Read Turn Right At Orion for Free Online

the partners: They would release their gentle grasps and swing apart. But in this case the bulges lagged far enough behind, and gravity had enough leverage: The stars just managed to swing into orbit around each other.
    Like most stars that have newly captured one another, my couple shared a graceful orbit, swinging far apart and then plunging close. When far apart, the stars seemed almost oblivious to one another—in this phase, indeed, passing stars have been known to steal other stars’ partners. But when they plunged close together, the bulges reappeared, and the stars sank deeper into one another’s gravitational influence. By now the incessant heating had inflated the stars’ atmospheres, and their gaseous envelopes had begun to mingle. The stellar nuclei, where nuclear reactions pump out energy, were still distinct, but they were rapidly being subsumed beneath the common envelope. Finally, they merged.
    According to theory, it would take another 1000 years or more for the merged star to settle down. The “new” star would become much brighter than the sum of its two progenitors, and not just because the merging process itself generates a lot of heat. The nuclear reactions that power stars are extremely sensitive to temperature (hence the term thermonuclear ), and the temperature inside a star depends on the star’s mass and size in a way that is determined
by the necessity of a balance between gravity and pressure. Thus, if the new star is double the mass of the old, it must be roughly twice as large. If it were too small, the temperature in the center would be so high that nuclear reactions would proceed at an explosive pace, the pressure would build up, and the star would expand. If it were too large, the central temperature would be so low that the nuclear reactions would fizzle out, and the star would contract. In this way, the temperature sensitivity of thermonuclear reactions provides an elegant feedback that determines the sizes of stars. But a different effect determines how bright a star is. Energy leaks out faster from a larger star than from a smaller star, because the former has more surface area and is generally more porous. As a result, more massive (and therefore larger) stars put out a lot more light than low-mass stars. A star only twice the mass of the Sun puts out about 16 times more light. The flip side is that a 2-solar-mass star has only twice the fuel supply of the Sun, so it can live only ⅛ as long. When I put the arguments together this way, it no longer seemed like such a crazy idea that the hot young stars in the Galactic Center Star Cluster might well have formed from mergers.
    My theoretical training allowed me to anticipate the future of this newly merged star, but I had no time to watch the final stages unfold. I hadn’t come here to study stars, anyway. I was searching for pure gravity, and pure gravity was to be found in one place: the big black hole at the very center of the Milky Way. But how was I to locate the Galaxy’s exact center of mass? I looked about for some secondary clues and noticed, in one direction, an especially dense concentration of stars surrounding a point of light with a strange, very blue glow. As I headed toward it, I immediately noticed that the stars around me were getting closer together. Their random motions were also speeding up: 500 hundred kilometers per second, 1000, 1500. . . . Any stellar collisions that occurred here would be far from gentle. They certainly would not lead to graceful mergers. The stars would be smashed, their debris dispersed to interstellar space. Could that be where some of the streamers of gas had come from?

    I pulled out my calculator and started taking notes on how the stellar speeds were increasing as I approached the blue glow. Atof a light-year the speed was 600 kilometers per second, atof a light-year it was 850, and so forth. Every decrease in distance by a factor of 4 brought a