Un grupo internacional, ha recopilado información contundente que muestra que los planetas de composición rocosa y posiblemente con agua, son muy comunes en nuestra galaxia. Se llegó a esta conclusión analizando la composicion de Enanas Blancas (estrellas que eran como nuestro Sol), la cual estaba "contaminada" por elementos mas pesados que el Helio y el Hidrógeno, astronómicamente llamados "metales" (incluso el Oxígeno se le denomina metal bajo esta regla), dando las bases de que tienen o tuvieron cuerpos rocosos y posiblemente con agua. Las enanas blancas son las estrellas más comunes en nuestra galaxia.
Extracto del artículo a continuacion (ingles):
White dwarf stars (more than 90%) of all stars in the Milky Way, including our Sun. Because they should have essentially pure hydrogen or pure helium atmospheres, if heavier elements — in astronomy described as "metals," examples including calcium, magnesium, and iron — are found, then these must be external pollutants. For decades, scientists believed that the interstellar medium, the tenuous gas between the stars, was the source of metals in these polluted white dwarfs.
Farihi and his team used data from the Sloan Digital Sky Survey (SDSS), a project that aims to survey the sky in infrared light, imaging more than 100 million objects and following up one million of these by obtaining their spectra (dispersing the light by color).
By examining the positions, motions, and spectra of the white dwarfs identified in the SDSS, Farihi and his team show that the interstellar medium as the source is no longer a viable theory. Instead, rocky planetary debris is almost certainly the culprit in most or all cases.
The new work indicates that at least 3 percent and perhaps as much as 20 percent of all white dwarfs are contaminated in this way, with the debris most likely in the form of rocky minor planets with a total mass of about that of an 87-mile-diameter (140 kilometers) asteroid.
This implies that a similar proportion of stars like our Sun, as well as stars that are a little more massive like Vega and Fomalhaut, build terrestrial planetary systems. Astronomers are thus playing the role of celestial archaeologists by studying the "ruins" of rocky planets and their building blocks.