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Two Earth-Sized Bodies With Oxygen-Rich Atmospheres
tugfoigel writes "Astrophysicists at the University of Warwick and Kiel University have discovered two bodies the size of earth with oxygen-rich atmospheres — however, there is a disappointing snag for anyone looking for a potential home for alien life, or even a future home for ourselves. These are not planets, but are actually two unusual white dwarf stars." The objects, 220 and 400 light-years distant, are believed to be remnants of stars between 7 and 10 solar masses. Such stars, the largest that evolve to white dwarves, have been sought for years. If the stars were a little more massive they would collapse to neutron stars, or so the theory goes. Here is the paper on the arXiv.
The real historical plural of dwarf is dwarrows. Dwarves is bad grammar, but is in common enough usage that it's pointless to argue. "Dwarfs" just makes you look illiterate, as if you spelled the plural of fish as "fishs."
The preference for Dwarves instead of Dwarfs is actually fairly recent. In the foreword for The Hobbit, Tolkein comments that in English the only correct pluralisation of Dwarf is Dwarfs, but that he uses Dwarves "only when speaking of the ancient people to whom Thorin Oakenshield and his companions belonged".
So either Dwarves or Dwarfs would be correct, as both have been in common usage in living memory, but Dwarrows wouldn't exactly count as modern English.
The radius is not explicitly stated in the paper, and the estimated masses are around one solar mass, which means they are no where near earth-sized.
Wrong. WDs are *ridiculously* dense, with a rho of about 10^6 g/cm^3, so a 1M_sun WD has a volume of like 2*10^31 cubic meters, which means the radius is around 8000 kilometers. R_earth is about 6400 kilometers, so Earth is actually really useful to get an intuitive picture of how these guys look.
The cool thing about WDs is that they shrink in volume when you add mass. Which means they get denser the more mass you add. Even cooler is that lots of them are in a co-orbit with other stars in a binary system, and they steal mass from the other star, so it's not so strange to see WDs gaining mass and getting denser over time.
It turns out there is one special mass at which the electron degeneracy pressure holding the star up is not enough to fight the force of gravity pushing it inward. (This mass is about 1.4 times the mass of the sun, depending on whether the star is rotating.) At that point the thing collapses from the size of earth to about the size of a soccer ball in less than a second, generating one of the most spectacular explosions in nature. I mean this thing is blown apart at around 3% of the speed of light and is 5 billion times brighter than the sun.
This is called a "type Ia supernova" -- a pretty boring name for what is, technically speaking, the awesomest thing in the universe.