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    Spider Star

    The human colony on the planet Argo has long explored and exploited the technology left behind by an extinct alien race. But then an archaeology team accidentally activates a terrible weapon...
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    Spider Star

    "Seldom does a storytelling talent come along as potent and fully mature as Mike Brotherton. His complex characters take you on a voyage that is both fiercely credible and astonishingly imaginative. This is Science Fiction."
    -- David Brin

    "Star Dragon is terrific fare, offering readers a fusion of hard science and grand adventure."
    -- Locus Magazine

    "Star Dragon is steeped in cosmology, the physics of interstellar travel, exobiology, artificial intelligence, bioscience. Brotherton, author of many scientific articles in refereed journals, has written a dramatic, provocative, utterly convincing hard science sf novel that includes an ironic twist that fans will love."
    -- Booklist starred review

    "Readers hungry for the thought-provoking extrapolation and rigorous technical detail of old-fashioned hard SF are sure to enjoy astronomer Brotherton's first novel."
    -- Publishers Weekly

    "Mike Brotherton, himself a trained astrophysicist, combines the technical acuity and ingenuity of Robert Forward with the ironic, postmodern stance and style of M. John Harrison. In this, his debut novel, those twin talents unite to produce a work that is involving on any number of levels. It's just about all you could ask for in a hardcore SF adventure."
    -- Paul di Fillippo, SCI-FI.COM

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Green “Stars” for Real?

June 10th, 2008

In light of the recent posts about the red M stars, as red as they’re perceived to be anyway, I wanted to bring up the issue of the non existence of green stars. A star with the appropriate temperature, not too dissimilar from that of our own Sun, has a spectrum that peaks in the green. Yet there are no green stars. Why not?

I’ve asked this from time to time as an extra credit question on introductory astronomy exams. I usually only get a few correct answers out of 120 students. It does take different thinking from the every day.
The reason there are no green stars is that those stars of the appropriate temperature also put out a lot of red light and blue light both. Emitting all colors, they appear white.

But if you look carefully enough, there are some green star-like objects. I was discussing this with a friend at the American Astronomical Society meeting last week. These greenies aren’t bright enough to be seen with the naked eye, or indeed with any telescope I’m aware of that you can use with an eyepiece. [We'll ignore the philosophical question of whether or not they're actually green if you can't see them with your own eye.]

They’re a subset of quasars/radio galaxies of redshift 3 or so, which places the strong Lyman alpha line (the strongest emission line of hydrogen) at an observed wavelength of about 500 nanometers. The light at shorter wavelengths is eaten by intergalactic absorption. The light at longer wavelengths can be much fainter than the Lyman alpha emission.

This is the best example I can find in a quick search. The color composite cannot be trusted as it is created using broad band images and the band with the Lyman alpha is a blend of blue and green. The combination of the strong Lyman alpha line and the eye’s peak efficiency both in the green should make this object appear green to the eye if seen through a large enough telescope. At least I think so. I’d love to hook up a regular color camera to a telescope (it would need to be close to a meter in diameter at least) and test this. Perhaps as an experiment this summer at Launch Pad we can try it.


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