First estimate of the mass of an Earth-like exoplanet

The exoplanet Kepler-78b (a planet located outside our solar system) is one of several that astronomers have identified in recent years. In particular, it is the first for which the mass and diameter are known. Two international research teams recently published these results in the journal Naturean FCT-supported researcher from the University of Porto's Astrophysics Center (CAUP) is part of one of these teams. 

Kepler-78b is located in the constellation Cygnus, about 400 light years from Earth. Due to its density and radius, it is the exoplanet most similar to Earth, having similar rock and iron compositions. However, it is 40 times closer to its star than Mercury is to the Sun, which causes temperatures to reach 1800 to 3300°C. In fact, it's surprising that the planet exists at all, and current models predict that it will collide with its star in the next 3 billion years. 

The size and orbit of the planet Kepler-78b were initially determined using NASA's Kepler telescope. The two teams that have now published the mass and diameter of the exoplanet combined data from the telescope with that from another technique, which measures the gravitational effect of a planet on the speed with which its star approaches or moves away from the planet.  

Pedro Figueira, from CAUP, emphasizes the importance of these results, "It was not easy to extract confirmation from the data that the signal found by Kepler was due to a planet. It was only after several months of work that we were able to identify the planet's signal (...) it is a very clear testimony to the high level of current planetary astronomy and the impressive progress made in recent years."