Stellar remnants are the key to understanding the origin and future of the cosmos

The remains of stars at the end of their lives, known as stellar remnants, are a window to decipher the mysteries of the universe and its evolution. Not only does it bring us closer to understanding the origin of the cosmos, but it also drives technological innovationsaid William Henry Lee Alardin, a physicist at the National Autonomous University of Mexico (UNAM), who has dedicated more than 20 years of his life to observing neutron stars and black holes.

In interview with The Daythe scientist explained that depending on the initial mass of the star, the stellar remnant can take on different shapes: white dwarfs (if it has 8 times the mass of the Sun); neutron stars (if you have between 8 and 25); and black holes (if you have 25).

If we talk about the end of a small star, the process is calm: its outer layers are slowly ejected to form a white dwarf. On the other hand, if they are massive they end with a violent explosion, throwing elements at 30 thousand kilometers per second.

Lee Alardin, who received the Gabino Barreda medal in 1992 and the National University Distinction for Young Academics in 2009, explained that although almost all the hydrogen and helium in the universe was produced during the Big Bang, other elements such as carbon, nitrogen, Oxygen, iron, silicon, cobalt, nickel and uranium are produced throughout the life and death of stars.

natural laboratory

It is important to study these remnants because it is under these extreme conditions that the matter of which our galaxy, our planet, and ourselves are made is formed. These phenomena are a natural laboratory to understand their behavior.

Another reason to observe bodies such as white dwarfs, neutron dwarfs or black holes, added the astrophysicist, is that they provide data on the populations of stars in the Milky Way and other galaxies, with this we can understand their spatial distribution, their composition chemistry, their ages and their movement.

“Although we have made enormous progress in some topics, we are still not clear about what star formation processes and stellar demography are like. Why are there a certain number of stars, of certain masses, and why not others?

In the large-scale structure of the universe, stars are the fundamental building block of galaxies, so if we do not understand how they are formed, we will not understand much about galaxies.he stated.

The specialist highlighted that one more reason to study them has to do with the tools that must be created to observe them. “The stellar remnants are very hot and shine in ultraviolet light, X-rays and gamma rays, to see them we must develop techniques, instruments, observatories, softwarewhich triggers a series of technological implements that may later have other applications.”

For example, during the covid pandemic, a UNAM computer team developed a tool to analyze chest films to find out if there were lesions in the lungs, with a technique very similar to that used in astronomy to see if what is observed in space is a spot or a galaxy.

In the past 10 years, LIGO and Virgo, gravitational wave detection observatories, have made significant discoveries. One of them is the presence of black holes in binary systems that have between 50 and 200 times the mass of the Sun.

We knew of black holes in our galaxy 30 and 40 times the mass of the Sun, and we hope to see more of those. But LIGO detected holes with larger masses that we had never seen before. This raises new questions, challenges to knowledge: which stars gave rise to these black holes?.

But the study of the remnants not only brings us closer to understanding the origin of the cosmos, but also drives technological innovation and strengthens international collaboration, said Lee Alardín, who also directs the coordination of International Relations and Affairs (CRAI) at UNAM. .

“The investment required by the projects and the sites from which observatories can be established are key reasons why astronomy is a very international science.

The list of places suitable for stargazing is very small, just a couple of sites on islands or mountain ranges near the sea. Now, a technical and scientific collaboration allows us to split the bill for a project.

Regarding the future and the big questions to be resolved, Lee Alardin believes that the work is in achieving a better characterization of the cosmos from the detection of gravitational waves combined with observatories that find different types of light, such as X-rays or infrared. There is a section of the gravitational wave spectrum that we have not observed.

The researcher said that a bet for the coming years is the LISA project, which aims to launch three satellites in 2037 to observe sources of low-frequency gravitational waves. Which will complement the discoveries made by experiments such as LIGO and Virgo in the high frequency range.

In Mexico, he highlighted the role played by the robotic telescope hummingbird which this year was installed at the National Astronomical Observatory of San Pedro Mártir and whose main purpose is to identify and monitor gamma ray bursts. This device will be networked with two other ground-based telescopes in China and the Franco-Chinese SVOM satellite launched in June this year.

“Stellar remnants are more than vestiges of extinct stars: they are the key to our understanding of the origin and future of the cosmos. With projects like LISA and hummingbirdhumanity is closer to deciphering the mysteries of the universe and its evolution.”