The discovery of the first exoplanet by mankind was an incredible accident


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In the early 1990s, planetary history was made. In 1992, two astronomers, Alexander Volshchan and Dale Fraile, published an article in Nature announcing the discovery of the very first planets outside the solar system.

These two extrasolar planets, or exoplanets, immediately intrigued. These were rocky worlds, 4.3 and 3.9 times the mass of the Earth, orbiting a type of dead star known as a millisecond pulsar, called PSR B1257+12, or Lich for short (Lich is a powerful living dead being in folklore) . . In 1994, a third exoplanet, 0.2 times the mass of Earth, was confirmed to be orbiting a pulsar.

Now, an analysis of hundreds of pulsars has shown that such exoplanets are incredibly rare—almost disappearing.

Pulsars are quite rare; only about 3,320 are known in the Milky Way at the time of writing. Of these, astronomers now say less than 0.5 percent likely have rocky, Earth-like worlds in orbit. There are 16 pulsars in total.

Millisecond pulsars are even rarer, with about 550 known in the Milky Way. This makes the earliest human discoveries of exoplanets pretty damn amazing.

All dead stars are charming, but pulsars add a bit of interest to the interesting factor.

It’s kind of like a neutron star; it is the core of a dead star that has reached the end of its fusion period, ejected most of its outer material, and collapsed into an object whose density is second only to black holes. Neutron stars can be about 2.3 times the mass of the Sun and are packed into a sphere only 20 kilometers (12 miles) in diameter.

A pulsar is a spinning neutron star whose rays of radiation emanate from its poles. Its orientation is such that as the pulsar spins, its beams pass by the Earth, giving the impression that the star is pulsing. Imagine a really dense space beacon.

And because some pulsars spin extremely fast—on millisecond scales—these light pulses also occur on millisecond scales. To better understand what this means, you can listen to the pulses of the pulsar translated into sound here.

It’s a pretty extreme environment. They may have exoplanets; since the discovery of Lich and his worlds, several other exoplanet-bearing pulsars have been discovered. However, most of these planets are giants, and those that aren’t can get a little weird, like the superdense world thought to be the remnants of a white dwarf eaten by a pulsar.

A group of astronomers led by Juliana Nitsu from the University of Manchester in the UK wanted to find out how common pulsar planets are. They surveyed 800 pulsars monitored by the UK’s Jodrell Bank Observatory looking for bursts of pulse time that could indicate the presence of exoplanets in orbit.

“Pulsars are incredibly interesting and exotic objects,” Niu said.

“Exactly 30 years ago, the first extrasolar planets were discovered around a pulsar, but we have yet to understand how these planets can form and survive in such extreme conditions. Finding out how common they are and what they look like is an important step. to that”.

Their search parameters were set to search for worlds from 1 percent of the mass of the Moon to 100 times the mass of the Earth, with orbital periods ranging from 20 days to 17 years. These search parameters would reveal the larger of the Lich’s two worlds, Poltergeist and Phoebetor, which have orbital periods of 66 and 98 days respectively.

The team found that two-thirds of the pulsars in their sample are extremely unlikely to contain exoplanets much heavier than Earth, and less than 0.5 percent are likely to contain exoplanets in the Poltergeist and Phoebetor mass ranges.

The presence of exoplanets similar to the smaller exoplanet in the Leach system, Draugr, is a bit more difficult to assess.

The Draugr, with its low mass and 25-day orbit, will not be found in 95 percent of the team’s samples, as it will get lost in the noise. It is not clear how many pulsars such tiny worlds can contain; or even whether it is possible for these worlds to exist outside of a multi-planetary system.

Of the 800 pulsars, 15 showed periodic signals that could be attributed to exoplanets. However, the team believes that most of them can be attributed to the magnetosphere of the pulsar. One pulsar in particular, PSR J2007+3120, looked like a promising candidate for future exoplanet studies.

This means that only 0.5 percent of pulsars could have Earth-like worlds, the team concluded, meaning that the chances of us stumbling upon a distant planet with a rare millisecond pulsar for a star are pretty low.

The team also found that pulsar systems are not prone to any range of exoplanet sizes or masses. However, any such exoplanets around a pulsar would have extremely elliptical orbits. This is in stark contrast to the near-circular orbits seen in the solar system and suggests that, however they formed, the process was different from that which creates planets around young stars just beginning their lives.

The group’s study was presented last week at the National Astronomical Meeting in the UK and published in Royal Astronomical Society Monthly Notices.

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