Worlds beyond our solar system

One of the main reasons why extrasolar planets are difficult to observe is because they are fainter than the stars they orbit. In addition, the host stars give off light that obscures them from direct observation. As a result, the first discovery was not made until 1992 when astronomers using the Arecibo Observatory in Puerto Rico observed several planets orbiting the pulsar PSR B1257+12.

Since then, some extrasolar planets were directly observed with telescopes. However, the vast majority has been detected through indirect methods such as the transit method. The EU-funded DICE (Direct imaging of extrasolar planets from LBT and VLT to E-ELT) project paved the way for new discoveries using the direct imaging capabilities of ground-based telescopes in Europe and the United States.

DICE scientists completed surveys on gas giant planets around nearby stars. Specifically, they investigated the formation and evolution of planetary systems in our galaxy. Massive stars that are relatively young in comparison to our own Sun were the starting point. Next, they looked at stars similar to HR 8799 with four planets orbiting around it.

To increase the sensitivity of direct imaging of extrasolar planets, DICE scientists developed two new coronagraphs. These angular filters that suppress the halo around the bright host stars were used at the Very Large Telescope (VLT) in Chile and the Large Binocular Telescope (LBT) in the United States. Thanks to their improved design, it was possible to acquire images of the extrasolar planet β Pictoris b and a low-mass protoplanet.

Project scientists also developed new adaptive optics techniques that have led to new insight into how wide-field spectroscopy could be carried out on extremely large telescopes. A network of small telescopes distributed around an extremely large telescope can acquire images along multiple different lines of sight by looking in the direction of bright guide stars.

With state-of-the-art astronomical instruments of the European Extremely Large Telescope (E-ELT), DICE scientists plan to continue the hunt for extrasolar planets. The discovery of Earth-like planets also intensifies interest in the search for extraterrestrial life, particularly regarding those that orbit in the host star's habitable zone.