Not in Our Stars

Where Are All the Aliens?

Last year, there was considerable excitement among astronomy and space exploration enthusiasts, especially those who adhere to worldview commitments limited to time, chance, and chemical ingredients as the only sources for a tenable explanation of the origin and existence of life. The hubbub arose when NASA announced the discovery of a “potentially habitable ‘super-Earth’” that is a mere 137 light years distant from us. As is the custom in science reporting about such discoveries, the “potentially habitable” assertion breaks down as soon as one reads into the details about the discovery. The planet, TOI-715b, orbits an M-dwarf class star, meaning that it cannot be at all habitable, given the properties of that class of star.¹

Nevertheless, the discovery of TOI-715b was but one source of high excitement and extravagant expectations in astronomy and (possibly) astrobiology in recent months. Back in September 2023, NASA reported that the James Webb Space Telescope (JWST) had detected indications of biologically relevant molecules in the atmosphere of planet K2-18b, a sub-Neptune (smaller than Neptune) planet orbiting in the habitable zone of a cool dwarf star 120 light years distant from Earth.² The possible discovery of dimethyl sulfide (DMS) in the planet’s atmosphere, along with CO2 and methane, was thought to be cause for special excitement, as it is generally believed that this molecule only arises from biological processes. That would indeed be exciting news in the hunt for extraterrestrial life if it panned out, and, in fairness, the NASA press release was more sober than some reports in the press, stating:

The inference of DMS is less robust and requires further validation. “Upcoming Webb observations should be able to confirm if DMS is indeed present in the atmosphere of K2-18b at significant levels,” explained [Cambridge University Astronomer Nikku] Madhusudhan.

Madhusudhan’s caution later proved wise. A subsequent investigation of JWST’s observations has shown that the most advanced space telescope yet built by man most likely did not detect any DMS in the atmosphere of K2-18b.³ There’s another factor that speaks against the possibility of K2-18b’s harboring life of any kind: the type of star it orbits is not at all hospitable to life. It, too, is an M-dwarf star, a red dwarf, the most common type of star in the observable universe. The habitable zone of these relatively cool, low-luminosity stars lies so close to the host star that any planet orbiting one of them would be tidally locked, thus foreclosing any possibility that it could support life for long. This same set of conditions applies to TOI-715b and every other planet of any size and atmospheric composition orbiting a red dwarf star. So much for any of these planets being “in the habitable zone” of its parent star, however broadly that term is defined.

The Drake Equation

What this means is that, viewed soberly, the new discovery is merely another data point supporting physicist Bijan Nemati’s call for a revision of the Drake Equation in light of improvements in our state of knowledge regarding the search for life beyond Earth. The Drake Equation was proposed in 1961 as a formula for estimating the number of detectable alien civilizations in the Milky Way galaxy. To understand why the formula needs to be revised, let us recall that the general form of the equation is:

N = R* x fp x ne x fl x fi  x fc  x L

N= the number of extraterrestrial civilizations with which communication might be possible

R* = the average rate of star formation per year

fp= the fraction of those stars with planets

ne= the fraction of those planets that are habitable, i.e., capable of supporting life

fl= the fraction of habitable planets on which life develops

fi= the fraction of those planets with intelligent life capable of developing civilization

fc= the fraction of those civilizations that develop technology sufficient to send radio signals into space

L= the length of time over which the civilization transmits signals

The equation has multiple terms for which the value is based on pure speculation. With recent discoveries in astronomy, however, the state of knowledge has changed. A little.

In the 30 years since the discovery of the first exoplanet, 51 Pegasi b, the number of known worlds orbiting stars distant from our sun has grown to, as of December 2024, a total of 7,367. The total number of stars with planets orbiting them is 5,056, with 1,024 of those stars hosting multi-planet systems similar to our own solar system.⁴ This might be hard for those born after 1995 to believe, but this recent history of observational discovery of planets beyond our solar system was of momentous importance to those seeking validation of the then-utterly speculative idea that our solar system represented just “average planets around an average star”—nothing remarkable, cosmically speaking. There was, for a time, furor around discoveries of planets falling into the “gas giant” class, those planets equal to or larger in size and mass than Jupiter (many of them being so-called “hot Jupiters,” which orbit close-in to their parent stars), but it has long since died down, since this class of planets seems to be quite common in the observed population of exoplanets.

In fact, the two most common types of exoplanets catalogued by astronomers have turned out to be gas giants and Neptune-like worlds, with these two categories making up easily two thirds of the exoplanets discovered to date. Neither of these types of planets is what one might by any stretch of the imagination call hospitable to life, and that presents real difficulties for those still searching for Earth 2.0. Enrico Fermi’s famous question, “Where is everybody?”, first posed in 1950 based on speculations that Earth-like planets with technologically advanced civilizations would prove to be typical across the universe, now seems to be based on a false premise in light of our improved, enriched body of data. Earth appears to be a rarity, perhaps even unique among the planets thus far discovered.

More Confirmation of the Rare Earth Hypothesis

The good news for people concerned with data and facts is that we now have data indicating that the value for fp (the fraction of stars with planets) is perhaps as high as .5, while ne (the fraction of planets capable of supporting a biosphere of any kind), using the most optimistic estimate, is .000137. Using round numbers, that translates into exactly one out of approximately 7,300 known planets being capable of supporting life.

And you’re living on it. That may not seem like much of an improvement, but, compared to “we have not the slightest idea,” the new observations do provide some numbers more solid than sheer speculation—not the kind of numbers that people seeking out “strange new worlds, new life, and new civilizations” might want to see, but defensible numbers for at least two of the values.

The Star Trek reference is used here advisedly, in light of the long-lasting influence that that once-humble, rerun-driven franchise has had on the popular imagination. Of course, it’s not the only sci-fi game in town that accepts extraterrestrial life as a given, but it is one of the best-known ones fueling the speculations inherent in the press coverage of exoplanets. The drive to find habitable planets beyond our solar system is as much an indulgence of fancy as it is an exercise in intellectual curiosity. Yes, exoplanets exist. What was science fiction in the pages of magazines and novels only a few decades ago has been confirmed as fact. What the cold, hard data about these planets tell us, though, is that these staggeringly distant worlds are unlikely to be in any degree hospitable to life of any kind. And that staggering distance? It means any communication with any intelligent life would be extremely impractical, if not impossible.

For those searching for signs of life beyond our solar system, these numbers provide a massive improvement, but they yield less-than-optimistic results for those looking to the stars for signs that time, chance, and chemical ingredients inevitably yield life. Fed into the key components of the Drake Equation, the data indicate that Earth is certainly rare and just possibly unique as an oasis for life in a vast cosmic desert. This also makes the most-likely explanation for the infamous Fermi Paradox the simplest one: We hear nothing from biological life beyond Earth because there is nothing to hear.

Worldview Implications

Of the press coverage of these discoveries in the atmosphere of K2-18b, the clearest statement of popular thinking about possible implications of the discovery of life beyond Earth came in an account given in The Free Press:

Alexei Filippenko, a UC Berkeley astronomer, told me in an email: “If there is life on K2-18b, it would demonstrate that life on Earth is not unique—a very important discovery.” He added: “Perhaps it would change the religious outlooks of some people, but not others. It depends on whether one subscribes to the belief that God made Earth unique in terms of life.”⁵

Discovery of life beyond Earth might change religious outlooks, but why would it? God created life in staggering variety here. Why would he not create life in equally staggering variety elsewhere, if he so chose?

Theists, especially we of the Judeo-Christian variety, have better warrant for expecting to find extraterrestrial life than do adherents to philosophical materialism, whose best explanation amounts to “derp, derp, just happened—we won the cosmic lottery.” The search for knowledge is itself worthwhile, but on purely materialistic premises, faith that the search will be rewarded with a positive result is just scientifically baptized -superstition.

Notes
1. Hugh Ross, “More Evidence That Planets Orbiting M Dwarf Stars Are Uninhabitable,” Reasons to Believe (Nov. 20, 2023).
2. NASA Webb Telescope Team, “Webb Discovers Methane, Carbon Dioxide in Atmosphere of K2-18b,” NASA (Sep. 11, 2023).
3. “Webb Probably Didn’t Detect Biosignature Gas on K2-18b,” Sci News (May   2, 2024).
4. The Extrasolar Planets Encyclopaedia Catalogue of Exoplanets (accessed Dec. 11, 2024).
5. Peter Savodnik, “Astronomers May Have Found Life Beyond Earth,” The Free Press (Jun.   22, 2024).