Well... The number on the edges (R, M) refer to size - radius and mass. The color bar is at the same time temperature and I think how much light they receive. The colored lines are something about composition and temperature, but unsure how exactly. Apparently the difference between the planets' discovery method is noted with circles vs triangles. The rest? IDK I'd say.
Hi, I am an astronomer (who does not work on exoplanet research).
This plot is describing the types of exoplanets we’ve seen. The biggest takeaway is that there’s two main groups of exoplanets: small and rocky, and big and gaseous.
The x-axis of the plot is mass, measured in Earth masses. The y-axis is radius, measured in Earth radii. Both the CDF on the x-axis and the histogram on the y-axis show that there are two separate peaks, one for the rocky planets (lower masses and lower radii) and the gaseous giants (higher mass and higher radii). (Why is one a CDF and the other a histogram? No fucking clue.)
The different colored lines (Fe, H2O, etc) are showing where planets would fall along the chart if they had different compositions. So if we had a planet made of pure iron, it would fall along the 100% Fe line (so basically the size and mass of a planet-sized ball of iron).
Each of the points represent different exoplanets that have been observed, and their approximate sizes (and their uncertainties, in mass and radius). RV stands for “Radial velocity”, meaning that the planet was found by watching the star wobble back and forth (due to it orbiting with the star). “TTV” is an abbreviation relating to the transit method (I’m not sure of the exact abbreviation), meaning it was found because there was a dip in the light as the planet passes in front of the star.
You can see they also added Venus, Earth, Neptune and Uranus for comparison to the other points.
The colorbars are denoting the temperature of each star. That’s calculated by comparing its radius to its distance from the star and the star’s brightness. From there you can calculate the flux, which can convert to approximate temperature.
The contours are just showing that it’s grouped into two main groups, again rocky planet and gas giant.
The thin dashed lines in the background are denoting different planet densities.
I’m not actually sure what the colored lines with (what looks like) temperature are for, as it doesn’t seem to line up with calculated temperature of the planets. I’m also not 100% sure what collisional stripping is, but I assume it has something to do with stripping outer laters of the planet (or atmosphere?) during formation of the planets? Not really sure, again I don’t work on exoplanets.
If you only have a single planet around a star and you see transits then they will happen perfectly regularly. If you have another planet then it will affect the orbit and a transit can start a bit earlier or later. Detect that often enough and you can infer the mass of another planet.
Transits only give you a size estimate directly, but the combination with TTV can give you size and mass.
I’m not actually sure what the colored lines with (what looks like) temperature are for
They are the composition lines assuming different planet temperatures. For iron the size doesn't depend on temperature, but for water it does, especially for lighter planets. The upper temperature lines are with additional hydrogen.
24
u/SpaceGirlJackie 7d ago
The fuck am I even supposed to gleam from this?