The first evidence of a planet outside our solar system came in 1992. This exoplanet was found near a rapidly spinning neutron star, or a pulsar. It now appears that this combination is very rare.

Zombie Planets

Much is still unclear about the origin and survival of a planet in a pulsar solar system. The electromagnetic radiation is immense, but at the same time it is very cold and dark. Zombie planets orbit a pulsar in a dead galaxy in a weird orbit.

The Jodrell Bank Observatory has observed 800 pulsars for fifty years. It turns out that exoplanets orbiting pulsars are very rare. Only in four of the eight hundred cases were Earth-sized exoplanets found.

Exo-Brandaris

“Pulsars rotate extremely stably around their axis. Each round, they send out powerful signals that we can pick up on Earth. You can think of it as a huge cosmic lighthouse,” says Iuliana Nitu, a PhD student at the University of Manchester, who will talk about these new findings at the National Astronomy Meeting (NAM) on July 12. “We can collect the electromagnetic data with radio telescopes. These signals are very interesting. We can make fascinating scientific discoveries with it.”

The very first exoplanet was discovered thirty years ago. This zombie planet orbits a pulsar named PSR B1257+12. There are at least three celestial bodies there that resemble the planets in our solar system.

Since this discovery in the 1990s, a handful of other pulsars have been discovered orbiting exoplanets. Apparently, the extreme cosmic violence with which a pulsar is formed is often a bit too much for the formation of local planets.

diamond planet

The exceptional planets that are found in the vicinity of a pulsar have rather unusual properties. For example, there are exoplanets that consist almost entirely of diamonds, and the orbit of these exotic celestial bodies around the pulsar is often extremely elliptical.

pulse. Photo: Science Photo Library

A team of astronomers from the University of Manchester conducted the largest pulsar search ever. The focus was on finding exoplanets with masses up to a hundred times that of Earth and an orbital period between twenty days and seventeen years.

Ten pulsar systems with potential were found. PSR J2007+3120 in particular looked suitable. It contains two exoplanets that are about twice as massive as Earth, with orbits around the pulsar of 1.9 and 3.6 years.

Eccentric Ellipse

The orbit of planets around the sun in our solar system resembles a circle. However, the exoplanets studied have a sharp elliptical orbit around their pulsar. This means that they originated in a very different way than in ‘normal’ solar systems. “Pulsars are incredibly impressive and exotic space objects. Exactly thirty years ago, the first planets were discovered outside our solar system. These exoplanets orbit around a pulsar,” said Nitu.

“We still know very little about the formation and survival of these planets under such extreme conditions. Finding out how often this combination occurs and what it looks like is extremely interesting. This data will take us a lot further in the search for the ins and outs of pulsars and their planets.”

What is a pulsar?

Even stars burn out one day. All hydrogen from the core is then converted into iron. A star with a mass about ten times the sun eventually implodes under its own gravity.

This enormous pressure causes the protons and electrons of the iron atoms to fuse into neutrons and a large part of the star explodes into space. What remains is a rapidly spinning pulsar about ten kilometers in diameter and a mass of one and a half to three solar masses.

Lighthouse Effect

The electromagnetic beams emitted at the poles are gigantic. We can observe these signals on earth. Each pulsar has its own very stable rotation period, somewhere between a few milliseconds and eight seconds. A kind of cosmic lighthouse.

The so-called ‘pulse profile’ of each individual pulsar is unique. This says a lot about the physical processes that take place in and around the pulsar. This allows us to learn a lot about possible exoplanets in the same system.

The first pulsar was discovered in 1967 by Jocelyn Bell in Cambridge. More than 2,600 pulsars have been described so far. The first exoplanet was discovered in 1992. It was spotted orbiting a known pulsar.