Scientists are writing a recipe for the perfect planet — a place not too cold, not too hot, not too toxic, and chemically suitable for life as we know it — as they brace for a torrent of new discoveries about potentially habitable alien worlds.
There may be billions of planets hospitable to life in the Milky Way galaxy alone, dozens of them much closer to Earth than previously suspected, several new star surveys and statistical studies suggest.
"We could be in a situation where there are a billion objects that conceivably match expectations for habitability — the right-sized planet around the right sort of star," says Caleb Scharf, director of astrobiology at Columbia University in New York. "How do you categorize them in a tree of possibilities for life?"
To help guide future study and exploration, independent researchers are for the first time developing formulas to rank planets by their similarity to Earth and their suitability for life.
They want a set of technical parameters that can be codified in a single number, like earthquake magnitude or tornado intensity.
The most basic of the indexes rates a world's suitability for life based on its place within a habitable zone, which is calculated by a planet's distance from its parent star, the star's luminosity and temperature.
Astronomers call the most promising of these places "Goldilocks planets," because they orbit in a temperate zone not too hot and not too cold to support liquid water-essential for carbon-based life as we know it.
The concept, widely used as a rule of thumb by astronomers, was codified last year by Abel Mendez, director of the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo, and his colleagues into a more formal Habitable Zone Distance scale.
Read the full story in the Wall Street Journal
Learn more about the search for life in space at SPIE Astronomical Telescopes + Instrumentation (1-6 July) and SPIE Optics + Photonics (12-16 August). Offerings at these two symposia include conferences, courses, panel discussions, and these special events:
- Exoplanets: Unraveling a New Paradigm, 2 July plenary talk at SPIE Astronomical Telescopes + Instrumentation, by Didier Queloz of Geneva University
- James Webb Space Telescope: Science Update and Status, 2 July plenary talk at SPIE Astronomical Telescopes + Instrumentation, by Heidi Hammel, executive vice president of AURA, Inc.
- The Kepler Exoplanet Survey: Instruments, Performance, and Results, 3 July plenary talk at SPIE Astronomical Telescopes + Instrumentation, by Thomas Gautier of the NASA Jet Propulsion Lab.
- Life in the Cosmos, 14 August panel discussion at SPIE Optics + Photonics, moderated by NASA's Richard Hoover