![AU Mic b: 4-Planet System, 0.070 AU Out](https://cdn.slatesource.com/1/1/7/1170ba3d-f442-41c8-88bc-0552c21fb12c.webp)

# AU Mic b: 4-Planet System, 0.070 AU Out

- [Made in Slatesource](https://slatesource.com/@steph/au-mic-b-4-planet-system-0-070-au-out)
- By [Steph](https://slatesource.com/@steph)
- Created on Sep 19, 2026

## Ice giant around AU Mic

It is 4.79 times Earth's radius, closest in size to Uranus, and 9.0 times Earth's mass, at 0.49 g/cm3, less dense than Earth. A year there lasts 8.46 days, on an orbit 6 times closer to its star than Mercury is to the Sun. Its equilibrium temperature is 555 K, hotter than any desert. The host star AU Mic runs at 3540 K with 0.64 times the Sun's mass.

Radius

4.79 Earth radii

Mass

9.0 Earth masses

Equilibrium temperature

555 K (measured)

One year

8.46 days

Orbit radius

0.0700 AU

Host star

AU Mic at 3540 K

Distance

32 light-years

Starlight blocked

0.259% at each transit

🔭🪐📅01.01.2020 – 01.01.2021

01.01.2020AU Mic b

01.01.2020

01.01.2021AU Mic c

01.01.2021

What a crossing measures

The depth of the dip is the ratio of the two discs, so the radius follows.

AU Mic has 4 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 Transiting Exoplanet Survey Satellite (TESS) in 2020. TESS scans most of the sky in 27-day stretches, so it favours bright nearby stars and short orbits over the faint distant ones Kepler specialised in.

Two independent measurements sit behind this page: a dip in starlight for the size, and something else entirely for the mass. Together they make a density.

[NASA Exoplanet Archive: the full record for AU Mic b](https://exoplanetarchive.ipac.caltech.edu/overview/AU%20Mic%20b?utm_source=slatesource)