My collaborators and I recently discovered a pair of exoplanet pairs. Each pair orbits a subgiant star, or a "retired A star" as I've taken to calling them. And each pair is pretty special in that the planets are interacting with eachother because they are close enough to (strongly) feel each other's gravitational tugs, in addition to the tug of their parent stars.
One of the pairs, cleverly named HD200964b and HD200964c, are extremely close to one another. Astronomers like to quantify the closeness of planets (and moons) by the ratio of their orbital periods. The HD200964 planetary system has a period ratio of 4:3---the outer planet completes 3 orbits for every 4 orbits of the inner planet. The precise ratio of periods---exactly 4 to 3, as opposed to say 4.5 to 2.7---is no accident. The only way for the planets to get along is for them to do the old 4-to-3 step, a precise set of dance moves that allows them to stay stable over long periods of time. Otherwise, one of the planets would most likely have been ejected from the system long ago. The other pair of planets orbits a star somewhat more romantically named 24 Sextanis, and they do the two-step; the outer planet completes one orbit for every 2 orbits of the inner planet.
Caltech put out a press release for the new discoveries, which got picked up by a few news outlets. Most are Astronomy-related publications, but I am in Google news!
Check it out!
The paper is on the arXiv preprint server if you'd like to get the straight dope on the system.
One of the pairs, cleverly named HD200964b and HD200964c, are extremely close to one another. Astronomers like to quantify the closeness of planets (and moons) by the ratio of their orbital periods. The HD200964 planetary system has a period ratio of 4:3---the outer planet completes 3 orbits for every 4 orbits of the inner planet. The precise ratio of periods---exactly 4 to 3, as opposed to say 4.5 to 2.7---is no accident. The only way for the planets to get along is for them to do the old 4-to-3 step, a precise set of dance moves that allows them to stay stable over long periods of time. Otherwise, one of the planets would most likely have been ejected from the system long ago. The other pair of planets orbits a star somewhat more romantically named 24 Sextanis, and they do the two-step; the outer planet completes one orbit for every 2 orbits of the inner planet.
Caltech put out a press release for the new discoveries, which got picked up by a few news outlets. Most are Astronomy-related publications, but I am in Google news!
Check it out!
The paper is on the arXiv preprint server if you'd like to get the straight dope on the system.
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