A Whole Planetary Year Fits Inside One Long-Haul Flight
A whole planetary year, start to finish, fits inside a single long-haul flight. TOI-6255 b, an Earth-sized world found in 2024, closes one full lap of its star in 20,578.96 seconds. Divide that by 3,600 and the orbit comes out to 5.72 hours. Board a flight from London to New York, watch the movie, land, collect a bag, the planet has already started its next year.
The measuring stick
5.72 hours fits inside spans of time you’ve actually sat through: a transatlantic flight runs six to eight hours; a workday with its commute isn’t far behind. That’s the point of picking it, a number in seconds doesn’t mean anything until it’s set against a stretch of time you’ve personally watched crawl by.
Set against Earth’s own year, 365.25 days, or 31,557,600 seconds, the standard figure astronomers use, TOI-6255 b’s orbit works out to about 6.52 × 10⁻⁴ of that. Flip the fraction and it reads more plainly: this planet completes roughly 1,533 orbits in the time Earth needs for one.
How we know
NASA’s Transiting Exoplanet Survey Satellite, TESS, caught the signal twice: in September 2019 and again in September 2022, watching the star’s light dip every time the planet crossed in front of it. That dip repeats like clockwork every 5.72 hours, and that repetition is where the orbital period comes from directly, measured, not modeled. Follow-up spectroscopy, splitting the star’s light to track a tiny gravitational wobble, with the Keck Planet Finder and the CARMENES instrument then pinned down the planet’s mass. Astronomer Fei Dai and colleagues published the full confirmation in The Astronomical Journal in 2024. The planet’s name comes straight from that pipeline: TOI stands for “TESS Object of Interest.”
Why your gut gets it wrong
TOI-6255 b’s radius measures 1.079 Earth radii, about 4,272 miles (6,874 kilometers), against Earth’s 3,959 miles (6,371 kilometers). Call it 8 percent wider. Its mass comes in at 1.44 times Earth’s, about 8.60 × 10²⁴ kilograms versus Earth’s 5.97 × 10²⁴ kilograms. On paper, this reads like a cousin of home: Earth-sized, Earth-ish in bulk.
But a 5.72-hour year is only possible if a planet sits brutally close to its star. TOI-6255 b orbits at just 0.0054 AU, an astronomical unit is the average Earth-Sun distance, 93 million miles (149.6 million kilometers), which puts the planet roughly 502,000 miles (807,800 kilometers) from its star. Its star is an M-dwarf, the small, cool class often called a red dwarf: measured at 3,421 K at the surface, with a radius about 37 percent of the Sun’s. Feed that heat and that distance into a model that assumes a surface reflectivity, or albedo, and you get an equilibrium temperature near 1,300 K (about 1,030 °C). That’s an estimate, not a thermometer reading, nobody has measured this planet’s surface directly, but it’s well past the point where silicate rock stops being solid. An Earth-sized, Earth-mass world, baked past the point where “Earth-like” stops meaning anything comforting.
What’s still open
TOI-6255 and its planet sit about 66.2 light-years away, or 20.3 parsecs, a parsec equals 3.26 light-years. That distance is solid. A few things about the planet’s fate are not.
Eccentricity comes out to exactly zero in the 2024 fit: a perfectly circular orbit. Whether that’s a direct measurement, or a default the fitting software falls back on when a very slight ellipse and a true circle look identical in the data, isn’t settled in the catalog entries themselves.
Models that assume a particular tidal strength for the star put TOI-6255 b roughly 400 million years from the Roche limit, the distance at which a star’s gravity starts pulling a planet apart. The orbit sits only about 13 percent outside that limit, with roughly 10 percentage points of uncertainty either way, which means nobody can yet say whether this world is settled or slowly spiraling toward the edge. The James Webb Space Telescope has a program queued, GO 8864, led by astronomer Lisa Dang, to watch the planet’s phase curve, the changing brightness as its day and night sides rotate into view.
No camera has photographed TOI-6255 b, and none can. Transit observations only ever record a dip in starlight, never a disc. Any picture claiming to show the planet itself is an artist’s illustration, not a photograph.