Stars shine through a process of nuclear fusion in which lighter atoms such as hydrogen fuse together to form heavier atoms.
All stars, including Sunhas a limited lifespan.
Stars shine through a process of nuclear fusion in which lighter atoms such as hydrogen fuse together to form heavier atoms. This process releases huge amounts of energy that counteract the constant inner pull of the star’s gravity. Ultimately, the merger helps stars resist gravitational collapse.
This balance of forces is called “hydrostatic equilibrium”. However, there will come a time when the fuel supply to the star’s core begins to run out and eventually dies.
Stars with a mass more than eight times the mass of the Sun typically burn out with their fuel in less than 100 million years. Once the fusion stops, the star collapses – resulting in a massive, momentary final explosion of nuclear fusion that causes the star to explode as a supernova.
A supernova releases enough energy to outpace the galaxy in which it occurs. What remains after that is collapsed, dead stellar cores called neutron stars or, if the preceding star was sufficiently massive, a black hole.
Any planets orbiting a star will be wiped out when it transforms into a supernova. But mysteriously, a handful of “zombie planets” have been discovered orbiting neutron stars. They are one of the strangest worlds in the universe.
Neutron stars are extremely dense, containing a mass equal to the mass of the Sun in a sphere only a few miles away. Some neutron stars emit beams of radio waves into space – and planets have been found around these “pulsating” stars.
As the pulsar rotates, its radio beams sweep through space to generate regular radio flashes. Pulsars were discovered in 1967 – you can listen to radio broadcasts from some of them here.
The regularity of these radio pulses makes pulsars ideal for searching for nearby planets. If a pulsar had a planet, they would both orbit a common center of gravity. This means that the radio transmission will periodically expand and compress in a predictable manner – allowing for this we to discover the planet.
Phobetor, Draugr, and Poltergeist
About 2,300 light-years from a land The pulsar PSR B1257 is located 12. It flashes 161 times per second and has been nicknamed “Lich” after an undead creature in Western folklore. It is orbited by three terrestrial rocky planets called Phobetor, Draugr and Poltergeist.
These planets occupy a special place in the history of astronomy, as they were the first after us Solar System (exoplanets) to be discovered again in 1991. A few years ago, NASA They released their “Zombie Worlds” poster:
Their discovery challenged ideas about planet formation, which usually occurs in the form of a new star. In contrast, these planets must have formed after the supernova of the dying star.
It is not yet known for sure how this happened. The material in a disk of debris orbiting the pulsar may have coalesced into post-supernova planets.
Draugr, named after an undead creature in Norse mythology, is the deepest of the three. It has a mass twice the mass of the Moon and is the currently lowest known planet by mass, orbiting Leach every 25 days. Its larger cousins, Poltergeist and Phobetor, orbit every 67 and 98 days, respectively, and are each about four times the mass of Earth.
Pulsars contain strong magnetic fields that may allow electric currents to arc through the space between the pulsar and the orbiting planet. Therefore, if any of these planets had an atmosphere, they could be constantly bathed in the mysterious light of strong aurora borealis (similar to our northern lights).
If you were to stand on the surface of one of these zombie worlds, you would see, through the strong color of the aurora borealis, the glowing Lich in the sky projecting two powerful and tightly controlled beams of light outward in opposite directions into the blackness of space.
Neutron stars can be extremely hot, carrying residual heat from the supernova. Lich has a temperature of nearly 30,000 degrees Celsius, and the Lich temperature in the depths of these worlds, Draugr, is likely only a few degrees below freezing on their surface.
Planet PSR J1719−1438b orbits a pulsar about 4,000 light-years away, and orbits its host in just over two hours.
It’s the densest planet yet discovered—so dense, in fact, it’s thought to be made largely of diamond.
This “diamond world” is the remaining core of a dead star called a white dwarf. This dwarf is known to have a high carbon content (diamonds are made of carbon) – but this particular white dwarf has lost 99.9 percent of its original mass, which was consumed by the strong gravity of the nearby pulsar.
This diamond ball is about half the size of it Jupiter, and it orbits PSR J1719-1438 at a distance of 600,000 km (just 1.5 times farther from our Moon than Earth). At such a distance from the host pulsar, this world would likely have an extremely hot surface.
Orbiting the Milky Way (and many galaxies) are globular star clusters – globular clusters of up to a million stars each. These are some of the oldest stars in the universe.
The globular star cluster Messier M4 is located about 5,600 light-years away and contains about 100,000 stars. Among them was a planet called Methuselah, after the son of Enoch in the Book of Genesis World Health Organization He is supposed to live for 969 years.
At the center of the M4 star cluster is a pulsar and a white dwarf that orbit their common center of gravity every 161 days. Given the short-lived nature of high-mass stars, the pulsar may have formed shortly after the formation of Messier 4 itself.
Methusheleh also orbits this center, but at a much more comfortable pace at the rate of once every 100 years or so, at a distance similar to that of Uranus orbiting our sun.
It is a gas giant planet with a mass about 2.5 times that of Jupiter. Methuselah is thought to have formed as a natural planet around a sun-like star during the first billion years of the universe’s formation. It was then captured into orbit around the host pulsar, which has been in orbit ever since.
The high density of stars in globular clusters makes the chances of two stars meeting up close—and similarly exchanging planets. Methosaleh is the oldest known planet in the world Universehaving formed an estimated 12.7 billion years ago with all the stars in M4.
Pulsating planets are extreme worlds, but they may not be the most unusual. A few theoretical studies have suggested the existence of planets in orbits black holes. So far, however, none have been found.
Written by Gareth Dorian, Postdoctoral Research Fellow in Space Science, University of Birmingham
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