Among all the moons in the solar system, Earth’s is unique in that it is so massive compared to the planet. The ratio of the Moon’s mass compared to Earth’s is almost 50 times larger than the next closest ratio of moon mass to planet mass (that would be Saturn’s moon Titan).
Between 30-50 million years after the formation of the solar system, a collision between a Mars-sized object and Earth enriched the planet with additional radioactive elements and scattered a large disk of debris around it that coalesced to form the Moon. With the launch of NASA’s fourth and final Great Observatory, the Spitzer Space Telescope, scientists now have the capability to detect the remnants of similar collisions around other stars.
A recent Science Daily article highlights the results of one search in a 30 million-year-old nearby star cluster called NGC 2547. Among other important results, the search concludes that no more than 5-10 percent of all star systems could possibly contain a moon like Earth’s!
An Astrophysical Journal article details how the scientists analyzed data from the 400-500 stars in NGC 2547 by looking for the telltale dust signature from a collision between two planet-sized objects. If such a collision occurred around any of these stars, a large cloud of dust would cover the inner region of the star system. The radiation from the star heats the dust to a temperature where the dust emits infrared light that Spitzer can detect. Because the star would drive out any primordial dust by 30 million years, there are very few sources of dust other than a giant collision.
Of the 400-500 stars, only four showed any infrared signature. Two of those were so weak that a collision could not have been the cause. Thus, far less than 1 percent of the star systems contained a collision capable of producing a Moon-like object. Accounting for the duration of such a dust signature means that no more than 5-10 percent of Sun-like stars have an object like the Moon orbiting a planet.
In reality, the figure is probably much lower because the majority of collisions don’t produce moons. One exciting aspect of this research spotlights the capability astronomers now have to determine hard numbers regarding the rarity of an Earth-Moon type system. Just as Earth-like planets seem increasingly rare, RTB’s model predicts that future discoveries will continue to demonstrate the uniqueness of the Moon. Such rarity points to the activity of a supernatural Creator, who fashioned the Earth-Moon system with just-right conditions for advanced life.