A milestone astronomical discovery was announced on January 10th 2011 by NASA's Kepler team at the American Astronomical Society's annual meeting in Seattle. Kepler's space telescope has discovered a new planet. Although it has only been very recently that scientists have been able to confirm the existence of planets beyond Earth's own solar system, such announcements have quickly become commonplace. Kepler 10b is a remarkable discovery, however, because it marks the first time that an 'exoplanet' has been confirmed as having an Earth-like rock-based structure, rather than being a gaseous planet. Kepler 10b's diameter is approximately 1.4 times that of Earth, with 4.6 times more mass.
In other words, the discovery of Kepler 10b confirms the existence outside the solar system of planets similar to our own. Planets which could, in theory, support life.
Not that Kepler 10b itself is likely to support life, of course. According to the Kepler team, it is so close to its star that the daytime surface temperature is thought to exceed 1,300C. Now that the methods have been established to locate and identify rocky exoplanets, however, it can only be a matter of time before more likely prospects for interstellar life are discovered.
Kepler 10b was discovered and confirmed by a combination of techniques. First, the Kepler telescope used a technique called 'transiting' - when an exoplanet's orbit takes it between its star and Earth, a proportion of its light is blocked, hinting at the presence of a planet. The amount of light which is blocked is tiny, but still measurable, and allows scientists to measure with confidence the radius of a new planet.
The find was then confirmed by an observatory based in Hawaii, which measured the extent to which Kepler 10b was pulling on its parent star as it orbited, giving indications as to the exoplanet's likely mass.
Finally, asteroseismology was employed - a technique which detects oscillations within stars which affect the frequency of a star's light and imply a star's size.
With the size of the star established, along with the radius and gravitational properties of the exoplanet, it became a comparatively simple step to calculate the planet's density and deduce that it must indeed be a solid planet. Previous candidates for the first rocky exoplanet have been announced, such as Corot-7b in 2009, but were later discounted due to fluctuations in optical and magnetic activity from the planets' host stars which made the measurements unreliable. Kepler 10b's star, 560 light years away, is a much older sun, with none of this instability, so this is definitely the first confirmed find.
As measuring equipment becomes ever more sensitive, and techniques become ever more refined, it seems inevitable that we will see more of these solid exoplanets cropping up in the ever-increasing field of planetary bodies discovered outside our solar system. And the more planets that turn up, the more likely that some will be in the theoretical patch of a star's orbit which could support life as we know it.
The discovery of Kepler 10b and its structure is perhaps one of the most crucial steps along the way to the greatest discovery of all - that there is life on other worlds.