Land of Three Suns

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This artist's animation shows the view from a hypothetical moon in orbit around the first known planet to reside in a tight-knit triple-star system. The gas giant planet, discovered using the Keck I telescope atop Mauna Kea in Hawaii, zips around a single star that is orbited by a nearby pair of pirouetting stars. Because the stars in this triple system are bunched together, sunsets on the planet - or on any moons that might exist around the planet - would be spectacular. In this movie, sunset is seen through the tenuous atmosphere of a hot, baked hypothetical moon. As the suns dip below the horizon, the gas giant comes into view. The moon's landscape remains illuminated by sunlight reflected off the planet. Both the planet and moon would be so hot that even in shadow their surfaces would glow. The suns' colors and sizes reflect their masses, temperatures and distances to the planet. For example, the first star shown setting over the horizon is the closest, most massive and hottest of the trio, so it is depicted as large and white. The second star is farther away, less massive and cooler than the first, appearing smaller and yellow. The final star is at the same distance as the second, but it is still less massive and cooler, appearing even smaller and orange-red in color. Our Sun is a bit cooler than the hottest star of the system. This rambunctious stellar family is called HD188753 and is located 149 light-years away in the constellation Cygnus. Its planet, called HD 188753 Ab, is 1.14 times the mass of Jupiter. Image credit: NASA/JPL-Caltech

Circus Family of Stars

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This artist's animation shows the clockwork-like orbits of a triple-star system called HD 188753, which was discovered to harbor a gas giant, or "hot Jupiter," planet. The planet zips around the system's main star (yellow, center) every 3.3 days, while the main star is circled every 25.7 years by a dancing duo of stars (yellow and orange, outer orbit). The star pair is locked in a 156-day orbit. This eccentric star family is a cramped bunch; the distance between the main star and the outer pair of stars is about the same as that between the Sun and Saturn. Though multiple-star systems like this one are common in the universe, astronomers were surprised to find a planet living in such tight quarters. One reason for the surprise has to do with theories of hot Jupiter formation. Astronomers believe that these planets begin life at the outer fringes of their stars, in thick dusty disks called protoplanetary disks, before migrating inward. The discovery of a world under three suns throws this theory into question. As seen in this animation, there is not much room at this system's outer edges for a hot Jupiter to grow. The discovery was made using the Keck I telescope atop Mauna Kea mountain in Hawaii. The triple-star system is located 149 light-years away in the constellation Cygnus. The sizes and orbital periods in the animation are not shown to scale. The relative motions are shown with respect to the main star. Image credit: NASA/JPL-Caltech

Full Resolution JPG (3000x2400)

This artist's concept shows an edge-on view of the triple-star system. Sifting the Light of Three Suns Full Resolution JPG (3000x2400) This graph shows the "wobble" of a star being tugged on by a planet, called HD 188753 Ab. The planet was discovered via the radial velocity technique, in which a planet's presence is inferred by the motion, or wobble, it causes in its parent star. Stellar motion is plotted here as changes in velocity (y-axis) versus time (x-axis). Unlike most planetary wobbles, this one comes from a star that is circled by a nearby pair of stars. In other words, the planet orbits a single star that is part of a close-knit triple-star system. Because the starlight from this cramped bunch blends together, the task of sifting through the light to find the planet's signature was more difficult. This challenge was overcome with the help of detailed models of the triple-star system's light. Data from those models resulted in precise velocity measurements of the star circled by HD 188753 Ab, as shown in the graph above. HD 188553 Ab is a gas giant planet, about 1.14 times the mass of Jupiter, with an orbital period of 3.3 days. It was detected using the Keck I telescope atop Mauna Kea mountain in Hawaii. Image credit: NASA/JPL-Caltech