Chandra solves the problem of the "missing mass" of the universe


The universe hides its missing mass

Astronomers have used Chandra to possibly identify the location of one-third of the hydrogen, helium and other elements created after the Big Bang, but which do not occur. have not yet been found in the current universe. This "missing mass" may consist of large hot and hot gas filaments known as WHIM. The graph on the left shows how the X-rays of a far quasar were absorbed by the gas contained in these filaments.

New findings from NASA's Chandra X-ray observatory may have helped to solve the Universe's "missing mass" problem. Astronomers can not represent about a third of the normal matter – that is, hydrogen, helium and other elements – which were created about a billion dollars ago. Years after the start of the war. big Bang.

Scientists have proposed that the missing mass can be hidden in gigantic strands or filaments of hot gas (temperature below 100 000 Kelvin) and hot (temperature above 100 000 K) in an intergalactic space. Astronomers call these filaments the "warm-hot intergalactic medium" or WHIM. They are invisible to optical light telescopes, but some of the hot gas contained in the filaments has been detected in ultraviolet light. The main part of this graphic comes from the Millennium simulation, which uses supercomputers to formulate how the key components of the Universe, including the WHIM, would have evolved over cosmic time.

If these filaments exist, they could absorb certain types of light, such as the X-rays that pass through them. The box in this graph represents some of the X-ray data Chandra collects from a fast-growing, far-away supermassif. black hole known as quasar. The plot is a spectrum – the amount of x-rays over a range of wavelengths – a result of a new quasar study H1821 + 643 located at around 3.4 billion years ago. light of the Earth.

The most recent result uses a new technique that, at the same time, refines the WHIM search and strengthens the relatively weak absorption signature by combining different parts of the spectrum to find a valid signal. With this technique, the researchers identified 17 possible filaments located between the quasar and the Earth and obtained their distances.

Where does the universe hide its missing mass?

An image of the Millenium simulation that explains how the key components of the Universe, including the WHIM, have evolved over time. Credit: Illustration: Springel et al. (2005); Spectrum: NASA / CXC / CfA / Kovács et al.

For each filament, the spectrum was shifted in wavelength in order to suppress the effects of cosmic expansion, then the spectra of all the filaments were summed so that the resulting spectrum had a signal. much stronger absorption by WHIM than in individual spectra.

Indeed, the team did not find any absorption in the individual spectra. But by adding them together, they transformed a 5.5-day observation into the equivalent of nearly 100 days (about 8 million seconds) of data. This revealed an oxygen absorption line believed to be present in a gas with a temperature of about one million Kelvin.

Extrapolating from these observations of oxygen to all elements and the region observed at the local universe, the researchers indicate that they can account for the complete amount of missing material.

An article describing these findings was published in The Astrophysical Journal on February 13, 2019. The authors of the article are Orsolya Kovács, Akos Bogdan, Randall Smith, Ralph Kraft and William Forman, all from the Center for Astrophysics | Harvard & Smithsonian in Cambridge, Mass.

NASA's Marshall Space Flight Center in Huntsville, Alabama, runs the Chandra Program for the NASA Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's scientific and aerial activities.

Paper: Detection of missing baryons to the line of sight of H1821 + 643

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