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Researchers Create Reference Catalog of Solar System for Exoplanet Comparison

Detectives who are earthbound depend on fingerprints to solve their cases. At present, astronomers can execute the same, with the help of “light-fingerprints” in the place of skin grooves to bring to light the mysteries of exoplanets.

Earth with the albedo plotted over it. (Image credit: Jack Madden/NASA)

Scientists from the Cornell University have developed a reference catalog with the help of calibrated spectra and geometric albedos (the light reflected by a surface) of 19 of the most distinctive bodies in our solar system: all eight planets, from rocky to gaseous; two dwarf planets, one in the asteroid belt (Ceres) and one in the Kuiper belt (Pluto); and nine moons, from frozen to lava spewing.

Comparison of the observed spectra and albedos of exoplanets with this catalog of our own home planetary system will enable researchers to characterize them with respect to the broad array of rocky, icy, and gaseous realms in our home system.

The paper titled “A Catalog of Spectra, Albedos and Colors of Solar System Bodies for Exoplanet Comparison” was published online in the Astrobiology journal on July 31, 2018, and will be featured on the print edition’s cover in December.

We use our own solar system and all we know about its incredible diversity of fascinating worlds as our Rosetta Stone. 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.

Lisa Kaltenegger, Associate Professor of astronomy & Director of the Carl Sagan Institute

The catalog is freely available on the Carl Sagan Institute website and includes high- and low-resolution versions of the data, which reveals to the astronomers the impact of spectral resolution on the identification of an object. Moreover, the catalog provides examples of the way in which the colors of the 19 solar system models would vary if they orbited stars other than our sun.

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. 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 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.

Jack Madden, Lead Author

The catalog will allow researchers to give precedence to time-intensive, high-resolution observations of extrasolar planets and moons. It will also allow them to understand the kind of realms that will not be very easy to categorize in the absence of high-resolution spectra. For instance, although Venus is a rocky planet, sunlight is reflected from its dense carbon dioxide atmosphere instead of its rocky surface, hence the colors observed by astronomers from such a planet are analogous to those of an icy world. On the outer edge of the habitable zone, it is possible that rocky exoplanets will have dense atmospheres similar to Venus. Such realms will necessitate long observations for correct characterization.

Examining our solar system from the vantage point of a distant observer is an illuminating exercise,” stated Madden.

By unraveling the mysteries of the objects in our own solar system we can glimpse the secrets of these new worlds we are finding,” stated Kaltenegger.

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