500 exoplanets to scale in a single image

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This is really pretty, but it’s pure fiction. We can generally detect the mass of these planets, but there’s no linear relationship between mass and radius, and no clues about colors at all.


may contain enormous quantities of halite

so… rock salt? Genuinely curious why this is noteworthy. Is it just that we think we know something at all about the planets?

I thought we were detecting planets based on how much light they obscure from the stars they orbit, which would be a function of size, rather than mass, I thought?

That’s one way. Star wobble is the other. No idea which is more common.

I’m back from wikipedia. Apparently 2014 was a good year for the transit method (shown in green on this chart of planets discovered per year)

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<cough> …(to be taken in) “large quantities”…


Back to Wikipedia, do your homework: In 2014 a huge batch of Kepler results was published.

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Here is a little insider tip on organizing your planets. First, put the big ones in your bucket, then the little ones, that way the little ones fill in all the spaces between the big ones. You can also use cardboard boxes or grocery bags. So handy for show and tell.


IIRC, measurements come from the light that’s occluded as well as how much the star is gravitationally nudged by the circling planet(s). And I think that scientists are able to figure out the planet’s mass from how much or how little the star is nudged (via the redshift of the star in question).

And again, humans learn that not only does the sun not rotate around Earth, and that our solar system isn’t the center of our galaxy (and certainly not the center of the universe), but that we may be just one more little stone circling just one more little speck of light.

Redshift actually only gives m sin i, which serves as a minimum possible value for the mass m but doesn’t actually let you figure out what it is until you know the orbital inclination i. That has to be found through some other method, like resolving the motion of the star relative to the background, which is harder to do.

Unfortunately there’s been lots of news releases and even papers that confuse the m sin i values with actual masses, and it hasn’t all been sorted out yet. You can bet at least some of the larger planets detected this way are actually brown dwarfs in orbits relatively perpendicular to us.


I hope that with the JWST and Kepler’s successor, TESS, that we’ll get that much closer to good numbers, although I think it’s safe to say that given what we’ve found in such a small search area we can expect to find a hell of a lot of planets, habitable or not.


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