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Despite the deadly rays, pulsars can host habitable planets

Artist’s impression of a habitable planet (in the middle) in the vicinity of a pulsar (right). Such a planet should be a huge atmosphere that converts the deadly X-rays and high-energy particles from the pulsar into heat.

(Institute for Astronomy, University of Cambridge)

Although pulsars regularly blast out deadly gamma rays and X-rays, alien planets in orbit around them can in theory be habitable, a new study found.

However, this pulsar worlds are probably not friendly to humans — according to the study of the planets’ environment, it would be more like the bottom of the sea on Earth.

When a large star explodes in a supernova at the end of its life, it can behind a dense core of matter called a neutron star. Neutron star matter is the densest known material — a sugar cube-size piece of the mass of a mountain, about 100 million tonnes. The mass of one neutron star is higher than that of the sun, while fitting in a ball smaller in diameter than London. [In a neutron star (Infographic)]

Pulsars rotate extremely rapidly, up to thousands of revolutions per second, and they flash like lighthouse beacons — hence their name, which is short for “pulsating star.” They periodically blaze with gamma-rays and X-rays and syringes from energetic particles. According to the new study of researchers of the Milky way hosts about 1 billion neutron stars, about 200,000 of which are pulsars.

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Despite the violent nature of pulsars, they can still have planets. In fact, the first exoplanets that astronomers have discovered orbiting the pulsar B1257+12, located at about 2300 light-years away from Earth in the constellation Virgo.

Three worlds known to orbit B1257+12, which is about a fiftieth of the mass of earth, while the other two are “super-Earths” about four times the mass of earth. Since these three exoplanets were discovered in 1992, astronomers have also discovered a Jupiter-sized world around the pulsar PSR J1719–1438, and other Jupiter-size world, around PSR B1620-26, which is a binary system with a pulsar and a white dwarf star.

Now the researchers suggest that life could exist on that pulsar is in orbit around the planets. “Despite that deadly particles and radiation, pulsars, might be a habitable zone,” study co-author Alessandro Patruno, an astrophysicist at the University of Leiden in the Netherlands, told Space.com.

Since there is life virtually wherever there is water on Earth, astronomers often judge a world as potentially habitable if it exists in a zone in which liquid water could survive on the surface. In the new study, the researchers found “habitable zone” may exist around neutron stars.

“The habitable zone may be as wide as the one that exists around normal stars,” study co-author Mihkel Kama, astrophysicist at the University of Cambridge in England, told Space.com.

The scientists used the Chandra space telescope to analyze X-rays of the pulsar B1257+12. Their calculations suggest that this pulsar two super-Earths, perhaps warm enough to have liquid water on the surface, Patruno said. [The X-Ray Universe: Chandra X-Ray Space Observatory Pictures]

The researchers noted the habitability of planets around pulsars depended on at least two important findings. For one, there is a million times thicker than the Earth is likely to be necessary for protecting life at the surface of pulsar radiation. This would make conditions on these worlds similar to those that occur in the Earth’s deep seas.

“The atmospheric pressure on the surface of these planets is comparable with or even higher than the pressure in the Mariana Trench,” which at 36,000 feet deep (11,000 meters) is the deepest known point on the earth’s surface, Kama said.

“However, because we know that life exists in the depths of our oceans, a form of life could certainly exist in this high pressure and warm environments,” Patruno said.

Another important finding was that the habitable worlds around pulsars are likely to be super-Earths with masses up to 10 times that of the Earth, the stronger gravity fields to help them keep their environment for a billion or so years, the researchers said. The scientists calculated that the radiation from pulsars would destroy the atmosphere of a smaller planet within a few thousand years, that any liquid water on the surface to boil away.

The researchers started with this work, “and expected that it would be impossible to have a habitable zone around pulsars,” Kama said. “Instead, we quickly realized that for super-Earths this is a very solid possibility. Add on top of that the fact that the only multi-planetary pulsar system known, has two super-Earths, and our excitement skyrocketed.”

For the worlds in the habitable zones of pulsars, “the high energy particles and radiation will keep the atmosphere warm enough to keep the liquid hot water to exist,” Patruno said. “Since there is hardly any visible light that the planet — pulsars emit almost no visible light — this opens up a whole unexpected scenarios for exotic habitable environments.”

The scientists note that even a thick atmosphere can not block the high-energy radiation of pulsars. “Some of it might still to the surface of the planet, that could then be detrimental for any form of life,” Kama said.

Patruno and Kama detailed their findings online Dec. 19 in the journal Astronomy & Astrophysics.

Original article on Space.com.

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