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Using the powerful Japanese Subaru telescope, an international team of researchers has created and analyzed the larger-scale map of the three-dimensional distribution of matter in the universe.
The collaboration team of the Hyper Suprime-Cam (HSC) survey, comprising scientists from Princeton University, Japan and Taiwan, used tiny gravitational distortions of about 10 million galaxies to accurately measure the size of matter in the universe.
By combining this measurement with the observations of the cosmic microwave satellite and other cosmological experiments carried out by the Planck satellite of the European Space Agency, the team was able to further limit the properties of the dark energy that dominates the universe. They shared the results of their first year of data collection in a study on September 25th.
It is thought that over 80% of matter in the universe is a dark matter, a mysterious form of matter that is not made up of ordinary atoms that make up our body. Although dark matter can not be seen directly, its gravitational effects, predicted by Albert Einstein's general theory of relativity, cause the stretching and compression of light from distant galaxies when it is dark. they traverse the cosmos, distorting their apparent forms.
The Subaru telescope can detect this stretch and compression, called "gravitational lenses", to observe the growth of the cosmic structure that can be used to unlock the mysteries of dark matter and energy. The new observations are consistent with the simplest model for dark energy called the "cosmological constant," based on ideas that date back to Einstein.
The gravitational lens effect of dark matter is low, resulting in a distortion of only one percent in images of distant HSC galaxies. Like a pointillist painting, these millions of tiny deformations collectively create a three-dimensional image of the distribution of matter in the universe.
Researchers have specifically characterized these fluctuations – sometimes called "size" or "size" – of dark matter distribution and the evolution of this size over billions of years, of adolescence in adulthood. This rudeness is a key parameter that describes how the universe has developed from its smooth beginnings after the Big Bang to the galaxies, stars, and planets we see today.
Other satellites, including NASA's Cosmic Background Explorer, Wilkinson Microwave Anisotropy Probe and the European Space Agency's Max Planck satellite, observed the first light of the universe, the cosmic background created when the Universe was around 380,000 years old. They showed that the primitive universe was very bland and boring, with only subtle variations in the density of dark matter at the one hundred thousand level.
Over time, the gravitational attraction of dark matter has brought more matter to the slightly dense areas, making them denser and thus reinforcing gravity, resulting in more dark matter, creating stars. , galaxies and clusters of galaxies. On the other hand, the dark energy separates these structures; the growth of cosmic structures therefore depends on a competition between dark matter and black energy.
"Precise measurements of the cosmic structure reveal this dance and the extent to which dark matter has constructed the structure and the energy darkens the skin," said Elinor Medezinski, associate researcher in astrophysics at Princeton, co-author of the study .
The high-precision data collected by the Hyper Suprime-Cam yielded results very similar to those obtained with other lens surveys, including the dark energy study carried out on the Victor Blanco telescope in Chile. Researchers were encouraged by the consistency of the results at different distances and therefore at cosmic times.
By making accurate measurements of very small effects, such as weak lenses, people tend to decide that their analysis is complete if their results confirm previous results. The HSC team performed a blind analysis of its data to avoid such "confirmation bias".
As Jim Bosch, a member of the data analysis team, explained, "We have done all the tests of our catalogs without ever seeing the actual values of the cosmological parameters of the analysis or comparing them to the results of other experiments, pending completely satisfied with the results before allowing us to examine their cosmological implications. "
Until now, the HSC data suggest a slightly less agglomerated universe than that predicted by the Planck satellite, "but it is not yet known if this difference is a statistical fluctuation, or indicates new possible ingredients for our cosmological model" said Cristobal Sifon. a postdoctoral fellow at Princeton. "More data is needed to answer this question."
The research team conducted the HSC survey using the National Astronomical Observatory of the Subaru Japanese Telescope, located near Maunakea's 13,803-foot summit on the Big Island of Hawaii, one of the best astronomical sites in the world. The combination of a large primary mirror (27 feet wide), a wide angle camera can observe an area the size of nine full moons in one take and a superb quality of 39; image makes the telescope well suited to wide but deep imagery of the sky.
During its first 90 nights of observation in its first year of operations, the survey covered approximately 10% of the planned area, observing a band of sky of about 3,000 moons. Once the investigation is complete, the cosmological parameters should be subject to much stricter constraints, which would deepen astronomers' understanding of both dark matter and dark energy.
"We only cover one-tenth of what we expect," said Michael Strauss, professor of astrophysics and co-author of the paper. "When the investigation is complete, it has the potential to deepen our understanding of the standard cosmological model by highlighting the behavior of dark energy."
Research Report: "Cosmic Shear Power Spectrum Cosmology with Subaru Hyper Suprime-Cam's First Year Data"
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Upgrading the GBT to refine the telescope vision
Green Bank WV (SPX) Sep 21, 2018
The National Science Foundation (NSF) has awarded more than $ 1.3 million to upgrade its Green Bank Telescope (GBT) in West Virginia with an innovative measurement system for precision laser telemetry.
This upgrade will allow the telescope to observe celestial objects, day or night, at radio wave lengths of only 3 millimeters. This new capability is essential for studying the chemistry and composition of galaxies, stars, and dense clouds in regions near the center of our galaxy.
The GBT … read more
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