In 1991, radio signals from the pulsar PSR B1257+12 in the constellation Virgo led Penn State professor of Astronomy and Astrophysics Alexander Wolszczan to the discovery of the first planets ever known outside our solar system.
Wolszczan used the worlds largest radio telescope in Arecibo, Puerto Rico, to time the radio signals coming from a distant tiny neutron star in the constellation Virgo, 7,000 trillion miles from Earth. These measurements helped him to determine that two of the planets are similar in mass to Earth and the other is about the mass of the Moon.
The neutron star Wolszcan discovered is the remnant of a supernova explosion--with a mass larger than the Sun's compressed within a radius of 10 kilometers with density 100 trillion times higher than an ordinary solid. The radiation netron stars emit is exponentially brighter than a terrestrial laser and its magnetic fields are millions times more intense than what can be created in Earth-based labs along with gravity a 1000 billion times stronger than on Earth.
The neutron star PSR B1257+12 radiates little light, but it emits penetrating x -rays and ejects winds at nearly the speed of light. Astronomers are baffled at how this planetary system got there. But current thinking is that the earlier star had its own system of planets before its supernova phase. The three remaining planets existed on the outer orbits, possibly with life forms that would have been snuffed out by the vaporizing blast of the supernova.
The Cambridge physicist, Lord Martin Rees, suggests that life could possibly evolve on the neutron star itself as a "hyper-dense microscopic organisms controlled by nuclear forces with a metabolism faster than ordinary chemical-based life.
All three pulsar planets are shown in the image below; the farthest two from the pulsar (closest in this view) are about the size of Earth. Radiation from charged pulsar particles would probably rain down on the planets, causing their night skies to light up with auroras similar to our Northern Lights. One such aurora is illustrated on the planet at the bottom of the picture.
Since this landmark discovery, more than 160 extrasolar planets have been observed around stars that are burning nuclear fuel. The planets spotted by Wolszczan are still the only ones around a dead star. They also might be part of a second generation of planets, the first having been destroyed when their star blew up. The Spitzer Space Telescope's discovery of a dusty disk around a pulsar might represent the beginnings of a similarly "reborn" planetary system.
Not so oddly, in 1973 radio astronomer Frank Drake (of Drake's Equation fame) suggested that intelligent life could inhabit neutron stars, which inspired science-fiction author Robert Forward's classic, Dragon's Egg, that developed Drake's theory that such creatures would be microscopic. It's a story of sacrifice and triumph, human scientists establish a relationship with intelligent lifeforms--the cheela--living on Dragon's Egg, a neutron star where one Earth hour is equivalent to hundreds of their years. The cheela culturally evolve from savagery to the discovery of science, and for a brief time, humans are their diligent teachers.
The image at the top ofthe page shows pulsar PSR J1846-0258, the brightest point at the center, is surrounded by its non-thermal 'pulsar wind nebula' in blue. The green partial shell is the actual (gas) remnant of the star that exploded (leaving the neutron star behind), thermally equilibrating as it interacts with the surrounding medium.
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