HD 219134 b: 21 Light-Years Away
Super-earth around HD 219134
It is 1.60 times Earth's radius, closest in size to Earth, and 4.7 times Earth's mass, at 6.34 g/cm3, denser than Earth. A year there lasts 3.09 days, on an orbit 10 times closer to its star than Mercury is to the Sun. Its equilibrium temperature is 1015 K, hot enough to melt lead. The host star HD 219134 runs at 4699 K with 0.81 times the Sun's mass.
HD 219134 from the inside out
Orbit
/
Planet
Radius
1.60 Earth radii
Mass
4.7 Earth masses
Equilibrium temperature
1015 K (measured)
One year
3.09 days
Orbit radius
0.0388 AU
Host star
HD 219134 at 4699 K
Distance
21 light-years
21.3light-years: close enough to be a follow-up target
What the star's motion reveals
How hard the planet tugs, which sets a floor on how heavy it is.
This planet was found by the wobble it induces in its star, which measures mass rather than size. A radius quoted for such a planet usually comes from a later transit or from a model.
HD 219134 has 6 known planets. Planets in company tug on each other, and those tugs are measurable, which is how masses get pinned down without a wobble.
Found by Roque de los Muchachos Observatory in 2015.
