Habitable Zones | The Institute for Creation Research

Habitable Zones

When speculating about life in the universe, scientists need to be more realistic than Hollywood. In Star Trek, no matter where the actors land, they can walk around and breathe the air. That may be easier on directors, but for a surface to be habitable, there are physical requirements.

Astrobiologists limit their searches to regions around stars where liquid water can exist. Because liquid water is bounded by its freezing and boiling points, a "Goldilocks" zone neither too hot nor too cold must be found at particular distances from a star. Extending the inner and outer radii in the orbital plane produces a ring-shaped region called the Continuously Habitable Zone, or CHZ. Under-surface oceans may exist on some planets or moons, but surface life must be in the zone.

A paper in Icarus last August added a complication to the CHZ concept. Earlier estimates overlooked the hazards of ultraviolet light. Highly-ionizing UV radiation rapidly destroys organic molecules. Many massive stars output prodigious amounts of UV. This cuts down on the number of candidate stars. Of twenty-one extrasolar planets studied, only five had an overlap between the UV-safe zone and the CHZ, where life could exist.

Smaller stars have a different problem: a much narrower CHZ. The zone is also closer in, meaning that any planet lucky enough to fit in the zone would become gravitationally locked to the star, with one hemisphere always facing the star, overheating, and the other hemisphere facing away, forever freezing. It is unlikely life could survive except along a very thin longitude near the terminator (the boundary between light and darkness). This means that life is highly improbable except around sun-like stars, a mere 5% of all stars.

Further complications arise when considering a star's host galaxy. Conditions too close to the center are exposed to hazardous radiation levels; too far out lack the heavy elements required for life. This means there is also a Galactic Habitable Zone (GHZ) to consider. Having a zone defined, of course, does not mean an earth-like planet will be present.

Astronomers continue to find extra-solar planets at an accelerating clip. Upcoming missions like the Terrestrial Planet Finder (TPF), Kepler, and Space Interferometry Mission (SIM) may one day succeed in finding an earthlike planet around another sun-like star. Spectral analysis may even be able to infer the possible presence of life from certain "biosignatures" such as gas ratios unexpected from geological or atmospheric processes alone. Given the vastness of space and the number of stars in the "cosmic lottery," astrobiologists are not discouraged at the prospects for life, even with few suitable zones.

What does this mean for Biblical creationists? The Bible does not specifically rule out some kind of life on other worlds. Many Christian thinkers have speculated about it. In the eighteenth century, in fact, the majority thought it foolish to deny it. Now that we have the means, searching for data to replace speculation is a good thing that Christians should welcome. A day of evidence is worth a millennium of conjecture.

*David F. Coppedge works in the Cassini program at the Jet Propulsion Laboratory.

Cite this article: Coppedge, D. 2007. Habitable Zones. Acts & Facts. 36 (4).

The Latest
CREATION PODCAST
Humanity's Demise at the Hands of Genetic Entropy | The Creation...
Welcome to the fourth episode in a series called “The Failures of Old Earth Creationism.” Many Christians attempt to fit old earth...

NEWS
''Inside-Out'' Fossil is Amazingly Preserved
It is widely known that vast numbers of fossils—vertebrate and invertebrate—have been discovered incredibly well-preserved.1,2...

NEWS
The Resurrection and the Origin of Life
At Easter time we focus on the cardinal Christian doctrine of the Resurrection. Without the Resurrection, Christianity is a sham. The truth that Jesus...

NEWS
Is an Ancient Extinct Tree-Dweller Our Relative?
Human evolution has always been hazy with seemingly as many attempted explanations for how we evolved from animals as there are paleoanthropologists. Evolutionists...

NEWS
The Return of the Dire Wolf?
There’s been much recent excitement about the birth of three dire wolf (Aenocyon dirus) puppies by a Dallas-based biotech company: Colossal Bioscience....

CREATION PODCAST
Cracks in the Layers: Lake Suigetsu and the Old Earth Illusion...
Welcome to the third episode in a series called “The Failures of Old Earth Creationism.” Many Christians attempt to fit old earth...

NEWS
Fish Fossil Vomit
A rather unsavory news story recently appeared regarding fossilized vomit. Although it’s hardly dinner table conversation, it nonetheless supports...

NEWS
Dino Footprints Down Under
Dinosaur trackways1 are once again making the news. Australia is the setting of a remarkable series of dinosaur tracks attributed to ornithischian...

NEWS
April 2025 ICR Wallpaper
"But the Helper, the Holy Spirit, whom the Father will send in My name, He will teach you all things, and bring to your remembrance all things...

NEWS
Human Evolution and the Inner Ear
The vain attempt by evolutionists to make an evolutionary connection between people and ape-like ancestors continues. This time, it is in regard to...