description HD 219134 d Overview
HD 219134 d is an extrasolar planet orbiting the nearby K-type star HD 219134 in the constellation Cassiopeia, about 21 light-years from Earth. It was identified through radial-velocity measurements and has a minimum mass in the Neptune range, which is why it is commonly classified as a mini-Neptune or Neptune-mass planet. Unlike the system's inner planet b, it has not been established as a transiting planet, so its radius and bulk composition are less directly constrained.
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Which star does HD 219134 d orbit?
HD 219134 d orbits the nearby K-type star HD 219134 in the constellation Cassiopeia. The system is about 21 light-years from Earth. ([NASA Science](https://science.nasa.gov/exoplanet-catalog/hd-219134-d/))
How was HD 219134 d detected?
It was detected through the radial-velocity method, which measures the star's motion caused by an orbiting planet. The planet takes about 46.9 days to complete an orbit and has a minimum mass in the Neptune range.
What is the estimated mass of HD 219134 d?
A commonly cited solution gives it a minimum mass of about 16 Earth masses. That is why it is often described as a Neptune-mass or likely ice-giant planet rather than an Earth-sized rocky world.
Does HD 219134 d transit its star?
The standard catalog lists HD 219134 d as a radial-velocity planet without a confirmed transit. Because its orbit is not seen crossing the star, astronomers report a minimum mass rather than a directly measured radius.
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