2
$\begingroup$

Has Kepler (or any other survey) found an exoplanet with a similar orbit as another exoplanet around the same star?

The current IAU definition of a planet requires that "a planet has cleared its neighborhood around its orbit".

Have there been any exoplanet discoveries that bring such a definition into question?

Mathematically, is there anything stopping 2 "planets" from existing in equilibrium in a similar orbit around a single star?

$\endgroup$
  • $\begingroup$ What do you mean by "similar orbit?" $\endgroup$ – Russell Borogove Feb 22 '17 at 4:46
  • $\begingroup$ The IAU definition of "planet" is specific to objects that orbit our sun. They do not attempt to include exoplanets within this classification. $\endgroup$ – Phiteros Feb 22 '17 at 5:30
6
$\begingroup$

Two planets sharing their orbit is expected to be a rare configuration. Most configurations of 2 planets in 1 orbit are unstable. Only when one planet is in a Lagrange point of the other, are the orbits stable.

As of now (February 2017), there are no known co-orbital planets. We do know lots of smaller objects co-orbiting with planets (in our own solar system, there are thousands of Trojans in e.g. Jupiter's orbit).

There was a potential detection (Kepler-223), but on closer examination those planets were unlikely to be co-orbital.

$\endgroup$
  • $\begingroup$ Can't horseshoe orbits not be stable (at least for a long time)? $\endgroup$ – fibonatic Feb 22 '17 at 12:40
  • $\begingroup$ Sadly, according to Wikipedia, "follow-up study of the system revealed that an alternative configuration, with the four planets having orbital periods in the ratio 8:6:4:3 is better supported by the data" -- i.e. what was thought to be a co-orbital situation appears not to be. en.wikipedia.org/wiki/Kepler-223 $\endgroup$ – Russell Borogove Feb 22 '17 at 15:23
  • $\begingroup$ (Fascinating system either way -- 4 planets orbiting a star quite similar to our sun, but all four well inside Mercury's orbital distance!) $\endgroup$ – Russell Borogove Feb 22 '17 at 15:25

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.