come from inside stars of this type that died billions of years ago," says Pantaleoni. In addition, massive blue stars are the triggers for large outbreaks of star formation. When an OB star dies, it releases enormous energy in the form of a supernova, which compresses the interstellar gas over several light years. This compressed gas reaches very high temperatures and is the basis for the formation of new stars. "An OB star can, with its death, give life to hundreds of stars like the Sun," says Pantaleoni.
However, for scientists at the Center for Astrobiology of Spain, the most relevant of these OB stars that make up the new spur is that have extremely short lives on the geologic time scale. "Some barely live a couple of million years, five thousand times less than the Sun will live," explains the researcher. He continues: “This means that they cannot have changed their position in the galaxy much. We almost always find them near the star-forming regions, where the Galaxy is active, it is alive ”. That is why this discovery helps to understand the way in which the stars of our Galaxy are born. "The new spur shows how the production of new elements is maintained and how matter is recycled in the universe," explains Pantaleoni, "ultimately it is directly related to the formation of planets in other stars and to the chemical basis of life. ”.
Rodolfo Barbá, co-author of the article and professor of astrophysics at the University of La Serena in Chile, compares this work of creating galactic maps with the planes of the earth that were made in the Enlightenment. “We cannot send space probes to the nearest stars, but we are probing the coasts of the Milky Way using the light that comes to us from the distant lighthouses that are the OB stars.”
According to Barbá, we are in the era of exploration of our Galaxy, facing the same debates and problems of the great voyages of exploration of the 16th and 17th centuries. “In the cartographic expeditions of other times, the Baja California peninsula seemed separated from the American continent until enough data was obtained to show that it was not an island, but that it connected to land in the North. We are now debating whether the galactic arm to which the Sun belongs connects at some point with the other arms or whether it is alone on an island. ”
Pantaleoni says that during the research process there were many exciting moments. “The moment of discovery of the spur is curious. It wasn't an explosive revelation, but there was something inside me that was transformed. It is what hooks you and what gives meaning to so much effort, "he says. And he adds: “We were in front of the computer of Jesús [ Apellániz ] when he began to suspect an overdensity of points on the map, I ran to make a special diagram to see how consistent the idea that there was a structure was there, and it appeared
At those times, Pantaleoni confesses, doubts assail you and you spend hours thinking how to refute yourself, but after a few days the arguments were piling up in favor of the fact that there was indeed a bridge between the arms of Orion and Perseus . “It was Jesus, my mentor, who gave him the name of the spur of Cepheus. Without him I would never have glimpsed the importance of that moment. " The young scientist who alternates his classes at the university with work at the CAB explains that Apellániz has an unusual research method. Instead of drawing general conclusions by probing thousands of data, examine it on a case-by-case basis. This “artisan” way of working is inefficient if you are looking for obvious things, but it is extremely productive when you seek to discover subtle clues of what nature shows us. For Jesus, each OB star is different and I would say that he knows each one of them in detail ”, concludes Pantaleoni.
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