![]() A full bathtub of neutron-star material (instead of water) would weigh as much as two Mount Everests. In a star with a core that is 1.4 to 3 times the mass of the Sun, the core collapses so completely that electrons and protons combine to form neutrons. Neutron stars are named after their composition: neutrons. Stars born with about 8 to 20 times the mass of the Sun blast most of their material into interstellar space in titanic explosions, leaving only their crushed, dense cores, called neutron stars. ![]() The megaparsec is a standard unit for measuring the distances to other galaxies. One million parsecs or 3.26 million light-years. Einstein says that mass and space are related, because mass warps space and space directs the motion of mass. Newton's law states that mass is related to force and acceleration: m = F/a. Radio wavelengths can be the size of mountains while gamma ray wavelengths are the size of an atomic nucleus. The electromagnetic spectrum range spans beyond a factor of 10^18, (1 followed by 18 zeroes) from radio to gamma ray wavelengths. The wavelengths of red and blue light differ by less than a factor of two. The familiar "rainbow" of light spans a narrow slit in the electromagnetic spectrum, from 700 nanometers (red) to 400 nanometers (blue). lightĮlectromagnetic radiation of all wavelengths and frequencies. kiloparsecĮlectromagnetic radiation of all wavelengths and frequencies. The distance separating you from the Sun weakens the mutual gravitational attraction, so as you stand on Earth's surface, Earth's gravitational pull on you is 1,650 times greater than the Sun's. For instance, the gravitational attraction between you and Earth is much greater than that between you and the Sun, even though the Sun is 333,000 times more massive than Earth. The magnitude of gravitational attraction depends directly on mass and inversely on distance squared. ![]() The most feeble of the four fundamental forces in the universe that affect all matter. A tight relationship between the masses of supermassive black holes and their surrounding bulges would support this scenario. Radiation and "winds" from the disk can stop the starbirth process by blowing away the remaining gas, leaving nothing to make stars. Some of the material falls toward the black hole, however, encircling it with a bright, hot disk. Astronomers theorize that the black hole pulls in the gas and dust that gives birth to stars in the bulge. A true bulge formed at the same time as the supermassive black hole. The bulge is a massive, densely packed region at the center of a galaxy. In essence, although it is not a physical boundary, the event horizon marks the black hole's "surface." galactic bulge Beyond this point, the escape velocity is greater than the speed of light, the ultimate speed limit. Any light or matter crossing within this boundary is doomed by the hole's gravity. event horizonĪ black hole's point of no return. Since lightspeed is the ultimate cosmic speed limit, nothing can achieve the speed needed to escape from a black hole. For a black hole, the escape velocity is greater than the speed of light. A rocket launched from Kennedy Space Center must accelerate to about 17,500 mph to enter orbit, or about 25,000 mph (11.2 km/second) to escape Earth's gravitational pull and travel to another planet. The minimum speed necessary to escape the gravitational pull of a celestial body. Subrahamanyan Chadrasekhar, at age 19 in 1930, worked out this limiting mass while on a steamship to England. Beyond this mass, the star collapses into a neutron star or black hole depending on the mass of the collapsing core. The maximum mass of a white dwarf, 1.4 solar masses. Such galaxies probably are powered by large, hot accretion disks that encircle supermassive black holes in their cores. active galaxyĪ galaxy that emits much more energy than the sum of the individual stars within it. The material within the disk may generate heat from friction the hottest accretion disks produce enormous amounts of X-rays. A swirling disk of gas and dust orbiting a star or black hole.
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