Determining the exact number of galaxies in the Universe is a huge task that remains unattainable at the moment. However, the Canadian Space Agency (CSA) has revealed that experts suggest a figure higher than one billion galaxies. With such a large number, it is not surprising that there is what can be called a twin galaxy of the Milky Way in the vicinity of our galaxy, where our planet is located.
In this article we are going to tell you everything you need to know about the discovery of the Milky Way's twin galaxy and its characteristics.
Discovery of the Milky Way's twin galaxy
During his summer holidays in Cantabria last year, Renowned astrophysicist Luca Costantin enjoyed a day of leisure on August 1. After exploring the lush green mountains and sandy beaches of San Vicente de la Barquera, he turned on his laptop and checked his email, a habit he admits to having even when he's on vacation. Among the new messages was a set of captivating images captured by the revolutionary James Webb Space Telescope, launched on Christmas 2021.
As he examined the images and classified various galaxies, one in particular caught his attention. He had discovered Ceers-2112, a galaxy that could be considered the "twin sister" of the Milky Way on the opposite side of the universe. This discovery is detailed in this week's edition of the prestigious scientific journal Nature. It is worth noting that the universe is estimated to be 13.800 billion years old.
According to a study by Costantin and his colleagues, galaxies that look like the Milky Way existed 11.700 billion years ago, when the universe was only 15% of its current age. The ultrasensitive James Webb telescope has captured the faint light emitted during the universe's infancy. "It's as if we were seeing our galaxy in the past," says Costantin, a 33-year-old Italian researcher.
Astrophysicist Pablo G. Pérez González compares the discovery to that of a 100-year-old person who has never seen himself in the mirror receiving a self-portrait sent by an unknown twin sister when he was 15 years old. This is the most remote Milky Way-like galaxy ever discovered, known as ceers-2112. This galaxy is located in the region of the sky between the constellations Ursa Major and Boyero, which is a dotted line that resembles a human figure and has the star Arthur, one of the brightest in the sky.
Galaxy Ceers-2112
According to Pérez González, one of the main authors of the study, the combined mass of the stars in ceers-2112 is equivalent to 3.900 billion solar masses, a size that agrees with simulations of the dimensions of the Milky Way at the time. "At that time there were ten times less solar masses in our galaxy," explains the researcher, who researches with Costantin at the Astrobiology Center (INTA-CSIC) in Torrejón de Ardoz, Madrid. Like other spiral galaxies in the local universe, the Milky Way has a bar-shaped structure in its central area, which is elongated. About 15 years ago, the Hubble Space Telescope, which was launched in 1990 and was primitive compared to the current James Webb Space Telescope, allowed approximately 2.000 similar galaxies to be examined.
The conclusion reached by NASA astronomers is that the central bars of spiral galaxies are the result of the evolution of galaxies. Bars form when stars' orbits become unstable and deviate from their previous circular paths. Large amounts of gases accumulate in these elongated structures, giving rise to new stars and transforming galaxies.
The young ceers-2112 is an example of a galaxy that surprisingly has a bar in its center, despite being only 2.100 billion years old when it emitted the light that reached the telescope. The importance of these structures, according to Pablo G. Pérez González, lies in the fact that they play a crucial role in the formation of life. For the Sun to form from its essential metals, including iron, nickel, carbon, silicon and all the other ingredients of life, previous stars must have had elliptical orbits, transporting materials from which more stars form in a galaxy towards the outer areas.
Ancient twin galaxy of the Milky Way
Announced three years ago, the existence of SPT0418-47, a “twin” galaxy of the Milky Way, had already been established as a colossal and stable entity when the cosmos was just 1.400 billion years old. However, it lacked a bar. According to Pérez González, «The Milky Way can have countless twins, and we observe each of them at different times in the universe. "These twins can provide us with a timeline of the evolution of the Milky Way."
The galaxy ceers-2112 is named after the international Cosmic Evolution Early Release Science project, in which astrophysicists from the Center for Astrobiology participate. Although he did not participate in the study, Mexican astrophysicist Yetli Rosas Guevara praised the research. He states: “This is the first publication to identify spiral galaxies with a central bar in the infancy of the universe. Given the young age, we would expect things to be more turbulent«. Guevara carries out cosmological simulations at the Donostia International Physics Center in San Sebastián. According to Rosas Guevara, the impact of the James Webb Space Telescope on the field of astronomy cannot be underestimated.
Thanks to this powerful tool, astronomers have been able to detect the initial galaxies that emerged in the universe. Guevara points out that with additional observations, it could be determined whether ceers-2112 was a singular event during the early universe or whether numerous galaxies similar to the Milky Way already existed.
As you can see, with each discovery we place pieces of the puzzle of our universe to better understand how it is formed and its entire composition. I hope that with this information you can learn more about the characteristics of the main Milky Way galaxy and its discoveries.