By: Charles Q. Choi, SPACE.com Contributor
Published: 10/01/2012 05:58 PM EDT on SPACE.com
Alien worlds that orbit the energetic dead stars known as pulsars may leave electric currents behind them – anomalies that could help researchers find more of these strange planets.
Astronomers know of only four "pulsar planets" so far, and much remains unknown about such worlds, but scientists propose that they formed in the chaos after the supernova explosions that gave birth to the pulsars.
A pulsar is a kind of neutron star, a stellar corpse left over from a supernova, a giant star explosion that crushes protons with electrons to form neutrons. Neutron star matter is the densest known material: A sugar cube-size piece weighs as much as a mountain, about 100 million tons. The mass of a single neutron star surpasses that of the sun while fitting into a ball smaller in diameter than the city of London.
This artist's impression shows the planetary system around pulsar PSR B1257+12, one of two pulsars known to be host to at least one planet. Such planets around pulsars may have powerful electromagnetic wakes around them.
Pulsars spin extraordinarily rapidly, up to thousands of revolutions per second, and they flash like lighthouse beacons — hence their name, which is short for "pulsating star." They are also extremely magnetic — a kind of pulsar known as a magnetaris the most powerful magnet in the universe.
Despite the exotic nature of pulsars, they have been seen hosting planetary systems.
Around pulsars, "nobody would expect to find planets like those we know … because the creation of a pulsar involves the supernova of a massive progenitor star," Fabrice Mottez, an astronomer and astrophysicist at the Paris Observatory, told SPACE.com. [Gallery: Strangest Alien Planets]
Mottez, lead author of a study into pulsar planets, and his colleagues suggested a new way to discover more of them: by looking for their wakes.
Pulsar planets could be interacting with the winds of electrically charged particles streaming from their pulsars, leaving powerful electric currents in their wake, the researchers said.
"In some circumstances, these currents would be almost as strong as those directly generated by the pulsar," Mottez said.
These electric currents should generate radio emissions. "The detectability of these planets with radio telescopes is currently under study," Mottez said.
Any world that survived the supernova that gave birth to a pulsar would be expected to have a very elongated, oval-like orbit. The supernova would have kicked the neutron star into motion at hundreds of miles per second, so planets that successfully followed these pulsars as they zoomed through space would have to move in comparably warped paths.
However, the four known pulsar planets all have very circular orbits, and they dwell rather close to their pulsars, at distances comparable to those of Mercury, Venus and Earth. This suggests they formed after the supernova, from debris that collected together shortly after the explosion.
The powerful magnetic fields and winds of particles from a pulsar should have profound effects on how planets form, and on smaller bodies such as asteroids and comets in its system, Mottez said.
The scientists presented their findings Sept. 28 at the European Planetary Science Congress in Madrid.
- Top 10 Star Mysteries
- Planets Large and Small Populate Our Galaxy (Infographic)
- Gallery: First Earth-Size Alien Planets Discovered
Related on HuffPost:
NASA's Kepler Mission Discovers Planet
In this handout illustration made available on December 5, 2011 by NASA, the Kepler-22b, a planet known to comfortably circle in the habitable zone of a sun-like star is digitally illustrated. For the first time NASA's Kepler mission has confirmed a planet to orbit in a star's habitable zone; the region around a star, where liquid water, a requirement for life on Earth, could persist. The planet is 2.4 times the size of Earth, making it the smallest yet found to orbit in the middle of the habit. Clouds could exist in this earth's atmosphere, as the artist's interpretive illustration depicts. (Photo Illustration by Ames/JPL-Caltech/NASA via Getty Images)
NASA's Kepler Mission Discovers Planet
In this handout illustration made available on December 5, 2011 by NASA, a diagram compares our own solar system to Kepler-22, a star system containing the first 'habitable zone' planet discovered by NASA's Kepler mission. The habitable zone is the sweet spot around a star where temperatures are right for water to exist in its liquid form. Liquid water is essential for life on Earth. The diagram displays an artist's rendering of the planet comfortably orbiting within the habitable zone, similar to where Earth circles the sun. Kepler-22b has a yearly orbit of 289 days. The planet is the smallest known to orbit in the middle of the habitable zone of a sun-like star and is about 2.4 times the size of Earth. (Photo Illustration by Ames/JPL-Caltech/NASA via Getty Images)
Extrasolar Planet HD 209458 b, Osiris
Artist's conception released by NASA of extrasolar planet HD 209458 b, also known as Osiris, orbiting its star in the constellation Pegasus, some 150 light years from Earth's solar system. Scientists have used an infrared spectrum -- the first ever obtained for an extrasolar planet -- to analyze Osiris' atmosphere, which is said to contain dust but no water. The planet's surface temperature is more than 700 Celsius (1330 Fahrenheit).'
Planet & Its Parent Star
Picture released 04 October 2006 by the European Space Agency shows an artist's impression of a Jupiter-sized planet passing in front of its parent star. Such events are called transits. When the planet transits the star, the star's apparent brightness drops by a few percent for a short period. Through this technique, astronomers can use the Hubble Space Telescope to search for planets across the galaxy by measuring periodic changes in a star's luminosity. The first class of exoplanets found by this technique are the so-called 'hot Jupiters,' which are so close to their stars they complete an orbit within days, or even hours. A seam of stars at the centre of the Milky Way has shown astronomers that an entirely new class of planets closely orbiting distant suns is waiting to be explored, according to a paper published 04 October 2006. An international team of astronomers, using a camera aboard NASA's Hubble telescope, delved into a zone of the Milky Way known as the 'galactic bulge', thus called because it is rich in stars and in the gas and dust which go to make up stars and planets. The finding opens up a new area of investigation for space scientists probing extrasolar planets - planets that orbit stars other than our own. AFP PHOTO NASA/ESA/K. SAHU (STScI) AND THE SWEEPS SCIENCE TEAM
Picture released 04 October 2006 by the European Space Agency shows an artist's impression of a unique type of exoplanet discovered with the Hubble Space Telescope. This image presents a purely speculative view of what such a 'hot Jupiter' (word dedicated to planets so close to their stars with such short orbital periods) might look like. A seam of stars at the centre of the Milky Way has shown astronomers that an entirely new class of planets closely orbiting distant suns is waiting to be explored, according to a paper published 04 October 2006. An international team of astronomers, using a camera aboard NASA's Hubble telescope, delved into a zone of the Milky Way known as the 'galactic bulge', thus called because it is rich in stars and in the gas and dust which go to make up stars and planets. The finding opens up a new area of investigation for space scientists probing extrasolar planets - planets that orbit stars other than our own. AFP PHOTO NASA/ESA/K. SAHU (STScI) AND THE SWEEPS SCIENCE TEAM
The Goldilocks Planet: Glises 581 G
Scientist have found a new potentially habitable planet.
Imagining Extrasolar Planets
From the Spitzer Science Center. While astronomers have identified over 500 planets around other stars, they're all too small and distant to fill even a single pixel in our most powerful telescopes. That's why science must rely on art to help us imagine these strange new worlds. From Spitzer Space Telescope. Even without pictures of these exoplanets, astronomers have learned many things that can be illustrated in artwork. For instance, measurements of the temperatures of many "Hot Jupiters," massive worlds orbiting very close to their stars, hint that their atmospheres may be as dark as soot, glowing only from their own heat. While "Hot Jupiters" would be relatively dark in visible light, compared to their stars, their brightness is proportionally much greater in the infrared. Illustrating this dramatic contrast change helps explain why the infrared eye of NASA's Spitzer Space Telescope plays a key role in studying exoplanets. As our understanding evolves, so must the artwork. Astronomers found a blazing hot spot on the exoplanet Upsilon Andromedae b that at first, appeared to face towards its star. More data has revealed that the hottest area is actually strangely rotated almost 90 degrees away, near the day/night terminator. WASP 12b is as hot as the filament in a light bulb, and would be blazing bright to our eyes. Most interestingly, if it proves to have a strongly elliptical orbit, as first thought, calculations show it would be shedding some of its outer atmosphere <b>...</b>