Catalog identifies “light fingerprints” of 19 solar system bodies

Resource will be reference for categorizing exoplanets.

A new catalog compiled by scientists at Cornell University identifies the unique “light fingerprints” of 19 solar system objects, including 10 planets and nine moons for use as a resource to better characterize exoplanets.

Planets and moons have unique “fingerprints” in the form of their calibrated light spectra and geometric albedo, or sunlight reflected from their surfaces.

The 19 objects selected were chosen for their highly diverse compositions and characteristics and include rocky, gaseous, and dwarf planets, frozen worlds, and objects that spew lava.

Titled “A Catalog of Spectra, Albedos, and Colors of Solar System Bodies for Exoplanet Comparison,” the catalog has been published in the journal Astrobiology and will be highlighted on the December cover of its print edition.

Its contents are available to the public for free on the website of the Carl Sagan Institute.

Objects included in the resource are the solar system’s four terrestrial planets, Mercury, Venus, Earth, and Mars; its four gas giants, Jupiter, Saturn, Uranus, and Neptune; two dwarf planets, Ceres and Pluto; Earth’s Moon; Jupiter’s moons Io, Callisto, Europa, and Ganymede; and Saturn’s moons Titan, Rhea, Dione, and Enceladus.

“We use our own solar system and all we know about its incredible diversity of fascinating worlds as our Rosetta Stone,” explained Lisa Kaltenegger 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 world of Europa, the volcanic world of Io, and our own life-filled planet.”

In addition to showing high- and low-resolution images of the data from which the scientists characterized these 19 worlds, the catalog also shows how the colors of each world would change if it orbited various stars other than the Sun.

Without high-resolution spectra, some exoplanets will prove difficult to categorize. For example, if Venus were observed from another solar system, the way sunlight reflects off its thick carbon dioxide atmosphere would give it the colors of an icy world even though it is actually a rocky planet.

“Planetary science broke new ground in the ’70s and ’80s with spectral measurements for solar system bodies. Exoplanet science will see a similar renaissance in the near future,” said Jack Madden of the Carl Sagan Institute, who led the study.

“The technology to directly collect the light from Earth-sized planets around other stars is currently in a clean room waiting to be assembled and trained on the right target. With the upcoming launch of the James Webb Space Telescope (JWST) and the current construction of large ground-based telescopes such as the Giant Magellan Telescope and the Extremely Large Telescope, we are entering a new age of observational ability, so we need a reference catalog of all the planets and moons we already know, to compare these new exoplanet spectra to.”

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