From: fungus@amongus.com.invalid   
      
   From the «Tatooine» department:   
   Title: Why Are Tatooine Planets Rare? Blame General Relativity   
   Author: admin@soylentnews.org   
   Date: Tue, 24 Feb 2026 02:37:00 +0000   
   Link: https://soylentnews.org/article.pl?sid=26/02/23/0050217&from=rss   
      
   hubie[1] writes:   
      
   Astronomers have found thousands of exoplanets around single stars, but   
   few around binary stars — even though both types of stars are equally   
   common. Physicists can now explain the dearth[2]:   
      
   Of the more than 4,500 stars known to have planets, one puzzling   
   statistic stands out. Even though nearly all stars are expected to   
   have planets and most stars form in pairs, planets that orbit both   
   stars in a pair are rare.   
      
   Of the more than 6,000 extrasolar planets, or exoplanets, confirmed   
   to date — most of them found by NASA's Kepler Space Telescope and the   
   Transiting Exoplanet Survey Satellite (TESS) — only 14 are observed   
   to orbit binary stars. There should be hundreds. Where are all the   
   planets with two suns, like Tatooine in Star Wars?   
      
   Astrophysicists at the University of California, Berkeley, and the   
   American University of Beirut have now proposed a reason for this   
   dearth of circumbinary exoplanets — and Einstein's general theory of   
   relativity is to blame.   
      
   In most binary star systems, the stars have similar but not identical   
   masses and orbit one another in an egg-shaped or elliptical orbit. If   
   a planet is orbiting the pair of stars, the gravitational tugs from   
   the stars make the planet's orbit precess, meaning the orbital axis   
   rotates similar to the way the axis of a spinning top rotates or   
   precesses in Earth's gravity.   
      
   The orbit of the binary stars also precesses, but mainly because of   
   general relativity. Over time, tidal interactions between the binary   
   pair shrink the orbit, which has two effects: The precession rate of   
   the stars increases, but the precession rate of the planet slows.   
   When the two precession rates match, or resonate, the planet's orbit   
   becomes wildly elongated, taking it farther from the star but also   
   nearer at its closest approach.   
      
   "Two things can happen: Either the planet gets very, very close to   
   the binary, suffering tidal disruption or being engulfed by one of   
   the stars, or its orbit gets significantly perturbed by the binary to   
   be eventually ejected from the system," said Mohammad Farhat, a   
   Miller Postdoctoral Fellow at UC Berkeley and first author of the   
   paper. "In both cases, you get rid of the planet."   
      
   That doesn't mean that binary stars don't have planets, he cautioned.   
   But the only ones that survive this process are too far from the   
   stars for us to detect with transit techniques used by Kepler and   
   TESS.   
      
   "There are surely planets out there. It's just that they are   
   difficult to detect with current instruments," said co-author Jihad   
   Touma, a physics professor at the American University of Beirut.   
      
   [...] Farhat points out that binaries have an instability zone around   
   them in which no planet can survive. Within that zone, the three-body   
   interactions between the two stars and the planet either expel the   
   planet from the system or pull it close enough to merge with or be   
   shredded by the stars. Peculiarly, 12 of the 14 known transiting   
   exoplanets around tight binaries are just beyond the edge of the   
   instability zone, where they apparently migrated from farther away,   
   since planets would have a hard time forming there.   
      
   "Planets form from the bottom up, by sticking small-scale   
   planetesimals together. But forming a planet at the edge of the   
   instability zone would be like trying to stick snowflakes together in   
   a hurricane," he said.   
      
   Read more of this story[3] at SoylentNews.   
      
   Links:   
   [1]: https://soylentnews.org/~hubie/ (link)   
   [2]: https://news.berkeley.edu/2026/01/30/why-are-tatooine-plane   
   s-rare-blame-general-relativity/ (link)   
   [3]: https://soylentnews.org/article.pl?sid=26/02/23/0050217&from=rss (link)   
      
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