How to get a 100-pixel image of an Earth-like planet in another solar system

Saturday, May 01, 2010

Space.com has a great article here from yesterday on exactly what sort of telescope array will be needed to get pictures of planets at different distances. The overall tone of the article is supposed to be negative as it concludes that we won't be able to take pictures of creatures on other planets for at least a few centuries, but it really doesn't feel that way as it goes over all the exciting stages that would come before this, including the ability to take direct pictures of extrasolar planets, a subject that I wrote about just four days ago.

Here's the part that first gets into the direct imaging of an exoplanet:

The follow-up missions also could deeply investigate any exoplanets that display potential signs of life. Such missions will require much larger arrays in space — for instance, taking a 100-pixel image of a planet twice the width of Earth some 16.3 light years away would require the elements making up a space telescope array to be more than 70 km apart.
Okay, but there are 48 solar systems that are located closer than 16.3 LY, so there's plenty to observe at nearer locations, and there are larger targets too. So let's ease our burden by changing the numbers a bit.

First change 16.3 light years to 4.3 light years (Alpha Centauri).
Then change the target planet to Polyphemus from Avatar, with a diameter 8.5 times that of Earth (4.25 times the diameter of the planet mentioned in the article). That gives it a visible surface area 18 times the Earth-like planet.
Then let's assume that we don't need a 100 pixel image. 80 pixels would look like this:

So with a much more modest array we should be able to get pictures of this type from larger planets around nearby stars. I'm excited already.

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