Page 38 - Curriculum Visions Dynamic Book

For example, the radio source called Sagittarius A*, some 30,000 light-years from us, is thought to mark a black hole.
The same process powers the jets of charged particles flung from the black hole, which we can see as blue streaks in space and also the shining core that we observe as a pointlike qUasar.
Black holes are not uncommon. The closest black hole to us is within the central bulge of the Milky Way. A black hole is a natural part of a star’s formation, the star and the black hole being created as part of the life cycle of a star. Evidence for this comes from the fact that the amount of mass in a black hole is always about a fifth of 1% of the mass of the stars in the central bulge of the galaxy
it is in.
Finally, we can ask, “Are all
black holes the same?” In principle probably yes, but size does seem to matter. For example, black holes in small galaxies like the Milky Way have a small mass of just a few Suns and are relatively less powerful—not powerful enough to release radiation, for example. On the other hand, black holes developing in large galaxies can
be equivalent to a billion Suns. At this mass they send out so much radiation that they blaze for a while as the brightest objects in the cosmos—quasars.
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