Alpha Centauri: Unveiling the Secrets of Our Nearest Stellar Neighbor (Astronomers' Universe)
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As our closest stellar companion and composed of two Sun-like stars and a third small dwarf star, Alpha Centauri is an ideal testing ground of astrophysical models and has played a central role in the history and development of modern astronomy―from the first guesses at stellar distances to understanding how our own star, the Sun, might have evolved. It is also the host of the nearest known exoplanet, an ultra-hot, Earth-like planet recently discovered.
Just 4.4 light years away Alpha Centauri is also the most obvious target for humanity’s first directed interstellar space probe. Such a mission could reveal the small-scale structure of a new planetary system and also represent the first step in what must surely be humanity’s greatest future adventure―exploration of the Milky Way Galaxy itself.
For all of its closeness, α Centauri continues to tantalize astronomers with many unresolved mysteries, such as how did it form, how many planets does it contain and where are they, and how might we view its extensive panorama directly?
In this book we move from the study of individual stars to the study of our Solar System and our nearby galactic neighborhood. On the way we will review the rapidly developing fields of exoplanet formation and detection.
Humanity’s technological skills, no spacecraft has to date reached interstellar space. 2 Voyager 1 , the current long-distance record holder launched in 1977, is now some 18.5 billion kilometers away from the Sun, but this is a minuscule step compared to the 7.4 trillion kilometers outer radius of the Oort Cloud boundary – the zone that gravitationally separates out the Solar System, our current stomping ground, from the rest of the galaxy. Ever hungry for adventure and raging against the.
≈ 107 K, that is, collapse stops once the central temperature is high enough for fusion reactions to begin. With Fig. 2.2 as our guide, it is through the onset of nuclear reactions that a star is able to tap into an internal energy source. The energy generated by the hydrogen fusion reactions then exactly balances the energy lost into space at a star’s surface (its observed luminosity). By having a hot interior, a star sets up a pressure gradient, with high pressure at the center and low.
Might orbit other stars is far from being a new one. Indeed, it is an ancient idea. The atomistic philosophy of Epicurus (341–270 B.C.) supposed, in fact, that there were an infinite number of stars and planets, and specifically an infinite number of Earths. Much later in history, the scripturally misguided polymath Giordano Bruno (1548–1600) reasoned that not only did it make philosophical sense that the universe was infinite in extent, but that every star in the universe should also have an.
From their parent Sun-like stars are discovered. This discovery, of course, will open up all manner of exciting opportunities to investigate the development of planetary atmospheres and possibly the evolution of life elsewhere in the galaxy. In terms of possibly detecting planetary transits within the α Cen AB binary, the transit probabilities for us will be similar to those for an alien observer detecting Earth in orbit around the Sun. Formally, using Table 2.2 as our guide, the probabilities.
Their forward to the final Project Daedalus report (published in 1978 – Ref.41) Alan Bond and Anthony Martin commented that the program was intended as a proof of feasibility exercise, “to establish whether any form of interstellar space flight could be discussed, in sensible terms, within established science and technology.” We are now at a crossroads. The proof-of-concept studies all seemingly indicate that on a timescale of perhaps a century from the present un-manned interstellar space.