Cientistas da NASA exploram a energia escura – hora de reformular a teoria gravitacional de Albert Einstein?

Ilustre a energia escura. Crédito: Visualização por Frank Summers, Space Telescope Science Institute. Simulação por Martin White, UC Berkeley e Lars Hernquist, Harvard University

Um dos maiores mistérios da astrofísica pode ser resolvido parafraseando a teoria da gravidade de Albert Einstein? Ainda não, de acordo com um novo estudo que ele é co-autor[{” attribute=””>NASA scientists.

The universe is expanding at an accelerating rate, and physicists don’t know why. This phenomenon seems to contradict everything scientists understand about gravity’s effect on the cosmos: It’s as if you threw an apple in the air and instead of coming back down, it continued upward, faster and faster. The cause of the cosmic acceleration, dubbed dark energy, remains a mystery.

A new study marks the latest effort to determine whether this is all simply a misunderstanding: that expectations for how gravity works at the scale of the entire universe are flawed or incomplete. This potential misunderstanding might help researchers explain dark energy. However, the study – one of the most precise tests yet of Albert Einstein’s theory of gravity at cosmic scales – finds that the current understanding still appears to be correct. The study was from the international Dark Energy Survey, using the Victor M. Blanco 4-meter Telescope in Chile.

The results, authored by a group of scientists that includes some from NASA’s Jet Propulsion Laboratory (JPL), were presented Wednesday, August 24, at the International Conference on Particle Physics and Cosmology (COSMO’22) in Rio de Janeiro. The work helps set the stage for two upcoming space telescopes that will probe our understanding of gravity with even higher precision than the new study and perhaps finally solve the mystery.

Webb SMACS 0723

This image – the first released from NASA’s James Webb Space Telescope – shows the galaxy cluster SMACS 0723. Some of the galaxies appear smeared or stretched due to a phenomenon called gravitational lensing. This effect can help scientists map the presence of dark matter in the universe. Credit: NASA, ESA, CSA, and STScI

More than a century ago, Albert Einstein developed his Theory of General Relativity to describe gravity. Thus far it has accurately predicted everything from the orbit of Mercury to the existence of black holes. But some scientists have argued that if this theory can’t explain dark energy, then maybe they need to modify some of its equations or add new components.

To find out if that’s the case, members of the Dark Energy Survey looked for evidence that gravity’s strength has varied throughout the universe’s history or over cosmic distances. A positive finding would indicate that Einstein’s theory is incomplete, which might help explain the universe’s accelerating expansion. They also examined data from other telescopes in addition to Blanco, including the ESA (European Space Agency) Planck satellite, and reached the same conclusion.

Einstein’s theory still works, according to the study. So no there’s no explanation for dark energy yet. However, this research will feed into two upcoming missions: ESA’s Euclid mission, slated for launch no earlier than 2023, which has contributions from NASA; and NASA’s Nancy Grace Roman Space Telescope, targeted for launch no later than May 2027. Both telescopes will search for changes in the strength of gravity over time or distance.

Blurred Vision

How do scientists know what happened in the universe’s past? By looking at distant objects. A light-year is a measure of the distance light can travel in a year (about 6 trillion miles, or about 9.5 trillion kilometers). That means an object one light-year away appears to us as it was one year ago, when the light first left the object. And galaxies billions of light-years away appear to us as they did billions of years ago. The new study looked at galaxies stretching back about 5 billion years in the past. Euclid will peer 8 billion years into the past, and Roman will look back 11 billion years.

The galaxies themselves don’t reveal the strength of gravity, but how they look when viewed from Earth does. Most matter in our universe is dark matter, which does not emit, reflect, or otherwise interact with light. While physicists don’t know what it’s made of, they know it’s there, because its gravity gives it away: Large reservoirs of dark matter in our universe warp space itself. As light travels through space, it encounters these portions of warped space, causing images of distant galaxies to appear curved or smeared. This was on display in one of first images released from NASA’s James Webb Space Telescope.

Este vídeo explica um fenômeno chamado lente gravitacional, que pode fazer com que as imagens das galáxias pareçam distorcidas ou borradas. Essa distorção é causada pela gravidade, e os cientistas podem usar o efeito para detectar a matéria escura, que não emite nem reflete luz. Crédito: Goddard Space Flight Center da NASA

Os cientistas do Dark Energy Survey analisam imagens de galáxias em busca de distorções mais sutis devido ao espaço de curvatura da matéria escura, um efeito chamado fraco lente de gravidade. A força da gravidade determina o tamanho e a distribuição das estruturas de matéria escura, e o tamanho e a distribuição, por sua vez, determinam o quão distorcidas essas galáxias nos parecem. É assim que as imagens podem revelar a força da gravidade em diferentes distâncias da Terra e em tempos distantes ao longo da história do universo. O grupo já mediu as formas de mais de 100 milhões de galáxias e, até agora, as observações correspondem ao que a teoria de Einstein previu.

“Ainda há espaço para desafiar a teoria da gravidade de Einstein, à medida que as medições se tornam mais precisas”, disse a coautora do estudo Agnes Ferti, que conduziu a pesquisa como pesquisadora de pós-doutorado no JPL. “Mas ainda temos muito a fazer antes de estarmos prontos para Euclides e Roman. Portanto, é imperativo que continuemos a colaborar com cientistas de todo o mundo neste problema, como fizemos com a pesquisa de energia escura.”

Referência: “Resultados da Pesquisa de Energia Escura do Terceiro Ano: Restrições de Extensão para ΛCDM com Lentes Fracas e Aglomerados Galácticos” Por DES Colaboração: TMC Abbott, M. Aguena, A. Alarcon, O. Alves, A. Amon, J. Annis, S. Avila, D. Bacon, E. Baxter, K. Bechtol, M. R. Becker, G. M. Bernstein, S. Birrer, J. Blazek, S. Bocquet, A. Brandao-Souza, S. L. Bridle, D. Brooks, D. L. Burke, H. Camacho, A. Campos, A.; Carneiro-Roussell, M. Carrasco-Kinde, J. Carretero, F.J. Castander, R. Cawthon, C. Chang, A. Chen, R. Chen, A. Choi, C. Consullis, J. Cordero, M.Costanzi, M. Crocce, LN da Costa, MES Pereira, C. Davis, T.M. Davis, J. DeRose, S. Desai, E. Di Valentino, H.T. Diehl, S. Dodelson, P. Doel, C. Doux, A. Drlica-Wagner, K. Eckert, T. F. Eifler, F. Elsner, J. Elvin-Poole, S. Everett, X. Fang, A. Farahi, I. Ferrero, A. Ferté, B. Flaugher, P Fosalba, D. Friedel, O. Friedrich, J. Frieman, J. García-Bellido, M. Gatti, L. Giani, T. Giannantonio, G. Giannini, D. Gruen, R. R. Gruendl, J. Gschwend, G. Gutierrez , N. Hammos, I. Harrison, W. G. Hartley, K. Herner, SR Hinton, DL; Honshed, H. Huang, M. Hof, de Hutterer, B. Jane, D.J. James, M. Jarvis, N. Jeffrey, T. Geltima, A. Kovacs, Cross, K. Cohn, N.; Kuropatkin, O. Lahav, S.; Lee, P.-F. Leggett, B. Lemus, CD Leonard, AR Liddell, M. Lima, H. Lynn, N. McCran, J.L. Marshall, J. McCullough, J. Mina Fernandez, F. Minanto, R. Mikel, V. Miranda, J. J. Mohr, J. Muir, J. Miles, S. Nadthor, A. Navarro-Alsina, RC Nicoll, RLC Uganda, Y. Aomori, A. Palmis, S Pandey, Y Park, M Paterno, F Paz-Chinchon, WG Percival, A Perez, AA Plazas Malagon, A Buridon, J Pratt, M ​​Raveri, M Rodriguez-Monroy, B Rogozinski, RP Rollins, AK Romer Rodman, A.R. Rosenfeld, A.J. Ross, A. Rykoff e S. Rodman. Samorov, C. Sanchez, E. Sanchez, J. Sanchez e Dr. , M. Smith, M. Soares-Santos, E. Suchyta, M. Tabbutt, G. Tarle, D. Thomas, C. To, A. Troja, M. A. Troxel, I. Tutusaus, T. N. Varga, M. Vincenzi, AR Walker, N. Weverdick, R.H. Wechler, J. Wheeler, P. Yanni, P. Yin, Y. Zhang e J. Zontz, 12 de julho de 2022, disponível aqui. Astrofísica > Cosmologia e astrofísica não galáctica.
arXiv: 2207.05766

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