Distance To The Galactic Center and Bar
The exact distance from the Sun to the Galactic Center is notoriously uncertain. The latest estimates from geometric-based methods and standard candles yield distances to the Galactic Center between 7.6–8.7 kpc (25,000–28,000 light years). An accurate determination of the distance to the Galactic Center as established from variable stars (e.g., RR Lyrae variables) or standard candles (e.g., red clump stars) is hindered by countless effects, which include: an ambiguous reddening law; a bias for smaller values of the distance to the Galactic Center because of a preferential sampling of stars toward the near side of the Galactic bulge owing to interstellar extinction; and an uncertainty in characterizing how a mean distance to a group of variable stars found in the direction of the Galactic bulge relates to the distance to the Galactic Center.
The nature of the Galaxy's bar which extends across the Galactic Center is also actively debated, with estimates for its half-length and orientation spanning between 1–5 kpc (short or a long bar) and 10–50 degrees. Certain authors advocate that the Milky Way features two distinct bars, one nestled within the other. The bar is delineated by red-clump stars (see also red giant), however, RR Lyr variables do not trace a prominent Galactic bar. The bar may be surrounded by a ring called the "5-kpc ring" that contains a large fraction of the molecular hydrogen present in the galaxy, as well as most of the Milky Way's star formation activity. Viewed from the Andromeda Galaxy, it would be the brightest feature of our own galaxy.
Read more about this topic: Galactic Center
Famous quotes containing the words distance to, distance, galactic, center and/or bar:
“No doubt, the short distance to which you can see in the woods, and the general twilight, would at length react on the inhabitants, and make them savages. The lakes also reveal the mountains, and give ample scope and range to our thought.”
—Henry David Thoreau (1817–1862)
“Midway the lake we took on board two manly-looking middle-aged men.... I talked with one of them, telling him that I had come all this distance partly to see where the white pine, the Eastern stuff of which our houses are built, grew, but that on this and a previous excursion into another part of Maine I had found it a scarce tree; and I asked him where I must look for it. With a smile, he answered that he could hardly tell me.”
—Henry David Thoreau (1817–1862)
“In sci-fi convention, life-forms that hadn’t developed space travel were mere prehistory—horse-shoe crabs of the cosmic scene—and something of the humiliation of being stuck on a provincial planet in a galactic backwater has stayed with me ever since.”
—Barbara Ehrenreich (b. 1941)
“Everything that explains the world has in fact explained a world that does not exist, a world in which men are at the center of the human enterprise and women are at the margin “helping” them. Such a world does not exist—never has.”
—Gerda Lerner (b. 1920)
“I am of course confident that I will fulfil my tasks as a writer in all circumstances—from my grave even more successfully and more irrefutably than in my lifetime. No one can bar the road to truth, and to advance its cause I am prepared to accept even death. But may it be that repeated lessons will finally teach us not to stop the writer’s pen during his lifetime? At no time has this ennobled our history.”
—Alexander Solzhenitsyn (b. 1918)