The HD 215152 system

HD 215152 is a K3V orange dwarf in Aquarius, 70.19 ly away, with 4 known planets. Their orbits run from 0.0576 to 0.154 AU. All of them were detected by radial velocity.

28 AUG 2026 08:57 UTC

ACROSS

Seen from above the orbital plane, on a linear scale — the star is at a focus of every ellipse rather than in the middle of it, and on any other radial scale these would stop being ellipses. This is not the view from Earth: from here the system is edge-on, which for most of them is how they were found. The planets turn anticlockwise. 4 are drawn as a dashed circle because the archive publishes an eccentricity of exactly zero with no uncertainty around it — a fit that held the orbit circular rather than a measurement that found it so. 4 orbits are drawn without a planet on them because nothing dates them: a period says how long a lap takes and not when one began.

Distances are semi-major axes in astronomical units on a linear axis. Planet discs are on their own scale, by cube root of radius, because at the orbital scale every one of them is smaller than a pixel. The band is where a planet would receive between 0.53 and 1.1 times the sunlight Earth does, computed from the star’s luminosity and nothing else — it is a distance, not a verdict about any world in it.

[

THE PLANETS

] 4, INNERMOST FIRST

PLANET

ORBIT (AU)

PERIOD

RADIUS

MASS

EQUILIBRIUM T

[

WHAT THIS PAGE IS

] AND IS NOT

Every figure here is the NASA Exoplanet Archive’s composite parameter for that planet — one consistent set per world, not the best number for each column from a different paper. Semi-major axes are orbits about the star, not distances from Earth; the system as a whole is 70.19 ly away.

The band on the diagram is a distance and not a verdict. It is where a planet would receive between 0.53 and 1.1 times the sunlight Earth does, from a luminosity of 0.23 L☉. It says nothing about whether anything in it has an atmosphere, water, a magnetic field or a stable star.

Discovery order and orbital order are different things. Planets are lettered b, c, d in the order they were found, and this table is ordered by semi-major axis instead — which is why the letters on many of these pages are out of sequence.

The plan view at the top puts the planets where their published elements say they are, and there is one thing it deliberately cannot show: which way the whole system is tilted. The inclinations the archive publishes are measured against the plane of the sky, one per planet, and there is no longitude of the ascending node for any planet in this catalogue — so the view perpendicular to the orbits is the only one that needs nothing invented. What that costs is the view from Earth, which for most of these systems is very nearly edge-on, because a system seen any other way does not transit and would never have been found.