- weight
- 0.31 g
- sun
- 4.4× wider
- sky
- warm white
Illustration computed from this world’s measured and derived values, not a photograph.
HD 191939 d
HD 191939 d is a confirmed sub-Neptune exoplanet 175 ly from Earth in the constellation Draco, discovered in 2020 by Transiting Exoplanet Survey Satellite (TESS).
Transit: spotted by the tiny, repeating dip in its star’s light each time the planet crosses in front of it.
Standing on HD 191939 d, you would weigh about 69% less than you do on Earth. Its yellow, Sun-like star looks 4.4× wider than ours, bathing the surface in warm white light. It is likely tidally locked, so that sun never moves in the sky: one hemisphere in endless day, the other in permanent night. A year passes in just 38 days, and at an estimated 267°C (512°F) it is blistering.
How closely this world matches Earth in size and warmth, from 0 to 1 (Earth = 1.0). Computed by gravityfinder. See every world ranked →
What these mean: surface gravity · tidal locking · equilibrium temperature · Earth similarity
If your children grew up herea playful thought experiment
Low gravity, 0.31 times Earth's. A child who grew up here could become strikingly tall and lightly built, about 1.3x taller than on Earth: a 5 ft 10 in adult could stand nearer 7 ft 4 in, with long limbs and slender bones.
- Bones
- Light and slender
- With little weight to carry, the growing skeleton lays down far less bone, the way astronauts' bones thin in months of low gravity.
- Heart
- Unhurried
- With less weight pulling blood down toward the feet, the heart has far less work to do.
- Movement
- Bounding and springy
- So little weight means each step would carry the body up and forward in long, floating strides.
A playful thought experiment from this world’s gravity, not a prediction about any real person. No human has ever grown up off Earth, so no one truly knows; the direction (taller in low gravity, shorter and stockier in high) follows how growing bodies respond to weight.
Hear how a voice sounds herea computed acoustic demo
Your voice would sound high and thin, almost cartoonish.
Assuming Earth-like air at this world's temperature of about 267°C (512°F), sound would travel roughly 37% faster than on Earth, so your voice would sound high and thin, almost cartoonish. The real atmosphere is unknown, so this is a best guess.
A real voice sample, pitch-shifted (tempo held constant) to suggest the acoustics: a playful approximation, not a precise simulation. Voice: Lingua Libre / Vealhurl, CC BY-SA 4.0.
- !Blistering at about 267°C (512°F), far too hot for liquid water on the surface.
- !Far too little gravity, 0.31 times Earth's, to hold a breathable atmosphere: effectively an airless vacuum.
- !Likely tidally locked: one hemisphere in endless day, the other in permanent night.
A playful read of HD 191939 d’s measured and computed values, not a real advisory.
How long to get there · 175 ly away
Zoom out: star → system → (soon) galaxy arm, host black hole, and a real image of the host galaxy.
Matched telescope & eyepiece recommendations are coming. Any product links will carry a clear affiliate disclosure.
What is the gravity on HD 191939 d?
HD 191939 d's surface gravity is about 0.31 times Earth's.
How much would you weigh on HD 191939 d?
Someone who weighs 150 pounds on Earth would weigh about 47 pounds on HD 191939 d.
How far is HD 191939 d from Earth?
HD 191939 d lies about 175 light-years from Earth.
How long would it take to get to HD 191939 d?
At the speed of NASA's Parker Solar Probe, the fastest craft ever built, the journey would take about 272,696 years.
How hot is HD 191939 d?
HD 191939 d's equilibrium temperature, the balance it reaches from its star's light alone before any greenhouse warming, is about 267°C (512°F).
How long is a year on HD 191939 d?
HD 191939 d completes one orbit of its star in 38 days.
Illustration generated from HD 191939 d's confirmed parameters, not a photograph.