Orbit shrinking≈ 30 ms per yearits year gets shorter[2]
Time leftabout 3 million yearsTurner et al. 2021; Wong et al. 2022[2]
About the image. Drawn dark and egg-shaped, losing a stream of gas. The stretching, the gas loss and the darkness are measured or modelled; the exact shape of the stream is imagined.
72×as wide as our Sun looks from Earth
7 200×the light Earth gets
Expected to be tidally locked: the star stays putNo ground: the view from the cloud tops
The sky from WASP-12b
WASP-12 would look 72× as wide as the Sun does from Earth, and the planet gets 7 200× as much light as Earth gets.
Its colour comes from its surface temperature of 6 265 K (5 990 °C); the Sun's is about 5 772 K (5 500 °C).
WASP-12b is expected to be tidally locked: one side always faces the star.
There are no sunrises. Where you stand decides where the star hangs, overhead on the day side, low at the edge, gone on the night side.
Apparent size = star radius ÷ orbit; light = size² × (temperature ÷ 5 772 K)⁴. Both from the values on this page. The landscape is imagined.
WASP-12b was found in 2008 by the SuperWASP survey. It is a hot Jupiter in the most extreme sense: a gas giant almost twice Jupiter’s width that races around its star in just 26 hours, so close that its year is shorter than an Earth day.
Stretched into an egg
At that distance the star’s gravity pulls harder on the near side of the planet than on the far side. In 2010 Shu-lin Li and colleagues showed in Nature that this has stretched WASP-12b into an elongated, egg-like shape, with its puffed-up atmosphere spilling beyond the point where the planet can hold on to it. It is losing gas at a rate of roughly six billion tonnes every second, and the same year Hubble watched it being consumed. With a density of only 0.27 grams per cubic centimetre, it is among the lightest, fluffiest planets known.
Spiralling in
The planet’s orbit is shrinking. Since 2008 each year has become about 30 milliseconds shorter, a change that careful timing of its transits has now confirmed several times. For years another explanation was possible: a slightly oval orbit that slowly swings around could also make the transits drift. In 2020 Samuel Yee and colleagues used new transit and eclipse timings to favour decay over that idea, and new radial-velocity data to rule out a further timing effect. That made WASP-12 the first planetary system in which astronomers could be confident that an orbit is decaying. Studies in 2021 and 2022 estimate it has about three million years left before it falls into its star.
Black as asphalt
In 2017 Hubble showed how little light the planet reflects: at most about 6 percent, as dark as fresh asphalt. The team, led by Taylor Bell, used the STIS spectrograph in October 2016 to catch the planet as it passed behind its star, which isolates reflected light but needs about ten times the precision of an ordinary transit observation. Their upper limit, an albedo of 0.064, makes it about half as reflective as the Moon. The day side is too hot for clouds, and the heat breaks hydrogen molecules into single atoms, so the atmosphere behaves more like that of a low-mass star than a planet’s. Its day side is over 2 500 K (2 230 °C), and it glows faintly red from its own heat. A 2010 study suggested it holds more carbon than oxygen, which led to headlines about a diamond planet; that label came from the media, not the research. Its orbit is also tilted about 59 degrees to its star’s equator.
Its orbit, to scale
WASP-12b goes around once every 1.1 days, at 0.0234 AU from its star. The whole view is tiny on Solar System scale: Mercury orbits the Sun about 17 times farther out than the outermost orbit shown here.
WASP-12b: equilibrium temperature. Logarithmic scale from 100 K to 10 000 K. Reference values: NASA, IAU.
How long to get there?
WASP-12b is about 1 390 light-years away.
Light299 792 km/s1 390 years
Breakthrough Starshotplanned light sail, 20% of light speed6 950 years
Parker Solar Probefastest spacecraft so far, 192 km/s2.2 million years
Voyager 1leaving the Solar System, 17 km/s24.5 million years
At Voyager 1's speed the trip would take about 306 405 human lifetimes of 80 years. Bars are on a logarithmic scale. Speeds: NASA, Breakthrough Initiatives.
Your weight on WASP-12b
On WASP-12b
Gravity there is about 0.96× Earth's, at the cloud tops; there is no surface. Calculated from the measured mass and radius.
Gallery
A dark planet with a glowing outline, a stream of gas pulled from it towards a bright star on the left, an impression of WASP-12b. AI-generated painting.A huge dark planet curving around a bright star whose glow lights its stretched outer edge, an impression of WASP-12b. AI-generated painting.WASP-12b, 3D artist's impression, rendered from the interactive model.WASP-12b, 3D artist's impression, from another angle, rendered from the interactive model.WASP-12b, 3D artist's impression, close-up, rendered from the interactive model.
Timeline
2008Discovered by the SuperWASP survey.
2010Shown to be stretched into an egg shape and losing gas.
2017Hubble finds it reflects only about 6% of light.
2021Its shrinking orbit is measured: about three million years left.
Questions people ask
Is WASP-12b being eaten by its star?
Yes, slowly. It is losing gas to its star and its orbit is shrinking. It may fall in within about three million years.
Why is WASP-12b egg-shaped?
The star's gravity pulls much harder on the near side of the planet than on the far side, stretching it.
Is WASP-12b a diamond planet?
No. That was a media label. A 2010 study suggested it is rich in carbon, but that did not mean it is made of diamond.