Books and Clothes Make Me Hungry Inside

 Yesterday another driving lesson. Probably only one more before the test and hopefully I will be able to go about on my own (always assuming there is a car available and petrol to fuel it!). Afterward a little polishing up of my resume and then off to turn in my application at Borders - fortunately not too late. I really really hope I get the job, even if it is only christmas casual. Afterall, scott_lynch's  first novel (The Lies of Locke Lamora) is finally available in Australia and how else am I to afford it? (Also: Get to work, you!).

I did snap up a book cheap too, <em>The Last Albatross</em> by Ian Irvine. Only fair I got it from the same newsagent that tricked me into buying the sequel. Some of his fantasy novels have been omnibused now so hopefully I can snap them up soon.

Tricia

A Scattering of Notes

    Talking mostly about giant planets here, one reason they are so difficult to detect directly is the matter of contrast. The host star (parasitic connotations!) is expected to be roughly 10⁹ times brighter than the planet. That's (because this kind of explicating is easier and more fun than contributing new trickier information) a difference of one thousand million or (in US-now-standard use) a whole billion. This is in visible light. In infrared (well, wavelengths from 20 - 100 micrometres) the difference is ~10⁴. or about ten thousand times. This is because main sequence stars tend to have their peak luminosity in the visible part of the electromagnetic spectrum and decline fairly rapidly in the infrared whereas giant planets are expected to be brightest (they radiate in infrared from gravitational collapse, at least until they are done [Jupiter still does])

The paper I am looking at right now (Detection of Extrasolar Giant Planets by Marcy & Butler, 1998) uses the example of a solar type star with a Jupiter-equivalent planetary companion, seen from a distance of 10 parsecs. The star would have a visual magnitude of 5 (that would be an approximation, Sol's absolute magnitude is actually 4.8) while 'Jupiter' would have a magnitude of 27*. In this hypothetical system 'Jupiter' would have an angular separation from the star of half an arcsecond. If diffraction were the only limiting factor all we would need to resolve it is a scope with at least a 0.4 metre aperture**. Obviously since there are plans to build rather expensive scopes (especially interferometers) in space something more is required. And since it looks like I may be running out of time tonight I think I will stop here for now.

*For those who don't know, in the magnitude system astronomers us the lower the number the brighter the object, extending into negative numbers if necessary. Each five steps of magnitude represent a change in brightness of 100 times, so a magnitude 1 object is 100 times as bright as a magnitude 6 one. Or, each step is brighter/dimmer by the fifth root of one hundred (~2.512 - the scale is logarithmic, see?)

**D > 0.4 (lambda/1mu)(d/10pc)(5AU/r), with lambda being the wavelength observations happen at, d the distance to the star and r is their orbital seperation.