Solar Neighborhood · Kirkpatrick+ 2024 · 20-pc Census

The 20 Parsec Census

The 2,985 stars and brown dwarfs of the Kirkpatrick+ 2024 20-parsec sample, plotted in 3D Galactic coordinates. The sample is the published census, not a complete one - the same page's IMF fit implies roughly 3,000 stars and 790 brown dwarfs in this volume, so the L/T/Y tail is known to be incomplete. M dwarfs dominate the count, and it's among them that VarWISE hunts for new eclipsing binary candidates. Hover any star to see its details.

Spectral Class

F / A / B — hot92
G / K — Sun-like382
M dwarfs1,594
L / T / Y — brown dwarfs345
White dwarfs144
No spectral type428
VarWISE candidates · 44-200 pc, radius compressed452

Camera

Reference

Visible

Stars
Camera d
Frame
Class
Spectral
d
G
BP−RP
T_eff
Mass
Constellation
Figure 1 — All-Sky Map

The Sky Distribution

Every nearby star projected onto an Aitoff all-sky map in equatorial coordinates (Aitoff is neither equal-area nor conformal; the equal-area sibling is Hammer). VarWISE candidate eclipsers (gold ✦) are concentrated along the Galactic plane where variability surveys have deepest coverage.

Why this matters: The 20 pc sample shows no strong anisotropy by eye - the Sun's immediate neighbourhood looks broadly similar in every direction. No isotropy test is run on this page. VarWISE candidates, by contrast, trace the footprint of the NEOWISE + Gaia time-domain surveys. Gaps reveal regions not yet searched.
Figure 2 — Color-Magnitude Diagram

The Main Sequence, Up Close

Absolute G magnitude vs. Gaia BP − RP color for every 20 pc census object with a reliable parallax and photometry. The main sequence, white dwarf cooling track, and the brown dwarf plunge are all visible in one frame.

Reading the diagram: The hot upper-left corner holds A/F stars like Vega and Sirius. The long diagonal running toward the lower-right is where M dwarfs live — cool, dim, and the most abundant category. The white dwarf sequence sits below the main sequence (faint but blue). VarWISE candidate eclipsers fall squarely inside the M dwarf locus, consistent with their spectral identification (a CMD position is consistent with a classification; it does not confirm one).
Figure 3 — Initial Mass Function

Counting the Solar Neighborhood

Distribution of adopted initial masses for every object in the 20 pc sample. The low-mass end dominates by number — more than half the population is less than half a solar mass.

The Quadripartite Initial Mass Function

Bars: observed mass distribution of the 20 pc census. Black line: the four-segment power law ξ(M) ∝ M−α fit by Kirkpatrick et al. (2024), with α = 2.3 / 1.3 / 0.25 / 0.6 in the four mass regimes shown. Dashed segments mark the breakpoints. Vertical gold line: the hydrogen-burning limit.

Spectral-Type Breakdown

Dwarfs dominate. M dwarfs alone are a majority of cataloged objects.

Mass vs. Spectral Type

Kirkpatrick Figure 14. Mass scales almost monotonically with spectral class — reading a spectrum is the same as weighing a star.

Kirkpatrick 2024, Figure 20 — the headline result: The 20 pc mass function is a quadripartite power law. From Salpeter's classic α = 2.3 at stellar masses, the slope flattens through α = 1.3 (intermediate) down to α = 0.25 across the low-mass star / high-mass brown dwarf boundary — meaning production slows near the H-burning limit. It then steepens again to α = 0.6 deep into the brown dwarf regime. Integrating the fit: 3,002 stars and 789 brown dwarfs per 20 pc sphere → a star-to-brown-dwarf ratio of ~4:1, and an average mass per object of 0.41 M. M dwarfs dominate by number, which is exactly why VarWISE targets them for eclipsing-binary discovery.
Figure 4 — Completeness

How Complete Is the Census?

A uniform survey should grow as the volume of a sphere — the number of objects inside radius d should scale as d³. Deviations from that scaling reveal which classes are still missing from the sample at larger distances.

Distance histogram

Count per 1 pc shell. Shell volume grows as 4πr²Δr, so a complete sample should trace a parabola.

Cumulative count

N(<d) for each spectral class. The slope reveals the effective detection limit.

What to look for: M dwarfs turn over before 20 pc — at the faint end the sample becomes incomplete. Brown dwarfs (L/T/Y) are severely incomplete past ~10 pc; those are the objects Kirkpatrick and collaborators are still actively discovering with Spitzer + WISE + citizen science (Backyard Worlds). Any object we add to this plot is a real contribution to nearby-star demographics.