12/30/2023 0 Comments Elliptical vs spiral galaxy![]() ![]() Thus, their relation significantly constrains the space of possible modifications of dynamics or gravity and illuminates the directions for future research that are more likely to shed new light on dark matter and how it is related to baryons. It was first thought by Edwin Hubble that the elliptical galaxy actually evolved into a spiral galaxy. Milgrom suggested more than 30 years ago is not ruled out by their new acceleration relation, a number of more recent theories are. The shape of a galaxy gives a clue to the age and types of star within the galaxy. Spirals have a central bulge surrounded by a flat disk, while elliptical galaxies have no apparent structure other than bright points in their centers. Fun fact: our very own Milky Way is a spiral galaxy, and it is rotating at 168 miles per second. These shapes are typically divided into elliptical, spiral, or irregular. ![]() Some spirals have wide flung arms like the above image of M51, while others have spirals that are more tightly bound. Although the MOND framework itself that M. The first type of galaxies spiral galaxies can be recognized by their wide, flat disks of rotating gas and dust. The Korea-US collaboration carefully selected nearly spherical galaxies from the Sloan Digital Sky Survey and the ATLAS3D survey and showed that they were indeed able to derive an acceleration relation (a possibly Kepler-like law) between baryons (normal matter) and dark or phantom matter. Sheth from the University of Pennsylvania, USA, showed that various dark matter, MOND or MOG scenarios, actually make divergent predictions at 10 to 100 times higher accelerations, and pointed out that massive elliptical galaxies were excellent laboratories for this test. Previous work has studied stars in spiral galaxies, where the gravitational acceleration is typically 100 billion to 1 trillion times smaller than on Earth.Īstrophysicists Kyu-Hyun Chae from Sejong University, South Korea, and Mariangela Bernardi and Ravi K. With this historical lesson in mind, some astronomers have asked if Kepler-like laws of the stellar motions in galaxies may hold a crucial clue to solving the dark matter conundrum. Kepler's empirical laws of how planets orbit the sun, discovered about 400 years ago, led to the development of Newton's theory of dynamics and gravity shortly thereafter. These are the so-called modified Newtonian dynamics (MOND) or modified gravity (MOG) approaches. As the dark matter problem is currently "lost in the dark," other schools of thought have arisen which suggest that instead of looking for missing "phantom" matter, we should instead modify our understanding of dynamics or gravity. ![]() Over the 50 years since, intense worldwide campaigns to detect, directly or indirectly, dark matter particles have not been successful. ![]()
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