An exoplanet that orbits three stars in a highly unusual configuration and is only 16 million years old has been discovered through the technique of direct imaging approximately 340 light years from Earth in the constellation Centaurus.
Titled HD 131399Ab, the planet orbits the brightest and most massive of the stars, labeled Star A, from a distance of 82 astronomical units (AU, with one AU equal to about 93 million miles, or the Earth-Sun distance), about twice the distance between the Sun and Pluto in our solar system.
The system’s other two stars, Star B and Star C, both dimmer and less luminous than Star A, are located close to one another. These smaller stars technically orbit Star A and the planet.
In most multi-star systems, planets orbit close to one of the stars with the others being too far away to gravitationally affect the planets.
That is not the case in this system, where all three stars gravitationally tug on HD 131399Ab.
Star A is 80 percent more massive than our Sun and 7.8 percent brighter. However, from the planet, the star appears only about 0.00116 times as bright as the Sun does from Earth though it is still 464 times brighter than the full Moon as seen from our planet.
Star B has a mass approximately that of the Sun, but it is only 0.87 times as bright. The smaller Star C has a mass about 60 percent that of the Sun and is just 0.17 times as bright.
Depending on the planet’s position in its orbit around Star A, the two smaller stars are located between 300 and 400 AU from it.
“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 University of Arizona doctoral student Kevin Wagner, who discovered HD 131399Ab, in a press release.
During the period when all three stars are visible in the planet’s sky, three sunrises and three sunsets are visible from its surface every day.
“As the planets orbit, and the stars grow farther apart each day, they reach a point where the setting of one coincides with the rising of [the other two]–at which point the planet is in near-constant daytime for about one-quarter of its orbit, or roughly 140 Earth years,” Wagner explained.
Approximately four times the mass of Jupiter, the planet has a temperature of about 1,070 degrees Fahrenheit (580 degrees Celsius).
It was discovered via direct imaging, in which observers directly see a planet’s light through a telescope, via the Spectro-Polarimetric High-Contrast Exoplanet Research Instrument (SPHERE), which can detect the heat from planets due to its sensitivity to infrared light.
The discovery is the subject of a paper published in the July 7 issue of the journal Science.
Source:: Google Science]]>