A team of scientists from Cornell University has created a reference catalog detailing the "light-fingerprints" of worlds orbiting our Sun, in the hope that it will help future telescopes to uncover the true natures of distant exoplanets. The researchers characterized a total of 19 celestial bodies from our cosmic backyard, including all nine planets, major moons such as Enceladus, as well as the dwarf planets Ceres and Pluto.

The new catalog details the light reflected by the surface of the solar system bodies, known as their geometric albedos, as well as their calibrated spectra. A diverse set of bodies were chosen for the study, including gas giants, icy and potentially life-harbouring moons, volcanic worlds and enigmatic satellites such as Titan. The researchers also explored how the spectra and albedos of the worlds would change if they were bathed in the light of stars different in nature from our own Sun.

"We use our own solar system and all we know about its incredible diversity of fascinating worlds as our Rosetta Stone," said co-author Lisa Kaltenegger, associate professor of astronomy and director of the Carl Sagan Institute. "With this catalog of light-fingerprints, we will be able to compare new observations of exoplanets to objects in our own solar system – including the gaseous worlds of Jupiter and Saturn, the icy worlds of Europa, the volcanic world of Io and our own life-filled planet."

The team believes that their work will allow astronomers using the next generation of terrestrial and orbital observatories to better characterize distant worlds by comparing the spectra of exoplanets collected by direct observation with that of worlds we can study (relatively) up close.

The ability to put exoplanet readings in context will allow scientists to select exoplanets for follow-up observations that will be quicker and easier to understand. Conversely, the resource could highlight worlds whose secrets would be far more time-consuming to unravel.

For the latter scenario the team gave Venus as an example. Venus is a rocky world, sometimes described (poorly) as Earth's twin, however, a runaway greenhouse effect is believed to have endowed the planet with the super dense atmosphere that astronomers observe today.

Light from our Sun reflects off the dense carbon dioxide atmosphere of Venus, rather than its underlying surface, giving it a spectral appearance of an icy world, effectively masking its true nature. Worlds such as this require long-term observations in order to reveal their true nature. Therefore, if a telescope is able to obtain a spectra of an exoplanet that closely matches the catalog values of Venus, then they know that it will take a lot of precious telescope time to properly understand the alien world.

Currently, the next generation of orbital telescope and observatories that will best complement the new catalog are still years from completion. The launch of the ambitious James Webb Space Telescope was recently delayed to no earlier than March 30, 2021, following the findings of an independent review board. Meanwhile, terrestrial observatories are even further away.

First light for the European Southern Observatory's Extremely Large Telescope (ELT) is not set to take place until 2024, while commissioning for the Giant Magellan Telescope (GMT) is expected to begin the same year. Of course, the 2024 dates are best-case scenarios, and projects as ambitious and complex as the GMT and ELT are prone to unforeseen delays and technological challenges.

High and low-resolution versions of the data contained in the catalog have already been published on the Carl Sagan Institute website.

A paper detailing the research has been published in the journal Astrobiology.

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