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- In 1992, astronomers found the first known exoplanet<\/strong>, or world orbiting another star. In this case, it orbited a pulsar, or rapidly spinning dead star.<\/li>\n
- Now astronomers have found a new possible exoplanet around a pulsar<\/strong> some 4,200 light-years away.<\/li>\n
- It will be the smallest known exoplanet found to date<\/strong>, if confirmed. It is smaller and less massive than Earth\u2019s moon.<\/li>\n<\/ul>\n
Smallest exoplanet candidate orbits a pulsar<\/h3>\n
Just like the planets in our own solar system, exoplanets around other stars come in a wide range of sizes. Now, researchers in Europe say they\u2019ve found what might be the smallest exoplanet to date. And it orbits a pulsar! The researchers said on January 20, 2025, they calculated the possible planet as smaller than Earth\u2019s moon, perhaps about the size and mass of Pluto.<\/p>\n
Incidentally, when astronomers discovered the first-ever exoplanet in 1992, it also orbited a pulsar (PSR B1257+12). A pulsar is a rapidly spinning neutron star. A neutron star is the small, incredibly dense remnant of a much more massive star that exploded in a supernova.<\/p>\n
2025 EarthSky lunar calendar is available now. A unique and beautiful poster-sized calendar with phases of the moon for every night of the year. Get yours today!<\/p>\n
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Have We Discovered The Smallest Extra-solar Planet?astrobiology.com\/2025\/01\/have\u2026 #astrobiology #astronomy #exoplanet<\/p>\n
\u2014 Astrobiology (@astrobiology.bsky.social) 2025-01-23T15:12:16.348Z<\/p>\n<\/blockquote>\n
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This may be the strangest planet yet discovered. It seems to be a Pluto-size world circling the remains of three dead stars: two white dwarfs & a pulsar, as massive as the Sun but no bigger than Brooklyn. If confirmed, it is also the smallest exoplanet known. ??astrobiology.com\/2025\/01\/have\u2026<\/p>\n
\u2014 Corey S. Powell (@coreyspowell.bsky.social) 2025-01-27T23:27:10.147Z<\/p>\n<\/blockquote>\n
Meet pulsar PSR J0337+1715<\/h3>\n
Astronomers first discovered the pulsar, called PSR J0337+1715, in 2014. It\u2019s part of a three-star system, consisting of the pulsar and two white dwarfs. All three stars are within an outer perimeter about the same size as Earth\u2019s orbit around the sun.<\/p>\n
The pulsar is 4,200 light years away in the constellation Taurus the Bull. It is the first one ever found in a triple star system.<\/p>\n
![\"2](\"https:\/\/earthsky.org\/upl\/2025\/02\/pulsar-PSR-J03371715-orbits-Paris-Observatory-January-20-2025.png\")
View larger. | Artist\u2019s depiction of the orbits of the pulsar, the 2 white dwarfs and possible planet orbiting all 3 stars. Image via Guillaume Voisin\/ Fabrice Mottez\/ Paris Observatory (CC BY SA).<\/figcaption><\/figure>\n Smallest exoplanet found so far?<\/h3>\n
Mathematical models suggested there might be an additional body in the system. But this isn\u2019t a fourth star. Instead, it appears to be a planet. Calculations suggest it is smaller and less massive than our moon, perhaps about the size of Pluto.<\/p>\n
It\u2019s still possible that it is a random signal from the pulsar itself that mimics the signal of a planet. But the amplitude of the signal is unusually large. The planet, if real, also orbits the whole triple system in a huge orbit.<\/p>\n
1st exoplanets discovered were pulsar planets<\/h3>\n
Planets around pulsars seem to be a lot less common than around still-active stars. So far, astronomers have only found about half a dozen of them as compared to over 5,000 other exoplanets. Yet, as it happened, the first exoplanets that astronomers ever found were orbiting a pulsar! In 1992, astronomers Aleksander Wolszczan and Dale Frail discovered not one, but two exoplanets orbiting the pulsar PSR1257+12.<\/p>\n
This pulsar, named Lich by the International Astronomical Union (IAU), is a rapidly spinning millisecond pulsar. It rotates once every 6.2 milliseconds. A millisecond is 1\/1000 of a second.<\/p>\n
The researchers measured the timing of pulses coming from the pulsar, 4,040 of them. They noticed that the arrival times of the pulses varied a bit. The variations aligned with a combination of two periods: 66.6 days and 98.2 days. The astronomers determined the explanation was two low-mass planets. Their orbits were similar to that of Mercury and both of their masses were just a few times that of Earth.<\/p>\n
There was also evidence for a possible third planet on a larger orbit, but it was not confirmed.<\/p>\n
Pulsar planets are likely newer planets<\/h3>\n
Scientists think the planets around pulsars did not form with the stars, but instead formed in the aftermath of their deaths. They would have formed in the accretion disk of the exploded star. If they had been planets orbiting the original star when it exploded, they likely would not have survived.<\/p>\n
Bottom line: Astronomers in Europe said they have discovered what might be the smallest exoplanet found so far. If real, it is smaller than our moon and orbits a pulsar.<\/p>\n
Source: Explanation of the exceptionally strong timing noise of PSR J0337+1715 by a circum-ternary planet and consequences for gravity tests<\/p>\n
Via Paris Observatory<\/p>\n
Read more: A super-Venus exoplanet (with a watery name)<\/p>\n
Read more: Can we detect dark matter using light from pulsars?<\/p>\n
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\n - Now astronomers have found a new possible exoplanet around a pulsar<\/strong> some 4,200 light-years away.<\/li>\n