The cosmic body is believed to be relatively young, about 16 million years old, which makes it one of the youngest planets discovered outside our solar system to date.
Its mass is believed to be four times that of the gas giant Jupiter, which is our solar system's largest planet.
It orbits the brightest of the three stars on a very long and wide path."For about half of the planet's orbit, which lasts 550 Earth-years, three stars are visible in the sky, the fainter two always much closer together, and changing in apparent separation from the brightest star throughout the year," said first author Kevin Wagner, a first-year PhD student who discovered HD 131399Ab.
"For much of the planet's year the stars appear close together, giving it a familiar night-side and day-side with a unique triple-sunset and sunrise each day," Wagner added.
"As the planet orbits and the stars grow further apart each day, they reach a point where the setting of one coincides with the rising of the other." The result is "near-constant daytime for about one-quarter of its orbit, or roughly 140 Earth-years".
The astronomy team spotted the planet using the SPHERE instrument on the European Southern Observatory's (ESO) Very Large Telescope in Chile.SPHERE is one of the world's most advanced instruments dedicated to finding planets around other stars.SPHERE stands for Spectro Polarimetric High Contrast Exoplanet Research Instrument.It is sensitive to infrared light, making it capable of detecting the heat signatures of young planets.