Exoplanets · Space Codex
PSR B1257+12 planets
Three planets orbiting a dead star, a millisecond pulsar, found in 1992 from tiny delays in its radio pulses, three years before the first planet around a Sun-like star.
The first exoplanets ever confirmed
Artist's concept. No telescope has seen PSR B1257+12 planets as more than a point of light, and most exoplanets not even that. What we know comes from how a planet dims or tugs its star. Any picture of its surface, colour or sky, anywhere, is an illustration, not an observation.
At a glance
Key points
- First confirmed exoplanets (1992)
- Orbit a dead star
- Planet b is about twice the Moon's mass
How they were found
Aleksander Wolszczan discovered the pulsar in 1990 with the 305-metre Arecibo radio telescope in Puerto Rico. Its flashes, normally as regular as an atomic clock, arrived slightly early and then slightly late in a repeating pattern. With Dale Frail he traced the pattern to two bodies of a few Earth masses on orbits of about 67 and 98 days, published in Nature in January 1992. The much smaller planet b followed in 1994.
Proof from their tugs
Planets c and d orbit close to a 3:2 ratio, so they pull on each other in a predictable way. Detecting those mutual perturbations in the timing data ruled out other explanations and pinned down their true masses, something radial-velocity planets usually lack.
A cautionary tale
In 1991 a team at Jodrell Bank announced a planet around a different pulsar, PSR B1829−10. In January 1992 they withdrew it: Earth's own motion around the Sun had not been fully removed from the timing. The PSR B1257+12 planets survived the same scrutiny, and years of further timing strengthened the case.
Planets after death
These worlds probably formed from a disc of debris after the supernova that created the pulsar. They receive almost no visible light, only the pulsar's high-energy radiation and particle wind.
What we still don't know
How common such second-generation planets are. Only a handful of pulsar planets are known, and the radii, atmospheres and make-up of these three are unmeasured.
Related entries
- PulsarsCosmic lighthouses
- Exoplanets: the censusPlanets around other stars
Sources
- Wolszczan & Frail 1992, Nature 355:145 (ADS) (opens in a new tab)
- Wolszczan 1994, Science 264:538 (ADS) (opens in a new tab)
- Lyne & Bailes 1992, Nature: No planet orbiting PSR1829−10 (opens in a new tab)
- NASA Exoplanet Archive: PSR B1257+12 overview (opens in a new tab)
- IAU: NameExoWorlds results (iau1514) (opens in a new tab)
- NASA Exoplanet Archive (IPAC/Caltech) (opens in a new tab)
Last reviewed against these sources. Built from public NASA, ESA and JPL data; not affiliated with or endorsed by any agency.