Searching for Earth-Like Worlds Just Got Easier Thanks to This ESPRESSO Instrument

The search for Earth-like planets just got a major upgrade: The European Southern Observatory's Very Large Telescope (VLT) in Chile successfully integrated the light from all four of its 8.2-meter (27 feet) unit telescopes into a new instrument, making VLT the optical telescope with the largest collecting area in the world.

The upgrade will make it easier for scientists to use the observatory to search for faint, rocky planets around distant stars, ESO representatives said in a statement.

The instrument is called ESPRESSO (Echelle Spectrograph for Rocky Exoplanet and Stable Spectroscopic Observations). Each of the VLT units sends its light to the instrument using mirrors, prisms and lenses. ESPRESSO can use the light from either all four telescopes at once or just one individual telescope. That design is intended to provide more flexibility in observing time, ESO representatives said. [Amazing Space Views of ESO's Very Large Telescope (Photos)]

The ESPRESSO instrument on the European Southern Observatory's Very Large Telescope (VLT) in Chile successfully combined light from four 8.2-meter unit telescopes for the first time, making VLT the optical telescope with the largest collecting area in the world. (Image credit: L. Calçada/ESO)

Another instrument, called the VLT Interferometer, commonly combines the light from all four unit telescopes, but ESPRESSO does it differently. Interferometry combines multiple telescopes to make observations. The effective size of the telescope "mirror" is the same as the distance between the individual telescopes. Interferometry also takes the phase of an object's light waves into account to form an image. 

ESPRESSO, by contrast, is designed to exploit the light-gathering power of the individual telescopes. It has the light-collecting power of a 16-meter (52 feet) telescope. Light gathering is important for telescopes because, as they receive more photons of light, fainter objects appear brighter. Bigger telescopes typically see distant objects such as galaxies more easily because they have more light-gathering power.

These images from the ESPRESSO instruments at the European Southern Observatory's Very Large Telescope capture the first-light moment for the new astronomy tool. (Image credit: ESO/D. Mégevand)

The objects ESPRESSO can resolve are at the power of an 8-meter (26 feet) telescope (the same as each individual telescope). Resolving power refers to the ability of a telescope to separate objects that are close together in the sky. A telescope that professionals use tends to have more resolving power than an amateur one, allowing professionals to see stars more clearly in multiple-star systems, for example.

"This impressive milestone is the culmination of work by a large team of scientists and engineers over many years," project scientist Paolo Molaro said in the statement. "It is wonderful to see ESPRESSO working with all four unit telescopes, and I look forward to the exciting science results to come," added Molaro, who is on the research staff of the Astronomical Observatory of Trieste in Italy.

Astronomers celebrated the first light of the ESPRESSO instrument on ESO's Very Large Telescope with, appropriately, celebratory espresso. (Image credit: ESO/D. Mégevand)

ESPRESSO has a second major scientific goal besides looking for Earth-like worlds: to seek variability in fundamental physics constants. ESPRESSO will observe faint and faraway quasars to uncover more about basic physics, and the combined light of the four telescopes will greatly benefit it in its observations, ESO representatives said.

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Elizabeth Howell
Staff Writer, Spaceflight

Elizabeth Howell (she/her), Ph.D., is a staff writer in the spaceflight channel since 2022 covering diversity, education and gaming as well. She was contributing writer for for 10 years before joining full-time. Elizabeth's reporting includes multiple exclusives with the White House and Office of the Vice-President of the United States, an exclusive conversation with aspiring space tourist (and NSYNC bassist) Lance Bass, speaking several times with the International Space Station, witnessing five human spaceflight launches on two continents, flying parabolic, working inside a spacesuit, and participating in a simulated Mars mission. Her latest book, "Why Am I Taller?", is co-written with astronaut Dave Williams. Elizabeth holds a Ph.D. and M.Sc. in Space Studies from the University of North Dakota, a Bachelor of Journalism from Canada's Carleton University and a Bachelor of History from Canada's Athabasca University. Elizabeth is also a post-secondary instructor in communications and science at several institutions since 2015; her experience includes developing and teaching an astronomy course at Canada's Algonquin College (with Indigenous content as well) to more than 1,000 students since 2020. Elizabeth first got interested in space after watching the movie Apollo 13 in 1996, and still wants to be an astronaut someday. Mastodon: