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Linda Siobhan Sparke is a British astronomer known for her research on the structure and dynamics of galaxies. She is a professor emerita of astronomy at the University of Wisconsin–Madison , [ 1 ] and Explorers Program Scientist in the NASA Astrophysics Division.
Rings. Galaxies are divided into those possessing ring-like structures (denoted ‘(r)’) and those without rings (denoted ‘(s)’). So-called ‘transition’ galaxies are given the symbol (rs). [16] Spiral arms. As in Hubble’s original scheme, spiral galaxies are assigned to a class based primarily on the tightness of their spiral arms.
It can be thought of as a "clumpiness" factor - the higher the value for some distance scale, the more "clumpy" the universe is at that distance scale. From every pair in a distribution of galaxies, the two-point correlation function is calculated by counting the number of pairs that are separated by distances in various bins.
Spiral galaxies are quite thin, dense, and rotate relatively fast, while the stars in elliptical galaxies have randomly oriented orbits. The majority of giant galaxies contain a supermassive black hole in their centers, ranging in mass from millions to billions of times the mass of the Sun. The black hole mass is tied to the host galaxy bulge ...
The Milky Way is an example of a spiral galaxy. It is estimated that there are between 200 billion [7] (2 × 10 11) to 2 trillion [8] galaxies in the observable universe. Most galaxies are 1,000 to 100,000 parsecs in diameter (approximately 3,000 to 300,000 light years) and
The cD-type is a classification in the Yerkes galaxy classification scheme, one of two Yerkes classifications still in common use, along with D-type. [8] The "c" in "cD" refers to the fact that the galaxies are very large, hence the adjective supergiant, while the "D" refers to the fact that the galaxies appear diffuse. [9]
The physical universe is defined as all of space and time [a] (collectively referred to as spacetime) and their contents. [10] Such contents comprise all of energy in its various forms, including electromagnetic radiation and matter, and therefore planets, moons, stars, galaxies, and the contents of intergalactic space.
A key interest in Extragalactic Astronomy is the study of how galaxies behave and interact through the universe. Astronomer's methodologies depend — from theoretical to observation based methods. NGC 2207 (the bigger galaxy to the left) and IC 2163 (the smaller galaxy to the right) as seen by the Hubble Space Telescope. Galaxies form in ...