Atenção!: Os tamanhos não estão em escala. He fusion=>C significa que o Hélio, por sua vez, se funde em outro elemento, o Carbono. E assim são criados os elementos nas estrelas, e somente as supernovas ao explodir criam os mais pesados.
Astrofísicos da Universidade de Sydney, Austrália, estão por trás de uma grande descoberta no estudo dos cidadãos seniores de nossa galáxia: as estrelas conhecidas como gigantes vermelhas.
Usando instrumentos de medição de intensidade de brilho, de alta precisão, levados pela espaçonave Kepler, cientistas conseguiram distinguir profundas diferenças no interior do núcleo de estrelas que, de outra forma, parecem iguais na superfície.
A descoberta, publicada na última edição da revista Nature, e tornada possível através de observações utilizando o poderoso telesópio espacial Kepler da NASA, está lançando novas luzes sobre a questão da evolução das estrelas, inclusive do nosso Sol.
Autor principal do artigo, o professor da University de Sydney, Tim Bedding, explica, "Gigantes vermelhas são estrelas evoluídas que exauriram o suprimento de hidrogênio em seus núcleos, que possibilita a fusão nuclear, e em vez disso queimam hidrogênio numa região circundante. Perto do final de suas vidas, as gigantes vermelhas começam a queimar hélio em seus núcleos (o hélio era o hidrogênio original, que se fundiu, transformando-se neste outro elemento)."
O telescópio espacial Kepler permitiu ao Professor Bedding e colegas estudar continuamente a luz estelar de centenas de gigantes vermelhas com um nível de precisão sem precedentes durante cerca de um ano, abrindo uma janela para os núcleos das estrelas.
"As mudanças no brilho da superfície de uma estrela são o resultado de movimentos turbulentos no interior que causam contínuos tremores estelares (algo análogo aos terremotos), criando ondas sonoras que viajam para baixo através de seu interior e retornam à superfície," disse o professor Bedding.
"Sob as condições ideiais, essas ondas interagem com outras ondas presas no núcleo de hélio da estrela. São esses modos de oscilações "misturadas" a chave da compreensão da vida de uma estrela em determinado estágio. Medindo cuidadosamente sutilíssimas características das oscilações no brilho de uma estrela, pode-se ver que algumas estrelas esgotaram o hiodrogênio do núcleo e estão agora queimando hélio, e estão por conseguinte num estágio mais tardio de vida."
O astrônomo Travis Metcalfe do Centro Nacional para Pesquisas Atmosféricas dos EUA, em um texto associado na mesma edição da Nature que ressalta a significância da descoberta, compara gigantes vermelhas com estrelas de Hollywood, cuja idade nem sempre é óbvia na aparência. "Durante certas fases da vida de uma estrela, seu tamanho e brilhosidade são notavelmente constantes, mesmo enquanto profundas transformações ocorrem nas profundezas de seu interior."
O professor Bedding e seus colegas trabalham num campo em expansão chamado astrosismologia. "Da mesma forma que os geólogos usam terremotos para exporar o interior da Terra, nós utilizamos os tremores estelares para examinar a estrutura interna de estrelas," explicou.
O professor Bedding disse: "Nós estamos bastante animados com os resultados. Nós tínhamos alguma ideia de modelos teóricos de que esses sutis padrões de oscilação estariam presentes lá, mas isso confirma nossos modelos. Nos permite distinguir as gigantes vermelhas, e nós poderemos comparar a fração de estrelas que estão em estágios diferentes de evolução de uma maneira que não podíamos antes."
Daniel Huber, um estudante PhD que trabalha com o professor Bedding, completou: "Isso mostra o quão maravilhoso o telescópio satélite Kepler realmente é. O objetivo principal do Kepler era encontrar planetas do tamanho da terra habitáveis, mas isso também nos deu uma grande oportunidade de aprimorar nossa compreensão das estrelas."
University of Sydney astrophysicists are behind a major breakthrough in the study of the senior citizens of our galaxy: stars known as Red Giants. Using high precision brightness measurements taken by the Kepler spacecraft, scientists have been able to distinguish profound differences inside the cores of stars that otherwise look the same on the surface.
The discovery, published in the latest edition of the journal Nature and made possible by observations using NASA's powerful Kepler space telescope, is shedding new light on the evolution of stars, including our own sun.
The paper's lead author, the University of Sydney's Professor Tim Bedding, explains, "Red giants are evolved stars that have exhausted the supply of hydrogen in their cores that powers nuclear fusion, and instead burn hydrogen in a surrounding shell. Towards the end of their lives, red giants begin burning the helium in their cores."
The Kepler space telescope has allowed Professor Bedding and colleagues to continuously study starlight from hundreds of red giants at an unprecedented level of precision for nearly a year, opening up a window into the stars' cores.
"The changes in brightness at a star's surface is a result of turbulent motions inside that cause continuous star-quakes, creating sound waves that travel down through the interior and back to the surface," Professor Bedding said.
"Under the right conditions, these waves interact with other waves trapped inside the star's helium core. It is these 'mixed' oscillation modes that are the key to understanding a star's particular life stage. By carefully measuring very subtle features of the oscillations in a star's brightness, we can see that some stars have run out of hydrogen in the center and are now burning helium, and are therefore at a later stage of life."
Astronomer Travis Metcalfe of the US National Center for Atmospheric Research, in a companion piece in the same Nature issue which highlights the discovery's significance, compares red giants to Hollywood stars, whose age is not always obvious from the surface. "During certain phases in a star's life, its size and brightness are remarkably constant, even while profound transformations are taking place deep inside."
Professor Bedding and his colleagues work in an expanding field called asteroseismology. "In the same way that geologists use earthquakes to explore Earth's interior, we use star quakes to explore the internal structure of stars," he explained.
Professor Bedding said: "We are very excited about the results. We had some idea from theoretical models that these subtle oscillation patterns would be there, but this confirms our models. It allows us to tell red giants apart, and we will be able to compare the fraction of stars that are at the different stages of evolution in a way that we couldn't before."
Daniel Huber, a PhD student working with Professor Bedding, added: "This shows how wonderful the Kepler satellite really is. The main aim of the telescope was to find Earth-sized planets that could be habitable, but it has also provided us with a great opportunity to improve our understanding of stars."
University of Sydney astrophysicists are behind a major breakthrough in the study of the senior citizens of our galaxy: stars known as Red Giants. Using high precision brightness measurements taken by the Kepler spacecraft, scientists have been able to distinguish profound differences inside the cores of stars that otherwise look the same on the surface.
The discovery, published in the latest edition of the journal Nature and made possible by observations using NASA's powerful Kepler space telescope, is shedding new light on the evolution of stars, including our own sun.
The paper's lead author, the University of Sydney's Professor Tim Bedding, explains, "Red giants are evolved stars that have exhausted the supply of hydrogen in their cores that powers nuclear fusion, and instead burn hydrogen in a surrounding shell. Towards the end of their lives, red giants begin burning the helium in their cores."
The Kepler space telescope has allowed Professor Bedding and colleagues to continuously study starlight from hundreds of red giants at an unprecedented level of precision for nearly a year, opening up a window into the stars' cores.
"The changes in brightness at a star's surface is a result of turbulent motions inside that cause continuous star-quakes, creating sound waves that travel down through the interior and back to the surface," Professor Bedding said.
"Under the right conditions, these waves interact with other waves trapped inside the star's helium core. It is these 'mixed' oscillation modes that are the key to understanding a star's particular life stage. By carefully measuring very subtle features of the oscillations in a star's brightness, we can see that some stars have run out of hydrogen in the center and are now burning helium, and are therefore at a later stage of life."
Astronomer Travis Metcalfe of the US National Center for Atmospheric Research, in a companion piece in the same Nature issue which highlights the discovery's significance, compares red giants to Hollywood stars, whose age is not always obvious from the surface. "During certain phases in a star's life, its size and brightness are remarkably constant, even while profound transformations are taking place deep inside."
Professor Bedding and his colleagues work in an expanding field called asteroseismology. "In the same way that geologists use earthquakes to explore Earth's interior, we use star quakes to explore the internal structure of stars," he explained.
Professor Bedding said: "We are very excited about the results. We had some idea from theoretical models that these subtle oscillation patterns would be there, but this confirms our models. It allows us to tell red giants apart, and we will be able to compare the fraction of stars that are at the different stages of evolution in a way that we couldn't before."
Daniel Huber, a PhD student working with Professor Bedding, added: "This shows how wonderful the Kepler satellite really is. The main aim of the telescope was to find Earth-sized planets that could be habitable, but it has also provided us with a great opportunity to improve our understanding of stars."
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