The composition of the Universe
The chemical composition of the Universe and the physical nature of its constituent matter are topics that accept occupied scientists for centuries. From its privileged position to a higher place the Earth’due south temper Hubble has been able to contribute significantly to this area of research.
All over the Universe stars work as giant reprocessing plants taking low-cal chemical elements and transforming them into heavier ones. The original, so-called primordial, limerick of the Universe is studied in such fine detail considering it is one of the keys to our understanding of processes in the very early Universe.
Helium in the early Universe
Shortly after the First Servicing Mission successfully corrected the spherical aberration in Hubble’s mirror a team led by European astronomer Peter Jakobsen investigated the nature of the gaseous affair that fills the vast volume of intergalactic infinite. By observing ultraviolet low-cal from a afar quasar, which would otherwise accept been captivated by the Earth’s temper, they found the long-sought signature of helium in the early Universe. This was an important piece of supporting bear witness for the Big Bang theory. It likewise confirmed scientists’ expectation that, in the very early Universe, matter not all the same locked up in stars and galaxies was nearly completely ionised (the atoms were stripped of their electrons). This was an important pace forrard for cosmology.
|The Cosmic Origins Spectrograph is designed to study the composition and large-scale structure of the Universe|
This investigation of helium in the early on Universe is one of many means that Hubble has used distant quasars as lighthouses. As lite from the quasars passes through the intervening intergalactic matter, the lite signal is changed in such a way as to reveal the composition of the gas.
The results have filled in of import pieces of the puzzle of the total limerick of the Universe at present and in the by.
During the servicing mission in 2009, astronauts installed a new instrument dedicated to studying this field. The Cosmic Origins Spectrograph is designed to suspension upwardly ultraviolet light from faraway quasars into its component wavelengths, and study how intervening thing absorbs sure wavelengths more than others. This reveals the fingerprints of different elements, telling u.s.a. more than about their abundances at various locations in the Universe.
Today astronomers believe that around 1 quarter of the mass-energy of the Universe consists of dark matter. This is a substance quite unlike from the normal thing that makes up atoms and the familiar world around us. Hubble has played an important part in work intended to plant the amount of dark matter in the Universe and to decide where information technology is and how it behaves.
The riddle of what the ghostly nighttime affair is made of is withal far from solved, but Hubble’s incredibly sharp observations of gravitational lenses have provided stepping stones for future work in this area.
Nighttime matter merely interacts with gravity, which means it neither reflects, emits or obstructs light (or indeed any other blazon of electromagnetic radiations). Because of this, it cannot be observed directly. Nevertheless, Hubble studies of how clusters of galaxies bend the light that passes through them lets astronomers deduce where the hidden mass lies. This ways that they are able to make maps of where the dark matter lies in a cluster.
|This Hubble/Chandra/VLT composite shows how night thing (in bluish) and hot gas (in pink) are located far apart from each other during a cluster collision.|
Ane of Hubble’s large breakthroughs in this area is the discovery of how dark matter behaves when clusters collide with each other. Studies of a number of these clusters have shown that the location of nighttime matter (as deduced from gravitational lensing with Hubble) does not lucifer the distribution of hot gas (as spotted in X-rays by observatories such every bit ESA’s XMM-Newton or NASA’south Chandra). This strongly supports theories virtually dark matter: we expect hot gases to slow downwardly as they hit each other and the pressure increases. Nighttime matter, on the other hand, should not experience friction or pressure, so we would look it to laissez passer through the collision relatively unhindered. Hubble and Chandra observations have indeed confirmed that this is the case.
In 2018 astronomers used Hubble’s sensitivty to study intracluster light in the chase for dark matter. Intracluster low-cal is a byproduct of interactions between galaxies. In the course of these interactions, individual stars are stripped from their galaxies and float freely within the cluster. Once free from their galaxies, they finish up where the majority of the mass of the cluster, more often than not dark affair, resides. Both the night matter and these isolated stars — which form the intracluster calorie-free — act every bit collisionless components. These follow the gravitational potential of the cluster itself. The written report showed that the intracluster light is aligned with the dark matter, tracing its distribution more than accurately than any other method relying on luminous tracers used so far.
A 3D map of the night matter distribution in the Universe
In 2007 an international team of astronomers used Hubble to create the offset three-dimensional map of the big-calibration distribution of dark matter in the Universe. It was constructed by measuring the shapes of half a one thousand thousand galaxies observed by Hubble. The light of these galaxies traveled — until it reached Hubble — down a path interrupted past clumps of dark matter which deformed the advent of the galaxies. Astronomers used the observed distortion of the galaxies shapes to reconstruct their original shape and could therefore as well calculate the distribution of nighttime matter in betwixt.
This map showed that normal matter, largely in the form of galaxies, accumulates forth the densest concentrations of dark affair. The created map stretches halfway back to the kickoff of the Universe and shows how dark thing grew increasingly clumpy every bit information technology collapsed under gravity. Mapping dark thing distribution down to fifty-fifty smaller scales is fundamental for our agreement of how galaxies grew and clustered over billions of years. Tracing the growth of clustering in dark thing may eventually also shed light on dark free energy.
Nighttime free energy
More intriguing still than dark affair is dark energy. Hubble studies of the expansion charge per unit of the Universe take establish that the expansion is actually speeding up. Astronomers take explained this using the theory of dark free energy, that pushes the Universe autonomously always faster, against the pull of gravity.
As Einstein’s famous equation, Due east=mc2
tells u.s., energy and mass are interchangeable. Studies of the rate of expansion of the creation suggests that night free energy is past far the largest function of the Universe’s mass-free energy content, far outweighing both normal thing and dark matter: information technology seems that dark energy makes almost 70% of the known Universe.
While astronomers have been able to have steps along the path to understanding how dark energy works and what it does, its true nature is still a mystery.
The page on “measuring the age and size of the Universe” as well has information on dark energy and how it relates to the expansion of the cosmos.
Related videos and images
- Animation of dark matter filaments (creative person’s impression)
- Hubblecast episode 05: Hubble finds a ring of dark matter
- Graphic: the history of the Universe
Related news releases
- Hubble tracks down a milky way cluster’s dark affair (2003)
- Stellar survivor from 1572AD supports supernova theory (2004)
- Showtime 3D map of the Universe’s dark matter scaffolding (2007)
- Hubble finds ring of dark matter (2007)
- Clash of clusters provides new dark thing inkling (2008)
- Hubble finds that dark matter interacts with itself even less than previously thought (2015)
- Dark Matter filaments studied in 3D for the kickoff time (2015)
- Hubble finds that Universe may be expending faster than expected (2016)
- Observable universe contains x times more than galaxies than previously thought (2016)
- Hubble discovers wobbling galaxies (2017)
- Faint starlight in Hubble images reveals distribution of dark affair (2018)