A team of researchers from the Spanish Astrobiology Center (CAB) has presented the most accurate map of the Milky Way to date, and has described the existence of the “Cepheus spur”, a formation of blue stars hotter than the sun that had remained hidden until now.
The team mapped Earth’s “solar neighborhood” using the European Space Agency’s Gaia telescope, detailing the spiral arms of the stars that make up our galaxy. These include Orion, where the Solar System is located; Perseus, located at the outer edge of the galaxy, and Sagittarius, towards the center of the Milky Way.
When we discovered the spur, there was no explosive revelation, but something inside me was transformed
Michelangelo Pantaleoni González, scientist at the Spanish Astrobiology Center
Scientists led by Michelangelo Pantaleoni González and Jesús Maíz Apellániz also discovered a hidden structure they called the Cepheus spur, a bridge of massive blue stars between the Arm of Orion and the constellation of Perseus. A blue star is at least three times the mass of the sun and has its nickname because its intense heat means that it appears blue to our eyes.
The Cepheus spur went unnoticed due to the earlier lack of details in the “star catalog” that the researchers just updated. The new map they have drawn “has 20,000 classified celestial objects,” says Pantaleoni González. “You can observe a density of stars in a space that was apparently empty before.” His work was published in the Monthly notices from the Royal Astronomical Society of Great Britain in March.
For scientists, an important aspect of the newly discovered spur is its constant motion, which shows that it is not a random alignment of stars, but rather a structure located on the “galactic disk”, the thin, circular distribution of stars, dust and gas that they often exhibit beautiful spiral patterns. This position could be due to contractions of a type observed in other neighboring galaxies but not seen in the Milky Way. “Possibly these are oscillations of the galactic disk resulting from the convulsive evolution of the galaxy. Maybe it’s the echoes of collisions with other galaxies billions of years ago, or maybe it’s something else, ”says Pantaleoni González.
The massive blue stars that make up the Cepheus spur, also known as OB stars among astrophysicists, are the largest, rarest, and hottest stars in the galaxy. Of the estimated 400 billion stars in the Milky Way, less than one in a million is an OB star, so rare in fact that Pantaleoni González characterizes them as a “rare disease.”
While the surface temperature of a star like the sun is around 5,500ºC, OB stars can exceed 30,000ºC and their mass can be tens of times greater. Pantaleoni González explains that the relationship between the temperature of an object and the color of its brightness is called Planck’s law. “If we heat a piece of coal to more than 1,000ºC we will begin to see it glow a dark red color. If we heat the grill more and more, it will reach the temperature of the sun and will shine a yellowish-white color, and if we continue, the color of that glow will be blue ”, explains Pantaleoni González. “There are jokes about astrophysicists burning their hands in public toilets because they don’t understand the color code on the taps.”
For Pantaleoni González, blue stars are the most interesting objects in the universe because the nuclear reactions that occur inside them are particularly violent, which means that they produce elements that helped build the Earth. “The elements of which our planet is composed, such as silicon or the phosphorous atoms of our DNA, come mainly from the interior of stars of this type that died billions of years ago”, says the young scientist, who has not yet has graduated.
Massive blue stars also create new stars when they die, releasing enormous energy in the form of a supernova, which compresses the gas at very high temperatures and then bursts into a new formation. “An OB star can, in death, give life to hundreds of stars like the sun,” says Pantaleoni González.
While blue stars shine brightly in life, they quickly fade. “Some of them barely live a couple of million years, five thousand times less than the life expectancy of the sun,” explains the researcher. “That means they couldn’t have altered their position in the galaxy much. We almost always find them near the star-forming regions, where the galaxy is active, where it is alive. ” Their discovery, therefore, helps to understand where new stars are born, by identifying a cluster of blue stars that give birth to many more. “The new spur shows how the production of new elements is maintained and how matter is recycled in the universe. Ultimately, it is directly related to the formation of planets in other stars and to the chemical bases of life, ”he says.
The massive blue stars that make up the Cepheus spur are the largest, rarest, and hottest stars in the galaxy.
Rodolfo Barbá, co-author of the article and professor of astrophysics at the University of La Serena in Chile, compares the task of creating galactic maps with maps of the Earth drawn up in the Age of Enlightenment. “We cannot send space probes even to our closest stars, but we are probing the edges of the Milky Way using the light that reaches us from distant beacons, the OB stars,” he says. We are in the era of galaxy exploration, Barbá adds, facing the same debates and problems as the great explorers of Earth in the 16th and 17th centuries. “In the first mapping expeditions, the Baja California peninsula seemed separate from the American continent until enough data was obtained to show that it was not an island. Now we are debating whether the galactic arm to which the sun belongs connects at some point with the other arms or if it is alone on an island. “
Pantaleoni González recounts the moment the team found Cepheus’s spur. “When we discovered the spur, there was no explosive revelation, but something inside me was transformed. That is what attracts you and gives meaning to so much effort, ”he says. “We were in front of [astrophysicist] Jesus [Apellániz]computer when it began to inspect this density of points on the map. I ran to make a special diagram to see if it was consistent with the idea that there was a structure there, and it appeared. “
The young scientist alternates his university classes with work at the Spanish Astrobiology Center. He explains that Apellániz, his mentor, has an unusual research method: “Instead of drawing general conclusions by probing thousands of data, he examines case by case. This ‘artisan’ way of working is ineffective if you are looking for the obvious, but it is extremely productive when you are looking to discover subtle clues of what nature shows us.