ANALOG "Alternate View" columnist, and author of TWISTOR,
(click on the "Document" button for more details).
This stack, copyright 1988 by J. G. Cramer, is semi-freeware. It may be freely used, duplicated, and passed on, but may NOT be modified, except to correct bugs and to include minor improvements. In particular, the commerical "message" about my book TWISTOR must be included in all legal copies of this stack.
WARNING: This stack, in its pristine state, occupies 85K. However, it will grow to 88-90K when the plot and/or sort features are used. Be sure enough disk space is available to accomodate this increase in size.
The Sol's Neighbors stack contains organized information about the stars that lie withing 16 light years of the Solar System, the Earth's nearest stellar neighbors. These stars, though of not much astronomical interest, are important to our future because they are the star systems that will undoubtedly be explored first when our race finally ventures beyond the bounds of our own planetary system.
ΓÇó The control eight buttons along the bottom edge of this card are used, respectively, for: [Returning to Home stack] , [Reading the Developer's Message] , [Getting the Location Plot Screen] , [Going forward or back one card] , [Getting the Sorting Control Screen] , [Showing all cards in the stack in rapid succession] , and [Getting this Help Screen] . Click on a button to perform the function. On most cards there is an "Up-Arrow" button that will return you to the title screen.
ΓÇó On the individual star cards, the right and left arrow buttons allow movement forward or backward by one card. The two oblong buttons along the bottom edge are used, respectively: (1) For calculating the distance from the first star selected by clicking the button to the second star selected by clicking the button again, and (2) For plotting the location of the present star on the Location Plot Screen. Such location plots can be accumulated for several stars by using the "Return" button rather than the "Erase" button on the location screen.
The data provided on the individual star cards include the following:
ΓÇó Names of the stars, using the arcane designations of astronomers, which may refer to the location of the star in a constallation (e.g., Epsilon Eridani) or to a listing in a star catalog (e.g., Groombridge 34 A).
ΓÇó Alpha and Delta are the astronomical polar coordinate angles (the hour angle and the right ascention) of the star on the celestial sphere, as seen from the Earth. By convention the angle Alpha is given in hours and minutes rather than degrees.
ΓÇó Parallax is the half-angle of the angular change observed in the star's position as the Earth moves from one side of its yearly orbit to the other side. Parallax is measured in units of arc seconds, or 1/3600 of a degree.
ΓÇó Distance, given in both light years and parsecs, is the distance of the star from the sun. The parsec unit (= 3.261633 light years) is preferred by astronomers because it can be directly related to the parallax measurements used to find the distance of relatively close stars. Another distance unit frequently used is the AU (or astonmomical unit). The AU is the average radius of the Earth's orbit, or the mean distance from the Earth to the Sun. (1 light year = 6.324 x 10^4 AU)
ΓÇó Spectral Class is an astronomical designation which classifies the color (or spectral content) of the light from the star. The letters that specify the range of spectral classes, going from the hottest or bluest stars to the coolest or reddest stars, is given by the sequence "OBAFGKM" (Mnemonic: Oh Be A Fine Girl, Kiss Me!) Within this classification a number from 0 to 9 specifies where in the temperature range the particular star lies. For example an O-zero star at the top of the range (there are none known) would have a temperature of 83,300 K, while an M-9 star at the bottom of the range would have a temperature of 2,500 K. The designation "wd" indicates a white dwarf, which is taken here to have a temperature of 32,000 K.
ΓÇó Proper Motion is the change in arc angle per year by which the star is observed to move on the celestial sphere due to its tangential velocity relative to the Sun. Typical proper motions are a small fraction of an arc-second per year, but Barnard's Star has a very large proper motion of 10.3"/year.
ΓÇó Visual magnitude is the realtive brightness of the star as it appears in the night sky. The mangitude is represented on a logarithnmic scale, with the stars of largest magnitude being the dimmest while those with smallest magnitude are the brightest. The visual magnitude depends both on the luminosity (energy output) of the star and on the inverse square of its distance from us.
ΓÇó Luminosity is the energy output of the star, relative to the energy output of Sol. The absolute energy output of our sun is 3.827 x 10^26 watts.
ΓÇó Surface Temperature is the temperature of the stars surface, as estimated from its spectral class. It is measured in units of degrees Kelvin (K), which is the number of Celsius degrees above absolute zero (0 K). Absolute zero is -273 K.
ΓÇó Radius is the distance from the center of the star to its surface, as estimated (see formulas) from its temperature and luminosity. Here the radius is given relative to the radius of our sun, so that a star with the same radius as Sol would have a relative radius of 1.0. The radius of Sol is 6.96 x 10^8 meters.
ΓÇó Mass is the mass of the star, as estimated from its surface temperature and luminosity (see formulas). Here it is given relative to the mass of our sun,so that a star with the same mass as Sol would have a relative mass of 1.0. The mass of Sol is 5.9742 x 10^30 kg.
ΓÇó Density is the mass per unit volume of the star, as calculated from the mass and radius above, using a scale where the density of Sol is 1.0. The actual density of Sol is 4.23 gm/cm^3 . (Note that water has a density of 1 gm/cm^3).
ΓÇó E-orbit Radius is the orbital radius at which an earth-like planet would haveto be located in order to receive the same amount of light energy from its star as does the Earth in its orbit around the Sun. For very cool stars most of this light energy would lie in the infra-red. For white dward stars and large hot stars, a significant fraction of the light energy would lie in the ultra-violet.
ΓÇó E-orbit Period is the orbital period of a planet that was in this E-orbit. In other words, the length of a year on such a world.
ΓÇó Pictorial displays:
ΓÇó Star and E-orbit: A white disc shows the size of the star relative to that of our own Sun, which is represented on th "Sol" card as a disc about 2 cm in diameter. Larger and smaller stars are represented by proportionatley larger and smaller discs, down to single pixel size. Also shown is a white 3:1 ellipse (not to scale) indicating the relative orbital radius of an Earth-like planet, that it, the orbit at which a planet would receive the same quantity of light energy per unit area that is received by the Earth in its orbit around the Sun. For very large stars (Sirius, Procyon A), this orbit is so large as to be off the diagram. For very small stars it is so small as to be indistinguishable from the star itself. It should be emphasized that the ellipse is NOT on the same scale as the solar disc and is a view of a circular orbit from about 20 degrees above the orbital plane. A true-scale drawing showing the sun as a 2 cm diameter disk would require a proportional radius for the Earth's orbit of about 2.14 meters, or well off the Macintosh screen.
ΓÇó E-view of Star: A white disc shows the relative size of the star as it would appear from a planet in an E-orbit, using a scale such that an Earth-view of our Sun is represented as a 1 cm diameter white disc. Note that the smaller and dimmer stars would actually appear larger in the sky, while the larger and hotter stars would appear smaller. The exception to this is the white dwarf stars, which will be very small and bright. (Beware of eye damage to observers!)
ΓÇó Location Plot Screen: A perspective diagram shows the location of the selected star with respect to the equitorial plane of the celestial sphere (also the Earth's equarorial plane). A square 32 light years on a side is shown, with our sun located at its center. The position of each star is plotted as a solid horizontal (in plane), vertical (perpendicular distance above or below plane), and a dotted radius vector from Sol to the star of interest. Plots of several stars may be accumulated by using the "Return" button rather than the "Erase" button when leaving the Plot Screen.
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AND NOW ... A WORD FROM THE STACK DEVELOPER
John G. Cramer, author of TWISTOR
Hello. I'm John Cramer. I wrote this stack, and I'm circulating it as semi-freeware. It's a nice stack, as I'm sure you'll agree, but, frankly, it's a medium for getting your attention long enough to tell you about my first novel, TWISTOR, which is being published in hardcover in March of 1989 by William Morrow & Co., Inc. New writers are advised to "write about what you know." Well, I know physics. I'm a Professor of Physics at the University of Washington in Seattle, where I teach and do research. I also write a bi-monthly science column, "The Alternate View", for ANALOG magazine.
TWISTOR is set at my university and describes the process of scientific discovery -- its difficulty, its excitement, its importance, its impact. It's about Vickie, a graduate student, and David, a postdoc, working together on what seems to be fairly standard physics research until they discover an unexpected new phenomenon, the Twistor Effect. We follow the Twistor Effect from its accidental discovery through to full understanding of its implications, which takes David right out of this universe and into another one.
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I wrote TWISTOR because it's the kind of hard science fiction story I enjoy reading, the kind I always search for in the SF sections of bookstores and libraries. It's perhaps obvious that I should like what I write . However, some of the foremost writers of the science fiction field have recently read TWISTOR. You may be interested in what they have to say about it:
"Finally, the most exciting novel about the cutting edge of physics since TIMESCAPE. TWISTOR takes you into the lab and through the world of far-out theory, all in a swooping story of adventure."
-- David Brin
"A fine hard-science fiction thriller, very enjoyable. TWISTOR is an auspicious debut for Dr. John Cramer."
-- Greg Bear
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"TWISTOR is a rare blend of high imagination and fun by a writer who understands how research really works, both on the scientific and the human levels. It made me feel as if I were back in the lab myself -- and glad to be there."
-- Stanley Schmidt
"John Cramer's TWISTOR is a wonderful romp through the several universes of real science, from the thin abstraction of particle theory to the grubby, greasy, problem-plagued experimental laboratory, and on to the intricacies of departmental politics and the pitfalls of institutional funding. Before Cramer has finished telling his ingenious tale, TWISTOR has taken us right out of this world into a plausible universe next door. The ideas are as startlingly original as anything in the work of Robert Forward or James P. Hogan, with the added attraction of likeable flesh and blood characters and an order of magnitude better storytelling."
-- Paul Preuss
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"TWISTOR marks the arrival of a major new science fiction talent. John Cramer knows science, and people. He possesses to a phenomenal degree the wit, ingenuity, and soaring imagination all of us hope for; and they make TWISTOR a book no intelligent reader should miss."
-- Gene Wolfe
"True hard science fiction -- deftly done, with plenty of fine surprises."
-- Gregory Benford
But you don't have to take the word of these distinguished authors either. In March, 1989, TWISTOR will be available in hardcover in better bookstores. Pick up a copy and see for yourself. Because TWISTOR is a first novel, its press run will be fairly small. First edition/printings promise to soon become rare collector's items. So act soon, while copies are still available.
John G. Cramer
12/15/88
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"TWISTOR tells an exciting story that employs concepts even more exciting. Authors who not only know science but practice it are all too rare. John Cramer's distinguished career as a physicist enables him to give this novel a ring of authenticity, not only scientific, but human."
-- Poul Anderson
"John Cramer's first novel has fascinating extrapolation, strong characters, and accelerating suspense. Once you've read TWISTOR, Cramer will be on your Must-Read list."
-- F. M. Busby
"John Cramer's first science fiction novel has two great things going for it. His scientific background includes degrees in physics, and he has been teaching the subject at university level. And somehow he also learned to intertwine his far-reaching knowledge with a wonderful, exciting story. TWISTOR may well be the best SF novel of the year."
