In the context of the Milky Way as a whole, Sgr A* is considered to be the very center of the Galaxy. In the Milky Way we have a central black hole that is 4 million times the mass of the Sun. (Think of Kepler’s laws.) The stellar density (that is, the number of stars per unit volume) is greatest in the galactic nucleus, at the center of the bulge. Spiral arms run through the disk, and a straight “bar” may or may not be present in the middle. Galaxies, an international, peer-reviewed Open Access journal. Since observations of galaxy rotation do not match the distribution expected from application of Kepler's laws, they do not match the distribution of luminous matter. Clearly the supernova explosion of one star could never produce a single black hole with a mass so large, so this object must have formed in a different manner. Sgr A* is one example of a class of objects called Super-Massive Black Holes, or SMBHs. Using 3.6-μm data from 2112 galaxies, we show that, contrary to widely held expectations of a continuous steep decline, radial surface brightness profiles of galaxies tend to flatten and form extended plateaus beyond 27–28 mag AB /arcsec².

Michel Mayor and Didier Queloz of the Geneva Observatory (Figure 21.17) used this technique to find a planet orbiting a star resembling our Sun called 51 Pegasi, about 40 light-years away.

The stars in a galaxy are always moving, but the sheer number of them means the galaxy’s overall mass distribution hardly changes with time.2 To a The first successful use of the Doppler effect to find a planet around another star was in 1995. The toy model suggests that the combined mass of the two big spiral galaxies is around 5 x 10 12 solar masses. In fact, that’s a rather wimpy one. Spiral galaxies contain stars, gas, and dust that is mostly confined to a thin, rotating disk, although some of the mass may lie in a central bulge. To escape, you need to make a map of the cloud. But within this general description, spiral galaxies can exhibit quite a variety of shapes, as illustrated in Figure 24.2. Shapley used the positions of globular clusters to determine the location of the galactic center. 205 Exercises: The Milky Way Galaxy Collaborative Group Activities. Fact: The flat rotation curves of spiral galaxies do not show the characteristic drop-off that Kepler’s 3rd predicts. Could he have used …

You are captured by space aliens, who take you inside a complex cloud of interstellar gas, dust, and a few newly formed stars. Figure 24.2 Variation in shape among different spiral galaxies. Why? It seems that you are asking a question to which you have found an answer in Philosophy Unscrambles Dark Matter. Chapter 7 Extended Mass Distributions: Spiral Galaxies There is much to say about galaxies,1 but with our current theme we focus on motion and mass.

This implies that spiral galaxies contain large amounts of dark matter or, in alternative, the existence of … Elliptical galaxies contain mostly stars (little gas or dust) in a smooth, featureless, ellipsoidal distribution of light. we can apply Kepler's Laws or a simple numerical integration to chart the motion of the two galaxies as a function of time in the past. The Kepler space telescope is a retired space telescope launched by NASA to discover Earth-size planets orbiting other stars. At any given time, would you expect most globular clusters to be moving at high or low speeds with respect to the center of the Galaxy? Galaxies of any substantial size have a supermassive black hole in their centre.