For those curious, 9.7 g/cm^3 would roughly match the densities of Thulium (9.321), Bismuth (9.807), Moscovium (>9.807), Lutetium (9.84), or Lawrencium (>9.84). Several of those are short-lived radioactive elements, however.<p>Going up the scale slightly are Actinium (10.07), Molybdenum (10.22), and Silver (10.501).<p>My suspicion is that there's possibly a core of Lead (11.342) or Thorium (11.72) (both fairly abundant on Earth, and stable), though Mercury (13.5336) and Tungsten (19.25) give some interesting possibilities, surrounded by a crust (or ocean) of less-dense materials.<p>Oh, and surface temperature is ~1,200°C.<p>Quite a conundrum.<p>Elements listed by density (at standard temperature & pressure: 100 kPa & 0°C): <<a href="https://www.thoughtco.com/elements-listed-by-density-606528" rel="nofollow noreferrer">https://www.thoughtco.com/elements-listed-by-density-606528</a>>
From the article:<p>> There's nothing physically impossible about either of those potential formation mechanisms, but both require a series of unlikely events. The Universe is big, and those things probably happen somewhere…<p>The universe has so many galaxies, with so many stars, with so many planets, that the odds practically demand these outlier results. We should stop being surprised at them.<p>Astronomers and astrophysicists need a new law of discovery, something like this: “Every possible astrophysical body already exists somewhere in the universe.”