The NN Ser system

NN Ser is a WD Wolf-Rayet star in Serpens, 1682 ly away, with 2 known planets. Their orbits run from 3.39 to 5.35 AU. All of them were detected by eclipse timing variations.

28 AUG 2026 20:22 UTC

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. Every planet is at the position its published period and epoch give for the instant on the clock, to within the 8.3 minutes by which a barycentric date and a wall clock can differ. 2 orbits are drawn as an ellipse, from a measured eccentricity and a published argument of periastron.

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 PLANETS

] 2, 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 1682 ly away.

No habitable zone is drawn: it needs the star’s luminosity, and neither a luminosity nor the radius and temperature that would give one is recorded for NN Ser.

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.