Cosmology

A diagram illustrating the combined power of the James Webb and Hubble space telescopes in studying Cepheids present in the galaxy NGC 5584 with the NIRCam (Near-Infrared Camera) and WFC3 (Wide Field Camera 3) instruments, respectively

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An article accepted for publication in “The Astrophysical Journal” reports the results of calculating the universe’s expansion rate based on the observation of Cepheids with the James Webb Space Telescope. In particular, a team of researchers led by Adam Riess used the NIRCam instrument to observe over 330 cepheids in the galaxies NGC 4258 and NGC 5584. The results are more precise than those obtained in the past with the Hubble Space Telescope but confirm the accuracy of the previous calculation of the universe’s expansion rate. This leaves open the question of the difference in results obtained with different methods.

JADES-GS-z13-0, JADES-GS-z12-0, and JADES-GS-z11-0

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An article published in the journal “Proceedings of the National Academy of Sciences” reports the discovery of candidate supermassive dark stars observed by the James Webb Space Telescope. Cosmin Ilie, Jillian Paulin, and Katherine Freese argue that three of what were considered primordial galaxies have characteristics of a type of object that so far was only hypothesized. According to the model proposed in 2007, supermassive dark stars have a large dark matter component that powers them instead of nuclear fusion. These strange objects could reach masses up to ten million times the Sun’s and a brightness up to ten billion times the Sun’s, which could lead to mistaking them for primordial galaxies.

The Euclid Space Telescope blasting off atop a Falcon 9 rocket (Image courtesy SpaceX)

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A little while ago, ESA’s Euclid Space Telescope was launched atop a SpaceX Falcon 9 rocket from Cape Canaveral. After just over 40 minutes, it successfully separated from the rocket’s last stage and entered its course that will take it towards the so-called L2 point, about 1.5 million kilometers from Earth, where its scientific mission will begin with an investigation of the dark universe.

The Euclid Space Telescope mission is focused on the cosmological mysteries connected to dark matter and dark energy. Cosmological research in recent decades indicates that the universe we see with the ordinary matter that forms galaxies constitutes only a small part of the cosmos. Astronomers and physicists are having difficulty investigating parts of the cosmos that we can neither see nor directly detect. It’s a problem that makes it difficult to test models that try to explain the effects that led to hypothesize the existence of dark matter and dark energy. For this reason, ESA developed a scientific mission focused on these cosmological problems.

Diagram of Earth as a detection center for very low-frequency gravitational waves emitted by pairs of supermassive black holes (top) using pulsars (bottom) (Image courtesy EPTA)

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A series of articles published or being published in the journals “Astronomy and Astrophysics” and “The Astrophysical Journal Letters” reports various aspects of the detection of very low-frequency gravitational waves. Researchers from the European Pulsar Timing Array (EPTA), the Indian Pulsar Timing Array (InPta), the Parkes Pulsar Timing Array (PPTA), the Chinese Pulsar Timing Array (CPTA), and the North American Nanohertz Observatory for Gravitational Waves (NanoGrav) analyzed data collected over the course of more than 25 years using groups of pulsars to obtain a kind of detector of gravitational waves at the galactic level. This was possible by exploiting the extreme regularity of the signals emitted by pulsars to detect variations of less than a millionth of a second and their correlations to identify gravitational waves. This technique expands the gravitational-wave astronomy opened up by the LIGO and Virgo detectors since the announcement of the first detection in February 2016.

The map of dark matter based on observations from the Atacama Cosmology Telescope

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During the Future Science with CMB x LSS conference underway at Kyoto University, Japan, the results of a detailed mapping of dark matter in a part of the universe were presented. Three articles available in preview and submitted to “The Astrophysical Journal” illustrate these results, obtained using observations conducted at the Atacama Cosmology Telescope (ACT) in Chile, which operated between 2007 and 2022. This map (Image courtesy ACT Collaboration) was obtained by analyzing the cosmic microwave background radiation and its deviations caused to the gravity of massive structures such as concentrations of dark matter.