![TOI-2109 b: A Year In 16.1 Hours](https://cdn.slatesource.com/f/4/8/f4863d68-4ea7-422c-ba4c-7cea67a02350.webp)

# TOI-2109 b: A Year In 16.1 Hours

- [Made in Slatesource](https://slatesource.com/@steph/toi-2109-b-a-year-in-16-1-hours)
- By [Steph](https://slatesource.com/@steph)
- Created on Sep 19, 2026

## Gas giant around TOI-2109

It is 1.35 times Jupiter's radius, closest in size to Jupiter, and 1595.5 times Earth's mass. A year there lasts 16.1 hours, on an orbit 22 times closer to its star than Mercury is to the Sun. Its equilibrium temperature is 3646 K, hotter than the surface of many stars. The host star TOI-2109 runs at 6540 K with 1.45 times the Sun's mass.

**3646** K: hot enough to vaporise rock on the dayside

Radius

15.10 Earth radii

Mass

1595.5 Earth masses

Equilibrium temperature

3646 K (measured)

One year

16.1 hours

Orbit radius

0.0179 AU

Host star

TOI-2109 at 6540 K

Distance

855 light-years

Starlight blocked

0.663% at each transit

What has been measured here and what has not

0%

A measured radius. Yes.

A weight, not just a width. Yes.

A density, which decides rock or gas. No.

A semi-major axis. Yes.

A measured temperature rather than a derived one. Yes.

An eccentricity, so the orbit shape is known. No.

What the transit gives

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

Found by Transiting Exoplanet Survey Satellite (TESS) in 2021. 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.

Size from the shadow, mass from elsewhere. Most transiting planets never get the second half, and without it composition stays a guess.

[Every parameter ever published for TOI-2109 b, at the NASA Exoplanet Archive](https://exoplanetarchive.ipac.caltech.edu/overview/TOI-2109%20b?utm_source=slatesource)