The Very Large Telescope (VLT) housed at the European Southern Observatory in Chile just got an impressive upgrade, giving it the largest collection area of any optical telescope in the world. This upgrade consisted of light integration from its four 27-foot telescopes into an entirely new instrument. As a result, scientists can use the VLT to spot small, rocky planets orbiting distant stars. Previously, it had only been able to make observations using light from one of the units.

This new instrument is called the Echelle Spectrograph for Rocky Exoplanet and Stable Spectroscopic Observations, or ESPRESSO. It works by gathering and processing the light from each of the four VLT units using a variety of lenses, mirrors, and prisms. This process helps it gain more photons of light. In turn, smaller, fainter objects become brighter, clearer, and easier to see. Engineers designed the telescope to accept the light from all four units or one at a time, to offer observers greater flexibility.

ESPRESSO has high resolving power, which means the scope is capable of distinguishing between small objects located close together in the sky. Professional telescopes tend to have high resoling power, whereas ones for home use tend to have very low resolving power. High resolving power is necessary to help identify which objects are the rocky exoplanets scientists are searching for.

The scope serves a secondary yet equally as important scientific goal. ESPRESSO is also designed to observe quasars, which have been previously hard to identify. Information about these distant quasars may resolve many questions about basic physics, opening up countless other fields of study. The combined light form each of the four telescopes as well as its high resolving power work together to make ESPRESSO perfect for this purpose as well.