(ORDO NEWS) — Exoplanets were first discovered 30 years ago in a rapidly rotating star system called a pulsar. Now astronomers have found that such planets can be very rare.
The processes leading to the formation and stable existence of planets in pulsar systems are still unknown to science.
A survey of 800 pulsars observed by the Jodrell Bank Observatory at the University of Manchester, USA, over the past 50 years, showed that the planetary system in which the first exoplanet was discovered is extremely rare in the Universe – only less than 5 percent of all known pulsars may have a planet like Earth in their system.
These bodies are exceptionally stable, rotate at great speeds, and have powerful magnetic fields. Pulsars emit intense beams of radio emission from their magnetic poles, which look to us as if they pulsate as the neutron star rotates.
In 1992, the first exoplanets in the history of science were discovered in orbit around a pulsar. Now in this planetary system, scientists know at least three planets that are close in mass to the rocky planets of the solar system.
Since then, researchers have been able to detect only a few other planetary systems surrounding pulsars. In addition, the extreme conditions that accompany the emergence of pulsars determine the predominant presence in their systems of unusual planets, such as, for example, completely diamond planets, instead of planets similar to the rocky planets of the solar system.
In their new work, a team of astronomers led by Iuliana Nițu from the University of Manchester, UK, has conducted the largest search for signals indicating the presence of planets in pulsar systems.
In particular, the team was looking for signals indicating the presence of companion planets with masses up to 100 Earth masses and orbital periods between 20 days and 17 years.
Of the 10 possible detections, the most promising is the PSR J2007+3120 system, which may contain at least two planets with masses of several Earth masses with orbital periods of 1.9 and 3.6 years, respectively, the authors noted.
The authors also add that they did not find a predominance in pulsar systems of planets with a mass or orbital period from a particular range, however, they registered a predominance of planets, lying on elliptical orbits instead of circular ones.
This may point to a different mechanism for planet formation in pulsar systems compared to planet formation in conventional star systems, Nitu and her colleagues note.
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