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The Star-Spectroscope of the Lick Observatory in 1898. Designed by James Keeler and constructed by John Brashear.. Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light, ultraviolet, X-ray, infrared and radio waves that radiate from stars and other celestial objects.
For the giant planets, the "radius" is defined as the distance from the center at which the atmosphere reaches 1 bar of atmospheric pressure. [11] Because Sedna and 2002 MS 4 have no known moons, directly determining their mass is impossible without sending a probe (estimated to be from 1.7x10 21 to 6.1×10 21 kg for Sedna [12]).
The mass of the observable universe is often quoted as 10 53 kg. [48] In this context, mass refers to ordinary (baryonic) matter and includes the interstellar medium (ISM) and the intergalactic medium (IGM). However, it excludes dark matter and dark energy. This quoted value for the mass of ordinary matter in the universe can be estimated based ...
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.
Discovered through gamma-ray burst mapping. Largest-known regular formation in the observable universe. [8] Huge-LQG (2012–2013) 4,000,000,000 [9] [10] [11] Decoupling of 73 quasars. Largest-known large quasar group and the first structure found to exceed 3 billion light-years. "Giant Arc" (2021) 3,300,000,000 [12] Located 9.2 billion light ...
A successful large-scale simulation of the evolution of galaxies, with results consistent with what is actually seen by astronomers in the night sky, provides evidence that the theoretical underpinnings of the models employed, i.e., the supercomputer implementations ΛCDM, are sound bases for understanding galactic dynamics and the history of the universe, and opens avenues to further research.
Within a given supercluster, most galaxy motions will be directed inward, toward the center of mass. This gravitational focal point, in the case of Laniakea, is called the Great Attractor , and influences the motions of the Local Group of galaxies, where the Milky Way galaxy resides, and all others throughout the supercluster.
The second possibility is the core accretion model, which is also known as the nucleated instability model. [22] [34] The latter scenario is thought to be the most promising one, because it can explain the formation of the giant planets in relatively low-mass disks (less than 0.1 M ☉). [34]