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Circumtriple planet
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<p>A circumtriple planet is a celestial mass that is hypothesized to be orbiting not only a single star but three stars at the same time. Scientists observing the star system <a href="/facts/GW_Orionis/rdIQVzLm">GW Ori</a>, which is a huge disk of dust and gases about 1,300 light years away from Earth, suspect that there may be a circumtriple planet orbiting the three stars. They observed a gap in the vast dust cloud and they hypothesize that there may be a planet in this gap. The planet itself has not been seen but its influence may explain gravitational oddities within the star system. By using computer modeling, some scientists believe that a Jupiter-sized planet may be able to explain the star system's rings and strange behavior, according to one account. If so, this may be the first known example of a circumtriple planet in the universe. </p><p>In 2015, the planet or brown dwarf, 2MASS J0019-6226 was found to orbit the three stars in the HIP 1481 system. It is believed to be about 15 times the mass of <a href="/facts/Jupiter/95m7XjMT">Jupiter</a> and is roughly 155,000 <a href="/facts/Astronomical_unit/gjsbu5xU">au</a> away. 2MASS J0019-6226 has a size of about 1.6 RJ. If it is a planet, it would be the first confirmed circumtriple planet and the planet with the largest semi-major axis. </p><p>In 2022, evidence of a very small planet was found around the triple system <a href="/facts/PSR_J0337%252B1715/y8sm6ooD">PSR J0337+1715</a>. In 2024, additional data allowed the planet's mass to be constrained to 0.0041±0.003 <a href="/facts/Earth_mass/G74DaKFv"><i>M</i>🜨</a>, making it one of the smallest objects directly detected outside the Solar System so far. </p><p>In 2024, the substellar object <a href="/facts/Gliese_900_b/hf1eplx2">CWISE J235827.96–521813.4</a> was detected to be bound to the <a href="/facts/Gliese_900/hf1eplx2">Gliese 900</a> triple star system at a distance of 12000 <a href="/facts/Astronomical_unit/gjsbu5xU">AU</a>, thus becoming the planet with the longest orbital period and first confirmed circumtriple planet. </p><p>Circumtriple planets are likely to be an extremely rare phenomenon in the universe. Studying them could add to human understanding of how planets form. </p>