We study the possibility that hot Jupiters are formed through the secular gravitational interactions between two planets in eccentric orbits with relatively low mutual inclinations (≲20^∘) and friction due to tides raised on the planet by the host star. We term this migration mechanism Coplanar High-eccentricity Migration because, like disk migration, it allows for migration to occur on the same plane in which the planets formed. Coplanar High-eccentricity Migration can operate from the

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... g typical initial configurations: (i) inner planet in a circular orbit and the outer planet with an eccentricity ≳0.67 for m_ in/m_ out(a_ in/a_ out)^1/2≲0.3; (ii) two eccentric (≳0.5) orbits for m_ in/m_ out(a_ in/a_ out)^1/2≲0.16. A population synthesis study of hierarchical systems of two giant planets using the observed eccentricity distribution of giant planets shows that Coplanar High-eccentricity Migration produces hot Jupiters with low stellar obliquities (≲30^∘), with a semi-major axis distribution that matches the observations, and at a rate that can account for their observed occurrence. A different mechanism is needed to create large obliquity hot Jupiters, either a different migration channel or a mechanism that tilts the star or the proto-planetary disk. Coplanar High-eccentricity Migration predicts that hot Jupiters should have distant (a≳5 AU) and massive (most likely ∼1-3 more massive than the hot Jupiter) companions with relatively low mutual inclinations (≲ 20^∘) and moderately high eccentricities (e∼0.2-0.5)