![TOI-791 c: Less Dense Than Cork](https://cdn.slatesource.com/8/d/2/8d246e13-d597-4939-95a5-d66396b7abd2.webp)

# TOI-791 c: Less Dense Than Cork

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

## Ice giant around TOI-791

It is 1.15 times Jupiter's radius, closest in size to Jupiter, and 18.6 times Earth's mass, at 0.05 g/cm3, less dense than Earth. A year there lasts 232.02 days, on an orbit 2.2 times Mercury's distance from the Sun. Its equilibrium temperature is 363 K, hotter than any desert. The host star TOI-791 runs at 6294 K with 1.28 times the Sun's mass.

Radius

12.95 Earth radii

Mass

18.6 Earth masses

Equilibrium temperature

363 K (measured)

One year

232.02 days

Orbit radius

0.8630 AU

Host star

TOI-791 at 6294 K

Distance

1113 light-years

Starlight blocked

0.647% at each transit

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

The habitability checklist, honestly scored

0%

Orbits inside the computed habitable zone. No.

Dense enough to be rock rather than gas, at 0.05 g/cm3. No.

A measured mass, not just a radius. Yes.

A measured temperature rather than one derived from the star. Yes.

Any detection of an atmosphere. Not recorded in the archive.

What you get from the shadow

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

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.

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.

TOI-791 has 2 known planets. Planets in company tug on each other, and those tugs are measurable, which is how masses get pinned down without a wobble.

[NASA Exoplanet Archive: source data, including the values not used here](https://exoplanetarchive.ipac.caltech.edu/overview/TOI-791%20c?utm_source=slatesource)