question archive The GMT will explore the nature of dark matter, which exists outside the otherwise successful Standard Model of particle physics, through the statistics and properties of the most dark-matter-dominated halos—the ultra-faint dwarf galaxies around our own Milky Way
The GMT will explore the nature of dark matter, which exists outside the otherwise successful Standard Model of particle physics, through the statistics and properties of the most dark-matter-dominated halos—the ultra-faint dwarf galaxies around our own Milky Way
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The GMT will explore the nature of dark matter, which exists outside the otherwise successful Standard Model of particle physics, through the statistics and properties of the most dark-matter-dominated halos—the ultra-faint dwarf galaxies around our own Milky Way.
How did the universe form and grow? The universe began in a hot Big Bang 13.8 billion years ago, and has been expanding and cooling ever since. After nearly a hundred years of study, we know that the universe is mostly made up of dark matter and dark energy, with normal matter—everything we can actually see— comprising just a small fraction of the universe's mass and energy. Our model for the Big Bang and the subsequent evolution of the universe is well supported by empirical evidence, but the nature of dark matter and dark energy remains unknown. Our understanding is framed by our bedrock theories of physics that have been directly tested over a limited range of conditions. Extreme environments in the cosmos—from the earliest moments of the Big Bang itself to the recently-discovered sources of gravitational waves—offer new opportunities to test these theories. The GMT will offer new ways to challenge and refine our understanding of the physical laws that govern the universe.
Edwin Hubble's 1929 discovery that our universe is expanding profoundly changed astrophysical research and captured considerable public interest. In the 1930's Fritz Zwicky made the first attempt to weigh a collection of galaxies by measuring their orbital velocities. To his surprise, he found that the galaxies were much more massive than their collection of stars. The mysterious but dominant constituent of galaxies has still not been identified, although it now has a name: dark matter. In the late 1990s, two teams of scientists discovered that the expansion of the universe is accelerating, driven by an unknown energy source we call dark energy. The discovery of dark energy has fostered a further explosion of experimental, observational, and theoretical research.
The evidence for dark matter comes from astronomical observations that detect dark matter over a vast range of scales from the smallest, faint galaxies to large clusters of galaxies. The only alternative to the existence of dark matter would be a modification to the law of gravity. Such a modification to the theory of gravity is becoming more and more untenable. Einstein's general relativity, our anchoring theory for gravity, has been tested many times and so far has passed each test. Recent detections of gravitational wave sources have further strengthened our confidence in general relativity.
The GMT's enormous aperture, extraordinary spatial resolution, and powerful instruments will enable potentially revolutionary investigations of the distribution of dark matter. Detailed studies of very low mass galaxies hold particular promise because dark matter completely dominates their contents. We anticipate that LSST will discover many extremely faint dwarf galaxies for GMT to examine with its powerful spectrographs. GMT observations will reveal the details of the stellar dynamics of these galaxies and the distribution of the dark matter they contain.
To make progress in understanding the fundamental nature of dark matter, we need new observational constraints, and dark matter halos around galaxies are an obvious target. The most appealing candidates for such work at present are dwarf galaxies, and in particular the ultra-faint dwarf galaxy satellites (UFDs) of the Milky Way.
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Through the use of the statistics and properties of the most dark-matter-dominated halos—the ultra-faint dwarf galaxies around our own Milky Way—the GMT will investigate the existence of dark matter, which resides beyond the otherwise successful Standard Model of particle physics.
How did the world come into being and expand? The universe started 13.8 billion years ago with a big bang and has been expanding and cooling ever since. We already assume that the universe is entirely made up of dark matter and dark energy, with regular matter—what we can actually see—making up just a tiny fraction of the universe's mass and energy after nearly a century of research. The origin of dark matter and dark energy remains uncertain, despite the fact that our model for the Big Bang and subsequent evolution of the universe is well supported by empirical evidence. Our view is framed by fundamental physics hypotheses that have been explicitly evaluated under a restricted set of circumstances. Extreme conditions in the universe, ranging from the earliest moments of the Big Bang to newly found gravitational wave origins, provide new ways to test these theories. The GMT will provide new opportunities to test and refine our knowledge of the physical laws that control the universe.
The discovery that our universe is expanding by Edwin Hubble in 1929 revolutionized astronomical science and sparked widespread public interest. Fritz Zwicky made the first attempt to weigh a group of galaxies by calculating their orbital velocities in the 1930s, where he was shocked to find that galaxies were much more large than their star systems. Although it now has a name called as dark matter, the elusive but dominant constituent of galaxies has yet to be identified. Two teams of scientists discovered in the late 1990s that the universe's expansion is speeding up, thanks to an unseen energy force known as dark energy. Dark energy's discovery has triggered a new wave of experimental, empirical, and theoretical research.
Astronomical observations that detect dark matter over a wide range of scales, from the smallest, faint galaxies to massive clusters of galaxies, provide evidence for the existence of dark matter. The only way to rule out the presence of dark matter is to change the law of gravity. However, such a shift to the theory of gravity is becoming increasingly unfeasible. General relativity, Einstein's anchoring principle for gravity, has been put to the test several times and has passed each time. The discovery of gravitational wave origins recently has reinforced our confidence in general relativity.
The GMT's broad aperture, high spatial resolution, and powerful instruments will allow potentially groundbreaking studies of dark matter distribution. Since dark matter completely dominates the contents of very low mass galaxies, comprehensive studies of them hold particular promise. We can expect LSST to find a large number of extremely faint dwarf galaxies for GMT to study with its reliable spectrographs. The stellar dynamics of these galaxies, as well as the distribution of the dark matter they contain, will be revealed by GMT observations.
We needed new observational constraints to understand the fundamental nature of dark matter, and dark matter halos around galaxies are an obvious goal. Dwarf galaxies, especially the Milky Way's ultra-faint dwarf galaxy satellites (UFDs), are currently the most appealing candidates for such research.
