Watch a distant star brighten for no visible reason - no host star, no resolved image, just a brief lift in brightness. That absence is the whole signature of a rogue planet: a starless, planet-mass object detected purely by gravitational microlensing.
Rogue Planets 3D Explorer
Scrub a gravitational-microlensing event with no host star anywhere in it, and see why that absence - not a resolved image - is how astronomers find free-floating planets drifting alone in the galaxy.
What a rogue planet is, and why only microlensing catches one
Every confirmed exoplanet you have probably heard of orbits a star. A rogue (or "free-floating") planet does not - it was either flung out of its birth system or never fully formed one, and now drifts through the galaxy with no host at all. Because it emits no light of its own and has nothing to orbit, the only way to catch one is to watch a distant background star and wait for the rogue planet's gravity to briefly, invisibly, bend and brighten that star's light as it passes in front of it.
What the Rogue Planets explorer shows
- A monitored background star with a growing brightness halo driven by the real single-lens (Paczynski) magnification formula
- Three lens-mass presets - a comparison star, a Jupiter-mass planet, and an Earth-mass planet - each showing the real published event duration for that mass class
- A "Show inferred path" toggle that reveals a teaching-aid marker for the otherwise completely invisible lens - by default nothing marks it, matching what a real telescope actually sees
- A survey-estimate toggle comparing the widely reported 2011 population estimate against the 2017 survey that revised it down
- A live light-curve canvas tracing brightness vs. event progress, with Play/Pause and a scrub slider
- Runs on your device with WebGL and the vendored three.js engine - no account, no upload, nothing about your visit sent to a server; the engine is a one-time 0.7 MB cached download, and your lens-mass and view choices are remembered on your device
Recorded events and population estimates
| Quantity | Value |
|---|---|
| Shortest microlensing event ever recorded | OGLE-2016-BLG-1928, 41.5 minutes (Mroz et al. 2020) |
| That event's implied lens mass | about 0.3-2 Earth masses; no companion star within 8 AU |
| Typical stellar-mass microlensing event | about 20-40 days |
| 2011 population estimate | ~1.8 Jupiter-mass objects per star, ~75% unbound (Sumi et al. 2011) |
| 2017 revision | 95% upper limit of ~0.25 Jupiter-mass free-floating planets per star (Mroz et al. 2017) |
| JWST direct-imaging evidence (2023) | ~540 planet-mass objects in the Orion Nebula, including 42 JuMBO pairs/triples |
| Ground surveys | OGLE, MOA, KMTNet |
Why the lens itself is never seen
A rogue planet emits no light of its own, so the single brief brightening of the background star - and nothing else - is the entire detection. That is also why the event is so short: the lighter the lens, the faster it crosses the line of sight, so a planet-mass lens crosses in hours or less instead of the weeks a star-mass lens takes.
How the 2011, 2017, and 2023 results fit
The 2011 estimate suggested rogue Jupiter-mass planets could outnumber ordinary stars roughly two to one; the much larger 2017 follow-up did not confirm that excess and placed a far lower upper limit. The 2023 James Webb Space Telescope imaging of young, still-warm planet-mass objects in the Orion Nebula is a different method that does not depend on microlensing at all - one of the few ways a free-floating planet can be seen rather than only inferred.
The sibling explorer for a planet with a host star
For a planet detected while still orbiting its own star via the same microlensing technique, see the Gravitational Microlensing Exoplanet 3D Explorer - that page's secondary spike sits on top of a multi-week host-star event; this page's entire event is the short signature of having no host star at all.
Model limits and accuracy
This is an educational approximation, not a lensing simulation: the brightness curve uses the standard single-lens magnification formula, and the visual width shown for each mass preset is illustrative rather than a computed physical timescale - the real duration for each mass class is the cited figure in the facts panel and the table above.
Frequently Asked Questions
What is a rogue (free-floating) planet?
A planet-mass object that does not orbit any star - either flung out of its birth system or never fully attached to one. It drifts through the galaxy on its own, emitting no light of its own to detect.
How do astronomers find a planet with no host star and no light of its own?
Almost entirely through gravitational microlensing: when the rogue planet's gravity happens to pass directly in front of a distant background star, it briefly bends and focuses that star's light, causing a short, one-time brightening. No resolved image ever forms - only the brightness change reveals it.
Why is a rogue planet's microlensing event so much shorter than a normal one?
Event duration scales with the mass of the lens - a lighter lens crosses the line of sight faster. A star-mass lens produces a multi-week event; a Jupiter-mass rogue planet's event lasts hours to about a day; the lightest confirmed candidate, OGLE-2016-BLG-1928, lasted only 41.5 minutes.
What is OGLE-2016-BLG-1928?
The shortest gravitational-microlensing event ever recorded, lasting 41.5 minutes (Mroz et al. 2020). Its properties point to a lens of about 0.3 to 2 Earth masses with no companion star detected within a projected separation of 8 AU - the shortest, and one of the most closely-studied, rogue Earth-mass planet candidates found so far.
How many rogue planets are there really?
Estimates have changed as surveys grew. A 2011 study suggested roughly 1.8 Jupiter-mass objects per main-sequence star, with about three-quarters likely unbound - close to twice as many rogue Jupiter-mass planets as stars. A much larger 2017 survey did not confirm that excess, instead setting a 95% upper limit of about 0.25 Jupiter-mass free-floating planets per star. This explorer shows both figures rather than picking one.
Has the James Webb Space Telescope found rogue planets too?
Yes, by an entirely different method. In 2023, JWST directly imaged about 540 young, still-warm planet-mass objects in the Orion Nebula's Trapezium region, including 40 paired and 2 tripled "Jupiter-mass binary objects" (0.6-14 Jupiter masses). Direct imaging works there because the objects are young and still glowing with formation heat - it does not rely on microlensing at all.
How is this different from the Gravitational Microlensing Exoplanet explorer on this site?
That page shows a planet still orbiting a visible lens star - the planet only adds a short secondary spike on top of the star's own multi-week brightening event. This page has no host star at all: the planet-mass object itself is the entire lens, and the whole event (not a secondary spike) is short, which is the defining signature of a genuinely free-floating planet.
Is this a real physics simulation?
No. It is an educational approximation, not a lensing simulation. The brightness curve uses the standard single-lens (Paczynski) magnification formula; the visual width shown for each mass preset is illustrative, not a computed physical timescale - the real event duration for each mass class is the cited published figure shown in the facts panel.