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Scientists Find Solar System Like Ours
mlimber writes "The NYTimes has up a story about the discovery of a solar system that is analogous to ours. Of the 250 or so exoplanets found thus far, 'few of them are in systems that even faintly resemble our own. In many cases, giant Jupiter-like planets are whizzing around inside the orbit of Mercury,' whereas in this new system, 'a planet about two-thirds of the mass of Jupiter and another about 90 percent of the mass of Saturn are orbiting a reddish star about half the mass of the Sun, at about half the distances that Jupiter and Saturn circle our own Sun.' The researchers used gravitational microlensing to detect the planets, and two of the lead authors of the paper to be published in Science are amateur astronomers, one of whom describes herself as 'an ordinary New Zealand mother.'"
Because it's relative in scale to us, the star is half the size of our sun. The large gas giants are about half as far away from the star, as ours are to our star, etc., etc..
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Amateur astronomers contribute a great deal to the field. It's not necessary to have access to expensive research equipment to make useful observations of interest to the scientific community. Many comets have been discovered by amateurs, for example.
We're here and alive because Jupiter is big enough and close enough to suck up most comets and asteroids that might wipe us out, but small enough and far enough out that it doesn't suck us up. Most of the extrasolar planetary systems we've seen to date fail the second qualification.
Insolation (sunshine intensity) decreases with the square of the distance to the star. However, the relationship between star volume/mass and its radiation are more complicated than that, and TFA doesn't go into details.
Actually I think the correct term is "planetary system". A star system would be a group of stars that orbit each other.
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Being a graduate student at one of the universities involved, i did some modeling on this event (although we weren't quite up with the game, so our findings weren't used in the report).
The term 'lensing' is a bit of a misnomer, as that implies that you're looking at the source star; which is essentially a giant flashlight that allows us to probe the lens for information about it's planets.
The lens star acts to bend the light from the source, creating multiple and distorted images of it (which are too close together to resolve). Observing the sky from earth, these multiple images have the effect of increasing the net flux measured (in laymans terms, the star gets brighter).
When the lens star has planets (especially, as in this case, one close to what as known as the 'einstein ring') it causes large perturbations to the (otherwise fairly simple) lightcurve. With appropriate mathematical models and massive amounts of computing power, the parameters that give the best fitting theoretical lightcurve can be found.
Combining this with external information and a good dose of physical and statistical insight, it is possible to say to a reasonable degree of confidence (usually never 100%) that you have found such and such a system.
In reality, the astronomers who measure the data are only a very small part of the overall picture, but the media find a much better story in "amateur astronomer finds extrasolar planets" than "scientists use computer grid to minimize 10 dimensional chi^2 hypersurface" so they get all the attention.
Actually, the mass/luminosity relationship is (roughly) L~M^3.5. They never mention the exact size of the star, but if we assume it's half as massive as the sun it's luminosity is right around 9% of solar (I'm rounding a bit). Take into account you've got a factor of 4 increase in insolation by moving it to half the distance and you can see the inner planet gets something like 36% of the insolation of Jupiter. Granted, I completely made up the mass of the star, but it gives you an idea of what's going on.
And for the record I was an astronomer.
The closer star is the one with the planets. The one 21000 years provided the light however, the closer one acted like the lens. You can read this article for more information. Basically, the perfect alignment of the two stars produces a magnification of the furthermost stars light. If the intensity of the outer star is plot against time, the graph will show a hump when the stars aligned. If there is a planet around the "lens" star that is pretty far away, the planet will cause a deviation in the light intensity curve when it aligns with the stars. Thus, the planet acted as another lens in the system further magnifying the light from the furthermost star.
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From said article: Emphasis added.
In other words, the "lensing effect" of the nearer star doesn't behave, as you clearly imagine, like a cosmic telescope lens to make the distant star system more clearly visible to viewers on earth. Rather, its presence (and the presence of its attendant planets) is betrayed by the distortions they gravity introduces in the transmitted light as they pass between us and the more distant star.
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