510152025 As astronomers gaze into the depths of space, theydo so with unease: They don’t know precisely whatthe universe is made of. Surprisingly, no one knows the stars’ exactchemical composition: how many carbon, nitrogenand oxygen atoms they have relative to hydrogen, themost common element. These numbers are crucial, because they affecthow stars live and die, what types of planets form andeven how readily life might arise on other worlds. Twenty years ago, astronomers expressedconfidence in the numbers they had been workingwith. Now, not so much. The problem lies not in thefar corners of the cosmos, but much closer to home.Astonishingly, scientists don’t know exactly what thesun is made of. As a result, they don’t know what theother stars are made of, either. “The sun is a fundamental yardstick,” says MartinAsplund, an astrophysicist at the Max PlanckInstitute for Astrophysics, in Germany. “When wedetermine the abundance of a certain element in astar or a galaxy or a gas cloud anywhere in theuniverse, we use the sun as a reference point.” The sun’s location in the Milky Way also makes ita good representative of the entire galaxy. Most starsreside in giant galaxies like the Milky Way, whichmakes the sun a touchstone for the entire cosmos. For nearly a century, astronomers have judgedstars normal or not by seeing whether their chemicalcompositions match the sun’s. Most stars near us do;some don’t.
Scientific American. 1 July 2020. Adaptado.
Segundo o texto, conhecer a composição de elementos químicos que constituem as estrelas é fundamental, pois ela, entre outros aspectos,