![TOI-791 b: Less Dense Than Cork](https://cdn.slatesource.com/6/0/1/60106cc1-efe3-4e0e-b6ff-3586f5479309.webp)

# TOI-791 b: Less Dense Than Cork

- [Made in Slatesource](https://slatesource.com/@steph/toi-791-b-less-dense-than-cork)
- By [Steph](https://slatesource.com/@steph)
- Created on Sep 19, 2026

## Gas giant around TOI-791

It is 0.99 times Jupiter's radius, closest in size to Jupiter, and 9.5 times Earth's mass, at 0.04 g/cm3, less dense than Earth. A year there lasts 139.30 days, on an orbit 1.6 times Mercury's distance from the Sun. Its equilibrium temperature is 434 K, hotter than any desert. The host star TOI-791 runs at 6294 K with 1.28 times the Sun's mass.

Radius

11.13 Earth radii

Mass

9.5 Earth masses

Equilibrium temperature

434 K (measured)

One year

139.30 days

Orbit radius

0.6020 AU

Host star

TOI-791 at 6294 K

Distance

1113 light-years

Starlight blocked

0.478% at each transit

**0.04** g/cm3: less dense than cork

What the dip tells you

How deep the star dims fixes the planet's size relative to it.

A transit gives the radius and a separate measurement gives the mass. Having both is what makes a density, and a density is the only clue to composition at this range.

Found by Transiting Exoplanet Survey Satellite (TESS) in 2026. 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.

TOI-791 has 2 known planets. A crowded system is worth more than the sum of its planets: the timing of each transit constrains the others.

[NASA Exoplanet Archive: the full record for TOI-791 b](https://exoplanetarchive.ipac.caltech.edu/overview/TOI-791%20b?utm_source=slatesource)