Planets around other stars

In a series of posts earlier, I talked about the possibilities of extra-terrestrial life, and in Part Three, I mentioned our findings of planets around other stars, usually referred to as “exoplanets.” Now, in that post, I was a bit misleading in the progress we’ve made, and while not exactly incorrect in what I said (which referred to finding Earth-like planets in the Habitable Zone,) it is accurate to say that I gave the wrong impression.

So I’m correcting that now. We have found a handful of planets around other suns by direct visual observation, instead of only (as I implied) by changes in the light levels of the star itself. This is quite impressive, and shows off just how quickly our astronomical knowledge is changing – only a few years ago this was not the case, and some of the planets we know of had been seen a few years ago, but not confirmed.

Bad Astronomy has more details, most especially if you read through the comments (yes, some blogs get comments, imagine that.) We’re still finding planets by the method I mentioned, more than by direct visual observation, but it’s neat to know that we can, on occasion, actually see them directly.

Right now, only two exoplanets are considered candidates for life, Gliese 581 C and Gliese 581 D, and we have not seen those directly despite being much closer. The one that BA is talking about is far, far too young and hot, and would probably never be a candidate in its entire lifespan – it actually appears to lie somewhere in the grey area between planet and star, according to some of the comments. What I said about the proximity of the Habitable Zone still holds true, too – while you can distinctly see the planet well away from the star (it took some time to determine that it was not a faint background star that only appeared close,) it’s a tremendous distance away from the star itself, about 300 Astronomical Units. Since an AU is the mean distance between Earth and our sun, and should roughly correspond to the Habitable Zone for any star remotely like ours (this one is not, not by a long shot,) you can start getting the impression of how close the zone might be, swallowed up in the diffraction around the star itself.

There are lots of variables in observing stars, and it’s not clear if we’ll be able to see an Earth-like planet soon, or ever – one would have to be fairly close to us in astronomical terms, and we’re whittling down the candidates steadily. Considering, however, that at least three moons around planets within our own solar system (Enceladus, Europa, and Titan) may have the ability to support life in niche conditions, it may not require planets in specific zones at all. We’re still working it all out., so keep your eye on the astronomical websites, because our media sure as hell can’t get it straight.

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