These images feature the first three Exoplanets discovered around Gliese 876. Planets b and c are remarkable in that they are perpetually locked in sync with periods of 60 and 30 days. Planet d, when announced, was the lowest mass planet discovered to that point: just 6-8 Earth masses and a radius of only 1.8x that of the Earth. A hot world very close to its star, it is thought to have a thick cloud layer with possible active volcanism visible through breaks in the clouds. Astronomy Picture of the Day on June 14, 2005
Five confirmed planets orbit 55 Cancri. The innermost planet, with 14.2 Earth masses and a 2.8 day orbit, was discovered in 2004. The next planet out, the first known in this system and found in 1996, has a 14.7-day orbit. Then comes planet "c", with an orbit of 44.3 days. The fourth world is the newest discovery, having 45 Earth masses and an orbit of 260 days. The farthest world out has an orbit comparable to Jupiter's. While not an exact analog, it is the closest astronomers have come to date in finding a system that resembles our own. Shown here, close up, is the most distant planet with a hypothetical icy moon. The other four confirmed worlds in this system are shown as small spheres to the left and right of the parent star. Astronomy Picture of the Day on June 14, 2002
This painting of the 55 Cancri system was created in 1996 after the discovery announcement of the first Exoplanet. At that time, the outermost planetnow confirmedwas only suspected, and there was no hard data on the others. The first two discovered worlds are depicted here, with a large, cratered moon accompanying the outer planet. Shown in the distance is a red dwarf, the second star in this binary system.
Gliese 436 b Gliese 436 b, with an interior structure of a hybrid super-Earth/Neptune, circles a red M dwarf star just 30 light years from Earth. An observed transit, depicted in the lower right-hand box, allowed astronomers to pin down the mass of 22.4 Earths and to determine that the radius and density are similar to Neptune's. Hydrogen and helium, likely present in the atmosphere, could scatter blue light preferentially by Raleigh scattering. Clouds reflect the orange-red light of the star.
Two Jupiter-like planets orbit the star 47 Ursae Majoris. They have nearly the same mass ratio as our own Jupiter and Saturn and travel in nearly circular orbits at distances far beyond the distance that Mars orbits our Sun. At one time theorists suspected that low mass, Earth-like planets might exist around 47 Ursae Majoris in its habitable zone. More recent study casts doubt on such a possibility. This view is from an imagined satellite of the outermost planet. Two other planets are shown also: the confirmed inner planet and an imagined (but undetected) pale blue dot close to the stara possible "water world." Astronomy Picture of the Day on August 17, 2001