Measuring Black Holes
QPOs can be used to determine the mass of black holes. The technique uses a relationship between black holes and the inner part of their surrounding disks, where gas spirals inward before reaching the event horizon. The hot gas piles up near the black hole and radiates a torrent of X-rays, with an intensity that varies in a pattern that repeats itself over a nearly regular interval. This signal is the QPO. Astronomers have long suspected that a QPO’s frequency depends on the black hole’s mass. The congestion zone lies close in for small black holes, so the QPO clock ticks quickly. As black holes increase in mass, the congestion zone is pushed farther out, so the QPO clock ticks slower and slower.
Read more about this topic: Quasi-periodic Oscillation
Famous quotes containing the words measuring, black and/or holes:
“We recognize caste in dogs because we rank ourselves by the familiar dog system, a ladderlike social arrangement wherein one individual outranks all others, the next outranks all but the first, and so on down the hierarchy. But the cat system is more like a wheel, with a high-ranking cat at the hub and the others arranged around the rim, all reluctantly acknowledging the superiority of the despot but not necessarily measuring themselves against one another.”
—Elizabeth Marshall Thomas. “Strong and Sensitive Cats,” Atlantic Monthly (July 1994)
“It was common practice for me to take my children with me whenever I went shopping, out for a walk in a white neighborhood, or just felt like going about in a white world. The reason was simple enough: if a black man is alone or with other black men, he is a threat to whites. But if he is with children, then he is harmless, adorable.”
—Gerald Early (20th century)
“The danger lies in forgetting what we had. The flow between generations becomes a trickle, grandchildren tape-recording grandparents’ memories on special occasions perhaps—no casual storytelling jogged by daily life, there being no shared daily life what with migrations, exiles, diasporas, rendings, the search for work. Or there is a shared daily life riddled with holes of silence.”
—Adrienne Rich (b. 1929)