This isn’t really news to most folks who have paid any attention to astronomy or cosmology. It’s more of a confirmation of what most experts have suspected for a couple generations now, ever since the stellar lifecycle models were proposed and passed most reasonable observational tests.
WASHINGTON (AP) — The more astronomers look for other worlds, the more they find that it is a crowded and crazy cosmos. They think planets easily outnumber stars in our galaxy and they are even finding them in the strangest of places.
And they have only begun to count.
Three studies released Wednesday, in the journal Nature and at the American Astronomical Society’s conference in Austin, Texas, demonstrate an extrasolar real estate boom. One study shows that in our Milky Way, most stars have planets. And since there are a lot of stars in our galaxy — about 100 billion — that means a lot of planets.
It is nice to see this public acknowledgement that planets are common in the Milky Way (probably well over a trillion planets just orbiting stars. Who knows how many “rogue planets” are roaming around in interstellar space. By some estimates that number might even be bigger than the number of star orbiting planets.)
However, even through the filter of crappy science reporting, there’s still something that I’ve never seen addressed in any story about planets, and that’s the vastly increased likelihood of earth-like bodies capable of supporting life.
See, the thing is that the stellar lifecycle models don’t just predict that most stars probaby have a dozen or so planets (like our own system) but that a large fraction of those planets are gas giants. And that is what we are seeing when we find planets orbiting other stars. What did surprise cosmologists and astronomers when the first observational confirmation of planets orbiting other stars came in was how many of these gas giant planets are in close orbit to their stars. The assumption was that most stellar systems would resemble our own solar system, with rocky small planets close to the star and larger gas giants further out. That doesn’t seem to be the case though, at least so far. The majority of systems we see have large gas giant planets in orbits more like Mercury, Venus or Earth.
So of course the idiots who call themselves science reporters bemoan that those planets are not “earth-like” and therefore are not candidates for looking for “alien” life.
But nothing could be further from the truth.
See, the stellar lifecycle models don’t just predict that stars have planetary systems.
They also predict that gas giants have moon systems, and that those moons can be equal in size to what we think of as planets. So for every gas giant that is in close orbit to its sun, there is a fairly high probability that “hot Jupiter” has a collection of moons that could easily be the size of Mercury, Mars or even Earth.
Using our own solar system as a model, we have eight acknowledged “planets”. However those eight planets have over a hundred moons, and at least eight of those moons would qualify as planets if they were in orbit around the sun by themselves. So that means we should essentially not only DOUBLE the estimate of the number of possible life-supporting objects, we should actually QUADRUPLE that estimate since virtually all such “moons” are rocky bodies more resembling earth than gaseous bodies resembling Jupiter or Uranus.
So if half of the trillion or so “planets” now estimated to be in stellar orbits are gas giants, then there are likely TWO trillion planetary-sized objects with earth-like composition.
How many of those would be in the Goldilocks zone? Meaning how many would there be where water could exist in a liquid state on the surface? Well, that’s still a guess, but based on what I’ve seen from the data so far, probably five percent of the planets discovered so far would be in that zone, but the vast majority of them are “hot Jupiter” type objects.
By the way, that’s not necessarily because most planets in their star’s “goldilocks zone” are gas giants, that’s basically because our planet-detection process is still far more likely to find massive bodies in close orbit to stars than smaller bodies, or massive bodies in larger orbits.
Anyway, just throwing my own personal guess at things, I would guess that most stars have SOMETHING orbiting in their goldilocks zone. Some of those objects will be earth-like planets, some will be asteroid-like bodies and some will be gas giants with their own collection of moons. So my guess is that there’s likely to be a near one-to-one relationship between stars and rocky bodies capable of having liquid water on their surface.
Which puts the total number of such bodies into the hundreds of billions in our galaxy alone.
Now, if we plug that into the Drake Equation, that vastly increases the odds of there being alien life in our galaxy, which would therefore greatly increase the odds that there is intelligent life in the galaxy, which then greatly increases the odds that there are technologically advanced beings in our galaxy….
But then that takes us right to the Fermi paradox. “Where the hell are they then?”
By the way, using the standard of a potential life-supporting body being something large enough to have differentiated its composition and that composition being mainly of “rock”, our solar system has 27 such bodies currently known. Two of them orbit in the Goldilocks zone today. Mars and Venus are both right on the edge of that zone, and in the past and future both of them have been or will be in the Goldilocks zone. That means our solar system has four bodies that would merit close examination as potential life-bearing bodies if we were to be examined from some other vantage point outside our own solar system.
Four. I’m guessing that might be a pretty common number of potentially life-bearing planets for most stars. That means that roughly 15% of bodies of earth-like composition with reasonable surface gravity in our solar system are, have been or will be in the “Goldilocks zone” of our own star. That would mean if there are two trillion such objects in the galaxy, and our solar system can be used as a model, there should be roughly 300 BILLION Goldilocks zone inhabiting earth-like bodies in the galaxy.
My personal guess is that life is actually pretty common in the galaxy.