Dá sa jedna z najväčších záhad astrofyziky vyriešiť parafrázovaním gravitačnej teórie Alberta Einsteina? Zatiaľ nie, podľa novej štúdie, ktorej je spoluautorom[{“ 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.

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.

Toto video vysvetľuje jav nazývaný gravitačná šošovka, ktorý môže spôsobiť, že obrázky galaxií budú skreslené alebo rozmazané. Toto skreslenie je spôsobené gravitáciou a vedci môžu tento efekt využiť na detekciu temnej hmoty, ktorá nevyžaruje ani neodráža svetlo. Poďakovanie: Goddard Space Flight Center NASA

Vedci z prieskumu Dark Energy Survey sledujú na obrázkoch galaxií jemnejšie skreslenia spôsobené ohýbaním priestoru temnej hmoty, čo je efekt nazývaný slabý gravitačná šošovka. Gravitačná sila určuje veľkosť a distribúciu štruktúr temnej hmoty a veľkosť a distribúcia zase určujú, ako skreslené nám tieto galaxie vyzerajú. Takto môžu obrázky odhaliť silu gravitácie v rôznych vzdialenostiach od Zeme a vo vzdialených časoch v celej histórii vesmíru. Skupina teraz zmerala tvary viac ako 100 miliónov galaxií a doteraz sa pozorovania zhodujú s tým, čo predpovedala Einsteinova teória.

„Stále existuje priestor na spochybnenie Einsteinovej teórie gravitácie, pretože merania sa stávajú presnejšími,“ povedala spoluautorka štúdie Agnes Fertiová, ktorá výskum viedla ako postdoktorandská výskumníčka v JPL. „Stále však musíme urobiť veľa, kým budeme pripravení na Euklida a Romana. Je teda nevyhnutné, aby sme na tomto probléme pokračovali v spolupráci s vedcami z celého sveta, ako sme to urobili pri prieskume temnej energie.“

Referencia: „Výsledky prieskumu tmavej energie tretieho roku: Obmedzenia rozšírenia pre ΛCDM so slabými šošovkami a galaktickými klastrami“ od DES Collaboration: 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. Blažek, S. Bocquet, A. Brandao-Souza, S. L. Bridle, D. Brooks, D. L. Burke, H. Spoločnosť 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 a S. Rodman. Samorov, C. Sanchez, E. Sanchez, J. Sanchez a 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 a J. Zontz, 12. júla 2022, dostupné tu. Astrofyzika > Kozmológia a negalaktická astrofyzika.
arXiv: 2207,05766