On April 21, 1994, astronomers announced “unambiguous proof” of exoplanets, confirming research originally published in 1992. But these first-discovered planets outside our solar system didn’t come in any form scientists had anticipated.
Neutron stars are the second densest type of object in the universe outside black holes. They form when a giant star dies and explodes outward as a result of the collapse of its core. Put simply, the star becomes too massive to go on and expels all its energy into the surrounding space. The core is a sort of ground zero of this detonation. When that core collapses, depending on the size of the star, it becomes either a neutron star or a black hole.
Some neutron stars are called pulsars, for the regular “pulses” they give off in radio frequencies. Think of them like a drummer — fast regular beats. Those pulses are so regular that if they don’t come at the right interval, astronomers know something is off.
A breakthrough in 1992 provided evidence of planets. Astronomers Aleksander Wolszczan and Dale Frail tuned into the pulsar PSR B1257+12. It should have pulsed every 0.006219 seconds, but every now and then, its pulses were a little off. Yet those off-beats came at regular intervals as well. After intensive study, Wolszczan and Frail came up with an explanation for why that was: It had two planets around it. One was around three and the other about four times the mass of Earth, and they rotated around every 67 and 98 days, rounded up. (They also noted the possible presence of a third planet, which was later confirmed in 1994.)
Pulsar planets are somewhere in between a zombie and a chimera. When a star explodes, usually the planets in that system are destroyed or flung out by a shockwave. But after the violence settles down, the gas and dust can recondense. This, in effect, means that the three planets in B1257 may be made out of parts of the planets that came before them. Given the extreme radiation in these systems, almost no one has ever thought that the B1257 system could host life. So, while the 1992 discovery was major news, it meant astronomers had the first verified planets around another star, but no proof of planets around a main sequence star like the Sun. That kind of confirmation was still a few years away.
