:INFO
Gas giant around Kepler-391
It is 2.50 times Earth's radius, closest in size to Neptune, and 1100.0 times Earth's mass, at 380.00 g/cm3, denser than Earth. A year there lasts 7.42 days, on an orbit 5 times closer to its star than Mercury is to the Sun. Its equilibrium temperature is 930 K, hot enough to melt lead. The host star Kepler-391 runs at 5038 K with 1.27 times the Sun's mass.

:COUNTER
380.0 g/cm3: denser than iron at Earth surface pressure

:STATS
[icon:TARGET] Radius | 2.50 Earth radii
[icon:CHART] Mass | 1100.0 Earth masses
[icon:FIRE] Equilibrium temperature | 930 K (measured)
[icon:CLOCK] One year | 7.42 days
[icon:BOLT] Orbit radius | 0.0830 AU
[icon:STAR] Host star | Kepler-391 at 5038 K
[icon:USERS] Distance | 2835 light-years
[icon:TRENDING_DOWN] Starlight blocked | 0.006% at each transit

:PATH
What the transit gives
The depth of the dip is the ratio of the two discs, so the radius follows.

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

:NOTE
Found by Kepler in 2014. Kepler watched a single field continuously, so it found the planets that come round often. A world with a long year simply never repeated within the mission.

:NOTE.half
Kepler-391 has 2 known planets. Multi-planet systems are where orbital dynamics can be measured rather than assumed.

:NOTE.half
Its orbit is noticeably elliptical, eccentricity 0.46, so the starlight it receives changes substantially over one year.

:LINK
https://exoplanetarchive.ipac.caltech.edu/overview/Kepler-391%20b
NASA Exoplanet Archive: the full record for Kepler-391 b