You’ve probably seen these pictures of planets orbiting other stars.  They’re obviously amazingly cool, but they raise a number of questions:

1. Why does one of them look like the Eye of Sauron?

2. Are these just cool pictures, or do they represent a significant advance in science.

(Full disclosure: I stole #1 from a student.)

Part of the answer to #1 is that the people who made this picture had to choose a more-or-less arbitrary color scheme to show the image, and they happened to choose a red one.  This image is apparently taken using visible wavelengths of light, but the colors shown are”false colors.”  (Extra-geeky aside: I’m not sure, but I think they might have gone with IDL’s “red temperature” color scheme, which happens to be one I’m partial to.)

The black region in the center is where they blocked out the light from the star by putting something in front of the telescope.  If they hadn’t done this, the light from the star would have overwhelmed the faint signal from the planet.  The reddish stuff is mostly radiation from the dust surrounding the star.

What about question #2: how important is this?  This is far from my area of expertise, but I’ll give my impressions anyway.  I think it’s mostly important as a milestone on the way to future discoveries.  Even with these images, the amount that we now know about these particular systems is not all that much greater than what we already knew about the few hundred other star systems where we’ve discovered planets.  In those other systems, even though we don’t see the planets, we can often figure out quite a bit about their locations, masses, orbits, etc., by observing the planets’ effects on their host stars.

But this is still a really big deal, because it’s a step on the way to eventually learning a lot more about these planets.  If you can learn to isolate the light from the planet, as distinct from the starlight, then you can study properties of the planet that can’t be gotten by the earlier kinds of observations.  In particular, if you can take that light and pass it through a spectrometer, you can do chemistry.  You can figure out what the planet is made of, what’s in its atmosphere, etc.

Ultimately, of course, doing chemistry on planetary atmospheres might give us evidence of life out there, which would be the just about the most important bit of science I can imagine.  But even if that doesn’t happen, just being able to study the composition of planets at all will be pretty amazing.

I don’t know how big a step it is to go from the sorts of images we’ve seen this week to spectroscopy, but this is definitely a lot closer than we’ve been before.

Published by

Ted Bunn

I am chair of the physics department at the University of Richmond. In addition to teaching a variety of undergraduate physics courses, I work on a variety of research projects in cosmology, the study of the origin, structure, and evolution of the Universe. University of Richmond undergraduates are involved in all aspects of this research. If you want to know more about my research, ask me!